Method for precise adjustment and focal plane determination of a secondary focusing curved mirror based on multi-aperture encoding

Abstract

The application discloses a kind of based on the method for precisely adjusting and determining focal plane of secondary focusing curved mirror of multi-aperture coding, will continuous laser source as probe light, through multi-aperture coding board generates different spatial positions of multiple beamlets, utilize the difference of different beamlets affected by the difference of misadjustment, realize the efficient adjustment of secondary focusing curved mirror by observing the difference of each beam spot, simultaneously, combined with cut focal point method, the focal plane position of secondary focusing curved mirror under ideal adjustment can be determined synchronously.The application solves the precision problem of the adjustment and determination of focal plane of traditional secondary focusing curved mirror, and has important application prospect for the establishment of various optical systems using secondary focusing curved mirror device.The application innovatively proposes the combination of multi-aperture and cut focal point method, to realize high-precision adjustment of secondary focusing curved mirror and determine its focal plane position.

Description

Technical Field

[0001] The present invention belongs to the field of precision adjustment of optical devices, and in particular relates to a method for adjusting a secondary focusing curved mirror and determining a focal plane. Background Art

[0002] The secondary focusing curved mirror is a reflective optical device with two focal points. The light beam confocal with the front focus must converge at the rear focus after reflection, so secondary focusing can be achieved, effectively changing the numerical aperture of the laser. When the rear focus is distinguished by real and virtual, it is an ellipsoidal mirror and a hyperbolic mirror respectively. Under ideal conditions, the secondary focusing curved mirror has the advantages of large numerical aperture, strong contrast, and good imaging effect. It is widely used in the fields of astronomical telescopes, microscopy, optical precision measurement, and various systems, and has extremely high application prospects and commercial value. At the same time, because the focal spot size can be effectively reduced, the secondary focusing curved mirror can also be used in various high-energy physics experiments, significantly improving the focusing power density of the laser.

[0003] However, due to its off-axis characteristics and large collection aperture angle, the secondary focusing curved mirror requires extremely high adjustment accuracy, and has many coupled adjustment dimensions. A slight misalignment will introduce large coma and astigmatism, resulting in a significant decrease in imaging effect or focusing power density. Therefore, the secondary focusing curved mirror must be precisely assembled and adjusted. Existing off-axis device adjustment methods mainly use cameras to observe the focus for imaging. For example, off-axis parabolic mirrors can eliminate astigmatism through light spots before and after the focus, but this method is only applicable to optical elements with a small number of dimensions of adjustment. When used for secondary focusing curved mirrors, its adjustment is extremely difficult and the accuracy cannot be guaranteed. At the same time, when the secondary focusing curved mirror is used for zooming, the shorter Rayleigh length will make it more difficult to determine the focal plane position. Summary of the Invention

[0004] To address the shortcomings of the aforementioned prior art, the present invention provides a method for adjusting and determining the focal plane of a secondary focusing curved mirror based on multi-aperture coding. This method utilizes the fact that sub-beams at different spatial locations are differentially affected by the misalignment of the secondary focusing curved mirror. By observing these differences in the sub-beams, high-precision and rapid adjustment of the secondary focusing curved mirror is achieved. Furthermore, by combining multiple beams with the traditional tangent focus method, the focal plane position of the secondary focusing curved mirror under ideal adjustment is synchronously determined by determining the tangent spot results of each sub-beam.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] On the one hand, the present invention provides a method for adjusting a secondary focusing curved mirror based on multi-aperture coding, which is characterized by the following steps:

[0007] S1. Build the optical path

[0008] S1.1 Direct a continuous laser light source into an off-axis parabolic mirror, adjust the off-axis parabolic mirror to achieve ideal focus without aberration, and use a camera equipped with an imaging lens to image the focus of the off-axis parabolic mirror and record the initial focal spot.

[0009] S1.2 Place the multi-aperture code plate in the optical path between the continuous laser light source and the off-axis parabolic mirror, so that multiple circular sub-beams are generated at different positions in space;

[0010] S1.3 placing a secondary focusing curved mirror, wherein the front focus of the secondary focusing curved mirror coincides with the focus of the off-axis parabolic mirror, imaging the back focus of the secondary focusing curved mirror using a camera, and recording a secondary image;

[0011] Adjustment of S2 secondary focusing curved mirror

[0012] S2.1 adjusts the secondary focusing curved mirror by observing the images of multiple sub-beams in the camera, so that the sub-beams form an ideal circular distribution near the focal plane;

[0013] S2.2 removes the multi-aperture coding plate, uses a camera to record the focal spot after secondary focusing, and calculates the actual magnification ratio based on the imaging ratio and the initial focal spot;

[0014] S2.3 Change the horizontal angle of the secondary focusing curved mirror, reinsert the multi-aperture coding plate, slightly adjust the secondary focusing curved mirror, and repeat the above steps until the desired secondary focusing magnification ratio is obtained.

[0015] Furthermore, by observing the images of the multiple sub-beams in the camera, the secondary focusing curved mirror is adjusted so that the sub-beams are distributed in an ideal circle near the focal plane. The specific adjustment process is as follows:

[0016] S2.1.1 When all sub-beams are tilted in the opposite direction before and after focus, adjust the height of the secondary focusing curved mirror to eliminate the tilt;

[0017] S2.1.2 When all sub-beams appear to be reversely elliptical and flattened at the pre-focus and post-focus positions, adjust the front-to-back direction of the secondary focusing curved mirror to make the beams tend to be circular; at the same time, observe the sub-beams at the upper and lower positions. If any tilt relative to the central sub-beam occurs, adjust the horizontal direction of the secondary focusing curved mirror to eliminate the tilt;

[0018] S2.1.3 Slowly move the camera to image the focus of the light beam. During the movement, if the sub-beam becomes misaligned again, repeat steps S2.1.1-S2.1.2, and couple and adjust the three-dimensional translation direction of the secondary focusing curved mirror until all sub-beams are distributed in an ideal circle at the focal plane position.

[0019] On the other hand, the present invention also provides a method for determining the focal plane of a secondary focusing curved surface mirror based on multi-aperture coding, including the above-mentioned adjustment method of the secondary focusing curved surface mirror, which is characterized in that it also includes: using a light-blocking plate to block part of the light propagation near the focal position of the secondary focusing curved surface mirror, and using a moving-in and moving-out focus cutting method to determine the focal plane position of the secondary focusing curved surface mirror.

[0020] Furthermore, the light blocking sheet is used to block the propagation of part of the light near the focal position of the secondary focusing curved mirror, and the focal plane position of the secondary focusing curved mirror is determined by using a moving-in and moving-out tangent focus method, specifically:

[0021] Cut the light shield from a specific direction, and observe the sub-beams closest and farthest from the light shield in the near field during the cutting process; when the near sub-beam is cut first, it indicates that the light shield is in the pre-focus position and needs to be moved backward; when the far sub-beam is cut first, it indicates that the light shield is in the pre-focus position and needs to be moved forward; repeat the above steps until all sub-beams are cut at the same time.

[0022] Preferably, the light blocking sheet is a thin sheet with sharp sides, placed perpendicular to the incident direction of the light beam, and equipped with a two-dimensional translation device in the front-back and left-right directions; the translation device in the front-back direction is used to change the defocus position of the light blocking sheet, and the translation device in the left-right direction is used to move in and out to realize the focus cutting function.

[0023] The continuous laser light source is vertically incident on the multi-aperture coding plate to generate multiple circular sub-beams at different positions in space;

[0024] The off-axis parabolic mirror is used to focus the light beam;

[0025] The secondary focusing curved mirror is used to secondary focus the light beam after being focused by the off-axis parabolic mirror;

[0026] The light blocking plate is used to block the light beam in and out at the focal position to determine the focal plane position;

[0027] The imaging lens and camera are used to magnify and image the sub-beam at the focal position behind the secondary focusing curved mirror, and the misalignment direction is judged and adjusted in real time by observing the magnified imaging image of the sub-beam.

[0028] The continuous laser light source needs to be incident normally through the multi-aperture coding plate and the off-axis parabolic mirror, and the focus after being focused by the off-axis parabolic mirror should be an ideal focus without aberration.

[0029] The secondary focusing curved mirror is equipped with a three-dimensional translation and a two-dimensional pitch adjustment device for adjusting the posture of the secondary focusing curved mirror.

[0030] The imaging lens is fixedly connected to the camera, and the camera is equipped with a front-back translation device for changing the imaging position.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1) By leveraging the differential misalignment characteristics of a secondary focusing curved mirror for beams at different spatial positions and observing the differences in the spot size of each sub-beam, high-precision adjustment of the mirror is achieved. Combined with the tangent focus method, the focal plane position can be simultaneously determined. This method effectively achieves rapid adjustment of the secondary focusing curved mirror, is simple to operate, and is easy to integrate. Only a few optical components are required to achieve misalignment adjustment of the secondary focusing curved mirror.

[0033] 2) Both multi-aperture and tangent point modulation can be moved in and out without affecting the main optical path.

[0034] 3) This method can accurately determine the focal position synchronously during the adjustment process, greatly reducing the adjustment error and adjustment time in beam-target coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : Schematic diagram of the principle of the method for precise adjustment and focal plane determination of the secondary focusing curved mirror based on multi-aperture coding;

[0036] Figure 2 : Schematic diagram of sub-beams generated by a multi-aperture coding plate.

[0037] In the figure, 1. continuous laser light source; 2. multi-aperture coding plate; 3. off-axis parabolic mirror; 4. secondary focusing curved mirror; 5. light shield; 6. imaging lens; 7. camera. DETAILED DESCRIPTION

[0038] In order to make the implementation objectives, technical solutions and technical effects of the present invention clearer, the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments. In the description of this application, it should be understood that the terms "front", "rear", "right", "upper", "vertical", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting this application.

[0039] This embodiment provides a method for precise adjustment and focal plane determination of a secondary focusing curved mirror based on multi-aperture coding, wherein an ellipsoidal mirror is selected as the secondary focusing curved mirror. Figure 1As shown in the figure, it includes a continuous laser light source 1, a multi-aperture code plate 2, an off-axis parabolic mirror 3, a secondary focusing curved mirror 4, a light shield 5, an imaging lens 6, and a camera 7. The continuous laser light source 1 passes through the multi-aperture code plate 2, is then reflected and focused by the off-axis parabolic mirror 3, and is secondary focused by the secondary focusing curved mirror 4 before being incident on the camera 7. The imaging lens 6 is fixed to the camera 7, and the light shield 5 is located near the secondary focus of the secondary focusing curved mirror 4.

[0040] Select a multi-aperture code plate with five sub-apertures, refer to Figure 2 The system comprises a continuous laser light source 1 and a multi-aperture coding plate 2. The continuous laser light source 1 generates five sub-beams through the multi-aperture coding plate 2, wherein beam III is the central beam, beams II and IV are located to the left and right of beam III, and beams I and V are located above and below beam III.

[0041] The specific steps are as follows:

[0042] Phase 1: Light path construction

[0043] 1. A continuous laser light source 1 is incident on an off-axis parabolic mirror 3. A camera 7 is used to image the focus of the off-axis parabolic mirror 3, complete the ideal adjustment of the off-axis parabolic mirror 3, and record the initial focal spot.

[0044] 2. Place a multi-aperture coding plate 2 with five sub-apertures between the continuous laser light source 1 and the off-axis parabolic mirror 3 to generate five sub-beams.

[0045] 3. Place the secondary focusing curved mirror 4 so that its front focus coincides with the focus of the off-axis parabolic mirror 3. The camera 7 images the back focus of the secondary focusing curved mirror 4 and records the secondary image.

[0046] Second stage: Secondary focusing curved mirror adjustment

[0047] 1. By observing the image of sub-beam I-V, the secondary focusing curved mirror is adjusted according to the image of the sub-beam so that the sub-beams I-V form an ideal circular distribution near the focal plane;

[0048] 2. Remove the multi-aperture encoding plate, and the camera records the focal spot after secondary focusing. It then calculates the actual magnification ratio based on the imaging ratio and the initial focal spot.

[0049] 3. Based on the actual magnification ratio required, change the horizontal angle of the secondary focusing curved mirror, re-introduce the multi-aperture encoder plate, and slightly adjust the secondary focusing curved mirror. Repeat the above steps to obtain the desired secondary focusing magnification ratio.

[0050] Stage 3: Determine the focal plane position of the quadratic mirror

[0051] 1. A light blocker is added to the rear focal plane of the secondary focusing curved mirror, and the surface of the light blocker is perpendicular to the incident direction of the light beam.

[0052] 2. Determine the operation method according to the focal plane of the secondary focusing curved mirror in the technical solution, and use the light blocking plate to move in and out of the cutting focus to find the focal plane position of the secondary curved mirror.

[0053] Experiments have shown that this invention uses a continuous laser light source as a probe light, and generates multiple sub-beams in different spatial positions through a multi-aperture coding plate. By utilizing the differences in the effects of misalignment on different sub-beams and observing the differences in the light spots of each sub-beam, efficient adjustment of the secondary focusing curved mirror is achieved. At the same time, combined with the tangent point method, the focal plane position of the secondary focusing curved mirror under ideal adjustment can be synchronously determined. This invention solves the problem of adjusting the traditional secondary focusing curved mirror and determining the accuracy of the focal plane, and has important application prospects for the construction of various optical systems using secondary focusing curved mirror devices. The present invention innovatively proposes a combination of multi-aperture and tangent point methods to achieve high-precision adjustment of the secondary focusing curved mirror and determine its focal plane position.

[0054] The present invention is mainly used to solve the problems of adjustment and focal plane determination of the secondary focusing curved mirror, reducing the difficulty and tediousness of adjustment in the traditional adjustment method. According to the technology described in the present invention, high-precision adjustment of the secondary focusing curved mirror and determination of its focal plane position can be achieved, providing a new adjustment scheme for high-precision adjustment of the secondary focusing curved mirror. Although certain embodiments have been described, these embodiments are only presented as examples and are not intended to limit the scope of protection. Although the invention has been described in detail with reference to the aforementioned examples, for those skilled in the art, it is still possible to modify the schemes recorded in the aforementioned examples, or to make equivalent substitutions for some of the technical features therein. All modifications, equivalent substitutions, etc. made within the spirit and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A method for adjusting a secondary focusing curved mirror based on multi-aperture coding, characterized in that: Here are the steps: S1. Build the optical path S1.1 Direct a continuous laser light source into an off-axis parabolic mirror, adjust the off-axis parabolic mirror to achieve ideal focus without aberration, and use a camera equipped with an imaging lens to image the focus of the off-axis parabolic mirror and record the initial focal spot. S1.2 Place the multi-aperture code plate in the optical path between the continuous laser light source and the off-axis parabolic mirror, so that multiple circular sub-beams are generated at different positions in space; S1.3 placing a secondary focusing curved mirror, wherein the front focus of the secondary focusing curved mirror coincides with the focus of the off-axis parabolic mirror, imaging the back focus of the secondary focusing curved mirror using a camera, and recording a secondary image; Adjustment of S2 secondary focusing curved mirror S2.1 adjusts the secondary focusing curved mirror by observing the images of multiple sub-beams in the camera, so that the sub-beams form an ideal circular distribution near the focal plane; S2.2 removes the multi-aperture coding plate, uses a camera to record the focal spot after secondary focusing, and calculates the actual magnification ratio based on the imaging ratio and the initial focal spot; S2.3 Change the horizontal angle of the secondary focusing curved mirror, reinsert the multi-aperture coding plate, slightly adjust the secondary focusing curved mirror, and repeat the above steps until the desired secondary focusing magnification ratio is obtained.

2. The adjustment method of the secondary focusing curved mirror based on multi-aperture coding according to claim 1, characterized in that: By observing the images of the multiple sub-beams in the camera, the secondary focusing curved mirror is adjusted so that the sub-beams are distributed in an ideal circle near the focal plane. The specific adjustment process is as follows: S2.1.1 When all sub-beams are tilted in the opposite direction before and after focus, adjust the height of the secondary focusing curved mirror to eliminate the tilt; S2.1.2 When all sub-beams appear to be reversely elliptical and flattened at the pre-focus and post-focus positions, adjust the front-to-back direction of the secondary focusing curved mirror to make the beams tend to be circular; at the same time, observe the sub-beams at the upper and lower positions. If any tilt relative to the central sub-beam occurs, adjust the horizontal direction of the secondary focusing curved mirror to eliminate the tilt; S2.1.3 Slowly move the camera to image the focus of the light beam. During the movement, if the sub-beam becomes misaligned again, repeat steps S2.1.1-S2.1.2, and couple and adjust the three-dimensional translation direction of the secondary focusing curved mirror until all sub-beams are distributed in an ideal circle at the focal plane position.

3. A method for determining the focal plane of a secondary focusing curved mirror based on multi-aperture coding, comprising the method for adjusting the secondary focusing curved mirror according to claim 1 or 2, characterized in that: It also includes: using a light blocking plate to block the propagation of part of the light near the focal position of the secondary focusing curved mirror, and using a moving-in and moving-out focus cutting method to determine the focal plane position of the secondary focusing curved mirror.

4. The method for determining the focal plane of a secondary focusing curved mirror based on multi-aperture coding according to claim 3, characterized in that: The light blocking plate is used to block the propagation of part of the light near the focal position of the secondary focusing curved mirror, and the focal plane position of the secondary focusing curved mirror is determined by using a moving-in and moving-out tangent focus method, specifically: Cut the light shield from a specific direction, and observe the sub-beams closest and farthest from the light shield in the near field during the cutting process; when the near sub-beam is cut first, it indicates that the light shield is in the pre-focus position and needs to be moved backward; when the far sub-beam is cut first, it indicates that the light shield is in the pre-focus position and needs to be moved forward; repeat the above steps until all sub-beams are cut at the same time.

5. The method for determining the focal plane of a secondary focusing curved mirror based on multi-aperture coding according to claim 3, characterized in that: The light blocking sheet is a thin sheet with sharp sides, placed perpendicular to the incident direction of the light beam, and equipped with a two-dimensional translation device in the front-back and left-right directions; the translation device in the front-back direction is used to change the defocus position of the light blocking sheet, and the translation device in the left-right direction is used to move in and out to realize the focus cutting function.

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