CN211696888U

CN211696888U - Knife edge device for measuring focal length in installation and adjustment of long-focus reflection telescope

Info

Publication number: CN211696888U
Application number: CN201921931150.9U
Authority: CN
Inventors: 刘强; 王欣; 黄庚华; 何志平; 舒嵘
Original assignee: Shanghai Institute of Technical Physics of CAS
Current assignee: Shanghai Institute of Technical Physics of CAS
Priority date: 2019-11-11
Filing date: 2019-11-11
Publication date: 2020-10-16
Anticipated expiration: 2029-11-11

Abstract

The patent discloses a knife edge device for measuring focal length in installation and adjustment of a reflection long-focus telescope. In the process of assembling and adjusting the large-aperture telescope, a knife edge device with a readable high-precision five-dimensional adjusting frame is adopted, and a laser interferometer and a photoelectric autocollimator which are used in the assembling and adjusting process are attached, so that the focal length of a high-precision test telescope system in the process of assembling and adjusting the large-aperture reflective long-focus telescope is realized, the problem that the focal length of a primary mirror and a secondary mirror cannot be accurately controlled in the assembling and adjusting process of the traditional large-aperture reflective long-focus telescope is solved, and the assembling and adjusting precision and the optical correction efficiency are greatly improved.

Description

Knife edge device for measuring focal length in installation and adjustment of long-focus reflection telescope

Technical Field

The patent belongs to the field of optical testing and optical adjustment, and relates to a knife edge device for measuring focal length in adjustment of a reflection long-focus telescope.

Background

In order to realize higher resolution, the aperture of the telescope system is increasingly larger, the focal length of the system is also longer, and the focal length control of the large-aperture reflective telescope optical system is required to be more and more accurate. The method can accurately test and control the focal length of the large-caliber reflective long-focus telescope system in the processes of optical processing and optical adjustment.

In the traditional optical adjustment process, two main methods are used for measuring the focal length of a large-caliber reflection-type long-focus telescope system: in the first method, a glass plate (a parallel flat plate with a fixed width line pair) is placed on the focal plane of the telescope system, and then the theodolite is used for testing the corresponding angle of the fixed width line pair in front of the main mirror of the telescope system, so that the focal length of the system can be calculated. In the method, because the glass compass plate has a certain thickness, the surface where the actually tested line pair with the fixed width is located is not on the focal plane, and in addition, in the process of testing the angle corresponding to the fixed line width by using the theodolite, the error of testing the focal length of the long-focus telescope is larger due to the artificial error of line pressing interpretation. In the second method, a detector is required to be placed on the focal plane of the telescope, then the telescope system and the detector are integrated to be aligned with the long-focus collimator, a point light source of the focal plane of the collimator forms an image point on the detector, the telescope system is rotated for a fixed angle, and the distance between two image points on the detector is tested, so that the focal distance of the system can be calculated. In addition, the test telescope system needs to be specially changed in a test light path, the detector needs to be installed again in each test, and the optical adjustment efficiency of the large-aperture telescope system is very low.

Therefore, how to test the focal length of the large-caliber reflection-type long-focus telescope system in real time, with high precision and high efficiency and guide the adjustment in the optical adjustment process is a problem to be solved in the field of optical adjustment.

Disclosure of Invention

The utility model aims at providing a knife edge device that is used for heavy-calibre reflection-type long focus telescope test system focus in optical adjustment process, and the device lower part is readable number high accuracy five dimension alignment jig 3 to can the reading. The upper part of the device is a cubic prism 2 with cross lines and a knife edge 1 which are arranged on a high-precision five-dimensional adjusting frame 3. The laser interferometer 4 is a parallel light which is formed by a spherical wave emitted by a point A and passes through a telescope system consisting of a primary mirror (8) and a secondary mirror 9, the parallel light is incident to a large-caliber plane mirror 10 and is reflected back to the telescope system to be converged at a point B, when the optical axis of the telescope system is superposed with the normal line of the large-caliber plane mirror 10, a point A, B is superposed, when the optical axis of the telescope system has a certain angle with the normal line of the large-caliber plane mirror 10, a point A, B is not superposed, and the focal length of the telescope system can be calculated according to the distance and the angle of the point A, B.

Another objective of the present invention is to provide a method for measuring the focal length of an optical system of a large-aperture reflective telescopic telescope by using the knife edge device, which comprises the following steps:

the method comprises the following steps: placing a knife edge 1, a cubic prism 2 with a cross reticle, a high-precision five-dimensional adjusting frame 3 with reading, a laser interferometer 4, a large five-dimensional adjusting frame 5, a plane mirror 6, a large-caliber reflective long-focus telescope system to be measured and composed of a main mirror 8 and a secondary mirror 9 on the same large turntable, and adjusting a large-caliber plane mirror 10 and a laser interferometer 4 to make the normal of the large-caliber plane mirror 10 and the optical axis of the laser interferometer 4 collinear with the optical axis of the large-caliber reflective long-focus telescope system composed of the main mirror 8 and the secondary mirror 9, and testing zero field wave aberration of the large-caliber telescope system composed of the main mirror 8 and the secondary mirror 9 by using the laser interferometer 4 and making the defocusing value zero as shown in (1) of the attached figure 3;

step two: replacing a spherical lens of the laser interferometer 4 with a plane lens, and adjusting the rotation and pitch dimensions of the readable high-precision five-dimensional adjusting frame 3 to make the normal of the cubic prism 2 with the cross reticle collinear with the optical axis of the laser interferometer 4, as shown in (2) of the attached drawing 3;

step three: replacing a plane lens of the laser interferometer 4 with a spherical lens, adjusting the translational dimension of the readable high-precision five-dimensional adjusting frame 3 perpendicular to the optical axis to ensure that the knife edge is just cut on the focus A of the lens of the interferometer, and checking interference fringes on the interferometerAnd (6) judging. Recording the reading H of the translation dimension of the high-precision five-dimensional adjusting frame 3 perpendicular to the optical axis₁As shown in FIG. 3 (3);

step four: aligning the photoelectric autocollimator 7 to the plane reflector 6 on the large turntable, and recording the angle theta₁Rotating the large turntable to record the angle theta of the photoelectric autocollimator 7 at the moment₂As shown in fig. 3 (4);

step five: adjusting the translational dimension of the readable high-precision five-dimensional adjusting frame 3 perpendicular to the optical axis to ensure that the knife edge is just coincided with the B point of the laser emitted by the laser interferometer 4 after passing through a large-caliber telescope system consisting of a primary mirror 8 and a secondary mirror 9 and being reflected by a large-caliber plane mirror 10 and then converged by the large-caliber telescope system again, and recording the reading H of the translational dimension of the high-precision five-dimensional adjusting frame 3 perpendicular to the optical axis at the moment₂As shown in FIGS. 3(5) and (6);

step six: then the focal length of the large-aperture telescope system can be calculated as follows:

the characteristics and the beneficial effect of this patent mainly embody following several aspects: (1) the knife edge device for measuring the focal length is simple and small, and is easy to build; (2) high-precision test equipment can be adopted for testing the two parameters for calculating the focal length, and the focal length precision of the large-caliber reflective long-focus telescope system for testing and calculating is high; (3) the knife edge device and the measuring method can be used for testing in the optical assembling and adjusting process of the large-caliber reflective long-focus telescope system, an optical assembling and adjusting light path does not need to be dismantled, transition is not needed, testing is carried out at any time, and the testing efficiency is improved; (4) in the test process, equipment test data are adopted, so that the artificial reading error is eliminated, and the test repetition precision is greatly improved.

Drawings

FIG. 1 is a schematic view of the knife edge device of the present patent in terms of composition and test light path;

FIG. 2 is a schematic diagram of the self-light calibration steps of the knife edge device for testing the focal length of the large-caliber reflective tele telescope in the patent: wherein, figure (1) is a schematic diagram of a knife edge device self optical correction step I, figure (2) is a schematic diagram of a knife edge device self optical correction step II, and figure (3) is a schematic diagram of a knife edge device self optical correction step III;

FIG. 3 is a schematic diagram of the method for testing the focal length of the large-caliber reflective tele telescope of the present patent: wherein fig. 1 is a schematic diagram of a step one of measuring a focal length, fig. 2 is a schematic diagram of a step two of measuring a focal length, fig. 3 is a schematic diagram of a step three of measuring a focal length, fig. 4 is a schematic diagram of a step four of measuring a focal length, fig. 5 is a schematic diagram of a step five of measuring a focal length, and fig. 6 is a schematic diagram of a step six of measuring a focal length.

Detailed Description

An embodiment of the method of the present patent will be described in detail below with reference to the accompanying drawings.

The main components used in this patent are explained:

cube prism 2: custom machining, the side length is 35mm, the angle difference of 90 degrees and the tower difference are both better than 3 seconds, the RMS of each surface is better than 1/15 wavelength @633nm, six surfaces of the aluminum-plated reflecting film are plated, and one surface of the reflecting film is carved with a cross line and is made of a material K9.

Photoelectric autocollimator 8: TriAngle company model number is TA500-57 photoelectric autocollimator, clear aperture is 50mm, view field angle 1300X950 seconds, resolution is 0.02 seconds, and repeatability is + -0.05 seconds.

Readable high-precision five-dimensional adjusting frame 3: the direction used for adjusting the knife edge comprises horizontal dimension adjustment, front and back dimension adjustment, height dimension adjustment, pitching dimension adjustment and rotation dimension adjustment, wherein the horizontal dimension adjustment precision is superior to 5um and can be read.

The knife edge device for testing the focal length of the large-caliber reflective long-focus telescope comprises the following specific steps:

the method comprises the following steps: the cubic prism 2 is arranged on the horizontal dimension perpendicular to the optical axis direction of the interferometer of the readable high-precision five-dimensional adjusting frame 3, and the surface of the cubic prism 2 with the cross lines faces the direction of horizontal dimension adjustment. The cubic prism 2 is aligned by the photoelectric inner focusing 11, and the photoelectric inner focusing 11 is adjusted so that the light emitted from the photoelectric inner focusing 11 passes through the cross line of the original path on the surface of the cubic prism 2 and is positioned at the center of the detector of the photoelectric inner focusing 11, as shown in fig. 2 (1).

Step two: adjusting the focal length of the electro-optically autofocus 11, so that the in-focus image is imaged on the surface of the cube prism 2, and adjusting the translation of the electro-optically autofocus 11, so that the cross-hatched lines on the surface of the cube prism 2 are located in the center of the detector of the electro-optically autofocus 11, as shown in fig. 2 (2).

Step three: and adjusting the horizontal dimension of the readable high-precision five-dimensional adjusting frame 3 perpendicular to the optical axis direction of the interferometer to the other end, adjusting the focal length of the photoelectric inner focusing 11, so that the cross reticle on the surface of the cubic prism 2 is clearly imaged on a detector of the photoelectric inner focusing 11, and at the moment, checking whether the image formed by the cross reticle on the surface of the cubic prism 2 deviates from the center of the detector. And if the deviation exists, adjusting the angle of the cubic prism 2, then returning to the step 1), and then performing the step 2), the step 3) until the image formed by the cross reticle on the surface of the square prism 2 in the step 3) does not deviate from the center of the detector, as shown in the attached figure 2(3), completing the self-adjustment of the knife edge device for testing the focal length of the large-caliber reflection type long-focus telescope system.

Claims

1. A knife edge device for measuring focal length in adjustment of a reflection long-focus telescope comprises a knife edge (1), a cubic prism (2) with a cross reticle, a high-precision five-dimensional adjusting frame (3) capable of reading numbers, a laser interferometer (4), a large five-dimensional adjusting frame (5), a plane mirror (6) and a photoelectric autocollimator (7), and is characterized in that:

the lower part of the knife edge device is a readable high-precision five-dimensional adjusting frame (3), the upper part of the knife edge device is a cube prism (2) with a cross line and a knife edge (1) which are arranged on the high-precision five-dimensional adjusting frame (3), a spherical wave emitted by a point A of a laser interferometer (4) becomes parallel light through a telescope system consisting of a primary mirror (8) and a secondary mirror (9), the parallel light enters a large-caliber plane mirror (10), is reflected back to the telescope system and is converged at a point B, when the optical axis of the telescope system is superposed with the normal of the large-caliber plane mirror (10), a point A, B is superposed, when the optical axis of the telescope system has a certain angle with the normal of the large-caliber plane mirror (10), a point A, B is not superposed, and the focal length of the telescope system can be calculated according to the distance and the angle of the point A, B.

2. The knife-edge apparatus for measuring focal length in fitting a reflex telescopic telescope according to claim 1, wherein: the cube prism (2) with the cross reticle is made of quartz materials, the vertical angle difference and the tower difference are both better than 3 seconds, the six-surface type RMS is better than 1/15 wavelength @633nm, six surfaces of the cube prism are plated with aluminum reflecting films, the reflectivity is larger than 90%, and one surface of the cube prism is carved with the cross reticle.

3. The knife-edge apparatus for measuring focal length in fitting a reflex telescopic telescope according to claim 1, wherein: the high-precision five-dimensional adjusting frame (3) capable of reading is used for adjusting the position of a knife edge and comprises a horizontal dimension adjusting mechanism, a front dimension adjusting mechanism, a rear dimension adjusting mechanism, a height dimension adjusting mechanism, a pitching dimension adjusting mechanism and a rotating dimension adjusting mechanism, wherein the horizontal dimension adjusting precision is superior to 5 um.

4. The knife-edge apparatus for measuring focal length in fitting a reflex telescopic telescope according to claim 1, wherein: the large five-dimensional adjusting frame (5) is used for adjusting the position of the interferometer and comprises horizontal dimension adjustment, front and back dimension adjustment, height dimension adjustment, pitching dimension adjustment and rotation dimension adjustment.

5. The knife-edge device for measuring focal length in fitting of a reflex telescopic telescope according to claim 1, wherein the angular resolution of the photoelectric autocollimator (7) is 0.02 sec, and the repetition accuracy is ± 0.05 sec.