JPH09113797A - Optical device for infrared ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of the incidence of unnecessary infrared rays on an image by making the exit pupil of a composite optical system of an object optical system and an image re-forming optical system meet the cold aperture of a sensor means for infrared rays. SOLUTION: The objective optical system 1 is an optical system which is telecentric (having its exit pupil at the infinite distance) to an image side. The imaging optical system 5, on the other hand, is telecentric (having its entrance and exit pupils at the infinite distance) to an object side and its exit pupil meets the position of the cold aperture 8. Then the objective optical system 1 and imaging optical system 5 are connected while being made eccentric with each other so that the center of a linear image (intermediate image 4) inscribed in a ring field formed by the objective optical system 1 is aligned with the optical axis of the imaging optical system 5. Thus, the exit pupil of the composite optical system of the objective optical system 1 and imaging optical system 5 meets the position of the cold aperture 8 and the composite optical system is what is called an aperture matching type optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared optical device, and more particularly to an infrared optical device that obtains an infrared image by scanning using a one-dimensional line sensor sensitive to infrared light.

[0002]

2. Description of the Related Art FIG. 5 is a diagram schematically showing a configuration of a conventional infrared optical device for obtaining an infrared image of a distant target object. In FIG. 5, a distant target object (not shown)
The emitted light from the first reflecting mirror 15 and the second reflecting mirror 16
Are sequentially reflected by and form an intermediate image 4. Thus, the first reflecting mirror 15 and the second reflecting mirror 16 form a coaxial objective optical system. The light from the intermediate image 4 is re-imaged on the detection elements 17 arranged two-dimensionally via the imaging optical system 5.

The inside of the dewar 6 having the built-in detection element 17 is evacuated and cooled by a container 10 filled with a refrigerant. The cold shield 11 is provided so that the detection element 17 receives as little light as possible emitted from other than the target object. That is, the detection element 17
A cold aperture 8 for taking in radiated light from a target object is provided in front of. The exit pupil of the combined optical system of the objective optical system and the imaging optical system 5 must match the cold aperture 8 (in order to achieve aperture matching) in order to capture as little radiation as possible from other than the target object. is there. Optical systems for infrared rays are often designed to be aperture-matched, and the optical device shown in FIG. 5 is also aperture-matched.

[0004]

Although the conventional infrared optical device shown in FIG. 5 has an aperture-matching type optical system, it receives light emitted from other than the target object to some extent. On the other hand, since the infrared optical device of FIG. 5 uses a coaxial Cassegrain type objective optical system, an intermediate image is formed using a circular light beam centered on the optical axis, but the second part is formed near the center of the light beam. It is blocked by the reflecting mirror 16. As a result, there is an inconvenience that the mixing of unnecessary infrared rays in the vicinity of the center of the light flux causes an increase in detection noise and the S / N of the obtained image is deteriorated.

In the case where a microscope structure is used in which an intermediate image is formed by using a Schwarzschild type objective optical system and the light from the intermediate image is re-imaged by the imaging optical system, similarly, the vicinity of the center of the light beam is Blocked. Therefore, there is a disadvantage that the S / N of the image is deteriorated due to the mixing of unnecessary infrared rays in the vicinity of the center of the light flux. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an infrared optical device in which the influence of mixing of unnecessary infrared rays on the S / N of an image is small.

[0006]

In order to solve the above-mentioned problems, in the present invention, an objective optical system for forming an intermediate image of the object based on light emitted from the object, and the objective optical system are provided. A re-imaging optical system for re-forming the image of the object based on the light from the intermediate image formed via the re-imaging optical system, and detecting the image of the object re-formed via the re-imaging optical system. Infrared optical device including infrared sensor means for controlling the object, the objective optical system is an optical system telecentric to the image side, and the re-imaging optical system is a coaxial optical system telecentric to the object side. The objective optical system and the re-imaging optical system are arranged so as to be decentered from each other, and the exit pupil of the combined optical system of the objective optical system and the re-imaging optical system is the cold aperture of the infrared sensor means. Characterized by matching To provide an infrared optical apparatus.

According to a preferred aspect of the present invention, the objective optical system forms a good image of the object in an annular field centered on the optical axis of the objective optical system based on the off-axis light beam from the object. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the present invention, the objective optical system is telecentric on the image side and the re-imaging optical system is telecentric on the object side. Also,
The objective optical system and the re-imaging optical system are eccentrically connected to each other, and the exit pupil of the synthetic optical system coincides with the cold aperture of the infrared sensor means. As described above, since the infrared optical device of the present invention has the aperture-matching type configuration in which it is difficult to capture the radiation light from other than the target object, the mixing of unnecessary infrared light is small.

Further, according to the present invention, for example, in an annular field of the objective optical system, that is, an off-axis field, an image with less astigmatism is formed by using only the off-axis light beam without using the on-axis light beam from the object. . That is, in the present invention, since the center of the light flux is not shielded, the influence of mixing of unnecessary infrared rays on the S / N of the infrared image is small. In the present invention, telecentricity and aperture matching are allowed in the aberration amount range where the re-formed image is not blurred. That is, the present invention includes not only the completely telecentric case but also the almost telecentric case. Similarly, with respect to aperture matching, the present invention also includes a state in which the exit pupil of the synthetic optical system substantially matches the cold aperture of the infrared sensor means.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of an infrared optical device according to a first embodiment of the present invention. In the optical device of FIG. 1, the emitted light from a distant target object (not shown) forms an intermediate image 4 in the annular field of the objective optical system (represented by one refracting optical system in the figure) 1. . Objective optical system 1
Is an optical system that is telecentric on the image side (exit pupil is infinity), and is, for example, a coaxial reflecting optical system that includes a plurality of reflecting mirrors.

The objective optical system 1 forms a one-dimensional good image with little astigmatism as an intermediate image 4 in an annular field distant from the optical axis based on the off-axis light beam from the target object. The light from the intermediate image 4 is re-imaged on the infrared detecting element 7 via the imaging optical system 5 (represented by one lens component in the figure) which is a re-imaging optical system. The detecting element 7 is disposed inside the dewar 6, and a dewar window 9 that transmits infrared rays is formed on the object side surface of the dewar 6. The inside of the Dewar 6 is pulled to a substantially vacuum, and is cooled by a container 10 filled with a refrigerant such as liquid nitrogen.

A cold shield 11 is provided inside the dewar 6 so that the detection element 7 receives as little light as possible emitted from other than the target object. That is, between the detection element 7 and the dewar window 9, the cold aperture 8 for taking in the emitted light from the target object is provided. As described above, the Dewar 6, the detection element 7, the cold aperture 8, the Dewar window 9, and the container 10 constitute infrared sensor means for detecting the object image reformed through the imaging optical system 5. .

As described above, the objective optical system 1 is an optical system that is telecentric (exit pupil is infinity) on the image side.
On the other hand, the imaging optical system 5 is telecentric on the object side (the entrance pupil is at infinity), and its exit pupil coincides with the position of the cold aperture 8. Then, the objective optical system 1
And the imaging optical system 5 are a one-dimensional image (intermediate image 4) inscribed in the annular field formed by the objective optical system 1.
Are eccentrically connected to each other so that the center of the image and the optical axis of the imaging optical system 5 coincide with each other.

Thus, the exit pupil of the combined optical system of the objective optical system 1 and the imaging optical system 5 has a cold aperture 8
Coincident with the position of, the synthetic optical system is a so-called aperture matching type optical system. In the device of FIG. 1, a two-dimensional infrared image of a distant target object can be obtained by relatively scanning the device and the target object along a predetermined direction. The objective optical system 1, the imaging optical system 5, the Dewar window 9 and the like have low emissivity, and the synthetic optical system is a so-called aperture matching type optical system. Therefore, the amount of unnecessary infrared rays received by the detection element 7 is small.

Further, as described above, the objective optical system 1 is
Based on the off-axis light flux from the target object, a one-dimensional good image with little astigmatism is formed as the intermediate image 4 in the annular field away from the optical axis. Therefore, the objective optical system 1 of FIG.
In the above, there is no shielding with respect to the center of the light flux unlike the Cassegrain objective optical system (see FIG. 5) that forms an intermediate image using the on-axis light flux from the target object. Therefore, in the infrared optical device of the first embodiment, it is possible to suppress the influence of the mixing of unnecessary infrared rays on the S / N of the infrared image and obtain a good infrared image.

FIG. 2 is a diagram schematically showing the structure of an infrared optical device according to the second embodiment of the present invention. The apparatus of the first embodiment obtains an image of a distant target object, while the apparatus of the second embodiment is designed to obtain an image of a target object at a short distance. In terms of configuration, the configuration of the objective optical system is different between the first embodiment and the second embodiment, and the configuration of the imaging optical system and the infrared sensor means are the same. Therefore, in FIG.
Elements having basically the same functions as those of the constituent elements are designated by the same reference numerals. Hereinafter, the second embodiment will be described by focusing on the differences from the first embodiment.

In the optical device of FIG. 2, the emitted light from the target object 12 at a short distance is, for example, at the same magnification in the annular field of the objective optical system (represented by one refracting optical system in the figure) 2. To form an intermediate image 4. Similar to the first embodiment, the objective optical system 2 is an optical system telecentric to the image side,
For example, a coaxial reflection optical system including a plurality of reflecting mirrors. The light from the intermediate image 4 is re-imaged on the infrared detecting element 7 via the imaging optical system 5. The structure of the infrared sensor means is the same as that of the first embodiment.

As described above, the objective optical system 2 is an optical system telecentric on the image side. On the other hand, similarly to the first embodiment, the imaging optical system 5 is telecentric on the object side, and its exit pupil coincides with the position of the cold aperture 8. Then, in the objective optical system 2 and the imaging optical system 5, the center of the one-dimensional image (intermediate image 4) inscribed in the annular field formed by the objective optical system 2 and the optical axis of the imaging optical system 5 coincide with each other. So that they are eccentrically connected to each other.

Thus, also in the second embodiment, the exit pupil of the combined optical system of the objective optical system 2 and the imaging optical system 5 coincides with the position of the cold aperture 8 and the combined optical system is a so-called aperture matching type optical system. Has become. Further, also in the second example, the objective optical system 2 sets the one-dimensional good image with less astigmatism as the intermediate image 4 in the annular field away from the optical axis based on the off-axis light beam from the target object. Form. That is, the objective optical system 2 in FIG. 2 does not have a shield for the center of the light flux, and it is possible to suppress the influence of mixing of unnecessary infrared rays on the S / N of the infrared image and obtain a good infrared image.

FIG. 3 is a schematic view showing the arrangement of an infrared optical device according to the third embodiment of the present invention. The apparatus of the third embodiment is a modification of the apparatus of the first embodiment, and has the points having imaging optical systems 5a and 5b having different magnifications, and the optical path of the light beam from the objective optical system 1 is switched to perform the imaging optical system. It is basically different from the first embodiment only in that it has an optical path switching means leading to 5a or 5b. Therefore, in FIG. 3, elements having basically the same functions as those of the constituent elements of FIG. 1 are designated by the same reference numerals. Hereinafter, the third embodiment will be described by focusing on the differences from the first embodiment.

In the optical device of FIG. 3, the light emitted from a distant target object forms an intermediate image 4 in the annular field of the objective optical system 1. A mirror 18 is provided so that it can be inserted into and removed from the convergent optical path through the objective optical system 1. Therefore, when the mirror 18 is out of the convergent optical path as shown by the solid line in the figure, the first intermediate image 4a is formed by the light flux that has proceeded straight. On the other hand, when the mirror 18 is inserted in the convergent optical path as shown by the broken line in the figure, the second intermediate image 4b is formed by the light flux bent by the mirror 18.

The light from the first intermediate image 4a is re-imaged on the first detecting element 7a via the first imaging optical system 5a. On the other hand, the light from the second intermediate image 4b is re-imaged on the second detection element 7b via the second imaging optical system 5b having a magnification different from that of the first imaging optical system 5a. Thus, the mirror 18 constitutes an optical path switching means for switching the optical path of the light flux passing through the objective optical system 1 and guiding it to the first imaging optical system 5a or the second imaging optical system 5b.

As described above, in the third embodiment, two kinds of infrared images having different magnifications can be selectively obtained by the optical path switching action of the mirror 18. When the first detection element 7a and the second detection element 7b have sensitivities to different wavelength bands, each imaging optical system may be configured using a material suitable for each wavelength band.

FIG. 4 is a diagram schematically showing the configuration of an infrared optical device according to the fourth embodiment of the present invention. The apparatus according to the fourth embodiment is another modification of the apparatus according to the first embodiment, in which a point having imaging optical systems 5a and 5b different in magnification from each other and a light beam from the objective optical system 1 are split and imaged. It is basically different from the first embodiment only in that it has a light splitting means for guiding the optical systems 5a and 5b. Therefore, in FIG. 4, elements having basically the same functions as those of the constituent elements in FIG. 1 are designated by the same reference numerals. Hereinafter, the fourth embodiment will be described focusing on the differences from the first embodiment.

In the optical arrangement of FIG. 4, the light emitted from a distant target object forms an intermediate image 4 in the annular field of the objective optical system 1. A half mirror 19 and a correction plate 20 for correcting the aberration generated by the half mirror 19 are provided in the convergent optical path through the objective optical system 1. Therefore, the half mirror 19 and the correction plate 20
The light transmitted through forms a first intermediate image 4a, and the light reflected by the half mirror 19 forms a second intermediate image 4b.

The light from the first intermediate image 4a is re-imaged on the first detecting element 7a via the first imaging optical system 5a. On the other hand, the light from the second intermediate image 4b is re-imaged on the second detection element 7b via the second imaging optical system 5b having a magnification different from that of the first imaging optical system 5a. In this way, the half mirror 19 constitutes a light splitting means for splitting the light flux that has passed through the objective optical system 1 and guiding it to the first imaging optical system 5a and the second imaging optical system 5b.

Thus, in the fourth embodiment, the two types of infrared images having different magnifications can be simultaneously obtained by the light splitting action of the half mirror 19. When the first detection element 7a and the second detection element 7b have sensitivities to different wavelength bands, each imaging optical system is configured using a material suitable for each wavelength band, and a half mirror is used. Instead of 19, a spectral means such as a dichroic mirror may be used.

In the third and fourth embodiments described above, the apparatus provided with two sets of imaging optical systems and sensor means has been described, but the apparatus provided with three or more sets of imaging optical systems and sensor means. It is obvious that the present invention can also be applied to. Further, in the above-described third and fourth embodiments, an apparatus including two sets of imaging optical system and sensor means has been described as a modification of the first embodiment, but the same applies to the second embodiment. It is possible to provide a modified example in which two or more sets of imaging optical system and sensor means are provided. Furthermore, by appropriately selecting the configuration of the objective optical system, the present invention can be applied to a telescope and a microscope.

[0029]

As described above, according to the present invention, the objective optical system and the imaging optical system that are not shielded with respect to the center of the light beam are decentered and connected to form an aperture-matching type synthetic optical system. Therefore, it is possible to significantly suppress the influence of the mixing of unnecessary infrared rays on the S / N of the infrared image.
Also, a plurality of imaging optical systems and optical path switching means,
By combining with the light splitting means or the spectroscopic means, images with different magnifications or different wavelength bands can be obtained alternatively or simultaneously.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of an infrared optical device according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of an infrared optical device according to a second embodiment of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an infrared optical device according to a third embodiment of the present invention.

FIG. 4 is a diagram schematically showing a configuration of an infrared optical device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram schematically showing a configuration of a conventional infrared optical device for obtaining an infrared image of a distant target object.

[Explanation of symbols]

 1, 2 Objective optical system 4 Intermediate image 5 Imaging optical system 6 Dewar 7 Detection element 8 Cold aperture 9 Dewar window 10 Container 11 Cold shield 18 Mirror 19 Half mirror 20 Correction plate

Claims (10)

[Claims] 1. An objective optical system for forming an intermediate image of the object based on light emitted from the object, and an object optical system for the object based on light from the intermediate image formed via the objective optical system. In an infrared optical device comprising a re-imaging optical system for re-forming an image, and infrared sensor means for detecting an image of the object re-formed via the re-imaging optical system, The objective optical system is an optical system telecentric on the image side, the re-imaging optical system is a coaxial optical system telecentric on the object side, and the objective optical system and the re-imaging optical system are mutually An infrared optical device, which is eccentrically arranged, wherein an exit pupil of a combined optical system of the objective optical system and the re-imaging optical system is coincident with a cold aperture of the infrared sensor means. 2. The objective optical system forms a good image of an object in an annular field centered on an optical axis of the objective optical system based on an off-axis light beam from the object. 1. The infrared optical device according to 1. 3. The re-imaging optical system includes a first re-imaging optical system and a second re-imaging optical system having different magnifications, and switching an optical path of a light beam through the objective optical system. 3. The infrared optical device according to claim 1, further comprising optical path switching means for guiding the light beam to the first re-imaging optical system or the second re-imaging optical system. 4. The re-imaging optical system includes a first re-imaging optical system that transmits a light beam in a first wavelength band and a second re-imaging optical system that transmits a light beam in a second wavelength band different from the first wavelength band. And an optical path switching means for switching the optical path of the light flux through the objective optical system and guiding it to the first re-imaging optical system or the second re-imaging optical system. The infrared optical device according to claim 1 or 2, characterized in that: 5. The infrared optical device according to claim 3, wherein the optical path switching means is a mirror that can be inserted into and removed from the optical path of a light beam passing through the objective optical system. 6. The re-imaging optical system includes a first re-imaging optical system and a second re-imaging optical system having different magnifications, and splits a light beam passing through the objective optical system to obtain the re-imaging optical system. The infrared optical device according to claim 1 or 2, further comprising a light splitting means for guiding the light beam to the first re-imaging optical system and the second re-imaging optical system. 7. The infrared optical device according to claim 6, wherein the light splitting means is a half mirror provided in an optical path of a light beam passing through the objective optical system. 8. The re-imaging optical system includes a first re-imaging optical system that transmits a light beam in a first wavelength band and a second re-imaging optical system that transmits a light beam in a second wavelength band different from the first wavelength band. An image-forming optical system, wherein the light flux passing through the objective optical system is dispersed, and the first re-imaging optical system receives the light beam in the first wavelength band and the second re-imaging optical system receives the light beam. The infrared optical device according to claim 1 or 2, further comprising a spectroscopic unit for guiding each of the light fluxes in the second wavelength band. 9. The infrared optical device according to claim 8, wherein the first re-imaging optical system and the second re-imaging optical system have different magnifications. 10. The infrared optical device according to claim 8, wherein the spectroscopic unit is a dichroic mirror provided in an optical path of a light beam passing through the objective optical system.