Detection method for amplification factor of large-aperture telescope

Abstract

The invention discloses a method for detecting the amplification factor of a large-aperture telescope. The method comprises the following steps: S1, installing a detection device in place according to detection requirements; s2, the pitch angle and the yaw angle of the detection device are adjusted, so that straight interference fringes are displayed on the surface-shaped interferometer; s3, the pitch angle and the yaw angle of the autocollimator are adjusted, the angle value of the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, and the angle value is set to be 0; s4, adjusting the large-aperture plane mirror to a small angle, recording inclined interference fringes displayed on the surface-shaped interferometer as theta T, and recording an angle value displayed on the autocollimator as theta M; s5, reversely adjusting the large-aperture plane mirror by a small angle, displaying inclined interference fringes on the surface-shaped interferometer, recording the inclined interference fringes as theta T, and recording an angle value displayed on the autocollimator as theta M; s6, calculating the angle magnification M angle of the telescope to be measured, and converting the angle magnification M angle into the magnification M of the telescope to be measured; and S7, replacing the sub-telescope, and repeating the steps S1-S6. The method is high in detection precision and convenient to popularize and apply.

Description

Technical Field

[0001] The invention relates to the fields of astronomical observation technology and astronomical observation instrument detection technology, and in particular to a method for detecting the magnification of a large-aperture telescope. Background Art

[0002] An optical telescope is an optical instrument composed of lenses or reflectors and other optical devices and structural parts for observing distant objects. Among them, reflective optical telescopes are widely used in astronomical observations. Reflective optical telescopes include several large-aperture reflective primary mirrors and small-aperture reflective secondary mirrors, which can magnify the small angle of distant objects at a certain rate, so that they have a larger angle in the image space, making objects that cannot be seen or distinguished with the naked eye become clear and distinguishable.

[0003] Compared with a single-aperture telescope, a spatially distributed synthetic aperture uses a telescope array to achieve the equivalent spatial resolution of a single large-aperture telescope, breaking through the diffraction limit of a single-aperture telescope due to the limitation of the aperture size. There are multiple sub-telescopes in the optical synthetic aperture imaging system, and the magnification of each sub-telescope needs to be accurately detected. If the magnifications of the sub-telescopes are inconsistent, pupil mapping errors will be introduced (pupil mapping refers to the similarity between the figure composed of the entrance pupils of each sub-telescope and the figure composed of its exit pupil) and thus affect the field of view of the optical synthetic aperture imaging system. Therefore, accurate detection of the magnification of each sub-telescope is crucial.

[0004] The optical synthetic aperture imaging system in the present application includes three coaxial reflective sub-telescopes with the same composition, structure and parameters, which are distributed in an equilateral triangle. The design value of the entrance pupil diameter of each sub-telescope is 360 mm, the design value of the exit pupil diameter is 72 mm, the design value of the magnification is 0.2, and the design value of the angular magnification is 5. The aperture of the sub-telescope in the present application is relatively large, and it is a coaxial system. Considering that the existing surface interferometer cannot simultaneously image the exit pupil of the sub-telescope and the large-aperture plane mirror, a new detection method for the magnification of the large-aperture sub-telescope in the optical synthetic aperture imaging is proposed.

[0005] Existing methods and means: 1. Zhejiang Zheguang Technology Co., Ltd. proposed a device and method for measuring the magnification of a self-assembled telescope using the graticule method. A graticule is set between the eyepiece and the objective lens. The lens imaging principle is used to accurately calculate the focal length of the objective lens and the eyepiece. Starting from the actual magnification of the limited farsightedness of the system, the magnification of the focal-free telescope system is finally obtained. The structure is simple and the operation is convenient.

[0006] 2. Shaanxi Zhiyuan Kefeng Optoelectronics Technology Co., Ltd. has proposed a new type of telescope magnification detector, which includes a collimator assembly, a telescope assembly to be tested, a CCD camera assembly, and a mounting platform assembly. The telescope assembly to be tested is located between the collimator assembly and the CCD camera assembly. The collimator assembly emits a light beam that passes through the telescope assembly to be tested and then is imaged by the CCD camera assembly. The image height of the left and right lens barrels of the telescope assembly to be tested is measured by the CCD camera assembly. The measured image height is divided by the graticule value in the collimator assembly to obtain the magnification of the telescope to be tested, which improves the accuracy and efficiency of imaging data collection to a certain extent.

[0007] 3. Harbin Institute of Technology proposed an improved method for measuring the magnification of a self-assembled telescope by direct comparison of viewing angles. This method places the target ruler at the front end of the telescope. When measuring, one eye is used to observe the images of the upper and lower indicators magnified by the telescope through the telescope eyepiece, and the other eye directly observes the target ruler. The target ruler is used to directly measure the distance between the indicator images. The distance between the target ruler indicators divided by the distance between the indicator images is the magnification of the telescope. The system is simple and easy to operate. The error is large when counting by visual inspection.

[0008] 4. Huzhou Normal University proposed a method to measure the pupil of a telescope and calculate its magnification. This method places an aperture stop at the front end of the telescope as the entrance pupil diameter, and an image screen at the rear end of the telescope. The size of the image on the image screen is the exit pupil diameter. The entrance pupil diameter divided by the exit pupil diameter is the magnification of the telescope. This method is simple in system, easy to operate, and has low accuracy.

[0009] Disadvantages of existing technology: (1) In the existing telescope magnification measurement method, the graticule line error and image recognition error are large. The measurement error of the object and image size by visual inspection is even larger. The measurement error of the telescope entrance pupil diameter and exit pupil diameter is also large, so the error of the calculated magnification is also large.

[0010] (2) The above method involves image recognition algorithms, which require the development and optimization of algorithms, which is relatively complex and time-consuming.

[0011] (3) The above method requires more instruments, is difficult to debug, is costly, and has a complex system.

[0012] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0013] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for detecting the magnification of a large-aperture telescope to solve the problems existing in the prior art.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions: A method for detecting the magnification of a large-aperture telescope, the method comprising the following steps: S1. Install the large-aperture plane mirror, the large-aperture plane mirror two-dimensional adjustment seat, the large-aperture telescope, the large-aperture telescope base, the surface interferometer, the surface interferometer base, the autocollimator and the autocollimator base in place according to the detection requirements; S2, adjusting the pitch angle and yaw angle of the large-aperture plane mirror, the large-aperture telescope and the surface interferometer, so that the surface interferometer displays straight interference fringes of the parallel light emitted by the large-aperture plane mirror, the large-aperture telescope and the large-aperture plane mirror and then returning to the surface interferometer; S3, adjusting the pitch angle and yaw angle of the autocollimator so that the parallel light emitted by the autocollimator is reflected by the large-aperture plane mirror and then returns to the autocollimator, and the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, and the angle value is set to 0; S4. Adjust the large-aperture plane mirror to a small angle, and the surface interferometer will show inclined interference fringes, which are recorded as θ T , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ; S5. Adjust the large-aperture plane mirror in the opposite direction to a small angle. The surface interferometer will display inclined interference fringes, which are recorded as θ. T ， , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ， ; S6. Calculate the angular magnification M of the telescope under test 角 , and then converted into its magnification M; S7, replace the sub-telescope, repeat steps S1-S6, and obtain the magnifications M1, M2, and M3 of the three sub-telescopes.

[0015] Further, in step S1, the connection and positional relationship of the large-aperture plane mirror, the large-aperture plane mirror two-dimensional adjustment seat, the large-aperture telescope, the large-aperture telescope base, the surface interferometer, the surface interferometer base, the autocollimator and the autocollimator base is as follows: The large-aperture plane mirror is vertically placed in the large-aperture plane mirror two-dimensional adjustment seat, and the pitch angle and yaw angle of the large-aperture plane mirror are adjusted by the large-aperture plane mirror two-dimensional adjustment seat; The large-aperture telescope is horizontally placed in the large-aperture telescope base, located between the large-aperture plane mirror and the surface interferometer, with its entrance pupil aligned with the large-aperture plane mirror, and its exit pupil aligned with the surface interferometer, so that the surface interferometer displays straight interference fringes of the parallel light emitted by it after passing through the large-aperture plane mirror, the large-aperture telescope, the large-aperture plane mirror and returning to the surface interferometer; The surface interferometer is placed on the surface interferometer base; The autocollimator is placed on the autocollimator base, and its light outlet is aimed at the large-aperture telescope, so that the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator.

[0016] Further, in step S6, the angular magnification M of the telescope under test 角 The calculation formula is as follows: M 角 =(θ T ， -θ T ) / (θ M ， -θ M ); The conversion formula for the magnification M is: ; Among them, △t is the time difference between the plane wavefront that arrives at the telescope at any moment and the time when the wavefront first and finally enters the telescope, c is the speed of light, D is the diameter of the telescope entrance pupil, and d is the diameter of the exit pupil.

[0017] Furthermore, the surface interferometer adopts a ZYGO interferometer.

[0018] By adopting the above technical solution, the present invention has the following beneficial effects: 1) The technology involved is relatively mature and easy to implement. The surface interferometer is a mature product, and the meter-level plane mirror with a surface shape of 1 / 60 wavelength or even 1 / 80 wavelength is also relatively mature. The two-dimensional angle adjustment frame is also very common, which meets the functional and performance requirements of this method; 2) Strong versatility. This method is generally applicable to the magnification measurement of large-aperture coaxial and off-axis telescopes. If the aperture of the telescope to be measured is very large, the aperture of the large-aperture plane mirror can be increased or the telescope to be measured can be partially aligned with the large-aperture plane mirror; 3) Strong applicability. This method provides ideas and solutions for measuring the magnification of telescopes in other telescopic systems; 4) High cost performance. After the telescope magnification test fixture is built, only the telescope to be tested needs to be replaced. Batch testing takes less time, requires fewer steps, and is cost-effective. 5) High detection accuracy. After many tests, this method is more accurate than the traditional method of measuring the size of objects and images, with an accuracy of up to a few ten-thousandths, that is, the fourth decimal place. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The present invention is a structural diagram of a device used in the method for detecting the magnification of a large-aperture telescope.

[0021] Figure 2 It is a schematic diagram of straight interference fringes on the surface interferometer of the present invention.

[0022] Figure 3 Schematic diagram of oblique interference fringes on the surface interferometer of the present invention.

[0023] Figure 4 It is a schematic diagram of reverse oblique interference fringes on the surface interferometer of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0026] Combination Figure 1-4 As shown, a method for detecting the magnification of a large-aperture telescope proposed by the present invention comprises the following steps: S1. Install the large-aperture plane mirror 1, the large-aperture plane mirror two-dimensional adjustment seat 2, the large-aperture telescope 3, the large-aperture telescope base 4, the surface interferometer 5, the surface interferometer base 6, the autocollimator 7 and the autocollimator base 8 in place according to the detection requirements. Figure 1 Also included is the telescope incident light 9 and the telescope outgoing light 10; S2, adjusting the pitch angle and yaw angle of the large-aperture plane mirror, the large-aperture telescope and the surface interferometer, so that the surface interferometer displays straight interference fringes 11 after the parallel light emitted by them passes through the large-aperture plane mirror, the large-aperture telescope and the large-aperture plane mirror and returns to the surface interferometer; S3, adjusting the pitch angle and yaw angle of the autocollimator so that the parallel light emitted by the autocollimator is reflected by the large-aperture plane mirror and then returns to the autocollimator, and the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, and the angle value is set to 0; S4. Adjust the large-aperture plane mirror to a small angle (arc second level), and the surface interferometer will display an inclined interference fringe of 12, recorded as θ T , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ; S5. Then adjust the large-aperture plane mirror in the opposite direction to a small angle (arc second level). The surface interferometer displays an inclined interference fringe 13, which is recorded as θ T ， , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ， ; S6. Calculate the angular magnification M of the telescope under test 角 , and then converted into its magnification M; S7, replace the sub-telescope, repeat steps S1-S6, and obtain the magnifications M1, M2, and M3 of the three sub-telescopes.

[0027] In the present application, the connection and positional relationship of the large-aperture plane mirror, the large-aperture plane mirror two-dimensional adjustment seat, the large-aperture telescope, the large-aperture telescope base, the surface interferometer, the surface interferometer base, the autocollimator and the autocollimator base in step S1 is: The large-aperture plane mirror is vertically placed in the large-aperture plane mirror two-dimensional adjustment seat, and the pitch angle and yaw angle of the large-aperture plane mirror are adjusted by the large-aperture plane mirror two-dimensional adjustment seat; The large-aperture telescope is horizontally placed in the large-aperture telescope base, located between the large-aperture plane mirror and the surface interferometer, with its entrance pupil aligned with the large-aperture plane mirror, and its exit pupil aligned with the surface interferometer, so that the surface interferometer displays straight interference fringes of the parallel light emitted by it after passing through the large-aperture plane mirror, the large-aperture telescope, the large-aperture plane mirror and returning to the surface interferometer; The surface interferometer is placed on the surface interferometer base; The autocollimator is placed on the autocollimator base, and its light outlet is aimed at the large-aperture telescope, so that the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator.

[0028] Further, in step S6, the angular magnification M of the telescope under test 角The calculation formula is as follows: M 角 =(θ T ， -θ T ) / (θ M ， -θ M ); The conversion formula for the magnification M is: ; Among them, △t is the time difference between the plane wavefront that arrives at the telescope at any moment and the time when the wavefront first and finally enters the telescope, c is the speed of light, D is the diameter of the telescope entrance pupil, and d is the diameter of the exit pupil.

[0029] In this application, the surface interferometer adopts ZYGO interferometer; the angle measurement principle of ZYGO interferometer is as follows: The horizontal tilt measured by the ZYGO interferometer is the second-order coefficient Z2 of the Zernike polynomial, and its unit is wavelength λ. The measurement uses a circular mask with n pixels in the mask diameter. The calibration result of the spatial physical size corresponding to the unit pixel of the ZYGO interferometer is a. Then the horizontal deflection angle corresponding to the tilt measurement result of the ZYGO interferometer is: .

[0030] The present application proposes a method for accurately detecting the magnification of a large-aperture telescope. The core is to obtain the magnification value by measuring the angular magnification of the telescope, and the two are in an inverse relationship. The magnification of the large-aperture telescope is detected using a surface interferometer, an autocollimator and an angle-adjustable large-aperture plane mirror. The entrance pupil of the large-aperture telescope is aligned with the large-aperture plane mirror, and the surface interferometer is simultaneously aligned with the exit pupil of the large-aperture telescope. The autocollimator is aligned with the large-aperture plane mirror. When the large-aperture plane mirror produces a small angle change, the surface interferometer displays the interference fringes of the parallel light emitted by it after passing through the large-aperture telescope-large-aperture plane mirror-large-aperture telescope. The angle value reflected by the interference fringes is solved, and the angle value of the large-aperture plane mirror is directly displayed on the autocollimator. The comparison of the two is the angular magnification of the telescope. This method can be used to achieve a higher-precision magnification of a large-aperture telescope with fewer instruments and equipment, fewer mechanisms and devices, and simpler operations, providing a guarantee for the control of pupil mapping errors and field angles of optical synthetic aperture imaging systems.

[0031] Compared with the prior art, the innovations and technical effects of this application mainly include: 1) This method can achieve accurate measurement of the magnification of a small-aperture telescope by using a large-aperture plane mirror and a surface interferometer.

[0032] 2) This method determines the magnification of the telescope by comparing the interference fringes of the telescope outgoing light after being reflected by the plane mirror and the interference fringes of the plane mirror reflected light itself displayed simultaneously on the plane interferometer, and using the angle values ​​represented by the two; 3) This method uses the same reflector as the reference for interference fringes comparison. As a rigid body, the reflector can truly reflect the angle represented by the interference fringes, thereby improving the detection accuracy; 4) After the telescope magnification test fixture is built by this method, only the telescope to be tested needs to be replaced. During batch testing, less time is spent, fewer steps are required, and the detection efficiency is high.

[0033] In addition, the present application can also expand the following aspects: the telescope to be measured can be a coaxial system or an off-axis system; the entrance pupil of the telescope to be measured can be aligned with a plane reflector and the exit pupil can be aligned with a surface interferometer, or the entrance pupil can be aligned with the surface interferometer and the exit pupil can be aligned with a plane reflector; the aperture and shape of the plane reflector are not limited, as long as the requirements are met; an autocollimator can be used to accurately measure the rotation angle of a large-aperture plane mirror, or other precision angle measuring instruments can be used; the entrance pupil or exit pupil of the telescope to be measured can be completely or partially aligned with a large-aperture plane mirror.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting the magnification of a large-aperture telescope, characterized in that: The detection method comprises the following steps: S1. Install the large-aperture plane mirror, the large-aperture plane mirror two-dimensional adjustment seat, the large-aperture telescope, the large-aperture telescope base, the surface interferometer, the surface interferometer base, the autocollimator and the autocollimator base in place according to the detection requirements; S2, adjusting the pitch angle and yaw angle of the large-aperture plane mirror, the large-aperture telescope and the surface interferometer, so that the surface interferometer displays straight interference fringes of the parallel light emitted by the large-aperture plane mirror, the large-aperture telescope and the large-aperture plane mirror and then returning to the surface interferometer; S3, adjusting the pitch angle and yaw angle of the autocollimator so that the parallel light emitted by the autocollimator is reflected by the large-aperture plane mirror and then returns to the autocollimator, and the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, and the angle value is set to 0; S4. Adjust the large-aperture plane mirror to a small angle, and the surface interferometer will show inclined interference fringes, which are recorded as θ T , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ; S5. Adjust the large-aperture plane mirror in the opposite direction to a small angle. The surface interferometer will display inclined interference fringes, which are recorded as θ. T ， , the angle between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator, recorded as θ M ， ; S6. Calculate the angular magnification M of the telescope under test 角 , and then converted into its magnification M; S7, replace the sub-telescope, repeat steps S1-S6, and obtain the magnifications M1, M2, and M3 of the three sub-telescopes.

2. The method for detecting the magnification of a large-aperture telescope according to claim 1, characterized in that: In step S1, the connection and positional relationship of the large-aperture plane mirror, the large-aperture plane mirror two-dimensional adjustment seat, the large-aperture telescope, the large-aperture telescope base, the surface interferometer, the surface interferometer base, the autocollimator and the autocollimator base is as follows: The large-aperture plane mirror is vertically placed in the large-aperture plane mirror two-dimensional adjustment seat, and the pitch angle and yaw angle of the large-aperture plane mirror are adjusted by the large-aperture plane mirror two-dimensional adjustment seat; The large-aperture telescope is horizontally placed in the large-aperture telescope base, located between the large-aperture plane mirror and the surface interferometer, with its entrance pupil aligned with the large-aperture plane mirror, and its exit pupil aligned with the surface interferometer, so that the surface interferometer displays straight interference fringes of the parallel light emitted by it after passing through the large-aperture plane mirror, the large-aperture telescope, the large-aperture plane mirror and returning to the surface interferometer; The surface interferometer is placed on the surface interferometer base; The autocollimator is placed on the autocollimator base, and its light outlet is aimed at the large-aperture telescope, so that the angle value between the large-aperture plane mirror and the autocollimator is displayed on the autocollimator.

3. The method for detecting the magnification of a large-aperture telescope according to claim 1, characterized in that: The angular magnification M of the telescope under test in step S6 角 The calculation formula is as follows: M 角 =(θ T ， -θ T ) / (θ M ， -θ M ); The conversion formula for the magnification M is: ； Among them, △t is the time difference between the plane wavefront that arrives at the telescope at any moment and the time when the wavefront first and finally enters the telescope, c is the speed of light, D is the diameter of the telescope entrance pupil, and d is the diameter of the exit pupil.

4. The method for detecting the magnification of a large-aperture telescope according to claim 1, characterized in that: The surface interferometer adopts a ZYGO interferometer.

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