CN103969787B - A kind of first assembling and positioning method of off-axis four anti-camera lenses - Google Patents

Abstract

A method for initial installation and positioning of an off-axis four-mirror lens. The off-axis four-mirror lens includes a main reflector, a secondary reflector, a third reflector, and a plane reflector, wherein the main reflector and the third reflector are off-axis Axis Aspheric Mirrors. The zero position compensator is used to calibrate the optical axis direction of the off-axis mirror, the four-bar positioning provides a reference for the adjustment of the spatial position of each mirror, and the network of multiple theodolites realizes the initial assembly and positioning of the mirror components. The invention combines the optical axis external lead and the four-bar positioning technology to ensure that the initial assembly of the off-axis four-mirror lens reaches a certain accuracy, and establishes a reasonable starting point for the computer-aided assembly and adjustment of the optical system.

Description

A method for initial assembly and positioning of an off-axis four-mirror lens

technical field

The invention belongs to the technical field of lens assembly and detection, and relates to a method for initial assembly and positioning of an off-axis four-mirror lens.

Background technique

With the wide application and rapid development of space optical remote sensors, large-aperture off-axis optical systems have been widely used due to their characteristics of no central occlusion, high energy utilization, large field of view and high ground resolution. . At present, computer-aided adjustment technology is generally used for the adjustment of off-axis optical lenses. The self-collimating interferometry method detects the wave aberration of the system in real time. The computer-aided adjustment software analyzes the interference fringes, solves the polynomial coefficients of the wave surface, and gives the parameters of each optical element. Adjustment direction and quantitative value guide the correction of the relative position error of each component to meet the final design requirements.

For the assembly and adjustment of traditional spherical transmissive optical system and coaxial total reflection aspheric optical system, relatively mature centering assembly technology can be used. Center, and then assemble multiple optical parts strictly according to the consistency of the optical axis.

Since the off-axis four-mirror lens components have no physical symmetry after molding, and the tolerance requirements for the system are often higher, considering that the off-axis mirror is a part of the mother mirror, it cannot be accurately centered through the traditional centering process. Determine the optical axis of the mirror; at the same time, the virtual vertex of the off-axis mirror brings difficulties to the adjustment of the spatial position of each mirror, which leads to a large amount of misalignment after the initial installation of the off-axis four-mirror lens. The deviation will be very large, causing the effect of the adjustment to fail to converge, resulting in the failure of the computer-aided adjustment.

Contents of the invention

The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a kind of off-axis four-mirror lens initial installation positioning method, in the off-axis four-mirror lens initial installation stage, the optical axis, off-axis angle, off-axis amount and The effective control of the mirror distance greatly improves the positioning accuracy of the initial assembly of the optical system and creates conditions for the next step of computer-aided precision assembly.

The technical solution of the present invention: a method for initial installation and positioning of an off-axis four-mirror lens. The off-axis four-mirror lens includes a main reflector, a secondary reflector, a third reflector, and a plane reflector, wherein the main reflector and the third mirror are off-axis aspheric mirrors; the steps are as follows:

1) Use the first interferometer and zero compensator to lead out the direction of the optical axis of the main reflector; set the incident surface of the light beam to the front of the main reflector, and use two theodolites to measure and measure the optical axis of the main reflector and the direction of the main reflector The included angle α of the normal direction of the back of the mirror;

2) Utilize the first interferometer and the zero compensator to lead out the optical axis direction of the third reflector; set the incident surface of the light beam as the front of the third reflector, and obtain the optical axis direction of the third reflector by means of two theodolite rendezvous and docking measurements Angle β with the normal direction on the back of the third mirror;

3) Calculate and manufacture four long rods from the optical design data of the off-axis four-mirror lens. The material of the long rods is quartz glass with a low expansion coefficient. The four ends of the four long rods are all made into ball heads. The four balls The head positions respectively represent the center position of the incident field of view, the mirror center position of the primary reflector, the mirror center position of the secondary reflector and the mirror center position of the third reflector;

4) Place the four long rods on the adjustment bracket, adjust the height of the center point of the incident field of view and the center point of the secondary reflector, determine the sagittal plane of the central field of view, use the secondary reflector as a reference, and adjust the primary reflector and the third reflector in turn. reflector until the center of each reflector surface contacts the ball head of the long rod;

5) Set the incident surface of the light beam on the front side of the main reflector, set up two theodolites to rendezvous and dock to measure the included angle α ₁ between the standard plane mirror of the second interferometer and the normal direction on the back of the main reflector, and adjust the main reflector so that α ₁ and step 1 ) in the same α;

6) Let the incident surface of the light beam be the front of the third reflector, set up two theodolites to meet and dock to measure the included angle β ₁ between the standard plane mirror of the second interferometer and the normal direction on the back of the third reflector, and adjust the third reflector so that β ₁ Consistent with β in step 2);

7) The parallel light emitted by the second interferometer passes through the main reflector, secondary reflector, third reflector, and plane reflector of the off-axis four-mirror lens, converges to the standard spherical mirror, returns and forms interference fringes in the second interferometer , to complete the initial installation and positioning of the off-axis four-anti.

The specific method of drawing out the direction of the optical axis in step 1) is: place the first interferometer, the zero compensator and the main mirror in sequence from left to right, and the plane wave emitted by the first interferometer passes through the zero compensator and becomes an aspheric surface After the aspheric wave is reflected by the main reflector, it returns to the original path, and then returns to the first interferometer after passing through the zero compensator. Adjust the positions of the zero compensator and the main reflector until the first interferometer measures The value is equal to the surface shape parameter value of the main reflector, and the positions of the zero compensator and the main reflector are fixed. At this time, the optical axis of the main reflector is parallel to the outgoing light direction of the first interferometer.

The specific method for extracting the direction of the optical axis in step 2) is: place the first interferometer, the zero compensator and the third reflector in sequence from left to right, and the plane wave emitted by the first interferometer passes through the zero compensator and becomes non- Spherical waves, aspheric waves are reflected by the third reflector and return to the original path, and then return to the first interferometer after passing through the zero compensator. Adjust the positions of the zero compensator and the third reflector until the first interferometer The measured value is equal to the surface shape parameter value of the third reflector, and the positions of the zero compensator and the third reflector are fixed. At this time, the optical axis of the third reflector is parallel to the outgoing light direction of the first interferometer.

Compared with the prior art, the positive effect of the present invention is that since the off-axis four-mirror lens parts have no physical symmetry after forming, the virtual vertex brings difficulties to the spatial position adjustment of each mirror. Therefore, before the computer-aided adjustment of the off-axis four-mirror lens optical system, it is proposed to use four-bar positioning and multiple theodolite networking methods to adjust the spatial position of each mirror in the main frame, so that the large-diameter off-axis four-mirror lens Under the guidance of theory, the positioning process of initial assembly is completed visually, quantitatively and orderly, which realizes the control and precise adjustment of the mirror distance, optical axis direction and off-axis amount, and improves the space of each mirror in the off-axis four-mirror lens. The positioning accuracy of the position placement enables the high-precision interferometer to accurately detect the image quality of the optical system and establish a reasonable starting point for the computer-aided adjustment algorithm, thereby effectively improving the adjustment efficiency. At the same time, this solution is also suitable for the initial installation and positioning of all off-axis four-mirror lenses.

Description of drawings

Figure 1 is a schematic diagram of the external introduction of the optical axis of the off-axis aspheric zero compensator;

Figure 2 is a schematic diagram of four-bar positioning and optical axis adjustment.

detailed description

The present invention is an initial installation and positioning method of an off-axis four-mirror lens. The off-axis four-mirror lens includes a main reflector 4, a secondary reflector 5, a third reflector 6, and a plane reflector 7, wherein the main reflector 4 And the 3rd reflector 6 is off-axis aspheric reflector 3; Below in conjunction with Fig. 1-Fig. 2, the specific embodiment of the off-axis four-mirror lens of the present invention is described in detail:

Interferometer 1 emits a beam of plane waves and passes through zero compensator 2 to become the required aspheric wave. The aspheric wave is reflected by the off-axis aspheric mirror and then returns to the interferometer through the zero compensator. As shown in Figure 1, the optical paths of the compensator and the interferometer are adjusted to be strictly parallel (the accuracy can be controlled within 10″), and the orientation of the off-axis aspheric mirror is repeatedly adjusted until the measured value is consistent with that of the off-axis aspheric mirror. The surface shape parameter values are equal, at this time the main optical axis of the off-axis aspheric mirror coincides with the optical axis of the compensator and interferometer. Two theodolite rendezvous and docking tests lead the direction of the optical axis of the off-axis aspheric mirror to the back of the mirror Reference plane. Due to the assembly accuracy of the compensator itself, the adjustment error of the detection optical path and the error of intersection measurement, etc., the optical axis extraction accuracy is about 1′.

1) Utilize the first interferometer 1 and the zero compensator 2 to draw the optical axis direction of the main reflector 6; set the light beam incident surface on the front of the main reflector 4, and use two theodolites to measure and obtain the light of the main reflector 4 The included angle α between the axial direction and the normal direction of the back surface of the main reflector 4,

2) Utilize the first interferometer 1 and the zero position compensator 2 to lead out the optical axis direction of the third reflector 6; set the incident surface of the light beam as the front of the third reflector 6, and use two theodolites (T1, T2) to meet and measure Obtain the angle β between the optical axis direction of the third reflector 6 and the normal direction on the back of the third reflector 6;

3) The main body frame is placed on the two-dimensional adjustment table 10, the secondary reflector 5 is installed on the main frame as a reference, and the angle between the second interferometer standard plane 8 and the secondary reflector 5 is measured by the intersection of two theodolites, and the The adjustment table 10 makes the angle between the two is Φ, so that the optical axis is led out to the standard plane reflector 8 .

4) The four end points (A, B, C, D) of the four long rods are selected to represent the incident field of view, the mirror center positions of the primary reflector 4, the secondary reflector 5 and the third reflector 6, respectively. According to the optical system data imported into the PRE structure design software, the theoretical length and angle of the four rods are calculated from the center positions of the mirror surfaces of each mirror. The material is quartz glass with a low expansion coefficient, and the two ends are made of ball heads.

5) As shown in Figure 2, place the four rods on the adjustment bracket, set the incident surface of the light beam of the second interferometer on the front of the main reflector 6, and the laser 11 emits a beam of laser light through endpoints A and B, and adjust the four rods so that AB The connecting line is parallel to the normal direction of the standard plane mirror of the second interferometer, and then, adjust the height of the center point A of the incident field of view and the center point C of the secondary reflector 5 to be consistent, thereby determining the sagittal plane of the central field of view, and adjusting the main reflector 4 in turn , the secondary mirror 5 and the third mirror 6, until the contact positions B, C, D.

6) Set up three theodolites (T3, T4, T5) to self-align the back of the main mirror, the back of the third mirror and the standard plane mirror of the interferometer respectively, adjust the tilt and pitch of the main mirror 4 and the third mirror 6 so that each The mirror optical axis direction coincides with the system optical axis direction. Assume that the incident surface of the light beam is the front of the main reflector 4, set up two theodolites (T4, T5) to meet and dock to measure the included angle α ₁ between the second interferometer standard plane mirror 8 and the normal direction on the back of the main reflector 4, and adjust the main reflector 4 Make α ₁ consistent with α in step 1; set up two theodolites (T3, T5) for rendezvous and docking measurement to obtain the angle β ₁ between the normal direction of the second interferometer standard plane mirror 8 and the back surface of the third mirror 6, adjust the first Three reflecting mirrors 6 make β ₁ consistent with β in step 2);

7) The wave aberration of the off-axis four-mirror lens is detected in real time by using the self-aligning interferometry system. As shown in FIG. The third reflector 6 and the plane reflector 7 converge to the standard spherical mirror 9 and return to form interference fringes. The root mean square value (RMS value) of the system aberration measured by the high-precision interferometer after the initial installation and positioning is 0.263λ(λ =632.8nm), and then after four computer-aided adjustments, the image quality of each field of view meets the requirements. Practice has proved that this scheme has high positioning accuracy, which makes the adjustment convergence speed very fast, effectively improves the installation and adjustment efficiency, and shortens the installation and adjustment cycle.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (3)

1. a kind of initial installation location method of off-axis four-mirror lens, described off-axis four-mirror lens comprises main reflector (4), secondary reflector (5), the 3rd reflector (6), plane reflector ( 7), wherein the main reflector (4) and the third reflector (6) are off-axis aspheric reflectors (3); it is characterized in that comprising the following steps: 1) Utilize the first interferometer (1) and the zero compensator (2) to lead out the direction of the optical axis of the main reflector (4); set the incident surface of the light beam to the front of the main reflector (4), and use two theodolites to rendezvous and dock Measure the included angle α between the optical axis direction of the primary reflector (4) and the normal direction on the back of the primary reflector (4); 2) Utilize the first interferometer (1) and the zero position compensator (2) to draw the optical axis direction of the third reflector (6); set the incident surface of the light beam as the front of the third reflector (6), and use two theodolites Obtain the angle β between the optical axis direction of the third reflector (6) and the normal direction on the back of the third reflector (6) through the rendezvous and docking measurement; 3) Calculate and manufacture four long rods from the optical design data of the off-axis four-mirror lens. The material of the long rods is quartz glass with a low expansion coefficient. The four ends of the four long rods are all made into ball heads. The four balls The head positions respectively represent the central position of the incident field of view, the central position of the mirror surface of the primary reflector (4), the central position of the mirror surface of the secondary reflector (5) and the central position of the mirror surface of the third reflector (6); 4) Place four long rods on the adjustment bracket, adjust the height of the center point of the incident field of view and the center point of the secondary reflector (5), determine the sagittal plane of the central field of view, and adjust the secondary reflector (5) as a reference The main reflector (4) and the third reflector (6), until the center of each reflector surface contacts the ball head of the long rod; 5) Set the incident surface of the light beam on the front side of the main reflector (4), set up two theodolites for rendezvous and docking measurement to obtain the included angle α ₁ between the second interferometer standard plane mirror (8) and the normal direction on the back side of the main reflector (4), adjust Primary reflector (4) makes α ₁ consistent with α in step 1); 6) Let the incident surface of the light beam be the front of the third reflector (6), set up two theodolites for rendezvous and docking measurement to obtain the angle β1 between the second interferometer standard plane mirror (8) and the normal direction on the back of the third reflector ( ₆ ) , adjust the third reflector (6) so that β1 is consistent with β in step ₂ ); 7) The parallel light emitted by the second interferometer standard plane mirror (8) passes through the main reflector (4), the secondary reflector (5), the third reflector (6), and the plane reflector (7) of the off-axis four-mirror lens Finally, it returns to the standard spherical mirror (9) and forms interference fringes on the second interferometer standard flat mirror (8) to complete the initial installation and positioning of the off-axis four-mirror lens. 2. The method for initial installation and positioning of a kind of off-axis four-mirror lens according to claim 1, is characterized in that: the specific method of drawing out the optical axis direction in step 1) is: the first interferometer (1), zero The position compensator (2) and the main reflector (4) are placed in order from left to right. The plane wave emitted by the first interferometer (1) passes through the zero position compensator (2) and becomes an aspheric wave, and the aspheric wave is reflected by the main Mirror (4) returns according to the original path after reflection, and then returns to the first interferometer (1) after passing through the zero compensator (2), and adjusts the positions of the zero compensator (2) and the main reflector (4) until The numerical value measured by the first interferometer (1) is equal to the surface parameter value of the main reflector (4), and the positions of the zero position compensator (2) and the main reflector (4) are fixed, and now the main reflector (4) ) is parallel to the direction of light emitted by the first interferometer (1). 3. The method for initial installation and positioning of a kind of off-axis four-mirror lens according to claim 1, is characterized in that: the specific method of drawing out the optical axis direction in step 2) is: the first interferometer (1), zero The position compensator (2) and the third reflector (6) are placed sequentially from left to right, the plane wave emitted by the first interferometer (1) passes through the zero position compensator (2) and becomes an aspheric wave, and the aspheric wave is absorbed by the second After the three reflectors (6) are reflected, return according to the original path, and then return to the first interferometer (1) after passing through the zero compensator (2), and adjust the zero compensator (2) and the third reflector (6) position until the value measured by the first interferometer (1) is equal to the surface parameter value of the third reflector (6), and the positions of the zero position compensator (2) and the third reflector (6) are fixed, at this time The optical axis of the third reflecting mirror (6) is parallel to the direction of light emitted by the first interferometer (1).