CN209878593U - A Long Wave Infrared Doppler Differential Interferometer - Google Patents

Abstract

The utility model belongs to the field of fine spectrum detection, in particular to a long-wave infrared Doppler differential interferometer. The long-wave infrared Doppler differential interferometer is sequentially provided with a front lens, an interferometer, a fringe imaging lens and a detector along the optical path; A light sheet, a field stop and a second front lens, the first aperture stop is located on the first surface of the front lens; the fringe imaging lens is sequentially arranged on the same optical axis along the optical path as the first imaging lens, the second imaging lens and the second imaging lens Three imaging lenses; after the parallel light passes through the front lens, interferometer, and fringe imaging lens in sequence, interference fringes are formed on the focal plane of the detector. The long-wave infrared Doppler differential interferometer can be used to detect the atmospheric wind field and ozone concentration in the 24-60 km stratosphere.

Description

A Long Wave Infrared Doppler Differential Interferometer

technical field

The utility model belongs to the field of fine spectrum detection, in particular to an optical system of a long-wave infrared Doppler differential interferometer.

Background technique

Traditional atmospheric wind field detection technologies mainly include Fabry-Perot interferometric wind field detection technology and wide-angle Michelson interferometer wind field detection technology. The former has high resolution and high sensitivity, but requires very high processing and adjustment accuracy; The latter requires an optical path difference scanning device and can only detect one spectral line at a time. Doppler differential interferometry is a new type of fine spectral detection technology, which has the advantages of high spectral resolution, high throughput, and high stability. The target source of the traditional atmospheric wind field detection method is the upper atmospheric airglow located in the visible light band of 80-300 km, and in the stratosphere of 24-60 km, it is necessary to select a weaker infrared thermal radiation source as the target source of wind field detection , so the Doppler differential interferometry technique is used for detection.

The study found that the ozone spectral line near 8.8 μm in the long-wave infrared band has high spectral intensity and good separation, which can be used as the target spectral line. According to the Doppler effect, the atmospheric wind field will shift the center frequency of the spectral line obtained by the interferometer, and the shift amount has a quantitative relationship with the velocity of the atmospheric motion. Therefore, the velocity of the stratospheric atmosphere can be calculated by inversion of the Doppler frequency shift of the ozone spectral line. At the same time, the ozone concentration of the atmosphere at this altitude can also be obtained through data inversion.

Utility model content

The utility model provides an optical system of a long-wave infrared Doppler differential interferometer to realize the detection of a 24-60 km stratosphere atmospheric wind field and ozone concentration.

In order to achieve the above objectives, the utility model provides a long-wave infrared Doppler differential interferometer, which is special in that: a front lens, an interferometer, a fringe imaging lens and a detector are sequentially arranged along the optical path;

The above-mentioned front lens is provided with a first aperture stop, a first front lens, an optical filter, a field stop and a second front lens along the optical path in sequence on the optical axis, and the first aperture stop is located at the first of the front lens. surface, the field diaphragm is located between the filter and the second front lens;

The above-mentioned interferometer includes a beam splitter plate, a compensation plate, a first field of view widening prism, a second field of view widening prism, a first grating and a second grating; the first field of view widening prism and the first grating form a first optical unit, and the first field of view widening prism and the first grating form a first optical unit. The second optical unit is formed by the two-field widening prism and the second grating, the beam splitter and the compensation plate are placed in parallel to form the beam splitter, and the first optical unit and the second optical unit are respectively located in the two outgoing light paths of the beam splitter;

The stripe imaging lens is provided with a first imaging lens, a second imaging lens and a third imaging lens on the same optical axis in sequence along the optical path;

After the parallel light passes through the front lens, the radiation intensity information of the target spectral line is extracted by using a filter; after the light is split by the interferometer, the two-arm light forms a Fizeau-type interference fringe at the exit of the interferometer; after passing through the fringe imaging lens, the interferometer exits The interference fringes at are imaged at the detector focal plane.

Further, the first front lens is a biconvex positive lens, the second front lens is a meniscus positive lens, and the focal power of the optical filter is zero.

Further, the materials of the first front lens, the second front lens and the filter are germanium;

The distance between the first aperture stop and the first front lens is 13.5±0.2mm, the distance between the first front lens and the filter is 12.7±0.2mm, and the distance between the filter and the field stop is 6±0.0mm 0.2mm, the distance between the field diaphragm and the second front lens is 60.8±0.2mm.

Further, the central wavelength of the above-mentioned optical filter is 8781.5 nm, and the FWHM of the optical filter is 127 nm.

Further, the beam splitter plate and the compensation plate in the above-mentioned interferometer are zinc selenide glass plates, the first field of view widening prism and the second field of view widening prism are the same prisms whose front and rear surfaces form a certain angle, and the material is zinc selenide, The first grating and the second grating have the same groove density of 150 lines/mm and a blaze angle of 41.588°.

Further, in the above-mentioned stripe imaging lens, the first imaging lens is a biconvex positive lens, the second imaging lens is a meniscus negative lens, and the third imaging lens is a meniscus positive lens; the above-mentioned stripe imaging lens also includes a second aperture stop, The above-mentioned second aperture stop is placed at the cold screen of the detector.

Further, the materials of the first imaging lens, the second imaging lens and the third imaging lens are germanium;

The distance between the first imaging lens and the second imaging lens is 33.5±0.03mm, the distance between the second imaging lens and the third imaging lens is 41.8±0.03mm, and the distance between the third imaging lens and the detector window is 20±0.03mm .

Further, the above-mentioned front lens is a Kepler-type afocal system, which ensures that the entire grating is illuminated; the above-mentioned fringe imaging lens has an F/# of 2 and a magnification of β=-0.28.

Further, the distance between the above-mentioned front lens and the beam splitter plate is 60±0.2mm, the distance between the compensation plate and the fringe imaging lens is adjustable, and at normal temperature and pressure, the distance between the compensation plate and the fringe imaging lens is 60±0.2mm .

Further, the above-mentioned detector is a scientific grade CCD camera with a spectral range of 8-10 μm, a pixel size of 30 μm, an array size of 320×256, and an operating temperature of -40°C to +71°C.

Compared with the prior art, the beneficial effects of the utility model are:

1. The utility model realizes the application of the split Doppler differential interferometer in the long-wave infrared band. Through the design of the front lens, interferometer and fringe imaging lens, the simulated interference fringes obtained by the interferometer system in the working band have The higher modulation degree can meet the accuracy requirements of 24-60km atmospheric wind speed retrieval and ozone concentration retrieval.

2. The utility model adopts a complete matching method to carry out cold screen matching on the cooling type detector, that is, the aperture diaphragm of the fringe imaging lens is placed at the cold screen of the detector, and the telecentricity of the object side of the imaging lens is ensured, thereby effectively improving the image plane. The relative illuminance at the position keeps the illuminance of the image plane uniform.

3. The utility model uses the mechanical active thermal compensation method to carry out an athermal design for the streak imaging lens, and ensures normal temperature and pressure (20°C, 1atm) and low temperature vacuum (160K, 0atm) by adjusting the distance between the lens and the detector window The imaging quality in the two environments enables the interferometer system to be assembled at normal temperature and pressure and work in a low-temperature vacuum environment, thereby reducing the impact of the thermal radiation of the optical-mechanical structure itself on the detection sensitivity.

Description of drawings

Fig. 1 is the schematic diagram of the optical path structure of the long-wave infrared Doppler differential interferometer in the embodiment;

Reference signs in the figure are: 1-front lens; 101-first aperture stop, 102-first front lens, 103-filter, 104-field diaphragm, 105-second front lens;

2-interferometer; 201-first grating, 202-first field of view widening prism, 203-beam splitter, 204-compensation plate, 205-second field of view widening prism, 206-second grating;

3—stripe imaging lens; 301—first imaging lens, 302—second imaging lens, 303—third imaging lens.

Fig. 2 is the optical structure diagram of the fringe imaging lens;

The reference signs in the figure are: 304-second aperture stop, 305-cold screen;

Figure 3a is a spot diagram of the streak imaging lens at normal temperature and pressure (20°C, 1atm);

Figure 3b is the MTF curve of the streak imaging lens at normal temperature and pressure (20°C, 1atm);

Figure 4a is a spot diagram of the system after the stripe imaging lens has been focused under low-temperature vacuum (0°C, 0atm);

Figure 4b is the MTF curve of the system after the fringe imaging lens is focused under low temperature vacuum (0°C, 0atm);

Fig. 5a is the interferogram under normal temperature and pressure (20°C, 1 atm) obtained by simulation of the optical system of the long-wave infrared Doppler differential interferometer;

Figure 5b is the interferogram under low temperature vacuum (0°C, 0atm) conditions obtained by simulation of the optical system of the long-wave infrared Doppler differential interferometer;

Figure 6a is the calculation of the interference fringe modulation obtained by the interferometer at normal temperature and pressure (20°C, 1 atm);

Fig. 6b is the calculation of the interference fringe modulation obtained by the interferometer under the condition of low temperature vacuum (0°C, 0atm).

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail.

This embodiment provides an optical system of a long-wave infrared Doppler differential interferometer, including a front lens 1 , an interferometer 2 , a fringe imaging lens 3 and a detector (not shown). The detector can use a scientific grade CCD camera with a spectral range of 8-10 μm, a pixel size of 30 μm, an array size of 320×256, and an operating temperature of -40°C to +71°C.

Referring to FIG. 1 , the front lens 1 in this embodiment includes a first aperture stop 101 , a first front lens 102 , a filter 103 , a field stop 104 and a second front lens 105 . Wherein the first aperture stop 101 is located on the first surface of the front lens 1, the first front lens 102 is a biconvex positive lens, the second front lens 105 is a meniscus positive lens, and the material is germanium, and the optical filter The central wavelength of 103 is 8781.5 nm, the bandwidth FWHM of the filter 103 is 127 nm, and the field stop 104 is located between the filter 103 and the second front lens 105 .

The interferometer 2 includes a first grating 201 , a first field-of-view widening prism 202 , a beam splitter 203 , a compensation plate 204 , a second field-of-view widening prism 205 and a second grating 206 . Wherein the beam splitter 203 and the compensation plate 204 are zinc selenide glass plates, the first field of view widening prism 202 and the second field of view widening prism 205 are prisms with the same front and rear surfaces at a certain angle, and the material is zinc selenide, the first The grating 201 and the second grating 206 have the same groove density of 150 lines/mm and a blaze angle of 41.588°.

The stripe imaging lens 3 includes a first imaging lens 301 , a second imaging lens 302 and a third imaging lens 303 . The first imaging lens 301 is a biconvex positive lens, the second imaging lens 302 is a meniscus negative lens, and the third imaging lens is a meniscus positive lens, all of which are germanium.

After the parallel rays from infinity pass through the front lens, the radiation intensity information of the target spectral line is extracted by using the filter 103; Finally, the interference fringes at the exit of the interferometer are imaged on the focal plane of the detector. Atmospheric wind speed and ozone concentration information can be obtained through data inversion of interference fringes.

The specific structural parameters of the long-wave infrared Doppler differential interferometer in this embodiment are detailed in the table below.

The optical system of the long-wave infrared Doppler differential interferometer in this embodiment has an F/# of 2, a half field angle of 13.5°, and an image plane size of 9.6mm×7.68mm.

Referring to Figure 2, the fringe imaging lens adopts a complete matching method for cold screen matching, and the second aperture diaphragm is placed at the detector cold screen to reduce system stray radiation and improve detection sensitivity.

Referring to Figure 3a and Figure 3b, the spot diagram of the fringe imaging lens at normal temperature and pressure (20°C, 1atm) reflects the size of the diffuse spot imaged by the system on the image plane, and the RMS radii of the on-axis and off-axis fields of view both meet the design requirements. Requirements: At the Nyquist frequency of the system at 16.7lp/mm, the MTF curve of the system is close to the diffraction limit, which meets the image quality requirements.

Referring to Fig. 4a and Fig. 4b, the spot diagram and MTF curve of the fringe imaging lens under cryogenic vacuum (160K, 0atm) show that the imaging quality of the system after focusing is good under the cryogenic vacuum environment.

Referring to Fig. 5a and Fig. 5b, the whole system simulation of the long-wave infrared Doppler differential interferometer obtains the interference fringes under normal temperature and pressure and low temperature vacuum conditions.

Referring to Fig. 6a and Fig. 6b, from the interference fringes in Fig. 4a and Fig. 4b, the fringe modulation degree under two conditions of normal temperature and pressure and low temperature vacuum can be calculated, both of which are above 0.99.

In summary, the utility model realizes the construction of the entire optical system of the long-wave infrared Doppler differential interferometer through the optical design of the front lens, interferometer, and fringe imaging lens, and the modulation degree of interference fringes under working conditions obtained by simulation can be It meets the accuracy requirements of data inversion and provides a computational simulation model for the subsequent inversion of atmospheric wind speed and ozone concentration.

The above is only a description of the preferred implementation of the utility model, and does not limit the technical solution of the utility model thereto. Any known deformation made by those skilled in the art on the basis of the main technical concept of the utility model belongs to this utility model. The technical category to be protected by the utility model.

Claims (10)

1. A long-wave infrared Doppler differential interferometer, characterized in that: a front lens (1), an interferometer (2), a fringe imaging lens (3) and a detector are arranged successively along the optical path; The front lens (1) is provided with a first aperture stop (101), a first front lens (102), an optical filter (103), a field stop (104) and a second The front lens (105), the first aperture stop (101) is located on the first surface of the front lens (1); The interferometer (2) includes a beam splitter plate (203), a compensation plate (204), a first field of view widening prism (202), a second field of view widening prism (205), a first grating (201) and a second Grating (206); the first field of view widening prism (202) and the first grating (201) form the first optical unit, the second field of view widening prism (205) and the second grating (206) form the second optical unit, respectively The beam plate (203) and the compensation plate (204) are placed in parallel to form a beam splitting unit, and the first optical unit and the second optical unit are respectively located in the two outgoing light paths of the beam splitting unit; The stripe imaging lens (3) is sequentially arranged with a first imaging lens (301), a second imaging lens (302) and a third imaging lens (303) on the same optical axis along the optical path; After parallel light rays pass through the front lens, interferometer, and fringe imaging lens in sequence, interference fringes are formed on the focal plane of the detector. 2. The long-wave infrared Doppler differential interferometer according to claim 1, characterized in that: the first front lens (102) is a biconvex positive lens, and the second front lens (105) is a concave surface. The meniscus positive lens of the field stop (104), the focal power of the optical filter (103) is zero. 3. long-wave infrared Doppler differential interferometer according to claim 2, is characterized in that: the material of the first front lens (102), the second front lens (105) and optical filter (103) is germanium; The interval between the above-mentioned first aperture stop (101) and the first front lens (102) is 13.5±0.2mm, the interval between the first front lens (102) and the optical filter (103) is 12.7±0.2mm, the filter The distance between the light sheet (103) and the field diaphragm (104) is 6±0.2mm, and the distance between the field diaphragm (104) and the second front lens (105) is 60.8±0.2mm. 4. The long-wave infrared Doppler differential interferometer according to claim 2, characterized in that: the central wavelength of the optical filter is 8781.5nm, and the FWHM of the optical filter is 127nm. 5. long-wave infrared Doppler differential interferometer according to claim 2, is characterized in that: described beam splitter plate (203) and compensation plate (204) are zinc selenide glass plates; 202) and the second field-of-view widening prism (205) have the same structure and are all prisms with a certain angle on the front and rear surfaces, and the material is zinc selenide; the first grating (201) and the second grating (206) have the same structure, and their groove density It is 150 lines/mm, and the blaze angle is 41.588°. 6. The long-wave infrared Doppler differential interferometer according to claim 5, characterized in that: the first imaging lens (301) is a biconvex positive lens, and the second imaging lens (302) is a meniscus negative lens, The third imaging lens (303) is a meniscus positive lens; The fringe imaging lens also includes a second aperture stop (304), and the second aperture stop (304) is placed at the detector cold screen (305). 7. The long-wave infrared Doppler differential interferometer according to claim 6, characterized in that: the materials of the first imaging lens (301), the second imaging lens (302) and the third imaging lens (303) are germanium ; The interval between the first imaging lens (301) and the second imaging lens (302) is 33.5±0.03mm, the interval between the second imaging lens (302) and the third imaging lens (303) is 41.8±0.03mm, the third The distance between the imaging lens (303) and the detector window is 20±0.03mm. 8. The long-wave infrared Doppler differential interferometer according to claim 1, characterized in that: the front lens (1) is a Keplerian afocal system; the fringe imaging lens (3) F/# is 2, and the magnification β=-0.28. 9. The long-wave infrared Doppler differential interferometer according to claim 1, characterized in that: the distance between the front lens (1) and the beam splitter plate (203) is 60±0.2mm; the compensation plate (204) The distance between the compensation plate (204) and the stripe imaging lens (3) is adjustable, and at normal temperature and pressure, the distance between the compensation plate (204) and the stripe imaging lens (3) is 60±0.2mm. 10. The long-wave infrared Doppler differential interferometer according to claim 1, characterized in that: the detector is a scientific grade CCD camera with a spectral range of 8-10 μm, a pixel size of 30 μm, and an array size of 320×256, working temperature is -40℃～+71℃.