Large aperture telescope high dynamic camera seeing detection system and detection method

Abstract

The present application relates to the field of seeing detection, and particularly relates to a large aperture telescope high dynamic camera seeing detection system and a detection method, wherein the detection system comprises: a fiber laser for emitting a detection beam; a mirror group distributed around the top of a to-be-detected mirror surface for reflecting the detection beam multiple times so that the detection beam passes through the detection area of the to-be-detected mirror surface multiple times; a microlens array for dividing the distorted wavefronts passing through the detection area of the to-be-detected mirror surface multiple times into a plurality of distorted sub-wavefronts and focusing the distorted sub-wavefronts onto a CCD detector array; the CCD detector array, wherein the CCD detectors are arranged in steps, for receiving the defocused and non-defocused distorted sub-wavefronts and obtaining different degrees of spot intensity; a neural network taking different spot intensities as input and camera seeing Zernike solution as output, and finally obtaining the camera seeing. The present application can perform wide-range seeing detection and has the characteristics of large flux and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of seeing testing technology, and in particular to a seeing detection system and method for a large-aperture telescope with a high dynamic range camera. Background Technology

[0002] Seeing is a physical quantity used to describe the degree to which an astronomical target appears blurred and flickering due to atmospheric turbulence. Essentially, it is the optical path difference between the wavefront after passing through turbulence and the ideal wavefront. One type of seeing is specular seeing, which mainly refers to the deterioration of image quality caused by turbulence on the surface of a mirror.

[0003] The existing method for detecting mirror seeing is the autocollimator method. This method utilizes the fact that light emitted by an electronic autocollimator passes through the turbulent region of the mirror surface, is reflected by a plane mirror, and is then received again by the autocollimator. The seeing of the portion of the beam that passed through is then calculated by the angular deviation between the direction of the turbulence and the emitted and received light. Increasing the number of electronic autocollimators can expand the area for seeing measurement. This type of seeing measurement device can measure the seeing of a certain volume through which light passes, and it is relatively simple to use, requiring only one electronic autocollimator and a reflecting mirror. However, this measurement device has a major drawback—the measurement area is limited. A single measurement can only obtain the average seeing within its aperture area. Even when using multiple electronic autocollimators, the sampling frequency and stitching issues still need to be considered, making it difficult to obtain a large-scale mirror seeing distribution in rapidly changing mirror turbulence. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a seeing detection system and method for a large-aperture telescope with a high dynamic range camera. The influence of the detection beam on the wavefront after passing through the area under test is projected onto the same plane. By obtaining the shape of the wavefront passing through the area under test, the seeing distribution of the entire mirror surface can be inverted, enabling large-scale seeing detection.

[0005] The present invention provides a high dynamic range camera seeing detection system for large-aperture telescopes, comprising: a fiber laser for emitting a detection beam; a mirror array distributed above and around the mirror under test for reflecting the detection beam multiple times, allowing the beam to pass through the detection area of ​​the mirror under test multiple times; a microlens array for dividing the distorted wavefront that has passed through the detection area of ​​the mirror under test multiple times into multiple distorted sub-wavefronts and focusing them onto a CCD detector array; a CCD detector array in which CCD detectors are arranged in a stepped manner to receive defocused and undefocused distorted sub-wavefronts to obtain different degrees of spot intensity; and a neural network that takes different spot intensities as input and the Zernike solution of camera seeing as output to finally obtain the camera seeing.

[0006] Preferably, a ground glass is arranged between the microlens array and the CCD detector array to increase nonlinearity and reduce complexity of the neural network.

[0007] The large-aperture telescope camera seeing detection method provided by the application is realized by using the large-aperture telescope high-dynamic camera seeing detection system, and the detection method comprises the following steps: a detection light beam is emitted by a fiber laser, the detection light beam is reflected by a mirror group, passes through the detection area of a to-be-detected mirror surface multiple times, and a distorted wavefront is generated due to the influence of turbulence; the distorted wavefront is divided into a plurality of distorted sub-wavefronts by a microlens array and focused on a CCD detector arranged in a step; the intensity of the light spots of different degrees is obtained and input into a neural network; and the Zernike solution output by the neural network is the camera seeing.

[0008] Preferably, the power spectrum of each pixel of the CCD detector is solved, all the power spectra are fitted to obtain a cutoff frequency, and the size of the spatial scale feature is determined by the cutoff frequency; the smaller the spatial scale feature, the greater the wavefront distortion; and the greater the spatial scale feature, the smaller the wavefront distortion.

[0009] Compared with the prior art, the application projects the influence of the detection light beam passing through the detected area on the wavefront onto the same plane, inversely calculates the seeing distribution of the entire mirror surface by obtaining the shape of the wavefront passing through the detected area, can detect the seeing in a large range, and has the characteristics of large flux and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 FIG. 1 is a structural schematic diagram of a large-aperture telescope high-dynamic camera seeing detection system provided by an embodiment of the application.

[0011] The reference signs: distorted wavefront 1, microlens array 2, CCD detector array 3, neural network 4. DETAILED DESCRIPTION

[0012] Hereinafter, embodiments of the application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference signs. In the case of the same reference signs, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0013] In order to make the purpose, technical solutions and advantages of the application more clear, the application will be further described in detail below by combining with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and do not constitute a limitation on the application.

[0014] Figure 1 FIG. 1 is a structural schematic diagram of a large-aperture telescope high-dynamic camera seeing detection system provided by an embodiment of the application.

[0015] As shown in Figure 1 The large-aperture telescope high-dynamic camera seeing detection system provided by the embodiment of the application comprises a distortion wavefront 1, a microlens array 2, a CCD detector array 3, a neural network 4, a fiber laser, and a mirror group.

[0016] The fiber laser is used to emit a detection beam, and the incident wavefront of the detection beam is not distorted before encountering turbulence.

[0017] The mirror group is distributed around the to-be-detected mirror surface and is used to reflect the detection beam multiple times so that the detection beam passes through the detection area of the to-be-detected mirror surface multiple times, and the incident wavefront is distorted when passing through the detection area of the to-be-detected mirror surface due to the influence of turbulence.

[0018] As an alternative, the mirror group can be replaced by two larger mirrors to achieve more intensive detection.

[0019] The microlens array 2 is used to divide the distortion wavefront into multiple distortion sub-wavefronts, and each distortion sub-wavefront forms an image on the CCD detector array 3.

[0020] The CCD detector array 3 is composed of multiple CCD detectors arranged in steps and is used to receive defocused (including pre-focal and post-focal) and non-defocused distortion sub-wavefronts, and the image formed by each distortion sub-wavefront has different spot intensities, thereby obtaining different degrees of spot intensity.

[0021] The neural network 4 takes different spot intensities as input and takes the camera seeing Zernike solution as output, and is constructed in this way.

[0022] The spot intensity of the image formed by each distortion sub-wavefront is input to the neural network 4, and the output Zernike solution is obtained, thereby obtaining the mirror surface seeing of the camera.

[0023] The large-aperture telescope camera seeing detection method provided by the application is implemented by using the above large-aperture telescope high-dynamic camera seeing detection system, and the detection method comprises the following steps: emitting a detection beam by a fiber laser, reflecting the detection beam by a mirror group, passing the detection area of a to-be-detected mirror surface multiple times, distorting the incident wavefront due to the influence of turbulence, dividing the distortion wavefront into multiple distortion sub-wavefronts by a microlens array, focusing the distortion sub-wavefronts on a CCD detector arranged in steps, obtaining different degrees of spot intensity, inputting the spot intensity to a neural network, and outputting the Zernike solution of the neural network as the camera seeing.

[0024] The power spectrum of each CCD detector is solved, all power spectra are fitted to obtain a cutoff frequency, the size of the spatial scale feature is determined by the cutoff frequency, the smaller the spatial scale feature, the greater the wavefront distortion, and the greater the spatial scale feature, the smaller the wavefront distortion.

[0025] It should be understood that the various forms of flow shown above can be used to reorder, add, or remove steps. For example, the steps recited in the present disclosure can be performed in parallel, in series, or in a different order, as long as the desired results of the present disclosure are achieved, which is not limited herein.

[0026] The specific implementation described above does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A seeing detection system for a high dynamic range camera on a large-aperture telescope, characterized in that, include: Fiber lasers are used to emit detection beams; The reflector group is distributed above and around the mirror surface to be tested, and is used to reflect the detection beam multiple times, so that the detection beam passes through the detection area of ​​the mirror surface to be tested multiple times. Microlens arrays are used to divide the distorted wavefront of the detection area that has passed through the mirror under test multiple times into multiple distorted sub-wavefronts and focus them onto the CCD detector array. A CCD detector array, in which the CCD detectors are arranged in a stepped manner, is used to receive the defocused and undefocused distorted wavefronts to obtain different degrees of light spot intensity. The neural network takes different light spot intensities as input and the Zernikal solution of camera seeing as output, and finally obtains the camera seeing.

2. The seeing detection system for a large-aperture telescope high dynamic range camera according to claim 1, characterized in that, A frosted glass is placed between the microlens array and the CCD detector array to increase nonlinearity and reduce the complexity of the neural network.

3. A method for detecting seeing using a high dynamic range camera on a large-aperture telescope, implemented using the high dynamic range camera seeing detection system for a large-aperture telescope as described in claim 1 or 2, characterized in that... include: A detection beam is emitted by a fiber laser. The detection beam is reflected by a group of mirrors and passes through the detection area of ​​the mirror under test multiple times. The incident wavefront is distorted by turbulence. The distorted wavefront is divided into multiple distorted sub-wavefronts by a microlens array and focused onto a CCD detector arranged in a stepped pattern. Different degrees of spot intensity are obtained and input into a neural network. The Zernike solution output by the neural network is the camera seeing.

4. The method for detecting seeing using a high dynamic range camera on a large-aperture telescope according to claim 3, characterized in that, The power spectrum of the data collected by each CCD detector pixel is calculated, and the cutoff frequency is obtained by fitting all the power spectra. The magnitude of the spatial scale feature is determined by the cutoff frequency. The smaller the spatial scale feature, the greater the wavefront distortion, and the greater the spatial scale feature, the smaller the wavefront distortion.

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