Long baseline optical interferometer system and method of optical path collimation

Abstract

The application discloses a long-base optical interference system and an optical path collimation method, and comprises an interference terminal and two optical path devices; the optical path device comprises a parallel light tube, a reflecting telescope and a guide star system; parallel light generated by the parallel light tube enters the guide star system after the reflecting telescope; the guide star system comprises a light splitting prism, a first mirror, a first lens, a second mirror and a guide star camera; the parallel light entering the guide star system is split into transmitted light and reflected light by the light splitting prism, wherein the reflected light sequentially passes through a folded axis structure composed of the first mirror, the first lens and the second mirror, and enters the guide star camera; the transmitted light split by the light splitting prism of the guide star system of the two optical path devices is respectively a first light beam and a second light beam; the interference terminal focuses the first light beam and the second light beam after beam combination, and then the first light beam and the second light beam propagate to the interference terminal camera. The system can be applied to outdoor observation, and the method is used for optical path collimation of the long-base optical interference system, so that stable optical interference fringes are obtained.

Description

Technical Field

[0001] This invention relates to the field of astronomical telescope calibration and adjustment, and more specifically to a long baseline optical interferometry system and an optical path collimation method. Background Technology

[0002] As humanity's exploration of the universe deepens, the number of telescopes built for astronomical observation is increasing. Larger apertures result in stronger light-gathering capabilities and higher spatial resolution. However, constrained by technology, funding, and other factors, telescope apertures cannot be increased indefinitely. This has led to the development of long-baseline interferometry (LBI). A LBI system utilizes an array of multiple small apertures, which are then combined through baseline synthesis to form a high-resolution, large-aperture optical system. While this represents a significant breakthrough in single-aperture telescope structures, the telescopes still need to be connected via optical systems. Some systems have baseline lengths reaching hundreds of meters. This discrete structure and increased baseline length introduce new challenges to optical axis alignment. Atmospheric turbulence, mechanical vibrations, and assembly / adjustment errors can all cause alignment errors, thus affecting the beam combining and interference process of starlight entering the telescope.

[0003] Therefore, in outdoor observation scenarios, it is essential to provide a long-baseline optical interferometer system that facilitates optical path collimation and adjustment, and to ensure accurate collimation, calibration, and beam combining of the entire long-baseline optical interferometer system's optical path. Unlike the small-scale assembly and adjustment operations of indoor optical systems, outdoor assembly and adjustment are more difficult and require higher precision. Ensuring interference stability and improving beam combining efficiency and pointing accuracy are also of great significance for the future development of long-baseline optical interferometer systems. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies by providing a long baseline optical interferometry system and an optical path collimation method. By constructing a long baseline optical interferometry system that facilitates optical path collimation adjustment, a collimator is used to simulate starlight entering a telescope. The centroid positions of two light spots on the images captured by the guide camera and the interferometer terminal camera are observed to determine the collimation status of the interferometric optical path. By aligning the centroid of the light spots with the calibration center of the images captured by the guide camera and the interferometer terminal camera, the collimation and beam combining of the two beams are achieved.

[0005] Technical Solution: A long baseline optical interferometry system, characterized in that it includes an interferometer terminal and two optical path devices; the optical path devices include a collimator for simulating starlight, a reflecting telescope with a folded-axis structure, and a guiding system; the parallel light generated by the collimator enters the guiding system after passing through the reflecting telescope; the guiding system includes a beam splitter, a first reflecting mirror, a first lens, a second reflecting mirror, and a guiding camera; the parallel light entering the guiding system is split into transmitted light and reflected light by the beam splitter, wherein the reflected light sequentially passes through the folded-axis structure composed of the first reflecting mirror, the first lens, and the second reflecting mirror, and enters the guiding camera; the transmitted light split by the beam splitter of the guiding system of the two optical path devices are respectively the first beam and the second beam;

[0006] The interference terminal includes a third reflecting mirror, a beam combiner, a second lens, and an interference terminal camera; the first beam enters the beam combiner directly, and the second beam is reflected to the beam combiner by the third reflecting mirror; the first beam and the second beam are combined into one beam in the beam combiner, and after being focused by the second lens, they propagate to the interference terminal camera.

[0007] Furthermore, the collimator is a straight tube supported by a tripod and placed in front of the entrance pupil of the reflecting telescope; the incident end of the collimator is connected to a laser source via an optical fiber, and the parallel light generated at the exit end uniformly irradiates the entrance pupil of the reflecting telescope to simulate starlight.

[0008] Furthermore, the collimator can be adjusted in four dimensions, the laser source is a 650mm single-mode fiber laser, and the output aperture of the collimator is 200mm, which is the same as the entrance pupil aperture of the reflecting telescope, ensuring that the beam enters the system completely.

[0009] Furthermore, the reflecting telescope includes a primary mirror, a secondary mirror, and a third mirror, with the third mirror located between the primary and secondary mirrors; the primary and secondary mirrors are parabolic reflectors, and the third mirror is a plane reflector; the primary mirror has a central opening, the optical axis of the primary mirror coincides with the optical axis of the secondary mirror, and the optical axis of the third mirror forms a 45-degree angle with the optical axis of the primary mirror; parallel light passes through the telescope system composed of the primary and secondary mirrors in sequence and then converges, while the outgoing parallel light continues to propagate and is reflected by the third mirror before entering the guiding system.

[0010] Furthermore, the primary mirror of the reflecting telescope has a focal length of 800mm, the secondary mirror has a focal length of 100mm, and the beam ratio is 8:1; the output beam diameter of the reflecting telescope is 25mm.

[0011] Furthermore, the guiding camera is a CCD with a resolution of 1280*960 and a pixel size of 3.75μm*3.75μm; the interferometric terminal camera is an EMCCD with a resolution of 512*512 and a pixel size of 13μm*13μm.

[0012] Furthermore, the third reflecting mirror, beam combiner, second lens, and interferometric terminal camera of the interference terminal are all placed on the same optical platform and located on the same straight line.

[0013] An optical path collimation method based on the aforementioned long baseline optical interferometry system includes the following steps:

[0014] Step 1, Coarse Adjustment: In each optical path device, adjust the attitude of the collimator so that the center of the parallel light emitted from the collimator coincides with the center of each mirror of the corresponding reflecting telescope.

[0015] Step 2, Fine-tuning I: Within each optical path device, adjust the optical components of the guiding system so that the center of mass of the light spot within the guiding system coincides with the calibration center of the image captured by the corresponding guiding camera;

[0016] Step 3, Fine-tuning II: The first and second beams entering the interferometer terminal are blocked sequentially, so that the centroid of the light spot generated by the interferometer terminal coincides with the calibration center of the image captured by the interferometer terminal camera, thus completing the collimation and beam combining.

[0017] Furthermore, it is characterized by,

[0018] Step one specifically involves adjusting the attitude of the collimator in four dimensions within each optical path device. These four dimensions are the X-axis, Y-axis, pitch, and yaw, so that the center of the emitted parallel light coincides with the center of the primary mirror, secondary mirror, and tertiary mirror of the corresponding reflecting telescope. This completes the coarse adjustment process.

[0019] Step two specifically involves adjusting the second reflector of the guiding system so that the center of the centroid of the guiding system's spot coincides with the calibration center of the image captured by the corresponding guiding camera, thus completing fine-tuning step I.

[0020] Step three specifically includes the following steps:

[0021] Step 1) First, block the second beam in front of the third reflecting mirror of the interferometer terminal, and adjust the beam combiner so that the center of the centroid of the light spot behind the second lens coincides with the calibration center of the image captured by the interferometer terminal camera.

[0022] Step 2) Next, block the first beam that directly enters the beam combiner, and adjust the third mirror so that the center of the centroid of the second beam after passing through the beam combiner and the second lens coincides with the calibration center of the image captured by the interference terminal camera; that is, the fine adjustment step II is completed.

[0023] Beneficial effects:

[0024] 1) This invention discloses a long-baseline optical interferometry system that can be applied to outdoor observations. The system's configuration reduces the assembly and adjustment difficulties caused by the separate structure and baseline length, thus improving assembly and adjustment efficiency. When performing starlight tracking in outdoor observations, the long-baseline optical interferometry system, based on a guiding algorithm, can consistently maintain the centroid of the starlight spot after it enters the system at the calibration center of the images captured by the guiding camera and the interferometer terminal camera, ensuring that the long-baseline optical interferometry system obtains stable optical interference fringes.

[0025] 2) This invention discloses an optical path collimation method for a long-baseline optical interferometer system. This method can be applied to long-baseline optical interferometer systems used for outdoor observation. A collimator simulates starlight entering a reflecting telescope, then exits via a folded axis and enters the guiding system and the interferometer terminal, respectively. By adjusting the collimator's attitude and the optical components of the guiding system and the interferometer terminal, the centroids of the two light spots are aligned with the calibration centers of the images captured by the guiding camera and the interferometer terminal camera, respectively, thus achieving collimation and beam combining of the interferometric optical path. This optical path collimation method is easy to operate, achieves a telescope pointing accuracy of 5 arcseconds, and can obtain stable optical interference fringes. Attached Figure Description

[0026] Figure 1 A flowchart of an optical path collimation method for a long baseline optical interferometer system provided for this invention patent;

[0027] Figure 2 This invention patent provides a schematic diagram of the arrangement of a collimator, a reflecting telescope, a star guide system, and an interferometer terminal in a long baseline optical interferometer system.

[0028] Figure 3 This is a schematic diagram of the primary mirror, secondary mirror, and tertiary mirror of the reflecting telescope in this invention patent.

[0029] Figure 4 This is a schematic diagram of the specific structure of the guiding star system in this invention patent;

[0030] Figure 5 This is a schematic diagram showing the arrangement of the optical components of the interference terminal in this invention patent.

[0031] The diagram is labeled as follows: Collimator 1; Tripod 101; Reflecting Telescope 2: Primary Mirror 201; Secondary Mirror 202; Third Mirror 203; Guiding System 3: Beam Spectrometer 301; First Reflector 302; First Lens 303; Second Reflector 304; Guiding Camera 305; First Beam 306; Second Beam 307; Interferometer Terminal 4: Third Reflector 401; Beam Combiner 402; Second Lens 403; Interferometer Terminal Camera 404. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions of this invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The described embodiments are only a part of the embodiments of this invention, not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0033] like Figure 2 As shown, a long baseline optical interferometry system includes an interferometer terminal 4 and two optical path devices. The optical path devices include a collimator 1 for simulating starlight, a reflecting telescope 2 with a folded-axis structure, and a guiding system 3. The parallel light generated by the collimator 1 enters the guiding system 3 after passing through the reflecting telescope 2. The transmitted light from the two optical path devices, separated by a beam splitter 301 in the guiding system 3, forms a first beam 306 and a second beam 307, respectively.

[0034] The collimator 1 is a straight tube supported by a tripod 101 and placed in front of the entrance pupil of the reflecting telescope 2. The incident end of the collimator 1 is connected to a laser source via an optical fiber, and the parallel light generated at the exit end uniformly irradiates the entrance pupil of the reflecting telescope 2 to simulate starlight from infinity. The collimator 1 is adjustable in four dimensions. The laser source is a 650mm single-mode fiber laser, and the exit aperture of the collimator 1 is 200mm, which is the same size as the entrance pupil aperture of the reflecting telescope 2, ensuring that the beam enters the system completely.

[0035] like Figure 3 As shown, the reflecting telescope 2 includes a primary mirror 201, a secondary mirror 202, and a third mirror 203, with the third mirror 203 located between the primary mirror 201 and the secondary mirror 202. The primary mirror 201 and the secondary mirror 202 are parabolic reflectors, while the third mirror 203 is a plane reflector. The primary mirror 201 has a central opening, and its optical axis coincides with that of the secondary mirror 202. The optical axis of the third mirror 203 forms a 45-degree angle with the optical axis of the primary mirror 201. The distance between the primary mirror 201 and the secondary mirror 202 is 700 mm, and the distance between the secondary mirror 202 and the third mirror 203 is 500 mm. The primary mirror 201 has a focal length of 800 mm, the secondary mirror 202 has a focal length of 100 mm, and the beam reduction ratio is 8:1. The output beam diameter of the reflecting telescope 2 is 25 mm.

[0036] The parallel light beam is reduced in diameter after passing through the telescope system consisting of the primary mirror 201 and the secondary mirror 202. Specifically, the parallel incident light with a 200mm aperture emitted from the collimator 1 is reduced in diameter after passing through the telescope system consisting of the primary mirror 201 and the secondary mirror 202, with a reduction ratio of 8:1, and the diameter of the emitted parallel light is reduced to 25mm. The emitted parallel light continues to propagate and is reflected by the three mirrors 203 before entering the guiding system 3.

[0037] like Figure 4 As shown, the guiding system 3 is located on the forked optical platform of the reflecting telescope 2. The guiding system 3 includes a beam splitter 301, a first reflecting mirror 302, a first lens 303, a second reflecting mirror 304, and a guiding camera 305. Parallel light entering the guiding system 3 is split into transmitted light and reflected light by the beam splitter 301. The reflected light passes through the folded axis structure composed of the first reflecting mirror 302, the first lens 303, and the second reflecting mirror 304 in sequence, and enters the guiding camera 305. The centroid position of the light spot can be observed on the image captured by the guiding camera 305. The transmitted light enters the interferometer terminal 4. The guiding camera 305 is a CCD with a resolution of 1280*960 and a pixel size of 3.75μm*3.75μm.

[0038] like Figure 5 As shown, the interference terminal 4 includes a third reflecting mirror 401, a beam combiner 402, a second lens 403, and an interference terminal camera 404. The third reflecting mirror 401, beam combiner 402, second lens 403, and interference terminal camera 404 are all placed on the same optical platform and located on the same straight line. The first beam 306 directly enters the beam combiner 402, and the second beam 307 is reflected by the third reflecting mirror 401 to the beam combiner 402. The first beam 306 and the second beam 307 are combined into one beam within the beam combiner 402, focused by the second lens 403, and then propagate to the interference terminal camera 404. The overlap of the centroids of the two beams can be observed on the image captured by the interference terminal camera 404. The interference terminal camera 404 is an EMCCD with a resolution of 512*512 and a pixel size of 13μm*13μm.

[0039] like Figure 1 As shown, an optical path collimation method based on the aforementioned long baseline optical interferometry system includes the following steps:

[0040] Step 1, Coarse Adjustment: In each optical path device, adjust the attitude of the collimator so that the center of the parallel light emitted from the collimator coincides with the center of each mirror of the corresponding reflecting telescope.

[0041] Step one specifically involves adjusting the attitude of the collimator in four dimensions within each optical path device. These four dimensions are the X-axis, Y-axis, pitch, and yaw, so that the center of the emitted parallel light coincides with the center of the primary mirror, secondary mirror, and tertiary mirror of the corresponding reflecting telescope. This completes the coarse adjustment process.

[0042] Step 2, Fine-tuning I: Within each optical path device, adjust the optical components of the guiding system so that the center of mass of the guiding system's light spot coincides with the calibration center of the image captured by the corresponding guiding camera;

[0043] Step two specifically involves adjusting the second reflector of the guiding system so that the center of the centroid of the guiding system's spot coincides with the calibration center of the image captured by the corresponding guiding camera, thus completing fine-tuning step I.

[0044] Step 3, Fine-tuning II: The first and second beams entering the interferometer terminal are blocked sequentially, so that the centroid of the light spot generated by the interferometer terminal coincides with the calibration center of the image captured by the interferometer terminal camera, thus completing the collimation and beam combining.

[0045] Step three specifically includes the following steps:

[0046] Step 1) First, block the second beam in front of the third reflecting mirror of the interferometer terminal, and adjust the beam combiner so that the center of the centroid of the light spot behind the second lens coincides with the calibration center of the image captured by the interferometer terminal camera.

[0047] Step 2) Next, block the first beam that directly enters the beam combiner, and adjust the third mirror so that the center of the centroid of the second beam after passing through the beam combiner and the second lens coincides with the calibration center of the image captured by the interference terminal camera; that is, the fine adjustment step II is completed.

[0048] After completing the above fine-tuning step II, the optical path collimation of the system is completed. At this time, it can be ensured that the two beams entering the interference terminal are successfully combined, and the pointing accuracy of the telescope can reach within 5 arcseconds.

[0049] This invention provides an optical path collimation method based on a long-baseline optical interferometer system, applicable to outdoor observations of long-baseline optical interferometer systems. It reduces the assembly and adjustment difficulties caused by the separate structure and baseline length, improving assembly and adjustment efficiency, and achieving a telescope pointing accuracy of 5 arcseconds. When performing starlight tracking in outdoor observations, the long-baseline optical interferometer system, based on a guiding algorithm, can consistently maintain the centroid of the starlight spot after it enters the system at the calibration center of the images captured by the guiding camera and the interferometer terminal camera, ensuring that the long-baseline optical interferometer system obtains stable optical interference fringes.

[0050] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An optical path collimation method based on a long-baseline optical interferometry system, characterized in that, The long baseline optical interferometry system includes an interferometry terminal and two optical path devices; The optical path device includes a collimator for simulating starlight, a reflecting telescope with a folded-axis structure, and a guiding system. The parallel light generated by the collimator enters the guiding system after passing through the reflecting telescope. The guiding system includes a beam splitter, a first reflecting mirror, a first lens, a second reflecting mirror, and a guiding camera. The parallel light entering the guiding system is split into transmitted and reflected light by the beam splitter, with the reflected light sequentially passing through the folded-axis structure formed by the first reflecting mirror, the first lens, and the second reflecting mirror before entering the guiding camera. The transmitted light split by the beam splitter of the guiding system of each of the two optical path devices is the first beam and the second beam, respectively. The interference terminal includes a third reflecting mirror, a beam combiner, a second lens, and an interference terminal camera; the first beam directly enters the beam combiner, and the second beam is reflected by the third reflecting mirror to the beam combiner; the first beam and the second beam are combined into one beam in the beam combiner, focused by the second lens, and then propagated to the interference terminal camera; the third reflecting mirror, beam combiner, second lens, and interference terminal camera of the interference terminal are all placed on the same optical platform and located on the same straight line; The optical path collimation method includes the following steps: Step 1, Coarse Adjustment: In each optical path device, adjust the attitude of the collimator so that the center of the parallel light emitted from the collimator coincides with the center of each mirror of the corresponding reflecting telescope. Step 2, Fine-tuning I: Within each optical path device, adjust the optical components of the guiding system so that the center of mass of the light spot within the guiding system coincides with the calibration center of the image captured by the corresponding guiding camera; Step 3, Fine-tuning II: The first and second beams entering the interferometer terminal are blocked sequentially, so that the centroid of the light spot generated by the interferometer terminal coincides with the calibration center of the image captured by the interferometer terminal camera, thus completing the collimation and beam combining.

2. The optical path collimation method based on a long baseline optical interferometry system according to claim 1, characterized in that, The collimator is a straight tube supported by a tripod and placed in front of the entrance pupil of the reflecting telescope. The incident end of the collimator is connected to a laser source via an optical fiber, and the parallel light generated at the exit end uniformly irradiates the entrance pupil of the reflecting telescope to simulate starlight.

3. The optical path collimation method based on a long baseline optical interferometry system according to claim 2, characterized in that, The collimator can be adjusted in four dimensions. The laser source is a 650mm single-mode fiber laser. The output aperture of the collimator is 200mm, which is the same as the entrance pupil aperture of the reflecting telescope, ensuring that the beam enters the system completely.

4. The optical path collimation method based on a long baseline optical interferometry system according to claim 1, characterized in that, The reflecting telescope includes a primary mirror, a secondary mirror, and a third mirror, with the third mirror located between the primary and secondary mirrors. The primary and secondary mirrors are parabolic reflectors, while the third mirror is a plane reflector. The primary mirror has a central opening, and the optical axis of the primary mirror coincides with the optical axis of the secondary mirror. The optical axis of the third mirror forms a 45-degree angle with the optical axis of the primary mirror. Parallel light passes through the telescope system composed of the primary and secondary mirrors in sequence, then converges. The emitted parallel light continues to propagate, is reflected by the third mirror, and then enters the guiding system.

5. The optical path collimation method based on a long baseline optical interferometry system according to claim 4, characterized in that, The primary mirror of the reflecting telescope has a focal length of 800mm, the secondary mirror has a focal length of 100mm, and the beam ratio is 8:1; the output beam diameter of the reflecting telescope is 25mm.

6. The optical path collimation method based on a long baseline optical interferometry system according to claim 1, characterized in that, The guiding camera is a CCD with a resolution of 1280*960 and a pixel size of 3.75μm*3.75μm; the interferometric terminal camera is an EMCCD with a resolution of 512*512 and a pixel size of 13μm*13μm.

7. The optical path collimation method based on a long baseline optical interferometry system according to claim 1, characterized in that, Step one specifically involves adjusting the attitude of the collimator in four dimensions within each optical path device. These four dimensions are the X-axis, Y-axis, pitch, and yaw, so that the center of the emitted parallel light coincides with the center of the primary mirror, secondary mirror, and tertiary mirror of the corresponding reflecting telescope. This completes the coarse adjustment process. Step two specifically involves adjusting the second reflector of the guiding system so that the center of the centroid of the guiding system's spot coincides with the calibration center of the image captured by the corresponding guiding camera, thus completing fine-tuning step I. Step three specifically includes the following steps: Step 1) First, block the second beam in front of the third reflecting mirror of the interferometer terminal, and adjust the beam combiner so that the center of the centroid of the light spot behind the second lens coincides with the calibration center of the image captured by the interferometer terminal camera. Step 2) Next, block the first beam that directly enters the beam combiner, and adjust the third mirror so that the center of the centroid of the second beam after passing through the beam combiner and the second lens coincides with the calibration center of the image captured by the interference terminal camera; that is, the fine adjustment step II is completed.

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