JPH07320295A - Super-resolution optical head device - Google Patents

Abstract

PURPOSE:To obtain a super-resolution optical head device in which two dimensional scanning is realized by a condensing light beam system having equivalently apporoximately 70% of diffraction limit by employing a simple optical system. CONSTITUTION:A light beam emmited from a linearly polarized coherent light source 100 is made incident on a polarization phase plate 104, which generates a main beam having mutally orthogonal polarized components and an auxiliary beam having a bimodal shape whose central positions and main section sizes are matched with each other. The main and the auxiliary beams are condensed on an information storage surface 110a of an optical disk 110, are polarization- separated after reflection and are individually detected by first, second and third photodetectors 113a, 113b and 113c, respectively. The output signals from the photodetectors 113a, 113b and 113c are operated by a difference computer 117 and outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super-resolution optical head device for condensing a condensed beam on an information storage surface to optically read information, and more particularly to an optical head device for an optical disk, a bar code scanner or an image scanner. The present invention relates to a super-resolution optical head device applicable to.

[0002]

2. Description of the Related Art The above-mentioned super-resolution optical head device detects a coherent beam as a focused beam on a minute spot on an information storage surface and a light intensity of a reflected beam reflected from the information storage surface. And various photoelectric conversion means are provided, and various measures are taken to obtain a focused beam of a diffraction limit or a minute spot below the diffraction limit.

FIG. 16 is a schematic block diagram showing, as a re-diffraction optical system, a conventional imaging optical system using a well-known ring-shaped aperture as a super-resolution optical system. Such a ring-shaped aperture type super-resolution optical system is reported in the following documents as an example of application to an optical head device.

1) "High Density Optical Recording b
y Super resolution, ”Y.Yamada, Y.Hirose and K.Kubo
ta, Proc.Int.Symp.on Optical Memory, 1989.Jap.J.of A
ppl.Phys., Vol.28 (1989) supplement 28-3, pp.197-200. 2) “Optical Head with Annular Phase-Shifting Apo
tizer, ”Hideo Ando, Tsuneshi Yokota and Koki Tanou
e, Jap.J.Appl.Phys., Vol.32 (1993) pp.5269-5276, pt.1, N
O.11B. As shown in FIG. 16, the coherent beam emitted from the coherent light source 50 is collimated by a collimating lens (first Fourier transform lens) 51, and then the aperture (1 (Dimensionally, slit opening) 5
2a, 52b, and an image is formed by an objective lens (second Fourier transform lens) 53, and a super-solution like I (X) is shown as a power spectrum of the annular opening (transmittance) 52. An image spot is obtained.

Reference 1) describes an optical head in which such a super-resolution spot is formed one-dimensionally and only the main lobe is taken out by a slit knife edge and used. In addition, the above-mentioned document 2) uses a plurality of phase distributions and a predetermined amplitude distribution as an annular opening in order to realize a two-dimensional super-resolution spot, and the side outside the main lobe that occurs in FIG. A method for suppressing lobes is described. In the latter method, the design condition of the annular opening is optimized to suppress the side lobe.

[0006]

However, the method of suppressing the side lobes by the ring-shaped opening inevitably lowers the intensity of the focused beam. For example, when the peak value of the focused beam is reduced to about 50% to 15%,
When the full width at half maximum of the main lobe is narrowed to 85% of the diffraction limit, the intensity ratio of the side lobe becomes about 7% of the peak value of the main lobe.

As described above, when a slit-shaped or ring-shaped opening is provided on the plane corresponding to the opening surface of the objective lens, it is possible to obtain a super-resolution in which the side lobe is suppressed to some extent and exceeds the diffraction limit. On the other hand, since the amount of light reaching the image plane is significantly reduced, the problem that the amount of light in the main lobe is reduced, and with the provision of the side lobe blocking opening, precision is required for adjustment of the optical path. In addition to the problem that the reliability of the apparatus is lowered due to changes in the components that make up the optical system over time, the full width at half maximum of the beam is reduced to at most 10 to 20%.

In view of the above, the present invention has an extremely high performance capable of reducing the diffraction-limited beam width to about 70% to 50% by a simple optical system without causing a significant decrease in the amount of light. An object is to provide a super-resolution optical head device.

[0009]

In order to achieve the above object, the invention of claim 1 is a main beam and a beam which are incoherent to each other and whose main parts have the same size but have a peak of intensity at the beam center. By superimposing a sub-beam having an intensity peak on at least both sides of the center on the information storage surface and condensing, separating the light beam reflected from the information storage surface and differentially detecting the light intensity. It realizes a super-resolution optical system.

Specifically, a solution means taken by the invention of claim 1 is a super-resolution optical head device, which comprises a first coherent light source for emitting a first coherent light beam serving as a main beam, and a polarization of the first coherent light beam. A second coherent light source which emits a second coherent light beam having a polarization plane orthogonal to the plane or which has a wavelength different from the wavelength of the first coherent light beam, and an incident axis of the second coherent light beam on the optical axis A phase plate for emitting a sub-beam having a peak value on at least both sides of the beam center in a vertical plane and having a light intensity distribution in which the size of the main part of the beam is substantially equal to the size of the main part of the main beam; No. 1, a main beam emitted from the coherent light source and a sub-beam emitted from the phase plate, and condensing means for converging on the information storage surface; Drive means for driving the condensing means to focus and track an optical information storage carrier provided on the information storage surface, and a light reflected from the information storage surface. A beam splitting means which receives a beam incident and splits or splits the light beam into a main beam and a sub beam and outputs the light beam, and the light intensities of the main beam and the sub beam emitted from the light splitting device are separately detected. And a light detecting means for outputting a light intensity signal, and a calculating means for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detecting means. .

The invention of claim 2 realizes a super-resolution optical system by using a hologram element in place of the phase plate of claim 1.

[0012] Specifically, a solution means taken by the invention of claim 2 is that a super-resolution optical head device is provided with a first coherent light source for emitting coherent light as a main beam, and a polarization plane of the first coherent light orthogonal to the first coherent light source. A second coherent light source which emits a second coherent light beam having a polarization plane which changes or which has a wavelength different from the wavelength of the first coherent light beam, and a plane which receives the second coherent light beam and is perpendicular to the optical axis. A hologram element for emitting a sub-beam having a peak value on at least both sides of the beam center and having a light intensity distribution in which the size of the main part of the beam is substantially equal to the size of the main part of the main beam; and the first coherent A main beam emitted from the light source and a sub beam emitted from the hologram element are superimposed on each other to condense them on the information storage surface, and the main beam. Drive means for driving the condensing means so that a light beam formed by superimposing a beam and the sub beam on the optical information storage carrier provided on the information storage surface is focused and tracked; A light separating unit that receives the reflected light beam and outputs the main beam and a sub beam by polarization separation or wavelength separation, and light intensity of the main beam and the sub beam emitted from the light separation unit. And a calculation means for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detection means. To do.

According to the third aspect of the present invention, since the sub-beam having the intensity distribution with optical axis symmetry is obtained with a simple structure through the phase plate, the structure of the first aspect is characterized in that the phase plate is provided around the center of the phase plate. The relative phase difference is 0, 2π / N, (2π / N) with respect to the second coherent light emitted from the second coherent light source, which is divided into N pieces (N is an integer of 2 or more).
× 2, (2π / N) × 3, ..., and (2π / N) · (2
N-1) is sequentially provided, and the second coherent light passing through the N regions is emitted as the sub beam.

According to the invention of claim 4, since the sub-beam is obtained with a simple structure, in the structure of claim 1 or 2, the phase plate is close to or in close proximity to the second coherent light source. The configuration in which it is provided integrally with the light source is added.

According to the invention of claim 5, in order to obtain a main beam and a sub beam having polarization planes orthogonal to each other with a simple structure, in the structure of claim 1 or 2, the first and second coherent light sources are: A configuration is added in which the pair of linearly polarized lasers are arranged so that their respective polarization planes are orthogonal to each other.

Since the invention of claim 6 is a simple structure of the light separating means, in the structure of claim 1 or 2, the light separating means comprises a substrate having a refractive index uniaxial anisotropy and the substrate. A configuration is added, which is a polarization splitting means that is formed by the formed polarizing hologram element or the polarizing diffraction grating and splits the light beam into a main beam and a sub beam.

The seventh aspect of the present invention is a simple structure of the light splitting means. Therefore, in the configuration of the first or second aspect, the light splitting means comprises a multilayer film dielectric filter, and the light beam is a main beam and a sub beam. A configuration that is a wavelength separation means for wavelength separation is added to and.

According to an eighth aspect of the present invention, a coherent light beam emitted from a single coherent light source is processed by a polarizing phase plate to have a main beam having polarization planes orthogonal to each other and having a peak value at the beam center, and the center of the main beam. Is separated into a sub-beam having a peak value on at least both sides of the main beam, the main beam and the sub-beam are condensed on the information storage surface, and the light beam reflected from the information storage surface is polarized and separated to differentiate the light intensity. A super-resolution optical system is realized by detecting it selectively.

Specifically, the means for solving the problems according to the invention of claim 8 is a super-resolution optical head device, which mainly uses a coherent light source which emits coherent light and which receives the coherent light emitted from the coherent light source. A light intensity distribution having a beam and a plane of polarization orthogonal to the plane of polarization of the main beam, having peaks on at least both sides of the center of the main beam, and the size of the main part of the beam being substantially equal to the size of the main part of the main beam. A polarizing phase plate that separates and emits a sub-beam having a light beam, and a condensing unit that superimposes the main beam and the sub beam emitted from the polarizing phase plate on each other to condense on the information storage surface. The focusing means for focusing and tracking the light beam formed by superimposing the beam and the sub-beam on the optical information storage carrier provided on the information storage surface. A driving means for moving the light beam; a polarization separating means for receiving a light beam reflected from the information storage surface and separating the light beam into a main beam and a sub-beam; and emitting the light beam from the polarization separating means. Optical detection means for separately detecting the light intensities of the main beam and the sub-beam and outputting a light intensity signal, and an operation for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detection means And means.

According to the ninth aspect of the present invention, since the polarization splitting means is simply configured, the polarization splitting means is formed on the substrate having the refractive index uniaxial anisotropy and on the substrate. A configuration including a polarizing hologram element or a polarizing diffraction grating is added.

According to the tenth aspect of the invention, since the polarizing phase plate is obtained with a simple structure, the polarizing phase plate has a structure in which the coherent light emitted from the coherent light source is directed in one direction. The polarized light is separated into a light component having a polarization plane and a light component having a polarization plane in another direction orthogonal to the one direction, and a light component having a polarization plane in the one direction is emitted as the main beam, and It has a first region that does not give a relative phase difference to a light component having a polarization plane in another direction and a second region that gives a relative phase difference of π, and passes through the first and second regions. The configuration in which the light component to be emitted is emitted as the sub-beam is added.

According to an eleventh aspect of the present invention, in the structure of the tenth aspect, the first and second regions are alternately formed in two regions in four regions divided around the center of the polarizing phase plate. Is added.

According to the twelfth aspect of the present invention, a sub-beam having an intensity distribution symmetrical with respect to the optical axis is obtained through the polarizing phase plate with a simple structure. The coherent light emitted from the coherent light source is polarized and separated into a light component having a polarization plane in one direction and a light component having a polarization plane in the other direction orthogonal to the one direction, and a polarization plane in the one direction. A light component having a value of N is emitted without giving a relative phase difference, and N (N is 2
Relative phase difference 0, 2π / N, (2π) with respect to a light component having a polarization plane in the other direction.
/ N) × 2, (2π / N) × 3, ..., and (2π / N)
-A configuration is added in which there are N regions that sequentially give (N-1) and the light component that passes through the N regions is emitted as the sub-beam.

According to a thirteenth aspect of the present invention, a pair of pulse trains alternately generated from a single coherent light source is used, and one pulse train is a main beam having a peak at the beam center,
Phase modulation is applied to the other pulse train to form a sub-beam having a peak value on at least both sides of the center of the main beam. The main beam and the sub-beam are focused on the information storage surface and reflected from the information storage surface. The pulse trains of the main beam and the sub-beam are time-separated to detect their light intensities separately, and the light intensities corresponding to the main beam and the sub-beams to which a delay time has been selectively applied are detected differentially to achieve the super It realizes a resolution optical system.

Specifically, the means taken by the thirteenth aspect of the present invention is a super-resolution optical head device in which the first pulse train and the second pulse train of the first pulse train are generated alternately in time series. A coherent light source that emits coherent light having a pulse train; and a coherent light that receives the coherent light and selectively imparts a phase shift to the wavefront of the coherent light in synchronization with the first and second pulse trains. The main beam composed of the first pulse train and the second pulse train have peak values on at least both sides of the beam center in the plane perpendicular to the optical axis of the main beam, and the size of the beam main part is the main part of the main beam. The phase modulation means for emitting a sub-beam having a light intensity distribution substantially equal to the size of the part, and the main beam and the sub-beam emitted from the phase modulation means Focusing means for focusing on a storage surface, driving means for driving the focusing means so that the main beam and the sub-beam focus and track the optical information storage carrier provided on the information storage surface, Light detecting means for separately detecting the light intensities of the main beam and the sub-beam reflected from the information storage surface and outputting a light intensity signal, and the first light intensity signal output from the light detecting means. Delay means for selectively providing a delay time corresponding to a pulse train interval between the pulse train and the second pulse train, a light intensity signal output from the photodetector means, and a light intensity given the delay time by the delay means. And a computing means for computing and outputting a super-resolution scanning signal based on the signal.

According to a fourteenth aspect of the present invention, a coherent light beam emitted from a single coherent light source is processed by a polarizing phase plate into a main beam having polarization planes orthogonal to each other and having a peak value at the beam center, and the main beam of the main beam. The main beam and the sub-beam are separated into a sub-beam having a peak value on at least both sides of the center, the main beam and the sub-beam are condensed on the information storage surface in the outward optical system, and the main beam reflected from the information storage surface on the return path is hologram element. The super-resolution optical system is realized by diffracting the light beam by the light beam and by differentially detecting the light intensities by polarization-separating the main beam and the sub beam.

Specifically, a solution means taken by the invention of claim 14 is a super-resolution optical head device, a coherent light source for emitting coherent light, a coherent light emitted from the coherent light source, a main beam, and the main beam. A sub-beam having a plane of polarization orthogonal to the plane of polarization of, and having a peak at least at both sides of the center of the main beam and having a light intensity distribution in which the size of the main part of the beam is substantially equal to the size of the main part of the main beam. A polarizing phase plate that separates and emits
Condensing means for superimposing the main beam and the sub beam emitted from the polarizing phase plate on the information storage surface and a light beam formed by superposing the main beam and the sub beam are the information storage. Driving means for driving the condensing means so as to focus and track an optical information storage carrier provided on a surface, and a return light beam which is provided integrally with the condensing means and is reflected from the information storage surface. A hologram element that diffracts light to guide it on a plane substantially the same as the light emitting surface of the coherent light source, and receives a return light beam diffracted by the hologram element, and converts the return light beam into a main beam and a sub beam. The polarized beam splitting means for splitting and outputting the polarized light into the main beam and the sub beam emitted from the polarized beam splitting means are provided on the same plane as the light emitting surface of the coherent light source. Light detection means for separately detecting the light intensities of the above and outputting a light intensity signal, and a calculation means for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detection means. It is configured to be.

[0028]

With the structure of claim 1, the main beam is a normal Airy beam.
The beam has a disc-shaped pattern or a peak value of the light intensity at the center of the optical axis. A peak is formed, the main beam and the sub-beam are superposed on each other in incoherently on the information storage surface and condensed, and the light beam in which the main beam and the sub-beam are superposed on the information storage surface is reflected from the information storage surface. After that, the light intensity is independently detected as the main beam and the sub-beam by polarization separation or wavelength separation, and the light intensity is differentially calculated, so that the intensity distribution of the main beam and the sub-beam are equivalently obtained. Since the scanned output signal is obtained as the difference from the intensity distribution, the super-resolution optical signal can be obtained simply and reliably.

According to the structure of claim 2, the main beam is a normal beam.
The beam has an airy disc-shaped pattern or a beam with a peak value of light intensity at the center of the optical axis, and the main part of the sub-beam generated in the form of being reproduced from the hologram element has a beam size equal to the half-value width of the main beam on the information storage surface. And a peak of the light intensity is formed on at least both sides of the beam center of the sub beam, and the main beam and the sub beam are incoherently superposed and condensed on the information storage surface, and the main beam and the sub beam are stored as information. The light beams superposed on the surface are reflected from the information storage surface, and then are polarized or wavelength-separated to independently detect the light intensities as a main beam and a sub beam, and the light intensities are differentially calculated. This makes it possible to obtain an output signal that is equivalently calculated as the difference between the intensity distribution of the main beam and the intensity distribution of the sub-beam, so that a super-resolution optical signal can be obtained simply and reliably. You can

According to the structure of claim 3, a light beam in which a main beam and a sub-beam having an annular peak with the beam center as an axis and coaxial with the main beam are superimposed is condensed on an information storage surface, and information is recorded. Since the light beam reflected from the storage surface is polarized and separated into a main beam and a sub beam and the light intensity is detected independently, a super-resolution optical signal equivalent to that when a circular beam narrower than the diffraction limit is used is stably obtained. Can be realized.

According to the structure of claim 4, since the phase plate for emitting the sub-beam is provided integrally with the second coherent light source, a simple and compact super-resolution optical signal can be stably realized.

According to the structure of claim 5, the pair of linearly polarized lasers whose polarization planes are orthogonal to each other are incoherent to each other and can be easily polarized and separated.
The super resolution optical head device can be realized simply.

According to the structure of claim 6, in the polarizing hologram element or the polarizing diffractive element, most of the energy components of the polarized beam of one of the main beam and the sub-beam is the ± first-order diffracted light, and the other polarized beam is Since the 0th-order diffracted light is transmitted, the main beam and the sub-beam can be spatially reliably separated and the light intensity can be detected, so that the super-resolution optical signal can be reliably realized.

According to the structure of claim 7, since the multilayer film dielectric filter acts as a narrow band pass filter, the main beam and the sub beam having different wavelengths can be reliably wavelength-separated to detect the light intensity. A resolution optical signal can be reliably realized.

According to the structure of claim 8, a main beam and a sub beam whose polarization planes are orthogonal to each other can be obtained from the coherent light emitted from a single coherent light source, and the main portions of the main beam and the sub beam have the same size. , The main beam becomes a beam having a light intensity peak at the optical axis center, and the sub beam has a light intensity peak formed on at least both sides of the beam center, and the main beam and the sub beam are superposed incoherently with each other on the information storage surface. Are condensed, and the main beam and the sub-beam are reflected from the information storage surface as a light beam which is superposed on the information storage surface, and then are polarized and separated to independently detect the light intensity as the main beam and the sub-beam. The light intensity is differentially calculated, so that the output is equivalently scanned as the difference between the intensity distribution of the main beam and the intensity distribution of the sub beam. Since No. is obtained, we are possible to obtain a super-resolution optical signal simply and reliably.

With the structure of claim 9, the super-resolution optical signal can be surely realized as in the case of claim 6.

According to the structure of the tenth aspect, the polarizing phase plate emits the main beam having the polarization plane in one direction as it is, and for the beam having the polarization plane in the other direction orthogonal to the one direction. , 0, and π, the main beam and the sub-beams are emitted as a sub-beam having peaks on at least both sides of the beam center and having a beam main portion size equal to that of the main beam. Since the main beam and the sub beam reflected from the information storage surface are separated and polarized and the light intensities are independently detected, the output signal of each light intensity is differentially calculated. In addition, it is possible to obtain an extremely stable optical signal having super-resolution in at least one-dimensional direction.

According to the eleventh aspect of the invention, the light beam in which the main beam and the sub-beam having peaks in four directions of the beam center are superposed is condensed on the information storage surface, and the light beam reflected from the information storage surface is collected. Since the main beam and the sub beam are polarized and separated and the light intensities are detected independently, a super-resolution optical head device equivalent to the case of using a rectangular beam narrower than the diffraction limit can be stably realized.

According to the structure of the twelfth aspect, similarly to the structure of the third aspect, it is possible to stably realize a super-resolution optical head equivalent to the case where a circular beam narrower than the diffraction limit is used.

According to the thirteenth aspect, the main beam and the sub-beam are obtained as a pair of pulse trains emitted from a single coherent light source and temporally separated, and the sizes of the main parts of the main beam and the sub-beam are equal. , The main beam becomes a beam having a light intensity peak value at the optical axis center, and the sub beam has a light intensity peak formed on at least both sides of the beam center. The light beams are separated and superposed equivalently incoherently, collected, and reflected from the information storage surface as a light beam subjected to focusing and tracking control on the information storage surface, and then temporally separated into a main beam and a sub beam. The light intensity is detected independently, and the light intensity signal corresponding to the light intensity is selectively delayed and differentially calculated, Since to the main beam of the intensity distribution and the computation output signal as the difference between the intensity distribution of the sub-beams are obtained, it is possible to obtain a super-resolution optical signal simply and reliably.

According to the structure of claim 14, a main beam and a sub beam whose polarization planes are orthogonal to each other are obtained from the coherent light emitted from a single coherent light source, and the sizes of the main parts of the main beam and the sub beam are almost the same. Equally, the main beam becomes a beam with a peak of light intensity at the optical axis center,
The sub-beam becomes a beam having a peak of light intensity on at least both sides of the beam center, and in the outward path, the main beam and the sub-beam are incoherently superposed on each other and focused on the information storage surface. The light beam in which the main beam and the sub-beam are superposed on the information storage surface is reflected from the information storage surface, diffracted by the hologram element on the return path, and then polarized and separated by the polarization separation means. Light intensity is detected separately for the beam and the sub-beam.
Since the light intensities of the main beam and the sub-beams are differentially calculated, the output signal scanned as the difference between the intensity distribution of the main beam and the intensity distribution of the sub-beam is equivalently obtained. The image signal can be obtained simply and reliably.

[0042]

【Example】

(First Embodiment) FIG. 1 shows a schematic configuration of a super-resolution optical head device according to the first embodiment of the present invention.

As shown in the figure, the light beam emitted from the coherent light source 100 made of a semiconductor laser is a collimator lens 101, an opening 102 and a condenser lens 1.
After passing through 03, the polarizing phase plate 104 is illuminated. The light beam is separated by a polarizing phase plate 104 into a main beam and a sub beam whose polarization planes are orthogonal to each other, is reflected by a mirror 107 through a collimating lens 105 and an opening 106, and then is directed by a beam splitter 108. Then, the light is focused by the objective lens 109 on the information storage surface 110a of the optical disk 110 in which the information is stored in a pit form. The main beam and the sub beam reflected by the information storage surface 110a are collimated again by the objective lens 109 and then go straight through the beam splitter 108. After that, the main beam 130 is diffracted by the polarization hologram element 111, which will be described later, and then condensed by the condensing lens 112 to form the first photodetector 113a and the third photodetector 1.
13c, the sub-beam 131 is the same as the condenser lens 11
It is condensed by 2 and reaches the second photodetector 113b.
The first to third photodetectors 113a to 113b constitute an integrated photodetector 113, and the detailed structure of the integrated photodetector 113 will be described later.

The first and third photodetectors 113a, 113
After being combined, the electric signal output from c is amplified by the first amplifier 115, and the electric signal output from the second photodetector 113b is amplified by the second amplifier 116. The output signals output from the first amplifier 115 and the second amplifier 116 are calculated by the differential calculator 117.

In FIG. 1, 118 is an electromagnetic driving means (voice coil actuator), 119 is a computing means for computing a focusing error signal and a tracking error signal, and 120 is an electromagnetic driving by an output signal from the computing means 119. It is a drive unit for driving the means 118.

The feature of the first embodiment is that the main beam and the main portion have the same size, and a sub-beam that can easily and stably form a sub-beam whose peripheral portion except the central portion has substantially the same light intensity as the main beam. This is in the configuration of the shaping optical system unit 121.

The effects peculiar to the first embodiment are as follows. That is, since the main beam and the sub-beam are formed by the light beam emitted from the single coherent light source 100, the main beam and the sub-beam are separated by different semiconductor lasers,
Compared with the case where shaping is performed via an optical system, a stable scanning optical system in which the light intensity in the peripheral portion of the main lobe is equal between the main beam and the sub beam and there is no optical axis shift can be obtained.

The semiconductor laser which constitutes the coherent light source 100 is a light source which emits a linearly polarized transverse mode single beam which is obtained as a normal commercial product, and in the first embodiment, it is approximately 45 ° on the paper surface. The plane of polarization is set to the direction. By doing so, there is a component obtained by multiplying sin 45 ° in the direction parallel to the paper surface and the direction perpendicular to the paper surface. On the other hand, the crystal axis of the polarizing phase plate 104 (see FIG.
(See (e)) is set such that its Z-Y plane coincides with the paper surface, whereby a main beam (ordinary light) 130 and a sub-beam (abnormal light) 131 are formed. In the first embodiment, as the polarizing phase plate 104, one having a phase region described later with reference to FIGS. 9 and 10 can be used, and the first embodiment is generally a very stable two-dimensional super plate. A resolution optical head device is provided.

In the first embodiment, the aperture size of the aperture 102 is slightly narrowed to make the beam size on the polarizing phase plate 104 larger than 1.5 times the diffraction limit beam size of the objective lens 109. However, the effect of the first embodiment is not particularly changed. The reason is that, as is clear from the principle of the present invention, the main lobes of the main beam and the sub-beam have the same profile except for the central portion and are canceled by the differential detection.

2 (a) and 2 (b) are schematic illustrations of how the light intensity distributions of the main beam 130 and the sub-beam 131 on the information storage surface in the first embodiment are shown. is there. In FIG. 2A, in order to easily understand the super-resolution principle of the present invention with a one-dimensional model, the X _s axis is set on the polarizing phase plate 104, and the main beam 130 is taken.
Also enters the X _s axis and has the same beam waist diameter W ₁ as the sub-beam 131. Figure 1
2A corresponds to the first convex lens 150 in FIG. 2A, and the objective lens 109 in FIG.
2A corresponds to the second convex lens 151, and the opening 106 in FIG. 1 corresponds to the opening 152 in FIG. 2A. However, the diameter W ₁ of the light beam having the wavelength λ is the diffraction-limited beam diameter W _R (W _R is λ / (N ·
A) = λ / sin α ₁ ), which is approximately 1.5 times larger than

Further, the first and second convex lenses 150, 1
Reference numeral 51 is a Fourier transform lens, and f ₁ · sin α
₁ = f ₂ · sin α ₂ = D / 2 (1) is satisfied. At this time, on the image plane X ₀ axis, the size of the main part of the intensity distribution 160 of the main beam 130 and the size of the main part of the intensity distribution 161 of the sub-beam 131 are equal to each other, and W ₂ (W ₂ is (f ₂ / f ₁ ) · W ₁ ).

The polarizing phase plate 104 is a substrate having a phase boundary of a step d ₁ which produces a phase difference π on the optical axis for a specific polarization component, and having a refractive index n for light of wavelength λ.
It is assumed that the relationship of (n-1) · d = λ / 2 is satisfied. Therefore, on the X ₀ axis, the above-mentioned intensity distribution 161 of the sub-beam 131 is obtained as a result of the superposition of the two wavefronts 162 and 163 having the amplitude distributions of opposite phases. As shown in FIG. 2B, the difference I _d (x ₀ ) between the intensity distribution 161 of the sub beam 131 and the intensity distribution 160 of the main beam 130 is only the portion where the sub beam 131 is dropped near the optical axis. Remains, and full width half maximum g
The size of ₀ is about 70% with respect to the full width at half maximum g _R of the diffraction limit.

The above-mentioned super-resolution principle is actually the first to third photodetectors 113a, 113b, 113c for detecting the light intensity of the main beam 130 and the sub-beam 131 shown in FIG.
Integrated detector 113 and signal arithmetic processing unit 114
What is realized by is as described above.

FIG. 3 is an optical system similar to that of FIG. 2, but schematically shows a modified example which can be handled analytically and is easy to understand. The difference from the optical system shown in FIG. 2 is that the sub-beam 131 is given by two points 170, 171 separated by a distance δ = (λf ₁ ) / D, and two points 170 on the X ₀ axis 170, The diffraction image corresponding to 171 is a diffraction-limited amplitude distribution 173 through the rectangular opening 152.
174, which are out of phase with each other by π. The center of the amplitude distributions 173 and 174 is δ ₁ = δ × (f ₂ / f ₁ ).
Since δ and δ ₁ are set so that the amplitude of the other party becomes 0 at the peak positions of the respective amplitudes, the intensity distribution 175 as shown in FIG. 3 is obtained. Analyzing this, the complex amplitude distribution u ₁ of the bimodal beam obtained as the sub beam 131 on the X ₀ axis
(X ₀ ) is

[Equation 1] And the intensity distribution I (X ₀ ) is I (X ₀ ) = | u
₁ (X ₀ ) | ² (3)

In equation (2), sincX = (sin
X) / X ... (4), and δ ₁ = δ × (f ₂ / f ₁ ) =
(F ₂ · λ) / D = (1/2) · (λ / sin α ₂ ) ...
(5) corresponds to the resolution of an optical head having a numerical aperture sin α ₂ and corresponds to Rayleigh's criterion (usually the minimum distance that can resolve two close points). The extension to two dimensions will be described later, but in that case, the Bessel function of the first kind J ₁ (r) is used instead of the sinc function to represent the amplitude and intensity distribution of the point image. The amplitude distribution of the point image (Airy pattern) imaged through the circular aperture on the optical axis is
Using the distance r from the center of the optical axis, u (r) = (2π (D
/ 2) ² · J ₁ (R)) / R ... (6) However, it is given by R = (π · D · r) / (λ · f ₂ ).

The size of the main lobe called Airy disc is A = 2 × 1.22 × (λ · f ₂ ) / D (7), and the size of the main lobe B = 2 × in the case of a rectangular opening. (Λ
・ It is only 1.22 times larger than f ₂ ) / D (8).

According to a computer simulation, the depression at the center of the bimodal beam formed by condensing the sub beam 131 on the information storage surface as described above is diffracted by the second convex lens 151 (objective lens 109 in FIG. 1). This is about 70% of the limit beam diameter. Match the dimensions of the main part of the main beam 130 with the dimensions of the main part of the sub-beam 131,
By detecting the main beam 130 and the sub-beam 131 separately and calculating them by the differential calculator 117, the output signal from the differential calculator 117 is equivalently equivalent to the diffraction limit of about 7
This corresponds to a signal scanned by a beam size of 0%. The sizes of the main beam 130 and the sub beam 131 can be adjusted by the opening 102 in FIG.

Polarizing phase plate 104 (or normal phase plate)
As shown in FIG. 9A, the phase region configuration of the first region 10 has a first region 10 having a reference thickness and d is more than the first region 10.
_{And a} second region 11 differing in thickness by _one . It has already been described that, in this case, a bimodal light intensity distribution is obtained in the X _s direction of FIG. 9A on the light collecting surface. Therefore, a one-dimensional super-resolution effect is realized in the X _s direction. When the main beam and the sub beam are formed by the independent optical system described later based on FIG. 5, the effect is the same even with the non-polarizing phase plate.

FIG. 9B shows another configuration example of the polarizing phase plate 104 (or a normal phase plate). In this example, the polarizing phase plate 104 is divided into four regions 12, 13, 1
As shown in FIG. 9C, the two-dimensional depression 16 having weak light intensity is realized in the central portion of the sub-beam 131.

FIG. 10A shows another more preferable example of the configuration of the phase region of the polarizing phase plate 104 (or a normal phase plate), which is 0, π / 2, π around the optical axis. , (3 /
2) Four regions 20, 21, 22, and 23 are formed in the order of π, and the phase difference between every other adjacent regions is π. By doing so, the central portion 24 of the image plane, which is schematically shown in FIG. 10B, has an intensity distribution with deeper depressions than in the case of FIG. 9B.

FIG. 10C also shows another structural example of the phase region of the polarizing phase plate 104 (or a normal phase plate), which is further expanded from the above idea by dividing it into eight equal parts in the circumferential direction. Eight areas 30, 31, 32, 33, 34, 35, 3
6 and 37, a phase difference is provided in the order of 2π / 8 from 0, and the phase difference between two regions facing each other (that is, the opposite pole forming an angle of 180 °) is π. By thus dividing the circumference into N and configuring the phase regions of the polarizing phase plate 104 so as to generate a phase difference of 2π / N each, an optical axis symmetric sub-beam 131 that is as close to ideal as possible is formed. It becomes possible to do. In practical terms,
With N = 8, the information storage surface (X ₀ , Y shown in FIG.
The central portion 38 of the sub-beam 131 in ( ₀ ) realizes a distribution substantially symmetrical with respect to the optical axis.

FIGS. 11A to 11D show the polarizing phase plate 10.
4 shows an example of the manufacturing process of No. 4.

First, as shown in FIG. 11A, the thickness 5
A Ta film 181 having a thickness of 230 angstroms is formed on the surface of a substrate 180 (X plate) made of a crystal of lithium niobate (LiNbO ₃ ) of 00 μm and having a uniaxially anisotropic refractive index by a sputtering method.

Next, as shown in FIG. 11B, the Ta film 181 is formed by photolithography and dry etching.
Is patterned to form a semi-planar proton exchange mask 182.

Next, as shown in FIG. 11 (c), heat treatment with pyrophosphoric acid (H ₄ P ₂ O ₇ ) at a temperature of 260 ° C. is carried out using the proton exchange mask 182 as a mask to exchange protons with a depth of 2.38 μm. A region 183 is formed.

Next, by etching with hydrofluoric acid (HF), as shown in FIG.
When a phase compensation groove (depth d ₂ ) is formed in 83, FIG.
The polarizing phase plate 104 as shown in (e) is obtained. T
The a film 181 is rapidly removed by hydrofluoric acid, and then the proton exchange region 183 is selectively etched.

In this way, the polarizing phase plate 104
Is a polarization component having a plane of polarization in the Y direction (called ordinary light)
On the other hand, it becomes a phase plate having a phase step, and becomes a transparent substrate which is uniform with respect to a polarization component (called extraordinary light) having a polarization plane in the Z direction. The method of forming the phase compensation groove will be described in detail later.

The condition that a transparent substrate that gives a phase difference π to ordinary light and is uniform to extraordinary light is that the thickness d ₃ of the proton exchange region 183 and the depth d ₂ of the phase compensation groove are (2π _{/ λ) × {Δn o ×} d 3 + (1-n o) × d 2} = - π ... (9) (2π / λ) × {Δn e × d 3 + (1-n e) × d 2 } = 0 (10) is satisfied. Where λ is the wavelength of the incident light, n _o and n _e are the ordinary and extraordinary light refractive indices with respect to the substrate (non-proton exchange region) 180, Δn _o is the decrease in the refractive index due to proton exchange with the ordinary light, and Δn _e
Is the increase in refractive index due to proton exchange with respect to extraordinary light.

[Table 1] shows data examples of the refractive index of the substrate 180 made of lithium niobate and the refractive index change due to proton conversion.

[0070]

[Table 1]

Although FIG. 11 shows the polarizing phase plate 104 in which (0, π) is formed as only one-dimensional two regions, the regions shown in FIGS. 9 and 10 are formed by the same process. It is also possible to realize the two-dimensional super-resolution scanning optical system by manufacturing the polarizing phase plate 104 having the same. In this case, the right side of the equation (9) is set to -φ in the region where another phase difference φ different from π is given to the ordinary light.

FIG. 7A shows a schematic structure of a polarization hologram element 111 produced by the same process as the polarization phase plate 104 using the lithium niobate substrate described in FIG. 11, and FIG. ) Is b- in FIG.
The sectional structure of line b is shown. FIG. 7A shows an off-axis Fresnel zone plate (off-axisFr) for focus detection.
A proton exchange region 111a and a non-proton exchange region 111b as patterns of an esnel zone plate, and diffraction grating patterns 111c and 111d for detecting a push-pull signal for detecting a tracking error signal are shown.

The polarizing hologram element 111 is composed of a proton exchange region 111a and a non-proton exchange region 111b, and the depth d ₂ of the phase compensation groove and the thickness d ₃ of the proton exchange layer are the same as the above (9), (10). ) Is satisfied.

FIG. 8 shows the structure of the integrated photodetector 113 described above. Polarizable hologram element 1 shown in FIG.
Diffracted by 11 Fresnel zone plate regions +
Beams 32a and 3 of first-order and -1st-order diffracted light (ordinary light)
2b is a pair of three-division photodetectors 113a ₁ and 113a
₂ , 113a ₃ (first photodetector 113a in FIG. 1
And 113c ₁ , 113c ₂ , 113c ₃
Each of them is incident on the corresponding spot size detection (SS corresponding to the third photodetector 113c in FIG. 1).
The focus error signal of the D method) is given. In addition, the 0th-order diffracted light (extraordinary light) 3 transmitted through the polarization hologram element 111
3 enters the second photodetector 113b. The tracking error signal is realized by differential detection of the light intensities of the beams 32c and 32d incident on the photodetectors 113c ₄ and 113c ₅ , respectively.

The hologram element (holographi) as described above
A technique for detecting a servo signal using a c optical element) is disclosed in JP-A-50-78341 and JP-A-6-74341.
2-251025, JP-A-62-251026, JP-A-63-229640 and USP 4,929,823.
Is disclosed in. An optical head using a polarizing hologram element is disclosed in USP 5,062,098.

The fact that the information stored in the information storage surface 110a (see FIG. 1) of the optical disk 111 can be super-resolution read by the first embodiment has already been performed based on FIGS. The explanation is clear. In summary, each signal (S _a1 -S _a3 and S a) at which the main beam is detected is
_{c1 to} S _c5 ) and the signal S _b from which the sub-beam is detected are differentially arithmetically processed, and equivalent to scanning with a beam size of about 70% of the diffraction limit of the objective lens 109 as an RF signal. Super-resolution reading can be realized.

The first modification of the first embodiment will be described below.

In the first embodiment, the main beam (ordinary light)
Although the focus error signal and the tracking error signal are obtained by using, it is possible to conversely give the servo signal by diffracting the sub beam (abnormal light) by the hologram element. In this case, it is only necessary to form the hologram element while rotating only the direction of the crystal axis of the substrate of the hologram element by 90 ° without changing the orientation of the hologram pattern shown in FIG. In this case, the sub-beam has a light intensity near the optical axis close to 0 and a high light intensity near the lens outer periphery, so that a tracking error signal with a large modulation degree corresponding to the push-pull signal can be obtained.

The second modification of the first embodiment will be described below.

As a second modification of the first embodiment, a third structure for obtaining a tracking signal is possible. That is,
All the hologram element surfaces are configured by Fresnel zone plates 111a and 111b without providing the diffraction grating patterns 111c and 111d shown in FIG. In this case, the second photodetector 11 for detecting the sub beam shown in FIG.
3b is composed of two photodetectors (not shown in FIG. 8) divided into two in the Y direction of the center of FIG. 8, and a tracking signal is obtained by using a differential output from the two photodetectors. It is also possible to obtain

By doing so, the tracking error signal can be obtained without being affected by the focusing error signal by the main beam, and stable tracking servo can be performed. Stable detection of the tracking error signal becomes more difficult as the track-to-track distance becomes narrower. However, in the second modification, the characteristics of the bimodal or four-modal beam pattern are used for tracking control by the sub beam. As a result, stable reading of an optical disc with a narrowed track becomes possible.

(Second Embodiment) FIG. 4 shows a schematic configuration of a super-resolution optical head device according to a second embodiment of the present invention.

As shown in the figure, the light beam emitted from the coherent light source 200 composed of a semiconductor laser reaches the collimator lens 201 and the hologram element 202,
The hologram element 202 separates a main beam and a sub beam whose polarization planes are orthogonal to each other, and then the beam splitter 204 changes the direction, and then the objective lens 2
Optical disc 21 in which pit-like information is stored by 05
It is condensed on the third information storage surface 213a. The information storage surface 2
The main beam and the sub beam reflected by 13a are again collimated by the objective lens 205 and then pass through the beam splitter 204. After that, the main beam is diffracted by the polarizing hologram element 206, and then the condenser lens 2
07 collects the first photodetector 208a and the third photodetector 208a.
To the second photodetector 208b.

First and third photodetectors 208a, 208
The electric signal output from c is combined and then amplified by the first amplifier 209, and the electric signal output from the second photodetector 208b is amplified by the second amplifier 210. The output signals output from the first amplifier 209 and the second amplifier 210 are calculated by the differential calculator 211.

In FIG. 4, reference numeral 212 is an electromagnetic drive unit (voice coil actuator), 214 is a control unit having an arithmetic processing unit 215 and a drive unit for driving the electromagnetic drive unit 212, and 216 is a main beam and a sub beam. A beam shaping optical system unit that forms a beam with ease and stability.

The hologram element 202 is shown in FIGS.
After illuminating any one of the polarization phase plate 104 (or a normal phase plate) described above with a coherent light of a predetermined size and collimating the transmitted light, the coherent light and the coherent light can be interfered with each other. It is a hologram element obtained by superimposing it on some other reference light. In the process of manufacturing the hologram element 202, the effect does not change even if the non-polarizing phase plate 104 is used.

The hologram element 202 will be described below with reference to FIG.

The polarizing phase plate 104 and the two points 170,
171 (actually, a slit having a minute aperture) has a wavelength λ
Of parallel reference light 176 on the focal plane (ξ axis) of the Fourier transform lens (convex lens) 150.
To record interference fringes on the photosensitive material. The holographic technology for producing such a diffracted wavefront from an arbitrary object by superimposing it on an independent reference beam is well known, and further detailed description will be unnecessary. Here, the hologram is recorded using the wavelength λ, the incident angle θ of the reference light, and the lens focal length f ₁ , but other wavelengths λ ₀ and the lens focal length f ₀ may be used. The incident angle θ ₀ of the reference light at this time is sin θ
₀ / sin θ = λ ₀ / λ, and the focal length of the collimator lens 201 shown in FIG. 4 is f ₁ = f ₀ · λ
_It may be ₀ / λ. Besides this, it is possible to set the parameters of the hologram recording / reproducing optical system so as to equivalently obtain the same effect.

In this way, the main beam and the sub beam shown in FIG. 4 are formed on the same axis by using the hologram element 202 equivalent to the polarizing phase plate 104, which also serves as the beam splitter. Polarizing phase plate 1
Of course, it is also possible to design and manufacture the 04 hologram by a method based on computer synthesis. A special advantage in this case is that the N-divided polarization phase plate 104 described with reference to FIG. 10 can be calculated from a model idealized as N → ∞ on a computer. Based on the calculation result, it is possible to obtain a relief hologram that can be generated as a mask pattern that can be used for lithography or that can be duplicated by means such as electron beam drawing or laser beam drawing.

The polarization hologram element 206 in the second embodiment has the same structure as the polarization hologram 111 in the first embodiment.

Regarding the same type of polarizing hologram element,
For example, application examples are disclosed in USP 5,062,098 and the like, and polarization anisotropy possessed by other substrate materials such as liquid crystal devices can also be used.

However, the method used to manufacture the polarizing hologram elements 111 and 206 according to the first and second embodiments is further excellent in manufacturing accuracy and cost, as will be described below. That is, in the device in which lithium niobate was proton-exchanged, as shown in [Table 1] above, a large change in the refractive index of the extraordinary light (Δ
n _e ) is generated, and acts as a phase type diffraction grating having a large diffraction effect on extraordinary light.

However, in the proton-exchanged region, a slight difference in refractive index (Δn _o ) occurs even with ordinary light. In this way, the diffraction grating with lithium niobate exchanged with protons causes the refractive index change of extraordinary light and the change of the refractive index of ordinary light at the same time, and the polarization separation function cannot be fully realized. There is. Conventional method (A.Ohba et al., Jap.J.Appl.Phys., 28 (1989) 359)
In the above, a dielectric film was formed in the proton exchange region to compensate for the phase difference of ordinary light. Therefore, in order to manufacture the diffraction grating, a dielectric deposition process and a patterning process are required, and a problem of alignment accuracy remains.

A polarizing hologram element (polarization separating element) 111 schematically shown in FIG. 7E is a substrate (X plate).
Proton exchange regions 111a are formed in a lattice pattern on the surface of, and are formed in a polarization anisotropic hologram element.
As a method of phase compensation, contrary to the conventional method, only the proton exchange region 111a is etched (hereinafter referred to as a phase compensation groove), and the proton exchange region 111 after etching is etched.
a non-proton exchange region 111 for extraordinary light passing through a
The phase difference with b is canceled out. That is, the phase compensating grooves is the refractive index 1 (= the refractive index of air) smaller than the substrate (ordinary light: 1-n _o, the extraordinary light: 1-n _e). Therefore, the increase (Δn _e ) due to the proton exchange of the extraordinary light is canceled out,
When the phase difference is eliminated, the amount of decrease in the refractive index due to proton exchange (Δn _o ) is added to the amount of decrease due to the phase compensation groove for ordinary light, and the phase difference is increased conversely. The conditions for diffracting ordinary light with maximum efficiency and not diffracting extraordinary light are (9),
It is given by the equation (10).

Hereinafter, a method of manufacturing the polarizing hologram element 111 will be described again.

Like the polarizing phase plate 104 shown in FIG. 11, the polarizing hologram element 111 can be easily manufactured by using the processes of photolithography and proton exchange. That is, after forming a Ta film on a substrate made of a crystal of lithium niobate (LiNbO ₃ ) which is a uniaxial anisotropic material, patterning is performed on the Ta film by photolithography and dry etching to form lattice-like protons. Form a replacement mask. Next, using a proton exchange mask as a mask, heat treatment is performed with pyrophosphoric acid at a temperature of 260 ° C. to form a proton exchange region having a depth of 2.38 μm as shown in FIG. 11C. Here, hydrofluoric acid etching has a selectivity that does not etch the substrate while etching the proton exchange region. By utilizing this selectivity, proton exchange can be performed without alignment. It becomes possible to form a phase compensation groove composed of the region 111a (see FIG. 7). As the depth of the phase compensation groove increases, the phase difference in ordinary light increases, the efficiency η _o1 of ordinary diffracted light of ordinary light increases, and the transmittance η _o0 (efficiency of diffracted light of zero order) decreases. On the other hand, in extraordinary light, the increase in the refractive index of the proton exchange region 111a is offset by the phase compensation groove, the diffraction efficiency η _e1 of the first-order diffracted light decreases, and the transmittance increases. The transmittance η _e0 of extraordinary light becomes minimum when the etching depth is 0.13 μm. At this time, the extinction ratio is that the transmitted light (abnormal light) is 24d.
B, the diffracted light (ordinary light) is 17 dB, and good characteristics are obtained.

In this way, the polarization hologram element 206
The main beam and the sub-beam are respectively detected by the first photodetector 208a and the third photodetector 208c and the second photodetector 208b shown in FIG. 4 with a good extinction ratio. Similar to the first embodiment, the first photodetector 20
8a and the third photodetector 208c are electrically connected,
The electrical signals are added. First to third photodetectors 208a
Output signals from 208 c are transmitted to a control unit 214 including an arithmetic processing unit and an actuator driving unit, and the electromagnetic driving unit 212 is controlled.

(Third Embodiment) FIG. 5 shows a schematic configuration of a super-resolution optical head device according to a third embodiment of the present invention.

The third embodiment differs from the first and second embodiments in that the first coherent light source 301 and the second coherent light source 301 and the second coherent light source which emit coherent light having slightly different wavelengths are used as the light sources.
The coherent light source 302 of is used. With this,
A multilayer interference filter 309, which is a wavelength separation optical system, is used as a means for separating the main beam and the sub beam.

As shown in FIG. 5, the main beam of the first coherent light of the wavelength λ ₁ emitted from the first coherent light source 300 has a first collimating lens having an opening (not shown). Incident on the objective lens 305 via 302 and the first beam splitter 303,
The light is focused on the information storage surface 306a of the optical disc 306.
On the other hand, from the second coherent light source 301 a phase plate are integrated together, made of the second coherent light only different wavelength λ ₂ = λ ₁ + Δλ Δλ is the wavelength lambda ₁ of the first coherent light sub The beam is emitted. The secondary beam is
The collimated light is collimated by the second collimator lens 304, reflected by the second beam splitter 307, transmitted through the first beam splitter 303, and transmitted through the first beam splitter 303 to the information storage surface 306 of the optical disc 306 by the objective lens 305.
It is focused on a. The main beam and the sub beam are superposed on the information storage surface 306a of the optical disc 306, reflected by the information storage surface 306a, and then diffracted by the hologram element 308 for detecting a focusing error signal and a tracking error signal. After that, the light enters the multilayer interference filter 309 for wavelength separation. Then, according to the band pass characteristic of the multilayer interference filter 309, the main beam is reflected by the multilayer interference filter 309 and passes through the condenser lens 310 to the first photodetector 3.
11 and the sub-beam is a multilayer interference filter 309.
And a second photodetector 313 that passes through the condenser lens 312.
Incident on. The electric signal output from the first photodetector 311 is amplified by the first amplifier 314, and the electric signal output from the second photodetector 313 is amplified by the second amplifier 31.
Amplified by 5. The output signal from the first amplifier 314 and the output signal from the second amplifier 315 are calculated by the differential calculator 316 and output from the differential calculator 316 as a super-resolution scanning signal. In addition, the electromagnetic drive means 3
Although the mechanism for outputting the control signal to 16 is not shown, it is the same as in the first and second embodiments.

As the second coherent light source 301,
As shown in FIG. 12, the phase plate 32 is placed close to the active layer output end 320a which is the beam emitting end face of the semiconductor laser 320.
1 (having four phase regions 321a to 321d) can be integrated, or as shown in FIG. 13, a semiconductor laser 320 can be used in which a phase plate 322 is closely attached and integrated.

As a modification of the third embodiment, the optical system may be constructed by the principle of polarization separation instead of wavelength separation.
That is, as the first coherent light source 300 and the second coherent light source 301, those having polarization planes orthogonal to each other are used, a polarization beam splitter is used instead of the multilayer film interference filter 309, and the hologram element 308 is used as the first embodiment. Alternatively, the polarization hologram elements 111 and 206 similar to those in the second embodiment can be used.

(Fourth Embodiment) FIG. 6 shows the schematic arrangement of a super-resolution optical head device according to the fourth embodiment of the present invention.

The fourth embodiment uses a time separation method as a signal detection method for the main beam and the sub beam.

As shown in FIG. 6, the coherent light source 40
The linearly polarized pulsed beam light emitted from 0 and subjected to pulse modulation is beam-shaped by the condensing lens 401 and then incident on the phase modulator 402, and thereafter, the collimator lens 403, the opening 404, and the polarization beam splitter. Four
The information storage surface 408a of the optical disc 408 is passed through the objective lens 407 after passing through the 05 and quarter wave plate 406.
Is focused on. The pulsed beam reflected by the information storage surface 108a again enters the photodetector 411 through the quarter-wave plate 406, the polarizing beam splitter 405, the hologram element 409, and the condenser lens 410. The first control unit 412 drives the coherent light source 400 and the phase modulator 402 in synchronization with each other, and the main beam and the sub beam alternate between the information storage surface 408 of the optical disc 408.
It is controlled so that it reaches a and is reflected.

The main beam of the pulsed beam incident on the photodetector 411 is passed through the first amplifier 413 to the differential calculator 4
The sub-beam of the pulsed beam that is input to the differential beam calculator 14 is passed through the second amplifier 415 and the delay element 416 to the differential calculator 41
4 is input. Then, the super-resolution signal is output from the differential calculator 415 through the output terminal 417. The delay element 416 adjusts the pulse interval t between the main beam and the sub beam.

The focusing error signal and the tracking error signal diffracted by the hologram element 409 are received by the photodetector 411 and then sent to the second controller 418 as a servo signal, as in the first embodiment.
The second controller 418 drives the electromagnetic drive unit 419 based on the servo signal.

In the phase modulator 402, as shown in FIG. 14, a ferroelectric crystal 420 made of lithium niobate crystal or PLZT is used as an upper electrode 421 from the vertical direction in the Z-axis direction.
A and the lower electrode 421B sandwich the upper electrode 4
21A and the lower electrode 421B are connected to a voltage application power supply incorporated in the first control unit 412. However, the voltage is such that as shown in FIG. 14, a beam 431 having an optical path difference of Δn _e × l with respect to a half of the linearly polarized beam 430 incident on the phase modulator 402 is generated. Apply.

[0109] In _{Δn e = (1/2) × N} 3 × Eγ 33 ... (11) Δn e × l = λ 2/2 ... (12) electro-optic constant gamma ₃₃ is approximately 30 × 10 ^-12 m / v Yes,
λ ₂ is approximately 0.4 × 10 ^-6 m, L = 10 ^-2 m, N
Is about 2 (refractive index), the required electric field E is about 2 ×
10 ⁵ v / m = 200 v / mm.

FIG. 15A shows a ferroelectric crystal 422 made of lithium tantalate (ferroelectric crystal 4 shown in FIG. 14).
(Corresponding to the upper half of 20) shows a schematic configuration of the phase modulator 402 having a domain-inverted structure formed by applying a high electric field of about 20 kv through the upper electrode 421A and the lower electrode 421B. By applying the voltage, the phase modulator 40
± Δn × for linearly polarized beam 432 incident on 2
A phase difference of 1 is generated in the beam 433, and by applying a voltage that is 1/2 of that of the phase modulator 402 shown in FIG.
An optical path difference equivalent to that of the phase modulator 402 shown in FIG. 4 can be generated. At this time, in order to realize the two-dimensional phase region formation as shown in FIG. 9B or FIG. 10A, the phase modulator 402 as shown in FIG. 14 or FIG. Rotate 90 ° in the Z plane) and superimpose them, or transparent electrodes 423A to 423D as shown in FIG.
May be formed on the incident surface and the exit surface of the light beam and a voltage may be applied. In addition, in FIGS. 15A and 15B, 424
Is a power supply unit that applies a voltage to the phase modulator 402.

(Fifth Embodiment) FIG. 16 shows the schematic arrangement of a super-resolution optical head device according to the fifth embodiment of the present invention.

Since the fifth embodiment constitutes a simple optical system of a reciprocating optical path type, a compact super-resolution optical head is realized by using an integrated objective lens and hologram element as the light collecting means. .

As shown in FIG. 16A, the coherent light emitted from the coherent light source 500 is formed on a substrate 501 having a uniaxial anisotropy of refractive index, which is provided close to the coherent light source 500 on the outward path. A main beam (→) and a sub-beam (⊚) whose polarization planes are orthogonal to each other are generated by passing through the four-divided polarizing phase plate 502 (0, π / 2, π, 3π / 2). The main beam and the sub-beam pass through the hologram element 504 provided integrally with the objective lens 503, and the hologram element 504's 0
The next transmitted light is transmitted through the objective lens 503 to the optical disk 50.
No. 5 information storage surface 505a is superimposed and condensed. The reflected beam from the information storage surface 505a passes through the objective lens 503 and the hologram element 504 on the return path. The first-order diffracted light diffracted by the hologram element 504 travels outside the optical axis of the objective lens 503 and is formed in a region of the substrate 501 adjacent to the polarizing phase plate 502.
The light enters the polarizing diffraction grating 506 shown in FIG. The light incident on the polarization diffraction grating 506 is reflected by the polarization diffraction grating 5
After being polarized and separated into a main beam and a sub beam by 06, it is detected by a photodetector 508 shown in FIG. Note that FIG. 17C shows the light intensity distributions of the main beam and the sub beams.

The operation of the hologram element 504 and the method of detecting the super-resolution scanning signal by the photodetector 508 will be described in detail below.

First, the hologram element 504 has a beam splitter function of diffracting the returning light beam out of the optical axis of the objective lens 503 to separate it from the going light beam, and obtains a focusing signal and a tracking servo signal from the separated light beam. It has a combined function of forming a light beam and a function of detecting an RF signal. The signal can be formed by various methods, but in the fifth embodiment, as shown in FIG.
As shown in, the focusing error signal is obtained by the spot size detection (SSD) method and the tracking error signal is obtained by the push-pull (PP) method. The SSD method is disclosed in Japanese Patent Application No. 62-251025, etc., and the hologram element 504 of the fifth embodiment is used.
Is suitable for integration with the objective lens 503,
As a blazed hologram, it is constituted by superimposing two area-separated Fresnel zone plates as described in detail in the following documents.

Makoto Kato et al .; "Recent advances in
optical pickup head with holographic optical eleme
nts ", Proc. SPiE, vol.1507, pp36-44., EuropianCongr
ess on Optics, Holographic Optics III: Principles a
nd Applications, 12-15 March 1991, The Hague, The Net
herlands. In the fifth embodiment, the hologram element 504 is located on the coherent light source 500 side and the objective lens 503 is located on the optical disk 505 side, but these arrangements may be reversed.

As shown in FIG. 17A, on the substrate 509 of the photodetector 508 integrated with the coherent light source 500, element terminals 510a and 510b for detecting the SSD type focusing error signal are provided. Has been. The focusing error signal is transmitted to the element terminals 510a and 5a.
10b separates and detects a pair of light beams 511a and 511b formed by the main beam. Further, the tracking error signal is transmitted to the substrate 5 of the photodetector 508.
The element terminals 510c and 510d formed on the upper surface 09b of the light beam detect the light beams 511c and 511d.

The sub-beams are separated into ± 1st-order diffracted lights by the polarization diffraction grating 506, and element terminals 512a, 512b, 512c, 512 are provided on both sides of the main beam.
d, 512e, 512f, respectively. The super-resolution scanning signal is converted into an RF signal as an element terminal 510a,
From the total output signals of 510b, 510c and 510d, the element terminals 512a, 512b, 512c, 512d and 512 are output.
It is obtained by subtracting the total output signals of e and 512f. However, optimizing the calculation through each suitable amplifier circuit is a design problem, and therefore further description will be omitted.

In the fifth embodiment, the polarizing phase plate 50 is used.
Although 2 is divided into four, it goes without saying that it may be divided into other numbers of regions. Further, the manufacturing process of the polarizing phase plate 502 has already been described in detail together with the polarizing diffraction grating, and therefore will be omitted here.

The following effects can be obtained in the super-resolution optical head device according to the fifth embodiment. That is, since the optical system of the reciprocating optical path type is configured, a compact and simple optical head device of the super-resolution scanning optical system can be realized. The polarizing phase plate 520 and the polarizing diffraction grating 506 are the same substrate 5
Since it is formed close to No. 01, it is very stable.
Since the coherent light source 500 and the photodetector 508 are integrally integrated on the same substrate 509, they are easy to assemble and adjust and extremely stable against aging, temperature change and mechanical deformation. Incidentally, the coherent light source 500
The technique of providing the photodetector 508 and the photodetector 508 on the same substrate 509 is, for example, a structure for emitting a light beam perpendicular to the surface of the substrate 509 by an etched mirror integrally formed on a silicon substrate, and the photodetector 508 described above. It is well known as a structure integrated on a silicon substrate.

In addition, in the fifth embodiment, the tracking error signal is output from the element terminal 510c and the element terminal 51.
When detecting as a differential signal with the output signal of 0d, the sum of the output signal from the element terminal 512a and the output signal from the element terminal 512b is subtracted from the output signal from the element terminal 510c at an appropriate ratio, and the element By subtracting the sum of the output signal from the terminal 512c and the output signal from the element terminal 512d from the output signal from the element terminal 510d at an appropriate ratio, a tracking error during high-density recording, which was difficult with ordinary means, It is possible to detect the signal clearly.

The servo signal obtained as described above is
Integrated objective lens 503 and hologram element 50
Since feedback to the actuator 515 for driving No. 4 is a known technique, its description is omitted.

As described above, the embodiments of the present invention have been described in detail. Therefore, the present invention equivalently realizing a beam size of about 70% of the diffraction limit beam in the optical head device using the conventional optical system. The structure and operation of the super-resolution optical head device will be clearly understood.

An important effect of the present invention is that the numerical aperture of the objective lens is not increased (for example, NA = 0.45, wavelength λ = 0.78 μm in an optical head incorporated in a compact disc player). Also, without changing the light source wavelength,
That is, about twice as high a densified disc can be read. The depth of focus of the optical head in a compact disc player is about 1.5 μm, and focusing control is easy, but an objective lens with a high numerical aperture (for example, NA = 0.6) and a short-wavelength light source (for example, λ = 0) are used. .43 μm), the depth of focus is proportional to the wavelength and decreases inversely with the square of the numerical aperture.

1.5 μm × (430/780) × (0.45 / 0.60) ₂ = 1.5 μm × 0.31 (equal to approximately 0.47 μm) (13) Therefore, the super solution of the present invention When the image optical system is used in an optical head device, a high-density optical disc can be read by a simple and inexpensive player by using a short-wavelength light source, and a stable optical disc can be easily obtained even by using conventional servo signal detection technology and control technology. This is a great effect that the device can be realized.

In other words, according to the present invention, as a result of the differential calculation processing of the light intensity of the main beam and the light intensity of the sub beam, the focal depth based on the diffraction limit resolution of the objective lens is doubled. It has a very remarkable effect of deepening the above.

[0127]

According to the super-resolution optical head device of the first aspect of the invention, the main beam and the sub-beam which are incoherent to each other are superposed and scanned on the surface to be scanned, and the main beam is an Airy disc-shaped pattern or beam. A beam profile having an intensity peak at the center is formed, and the sub-beam has a bimodal intensity distribution in which the size of the main part is equal to the main beam and the peak values are at least on both sides of the beam center. The beam is separated from the information storage surface after being reflected by the different polarization planes or wavelengths, is independently guided to the photodetector, and the light intensity is differentially processed. Regarding the resolution performance of, the beam width of about 70% can be equivalently realized beyond the diffraction limit of the objective lens used.

Further, on the information storage surface, the main beam and the sub beam superposed as coaxial beams can be easily utilized by utilizing the property that these two beams have mutually orthogonal polarization planes or different wavelengths. Since it is possible to spatially separate and detect light, it is possible to obtain a simple and reliable super-resolution optical signal.

The generation of the sub-beam having the bimodal intensity distribution has a relative phase difference of 0 to π with respect to the wavelength of the transmitted light.
It can be easily realized by a phase plate having a step difference that shifts to, and by irradiating the phase plate with coherent light having almost the same intensity distribution as the main beam, the peripheral part of the bimodal beam is surrounded by the main beam periphery. The intensity distribution substantially the same as that of the part can be realized. Such beam waveform shaping can be performed by optimizing the aperture diameter of the opening through which the main beam or the sub beam passes.

According to the super-resolution optical head device of the second aspect of the present invention, since the generation of the sub-beam is realized by the hologram element of the phase plate, even if the phase plate manufacturing process requires complicated processing. , Only one phase plate itself is required, and it is industrially possible to mass-produce and use hologram elements. Moreover, without actually manufacturing the phase plate, a computer-generated hologram that is simply designed on a computer is used. Since it is also possible to use the method, the degree of freedom in designing and manufacturing is greatly increased.

According to the super-resolution optical head device of the third aspect of the present invention, since the phase plate of the first or second aspect is realized as an axially symmetric polarizing phase plate, the super-resolution optical system of the first or second aspect is used as an axis. It is possible to obtain a great effect that the performance is equivalent to that of a symmetric super-resolution beam optical system and that it can be realized simply and stably.

According to the super-resolution optical head device of the fourth aspect of the present invention, since the phase plate is provided integrally with the second coherent light source, a stable sub-beam can be obtained with a simple structure.

According to the super-resolution optical head device of the fifth aspect of the present invention, the generation of the polarization planes of the main beam and the sub-beams orthogonal to each other in the first or second aspect of the invention simply causes the pair of linearly polarized lasers to emit light. Since it can be realized only by setting a predetermined positional relationship, the objective can be achieved with an optical system having a simple structure.

According to the super-resolution scanning optical device in the sixth aspect of the present invention, since the polarization separation can be realized by the polarization hologram element or the diffraction grating on the flat plate, it is more compact than the case where the polarization beam splitter is used. Moreover, a low-cost super-resolution scanning optical system can be realized.

According to the super-resolution optical head device of the seventh aspect of the present invention, since wavelength separation can be realized by the multilayer dielectric filter, the narrow bandpass characteristic of the filter and the reflectance characteristic having its inverse characteristic are used. Two wavelengths with a small wavelength difference can be efficiently separated and detected.

According to the super-resolution optical head device of the present invention, the beam emitted from a single coherent light source is guided to the polarizing phase plate, and the surface to be scanned is provided on the conjugate surface thereof. Are scanned without their optical axes being displaced at all, and an extremely stable and high-quality super-resolution scanning optical system can be realized with an extremely simple configuration.

According to the super-resolution optical head device of the ninth aspect, a compact and low-cost super-resolution scanning optical system can be realized as in the sixth aspect of the invention.

According to the super-resolution optical head device of the tenth aspect of the present invention, the main beam and the sub-beam are generated at the same time as the polarization separation by guiding the coherent light emitted from the single coherent light source to the polarizing phase plate. Therefore, the intensity distributions of the peripheral portions of the main beam and the sub-beam are the same shape, and the optical axes do not deviate from each other even when the beam scanning is performed, and an extremely stable and high-performance super-resolution optical head device can be realized. .

According to the super-resolution optical head device of the eleventh aspect of the present invention, the super-resolution scanning optical system of the tenth aspect of the invention has a performance equivalent to that of the rectangular super-resolution beam optical system and is simple. It has the effect that it can be realized.

According to the super-resolution optical head device of the twelfth aspect of the invention, similar to the third aspect of the invention, the super-resolution scanning optical system of the first or second aspect is axially symmetric. It is possible to obtain a great effect that the performance is equivalent to, and can be realized simply and stably.

According to the super-resolution optical head device of the thirteenth aspect of the present invention, the signals of the main beam and the sub-beam which are time-separated by using a single coherent light source, a single integrated photodetector and a delay element are provided. Since the processing is performed, the super-resolution optical head device can be realized with a simple optical system.

According to the super-resolution optical head device of the fourteenth aspect of the invention, since the single coherent light source and the photodetector are provided on the same plane, assembly and adjustment are easy, and secular change, temperature change and The super-resolution optical head device can be realized with a compact and simple optical system because it is extremely stable against mechanical deformation and the light converging means and the hologram element are integrated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a super-resolution optical head device according to a first embodiment of the invention.

FIG. 2 is a schematic diagram showing, as a one-dimensional model, a sub-beam generation common to each embodiment of the present invention and a configuration principle of a super-resolution optical system.

FIG. 3 is a schematic view showing the principle of a super-resolution optical system common to each embodiment of the present invention with a simple one-dimensional model.

FIG. 4 is a schematic configuration diagram of a super-resolution optical head device according to a second embodiment of the invention.

FIG. 5 is a schematic configuration diagram of a super-resolution optical head device according to a third embodiment of the invention.

FIG. 6 is a schematic configuration diagram of a super-resolution optical head device according to a fourth embodiment of the invention.

FIG. 7 is a schematic configuration diagram of a polarizing hologram element in first and second embodiments of the present invention.

FIG. 8 is a diagram illustrating a configuration example of an integrated photodetector common to the first and second embodiments of the present invention.

FIG. 9 is a diagram illustrating a configuration example of a phase plate for generating a sub beam common to each embodiment of the present invention.

FIG. 10 is a diagram illustrating another configuration example of a phase plate for generating a sub beam common to each embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating a configuration example of a polarizing diffraction grating according to a fourth exemplary embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration example of a sub beam generating light source and a phase plate in a third embodiment of the present invention.

FIG. 13 is a diagram for explaining another configuration example of the sub beam generating light source and the phase plate in the third embodiment of the present invention.

FIG. 14 is a diagram illustrating a configuration example of a phase modulator according to a fourth embodiment of the present invention.

FIG. 15 is a diagram illustrating another configuration example of the phase modulator according to the fourth embodiment of the present invention.

FIG. 16 is a schematic configuration diagram of a super-resolution optical head device according to a fifth embodiment of the invention.

17A is a plan view showing a state in which a coherent light source and a photodetector in the fifth embodiment are formed on the same substrate, and FIG. 17B is a polarizing phase plate in the fifth embodiment. FIG. 6C is a plan view showing a state in which the and the polarization diffraction grating are formed on the same substrate, and FIG. 13C is a view showing the light intensity distributions of the main beam and the sub beam in the fifth embodiment.

FIG. 18 is a schematic configuration diagram illustrating a conventional super-resolution optical system using a ring-shaped aperture.

[Explanation of symbols]

100 Coherent Light Source 104 Polarizing Phase Plate (Phase Plate) 109 Objective Lens (Condensing Means) 110 Optical Disk 110a Information Storage Surface 111 Polarizing Hologram Element (Light Separation Means) (Polarization Separation Means) 113a First Photo Detector (Light Detection means) 113b second photodetector (light detection means) 113c third photodetector (light detection means) 117 differential calculator (calculation means) 118 electromagnetic drive means (drive means) 200 coherent light source 202 hologram Element 205 Objective lens (condensing means) 206 Polarizing hologram element (light separating means) (polarization separating means) 208a First photodetector (light detecting means) 208b Second photodetector (light detecting means) 208c 3 photodetector (photodetector) 211 differential calculator (calculator) 212 electromagnetic drive unit (drive unit) 213 light Disc 213a Information storage surface 300 First coherent light source 301 Second coherent light source 305 Objective lens (condensing means) 306 Optical disc 306a Information storage surface 308 Hologram element 309 Multilayer interference filter (light separating means) (wavelength separating means) 311 First photodetector (light detecting means) 313 Second photodetector (light detecting means) 316 Electromagnetic driving means (driving means) 400 Coherent light source 402 Phase modulator (phase modulating means) 407 Objective lens (condensing Means) 408 Optical disc 408a Information storage surface 411 Photodetector (photodetection means) 414 Differential calculator (calculation means) 416 Delay element (delay means) 419 Electromagnetic driving means (driving means) 500 Coherent light source 502 Polarizing phase plate 503 Objective lens (condensing means) 504 Holographic element 505 Optical disk 505a Information storage surface 506 Polarizing diffraction grating (polarization separating means) 508 Photodetector 515 Actuator (driving means)

 ─────────────────────────────────────────────────── (72) Inventor Hiroaki Yamamoto 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kazuhisa Yamamoto, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A first coherent light source which emits a first coherent light beam as a main beam, and a polarization plane orthogonal to a polarization plane of the first coherent light beam or a wavelength of the first coherent light beam. A second coherent light source that emits second coherent light having different wavelengths, and a beam main part that receives the second coherent light and has a peak value on at least both sides of the beam center in a plane perpendicular to the optical axis. A phase plate that emits a sub-beam having a light intensity distribution whose size is substantially equal to the size of the main part of the main beam; a main beam emitted from the first coherent light source; and a phase beam emitted from the phase plate. The information storage surface is provided with a condensing unit for superimposing the sub-beam on the information storage surface and a light beam formed by superposing the main beam and the sub-beam. Driving means for driving the focusing means so as to focus and track the optical information storage carrier, and the incidence of the light beam reflected from the information storage surface to polarize the light beam into a main beam and a sub beam. A light separating means for separating or separating the wavelengths and emitting the light; a light detecting means for separately detecting the light intensities of the main beam and the sub-beam emitted from the light separating means and outputting a light intensity signal; and the light detecting means. A super-resolution optical head device, comprising: a computing means for computing and outputting a super-resolution scanning signal based on the light intensity signal output from 2. A first coherent light source that emits coherent light as a main beam, and a polarization plane orthogonal to the polarization plane of the first coherent light, or a wavelength different from the wavelength of the first coherent light. A second coherent light source that emits the second coherent light, and a beam main part having a peak value on at least both sides of the beam center in a plane perpendicular to the optical axis upon receiving the second coherent light. A hologram element that emits a sub-beam having a light intensity distribution that is substantially equal to the size of the main part of the main beam, a main beam that is emitted from the first coherent light source, and a sub-beam that is emitted from the hologram element. And a light beam formed by superimposing the main beam and the sub-beam on the information storage surface. Driving means for driving the condensing means so as to focus and track an optical information storage carrier provided, and the incidence of the light beam reflected from the information storage surface, the main beam and the sub-beam A light separating means for emitting polarized light or wavelength separated light, and a light detecting means for separately detecting the light intensities of the main beam and the sub-beams emitted from the light separating means and outputting a light intensity signal, A super-resolution optical head device, comprising: a computing means for computing and outputting a super-resolution scanning signal based on the light intensity signal output from the light detecting means. 3. The phase plate is divided into N pieces (N is an integer of 2 or more) around the center of the phase plate, and is relative to the second coherent light emitted from the second coherent light source. Phase difference 0, 2π / N, (2π / N) × 2
(2π / N) × 3, ..., And (2π / N) · (2N−
2. The super-resolution optical head device according to claim 1, wherein the super-resolution optical head device has N areas for sequentially giving 1), and emits the second coherent light passing through the N areas as the sub-beam. 4. The super-resolution light according to claim 1, wherein the phase plate is provided close to or in close proximity to the second coherent light source and integrally with the second coherent light source. Head device. 5. The super laser according to claim 1, wherein the first and second coherent light sources are a pair of linearly polarized lasers arranged such that their polarization planes are orthogonal to each other. Resolution optical head device. 6. The light separating means comprises a substrate having a refractive index uniaxial anisotropy and a polarizing hologram element or a polarizing diffraction grating formed on the substrate, and the light beam is divided into the main beam and the light beam. 3. The super-resolution optical head device according to claim 1, wherein the super-resolution optical head device is a polarization splitting device that splits the light into polarized light into a sub beam. 7. The light separating means is a wavelength separating means composed of a multilayer film dielectric filter and wavelength-separating the light beam into the main beam and the sub beam. The super-resolution optical head device described in 1. 8. A coherent light source that emits coherent light, and a coherent light that is incident on the coherent light emitted from the coherent light source, has a main beam, and a plane of polarization orthogonal to the plane of polarization of the main beam. A polarizing phase plate which has a peak on at least both sides of the center of the main beam and which is split into a sub-beam having a light intensity distribution in which the size of the beam main part is substantially equal to the size of the main part of the main beam, A condensing means for superimposing a main beam and a sub-beam emitted from the polarizing phase plate on the information storage surface and condensing the main beam and the sub-beam on the information beam; Driving means for driving the condensing means to focus and track an optical information storage carrier provided on the storage surface, and light reflected from the information storage surface. When the beam is incident on the beam, the light beam is polarized and separated into a main beam and a sub beam and emitted, and the light intensities of the main beam and the sub beam emitted from the polarization beam splitter are detected separately. Super-resolution light, which comprises: a light detecting means for outputting a light intensity signal according to the above; and a calculating means for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detecting means. Head device. 9. The polarization separating means comprises a substrate having a refractive index uniaxial anisotropy and a polarizing hologram element or a polarizing diffraction grating formed on the substrate. Super resolution optical head device. 10. The light component having a polarization plane of the coherent light emitted from the coherent light source, the polarization component having a polarization plane in one direction, and the polarization component having a polarization plane in another direction orthogonal to the one direction. A first region that is polarized and separated into and emits a light component having a polarization plane in the one direction as the main beam, and does not give a relative phase difference to a light component having a polarization plane in the other direction. 9. The super-resolution optical head according to claim 8, further comprising: a second region that provides a relative phase difference of π, and a light component that passes through the first and second regions is emitted as the sub-beam. apparatus. 11. The first and second regions are formed so that two regions are alternately formed in four regions divided around the center of the polarizing phase plate.
The super-resolution optical head device described in 1. 12. The light component having coherent light emitted from the coherent light source, the light component having a polarization plane in one direction, and the light component having a polarization plane in another direction orthogonal to the one direction. The light component having a polarization plane in one direction is emitted without giving a relative phase difference, and is divided into N (N is an integer of 2 or more) around the phase plate. Relative phase difference 0, 2π / N, (2π / N) × 2, (2π
/ N) × 3, ..., And (2π / N) · (N−1) in order, and the light component passing through the N areas is emitted as the sub-beam. The super-resolution optical head device according to claim 8, which is characterized in that. 13. A coherent light source that emits coherent light having a first pulse train and second pulse trains that are alternately generated in time series with respect to each pulse of the first pulse train, and the incidence of the coherent light. Receiving the coherent light, by selectively giving a phase shift to the wavefront of the coherent light in synchronization with the first and second pulse trains,
A main beam composed of the first pulse train, and a main beam composed of the second pulse train, having a peak value on at least both sides of the beam center in a plane perpendicular to the optical axis of the main beam, and having a beam main portion size of the main beam. Phase modulating means for emitting a sub-beam having a light intensity distribution substantially equal to the size of the main part, and condensing means for condensing the main beam and the sub-beam emitted from the phase modulating means on an information storage surface. Driving means for driving the focusing means so that the main beam and the sub-beam are focused and tracked on an optical information storage carrier provided on the information storage surface, and a main beam reflected from the information storage surface, Light detection means for outputting the light intensity signal by sequentially detecting the light intensity of the sub-beam separately and sequentially, and the first light intensity signal output from the light detection means. Delay means for selectively providing a delay time corresponding to a pulse train interval between the pulse train and the second pulse train, a light intensity signal output from the photodetector means, and light given the delay time by the delay means. A super-resolution optical head device, comprising: a computing means for computing and outputting a super-resolution scanning signal based on the intensity signal. 14. A coherent light source that emits coherent light, a main beam of the coherent light emitted from the coherent light source, and a polarization plane orthogonal to the polarization plane of the main beam, and at least both sides of the center of the main beam. A polarizing phase plate which is split into a sub-beam having a peak in the beam and having a light intensity distribution substantially equal to the size of the main portion of the main beam, and which is emitted; And a light beam formed by superimposing the main beam and the sub-beam on the information storage surface, and a light beam formed by superposing the main beam and the sub-beam on the information storage surface. Driving means for driving the light converging means so as to focus and track the information storage carrier, and the light converging means are provided integrally with the drive means and reflected from the information storage surface. A hologram element that diffracts the return light beam and guides it on a plane substantially the same as the light emitting surface of the coherent light source, and receives the return light beam that is diffracted by the hologram element and receives the return light beam as a main beam. A polarization splitting means for splitting and outputting the polarized light into a sub beam and a sub beam, and the light intensity of the main beam and the sub beam emitted from the polarization splitting means, which are provided on substantially the same plane as the light emitting surface of the coherent light source. And a calculation means for calculating and outputting a super-resolution scanning signal based on the light intensity signal output from the light detection means. Super resolution optical head device.