JP3429571B2 - Multi-channel Fourier spectrometer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel Fourier spectroscopy apparatus which has the advantages of both multi-channel spectroscopy and Fourier spectroscopy.

[0002]

2. Description of the Related Art Conventionally, as this type of multi-channel Fourier spectroscopic device, there is, for example, a first prior art spectroscopic device shown in FIG. 8 disclosed in Japanese Patent Laid-Open No. 2-147843. This spectroscopic device is applied to the luminescence detection of a sample obtained by liquid chromatography. Light emitted from a flow cell (light source to be measured) 1 for detecting emitted light is collected by a condensing optical system 2 and enters a Wollaston prism 5 via a collimator lens 3 and a polarizer 4. The light incident on the Wollaston prism 5 is divided into polarization components orthogonal to each other, and each of the divided polarization components is analyzed by an analyzer 6 and an imaging lens 7 to form a one-dimensional or two-dimensional photodetector (multi-channel photodetector). ) 8 and forms interference fringes. This interference fringe is Fourier-transformed by the computer 9, and the spectrum of the emitted light from the flow cell 1 is measured.

There is also a spectroscopic device according to the second prior art shown in FIG. 9 disclosed in Japanese Patent Laid-Open No. 1-176921. This spectroscopic device is characterized by removing background noise by performing a predetermined calculation on the interference fringe data, and the light emitted from the measured light source 11 is spectroscopically measured. The light emitted from the light source to be measured 11 is emitted from the collimator lens 1 as in the case of the first prior art.
Wollaston prism 14 through 2 and polarizer 13
Incident on. The light incident on the Wollaston prism 14 is divided into predetermined polarization components, and the interference fringes of the measured light source 11 are detected by the analyzer 15 and the imaging lens 16 on the detection surface of the photodiode array (multi-channel photodetector) 17. Image on. The interference fringe data obtained in the photodiode array 17 is synchronized with the clock signal by the video amplifier (V) 1
The signal is amplified by 8 and read by the AD converter 19. The read-out data becomes a digital signal and is processed by an arithmetic processing unit (C
PU) 20. The CPU 20 processes the input digital signal directly or processes the data, and temporarily stores the data (RAM).
It is stored in 21. The device is an input / output interface (I
F) 22 is controlled by the input device (KYB) 23, and the measurement result is displayed via the IF 22 on the display device (C).
RT) 24.

In addition, the literature "Spectroscopic Research Vol. 38, No. 6 (1
989) ”, pages 415-424, entitled Multichannel Fourier Spectroscopy, and there is also a third prior art spectroscopic device shown in FIG. Light source to be measured 31
Is extracted by the polarizer 32 from only the polarized component having an inclination of 45 degrees with respect to the Savart plate 33 located thereafter. Then, it is split into two components of light by the Savart plate 33 and emitted at the same angle as the incident angle. Savart plate 33
The polarized light components of the two components of the light emitted from are combined by the analyzer 34, and are superimposed on the detection surface of the multi-channel photodetector 36 by the imaging lens 35. At this time,
An interference fringe including a spectral component of the light source 31 to be measured is formed on the detection surface due to the wavelength difference between the two components of light.

[0005]

However, in any of the conventional spectroscopic devices described above, when the spread of the light source of the light source to be measured is small, the interference range of the polarization components on the multi-channel photodetector is narrow. Become. Therefore, the interference fringes cannot cover the entire detection surface of the multi-channel photodetector, and effective multi-channel detection, that is, high-precision spectroscopic spectrum measurement cannot be performed. Further, in order to widen this interference range, the focal length of the imaging lens may be lengthened, but if the focal length is lengthened, the device becomes large.

Further, with respect to the crystals such as the Wollaston prism and the Savart plate used as the polarization birefringent crystal in the above-mentioned prior art, the price thereof increases exponentially as the crystal size increases. Therefore, when the light source size of the measured light source becomes large, the luminous flux area becomes wider,
A very large polarization birefringent crystal is required, which makes the device expensive.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a lens for forming light from a light source to be measured to form an aerial image and the aerial image to be incident. Light scattering means that scatters and emits light, a polarizer that extracts a polarization component having a predetermined polarization angle from this scattered light, a Savart plate that splits this polarization component, and the polarization direction of each split light is matched An analyzer, an imaging lens that forms an image of the light emitted from the analyzer, a multi-channel photodetector that detects the interference fringes formed by the image formation, and the spectrum of the light source to be measured from the interference fringes. And a signal processing means for obtaining by the Fourier transform method.

The light scattering means is a tapered fiber plate, a microlens array or frosted glass.

[0009]

The light flux of the aerial image formed by the lens is expanded by the light scattering means and is incident on the Savart plate. Therefore, the light beams divided by the Savart plate generate interference fringes in a wide range of the detection surface of the multi-channel photodetector.

When a tapered fiber plate is used as the light scattering means, the area occupied by the aerial image emitted from the light scattering means to the Savart plate in space is reduced. Therefore, even if the light source of the measured light source has a large spread, a large Savart plate is not required.

[0011]

1 is a block diagram conceptually showing an example of a measuring system of a multi-channel Fourier spectroscopy apparatus according to the present invention.

The light beam emitted from the light source 41 to be measured is expanded by the objective lens 42 and is imaged in space as an aerial image 43. The optical image path of the formed aerial image 43 is changed to the relay lens system 47 side by the mirror 45 and is formed on the video camera 48. At this time, a magnified image of the measured light source 41 is displayed on the monitor 49 connected to the video camera 48. The variable mask 50 designates the measurement range of the aerial image 43 while observing the monitor image. That is, when the opening amount of the variable mask 50 is widened, the monitor 49 monitors the image of the light source 41 to be measured and the entire periphery thereof as shown in FIG. By adjusting and narrowing the opening amount, the measurement range of the measured light source 41 on the monitor 49 is limited to the rectangular opening portion of the variable mask 50 as shown in FIG. By this operation, incident light outside the measurement range is blocked. Next, the switching device 44 moves the mirror 45 and places the tapered fiber plate 46 at that position. The light flux whose range is designated by the variable mask 50 is incident on the tapered fiber plate 46 immediately behind the image formation position of the aerial image 43. Since this incident light beam is expanded by the objective lens 42, its spread is generally 0.
It is as small as about 01. By making this incident on the tapered fiber plate 46, the beam is scrambled and becomes a light beam having a spread. Moreover, since it is a tapered fiber plate, the area of incident light is 1
It is reduced to about / 4. Tapered fiber plate 46
The light flux emitted from the
A component having a polarization angle of 45 ° with respect to 2 is extracted. The extracted light fluxes are two light fluxes that are parallel to the incident angle and have different polarization angles of 90 ° by the Savart plate 52. The analyzer 53 selects only the same component of polarization of the two light fluxes, and forms an image on the detection surface of the multi-channel photodetector 55 by the lens system 54. At this time, since an optical path difference is generated between the two light fluxes, interference fringes are formed on the detection surface of the multi-channel photodetector 55.

FIG. 3 shows an observation optical system of a spectroscopic device according to an embodiment of the present invention in which an example of the above-described multi-channel Fourier spectroscopic device according to the present invention is applied to a microscope, and FIG. 4 shows an interference fringe of the spectroscopic device. 3 shows a forming optical system. Next, with reference to these figures, a microspectroscopy using the multi-channel Fourier spectroscopy apparatus according to the present embodiment will be described.

As described above, the minute light source 61, which is the object to be measured, is magnified by the objective lens 62 and forms an aerial image 63 in space. A switching device 64 is provided behind the aerial image 63. The switching device 64 includes a 30 ° prism 65 as an optical path changing means and a tapered fiber plate 66 as a light scattering means, which are installed on the same surface, and these are switched by a slide guide. That is, the switching device 64 constitutes a switching means for replacing the optical path changing means with the light scattering means. When the switching device 64 is operated to switch to the 30 ° prism 65, the optical system shown in FIG. 3 for observing the image of the micro light source 61 to be measured is configured. Further, when switching to the tapered fiber plate 66, the optical system shown in FIG. 4 for forming an interference fringe including the spectral spectrum information of the micro light source 61 to be measured is configured.

By means of the switching device 64, 30 shown in FIG.
When the prism 65 is selected, the micro light source 61 to be measured which is formed as an aerial image 63 in space by the objective lens 62.
The light flux of is incident on the 30 ° prism 65. The optical path of the incident light flux is changed to an optical system for observing the image, and the relay lens system 67 forms an image of the micro light source 61 to be measured on the imaging surface of the video camera 68. The monitor 69 connected to the video camera 68 has a micro light source 6 to be measured.
A magnified image of 1 is projected. In addition, the variable mask 7 is placed at the position of the aerial image 63 formed in space by the objective lens 62.
0 is installed, and the image of the variable mask 70 is also displayed on the monitor 69.
Projected on. The opening area of the variable mask 70 through which a predetermined area of the aerial image 63 passes can be adjusted by a variable mask opening amount adjusting mechanism. Therefore, the unnecessary portion of the aerial image 63 is covered by adjusting the opening amount of the variable mask 70 while observing the monitor 69, and the measurement unit is limited.

Next, the switching device 64 causes the 30 ° prism 65 to move to the tapered fiber plate 66 shown in FIG.
When replaced by, only the light flux of the measured minute light source 61 in the range limited by the variable mask 70 is incident on the tapered fiber plate 66. At this time, the light flux emitted from the objective lens 62 to form the aerial image 63 is a light flux with a small numerical aperture NA of about 0.01 and a small spread.

The tapered fiber plate 66 is shown in FIG.
As shown in (a), it has a multi-fiber structure in which fibers of several μm are bundled. Further, since the individual fibers are formed in a tapered shape, the outgoing light size is reduced and transmitted at the same ratio, and the light flux emitted from the tapered fiber plate 66 becomes the incident light as shown in FIG. Compared to this, the luminous flux becomes wider. Although the tapered fiber plate 66 is described as the light scattering means here, the microlens array 77 shown in FIG. 5B or the frosted glass 78 shown in FIG. 5C can be used as the light scattering means. is there. Also with these scattering elements, it is possible to give a certain degree of spread to a light beam having a small NA of about 0.01. The microlens array 77 has a structure in which minute lenses having short focal lengths are arranged vertically and horizontally, and the focal lengths are very short. Therefore, only by arranging the microlens array 77 at the rear of the image formation position of the aerial image 63, a light flux having a large emission angle with respect to the incident angle is emitted due to the image forming action of the microlens array 77. Further, the frosted glass 78 has a sanded surface on one side or both sides, and the surface of this sanded surface has various uneven shapes.
Incident light is variously refracted and scattered on this uneven surface, diffused and emitted as shown in the figure.

Tapered fiber plate 66 shown in FIG.
From the scattered light flux emitted from the polarizer 71, a component having a polarization angle of 45 ° with respect to the Savart plate 72 is extracted by the polarizer 71. The light flux extracted by the polarizer 71 is converted by the Savart plate 72 into two parallel light fluxes having the same exit angle with respect to the incident angle. The polarization angles of these light beams differ from each other by 90 °. Only the same component of the polarization of these two light fluxes is selected by the analyzer 73, and the lens system 7
An image is formed at one point on the detection surface of the multi-channel array photodetector 75 by means of 4. Since an optical path difference is generated between the two image-formed light fluxes, an interference fringe including the spectral spectrum information of the measured minute light source 61 is formed on the detection surface of the multi-channel array photodetector 75. The interference fringe data is input to the signal processing device 76 and Fourier-transformed to obtain the spectral spectrum of the micro light source 61 to be measured.

The multi-channel Fourier spectroscopy apparatus according to this embodiment has the following effects. That is, the aerial image 6 magnified by the microscope objective lens 62 and the like.
As for the spread of the light flux of No. 3, the NA is about 0.01 as described above, and the spread of the light flux is small. Considering a device that splits this light flux into two light fluxes by the Savart plate 72 or the like and causes the light fluxes to interfere with each other by a lens, the lens system 74 needs to have a long focal length. However, in this embodiment,
An aerial image 63 with a small spread of the light flux from the objective lens 62.
The light beam is spread by the light scattering means such as the tapered fiber plate 66 and is incident on the Savart plate 72. Therefore, the light beams divided by the Savart plate 72 generate interference fringes in a wide range of the detection surface of the multi-channel photodetector 75. Therefore, detailed interference fringe data can be obtained, and highly accurate spectral spectrum measurement can be performed. Further, in order to generate interference fringes in a wide range of the detection surface of the multi-channel photodetector 75, it is not necessary to make the focal length of the lens system 74, which is an imaging lens, long. That is, it is possible to use the lens system 74 having a short focal length by using the light scattering means such as the tapered fiber plate 66 and expanding the beam, and the device can be made compact, that is, downsized.

When the tapered fiber plate 66 is used as the light scattering means, the area occupied by the aerial image emitted from the light scattering means to the Savart plate 72 is reduced. Therefore, even if the light source of the measured light source has a large spread, a large Savart plate is not required.
That is, although the crystal used in the birefringent double image element such as the Savart plate 72 has an exponential increase in price due to its size, according to this embodiment, the tapered fiber plate 66 is used.
By adopting, it is possible to reduce the size of the detected light flux image, and it is possible to measure the spectral spectrum of the light source to be measured with a wide spread of the light source using the small and inexpensive Savart plate 72. Further, the lens system 7 arranged at the rear side
The diameter of No. 4 can also be reduced, the device design can be facilitated, and the cost and size of the device can be reduced.

FIG. 6 shows an observation optical system of a spectroscopic device according to another embodiment in which an example of the multi-channel Fourier spectroscopic device of the present invention shown in FIG. 1 is applied to a telescope, and FIG. 7 shows interference of this spectroscopic device. 3 shows a fringe forming optical system.

The difference between this embodiment and the above-mentioned embodiment is that
First, the measured object is different. That is, in the above-described embodiment, the minute light source 61 is the object to be measured, and the multi-channel Fourier-spectroscopic device is applied to the microspectroscopic light. The luminous flux is the object to be measured. Also,
The present embodiment and the above embodiment also differ in the structure of taking in a light flux from the outside. That is, in the above embodiment, the light flux from the micro light source 61 to be measured was taken in by the objective lens 62 of the microscope, but in this embodiment, the light flux 79 from the distant light source is taken in through the objective lens of the telescope 80. .

The light beam taken in by the telescope 80 is reduced and is formed as an aerial image 81 in space as shown in FIG. A switching device 82 is provided behind the aerial image 81 as in the above embodiment. This switching device 8
Reference numeral 2 includes a 30 ° prism 83 as an optical path changing means and a tapered fiber plate 84 as a light scattering means, which are installed on the same surface, and these are switched by a slide guide. When the switching device 82 is operated to switch to the 30 ° prism 83, the observation optical system shown in FIG.
When switched to, the interference fringe forming optical system shown in FIG. 7 is configured.

When the 30 ° prism 83 shown in FIG. 6 is selected, the light flux of the object to be measured which is imaged as an aerial image 81 in space by the telescope 80 enters the 30 ° prism 83. The optical path of the incident light flux is changed to an optical system for observing the image, and the relay lens system 85 forms an image of the DUT on the imaging surface of the video camera 86. A reduced image of the object to be measured is displayed on the monitor 87 connected to the video camera 86. A variable mask 88 is installed at the position of the aerial image 81 formed in space by the telescope 80, and the image of the variable mask 88 is also displayed on the monitor 87. Therefore, the variable mask 88 is observed while observing the monitor 87.
The unnecessary portion of the aerial image 81 is covered by adjusting the aperture amount of the measurement area, and the measurement unit is limited.

When the 30 ° prism 83 is replaced with the tapered fiber plate 84 shown in FIG. 7, only the light flux of the object to be measured in the range limited by the variable mask 88 is incident on the tapered fiber plate 84. At this time, the light beam emitted from the telescope 80 to form the aerial image 81 is a light beam with a small spread. The light flux that has entered the tapered fiber plate 84 is transmitted with the emitted light size reduced as described above, and the emitted light flux becomes a light flux that is wider than the incident light. Also in this embodiment, the tapered fiber plate 8 is used as the light scattering means.
Instead of 4, it is also possible to use the above-mentioned microlens array 77 and frosted glass 78. The light flux emitted from the tapered fiber plate 84 is changed by the polarizer 89.
A component having a polarization angle of 45 ° with respect to the Savart plate 90 is extracted therefrom. This light flux becomes two parallel light fluxes having the same emission angle with respect to the incident angle and different polarization angles by 90 ° due to the Savart plate 90. Only the same component of polarization of these two light fluxes is selected by an analyzer 91, and an image is formed on a detection surface of a multi-channel array photodetector 93 by a lens system 92. Since an optical path difference is generated between the two image-formed light fluxes, the multi-channel array photodetector 9
Interference fringes including the spectral spectrum information of the distant light source are formed on the detection surface of 3. This interference fringe data is input to the signal processing device 94 and Fourier-transformed to obtain the spectrum of the DUT.

Also in this embodiment, the same effect as that of the above-mentioned embodiment can be obtained. That is, the aerial image 81 from which the spread of the light flux from the telescope 80 is small is spread by the light scattering means such as the tapered fiber plate 84,
The light enters the Savart plate 90. Therefore, the light beams divided by the Savart plate 90 generate interference fringes in a wide range of the detection surface of the multi-channel photodetector 93. Therefore, detailed interference fringe data can be obtained and highly accurate spectral spectrum measurement can be performed. Further, a lens system 92 having a short focal length can be used, and the device can be made compact.

When the tapered fiber plate 84 is used as the light scattering means, the area occupied by the aerial image emitted from the light scattering means to the Savart plate 90 is reduced. Therefore, even if the light source of the measured light source has a large spread, a large Savart plate is not required.
Therefore, also in the present embodiment, it is possible to measure the spectral spectrum of the light source to be measured in which the light source spreads widely using the small and inexpensive Savart plate 90. Further, the diameter of the lens system 92 arranged at the rear can be made small, the device design can be facilitated, and the cost and size of the device can be reduced.

[0028]

As described above, according to the present invention, the light flux of the aerial image formed by the lens is expanded by the light scattering means and is incident on the Savart plate. Therefore, the light beams divided by the Savart plate generate interference fringes in a wide range of the detection surface of the multi-channel photodetector. Therefore, detailed interference fringe data can be obtained and highly accurate spectral spectrum measurement can be performed. Further, since interference fringes are generated in a wide range of the detection surface of the multi-channel photodetector, it is not necessary to increase the focal length of the imaging lens, and the device can be downsized.

When a tapered fiber plate is used as the light scattering means, the area occupied by the aerial image emitted from the light scattering means to the Savart plate in space is reduced. Therefore, even if the light source of the measured light source has a large spread, a large Savart plate is not required. Therefore, even with a small and inexpensive Savart plate, it is possible to measure the spectral spectrum of the light source to be measured in which the light source spreads widely.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of a multi-channel Fourier spectroscopy apparatus according to the present invention.

FIG. 2 is a diagram showing a monitor in the spectroscopic device shown in FIG.

FIG. 3 is a diagram showing an observation optical system of a multi-channel Fourier spectroscopy apparatus according to an embodiment of the present invention.

4 is a diagram showing an interference fringe forming optical system of the spectroscopic device shown in FIG.

FIG. 5 is a diagram showing various light scattering means.

FIG. 6 is a diagram showing an observation optical system of a multi-channel Fourier spectroscopy apparatus according to another embodiment of the present invention.

7 is a diagram showing an interference fringe forming optical system of the spectroscopic device shown in FIG.

FIG. 8 is a diagram showing a multi-channel Fourier spectroscopy apparatus according to the first prior art.

FIG. 9 is a diagram showing a multi-channel Fourier spectroscopy apparatus according to a second conventional technique.

FIG. 10 is a diagram showing a multi-channel Fourier spectroscopy apparatus according to the third prior art.

[Explanation of symbols]

41 ... Light source to be measured, 42 ... Objective lens, 43 ... Aerial image,
44 ... Switching device, 45 ... Mirror, 46 ... Tapered fiber plate, 47 ... Relay lens system, 48 ... Video camera, 49 ... Monitor, 50 ... Variable mask, 51 ... Polarizer, 52 ... Savart plate, 53 ... Analyzer, 54 ... Lens system, 55 ... Multi-channel photodetector.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 3/00-3/52 G01J 4/00-4/04 G01J 9/00-9/04 G01N 21 / 00-21 / 01 G01N 21 / 17-21 / 61 Practical file (PATOLIS) Patent file (PATOLIS) JISST file (JOIS)

Claims (4)

(57) [Claims] 1. A lens for forming an aerial image by entering light from a light source to be measured, a light scattering means for entering, scattering and emitting the aerial image, and a predetermined polarization angle from the scattered light. A polarizer that extracts the polarized component that has, a Savart plate that divides this polarized component, an analyzer that matches the polarization direction of each divided light, and an imaging lens that forms an image of the light emitted from this analyzer, A multi-channel photodetector for detecting interference fringes formed by imaging, and a signal processing means for obtaining a spectrum of the light source to be measured from the interference fringes by a Fourier transform method. Fourier spectroscopy device. 2. The multi-channel Fourier spectroscopy apparatus according to claim 1, wherein the light scattering means is a tapered fiber plate, a microlens array, or frosted glass. 3. A variable mask for passing a desired area of the aerial image formed by the lens, wherein the light scattering means makes an aerial image of an area selected by the variable mask incident. Item 2. The multi-channel Fourier spectroscopy apparatus according to Item 1. 4. An optical path changing means for changing an optical path of an aerial image passing through the variable mask, an observing means for observing an aerial image guided by the optical path changing means, and the variable mask while observing the aerial image. 4. The multi-channel Fourier spectroscopic apparatus according to claim 3, further comprising a variable mask aperture amount adjusting mechanism for adjusting the aperture area of the above, and a switching unit for replacing the optical path changing unit with the light scattering unit.