CN112596329B

CN112596329B - Self-rotating filter wheel device for lunar base ultraviolet camera and imaging method

Info

Publication number: CN112596329B
Application number: CN202011246189.4A
Authority: CN
Inventors: 肖思; 付利平; 王天放; 白雪松; 贾楠; 李睿智; 皮彦婷; 江芳
Original assignee: National Space Science Center of CAS
Current assignee: National Space Science Center of CAS
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2021-09-10
Anticipated expiration: 2040-11-10
Also published as: CN112596329A

Abstract

The invention belongs to the technical field of extreme ultraviolet cameras, and particularly relates to a self-rotating filter wheel device and an imaging method for a lunar base ultraviolet camera, wherein the device comprises the following components: the device comprises a filter set (1), a structure frame (2), a central rotating shaft (3) and a rotating motor (4); the filter set (1) is fixed on the structure frame (2), the combined filter is supported in front of the camera detector through the structure frame, the bottom of the structure frame is connected with the central rotating shaft (3), and the central rotating shaft is connected with the rotating motor (4). According to the invention, by adopting a mode of splicing after fractional image acquisition, the acquisition of a multiband image can be still realized under the condition of full-field image detection, and the problem that only partial field images can be obtained in multiband section detection in the prior art is solved.

Description

Self-rotating filter wheel device for lunar base ultraviolet camera and imaging method

Technical Field

The invention belongs to the technical field of extreme ultraviolet cameras, and particularly relates to a self-rotating filter wheel device for a lunar base ultraviolet camera and an imaging method.

Background

The air glow and aurora are important natural luminescence phenomena in the space optical radiation background, and are aimed at O air glow and N air glow at the height of ionized layer₂Airglow is detected, and the ionospheric electron density and thermal O/N can be obtained by inversion₂And the information is obtained, so that the ionosphere and the disturbance condition thereof are monitored and forecasted. The moon is a celestial body closest to the earth, one side of the celestial body always faces the earth, the surface of the moon has no atmosphere, the magnetic field and the lunar shock are extremely weak, the surface is quiet, and the celestial body is a very good natural observation platform. By utilizing the lunar platform, in the process of the moon running around the earth, the earth plasma layer is imaged at different angles, the obtained extreme ultraviolet image is inverted to obtain the volume distribution of the earth plasma layer, and then scientific research and space weather forecast are significant works.

An extreme ultraviolet imager TEX is carried on a moon goddess (SELENE) emitted in Japan in 2008, the SELENE runs around the moon, imaging observation on an earth plasma layer is realized, TEX working wave bands are 30.4nm and 83.4nm, a field angle is 10.9 degrees multiplied by 10.9 degrees, a camera images an earth disc in a field splicing mode, namely, each wave band can only obtain an image of a half of the earth disc, and distribution of the whole earth plasma layer cannot be obtained. In 2013, an extreme ultraviolet camera is carried on a Chinese Chang' e-II lander, an extreme ultraviolet image of a plasma layer of the earth is obtained on the surface of a moon from the side for the first time, the working waveband of the ultraviolet camera is 30.4nm, the viewing angle is 15 degrees, the camera can realize the imaging of the whole plasma layer of the earth disc, and the imaging of the waveband of 83.4nm cannot be realized. Although foreign EUV 83.4nm detectors have many in-orbit operations, no 83.4nm data are published to date. Therefore, the design of a set of multiband imaging method of the extreme ultraviolet camera is very critical to realize multiband global disk imaging by utilizing a lunar orbit or a lunar-based platform.

The multiband imaging modes are: (1) field splitting, the method cannot realize the detection of the whole target, such as SELENE in Japan, a part of fields are used for detecting 30.4nm waveband images, and the rest fields are used for detecting 83.4nm images; (2) the semi-reflecting and semi-transparent color separation sheet or the light separation prism is utilized to realize light separation of different wavelengths, and the method cannot be applied because the extreme ultraviolet band does not have proper transmission glass materials; (3) the method of placing the filter wheel in front of the focal plane can realize the imaging of a double-waveband full-circle disc of the extreme ultraviolet camera by switching the filters with different wavebands. However, the conventional filter wheel has a large volume, occupies the space of a camera, and blocks a central light path, so that the transmittance of the system is reduced, and the imaging quality is reduced. And the extreme ultraviolet filter is easy to damage, so that the filter is easy to damage due to large-amplitude rotation. Therefore, the existing multiband imaging method is not applicable to the detection requirement of the earth plasma layer.

Disclosure of Invention

The invention provides a self-rotating filter wheel device and an imaging method for a lunar base ultraviolet camera, aiming at solving the difficulty of the light splitting mode of the existing extreme ultraviolet (< 100nm) camera, and solving the problems of difficult light splitting, large volume and high risk of the traditional filter wheel of the existing extreme ultraviolet camera. The invention designs the self-rotating filter wheel, which is different from the traditional filter wheel, and has the characteristics of not occupying redundant space and not swinging in large amplitude under the condition of simultaneously realizing multi-band and full-field detection, thereby reducing the volume of a camera and greatly reducing the risk of the system.

The invention provides a self-rotating filter wheel device for a lunar base ultraviolet camera, which comprises: the device comprises a filter set 1, a structure frame 2, a central rotating shaft 3, a rotating motor 4, a camera detector 5, a support structure bracket 6 and a camera lens cone 7;

the optical filter set 1 is fixed on the structure frame 2, the central rotating shaft 3 is connected with the center of the bottom of the structure frame 2, and the rotating motor 4 is connected with the central rotating shaft 3; the camera detector 5 is fixed on the structural frame 2; the filter set 1 is fixed in front of the camera detector 5; the structure frame 2 is supported on the camera lens barrel 7 through a support structure 6;

the filter set comprises a plurality of filters, the plurality of filters are circumferentially distributed in the structure frame 2, and the plurality of filters are distributed at equal intervals.

As an improvement of the above technical solution, the device includes a filter set 1 (the number of filters can be designed into two or more than two according to task requirements), a structural frame 2, a central rotating shaft 3 and a rotating motor 4 thereof. Wherein, filter set 1 is connected with structure frame 3, and structure frame 2 provides the support for filter set 1, supports filter set 1 before camera detector 5. The central rotating shaft 3 is connected with the bottom of the structure frame 2, the rotating motor 4 is connected with the central rotating shaft 3, and the structure frame and the optical filter set can rotate by rotating the central rotating shaft 3 through the rotating motor 4.

As one improvement of the technical scheme, the central rotating shaft (3) and the rotating motor (4) are arranged behind the camera detector (5).

As one improvement of the technical scheme, the optical filter material comprises one or more than two of a metal In film, a metal Al film or magnesium fluoride glass, the number of the optical filters is n, and n is more than or equal to 2.

As an improvement of the technical scheme, the camera detector type comprises one or more than two of CMOS, CCD or cross-line anode.

As an improvement of the above technical solution, the structural frame includes one or more of aluminum alloy, titanium alloy, and invar steel.

The invention provides an imaging method of a lunar base ultraviolet camera, which is realized based on the self-rotating filter wheel device for the lunar base ultraviolet camera, and comprises the following steps:

1) combining n optical filters, installing the optical filters in front of a camera detector 5 through a structural frame 2, and collecting an image of the optical filter group at the position by the camera detector 5 to be recorded as a first image;

2) turning on a rotating motor 4, rotating a central rotating shaft 3 through the rotating motor 4, rotating the central rotating shaft 3360 degrees/n for the first time, and collecting an image of the combined optical filter at the position by a camera detector to be recorded as a second image;

3) repeating the step 2) until the central rotating shaft 3 is rotated for the nth-1 time, and collecting the image of the combined optical filter at the position by the camera detector to be recorded as an nth image;

4) splitting the images acquired in the steps 1) -3), and then splicing the split images to obtain spliced images.

As an improvement of the above technical solution, the number of the images acquired in step 4) is n, and the number of the acquired images after stitching is n.

As one improvement of the above technical solution, the specific splitting and splicing process in step 4) is that a device with n combined optical filters images the earth disk for the first time, the earth disk image is divided into n band sector images, and the cone angle of each sector image is 360 °/n; rotating the rotating optical filter for 360 degrees/n, and then imaging the earth disc for the second time; by analogy, after the rotating optical filter is rotated for 360 degrees/n, the earth disk is imaged for the nth time, at the moment, n images with different wave bands are obtained in each sector area, and n sector images with different view fields are obtained in each wave band; finally, the images of the same wave band in different fields of view are spliced together to obtain n full-field images of different wave bands. From the process of image splicing, the number of n is not limited, but the development of the combined filter is limited by the number of n, and the preferable range value of n is suggested to be 2-4.

As one improvement of the technical scheme, the image is respectively split into n parts according to the positions of the optical filters with different wave bands, and the optical filter set (1) realizes the acquisition of the images with different wave bands by rotating around the central rotating shaft (3).

As one of the improvement of the technical scheme, when the device uses two filter sheets, the working imaging process is as follows: (1) combining 2 optical filters into an optical filter group 1, a structure frame 2, a central rotating shaft 3 and a rotating motor 4 thereof, and installing; (2) collecting an image of the combined optical filter at the position by a camera detector, and recording the image as an image A; (3) turning on a rotating motor, rotating a central rotating shaft by 180 degrees, and collecting an image of the combined optical filter at the position by a camera to be recorded as an image B; (4) and splitting the images A and B, and splicing the images to obtain a new image A 'and a new image B'.

For an extreme ultraviolet camera for observing a plasma layer of the earth, the integration time is far longer than that of a common camera and is generally about 10 minutes (such as an extreme ultraviolet camera carried by a moon goddess in Japan and a Chang 'e' II in China), so that the method for collecting images at different time periods and then splicing the images is adopted aiming at the characteristic that the target changes slowly, and the use of the images is not influenced. According to the requirement of a task on detection wave bands, the combined optical filter can be designed into two or more than two according to the detection number of the wave bands, and the detection requirements of different wave band numbers are realized by increasing the times of rotating and splicing images. .

Compared with the prior art, the invention has the beneficial effects that:

1) according to the invention, by adopting a mode of splicing after fractional image acquisition, the acquisition of a multiband image can be still realized under the condition of full-field image detection, and the problem that only partial field-of-view images can be obtained in the multiband detection in the prior art is solved;

2) the invention designs a set of self-rotating filter wheel, which hardly occupies redundant space, does not shield a light path, does not increase the central blocking of an optical system, and solves the problems that the prior art occupies the space of a camera when selecting a traditional filter wheel, and the system transmittance is reduced and the imaging quality is reduced due to shielding the light path;

3) the extreme ultraviolet band filter is extremely brittle and easy to break. Compared with the traditional filter wheel, the self-rotating filter wheel designed by the invention has small swing amplitude, and overcomes the problem of filter damage caused by the swing process in the prior art;

4) when the rotating mechanism has a rail fault, the traditional filter wheel mode can directly cause the camera to be incapable of working, and the risk of the camera running in the rail is increased. The light filter is rotated by the rotation shaft, so that the field-of-view light splitting mode can be converted, and the work is continuously kept in the mode of obtaining partial field-of-view images.

Drawings

FIG. 1 is a schematic structural diagram of a lunar-base ultraviolet camera imaging device according to the present invention;

fig. 2 is a schematic diagram of a filter set of an imaging device of a lunar-base ultraviolet camera according to the present invention (n ═ 2);

fig. 3 is a schematic three-dimensional structure diagram (n ═ 2) of an imaging device of a lunar-base ultraviolet camera according to the present invention;

fig. 4 is a schematic diagram of a three-dimensional structure of a filter set in an imaging device of a lunar base ultraviolet camera according to the present invention (n ═ 2);

fig. 5 is an image stitching schematic diagram (n ═ 2) of an imaging method of a lunar base ultraviolet camera according to the present invention;

fig. 6 is an image stitching schematic diagram of the lunar base ultraviolet camera imaging method of the present invention (n-4);

reference numerals:

1. a filter set; 2. a structural frame; 3. a central rotating shaft; 4. rotating the motor; 5. a camera detector; 6. a support structure bracket, 7, a camera lens barrel; 8. an image A; 9. an image B; 10. an image A'; 11. an image B'; 12. rotating the front filter set wavelength a image; 13. rotating the front filter set wavelength b image; 14. rotating the wavelength a image of the post-filter set; 15. rotating the wavelength b image of the post-filter group; 16. an image C; 17. an image D; 18. an image E; 19. an image F; 20. rotating the front filter set wavelength c image; 21. rotating the front filter set wavelength d image; 22. rotating the front filter set wavelength e image; 23. rotating the front filter set wavelength f image; 24. rotating the wavelength c image of the filter group once; 25. rotating the wavelength d image of the filter group once; 26. rotating the wavelength e image of the filter group once; 27. rotating the filter set wavelength f image once; 28. rotating the wavelength c image of the post-filter group twice; 29. rotating the wavelength d image of the post-filter group twice; 30. rotating the wavelength e image of the filter group twice; 31. rotating the wavelength f image of the filter group twice; 32. rotating the wavelength c image of the filter group for three times; 33. rotating the filter set for three times to obtain a wavelength d image; 34. rotating the wavelength e image of the filter group for three times; 35. rotating the filter set for three times to obtain a wavelength f image; 36. an image C'; 37. an image D'; 38. an image E'; 39. image F'.

Detailed Description

The invention will now be further described with reference to the accompanying drawings.

EXAMPLE 1

The embodiment provides a self-rotating filter wheel device for a lunar base ultraviolet camera, which comprises a filter set 1, a structure frame 2, a central rotating shaft 3, a rotating motor 4, a camera detector 5, a supporting structure bracket 6 and a camera lens cone 7, wherein the structure frame 2 supports the filter set 1 and places the filter set in front of the camera detector 5. The central rotating shaft 3 is connected with the center of the bottom of the structural frame 2, the central rotating shaft 3 is connected with the rotating motor 4, the central rotating shaft 3 is rotated by the rotating motor 4, so that the structural frame is rotated, and finally, the rotation of the combined optical filter in front of the camera detector is realized, as shown in fig. 1, fig. 2, fig. 3 and fig. 4.

The filter set material needs to be selected according to the requirements of different wave band bandwidths and transmittance, and the structural frame 2 and the central rotating shaft 3 select corresponding materials according to the expansion coefficient of the filter material. In this embodiment, the device needs to meet the requirements of 30.4nm band and 83.4nm band transmission, so the filter set material respectively selects an aluminum thin film as a 30.4nm band filter, selects an In material as an 83.4nm band filter, and selects a low expansion coefficient material invar as the material of the structural frame 2 and the central spindle 3. Since there is no requirement for the rotational speed, there is no special requirement for the rotating electrical machine 4.

When the number n of the optical filters is 2, the specific imaging steps are as follows:

1) combining 2 optical filters into an optical filter group 1, a structure frame 2, a central rotating shaft 3 and a rotating motor 4, and assembling the optical filter group 1 in front of a camera detector 5;

2) collecting the image of the filter set at the position, and recording the image as an image A8;

3) turning on the rotating motor 4, rotating the filter set 180 degrees, and collecting the image of the filter set 1 at the position, which is recorded as an image B9;

4) according to the positions of the filters with different wave bands, respectively splitting the image A and the image B into two parts, recording as a wavelength a image 12 of a filter set before rotation, a wavelength B image 13 of the filter set before rotation, a wavelength a image 14 of a filter set after rotation and a wavelength B image 15 of the filter set after rotation, and recombining the split images to form a new image A '10 and a new image B' 11;

5) the image a '10 and the image B' 11 are final output images respectively representing images of different bands in the full field of view. Fig. 5 shows a method for splitting and splicing images when n is 2.

Example 2

When the number n of the optical filters is 4, the specific imaging steps are as follows:

1) combining 4 filters into a filter set 1, a structure frame 2, a central rotating shaft 3 and a rotating motor 4, and assembling the filter set 1 in front of a camera detector 5;

2) collecting the image of the filter set at the position, and recording the image as an image C16;

3) starting the rotating motor 4, rotating the filter set for 90 degrees for the first time, and collecting an image of the filter set at the position, wherein the image is recorded as an image D17;

4) turning on the rotating motor 4, rotating the filter set for the second time by 90 degrees, and collecting an image of the filter set at the position, and recording the image as an image E18;

5) turning on the rotating motor 4, rotating the filter set for 90 degrees for the third time, and collecting the image of the filter set at the position, and recording the image as an image F19;

6) splitting the image C16, the image D17, the image 18E and the image F19 into four parts according to the positions of the filters with different wave bands, and recording the four parts as a wavelength C image 20 of the filter set before rotation; rotating the front filter set wavelength d image 21; rotating the front filter set wavelength e-image 22; rotating the front filter set wavelength f image 23; the filter set wavelength c image 24 after one rotation; the filter set wavelength d image 25 after one rotation; the filter set wavelength e image 26 after one rotation; the filter set wavelength f image 27 after one rotation; the post-filter set wavelength c image 28 after two rotations; the filter set wavelength d image 29 after two rotations; the post-filter set wavelength e image 30 is rotated twice; rotating the filter set wavelength f image 31 twice; the filter set wavelength c image 32 after three rotations; image 33 of filter set wavelength d after three rotations; the filter set wavelength e image 34 after three rotations; the filter set wavelength f image 35 after three rotations; the split images are recombined (the method is consistent with that when n is 2), and the images become a new image C '36, an image D' 37, an image E '38 and an image F' 39;

5) image C ', image D', image E 'and image F' are final output images, representing images of different wavelength bands in the full field of view, respectively. Fig. 6 shows a method for splitting and splicing images when n is 4.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A self-rotating filter wheel device for a lunar-base ultraviolet camera, the device comprising: the device comprises a filter set (1), a structure frame (2), a central rotating shaft (3), a rotating motor (4), a camera detector (5), a supporting structure bracket (6) and a camera lens cone (7);

the optical filter set (1) is fixed on the structure frame (2), the central rotating shaft (3) is connected with the center of the bottom of the structure frame (2), and the rotating motor (4) is connected with the central rotating shaft (3); the camera detector (5) is fixed on the structure frame (2); the filter set (1) is fixed in front of the camera detector (5); the structure frame (2) is supported on the camera lens cone (7) through a support structure bracket (6);

the filter set (1) comprises a plurality of filters, the plurality of filters are circumferentially distributed in the structure frame (2), and the plurality of filters are distributed at equal intervals.

2. Self-rotating filter wheel device for lunar-base UV cameras according to claim 1, characterized in that the central spindle (3) and the rotation motor (4) are both behind the camera detector (5).

3. The self-rotating filter wheel device for the lunar-base ultraviolet camera as claimed In claim 1, wherein the filter material comprises one or more of metal In film, metal Al film or magnesium fluoride glass, the number of the filters is n, and n is greater than or equal to 2.

4. A self-rotating filter wheel device for a lunar base ultraviolet camera as defined in claim 1, wherein the camera detector type comprises one or more of CMOS, CCD, or cross-line anode.

5. The self-rotating filter wheel device of claim 1, wherein the structural frame comprises one or more of aluminum alloy, titanium alloy, or invar.

6. An imaging method of a lunar base ultraviolet camera, which is implemented based on the self-rotating filter wheel device for the lunar base ultraviolet camera as claimed in any one of the above claims 1 to 5, and which comprises:

step 1), combining n optical filters, installing the optical filters in front of a camera detector (5) through a structural frame (2), and collecting an image of the optical filter group at the position by the camera detector (5) and recording the image as a first image;

step 2) starting a rotating motor (4), rotating a central rotating shaft (3) through the rotating motor (4), rotating the central rotating shaft (3) for 360 degrees/n for the first time, and collecting an image of the combined optical filter at the position by a camera detector to be recorded as a second image;

step 3) repeating the step 2) until the central rotating shaft (3) is rotated for the nth-1 time, and collecting the image of the combined optical filter at the position by the camera detector and recording the image as an nth image;

and 4) splitting the images acquired in the steps 1) to 3), and then splicing the split images to obtain spliced images.

7. The imaging method of the lunar base ultraviolet camera according to claim 6, wherein the number of the images acquired in the step 4) is n, and the number of the images obtained after stitching is n.

8. The imaging method of the lunar base ultraviolet camera according to claim 6, wherein the image is split into n parts according to the positions of the filters with different wave bands, and the filter set (1) realizes the acquisition of the images with different wave bands by rotating around the central rotating shaft (3).