Deformable mirror slope response matrix measurement method and device based on voltage modulation

Abstract

The invention discloses a deformable mirror slope response matrix measurement method and device based on voltage modulation, and belongs to the technical field of adaptive optics, and the method comprises the steps: calculating the influence range of a single driver, and grouping the drivers; generating a voltage control signal for controlling the deformable mirror according to the sampling frequency of the Hartmann wavefront sensor and the frequency response characteristic of the deformable mirror; according to the driver grouping number, applying a voltage control signal to all drivers and recording a wavefront sensor slope signal of each group of drivers; bidirectional filtering is carried out on the slope signal of the wavefront sensor, the slope signal corresponding to each driver is restored, the phase difference between each slope signal and the corresponding voltage control signal is calculated, the voltage control signals are cut off, and a deformable mirror response matrix is obtained. The measuring time of the slope response matrix of the deformable mirror is effectively shortened, and the problem that the calculation precision of the response matrix is reduced due to phase irregularity of the voltage control signal and the slope signal is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of adaptive optics, and in particular relates to a method and device for measuring the slope response matrix of a deformable mirror based on voltage modulation. Background Art

[0002] Adaptive optics (AO) technology is an effective means of compensating for atmospheric turbulence in real time. Its basic principle is to use a deformable mirror to compensate for detected wavefront distortion. In an AO system, two crucial components exist: the Hartmann wavefront sensor (SHWFS) and the deformable mirror (DM), which determine the system's ability to spatially detect and correct aberrations, respectively. To fully utilize the aberration correction capabilities of an AO system, it is necessary to accurately measure the matching relationship between the deformable mirror actuator and the wavefront detector subaperture, i.e., the AO system's response matrix.

[0003] When adaptive optics systems employ deformable secondary and primary mirrors, the precise measurement of the response matrix is subject to multiple dynamic aberrations: system noise (such as low-frequency jitter in the optical path caused by turbulent noise, statistical fluctuations caused by photon noise, and detector readout noise), device characteristic limitations (nonlinear hysteresis of the deformable mirror and subaperture calibration deviations of the wavefront sensor), and long-term temperature drift (geometric mapping drift caused by thermal deformation of the optical path). These three factors interact with each other. Turbulence noise dominates under natural light sources, causing dynamic wavefront distortion that significantly degrades the accuracy of wavefront sensor centroid detection, leading to significant error accumulation in the response matrix measurement. This ultimately degrades the adaptive optics correction performance and even prevents stable closed-loop operation. Consequently, due to the structure of the adaptive optics system, the deformable mirror response matrix measurement process often fails to use an unperturbed light source. This results in a significant amount of noise in the wavefront sensor slope data, resulting in a low signal-to-noise ratio and impacting the measurement accuracy of the adaptive optics response matrix. Ultimately, this degrades the adaptive optics correction performance and even prevents stable closed-loop operation.

[0004] Existing technologies use long exposure methods, voltage modulation methods, direct calculation methods, etc. to achieve the measurement of the deformable mirror response matrix under dynamic aberration disturbance. The long exposure method uses the wavefront sensor to expose the wavefront slope signal for a long time and then average it. For atmospheric turbulence, which is a noise signal mainly composed of low-frequency energy, the long exposure method needs to suppress its randomness for a long time. As time goes by, the influence of other factors such as temperature drift of the system gradually increases with time. The voltage modulation method takes into account that the disturbance introduced by turbulence is mainly low-frequency. By modulating the deformable mirror voltage control signal to the high-frequency region, the signal-to-noise ratio is improved. However, the voltage modulation method has a long measurement time, and after the voltage control signal is sent, it is necessary to wait for the control signal to stabilize. Therefore, the time difference between the start of recording the wavefront sensor signal and the time of sending the voltage control signal is uncertain, resulting in an uncertain phase difference between the two. During the calculation process using the formula, the uncertainty of the phase difference leads to different calculation results each time, which significantly affects the accuracy of the measurement results. The direct calculation method utilizes a mathematical model of the deformable mirror and wavefront sensor alignment to directly calculate the response matrix. However, a significant drawback is that if the system is subject to external physical disturbances, the alignment between the deformable mirror and wavefront sensor will change, leading to a decrease in the credibility of the mathematical model. Furthermore, the measurement process of the long exposure method and voltage modulation method requires the repeated application of voltage to the actuator to record the wavefront sensor signal. This process presents a practical problem: for a large number of deformable mirror actuators, each actuator can be driven for up to 20 seconds, resulting in a single measurement time of up to hours. Furthermore, due to changes in the system structure during operation, the response matrix needs to be remeasured during the observation process. This long measurement time significantly reduces scientific observation time. Therefore, the existing technology is affected by dynamic aberration disturbances, resulting in high noise in the measurement of the deformable mirror slope response matrix. Under dynamic aberration disturbances, the response matrix measurement accuracy is low and the speed is slow. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for measuring a deformable mirror slope response matrix based on voltage modulation, comprising:

[0007] Step 1: Calculate the influence range of a single actuator based on the deformable mirror parameters. The actuators are grouped based on the criterion that no other actuators are within twice the influence range of a single actuator.

[0008] Step 2: Based on the sampling frequency of the Hartmann wavefront sensor, the frequency response characteristics of the deformable mirror, and the power spectrum density of the noise introduced by atmospheric turbulence, a set of sinusoidal voltage signals for controlling the deformable mirror is generated as voltage control signals;

[0009] Step 3: Apply the corresponding voltage control signal in step 2 to the corresponding driver according to the driver group number in step 1, so that all drivers are driven; record the wavefront sensor slope signal after each group of drivers is driven;

[0010] Step 4: Perform bidirectional filtering on the wavefront sensor slope signal in step 3 to restore the slope signal corresponding to each driver, calculate the phase difference between each slope signal and its corresponding voltage control signal, truncate the voltage control signal, and obtain the deformable mirror response matrix.

[0011] A device for measuring a deformable mirror slope response matrix based on voltage modulation, comprising:

[0012] The driver grouping module calculates the influence range of a single driver based on the deformable mirror parameters, and groups the drivers based on the standard that no other driver exists within twice the influence range of a single driver.

[0013] The voltage control signal generation module generates a set of sinusoidal voltage signals used to control the deformable mirror as voltage control signals based on the sampling frequency of the Hartmann wavefront sensor, the frequency response characteristics of the deformable mirror, and the power spectrum density of the noise introduced by atmospheric turbulence.

[0014] The driving module applies the corresponding voltage control signal in step 2 to the corresponding driver according to the driver group number in step 1, so that all drivers are driven; and records the wavefront sensor slope signal after each group of drivers is driven;

[0015] The response matrix acquisition module performs bidirectional filtering on the wavefront sensor slope signal in step 3 to restore the slope signal corresponding to each driver. It calculates the phase difference between each slope signal and its corresponding voltage control signal, truncates the voltage control signal, and obtains the deformable mirror response matrix.

[0016] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the method for measuring the slope response matrix of a deformable mirror based on voltage modulation are implemented.

[0017] A non-transitory computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for measuring the slope response matrix of a deformable mirror based on voltage modulation.

[0018] The present invention has the following beneficial effects:

[0019] (1) The present invention groups the drivers so that the drivers driven at the same time are far apart. Considering the fact that the noise caused by turbulence on the wavefront slope is mainly concentrated in the low-frequency region, the driving voltage frequencies of different drivers in the same group are all in the high-frequency region, and the frequencies are different. This ensures that there is little mutual interference within the group and different frequency components in the slope signal are clearly distinguished, thereby effectively shortening the measurement time of the deformable mirror slope response matrix.

[0020] (2) The present invention uses a digital filter to distribute the slope signal to the corresponding driver according to different control frequencies, thereby realizing the functions of driving multiple drivers at one time and signal separation, and performing phase alignment on the separated slope signals, thereby avoiding the problem of decreased accuracy in response matrix calculation due to the misalignment of the phase between the voltage control signal and the slope signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the flow of the method for measuring the slope response matrix of a deformable mirror based on voltage modulation of the present invention;

[0022] Figure 2a is the ideal response matrix of the deformable mirror without external disturbance;

[0023] Figure 2b The response matrix of the deformable mirror calculated by the modulation method under disturbance;

[0024] Figure 2c The deformable mirror response matrix calculated by the long exposure method under disturbance;

[0025] Figure 3a The residual error of wavefront restoration is the response matrix calculated without external perturbations;

[0026] Figure 3b is the residual error of wavefront restoration using the response matrix calculated by the modulation method under disturbance;

[0027] Figure 3c is the residual error of wavefront restoration using the response matrix calculated using the long exposure method under disturbance. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] The present invention modulates the voltage control signal to the high-frequency region to effectively separate the portion of the wavefront sensor slope signal generated by the high-frequency voltage control signal from the portion generated by the low-frequency turbulence noise, thereby improving the measurement accuracy of the deformable mirror response matrix. The invention is particularly suitable for natural light source scenes dominated by turbulence.

[0030] The present invention's voltage-modulated deformable mirror slope response matrix measurement method, based on the characteristic that the power spectral density of the disturbance introduced by turbulent noise rapidly decays with increasing frequency, groups the drivers to achieve the driving of multiple drivers at once, ensuring the separation of the slope signals generated by different drivers and effectively shortening the response matrix measurement time. Through the phase alignment process, the phase deviation problem between the deformable mirror voltage control signal and the wavefront sensor slope signal caused by system design and filtering issues is resolved, improving the accuracy loss caused by phase misalignment during the response matrix calculation process. Ultimately, the measurement accuracy of the deformable mirror response matrix is improved when dynamic aberration interference exists in the measurement optical path. The method is specifically implemented through the following steps:

[0031] like Figure 1 As shown, the method for measuring the slope response matrix of a deformable mirror based on voltage modulation of the present invention specifically includes:

[0032] Step 1: Calculate the influence range of a single actuator based on the deformable mirror parameters. The actuators are grouped if no other actuator is within twice the influence range of the single actuator (the grouping method can be the minimum spacing method or the graph coloring method. The present invention uses the minimum spacing method as an example for illustration).

[0033] According to the cross-link value and pole spacing of the deformable mirror driver, the minimum spacing method is used, and the distance of 2 times the influence range is used as the standard to divide the driver into groups, each containing Drive, The group drive coordinates are ,in, For the The coordinates of the first drive of the group, For the Set the coordinates of the second drive, For the Group The coordinates of the drive.

[0034] Among them, the minimum spacing method is used to divide the driver into Groups, including:

[0035] Step 1.1, determine the distribution of the deformable mirror actuator. Generally, a square distribution is selected with a size of , the pole spacing of the driver is , the crosslink value of the driver is , the effective influence range of a single driver is calculated as , choose the distance between them as drives into a group.

[0036] Step 1.2, assume , which means that every two drives are selected to enter the current group, and the group number is finally obtained. ;

[0037] Where, is the row coordinate of the driver distribution, is the column coordinate of the driver distribution, It is the driver group number, corresponding to the actual grouping of each driver, such as Represents the group number of the second row and third column drive.

[0038] Step 2: Based on the sampling frequency of the Hartmann wavefront sensor, the frequency response characteristics of the deformable mirror, and the power spectrum density of the noise introduced by atmospheric turbulence, a set of sinusoidal voltage signals for controlling the deformable mirror is generated as voltage control signals.

[0039] The specific process of generating the sinusoidal voltage signal in step 2 is as follows:

[0040] Step 2.1: Calculate the power spectral density of the noise introduced by atmospheric turbulence in the Hartmann wavefront sensor and calculate the cutoff frequency at which 96% of the total power is generated. .

[0041] Step 2.2, Round up to the initial frequency of the voltage control signal, and generate an amplitude of every 20 Hz upwards. The periodic voltage control signal is calculated based on the grouping of the drivers in step 1. The total number of drivers in each group is calculated. (Each group The values of may be the same or different), generate a group of sinusoidal voltage signals with the same amplitude, and the frequencies of the group of sinusoidal voltage signals are , remember The first in the group The voltage control signal is , in practical applications, the voltage signal is a discrete time signal, is a discrete time variable.

[0042] Step 3: According to the driver group number in step 1, apply the corresponding voltage control signal in step 2 to the corresponding driver so that all drivers are driven. Record the wavefront sensor slope signal after each group of drivers is driven, which is recorded as , representing the The slope signal of the wavefront sensor corresponding to the group voltage applied, any discrete time time, Contains all subaperture slope information.

[0043] Step 4: Perform bidirectional filtering on the wavefront sensor slope signal recorded in step 3 to restore the slope signal corresponding to each driver, calculate the phase difference between each slope signal and its corresponding voltage control signal, truncate the voltage control signal, implement phase compensation and demodulation of the control signal, and obtain the deformable mirror response matrix. This specifically includes:

[0044] Step 4.1, select any set of drives , using the Slope data corresponding to the group driver , according to the number of drivers in the group ,design The passing frequencies are The FIR bandpass filter (finite length unit impulse response digital filter) has a passband bandwidth of 4Hz; the design criteria are: the FIR filter has small ripple and a moderate transition band drop speed. Filter and get Slope data , For the The first in the group The effective wavefront sensor slope signal generated by each driver, correspondingly, The corresponding control signal is the frequency in step 2.2. The amplitude is Voltage control signal From this, we can get the effective wavefront sensor slope signal corresponding to all drivers and the voltage control signal corresponding to each driver (Get the voltage control signal of one group After that, other groups reuse the voltage control signal and amplitude; total number of drivers in each group At different times, the voltage is Generated; and when the value of N is different, the amplitude of each group is A).

[0045] Step 4.2, calculate the slope data after filtering The phase of Refers to The first in the group A driver, and the corresponding voltage control signal Phase subtraction gives the phase difference between the two , add the voltage control signal phase to Get a new voltage control signal (data set), realizing the slope signal (data set) with the new voltage control signal alignment.

[0046] Step 4.3, repeat steps 4.1-4.2 until the slope data corresponding to all drivers are filtered and the filtered slope data is phase-aligned with the truncated voltage control signal, finally obtaining the aligned voltage signals of all drivers and all slope signals corresponding to each driver.

[0047] Step 4.4, combine the frequency of the voltage control signal and use the formula , calculate the deformable mirror response matrix ;

[0048] in, For the The drive in the The slope signal of the sub-aperture, For the The voltage control signal corresponding to each driver (here Represents the total number of drivers , and the group number mentioned above 、 different), is the total length of the voltage control signal, is a discrete time variable.

[0049] Figure 2a 、 Figure 2b 、 Figure 2c The response matrices of the deformable mirror are given in three cases: without external disturbance, with disturbance using modulation method, and with disturbance using long exposure method. Figure 3a 、 Figure 3b 、 Figure 3c The residuals of wavefront restoration calculated by the response matrix without external disturbance, using the modulation method with disturbance, and using the long exposure method with disturbance are given respectively. Figure 2a 、 Figure 2b 、 Figure 2c As shown in Figure 2, the measurement accuracy of the response matrix using the modulation method is significantly higher than that using the long exposure method, and is close to the accuracy of the ideal response matrix. Figure 3a 、 Figure 3b 、 Figure 3c It can be clearly seen that the wavefront restoration residuals of the modulation method and the long exposure method differ significantly, with the RMS (root mean square) values of the three wavefront restoration residuals being 0.0064, 0.0198, and 0.0496, respectively. This result demonstrates that the voltage modulation method improves restoration accuracy by approximately 2.5 times compared to the long exposure method. In summary, the present invention achieves improved response matrix measurement accuracy through modulation.

[0050] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented using various computer languages.

[0051] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0052] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0053] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0054] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0055] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for measuring the slope response matrix of a deformable mirror based on voltage modulation, characterized in that: include: Step 1: Calculate the influence range of a single actuator based on the deformable mirror parameters. The actuators are grouped based on the criterion that no other actuators are within twice the influence range of a single actuator. Step 2: Based on the sampling frequency of the Hartmann wavefront sensor, the frequency response characteristics of the deformable mirror, and the power spectrum density of the noise introduced by atmospheric turbulence, a set of sinusoidal voltage signals for controlling the deformable mirror is generated as voltage control signals; Step 3: Apply the corresponding voltage control signal in step 2 to the corresponding driver according to the driver group number in step 1, so that all drivers are driven; record the wavefront sensor slope signal after each group of drivers is driven; Step 4: Perform bidirectional filtering on the wavefront sensor slope signal in step 3 to restore the slope signal corresponding to each driver, calculate the phase difference between each slope signal and its corresponding voltage control signal, truncate the voltage control signal, and obtain the deformable mirror response matrix.

2. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 1, characterized in that: In step 1, the minimum spacing method is used to divide the actuator into groups, each containing Drive, The group drive coordinates are ,in, For the The coordinates of the first drive of the group, For the Set the coordinates of the second drive, For the Group The coordinates of the drive.

3. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 2, characterized in that: Use the minimum spacing method to divide the drive into Groups, including: Step 1.1, determine the distribution of the deformable mirror actuator, choose a square distribution with a size of , the pole spacing of the driver is , the crosslink value of the driver is , the effective influence range of a single driver is calculated as , choose the distance between them as The drives are grouped together; Step 1.2, assume , which means that every two drives are selected to enter the current group, and the group number is finally obtained. ; in, is the row coordinate of the driver distribution, is the column coordinate of the driver distribution, The drive group number corresponds to the actual grouping of each drive.

4. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 3, characterized in that: In step 2, the process of generating a sinusoidal voltage signal includes: Step 2.1: Calculate the power spectral density of the noise introduced by atmospheric turbulence in the Hartmann wavefront sensor and calculate the cutoff frequency at which 96% of the total power is generated. ; Step 2.2, Round up to the initial frequency of the voltage control signal, and generate an amplitude of every 20 Hz upwards. The periodic voltage control signal is calculated based on the grouping of the drivers in step 1. The total number of drivers in each group is calculated. , generating a set of sinusoidal voltage signals with the same amplitude, the frequencies of which are , No. The first The voltage control signal is , is a discrete time variable.

5. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 4, characterized in that: Step 3 includes: the wavefront sensor slope signal after each set of drivers is driven is , For the The slope signal of the wavefront sensor corresponding to the group voltage applied, any discrete time time, Contains all subaperture slope information.

6. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 5, characterized in that: Step 4 includes: Step 4.1, select any set of drives , using the Slope data corresponding to group driver , according to the number of drivers in the group ,design The passing frequencies are FIR bandpass filter; Step 4.2, calculate the slope data after filtering The phase of For the The first in the group A driver, and the corresponding voltage control signal Phase subtraction gives the phase difference between the two , add the voltage control signal phase to Get a new voltage control signal , realize the slope signal With the new voltage control signal alignment; Step 4.3, repeat steps 4.1-4.2 until the slope data corresponding to all drivers are filtered and the filtered slope data is phase-aligned with the truncated voltage control signal, finally obtaining the aligned voltage signals of all drivers and all slope signals corresponding to each driver; Step 4.4, combine the frequency of the voltage control signal and use the formula , calculate the deformable mirror response matrix ; in, For the The drive in the The slope signal of the sub-aperture, For the The voltage control signal corresponding to each driver is is the total length of the voltage control signal, is a discrete time variable.

7. The method for measuring the slope response matrix of a deformable mirror based on voltage modulation according to claim 6, characterized in that: In step 4.1, Filter and get Slope data , For the The first The effective wavefront sensor slope signal generated by the driver is The corresponding control signal is the frequency in step 2.

2. The amplitude is Voltage control signal ; Thus, the effective wavefront sensor slope signals corresponding to all drivers and the voltage control signals corresponding to each driver are obtained. .

8. A device for measuring the slope response matrix of a deformable mirror based on voltage modulation, characterized in that: include: The driver grouping module calculates the influence range of a single driver based on the deformable mirror parameters, and groups the drivers based on the standard that no other driver exists within twice the influence range of a single driver. The voltage control signal generation module generates a set of sinusoidal voltage signals used to control the deformable mirror as voltage control signals based on the sampling frequency of the Hartmann wavefront sensor, the frequency response characteristics of the deformable mirror, and the power spectrum density of the noise introduced by atmospheric turbulence. The driving module applies the corresponding voltage control signal in step 2 to the corresponding driver according to the driver group number in step 1, so that all drivers are driven; and records the wavefront sensor slope signal after each group of drivers is driven; The response matrix acquisition module performs bidirectional filtering on the wavefront sensor slope signal in step 3 to restore the slope signal corresponding to each driver. It calculates the phase difference between each slope signal and its corresponding voltage control signal, truncates the voltage control signal, and obtains the deformable mirror response matrix.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the method for measuring the slope response matrix of a deformable mirror based on voltage modulation are implemented as claimed in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for measuring the slope response matrix of a deformable mirror based on voltage modulation are implemented as claimed in any one of claims 1 to 7.

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