JP2000111407A - Imaging spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pick-up apparatus for picking up images by an imaging spectrometer which is not increased so much in weight or the like and can change a maximum wavelength resolution. SOLUTION: In the imaging spectrometer aboard a space flying object, an optical means for forming images to a detecting system capable of changing a wavelength resolution by a magnification-changing function is provided between a diffraction grating spectrometer 2 for splitting by wavelengths and a detector 4. In the embodiment, an optical path changing mirror 5 is set to a part of an imaging system 3A, which is mechanically stowed and inserted when the wavelength resolution is raised. When the mirror is inserted, the split light is introduced by an imaging system 3B of a different image formation magnification to a detector 4B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus mounted on a spacecraft and using an imaging spectrometer for mapping and imaging observations of the earth and planets in a multi-wavelength band.

[0002]

2. Description of the Related Art In a conventional imaging spectrometer mounted on a spacecraft, it is desired to further increase the amount of information in a wavelength region in order to more accurately analyze an observation target (e.g., vegetation, geology, plankton in the sea area, etc.). There is a demand from data users for more wavelengths and narrower bands. In the case of a polar orbit satellite, the latest development example is to scan one direction of the imaging direction by satellite travel and use a two-dimensional array sensor as a detector. One direction of the two-dimensional array sensor is used for imaging scanning in a direction orthogonal to the satellite travel, and the other direction is used for wavelength scanning.

In this case, a diffraction grating spectrometer is used as a spectral method, and the wavelength scanning direction of this sensor is the wavelength dispersion direction of the diffraction grating. The light dispersed by the diffraction grating is guided to a two-dimensional array sensor by an imaging optical system. The maximum wavelength resolution is defined by the detector pixel size d. The observation wavelength range is defined by the number n of pixels arranged in the detector in the wavelength scanning direction.

[0004] As a prior art document of this type of spectrometer, Japanese Patent Application Laid-Open No. 7-128146 is first mentioned. An outline of the configuration and operation of this example will be described with reference to FIG. In the figure, observation light 8 is condensed on a slit 10 of a spectroscopic unit 60 by a condensing optical system 30 via a scanning mirror 20. The observation light 8 that has passed through the slit 10 is returned to parallel light by the collimating optical system 12 and enters the dispersion element 13 under the control of the control system 40. The observation light 8 split by the dispersive element 13 is imaged on the detector 17 by the imaging optical system 15. In this case, the imaging optical system 15 is adjusted by the control of the control system 40 by the focal length variable mechanism 16 so as to have a focal length corresponding to the slit width of the slit 10.
The observation light 8 imaged on the detector 17 by the imaging optical system 15 is converted into an electric signal by a signal processing system 50 and then subjected to signal processing.

[0005] In addition to the above-mentioned documents, Japanese Patent Application Laid-Open No. Hei 8-50
No. 3300 is known.

[0006]

SUMMARY OF THE INVENTION In the case of an artificial satellite as a space vehicle, it has been quite difficult to change the wavelength resolution after it has been manufactured and launched once. In the case of an imaging spectrometer, as the analysis of an observation target progresses, a change in wavelength resolution or a change in wavelength band is usually requested.

In the case of the conventional method using a diffraction grating and a two-dimensional array, this requirement can be satisfied by changing the combination of the two-dimensional array in which the output in the wavelength scanning direction is electrically synthesized by a command from the ground. Becomes

However, the maximum wavelength resolution is fixed to the detector pixel size once the hardware is launched. By increasing the magnification of the imaging system to the detector and increasing the maximum wavelength resolution as much as possible,
In the case of a semiconductor detector, the maximum number of pixels of the detector has an upper limit due to the limit of the crystal size, and the observation wavelength range is narrowed.

It is sufficient to mount two types of imaging spectrometers having different maximum wavelength resolutions, including a telescope and a spectrometer, but this is not feasible in the case of an artificial satellite which has a strong restriction on the launch weight.

[0010] As described above, the maximum wavelength resolution is fixed to the detector pixel size once the hardware is launched, whereas the imaging spectrometer according to the present invention solves the above problem. In order to solve the above problem, it is possible to change the wavelength resolution by providing a magnification conversion function in an imaging optical system between a diffraction grating for performing wavelength separation and a detector. The purpose of the present invention is
It is an object of the present invention to provide an imaging apparatus using an imaging spectrometer that can change the maximum wavelength resolution without a significant increase in weight or the like.

[0011]

An imaging spectrometer according to the present invention is an imaging spectrometer mounted on a space vehicle for mapping and imaging observations of the earth and planets in a multi-wavelength band. Is introduced by a telescope (1), a diffraction grating spectrometer (2) for wavelength-splitting the light, an imaging system (3) for imaging the spectroscopic observation light, and an imaging system. Between the photoelectric conversion detector (4) for measuring the observed light and the diffraction grating spectrometer (2) and the detector (4). Imaging optical means.

The image forming optical means includes two sets of image forming systems (3A and 3B) having different image forming magnifications and respective detectors (4 and 4).
A, 4B) and an optical path conversion mirror (5) for switching the A system and the B system having different imaging magnifications are preferred embodiments of the present invention.

Further, when the optical path conversion mirror (5) receives the switching signal, it is mechanically inserted into the part of the imaging system (3A), while the imaging system (3B) and the detector (4B) One embodiment is fixedly mounted in advance at a position that is compatible with the optical path conversion mirror.

The present invention also includes an optical path conversion mirror (5) which can be restored to its original position if necessary.

Further, the optical path conversion mirror (5), the imaging system (3A, 3B) and the detector (4B) are arranged in one frame separate from the spectrometer, and move with the frame when switching. It is one embodiment of the present invention that the optical path conversion mirror (5) moves to a predetermined position between the diffraction grating spectrometer (2) and the detector (4A).

The frame provided with the optical path conversion mirror (5), the imaging system (3A, 3B) and the detector (4B) is movable in the direction opposite to the moving direction and is restored to its original state. Is also conceivable.

[0017]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

Light (observation light 8) from an observation object is introduced into a telescope 1 of an imaging spectrometer, and separated by a diffraction grating spectrometer 2. Thereafter, an image is formed on the photoelectric conversion detector 4A by the imaging system 3A. This part is the same as that of the conventional example.

In the first embodiment of the present invention, an optical path conversion mirror 5 which is mechanically stowed and inserted when raising the wavelength resolution is provided in the imaging system 3A. When this is inserted, the split light is introduced into the detector 4B by the imaging systems 3B having different imaging magnifications. In this case, the optical path conversion mirror 5 and the imaging system 3A are provided in the same frame,
The frame is movable in a direction perpendicular to the direction of the light from the spectrometer 2, so that the optical path conversion mirror 5 and the imaging system 3A
Is switched.

In the above case, the imaging system 3B and the detector 4B are fixed in advance at a position suitable for the optical path conversion mirror 5. When changing the target observation wavelength and the wavelength resolution, it is a trial first, so that the restored mirror 5 is restored again, that is, from the B system to the A system.
Make it possible to restore the system. This is achieved by moving the frame on which the optical path conversion mirror 5 and the imaging system 3A are disposed in the forward and reverse directions as described above.

In another second embodiment, in addition to the imaging system 3A and the optical path conversion mirror 5, the imaging system 3B and the detector 4B are arranged on a frame different from the telescope or the spectrometer. When switching from the system to the system B, the frame is moved in the same manner as in the first embodiment, and the optical path conversion mirror 5 is moved to a predetermined position between the diffraction grating spectrometer 2 and the detector 4A. .

Also in this case, the frame can be restored assuming that it can be moved in the reverse direction. If the maximum wavelength resolution of the A system is Δλ = d _A (the pixel size of the detector A), and if the maximum wavelength resolution of the B system is k times, 1
The imaging system may be designed so that / k · Δλ = d _B (pixel size of the detector B).

If the number of detector pixels is the same for A / B, the amount of downlink data does not change, but in the B system, the observation wavelength range is 1 / k.

[0024]

As described above, according to the present invention, the magnification of the image forming optical system between the diffraction grating for spectral separation and the detector is provided with magnification conversion means, so that the pixel size of the detector is fixed even after launch. There is an effect that the maximum wavelength resolution can be changed without any problem. This also has the effect that the observation wavelength range does not need to be narrowed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging spectrometer according to the present invention that enables a change in wavelength resolution.

FIG. 2 is a schematic diagram showing a configuration of a conventional spectrometer that variably controls wavenumber resolution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Telescope 2 Diffraction grating spectrometer 3, 3A, 3B Imaging system 4, 4A, 4B Detector 5 Optical path conversion mirror 8 Observation light 20 Scanning mirror 30 Condensing system 40 Control system 50 Signal processing system 60 Spectroscopic section

Claims (6)

[Claims] 1. A telescope (1) into which light from an observation target is introduced, and a diffraction grating spectrometer (2) for wavelength-spectroscopy of the light.
And an imaging system (3) for forming an image of the spectroscopic observation light and a photoelectric conversion detector (4) for measuring the observation light formed by the imaging system. 3. The imaging spectrometer according to claim 1, further comprising an imaging optical unit between the diffraction grating spectrometer (2) and the detector (4), the imaging system being capable of changing a maximum wavelength resolution by a magnification conversion function. 2. The image forming optical means comprises two sets of image forming systems (3A, 3B) having different image forming magnifications, and respective detectors (4A, 3B).
The imaging spectrometer according to claim 1, further comprising 4B) and an optical path conversion mirror (5) for switching between the A system and the B system having different imaging magnifications. 3. When the optical path conversion mirror (5) receives a switching signal, the optical path conversion mirror (5) is mechanically inserted into the imaging system (3A), and the imaging system (3B) and the detector (4B) perform optical path conversion. 3. An imaging spectrometer according to claim 1, wherein the imaging spectrometer is fixedly mounted in advance at a position suitable for the mirror. 4. The imaging spectrometer according to claim 1, wherein the optical path conversion mirror can be restored to its original position as required. 5. The optical path conversion mirror (5), an imaging system (3)
A, 3B) and the detector (4B) are arranged in a frame separate from the spectrometer, and when switching, the frame moves and the position of the optical path conversion mirror (5) is changed to the diffraction grating spectrometer (2) and the detector ( The imaging spectrometer according to claim 1 or 2, wherein the imaging spectrometer moves to a predetermined position during 4A). 6. The optical path conversion mirror (5), an image forming system (3)
The imaging spectrometer according to claim 1, 2 or 5, wherein the frame provided with the detectors (A, 3B) and the detector (4B) is movable in a direction opposite to the direction and is restored to the original direction.