JP3125688B2 - Diffraction grating 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 diffraction grating spectrometer, and more particularly to a diffraction grating spectrometer that uses a diffraction grating to measure light in a plurality of wavelength bands with high resolution in optical spectrum measurement.

[0002]

2. Description of the Related Art Generally, a Michelson interferometer realizing a high spectral resolution is used as an apparatus for measuring a light spectrum such as a gas absorption and emission spectrum. This Michelson interferometer requires a complicated driving mechanism, so that it is increased in size, and a Fourier transform is required to have a high-performance computer. In addition, since an access time is required for performing mechanical scanning, it takes a long time to measure, and it is difficult to measure a phenomenon with a large time change. The drive mechanism requires reliability and maintenance work. Further, the Michelson interferometer may acquire an unnecessary spectrum because the wavelength range of the measurement target is wide. As an example of an apparatus in which such an interferometer is improved, a “spectroscope” described in Japanese Patent Application Laid-Open No. 5-281041 is known.

[0003] In this publication, a folding optics comprising a diffraction grating movable by a drive mechanism and light reflecting means for detecting the intensity of light having a specific wavelength by detecting light in a specific emission direction of light. The system is used to reciprocate the light beam to one diffraction grating to exert a spectral effect twice to improve the resolution of the light beam. In addition, although a technique for reducing the size of the spectroscope is described because a folding optical system is used, a driving mechanism still exists.

A diffraction grating spectrometer such as an echelle diffraction grating spectrometer can obtain a high spectral resolution using a high-order diffracted light without a driving mechanism. These diffraction grating spectrometers perform order separation (coarse spectroscopy) using a prism or a diffraction grating (separately installed coarse spectroscopic diffraction grating), and perform high-precision spectroscopy using a diffraction grating such as an echelle diffraction grating for fine spectroscopy. Thus, a two-dimensional spectral image is obtained.

[0005] However, in the spectrometer using the echelle diffraction grating, the dispersion is increased in order to increase the resolution. By performing such order separation, a plurality of wavelength bands can be measured by one spectrometer.

On the other hand, the "bright high-resolution spectrometer" described in Japanese Patent Application Laid-Open No. 5-133807 satisfies both the requirement for brightness and the requirement for high resolution, and has a weak and narrow spectral wavelength range like Raman spectroscopy. Although a high-resolution device suitable for separating light is described, a complicated optical system is required, and a usable wavelength range is limited.

As described above, in the conventional method, the focusing characteristics of the focusing optical system other than on the optical axis are poor, and a desired spectral resolution cannot be obtained.

Also, "Applied Optics, Vol. 27, No. 3, February 1988 (APPLIED OPT)
ICS, Vol. 27, no. 3, February,
1988) "describes a technique for moving a diffraction grating, a prism, and the like such that a diffracted light beam of a target spectrum is parallel to an optical axis for each observation.

In general, it is difficult to install an optical system so that the dispersion direction of a desired spectrum in a plurality of wavelength bands is on the optical axis over the entire wavelength band. When a prism or a diffraction grating is used for order separation, an angle of view also occurs in the order separation, so that the imaging performance is reduced and the spectral resolution is reduced. Further, since the slit image is distorted, the size of the slit is also limited.

[0010]

The above-mentioned conventional diffraction grating spectrometer has a drawback that the spectral resolution is reduced when spectra in a plurality of wavelength bands are obtained at the same time because the dispersion is large.

In addition, since it has a mechanically movable part, it is not only impossible to measure a phenomenon that changes in a short time,
It has the drawback that there is a problem in operability and maintainability.

An object of the present invention is to simultaneously measure a plurality of wavelength bands with a single optical meter without deteriorating the performance, and to provide reliability, maintainability, and the like without a mechanical drive unit.
An object of the present invention is to provide a diffraction grating spectrometer that improves operability.

[0013]

SUMMARY OF THE INVENTION A diffraction grating spectrometer according to the present invention diffracts a light beam of a measuring light and converts the diffracted light beam into a first light beam .
The light beam is divided into wavelength bands by a converging parabolic cylindrical mirror, and the light beam is condensed for each of the divided light beams using a second condensing parabolic cylindrical mirror, and the order of the collected light beam is separated by a bandpass filter. In this case, the light beams of the plurality of wavelength bands separated by the order are imaged on one focal plane.

An entrance slit through which the measurement light passes; a reflecting mirror for reflecting the measurement light from the entrance slit; a parabolic mirror for converting the measurement light reflected by the reflection mirror into parallel light; A diffraction grating for diffracting the parallel light; a first for dividing the diffracted light from the diffraction grating into light fluxes for each wavelength band
A converging parabolic cylindrical mirror ; a second converging parabolic cylindrical mirror for condensing each of the light beams divided for each of the wavelength bands;
And an optical filter that performs order separation of the light beam reflected by the converging parabolic cylindrical mirror ; and a detector that forms an image of the light beam transmitted through the optical filter.

An incident slit through which the measuring light passes; a reflecting mirror for reflecting the measuring light from the incident slit; a parabolic mirror for converting the measuring light reflected by the reflecting mirror into a parallel light; A first condensing beam for splitting the diffracted light from the diffraction grating into luminous fluxes of different wavelength bands.
And the object plane cylindrical mirror; a second Atsumarihikariho paraboloid cylindrical mirror for each focusing the light beam divided by the wavelength band; the second Atsumarihikariho
A detector on which the light beam reflected by the object-side cylindrical mirror forms an image; a first condensing parabolic cylindrical mirror and a second condensing parabolic cylinder
A prism installed between the light source and a mirror for performing order separation of the light beam divided for each wavelength band.

An entrance slit through which measurement light passes; a reflecting mirror for reflecting the measurement light from the entrance slit; a parabolic mirror for converting the measurement light reflected by the reflection mirror into parallel light; A first condensing beam for splitting the diffracted light from the diffraction grating into luminous fluxes of different wavelength bands.
And the object plane cylindrical mirror; a second Atsumarihikariho paraboloid cylindrical mirror for each focusing the light beam divided by the wavelength band; the second Atsumarihikariho
A detector on which the light beam reflected by the object-side cylindrical mirror forms an image; a first condensing parabolic cylindrical mirror and a second condensing parabolic cylinder
A transmission diffraction grating that is installed between the mirror and a mirror and that performs order separation of the light beam divided for each wavelength band.

[0017] The invention is characterized in that the diffraction grating is an echelle diffraction grating.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the diffraction grating spectrometer of the present invention.

The embodiment shown in FIG. 1 has an incident slit 1, a folding mirror 2 for reflecting the measuring light incident from the incident slit 1, and a collimating parabolic for converting the measuring light reflected by the folding mirror 2 into parallel light. A surface mirror 3, an echelle diffraction grating 4 for receiving and diffracting the parallel light, a condensing parabolic cylindrical mirror 5 for dividing the diffracted light from the echelle diffraction grating 4 into wavelength bands (bands), and each band is divided. A converging parabolic cylindrical mirror 6 for condensing and reflecting light beams, a band-pass filter 11 for performing order separation of a light beam condensed by the converging parabolic cylindrical mirror 6 in a spectral direction and a vertical direction, and And a two-dimensional array detector 7 that forms a light beam.

Next, the operation of the present embodiment will be described in more detail with reference to FIG.

The measuring light incident from the entrance slit 1 is applied to the collimating parabolic mirror 3 by the bending mirror 2, becomes parallel light, and enters the echelle diffraction grating 4.

The diffracted light from the echelle diffraction grating 4 is divided into a band 1 light beam 8, a band 2 light beam 9, and a band 3 light beam 10 for each wavelength band, and the convergent parabolic cylinder set for each light beam. The light is condensed in the spectral direction by the mirror 5, and is further condensed in the vertical direction by the converging parabolic cylindrical mirror 6. Thereafter, light other than the desired order is removed by the bandpass filter 11 for order separation, and an image is formed on the two-dimensional array detector 7. Here, the bandpass filter 11
Indicates an optical filter. Therefore, it is possible to simultaneously form an image of the spectrum of the wavelength band existing in a plurality of orders.

That is, two sets of converging parabolic cylindrical mirrors 5 and 6 are provided for each wavelength band, and the spectrum to be measured in each wavelength band is condensed on the optical axis and imaged at an optimum position. Adjust the position of each cylindrical mirror as much as possible. Also,
The focal direction can be adjusted by adjusting the arrangement of the cylindrical mirrors so that the focal plane of each wavelength band is on the plane of the two-dimensional array detector 7. The converging parabolic cylindrical mirror 5 performs fine adjustment of the focal length in the spectral direction by finely adjusting the installation position, and the converging parabolic cylindrical mirror 6 performs fine adjustment of the installing position to adjust the focal length in the spectral direction. Fine adjustment of the focal length with respect to the vertical direction.

Further, S / S due to light amount loss due to light beam splitting
In order to compensate for the reduction of the N ratio (signal / noise ratio), the two light-collecting parabolic mirrors 5 and 6 are used to change the light-collecting magnification in the spectral direction and the vertical direction. In a general detector, when the same amount of light is incident, a smaller light receiving area can reduce noise. Here, the length of the slit in the direction perpendicular to the spectral direction is longer than that of a normal spectrometer.

Since the longitudinal direction of the slit has no direct relation to the spectral resolution, the focal length is made short so that there is no problem in the performance as a spectrometer even if the imaging performance is somewhat deteriorated as a bright optical system.

The light is condensed in the longitudinal direction of the slit by the converging parabolic cylindrical mirror 6, and the focal length is shortened several times as compared with the converging parabolic cylindrical mirror 5, thereby increasing the reduction ratio and increasing the S / N ratio. Has been improved.

That is, as described above, the luminous flux of the diffracted light from the echelle diffraction grating 4 is divided into the number of observation targets (assuming about three wavelength bands), and after the luminous flux separation, the image forming characteristics are optimized for each luminous flux. As described above, a condensing optical system is provided for each divided light beam. Two sets of parabolic cylindrical mirrors are combined in order to compensate for the light amount loss due to light beam splitting, and the angle of the cylindrical mirror is adjusted so that an image is formed at a desired position of the two-dimensional array sensor.

By dividing a light beam, light in a plurality of wavelength bands is simultaneously decomposed at a high resolution by one optical system, and the S / N ratio (signal / noise ratio) by the light beam division is obtained.
The length of the slit is made longer and the two converging parabolic cylindrical mirrors 5 and 6 having different focal lengths are combined so as not to decrease.

In this embodiment, an echelle diffraction grating spectrometer is used as a diffraction grating, but the present invention is not limited to this. Other diffraction grating spectrometers, such as an echelle diffraction grating spectrometer and a transmission type diffraction grating, are used. Spectrometer applications are also possible. Although an optical bandpass filter is used for cutting the order, the present invention is not limited to this, and a prism or a diffraction grating may be used.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

Referring to FIG. 2, an entrance slit 1, a bending mirror 2 for reflecting the measuring light incident from the entrance slit 1, a collimating parabolic mirror 3 for converting the measuring light reflected by the folding mirror 2 into parallel light, An echelle diffraction grating 4 for receiving and diffracting the parallel light, a convergent parabolic cylindrical mirror 5 for dividing the diffracted light from the echelle diffraction grating 4 into wavelength bands (bands), and collecting the luminous fluxes divided into the respective bands. A condensing parabolic cylindrical mirror 6 for reflecting and reflecting light; a two-dimensional array detector 7 for forming an image of a light beam condensed in a spectral direction and a vertical direction by the condensing parabolic cylindrical mirror 6; Cylindrical mirror 5 and converging parabolic cylindrical mirror 6
And a prism 12 that is disposed between the prisms and separates the order of the light beam.

In FIG. 2, components corresponding to those shown in FIG. 1 are denoted by the same reference numerals or symbols, and description thereof will be omitted.

The difference from the configuration shown in FIG. 1 is that instead of the band-pass filter 11 installed in front of the two-dimensional array detector 7, a prism 12 for order separation is provided by a convergent parabolic cylindrical mirror 5. And a converging parabolic cylindrical mirror 6, and the prism removes light other than the desired order. Since other operations are the same, the description is omitted here.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

Referring to FIG. 3, an entrance slit 1, a bending mirror 2 for reflecting the measuring light incident from the entrance slit 1, a collimating parabolic mirror 3 for converting the measuring light reflected by the folding mirror 2 into parallel light, An echelle diffraction grating 4 for receiving and diffracting the parallel light, a convergent parabolic cylindrical mirror 5 for dividing the diffracted light from the echelle diffraction grating 4 into wavelength bands (bands), and collecting the luminous fluxes divided into the respective bands. A condensing parabolic cylindrical mirror 6 for reflecting and reflecting light; a two-dimensional array detector 7 for forming an image of a light beam condensed in a spectral direction and a vertical direction by the condensing parabolic cylindrical mirror 6; Cylindrical mirror 5 and converging parabolic cylindrical mirror 6
And a transmissive diffraction grating 13 that separates the order of the light beam.

In FIG. 3, components corresponding to those shown in FIG. 1 are denoted by the same reference numerals or symbols, and description thereof is omitted.

The difference from the configuration shown in FIG. 1 is that instead of the band-pass filter 11 installed in front of the two-dimensional array detector 7, a transmission type diffraction grating 13 for order separation is condensed parabolic. Installed between the cylindrical mirror 5 and the converging parabolic cylindrical mirror 6,
Light other than the desired order is removed by the transmission diffraction grating. Since other operations are the same, the description is omitted here.

[0039]

As described above, in the diffraction grating spectrometer of the present invention, two light collecting mirrors having different focal lengths are combined so that the slit is long and the spectral resolution is not deteriorated. In addition, since the S / N ratio does not decrease and the position and direction of the condenser mirror can be adjusted for each divided light beam, a spectral image of each wavelength band can be optimally formed on one focal plane with optimal imaging performance. Since the light is focused at the image position, it is possible to install a focusing mirror so that the imaging characteristics are optimized for each light beam, and to obtain spectra in multiple wavelength bands simultaneously with high spectral resolution. Have.

Further, since there is no mechanical movable part, there is an effect that reliability, operability and maintainability are improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a diffraction grating spectrometer of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incident slit 2 Bending mirror 3 Collimated parabolic mirror 4 Echelle diffraction grating 5, 6 Condensing parabolic cylindrical mirror 7 Two-dimensional array detector 8 Band 1 light flux 9 Band 2 light flux 10 Band 3 light flux 11 Band pass filter 12 Prism 13 Transmission type diffraction grating

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-69637 (JP, A) JP-A-8-193844 (JP, A) JP-A-9-105672 (JP, A) JP-A-7-105 301560 (JP, A) JP-A-6-75550 (JP, A) JP-B-51-13024 (JP, B2) JP-A-6-502483 (JP, A) JP-A-8-509293 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01J 3/00-3/52 G02B 5/18

Claims (5)

(57) [Claims] 1. A light beam of a measurement light is diffracted, and the diffracted light beam is divided into wavelength bands by a first convergent parabolic cylindrical mirror , and a second convergent parabolic cylinder is divided for each of the divided light beams. A diffraction grating spectrometer characterized in that light is condensed using a mirror , the light is converged by a band-pass filter, and the light is converged on a single focal plane to form an image of the light in a plurality of wavelength bands separated on the one focal plane. . 2. An entrance slit through which measurement light passes, and a reflecting mirror that reflects the measurement light from the entrance slit;
A parabolic mirror that converts the measuring light reflected by the reflecting mirror into parallel light; a diffraction grating that diffracts the parallel light; and a first collection that splits the diffracted light from the diffraction grating into light beams of different wavelength bands. light
Parabolic cylindrical mirror and; second Atsumarihikariho paraboloid cylindrical mirror for each focusing the light beam divided by the wavelength band and; the second focusing
A diffraction grating spectrometer, comprising: an optical filter that performs order separation of the light beam reflected by the parabolic cylindrical mirror ; and a detector that forms an image of the light beam transmitted through the optical filter. 3. An entrance slit through which measurement light passes; and a reflecting mirror reflecting the measurement light from the entrance slit;
A parabolic mirror that converts the measurement light reflected by the reflecting mirror into parallel light; a diffraction grating that diffracts the parallel light; and a first collection that splits the diffracted light from the diffraction grating into light fluxes of different wavelength bands. light
Parabolic cylindrical mirror and; second Atsumarihikariho paraboloid cylindrical mirror for each focusing the light beam divided by the wavelength band and, said second focusing
A detector on which the light beam reflected by the parabolic cylindrical mirror forms an image;
The first converging parabolic cylindrical mirror and the second converging parabolic circle
A prism disposed between the column mirror and the prism for performing order separation of the light beam divided for each wavelength band. 4. An entrance slit through which measurement light passes; and a reflecting mirror that reflects the measurement light from the entrance slit;
A parabolic mirror that converts the measurement light reflected by the reflecting mirror into parallel light; a diffraction grating that diffracts the parallel light; and a first collection that splits the diffracted light from the diffraction grating into light fluxes of different wavelength bands. light
Parabolic cylindrical mirror and; second Atsumarihikariho paraboloid cylindrical mirror for each focusing the light beam divided by the wavelength band and, said second focusing
A detector on which the light beam reflected by the parabolic cylindrical mirror forms an image;
The first converging parabolic cylindrical mirror and the second converging parabolic circle
A transmission diffraction grating installed between the column mirror and the light source, the transmission diffraction grating being configured to perform order separation of the light beam divided for each wavelength band. 5. The diffraction grating spectrometer according to claim 2, wherein the diffraction grating is an echelle diffraction grating.