CN110793755A - Knife-edge device and measuring method for measuring focal length in the setting and adjustment of reflecting telephoto telescope - Google Patents

Abstract

The invention discloses a knife-edge device and a measuring method for measuring the focal length in the assembling and adjustment of a reflective telephoto telescope. During the installation and adjustment of the large-aperture telescope, a knife-edge device with a readable high-precision five-dimensional adjustment frame is used, along with the laser interferometer and photoelectric autocollimator used in the installation and adjustment process. High-precision testing of the focal length of the telescope system during the installation and adjustment of the reflective telephoto telescope solves the problem that the focal length of the primary and secondary mirrors cannot be accurately controlled during the installation and adjustment of the traditional large-diameter reflective telephoto telescope, and greatly improves the installation and adjustment accuracy and optical calibration efficiency.

Description

Knife-edge device and measuring method for measuring focal length in the setting and adjustment of reflecting telephoto telescope

technical field

The invention belongs to the field of optical testing and optical adjustment, and relates to a knife-edge device and a method for measuring focal length in the adjustment of a reflective telephoto telescope. The invention also relates to a large-diameter reflective telephoto telescope in the process of testing and adjustment by using the above-mentioned knife-edge device A method of measuring the focal length of a system.

Background technique

In order to achieve higher resolution for the optical system load of space reflection cameras, the aperture of the telescope system is getting larger and larger, and the focal length of the system is also longer, which requires more and more precise control of the focal length of the optical system of the large aperture reflection telescope. This is for the precise testing and control of the focal length of the large-diameter reflective telescopic telescope system in the process of optical processing and optical adjustment.

Traditionally, in the process of optical adjustment, there are two main methods for measuring the focal length of large-aperture reflective telescopic telescope systems: the first method is to place a Boro plate (one with a fixed-width line pair on the focal plane of the telescope system); Parallel plate), and then use the theodolite to test the angle corresponding to the fixed width line pair in front of the main mirror of the telescope system, then the system focal length can be calculated. In this method, because the Boro plate has a certain thickness, the surface of the line pair with the fixed width actually tested is not on the focal plane. In addition, in the process of using the theodolite to test the angle corresponding to the fixed line width, due to the human error in the interpretation of the pressure line, for the long line. The focal length test error of the focal telescope is large. In the second method, a detector needs to be placed on the focal plane of the telescope, and then the telescope system and the detector as a whole are aligned with the telephoto collimator, and the point light source on the focal plane of the collimator forms an image point on the detector. The focal length of the system can be calculated by rotating the telescope system at a fixed angle and measuring the distance between the two image points on the detector. In this method, the detector needs to be installed on the focal plane of the telescope system, and the installation accuracy of this process affects the test accuracy. In addition, the test telescope system needs to change the test optical path in a special field, and the detector needs to be re-installed for each test. The adjustment efficiency is very low.

Therefore, in the process of optical adjustment, how to test the focal length of the large-diameter reflective telephoto telescope system in real time, with high precision and high efficiency, and guide the adjustment, is a problem that needs to be solved in the field of optical adjustment.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a knife-edge device for testing the focal length of the system during the optical assembly and adjustment of a large-diameter reflective telephoto telescope. The upper part of the device is a cube prism 2 with a cross line and a knife edge 1 placed on a high-precision five-dimensional adjustment frame 3 . The laser interferometer 4 emits an ideal spherical wave from point A, passes through the telescope system consisting of the primary mirror (8) and the secondary mirror 9 to become parallel light, enters the large-caliber standard plane mirror 10, reflects back to the telescope system, and converges at point B, When the optical axis of the telescope system is coincident with the normal of the large-aperture standard plane mirror 10, then points A and B are coincident; when the optical axis of the telescope system and the normal of the large-diameter standard plane mirror 10 are at a certain angle, points A and B are not coincident. According to the distance and angle of points A and B, the focal length of the telescope system can be calculated.

Another object of the present invention is to provide a method for measuring the focal length of the optical system of a large-diameter reflective telephoto telescope by utilizing the above-mentioned knife-edge device, and the specific steps of the measuring method are as follows:

Step 1: Put the knife edge 1, the cube prism 2 with the cross scribed line, the high-precision five-dimensional adjustment frame with reading 3, the laser interferometer 4, the large-scale five-dimensional adjustment frame 5, the plane mirror 6, and the main mirror to be measured. The large-diameter reflective telephoto telescope system composed of 8 and the secondary mirror 9 is placed on the same large turntable, and the large-diameter standard plane mirror 10 and the laser interferometer 4 are adjusted so that the normal of the large-diameter standard plane mirror 10 and the laser interferometer 4 The optical axis is collinear with the optical axis of the large-diameter reflective telephoto telescope system composed of the primary mirror 8 and the secondary mirror 9, and the large-diameter telescope system composed of the primary mirror 8 and the secondary mirror 9 is tested by using the laser interferometer 4. The zero field of view wave aberration, and make the defocus value zero, as shown in Figure 3 (1);

Step 2: Replace the spherical lens of the laser interferometer 4 with a plane lens, and adjust the rotation and pitch dimensions of the readable and high-precision five-dimensional adjustment frame 3, so that the normal line of the cube prism 2 with cross lines is the same as that of the laser interferometer 4. The optical axes are collinear, as shown in Figure 3 (2);

Step 3: Replace the plane lens of the laser interferometer 4 with a spherical lens, adjust the translation dimension of the readable high-precision five-dimensional adjustment frame 3 and the optical axis perpendicular to the optical axis, so that the knife edge is exactly on the focal point A of the lens of the interferometer. Check the interference fringes on the interferometer to judge. Record the reading H ₁ of the translation dimension perpendicular to the optical axis of the high-precision five-dimensional adjustment frame 3 at this time, as shown in Figure 3 (3);

Step 4: Align the photoelectric autocollimator 7 with the plane mirror 6 on the large turntable, record the angle θ ₁ at this time, rotate the large turntable, and record the angle θ ₂ of the photoelectric autocollimator 7 at this time, as shown in the accompanying drawings 3(4);

Step 5: Adjust the translation dimension of the readable high-precision five-dimensional adjustment frame 3 perpendicular to the optical axis, so that the knife edge is exactly the same as the laser emitted by the laser interferometer 4 through the large-diameter telescope system composed of the primary mirror 8 and the secondary mirror 9, After being reflected by the large-caliber standard plane mirror 10 again, the point B converged by the large-caliber telescope system is overlapped again, and the reading H ₂ of the translation dimension perpendicular to the optical axis of the high-precision five-dimensional adjustment frame 3 at this time is recorded, as shown in accompanying drawing 3 ( 5) and (6);

Step 6: The focal length of the large aperture telescope system can be calculated as:

The features and beneficial effects of the present invention are mainly reflected in the following aspects: (1) the knife-edge device for measuring the focal length is simple and compact, and easy to build; The calculated focal length of the large-aperture reflective telescopic telescope system has high focal length accuracy; (3) the knife-edge device and the measurement method can be tested during the optical adjustment process of the large-diameter reflective telescopic telescope system without removing the optical path for adjustment. No need to switch fields, test at any time, and improve test efficiency; (4) During the test process, equipment test data are used to eliminate human reading errors and greatly improve test repeatability.

Description of drawings

Fig. 1 is the schematic diagram of the composition of the knife edge device of the present invention and the test optical path;

Fig. 2 is the schematic diagram of the self-optical calibration step of the knife-edge device for testing the focal length of the large-diameter reflective telephoto telescope of the present invention: wherein Figure (1) is a schematic diagram of the knife-edge device self-optical calibration step 1, and Figure (2) is the knife-edge device self-optical calibration step. The schematic diagram of the calibration step 2, Figure (3) is the schematic diagram of the optical calibration step 3 of the knife edge device itself;

Fig. 3 is the schematic diagram of the method for testing the focal length of the large-diameter reflective telephoto telescope of the present invention: wherein Fig. (1) is a schematic diagram of step 1 of measuring focal length, Fig. (2) is a schematic diagram of step 2 of measuring focal length, and Fig. (3) is Figure (4) is a schematic diagram of step 4 of measuring focal length, Figure (5) is a schematic diagram of step 5 of measuring focal length, and Figure (6) is a schematic diagram of step 6 of measuring focal length.

Detailed ways

Embodiments of the patented method will be described in detail below with reference to the accompanying drawings.

The main components used in the present invention are described:

Cube prism 2: customized processing, side length 35mm, 90-degree angle difference and tower difference are better than 3 seconds, each facet RMS is better than 1/15 wavelength@633nm, six-sided aluminized reflective film, one of which is engraved with Crosshair, material K9.

Photoelectric autocollimator 8: TriAngle's model is TA500-57 photoelectric autocollimator, with a clear aperture of 50mm, a field of view angle of 1300X950 seconds, a resolution of 0.02 seconds, and a repeatability of ±0.05 seconds.

Readable high-precision five-dimensional adjustment frame 3: used to adjust the orientation of the knife edge, including horizontal dimension adjustment, front and rear dimension adjustment, high and low dimension adjustment, pitch dimension adjustment, and rotation dimension adjustment, among which the adjustment accuracy of horizontal dimension is better than 5um. reading.

The specific steps of the present invention to test the knife-edge device for the focal length of the large-diameter reflective telephoto telescope are as follows:

Step 1: Install the cube prism 2 above the horizontal dimension of the readable high-precision five-dimensional adjustment frame 3 that is perpendicular to the optical axis of the interferometer. The cross-haired side of the cube prism 2 faces the direction of horizontal dimension adjustment. Use the photoelectric inner focusing 11 to align the cube prism 2, and adjust the photoelectric inner focusing 11, so that the light emitted by the photoelectric inner focusing 11 will return to the detector of the photoelectric inner focusing 11 through the cross line on the surface of the cube prism 2. The center, as shown in Figure 2(1).

Step 2: Adjust the focal length of the photoelectric inner focusing 11, so that the inner focusing imaging and the surface of the cube prism 2, and adjust the translation of the photoelectric inner focusing 11, so that the cross line on the surface of the cube prism 2 is located in the detection of the photoelectric inner focusing 11 The center of the device is shown in Figure 2(2).

Step 3: Adjust the horizontal dimension of the readable high-precision five-dimensional adjustment frame 3 perpendicular to the optical axis of the interferometer, and to the other end, adjust the focal length of the photoelectric internal focusing 11, so that the cross line on the surface of the cube prism 2 is clear On the detector of imaging and photoelectric internal focusing 11, at this time, check whether the image formed by the reticle on the surface of the cube prism 2 is deviated from the center of the detector. If there is a deviation, adjust the angle of the cube prism 2, then go back to step 1), then proceed to step 2), step 3), until the image formed by the cross-hatched on the surface of the cube prism 2 in step 3) and the center of the detector are As long as there is no deviation, as shown in Figure 2 (3), the knife-edge device for testing the focal length of the large-diameter reflective telescopic telescope system is self-adjusted.

Claims (6)

1. A knife-edge device for measuring the focal length in the assembly and adjustment of a reflective telephoto telescope, comprising a knife-edge (1), a cube prism (2) with a cross-scribed line, a readable high-precision five-dimensional adjustment frame (3), a laser interference Instrument (4), large-scale five-dimensional adjustment frame (5), plane reflector (6), photoelectric autocollimator (7), characterized in that: The lower part of the knife-edge device is a readable high-precision five-dimensional adjustment frame (3), and the upper part of the knife-edge device is a cube prism (2) with a cross line placed on the high-precision five-dimensional adjustment frame (3) and The knife edge (1), the laser interferometer (4) emits an ideal spherical wave from point A, which becomes parallel light through a telescope system composed of a primary mirror (8) and a secondary mirror (9), and is incident on a large-caliber standard plane mirror (10) , reflected back to the telescope system and converged at point B. When the optical axis of the telescope system coincides with the normal of the large-aperture standard plane mirror (10), then points A and B are coincident. When the normal line has a certain angle, points A and B do not coincide. According to the distance and angle of points A and B, the focal length of the telescope system can be calculated. 2. the knife-edge device of measuring focal length in a kind of reflective telephoto telescope according to claim 1, it is characterized in that: the described cube prism (2) with cross engraved line is quartz material, vertical angle difference and tower The difference is better than 3 seconds, the RMS of six surfaces is better than 1/15 wavelength@633nm, the six surfaces are coated with aluminized reflective film, the reflectivity is greater than 90%, and one side is engraved with cross lines. 3. a kind of knife edge device for measuring focal length in the adjustment of a kind of reflecting telephoto telescope according to claim 1, it is characterized in that: described readable five-dimensional adjustment frame (3) with high precision is used to adjust the orientation of the knife edge , including horizontal dimension adjustment, front and rear dimension adjustment, high and low dimension adjustment, pitch dimension adjustment, and rotation dimension adjustment, among which the adjustment accuracy of horizontal dimension is better than 5um. 4. The knife-edge device for measuring focal length in the assembling and adjusting of a reflective telephoto telescope according to claim 1, characterized in that: the large-scale five-dimensional adjustment frame (5) is used to adjust the orientation of the interferometer, including the horizontal dimension Adjustment, front and rear dimension adjustment, high and low dimension adjustment, pitch dimension adjustment, rotation dimension adjustment. 5. The knife-edge device for measuring focal length in the assembling and adjusting of the reflective telephoto telescope according to claim 1, is characterized in that, the angular resolution of described photoelectric autocollimator (7) is 0.02 seconds, and repeatability ±0.05 second. 6. a focal length measuring method based on the knife-edge device measuring focal length in the adjustment of the reflective telephoto telescope according to claim 1, it is characterized in that the method steps are as follows: Step 1: Put the knife edge (1), the cube prism with cross-marked line (2), the high-precision five-dimensional adjustment frame with reading (3), the laser interferometer (4), the large five-dimensional adjustment frame (5), The plane reflector (6), the large-diameter reflective telephoto telescope system to be measured, which is composed of a primary mirror (8) and a secondary mirror (9), is placed on the same large turntable, and the large-diameter standard plane mirror (10) and the laser are adjusted an interferometer (4), so that the normal line of the large-diameter standard plane mirror (10), the optical axis of the laser interferometer (4) and the large-diameter reflective telephoto telescope system composed of the primary mirror (8) and the secondary mirror (9) The optical axes are collinear, and the laser interferometer (4) is used to test the zero-field wave aberration of the large-diameter telescope system composed of the primary mirror (8) and the secondary mirror (9), and the defocus value is zero; Step 2: Replace the spherical lens of the laser interferometer (4) with a plane lens, and adjust the rotation and pitch dimensions of the readable and high-precision five-dimensional adjustment frame (3), so that the cube prism (2) with cross lines is used. The line is collinear with the optical axis of the laser interferometer (4); Step 3: Replace the plane lens of the laser interferometer 4 with a spherical lens, and adjust the translation dimension of the readable high-precision five-dimensional adjustment frame (3) perpendicular to the optical axis, so that the knife edge is exactly on the focal point A of the lens of the interferometer. , judge by looking at the interference fringes on the interferometer. Record the reading H ₁ of the translation dimension perpendicular to the optical axis of the high-precision five-dimensional adjustment frame (3) at this time; Step 4: Align the photoelectric autocollimator (7) with the plane mirror (6) on the large turntable, record the angle θ ₁ at this time, rotate the large turntable, and record the angle of the photoelectric autocollimator (7) at this time θ ₂ ; Step 5: Adjust the translation dimension of the readable high-precision five-dimensional adjustment frame (3) perpendicular to the optical axis, so that the knife edge is exactly aligned with the laser light emitted by the laser interferometer (4) through the primary mirror (8) and the secondary mirror (9). ), after being reflected by the large-aperture standard plane mirror (10), the point B converged by the large-aperture telescope system overlaps again, and the high-precision five-dimensional adjustment frame (3) at this time is recorded perpendicular to the optical axis. the reading of the translation dimension H ₂ ; Step 6: The focal length of the large aperture telescope system can be calculated as:

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