A surface shape detection system of a concave ultra-thin self-adaptive deformable mirror

Abstract

The utility model discloses a kind of concave surface ultra-thin self-adapting deformation mirror's surface shape detection system, including open liquid storage tank, concave ultra-thin self-adapting deformation mirror, plane fold mirror, optical compensator, optical detection equipment, liftable object table, open liquid storage tank contains liquid, concave ultra-thin self-adapting deformation mirror utilizes its own concave cavity to make mirror body horizontally float in the liquid surface of open liquid storage tank, plane fold mirror is used for the light path fold of concave ultra-thin self-adapting deformation mirror and optical compensator, optical compensator and optical detection equipment are respectively set on liftable object table by supporting adjusting mechanism. The mirror surface support of the utility model is continuous, uniform support, and the high-frequency component in support deformation is small, without local support surface shape difference;The utility model can be adapted to different focal ratio ultra-thin self-adapting mirror, also can be used for gregorian type self-adapting deformation secondary mirror optical detection;The system can avoid tedious precision assembly and adjustment and calibration, shorten detection period, reduce measurement cost.

Description

Technical Field

[0001] This utility model belongs to the field of optical inspection technology, specifically an ultra-thin adaptive deformable mirror-shaped optical inspection system. Background Technology

[0002] Ground-based astronomical telescopes are susceptible to interference from the Earth's atmosphere. Specifically, the atmosphere interferes with the wavefronts of light waves emitted by celestial bodies and other objects, causing real-time distortion of the wavefronts that penetrate the atmosphere and resulting in image quality degradation. Adaptive optics technology can correct the distorted wavefronts of the observed target in real time based on the correction information of a standard target, resulting in sharper images and ultimately reducing the impact of atmospheric disturbances, thus improving the observation accuracy of ground-based astronomical telescopes.

[0003] Ultrathin adaptive deformable mirrors are one of the core components of adaptive optics technology. During their fabrication, surface shape information needs to be measured, and the measurement results guide the next step of processing. Common mirror support methods for surface shape detection include the following: The first method uses multi-point passive support. The drawback of this method is that when the ultrathin mirror is thin and lightweight, passive support struggles to evenly distribute the mirror's weight. This method can also create localized support spikes, and excessive actuators can cause significant ripples and undulations on the mirror surface.

[0004] The second method involves using modeling clay to bond the ultrathin mirror and the base mirror along their edges, leaving a gap between them. The ultrathin mirror and base mirror are then placed together on a V-shaped support, and their surface shape is measured using an interferometer. The drawback of this support method is that the stress distribution on the mirror surface is highly random, which can easily lead to bending deformation of the mirror surface.

[0005] The third approach involves installing a set of voice coil motors on the back of the mirror, applying a calculated correction force to correct the mirror's surface shape. For example, the deformable secondary mirror in a large binocular telescope (LBT) is an ultra-thin adaptive deformable secondary mirror, supported by a set of voice coil motors on its back. These motors provide correction force to correct deformation caused by the mirror's gravity. The drawbacks of this approach are threefold: First, the corrected surface shape will exhibit localized mid-to-high frequency surface shape aberrations (or "printing effect") near the voice coil motor locations. Second, as the mirror size increases, the number of voice coil motors required also increases, leading to a corresponding increase in the difficulty of installing, adjusting, and correcting the surface shape of the mirror support. Third, this approach requires bonding a certain number of metal blocks to the back of the mirror, which increases processing risk during the convergence stage of ultra-thin mirror polishing (multi-point support for a thin mirror needs to bear the weight of the entire polishing mold).

[0006] The fourth method involves bonding a set of magnets and micro-motion mechanisms to the back of the mirror. Based on the mirror's surface shape acquired by the interferometer, each micro-motion mechanism is manually adjusted to correct the mirror's deformation. The drawback of this method is that it can also produce localized surface shape aberrations (image distortion), and it requires manual estimation and trial adjustment, resulting in low accuracy. Other support methods include active mirror surface shape correction based on piezoelectric ceramics or piezoelectric ceramic stacks. The drawback of this method is that the piezoelectric ceramics require high driving voltage, and the driving and correction systems are complex and costly. Therefore, it is mainly used in small-aperture, ultra-thin, adaptive deformable mirrors. Utility Model Content

[0007] To overcome the shortcomings in optical inspection and support of ultrathin adaptive deformable mirrors, this invention provides a novel optical inspection and mirror support system for ultrathin adaptive deformable mirrors. Using the device of this invention, uniform support of the mirror surface can be achieved during the optical inspection of ultrathin adaptive deformable mirrors, and the detected surface shape is free from local surface shape differences caused by multi-point support, reducing the mid-to-high frequency (spatial) error components of mirror support deformation. The method of this invention is simple to operate and low in cost, and can be widely applied to the optical inspection (including interferometry or Shack-Hartmann wavefront sensing measurements) of ultrathin adaptive deformable mirrors with concave spherical, concave hyperboloid, concave parabolic, and concave ellipsoidal surfaces (and their even-order aspherical extensions), and can also be used for mirrors with central holes.

[0008] The technical solution of this utility model is as follows: A surface shape detection system for a concave ultrathin adaptive deformable mirror includes an open liquid storage tank, a concave ultrathin adaptive deformable mirror, a planar folding mirror, an optical compensator, an optical detection device, and a liftable platform. The open liquid storage tank contains liquid. The concave ultrathin adaptive deformable mirror uses its own concave cavity to make the mirror body float horizontally on the liquid surface of the open liquid storage tank, so that the back of the concave ultrathin adaptive deformable mirror is in contact with the liquid, while the front is not in contact with the liquid. The planar folding mirror is disposed in the optical path between the concave ultrathin adaptive deformable mirror and the optical compensator to realize the folding of the optical path. The optical compensator is disposed on the liftable platform through a first support adjustment mechanism. The optical detection device is disposed on the liftable platform behind the optical compensator through a second support adjustment mechanism.

[0009] Furthermore, the inner wall of the open liquid storage tank is provided with several pressure sensors along the circumference.

[0010] Furthermore, during testing, the end face of each pressure sensor contacts the end face of the concave ultrathin adaptive deformable mirror.

[0011] Furthermore, the gravity of the concave ultrathin adaptive deformable mirror is completely unloaded by liquid buoyancy, and no support mechanism is provided on the back of the concave ultrathin adaptive deformable mirror.

[0012] Furthermore, the types of the ultrathin adaptive deformable mirror include, but are not limited to, concave spherical mirrors, concave hyperboloid mirrors, concave parabolic mirrors, concave ellipsoidal mirrors, and even-order aspherical extended mirrors based thereon. When the ultrathin adaptive deformable mirror is a concave spherical mirror, the system does not include an optical compensator.

[0013] Furthermore, the type of the ultrathin adaptive deformable mirror includes an ultrathin adaptive deformable mirror with a central hole.

[0014] Furthermore, the optical compensator includes, but is not limited to, an optical compensator composed of a lens group, a computational holographic compensator, and a refractive-diffraction hybrid compensation system.

[0015] Furthermore, the optical detection equipment includes, but is not limited to, an interferometer and a Shaker-Hartmann wavefront sensing measurement system.

[0016] Compared with the traditional multi-point support method of optical detection, this utility model has the following advantages and features: (1) The convex surface of the mirror of this utility model is in contact with the liquid and is subjected to its buoyancy, which is equivalent to countless micro-element support points. The support is continuous, so the mirror support force is uniform, the mid-to-high frequency components in the support deformation are small, and there is no local support surface shape difference (printing effect).

[0017] (2) Under the condition that the convex surface of the mirror is not completely submerged (the weight of the maximum water displaced is greater than or equal to the weight of the mirror), the device can adapt to ultra-thin adaptive mirrors with different focal ratios.

[0018] (3) This device can test ultrathin adaptive mirrors that meet the liquid float conditions, and can be used for optical testing of Gregory type adaptive deformable secondary mirrors.

[0019] (4) This device is suitable for different types of optical detection, including interferometric detection, Shack-Hartmann wavefront sensing measurement, etc.

[0020] (5) The device is easy to operate. Compared with the active calibration of multi-point actuators, it avoids the tedious precision assembly and calibration, saves time and costs, and shortens the detection cycle. In addition, the device is simple to use and saves economic costs. Attached Figure Description

[0021] Figure 1 Schematic diagram of an ultrathin adaptive deformable mirror optical inspection system; Figure 2 Schematic diagram of the liquid buoyancy support of the ultrathin adaptive deformable mirror (side force sensors, etc. are not shown).

[0022] The markings in the diagram are: 1-open liquid storage tank; 2-liquid; 3-concave ultrathin adaptive deformable mirror; 4-pressure sensor; 5-planar folding mirror; 6-optical compensator; 7-first support adjustment mechanism; 8-optical detection equipment; 9-second support adjustment mechanism; 10-liftable platform; 11-central hole. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings.

[0024] This utility model discloses a surface shape detection system for a concave ultrathin adaptive deformable mirror, such as... Figure 1 As shown, it includes an open liquid storage tank 1, a concave ultrathin adaptive deformable mirror 3, a planar folding mirror 5, an optical compensator 6, an optical inspection device 8, and a liftable platform 10. Among them: The open reservoir 1 contains liquid 2. The concave ultrathin adaptive deformable mirror 3 is supported by the buoyancy of the liquid 2 on the mirror surface, so that the mirror surface reaches a static equilibrium state. That is, the mirror body floats horizontally on the liquid surface of the open reservoir 1 by its own concave cavity. The weight of the volume of liquid displaced by the mirror body (equal to the buoyancy) is sufficient to balance the weight of the mirror surface itself. At this time, the back of the concave ultrathin adaptive deformable mirror 3 is in contact with the liquid, while the front is not in contact with the liquid.

[0025] The surface shape of the concave ultrathin adaptive deformable mirror 3 is not limited to a concave sphere, but also includes concave hyperboloids, parabolic surfaces, ellipsoids, and even-order aspherical surfaces based on these, as well as cases with a central hole. The open liquid storage tank 1 contains a certain volume of liquid 2, which is not limited to water, but can also be kerosene or other usable liquid types that can generate sufficient buoyancy.

[0026] A planar folding mirror 5 is positioned in the optical path between the concave ultrathin adaptive deformable mirror 3 and the optical compensator 6 to achieve optical path folding. The planar folding mirror 5 can be adjusted via its matching adjustment mechanism. In this embodiment, the tilt angle of the planar folding mirror 5 is 45°.

[0027] The liftable platform 10 is equipped with a first support adjustment mechanism 7 and a second support adjustment mechanism 9. The first support adjustment mechanism 7 is located in front of the second support adjustment mechanism 9, closer to the planar folding mirror 5. An optical compensator 6 is mounted on the first support adjustment mechanism 7, and an optical detection device 8 is mounted on the second support adjustment mechanism 9.

[0028] Among them, the optical detection equipment 8 is not limited to an interferometer, but can also be a Shaker-Hartmann wavefront sensing and measurement system, a star point inspection device, etc. The optical compensator 6 is not limited to an optical compensator (or group) composed of lens groups, but can also be a computational holographic compensator or a refractive-diffraction hybrid compensation system.

[0029] With the assistance of the adjustable platform 10, the second support adjustment mechanism 9, the first support adjustment mechanism 7, and the planar folding mirror 5, the standard wavefront emitted by the optical testing equipment 8 passes through the optical compensator 6 (no optical compensator in the case of a spherical surface) and the planar folding mirror 5, finally reaching the concave ultrathin adaptive deformable mirror 3, and then returning to the optical testing equipment 8 along the same path. After measurement and data processing, the mirror surface shape of the concave ultrathin adaptive deformable mirror 3 is finally obtained.

[0030] The measurement method of the surface shape detection system for the concave ultrathin adaptive deformable mirror is as follows: Step 1: If the concave ultrathin adaptive deformable mirror 3 has a central hole, use transparent tape or thin waterproof tape to seal the central hole from the back of the mirror surface, so that the concave surface forms a complete, gapless space isolated from the liquid. If the ultrathin adaptive mirror does not have a central hole, skip this step; Step 2: Inject a certain volume of liquid 2 into the open liquid storage tank 1, and then rotate the four adjustable screws with waterproof pressure sensors 4 on the side of the open liquid storage tank 1 outward to ensure that the area enclosed by the end faces of the four sensors is larger than the diameter of the concave ultrathin adaptive deformable mirror 3 to be tested. Step 3: Place the concave ultrathin adaptive deformable mirror 3 into the liquid 2, and rotate the four adjustable screws with waterproof pressure sensors 4 on the side inward until the end faces of the four pressure sensors just touch the concave ultrathin adaptive deformable mirror 3. Step 4: Place the optical compensator 6 (compensation lens or computational hologram) and the first support adjustment mechanism 7 on the liftable stage 10, and place the optical detection equipment 8 (interferometer or Shaker-Hartmann wavefront sensing and other measurement systems) and the second support adjustment mechanism 9 on the liftable stage 10. Step 5: Adjust the liftable stage 10, the first support adjustment mechanism 7 and the second support adjustment mechanism 9 so that the optical detection equipment 8 (interferometer or Shaker-Hartmann wavefront sensing and other measurement systems), the optical compensator 6 (compensation lens or computational hologram), the plane folding mirror and the center of the adjustment mechanism are at the same height. At the same time, move and adjust the open liquid storage tank 1 so that the center of the incident beam is near the center of the concave ultrathin adaptive deformable mirror 3, and complete the coarse adjustment of the optical path. Step 6: Adjust the attitude of the first support adjustment mechanism 7, the second support adjustment mechanism 9, the planar folding mirror, and the adjustment mechanism so that the wavefront returning from the concave surface of the concave ultrathin adaptive deformable mirror 3 passes through the planar folding mirror 5 and the optical compensator 6 (compensation lens or computational hologram) and finally returns to the optical detection device 8 (interferometer or Shaker-Hartmann wavefront sensing and other measurement systems), while ensuring the integrity of the measurement area and completing the fine adjustment of the optical path; Step 7: Measure the concave ultrathin adaptive deformable mirror 3 using optical testing equipment 8 (interferometer or Shaker-Hartmann wavefront sensing measurement system, etc.). Complete the mirror surface measurement through data acquisition and analysis.

[0031] The following example demonstrates liquid-float interferometry measurement of a concave ultrathin adaptive spherical mirror.

[0032] The mirror aperture D2 = 500 mm, the central hole 11 diameter D3 = 80 mm, the thickness d = 2 mm, and the mirror material is microcrystalline glass. First, it is necessary to calculate to ensure that the weight of the displaced liquid is greater than or equal to the weight of the mirror under maximum displacement conditions, i.e.:

[0033] In the above formula, V 液 The maximum displaceable liquid volume, i.e. Figure 2 The volume of a frustum with diameters D2 and D3 at its upper and lower base circles, and a height of H2, is ρ. 液 Given the density of the selected liquid, water is chosen in this example. V 玻 The volume of the concave ultrathin adaptive spherical mirror, i.e. Figure 2 The volume of the thin spherical shell with upper and lower base diameters of D2 and D3 respectively, and a thickness of d = 2 mm, is given. Different liquids, such as water and kerosene, can be chosen to minimize the deformation of the liquid-buoyed support while maintaining the above formula.

[0034] Then, use transparent tape or thin waterproof tape to seal the central hole from the back, creating a completely sealed space isolated from the liquid. The tape must be sealed without gaps, and the tape inside the central hole should be slightly slack to avoid additional tension. Next, fill the open reservoir 1 with water to a certain height, and rotate the four adjustable screws with waterproof pressure sensors 4 on the side of the reservoir 1 outwards, making the diameter of the circle enclosed by the four sensor faces approximately 530 mm, ensuring it is larger than the aperture of the ultrathin adaptive mirror under test. Gently place the concave ultrathin adaptive spherical mirror into the water, and rotate the four adjustable screws with waterproof pressure sensors 4 inwards until the end faces of the four pressure sensors just touch the ultrathin adaptive mirror. Observe the pressure sensor readings; if there are non-zero data, then retract each adjusting screw by 0.1 mm (this can be monitored with a dial indicator). Next, place the dynamic polarization phase-shifting interferometer and its second support adjustment mechanism 9 on the liftable stage 10 (in this example, a spherical mirror without an optical compensation system). Adjust the liftable stage 10 and the second support adjustment mechanism 9 to make the center of the interferometer (in this example, a dynamic polarization phase-shifting interferometer) and the coated planar microcrystalline glass folding mirror and its adjustment mechanism at the same height. At the same time, move the open water tank 1 so that the center of the incident beam is near the center of the concave ultrathin adaptive spherical mirror, thus completing the coarse adjustment of the optical path.

[0035] Next, the orientation of the second support adjustment mechanism 9 and the coated planar microcrystalline glass folding mirror and its adjustment mechanism are adjusted to ensure that the wavefront returning from the working surface (concave surface) of the concave ultrathin adaptive spherical mirror returns to the dynamic polarization phase-shifting interferometer via the planar folding mirror, thus completing the measurement area and fine-tuning the optical path. Finally, the interferometer is used to measure the concave ultrathin adaptive spherical mirror to complete the mirror surface measurement.

[0036] In summary, this invention provides a surface shape detection system for a concave ultrathin adaptive deformable mirror. The system includes an optical detection device, an optical compensation system, a planar folding mirror, the concave ultrathin adaptive deformable mirror under test, and an auxiliary assembly and adjustment mechanism. The concave ultrathin adaptive deformable mirror is suspended in a liquid and reaches a static equilibrium state with uniform support. The standard wavefront emitted by the optical detection device is reflected by the concave ultrathin adaptive deformable mirror under test through the optical compensation system and the planar folding mirror, and finally returns to the optical detection device along the original path. The surface shape of the concave ultrathin adaptive deformable mirror can be obtained through data acquisition and processing. The mirror support of this invention is continuous and uniform, with small mid-to-high frequency components in the support deformation and no local support surface shape differences. This system can adapt to ultrathin adaptive mirrors with different focal ratios and can also be used for the optical detection of Gregory-type adaptive deformable secondary mirrors. The system is simple and economical to operate, avoids cumbersome precision assembly and calibration, shortens the detection cycle, and reduces measurement costs.

[0037] The above embodiments are merely typical implementations of this utility model and are not intended to limit the scope of this utility model. All equivalent substitutions or improvements made within the scope of the claims of this utility model are protected by this utility model.

Claims

1. A surface shape detection system for a concave ultrathin adaptive deformable mirror, characterized in that: The system includes an open liquid storage tank, a concave ultrathin adaptive deformable mirror, a planar folding mirror, an optical compensator, an optical detection device, and a liftable platform. The open liquid storage tank contains liquid. The concave ultrathin adaptive deformable mirror uses its own cavity to make the mirror body float horizontally on the liquid surface of the open liquid storage tank, so that the back of the concave ultrathin adaptive deformable mirror is in contact with the liquid, while the front is not in contact with the liquid. The planar folding mirror is set in the optical path between the concave ultrathin adaptive deformable mirror and the optical compensator to realize the folding of the optical path. The optical compensator is set on the liftable platform through a first support adjustment mechanism. The optical detection device is set on the liftable platform behind the optical compensator through a second support adjustment mechanism.

2. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: Several pressure sensors are arranged circumferentially on the inner wall of the open liquid storage tank.

3. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 2, characterized in that: During testing, the end face of each pressure sensor is in contact with the end face of the concave ultrathin adaptive deformable mirror.

4. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: The gravity of the concave ultrathin adaptive deformable mirror is completely unloaded by liquid buoyancy, and no support mechanism is set on the back of the concave ultrathin adaptive deformable mirror.

5. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: The types of ultrathin adaptive deformable mirrors include, but are not limited to, concave spherical mirrors, concave hyperboloid mirrors, concave parabolic mirrors, concave ellipsoidal mirrors, and even-order aspherical extended mirrors based on these. When the ultrathin adaptive deformable mirror is a concave spherical mirror, the system does not include an optical compensator.

6. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: The types of ultrathin adaptive deformable mirrors include ultrathin adaptive deformable mirrors with a central aperture.

7. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: The optical compensator includes, but is not limited to, an optical compensator composed of lens groups, a computational holographic compensator, and a refractive-diffraction hybrid compensation system.

8. The surface shape detection system for a concave ultrathin adaptive deformable mirror according to claim 1, characterized in that: The optical detection equipment includes, but is not limited to, interferometers and Shaker-Hartmann wavefront sensing measurement systems.

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