JP3355722B2 - How to create a diffraction grating pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention uses a laser beam,
The present invention relates to a method of forming a dot-like diffraction grating pattern by the two-beam interference, and more particularly to a method of forming a diffraction grating pattern capable of easily forming a diffraction grating pattern having an arbitrary spatial frequency.

[0002]

2. Description of the Related Art In general, when a coherent light source such as a laser light source is used and a laser beam to be split into two light beams is simultaneously exposed on a photosensitive material again, interference fringes are recorded (diffraction grating). Is created).

The pitch of the interference fringes (the reciprocal of the spatial frequency) is determined by the difference between the angles of the two light beams incident on the photosensitive material.
The direction changes according to the incident direction of the two light beams, and the recorded density changes according to the light intensity. That is, during observation, the pitch of the interference fringes is related to the visible color, the direction of the interference fringes is related to the visible direction, and the density of the interference fringes is related to the luminance of the visible color.

A method of forming a diffraction grating by two-beam interference and forming a display having a diffraction grating pattern is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 60-1.
No. 56004, "Japanese Patent Application No. 63-222577"
And other methods have been proposed.

That is, the former method uses a diffraction grating exposure head and moves the diffraction grating exposure head to produce minute interference fringes (hereinafter, referred to as interference fringes) caused by two-beam interference.
This is a method in which a photosensitive material is successively exposed to light by changing its pitch, direction, and light intensity, and an arbitrary diffraction grating is formed at an arbitrary position.

By using this method, a display comprising a planar photosensitive material and a diffraction grating pattern formed on the surface thereof can be obtained. And since this diffraction grating pattern is composed of a plurality of minute dots formed by the diffraction grating, each dot shines in each color in each direction in each direction and each pattern is drawn. .

In the latter method, dots formed of a diffraction grating are formed at corresponding positions on a dry plate (made of glass coated with a photosensitive material) on an XY stage in accordance with image data read from a computer. It is a way to go.

By using this method, a display having an almost completely uniform diffraction grating pattern can be obtained.

However, the former method has the following problems.

That is, it is necessary to move the optical system of the diffraction grating exposure head each time the pitch, direction, and light intensity of the diffraction grating are changed. Since the optical system cannot be fixed as described above, the optical system is weak against vibration and easily affected by external vibration.

Therefore, not only a long waiting time is required to sufficiently attenuate the vibrations, but also the stability of the diffraction grating is poor, and a uniform (high accuracy) diffraction grating cannot be formed. There is.

The latter method has the following problem.

That is, since the spatial frequency of the diffraction grating to be formed is determined by branching the laser beam into several parts and selecting one of them, there is a problem that the light utilization efficiency is extremely low. is there.

Also, the number of branched laser beams is limited to about three because the spatial arrangement of the optical system and the light intensity are weakened.

Therefore, there is a problem that only a diffraction grating having about three kinds of spatial frequencies can be formed (the spatial frequency of the diffraction grating is limited to about three kinds).

Therefore, as an apparatus for solving the above-mentioned problem, a diffraction grating plotter such as Japanese Patent Application No. 3-219556 has been proposed by the present applicant.

However, in this type of diffraction grating plotter, XY (-
θ) Two laser beams are incident on the stage via a predetermined device configuration. In most cases, there is no possibility that the incident side can be moved or rotated, and it is very difficult to reduce the size.

Further, not only must the required laser beams be adjusted one by one on the surface of the dry plate, but also the intersection between the center of rotation of the θ stage and the laser beam must be the same. Adjustment of the optical system is also very difficult.

Further, even in the case of an apparatus which can be moved and rotated, a diffraction grating exposure apparatus (Japanese Patent Laid-Open No. 60-1560)
As disclosed in Japanese Unexamined Patent Application Publication No. 04-204, the configuration is relatively large and complicated, and it is very difficult to adjust the alignment of the two light beams on the dry plate.

Therefore, recently, as an apparatus for solving such a problem, for example, Japanese Patent Application No. 4-43056 has been proposed.
Grating plotters have been proposed by the applicant.

In this apparatus, one laser beam is diffracted by a rotatable two-beam diffraction grating and split into three or more laser beams, and two of the laser beams are selected.
This is an apparatus configured to condense these on a dry plate on an XY (-θ) stage that can be arbitrarily moved in a plane.

However, in such a diffraction grating plotter, since the angle between two laser beams reaching the dry plate is always constant, it is not possible to change the spatial frequency of the diffraction grating recorded on the dry plate. Can not.

For this reason, when a diffraction grating pattern is used for a display, for example, it is not easy to change the color depending on the location.

Also, a holographic optical element (HO)
E) It cannot be used for a device requiring a fine spatial frequency change, such as in the case of creation.

[0025]

As described above, the conventional apparatus for producing a diffraction grating has a problem that it is difficult to produce a diffraction grating pattern having an arbitrary spatial frequency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method of forming a diffraction grating pattern capable of easily forming a diffraction grating pattern having an arbitrary spatial frequency. Aim.

[0027]

In order to achieve the above object, a laser beam is divided into two light beams, which are simultaneously exposed to one point on a dry plate coated with a photosensitive material to record interference fringes. In the method of creating a diffraction grating pattern by dividing a laser beam into arbitrary directions and angles each time a dry plate is exposed, first, in the invention corresponding to claim 1, the laser beam is moved in a direction parallel to the dry plate surface. A hologram lens that can move in the same direction as the dry plate, divides the laser beam into any direction and angle, and moves parallel to the hologram surface is placed in the middle of the optical path of the thin laser beam that illuminates the dry plate The hologram lens is fixed at a position where the hologram lens forms an image on the surface of the hologram plate. After the movement, the light is divided into a 0th-order diffracted light and a + 1st-order diffracted light at an angle corresponding to the spatial frequency of the diffraction grating to be created, and then condensed at one point on a dry plate with a lens to record the diffraction grating. Each time a dry plate is exposed, the dry plate is moved by a distance corresponding to the diameter of the diffraction grating to be created, and a diffraction grating pattern is created on the dry plate surface of the dry plate.

Further, in the invention corresponding to claim 2, the laser beam which can move in the same direction as the dry plate is provided in the middle of the optical path of the thin laser beam which illuminates the dry plate which can move in the direction parallel to the surface of the dry plate. Divide into arbitrary directions and angles, arrange a hologram lens that can move in parallel to the hologram surface, and fix the lens at a position where the hologram lens forms an image on the dry plate surface of the dry plate, When exposing the dry plate, the laser beam is split into + 1st-order diffracted light and -1st-order diffracted light at an angle corresponding to the spatial frequency of the diffraction grating to be created by parallel movement of the hologram lens, and then the lens is placed on the dry plate. The diffraction grating is recorded by condensing the light on one point, and every time the dry plate is exposed, the dry plate is moved by a distance corresponding to the diameter of the diffraction grating to be formed, and diffracted onto the dry plate surface of the dry plate. So that to create a child pattern.

[0029]

Accordingly, in the method of forming a diffraction grating pattern according to the present invention, when a laser beam is divided into two light beams and one point on the dry plate is simultaneously exposed to form a diffraction grating, each time the dry plate is exposed, By dividing the laser beam into arbitrary directions and angles (split into 0th-order diffracted light and + 1st-order diffracted light, or + 1st-order diffracted light and -1st-order diffracted light),
The spatial frequency of the created diffraction grating can be arbitrarily changed.

As a result, a diffraction grating pattern having an arbitrary spatial frequency, which cannot be formed by the conventional method, can be easily formed, and a display or a large HOE can be formed.
It is extremely useful in creating.

The optical system for creating the diffraction grating pattern can be made relatively small and simple by using only a hologram lens, a lens, and a thin laser beam.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention uses a hologram lens that can move in parallel to the hologram plane, instead of the above-described rotatable two-beam diffraction grating, so that the spatial frequency of the created diffraction grating can be changed arbitrarily. To make it possible.

That is, in order to arbitrarily change the spatial frequency of the diffraction grating to be formed, it is possible to arbitrarily change not only the direction of the laser beam to be divided but also the angle at a portion corresponding to the rotatable grating. Need to be

The hologram lens is a hologram having a function of converging (or diverging) parallel light. When a thin laser beam is applied to a part of the hologram lens, as shown in FIGS. 4A to 4C, a first-order diffracted light is generated in a direction toward (or opposite to) the center of the hologram lens. Then, as shown in FIGS. 5A and 5B, the angle of the diffracted light is small near the center of the hologram lens and is large near the periphery.

For this reason, if a thin laser beam is applied to an arbitrary position on the hologram lens, the direction of the diffracted light can be arbitrarily changed within 360 degrees toward the center, and the angle of the diffracted light is also changed. Since the laser beam can be arbitrarily changed between 0 degrees and the diffraction angle around the hologram, it becomes possible to divide the laser beam into arbitrary directions and angles.

Therefore, if a hologram lens is installed in the portion where the above-mentioned rotatable two-beam diffraction grating is arranged so that it can be moved in a direction parallel to the hologram surface, this portion can be used. Since the laser beam can be divided into arbitrary directions and angles, it is possible to arbitrarily change the direction and angle of the diffraction grating to be formed.

Hereinafter, an embodiment of the present invention based on the above-described concept will be described in detail with reference to the drawings.

The diffraction grating pattern according to this embodiment is created as follows.

That is, first, a hologram lens is prepared.

This operation is performed using, for example, an optical system as shown in FIG. In the optical system shown in FIG. 2, a laser beam 1 generated from the same laser light source is split into two laser beams by a beam splitter 2.

One of the laser beams is reflected by the mirror 3 and expanded by the lens 4, and then is collimated by the collimator lens 5.
Becomes parallel light, and is reflected by the half mirror 6,
The dry plate 7 is reached. The other laser beam is reflected by the mirror 8 and diverged by the lens 9,
The light passes through the half mirror 6 and reaches the dry plate 7. Then, a hologram is created by interference between the two lights. This hologram is a hologram lens in which diffracted light converges at one point when parallel light is incident from a direction opposite to the time of shooting.

Next, using the hologram lens thus prepared, for example, an optical system as shown in FIG. 1 is formed to form a diffraction grating pattern.

In the optical system shown in FIG. 1, the dry plate 11 can be moved in a direction parallel to the surface of the dry plate.

The thick hologram lens 12 can move in a direction parallel to the hologram surface, that is, in the same direction as the dry plate 11.

Further, the optical axis of the lens 13 is
The hologram lens 12 is fixed to a position that is substantially perpendicular to the surface of the dry plate 1 and forms an image at the position of the dry plate surface of the dry plate 11. Here, a glass lens or a plastic lens is used as the lens 13.

For this reason, since the light emitted from the same position on the hologram lens 12 is imaged at one point by the lens 13, the light is focused on the same position on the dry plate 11 regardless of its direction and angle. Become.

Then, the thin laser beam 14 passes through the hologram lens 12 and the lens 8 via the shutter 15 and then reaches the dry plate surface of the dry plate 11.

Using such an optical system, a diffraction grating pattern is created by the following procedure.

(A) When the shutter 15 is opened, the position of the hologram lens 12 is adjusted so that the laser beam shines on the place where the first order diffracted light of a certain direction and angle can be obtained.

(B) Open the shutter 15 and perform exposure. At this time, the thin laser beam 14 is diffracted by the hologram lens 12 and divided into the 0th-order diffracted light and the + 1st-order diffracted light. Created.

(C) The shutter 15 is closed and the dry plate 11 is closed.
Is translated by a distance corresponding to the diameter of the diffraction grating to be created.

By repeating the above operations (a) to (c) many times and recording a diffraction grating on the entire surface of the dry plate 11, a diffraction grating pattern in a desired direction and spatial frequency can be obtained.

As described above, in the present embodiment, when forming a diffraction grating pattern, the thin laser beam 1 illuminating the dry plate 11 movable in a direction parallel to the dry plate surface is used.
4, a thick hologram lens 12 that can move in the same direction as the dry plate 11 and divides the laser beam 14 into arbitrary directions and angles is disposed.
The lens 1 is placed at a position where the image 2 is formed on the surface of the dry plate 11.
3 is fixed, and when the dry plate is exposed, the laser beam 14 is divided into arbitrary directions and angles by the hologram lens 12, that is, after being divided into 0th-order diffracted light and + 1st-order diffracted light. At 13, the diffraction grating is recorded by condensing light at one point on the dry plate 11, and every time the dry plate 11 is exposed, the dry plate 11 is moved by a distance corresponding to the diameter of the diffraction grating to be formed. A diffraction grating pattern is formed on the entire surface of the dry plate.

Therefore, the laser beam is split into two light beams,
When a diffraction grating is created by simultaneously exposing one point on a dry plate, the laser beam 14 is divided into arbitrary directions and angles each time the dry plate is exposed (to a 0th-order diffracted light and a + 1st-order diffracted light). The spatial frequency of the created diffraction grating can be arbitrarily changed.

As a result, a diffraction grating pattern having an arbitrary spatial frequency, which cannot be formed by the conventional method, can be easily formed, and a display or a large HOE can be formed.
It is extremely useful in creating.

As an optical system for forming a diffraction grating pattern, a hologram lens 12, a lens 13,
Since it is composed of only the thin laser beam 14 and the shutter 15, it is possible to make the configuration relatively small and simple.

It should be noted that the present invention is not limited to the above-described embodiment, but can be similarly implemented in the following manner.

(A) In the above embodiment, when the laser beam is divided into arbitrary directions and angles, the 0th-order diffracted light and +1
The case where the laser beam is divided into the next diffracted light has been described. However, the present invention is not limited thereto. The present invention can be similarly applied to the present invention.

FIG. 3 is a schematic diagram showing an example of the configuration of an optical system for realizing this kind of method of forming a diffraction grating pattern. The same parts as those in FIG. 1 are denoted by the same reference numerals.

That is, in the embodiment shown in FIG. 3, it is possible to move in the same direction as the dry plate 11 in the optical path of the thin laser beam 14 illuminating the dry plate 11 which can move in the direction parallel to the dry plate surface. A thin hologram lens 16 that divides the laser beam 14 into arbitrary directions and angles is arranged, and the lens 13 is fixedly arranged at a position where the hologram lens 16 forms an image on the dry plate surface of the dry plate 11. Is performed, the laser beam 14 is divided by the hologram lens 16 into 0-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light, and the 0th-order diffracted light is shielded by the light shielding plate 17. Thereafter, the + 1st-order diffracted light and the -1st-order diffracted light are condensed by the lens 13 at one point on the dry plate 11 to record a diffraction grating, and each time the dry plate 11 is exposed, the dry plate 11 is created. It is moved by a distance corresponding to the diameter of the diffraction grating, and so as to create a diffraction grating pattern on the dry plate entire surface of the dry plate 11.

In the method of this embodiment, as in the case of the embodiment of FIG. 1, a diffraction grating pattern of an arbitrary spatial frequency can be easily formed, and a display or a large HOE can be formed. It is extremely useful in going.

(B) The method of forming a diffraction grating pattern according to the present invention is not limited to use in the field of hologram displays.

For example, as one method of producing a large holographic optical element (HOE), a method of producing a large hologram as a collection of many small diffraction gratings having appropriate directions and spatial frequencies is proposed. However, the method of the present invention can be used as a method for realizing it.

In this case, in order to increase the diffraction efficiency for the purpose of use in a large holographic optical element, after forming a diffraction grating pattern as a thin hologram by the method of each embodiment of FIGS. 1 and 3, FIG. It is preferable to use the diffraction grating pattern as a thick hologram (volume hologram) by copying on a thick photosensitive material by a contact copy method.

In addition, the present invention can be implemented in various modifications without departing from the scope of the invention.

[0066]

As described above, according to the method for forming a diffraction grating pattern of the present invention, when a laser beam is divided into two light beams and exposed to one point on a dry plate simultaneously to form a diffraction grating, Each time the dry plate is exposed, the laser beam is divided into arbitrary directions and angles (divided into 0th-order diffracted light and + 1st-order diffracted light, or + 1st-order diffracted light and -1st-order diffracted light)
Therefore, it is possible to easily create a diffraction grating pattern having an arbitrary spatial frequency.

As a result, a diffraction grating pattern having an arbitrary spatial frequency, which cannot be formed by the conventional method, can be easily formed, and a display or a large HOE can be formed.
It is extremely useful in creating.

Further, since the optical system for forming the diffraction grating pattern is constituted only by the hologram lens, the lens, and the thin laser beam, it is possible to make the structure relatively small and simple. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an optical system for realizing a method of forming a diffraction grating pattern according to the present invention.

FIG. 2 is a schematic diagram showing a configuration example of an optical system for creating a hologram lens used in the embodiment.

FIG. 3 is a schematic diagram showing another embodiment of the optical system for realizing the method of forming a diffraction grating pattern according to the present invention.

FIG. 4 is a conceptual diagram showing an example of how diffracted light is generated when a thin laser beam is applied to a part of a hologram lens.

FIG. 5 is a conceptual diagram showing an example of an angle of diffracted light generated when a thin laser beam is applied to a part of the hologram lens.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... laser beam, 2 ... beam splitter, 3 ... mirror, 4 ... lens, 5 ... collimator lens, 6 ... half mirror, 7 ... dry plate, 8 ... mirror, 9 ... lens, 11 ... dry plate, 12 ... thick hologram lens, 13 ... Lens, 14
... thin laser beam, 15 ... shutter, 16 ... hologram lens, 17 ... light shielding plate.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 5/18 G03H 1/04

Claims (2)

(57) [Claims] When a laser beam is divided into two light beams, and these are simultaneously exposed to one point on a dry plate coated with a photosensitive material to record interference fringes, the laser beam is applied each time the dry plate is exposed. In the method of creating a diffraction grating pattern by dividing into arbitrary directions and angles, moving in the same direction as the dry plate in the middle of the optical path of a thin laser beam that illuminates a dry plate that can move in a direction parallel to the dry plate surface It is possible to divide the laser beam into arbitrary directions and angles, arrange a hologram lens that can move in parallel to the hologram surface, and at a position where the hologram lens is imaged on the dry plate surface of the dry plate. When the lens is fixedly arranged, and when the exposure of the dry plate is performed, the laser beam is converted into a spatial frequency of a diffraction grating to be created by parallel movement of a hologram lens. After splitting into a 0th-order diffracted light and a + 1st-order diffracted light at the same angle, the lens focuses the light on one point on the dry plate to record a diffraction grating. A method of forming a diffraction grating pattern, wherein a dry plate is moved by a distance corresponding to a diameter of a diffraction grating to be formed, and a diffraction grating pattern is formed on a dry plate surface of the dry plate. 2. When dividing a laser beam into two light beams and simultaneously exposing them to one point on a dry plate coated with a photosensitive material to record interference fringes, the laser beam is applied every time the dry plate is exposed. In the method of creating a diffraction grating pattern by dividing into arbitrary directions and angles, moving in the same direction as the dry plate in the middle of the optical path of a thin laser beam that illuminates a dry plate that can move in a direction parallel to the dry plate surface It is possible to divide the laser beam into arbitrary directions and angles, arrange a hologram lens that can move in parallel to the hologram surface, and at a position where the hologram lens is imaged on the dry plate surface of the dry plate. When the lens is fixedly arranged, and when the exposure of the dry plate is performed, the laser beam is converted into a spatial frequency of a diffraction grating to be created by parallel movement of a hologram lens. After splitting into a + 1st-order diffracted light and a -1st-order diffracted light at the same angle, the lens collects a diffraction grating by condensing it at one point on the plate, and every time the plate is exposed, A method of forming a diffraction grating pattern, wherein the dry plate is moved by a distance corresponding to a diameter of a diffraction grating to be formed, and a diffraction grating pattern is formed on a dry plate surface of the dry plate.