A frequency response test device and method for a high-frequency deformable mirror

Abstract

The present application discloses a frequency response test device and method for a high-frequency deformable mirror, which relates to the field of adaptive optics technology. The device comprises: a pulse signal generator generates a pulse signal of a first frequency and a pulse signal of a second frequency, wherein the first frequency is equal to the working frequency of the deformable mirror, and the second frequency is equal to the sampling frequency of the Shack-Hartmann wavefront sensor; a laser generating component injects a parallel light beam into the deformable mirror; an action driver operates based on the pulse signal of the first frequency to drive the deformable mirror; a Shack-Hartmann wavefront sensor operates based on the pulse signal of the second frequency to collect and image the reflected light beam of the deformable mirror to obtain a light spot array image; a processor processes the light spot array image to obtain a reconstructed wavefront image, and the working frequency of the deformable mirror is continuously adjusted to complete the frequency response test of the deformable mirror. The present application can greatly reduce the cost of testing the frequency response of a high-frequency deformable mirror.

Description

Technical Field

[0001] The present application relates to the field of adaptive optics technology, and in particular to a frequency response testing device and method for a high-frequency deformable mirror. Background Art

[0002] Adaptive optics is the most promising technology for compensating wavefront distortion in the imaging process caused by atmospheric turbulence or other factors. It was originally developed to overcome the interference of atmospheric turbulence on astronomical observations. After years of development, it has broad applications in astronomy, laser systems, biomedicine and other fields. For example, it is widely used in the field of laser systems and can be applied to laser weapons and laser communications. With the advancement of research on adaptive optics technology in the civilian field, it has gradually been used in various laser systems. These applications can be divided into three categories in essence: beam purification, beam shaping and beam control. In addition, there are some new directions and derived subdivisions or cross-directions, such as laser processing, particle manipulation, optical imaging and coherent synthesis.

[0003] In adaptive optical systems, deformable mirrors are mainly used to compensate for the disturbance of atmospheric turbulence on optical wavefronts. They are adjustable optical elements that can change their shape in real time to offset aberrations on the image plane, ensure that light energy is focused at a predetermined precise position, and improve the stability and imaging quality of adaptive optical systems. In simple terms, a deformable mirror is like a dynamic optical lens that can automatically adjust with changes in ambient light conditions to keep the adaptive optical system at its best performance. In order to adapt to the rapid changes in atmospheric turbulence and improve the accuracy of correction of distorted wavefronts, the working bandwidth of the deformable mirror is further increased, resulting in an increase in the working frequency of the deformable mirror. At this time, the working stroke of the deformable mirror will produce a certain attenuation, and it is necessary to adjust the input voltage of the deformable mirror at high working frequency (usually the camera acquisition frequency is in the order of hundreds of frames, so it is considered that kHz or above is considered high frequency, that is, high working frequency is working frequency above kHz) to cope with the corresponding attenuation. Based on this, the field needs a frequency response test technology for deformable mirrors under stable high working frequency conditions to clarify the above attenuation.

[0004] At present, the cost of frequency response testing technology for high-frequency deformable mirrors (i.e., deformable mirrors operating at high operating frequencies) is relatively high, and there is an urgent need for a frequency response testing technology for high-frequency deformable mirrors that can reduce costs. Summary of the invention

[0005] The purpose of the present application is to provide a frequency response testing device and method for a high-frequency working deformable mirror, which can reduce the testing cost.

[0006] To achieve the above objectives, this application provides the following solutions.

[0007] In a first aspect, the present application provides a frequency response test device for a high-frequency working deformable mirror, the frequency response test device for a high-frequency working deformable mirror comprising: a pulse signal generator, a laser generating component, a Shack-Hartmann wavefront sensor and a processor;

[0008] A pulse signal generator is respectively connected to the motion driver of the deformable mirror and the Shack-Hartmann wavefront sensor for communication, and is used to generate a pulse signal of a first frequency and a pulse signal of a second frequency, and transmit the pulse signal of the first frequency to the motion driver to control the operation of the motion driver, and transmit the pulse signal of the second frequency to the Shack-Hartmann wavefront sensor to control the operation of the Shack-Hartmann wavefront sensor; wherein the first frequency is equal to the operating frequency of the deformable mirror, and the second frequency is equal to the sampling frequency of the Shack-Hartmann wavefront sensor; the sampling frequency of the Shack-Hartmann wavefront sensor is determined based on the operating frequency of the deformable mirror and the maximum operating frame rate of the Shack-Hartmann wavefront sensor, and the operating frequency of the deformable mirror is greater than the maximum operating frame rate of the Shack-Hartmann wavefront sensor;

[0009] A laser generating component, used for generating a parallel light beam and incidenting the parallel light beam onto the deformable mirror;

[0010] An action driver, for driving the deformable mirror based on a pulse signal of a first frequency after the parallel light beam is incident on the deformable mirror;

[0011] A Shack-Hartmann wavefront sensor is used to work based on a pulse signal of a second frequency, collect and image the reflected light beam of the deformable mirror, and obtain a spot array image of the reflected light beam wavefront;

[0012] The processor is respectively connected to the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor for communication. When receiving the light spot array image, the processor processes the light spot array image to obtain a reconstructed wavefront image of the reflected light beam wavefront and determines whether all values ​​of the working frequency of the deformable mirror have been traversed. If not, the working frequency of the deformable mirror is replaced, and the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor are resent to the pulse signal generator. If yes, the frequency response test of the deformable mirror is completed.

[0013] Optionally, the calculation formula of the sampling frequency of the Shack-Hartmann wavefront sensor is:

[0014] ;

[0015] in, is the sampling frequency of the Shack-Hartmann wavefront sensor; is the number of collection points of the deformable mirror in one working cycle; is the operating frequency of the deformable mirror; is the maximum operating frame rate of the Shack-Hartmann wavefront sensor.

[0016] Optionally, the laser generating component includes: a laser light source and a collimator;

[0017] The laser light source is used to generate a laser beam;

[0018] The collimator is used to convert the laser beam into a parallel beam and then direct the parallel beam to the deformable mirror.

[0019] Optionally, the frequency response testing device of the high-frequency working deformable mirror further comprises: a beam reduction mirror group; the beam reduction mirror group is located between the deformable mirror and the Shack-Hartmann wavefront sensor; the beam reduction mirror group is used to make the reflected light beam of the deformable mirror vertically incident on the Shack-Hartmann wavefront sensor.

[0020] In a second aspect, the present application provides a frequency response test method for a high-frequency working deformable mirror, which is applied to a frequency response test device for a high-frequency working deformable mirror as described above. The frequency response test method for a high-frequency working deformable mirror comprises:

[0021] Acquire a preset operating frequency set; the preset operating frequency set includes multiple preset operating frequencies;

[0022] Randomly selecting a preset operating frequency from the preset operating frequency set as the operating frequency of the deformable mirror;

[0023] The sampling frequency of the Shack-Hartmann wavefront sensor is calculated based on the working frequency of the deformable mirror, and a control instruction is issued; the control instruction is used to control the operation of the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor to obtain a spot array image;

[0024] Acquire a light spot array image collected by a Shack-Hartmann wavefront sensor;

[0025] Processing the spot array image to obtain a reconstructed wavefront image;

[0026] Determine whether all preset operating frequencies in the preset operating frequency set have been selected; if not, select an unselected preset operating frequency in the preset operating frequency set as the operating frequency of the deformable mirror for the next iteration, and return to the step of "calculating the sampling frequency of the Shack-Hartmann wavefront sensor based on the operating frequency of the deformable mirror, and issuing control instructions".

[0027] Optionally, processing the spot array image to obtain a reconstructed wavefront image specifically includes:

[0028] The spot array image is processed by using a centroid solution algorithm to obtain the x-direction offset centroid and the y-direction offset centroid of each sub-aperture in the Shack-Hartmann wavefront sensor;

[0029] For each sub-aperture, based on the x-direction offset centroid of the sub-aperture, the x-direction wavefront slope of the sub-aperture is calculated, and based on the y-direction offset centroid of the sub-aperture, the y-direction wavefront slope of the sub-aperture is calculated;

[0030] The wavefront slopes in the x direction and the wavefront slopes in the y direction of all sub-apertures are combined into a wavefront slope vector;

[0031] The wavefront slope vector is used as input and the reconstructed wavefront image is obtained using the pattern method.

[0032] Optionally, the center of mass solution algorithm is a center of gravity method; the mode method is a Zernike mode method, a deformable mirror eigenmode method, a Lukosz mode method or a Legendre mode method.

[0033] Optionally, the x-direction wavefront slope of the sub-aperture is calculated based on the x-direction offset centroid of the sub-aperture, specifically including:

[0034] Calculate the difference between the x-direction offset centroid of the subaperture and the x-direction reference centroid of the subaperture obtained by pre-calibration to obtain the x-direction difference, and calculate the ratio of the x-direction difference to the focal length of the microlens in the Shack-Hartmann wavefront sensor to obtain the x-direction wavefront slope of the subaperture;

[0035] Based on the y-direction offset centroid of the sub-aperture, the y-direction wavefront slope of the sub-aperture is calculated, specifically including:

[0036] The difference between the y-direction offset centroid of the subaperture and the y-direction reference centroid of the subaperture obtained in advance is calculated to obtain the y-direction difference, and the ratio of the y-direction difference and the focal length of the microlens in the Shack-Hartmann wavefront sensor is calculated to obtain the y-direction wavefront slope of the subaperture.

[0037] Optionally, when the pattern method is a Zernike pattern method, the wavefront slope vector is used as input, and the pattern method is used to obtain a reconstructed wavefront image, specifically including:

[0038] The Zernike polynomial coefficient vector is determined based on the wavefront slope vector; the Zernike polynomial coefficient vector includes Zernike polynomial coefficients, is the decomposition mode order;

[0039] The product of the Zernike polynomial coefficient vector and the Zernike polynomial is calculated to obtain the reconstructed wavefront image.

[0040] Optionally, after obtaining the reconstructed wavefront image, the frequency response test method of the high-frequency working deformable mirror further includes:

[0041] Based on the reconstructed wavefront image, the wavefront PV (Peak to Valley) value is calculated, and a curve of the wavefront PV value changing with time is plotted.

[0042] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0043] The present application provides a frequency response test device and method for a high-frequency deformable mirror. The device includes: a pulse signal generator, a laser generating component, a Shack-Hartmann wavefront sensor and a processor. The pulse signal generator generates a pulse signal of a first frequency and a pulse signal of a second frequency. The first frequency is equal to the working frequency of the deformable mirror, and the second frequency is equal to the sampling frequency of the Shack-Hartmann wavefront sensor. The sampling frequency of the Shack-Hartmann wavefront sensor is determined based on the working frequency of the deformable mirror and the maximum working frame rate of the Shack-Hartmann wavefront sensor. The laser generating component causes a parallel light beam to be incident on the deformable mirror. The action driver works based on the pulse signal of the first frequency to drive the deformable mirror. The Shack-Hartmann wavefront sensor works based on the pulse signal of the second frequency to collect and image the reflected light beam of the deformable mirror to obtain a spot array image of the reflected light beam wavefront. The processor processes the spot array image to obtain a reconstructed wavefront image of the reflected light beam wavefront. The working frequency of the deformable mirror is continuously adjusted to complete the frequency response test of the deformable mirror. The present application adopts an external triggering method, and only needs to use a pulse signal generator to control the operating frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor to realize the frequency response test of the deformable mirror. When the operating frequency of the deformable mirror exceeds the maximum operating frame rate of the Shack-Hartmann wavefront sensor, the cost of testing the frequency response can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A flow chart of a frequency response testing method for a high-frequency deformable mirror provided in Example 2 of the present application.

[0046] Figure 2 A schematic flow chart of the implementation principle of a method for testing the continuous wavefront of a high-frequency deformable mirror using a low frame rate Shack-Hartmann wavefront sensor provided in Example 2 of the present invention.

[0047] Figure 3A schematic diagram of the sub-aperture correspondence relationship of the Shack-Hartmann wavefront sensor designed for Embodiment 2 of the present invention.

[0048] Figure 4 This is the reconstructed wavefront image of the deformable mirror provided in Example 2 of the present invention at an operating frequency of 10 kHz.

[0049] Figure 5 This is a schematic diagram of a curve showing how the wavefront PV value of the deformable mirror provided in Example 2 of the present invention changes over time at an operating frequency of 10 kHz. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] Example 1.

[0052] This embodiment provides a frequency response test device for a high-frequency working deformable mirror, which includes: a pulse signal generator, a laser generating component, a Shack-Hartmann wavefront sensor and a processor.

[0053] The pulse signal generator is respectively connected to the action driver of the deformable mirror and the Shack-Hartmann wavefront sensor for communication, and is used to generate a pulse signal of a first frequency and a pulse signal of a second frequency, and transmit the pulse signal of the first frequency to the action driver to control the action driver to work, and transmit the pulse signal of the second frequency to the Shack-Hartmann wavefront sensor to control the Shack-Hartmann wavefront sensor to work. The first frequency is equal to the working frequency of the deformable mirror, the second frequency is equal to the sampling frequency of the Shack-Hartmann wavefront sensor, and the sampling frequency of the Shack-Hartmann wavefront sensor is determined based on the working frequency of the deformable mirror and the maximum working frame rate of the Shack-Hartmann wavefront sensor. The working frequency of the deformable mirror is greater than the maximum working frame rate of the Shack-Hartmann wavefront sensor. The maximum working frame rate can be understood as the maximum number of frames displayed per second, and the sampling frequency can be understood as the number of data points collected per second.

[0054] The laser generating component is used to generate a parallel light beam and direct the parallel light beam to the deformable mirror.

[0055] The action driver is used to drive the deformable mirror based on a pulse signal of a first frequency after the parallel light beam is incident on the deformable mirror.

[0056] The Shack-Hartmann wavefront sensor is used to work based on a pulse signal of a second frequency, collect and image the reflected light beam of the deformable mirror, and obtain a spot array image of the reflected light beam wavefront.

[0057] The processor is respectively connected to the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor for communication. When receiving the light spot array image, the processor processes the light spot array image to obtain a reconstructed wavefront image of the reflected light beam wavefront and determines whether all values ​​of the working frequency of the deformable mirror have been traversed. If not, the working frequency of the deformable mirror is replaced, and the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor are resent to the pulse signal generator. If yes, the frequency response test of the deformable mirror is completed.

[0058] The present embodiment provides a testing device for testing the frequency response of a high-frequency deformable mirror using a low frame rate Shack-Hartmann wavefront sensor. The maximum operating frame rate of the Shack-Hartmann wavefront sensor is less than the operating frequency of the deformable mirror. The prior art method for dealing with this situation is to use a high operating frame rate Shack-Hartmann wavefront sensor. In this case, the maximum operating frame rate of the Shack-Hartmann wavefront sensor is greater than the operating frequency of the deformable mirror. However, this method will bring about the problem of higher costs. Based on this, the present embodiment discloses a frequency response test device for a deformable mirror with a high operating frequency, taking the wavefront response of the high-frequency deformable mirror as the test target, and calculating and setting the sampling frequency of the Shack-Hartmann wavefront sensor according to the operating frequency of the deformable mirror and the maximum operating frame rate of the Shack-Hartmann wavefront sensor to collect and reconstruct the wavefront signal of the high-frequency deformable mirror, thereby obtaining a reconstructed wavefront image, and subsequently determining the attenuation of the deformable mirror when it is working at a high frequency. The present embodiment is based on the reconstruction of the tilt aberration mode, and when the operating frequency of the deformable mirror exceeds the maximum operating frame rate of the Shack-Hartmann wavefront sensor, the sampling frequency of the Shack-Hartmann wavefront sensor is controlled by setting an external trigger to test the frequency response of the deformable mirror at a high operating frequency. The present embodiment is suitable for frequency response testing when the operating frequency of the deformable mirror exceeds the maximum operating frame rate of the Shack-Hartmann wavefront sensor, thereby reducing the cost of testing the frequency response of the high-frequency deformable mirror, thereby realizing the frequency response test of the deformable mirror in the adaptive optical system at a low cost.

[0059] In this embodiment, according to the working frequency of the deformable mirror and the maximum operating frame rate of the Shack-Hartmann wavefront sensor , calculate the sampling frequency of the Shack-Hartmann wavefront sensor , the sampling frequency of the Shack-Hartmann wavefront sensor The calculation formula is:

[0060] (1)

[0061] In formula (1), is the sampling frequency of the Shack-Hartmann wavefront sensor; is the number of collection points of the deformable mirror in one working cycle; is the operating frequency of the deformable mirror; is the maximum operating frame rate of the Shack-Hartmann wavefront sensor.

[0062] The pulse signal generator is connected to the processor for communication, and the processor is used to send the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor to the pulse signal generator. and the calculated sampling frequency of the Shack-Hartmann wavefront sensor The frequencies of channel 1 and channel 2 of the pulse signal generator are set to and , so that channel 1 generates the first frequency ( ) pulse signal, channel 2 generates the second frequency ( ) and controls the operation of the action driver of the deformable mirror based on the pulse signal of the first frequency, and controls the operation of the Shack-Hartmann wavefront sensor based on the pulse signal of the second frequency.

[0063] In this embodiment, the laser generating component is connected to the processor for communication, and the processor is used to control the laser generating component to turn on or off. Specifically, the laser generating component includes: a laser light source and a collimator, the laser light source is used to generate a laser beam, the collimator is used to convert the laser beam into a parallel beam, and the parallel beam is incident on the deformable mirror. At this time, the laser light source is connected to the processor for communication, and the processor is used to control the laser light source to turn on or off.

[0064] The motion driver is connected to the processor for controlling the motion driver. When the parallel light beam is incident on the deformable mirror, the motion driver works based on the pulse signal of the first frequency to drive the deformable mirror, and the deformable mirror is used to modify the surface shape of the wavefront of the parallel light beam to correct the wavefront error. In this process, the reflected light beam of the deformable mirror is vertically incident on the Shack-Hartmann wavefront sensor.

[0065] The frequency response testing device of the high-frequency working deformable mirror of this embodiment also includes: a beam reduction mirror group, which is located between the deformable mirror and the Shack-Hartmann wavefront sensor, and is used to make the reflected light beam of the deformable mirror vertically incident on the Shack-Hartmann wavefront sensor.

[0066] When the Shack-Hartmann wavefront sensor receives the reflected light beam, the Shack-Hartmann wavefront sensor operates based on the pulse signal of the second frequency, collects and images the reflected light beam, and obtains a spot array image of the reflected light beam wavefront.

[0067] The processor is in communication connection with the Shack-Hartmann wavefront sensor. When receiving the light spot array image, the processor processes the light spot array image to obtain a reconstructed wavefront image of the reflected light beam wavefront.

[0068] Through the above process, a test under the working frequency of a deformable mirror can be completed. In order to complete the frequency response test, the working frequency of the deformable mirror needs to be changed multiple times. At this time, the processor stores multiple values ​​of the working frequency of the deformable mirror. After completing a test, the processor determines whether all values ​​of the working frequency of the deformable mirror have been traversed. If not, the working frequency of the deformable mirror is replaced, and the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor are re-sent to the pulse signal generator for the next test. If so, the frequency response test of the deformable mirror is completed.

[0069] This embodiment can obtain multiple reconstructed wavefront images in one test at the working frequency of a deformable mirror. For each reconstructed wavefront image, the wavefront PV value is calculated based on the reconstructed wavefront image, all wavefront PV values ​​are arranged according to the acquisition time of the reconstructed wavefront image, and a curve of the change of the wavefront PV value over time is further plotted.

[0070] The frequency response test device of the high-frequency working deformable mirror used in this embodiment includes: a pulse signal generator, a laser light source, a collimator, a beam reduction mirror and a Shack-Hartmann wavefront sensor. The action driver of the deformable mirror and the Shack-Hartmann wavefront sensor are both externally triggered, specifically controlled by the pulse signal generator. The laser beam emitted by the laser light source is converted into a parallel beam after passing through the collimator. The parallel beam is used as a measuring beam and incident on the deformable mirror. The action driver drives the deformable mirror to move based on a pulse signal of a first frequency to correct the wavefront error. The reflected beam of the deformable mirror is vertically incident on the Shack-Hartmann wavefront sensor through the beam reduction mirror. The front sensor and the Shack-Hartmann wavefront sensor collect and image the reflected light beam, continuously adjust the working frequency of the deformable mirror, and complete the frequency response test of the deformable mirror. Compared with the prior art, the test device of this embodiment does not change the hardware and data processing flow of the deformable mirror test. It only needs to use a pulse signal generator to control the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor to achieve the frequency response test of the deformable mirror. When the working frequency of the deformable mirror exceeds the maximum working frame rate of the Shack-Hartmann wavefront sensor, the test device proposed in this embodiment can reduce the cost of the frequency response test. At the same time, considering that the Shack-Hartmann wavefront sensor is a high-precision phase measurement device, its measurement accuracy of the wavefront error can usually reach the sub-micron level. Therefore, the test device of this embodiment can theoretically realize extremely accurate judgment of the working stroke of the deformable mirror with an operating frequency of up to 100kHz, which has important practical value for giving full play to the optimal correction performance of the adaptive optical system. Compared with the traditional frequency response test device, the test device of this embodiment has the technical advantage of achieving both high precision and high stability under the same measurement range, and has the ability to resist errors caused by environmental disturbances.

[0071] Example 2.

[0072] This embodiment provides a frequency response test method for a high-frequency working deformable mirror, which is applied to the frequency response test device for a high-frequency working deformable mirror described in Embodiment 1. Figure 1 As shown, the frequency response test method of the high-frequency working deformable mirror includes the following steps.

[0073] S1: Acquire a preset operating frequency set; the preset operating frequency set includes a plurality of preset operating frequencies.

[0074] S2: Randomly select a preset operating frequency from the preset operating frequency set as the operating frequency of the deformable mirror.

[0075] S3: Calculate the sampling frequency of the Shack-Hartmann wavefront sensor based on the operating frequency of the deformable mirror and issue a control instruction; the control instruction is used to control the operation of the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor to obtain a spot array image.

[0076] After the control command is issued, the pulse signal generator works to generate a pulse signal of a first frequency and a pulse signal of a second frequency, and transmits the pulse signal of the first frequency to the action driver, and transmits the pulse signal of the second frequency to the Shack-Hartmann wavefront sensor. The laser generating component works to make the parallel light beam incident on the deformable mirror, and the action driver works based on the pulse signal of the first frequency to drive the deformable mirror. The reflected light beam of the deformable mirror is vertically incident on the Shack-Hartmann wavefront sensor, and the Shack-Hartmann wavefront sensor works based on the pulse signal of the second frequency to collect and image the reflected light beam to obtain a spot array image of the reflected light beam wavefront.

[0077] S4: Acquire the spot array image collected by the Shack-Hartmann wavefront sensor.

[0078] S5: Process the spot array image to obtain a reconstructed wavefront image.

[0079] S6: Determine whether all preset operating frequencies in the preset operating frequency set have been selected; if not, select an unselected preset operating frequency in the preset operating frequency set as the operating frequency of the deformable mirror for the next iteration, and return to the step of "calculating the sampling frequency of the Shack-Hartmann wavefront sensor based on the operating frequency of the deformable mirror, and issuing control instructions".

[0080] In S5, the spot array image is processed to obtain a reconstructed wavefront image, which specifically includes the following steps.

[0081] (1) The spot array image is processed using the centroid solution algorithm to obtain the x-direction offset centroid and y-direction offset centroid of each sub-aperture in the Shack-Hartmann wavefront sensor.

[0082] Among them, the centroid solution algorithm can be a centroid method. At this time, for each sub-aperture, the product of the position (x coordinate or y coordinate) and the pixel value (generally intensity) of each pixel point in the sub-aperture is first calculated, and the sum of the products corresponding to all pixel points is calculated to obtain a first sum, and then the sum of the pixel values ​​of each pixel point in the sub-aperture is calculated to obtain a second sum, and finally the ratio of the first sum and the second sum is calculated to obtain the x-direction offset centroid or the y-direction offset centroid of the sub-aperture. Specifically, when the position is an x-coordinate, the x-direction offset centroid is calculated, and when the position is a y-coordinate, the y-direction offset centroid is calculated.

[0083] (2) For each subaperture, the wavefront slope in the x direction of the subaperture is calculated based on the offset centroid of the subaperture in the x direction, and the wavefront slope in the y direction of the subaperture is calculated based on the offset centroid of the subaperture in the y direction.

[0084] Wherein, based on the x-direction offset centroid of the subaperture, the x-direction wavefront slope of the subaperture is calculated, specifically including: calculating the difference between the x-direction offset centroid of the subaperture and the x-direction reference centroid of the subaperture obtained by pre-calibration to obtain the x-direction difference, and calculating the ratio of the x-direction difference to the focal length of the microlens in the Shack-Hartmann wavefront sensor to obtain the x-direction wavefront slope of the subaperture.

[0085] Wherein, based on the y-direction offset centroid of the subaperture, the y-direction wavefront slope of the subaperture is calculated, specifically including: calculating the difference between the y-direction offset centroid of the subaperture and the y-direction reference centroid of the subaperture obtained by pre-calibration to obtain the y-direction difference, and calculating the ratio of the y-direction difference and the focal length of the microlens in the Shack-Hartmann wavefront sensor to obtain the y-direction wavefront slope of the subaperture.

[0086] (3) The wavefront slopes in the x-direction and the wavefront slopes in the y-direction of all sub-apertures are combined to form a wavefront slope vector.

[0087] After the Shack-Hartmann wavefront sensor completes the wavefront shape measurement, the center of the subaperture can be aligned with the center of the microlens array spot by using the centroid solution algorithm to obtain the wavefront slope vector. The wavefront slope vector is in the following form:

[0088] (2)

[0089] In formula (2), is the wavefront slope vector; and They represent the Shack-Hartmann wavefront sensor The wavefront slope in the x direction and the wavefront slope in the y direction of each sub-aperture, , is the number of effectively working subapertures, The dimension is .

[0090] (4) Taking the wavefront slope vector as input, the pattern method is used to obtain the reconstructed wavefront image.

[0091] After the wavefront slope vector of the initial input parallel light beam wavefront is calculated by the x-direction centroid offset (i.e., the x-direction difference) and the y-direction centroid offset (i.e., the y-direction difference), the pattern method can be used to complete the wavefront restoration (or wavefront reconstruction) to obtain the reconstructed wavefront image. The pattern method can be a Zernike pattern method, a deformable mirror eigenmode method, a Lukosz pattern method, or a Legendre pattern method. Of course, other algorithms with the same or similar functions can also be used, as long as they can complete the wavefront restoration, and this embodiment does not impose any restrictions on this.

[0092] When the pattern method is the Zernike pattern method, the wavefront is first solved according to the spot array image acquired by the Shack-Hartmann wavefront sensor, and then the surface is Zernike decomposed, and finally the wavefront information is restored. At this time, the wavefront slope vector is used as input and the pattern method is used to obtain the reconstructed wavefront image, which specifically includes the following steps.

[0093] (1) Determine the Zernike polynomial coefficient vector based on the wavefront slope vector. The Zernike polynomial coefficient vector includes The coefficients of the Zernike polynomials are is the decomposition mode order.

[0094] Among them, according to the wavefront slope vector, the relationship between the Zernike polynomial and the wavefront slope detected by the Shack-Hartmann wavefront sensor is established, and the Zernike coefficient vector is solved, that is, the Zernike polynomial coefficient vector is obtained, as follows:

[0095] (3)

[0096] In formula (3), is the Zernike polynomial coefficient vector, including the coefficients of each mode vector (i.e., Zernike polynomial) to be determined, with a dimension of , is the decomposition mode order; is the wavefront reconstruction matrix, with dimension , including pre-designed Zernike polynomials.

[0097] (4)

[0098] In formula (4), For the Line The Zernike polynomials in the x-direction of the column; For the Line Zernike polynomials in the y direction of the column.

[0099] (2) Based on the Zernike polynomial coefficient vector obtained by Zernike decomposition, the wavefront is further reconstructed. Specifically, the Zernike polynomial coefficient vector and the Zernike polynomial (i.e. ) to obtain the reconstructed wavefront image.

[0100] After obtaining the reconstructed wavefront image, this embodiment can further calculate the wavefront PV value, which is the difference between the maximum deformation and the minimum deformation in the reconstructed wavefront image, and draw a curve of the change of the wavefront PV value of the deformable mirror over time at a specific operating frequency.

[0101] At this time, after obtaining the reconstructed wavefront image, the frequency response test method of the high-frequency working deformable mirror of this embodiment also includes: calculating the wavefront PV value based on the reconstructed wavefront image, and drawing a curve of the change of the wavefront PV value over time.

[0102] Hereinafter, this embodiment introduces the testing method of this embodiment through a specific example.

[0103] like Figure 2 As shown, it is a flow chart of the implementation principle of a frequency response test method for testing the continuous wavefront of a high-frequency working deformable mirror using a low frame rate Shack-Hartmann wavefront sensor, wherein the clear aperture of the collimator is 80 mm, the clear aperture of the deformable mirror is 15 mm, the spacing of the motion drivers is 7 mm, the number of effective motion drivers is 7, the clear aperture of the Shack-Hartmann wavefront sensor is 5 mm, the size of the subaperture is 0.15 mm, the number of effective subapertures is 414, and the wavelength of the laser beam to be tested is 1064 nm.

[0104] like Figure 3 As shown in the figure, it is the sub-aperture correspondence of the Shack-Hartmann wavefront sensor. The square grid represents the sub-aperture segmentation frame, and the circular dots represent the microlens array light spot. It can be seen that the microlens array light spot is exactly located in the center of the sub-aperture segmentation frame. However, in the actual adaptive optical system, the sub-aperture segmentation frame is not directly visible to the naked eye, and it cannot be guaranteed that the microlens array light spot falls exactly in the center of the sub-aperture segmentation frame. A specific method is needed to adjust the system, that is, the center of mass solution algorithm.

[0105] The operating frequency of the deformable mirror is 1kHz, the number of acquisition points in a single cycle is 100, and the maximum operating frame rate of the Shack-Hartmann wavefront sensor is 25Hz. The sampling frequency of the Shack-Hartmann wavefront sensor is calculated to be 24.993751Hz, accurate to 6 decimal places. According to the operating frequency of the deformable mirror and the calculated sampling frequency of the Shack-Hartmann wavefront sensor, the frequencies of channel 1 and channel 2 of the pulse signal generator are set to 1kHz and 24.993751Hz, respectively, and the motion driver of the deformable mirror and the Shack-Hartmann wavefront sensor are controlled respectively. After the Shack-Hartmann wavefront sensor completes the wavefront shape measurement, the center of mass solution algorithm is used to calculate the spot array image of the wavefront, so that the sub-aperture center can be aligned with the microlens array spot center to obtain the wavefront slope vector. The dimension of the wavefront slope vector is , is the number of effective subapertures, which is 414. According to the wavefront slope vector, the relationship between the Zernike polynomial and the wavefront slope detected by the Shack-Hartmann wavefront sensor is established, and the Zernike polynomial coefficient vector is solved. The dimension of the Zernike polynomial coefficient vector is , is the decomposition mode order, which is set to 45. Based on the Zernike polynomial coefficient vector obtained by Zernike decomposition, the waveform is further restored, and the reconstructed wavefront image is obtained as follows: Figure 4 As shown, the wavefront PV value is calculated based on the reconstructed wavefront image, and the variation curve of the PV value of the deformable mirror at a specific trigger frequency over time is drawn, as shown in Figure 5 shown.

[0106] like Figure 4 As shown in FIG. 1 , it is a reconstructed wavefront image obtained by the deformable mirror at a certain working frequency (i.e., 10 kHz). The spot array image collected by the Shack-Hartmann wavefront sensor is decomposed by the centroid solution algorithm and the Zernike mode method to obtain the first 45-order Zernike coefficients, and the reconstructed wavefront image is obtained after further wavefront restoration.

[0107] like Figure 5 As shown in the figure, it is a curve of the wavefront PV value of the deformable mirror changing with time at a certain working frequency (i.e. 10kHz). Within one cycle of the motion driver of the deformable mirror, the Shack-Hartmann wavefront sensor is used to sample the spot array image at 100 time points. After reconstructing the reconstructed wavefront image at each time point, the wavefront PV value at each time point is further calculated, and the change curve is obtained by plotting.

[0108] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiment method can be implemented by instructing related hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, the process of the above-mentioned embodiment method can be implemented.

[0109] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A frequency response test device for a high-frequency deformable mirror, characterized in that: The frequency response test device of the high-frequency working deformable mirror comprises: a pulse signal generator, a laser generating component, a Shack-Hartmann wavefront sensor and a processor; A pulse signal generator is respectively connected to the motion driver of the deformable mirror and the Shack-Hartmann wavefront sensor for communication, and is used to generate a pulse signal of a first frequency and a pulse signal of a second frequency, and transmit the pulse signal of the first frequency to the motion driver to control the operation of the motion driver, and transmit the pulse signal of the second frequency to the Shack-Hartmann wavefront sensor to control the operation of the Shack-Hartmann wavefront sensor; wherein the first frequency is equal to the operating frequency of the deformable mirror, and the second frequency is equal to the sampling frequency of the Shack-Hartmann wavefront sensor; the sampling frequency of the Shack-Hartmann wavefront sensor is determined based on the operating frequency of the deformable mirror and the maximum operating frame rate of the Shack-Hartmann wavefront sensor, and the operating frequency of the deformable mirror is greater than the maximum operating frame rate of the Shack-Hartmann wavefront sensor; A laser generating component, used for generating a parallel light beam and incidenting the parallel light beam onto the deformable mirror; An action driver, for driving the deformable mirror based on a pulse signal of a first frequency after the parallel light beam is incident on the deformable mirror; A Shack-Hartmann wavefront sensor is used to work based on a pulse signal of a second frequency, collect and image the reflected light beam of the deformable mirror, and obtain a spot array image of the reflected light beam wavefront; The processor is respectively connected to the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor for communication, and is used for processing the light spot array image when receiving the light spot array image, obtaining a reconstructed wavefront image of the reflected light beam wavefront, and judging whether all values ​​of the working frequency of the deformable mirror have been traversed, if not, changing the working frequency of the deformable mirror, resending the working frequency of the deformable mirror and the sampling frequency of the Shack-Hartmann wavefront sensor to the pulse signal generator, and if yes, completing the frequency response test of the deformable mirror; The calculation formula for the sampling frequency of the Shack-Hartmann wavefront sensor is: ； in, is the sampling frequency of the Shack-Hartmann wavefront sensor; is the number of collection points of the deformable mirror in one working cycle; is the operating frequency of the deformable mirror; is the maximum operating frame rate of the Shack-Hartmann wavefront sensor.

2. The frequency response test device of the high-frequency working deformable mirror according to claim 1, characterized in that: The laser generating components include: a laser light source and a collimator; The laser light source is used to generate a laser beam; The collimator is used to convert the laser beam into a parallel beam and then direct the parallel beam to the deformable mirror.

3. The frequency response test device of the high-frequency working deformable mirror according to claim 1, characterized in that: The frequency response test device of the high-frequency working deformable mirror also includes: a beam reduction mirror; the beam reduction mirror is located between the deformable mirror and the Shack-Hartmann wavefront sensor; the beam reduction mirror is used to make the reflected light beam of the deformable mirror vertically incident on the Shack-Hartmann wavefront sensor.

4. A method for testing the frequency response of a high-frequency deformable mirror, applied to the device for testing the frequency response of a high-frequency deformable mirror according to any one of claims 1 to 3, characterized in that: The frequency response test method of the high-frequency working deformable mirror comprises: Acquire a preset operating frequency set; the preset operating frequency set includes multiple preset operating frequencies; Randomly selecting a preset operating frequency from the preset operating frequency set as the operating frequency of the deformable mirror; The sampling frequency of the Shack-Hartmann wavefront sensor is calculated based on the working frequency of the deformable mirror, and a control instruction is issued; the control instruction is used to control the operation of the pulse signal generator, the laser generating component, the motion driver and the Shack-Hartmann wavefront sensor to obtain a spot array image; Acquire a light spot array image collected by a Shack-Hartmann wavefront sensor; Processing the spot array image to obtain a reconstructed wavefront image; Determine whether all preset operating frequencies in the preset operating frequency set have been selected; if not, select an unselected preset operating frequency in the preset operating frequency set as the operating frequency of the deformable mirror for the next iteration, and return to the step of "calculating the sampling frequency of the Shack-Hartmann wavefront sensor based on the operating frequency of the deformable mirror, and issuing a control instruction".

5. The frequency response test method of a high-frequency working deformable mirror according to claim 4, characterized in that: The spot array image is processed to obtain a reconstructed wavefront image, specifically including: The spot array image is processed by using a centroid solution algorithm to obtain the x-direction offset centroid and the y-direction offset centroid of each sub-aperture in the Shack-Hartmann wavefront sensor; For each sub-aperture, based on the x-direction offset centroid of the sub-aperture, the x-direction wavefront slope of the sub-aperture is calculated, and based on the y-direction offset centroid of the sub-aperture, the y-direction wavefront slope of the sub-aperture is calculated; The wavefront slopes in the x direction and the wavefront slopes in the y direction of all sub-apertures are combined into a wavefront slope vector; The wavefront slope vector is used as input and the reconstructed wavefront image is obtained using the pattern method.

6. The frequency response test method of a high-frequency working deformable mirror according to claim 5, characterized in that: The center of mass solution algorithm is the center of gravity method; the mode method is the Zernike mode method, the deformable mirror eigenmode method, the Lukosz mode method or the Legendre mode method.

7. The frequency response test method of a high-frequency working deformable mirror according to claim 5, characterized in that: Based on the x-direction offset centroid of the sub-aperture, the x-direction wavefront slope of the sub-aperture is calculated, specifically including: Calculate the difference between the x-direction offset centroid of the subaperture and the x-direction reference centroid of the subaperture obtained by pre-calibration to obtain the x-direction difference, and calculate the ratio of the x-direction difference to the focal length of the microlens in the Shack-Hartmann wavefront sensor to obtain the x-direction wavefront slope of the subaperture; Based on the y-direction offset centroid of the sub-aperture, the y-direction wavefront slope of the sub-aperture is calculated, specifically including: The difference between the y-direction offset centroid of the subaperture and the y-direction reference centroid of the subaperture obtained in advance is calculated to obtain the y-direction difference, and the ratio of the y-direction difference and the focal length of the microlens in the Shack-Hartmann wavefront sensor is calculated to obtain the y-direction wavefront slope of the subaperture.

8. The frequency response test method of a high-frequency working deformable mirror according to claim 6, characterized in that: When the pattern method is the Zernike pattern method, the wavefront slope vector is used as input and the reconstructed wavefront image is obtained by using the pattern method, specifically including: The Zernike polynomial coefficient vector is determined based on the wavefront slope vector; the Zernike polynomial coefficient vector includes Zernike polynomial coefficients, is the decomposition mode order; The product of the Zernike polynomial coefficient vector and the Zernike polynomial is calculated to obtain the reconstructed wavefront image.

9. The frequency response test method of a high-frequency working deformable mirror according to claim 4, characterized in that: After obtaining the reconstructed wavefront image, the frequency response test method of the high-frequency working deformable mirror further includes: Based on the reconstructed wavefront image, the wavefront PV value is calculated, and a curve showing the change of the wavefront PV value over time is plotted.

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