High-frequency single-photon tilted wavefront detection device and method

Abstract

The application discloses a kind of high-frequency single-photon tilted wavefront detection device and method, including beam splitter, optical mask, single-photon detector, counter, data processing computer.The beam splitter is divided into multiple beams by the light beam to be measured;The optical mask is different in different positions;The single-photon detector is used to collect the light energy of the mask;The counter is counted to the output of single-photon detector;The data processing computer processes the output value of the counter;By superimposing the mask of the transmittance varying with position on the photosensitive surface of single-photon detector, the light intensity of the light spot of different centroid position is different, and the mathematical model between the output intensity of single-photon counter and the light spot position is established, so that the light intensity data of the mask is directly calculated to obtain the light spot centroid position.The method can detect the tilted wavefront information of extremely dark and weak target, greatly improve the frame frequency of wavefront detection, and reduce the demand for target light intensity.

Description

Technical Field

[0001] This invention belongs to the field of tilted wavefront detection in adaptive optics, specifically relating to a high-frequency single-photon tilted wavefront detection device and method. Background Technology

[0002] Adaptive optics technology was initially designed primarily for observing astronomical events at night to address the problem of wavefront distortion caused by atmospheric turbulence, which leads to a decrease in image quality. However, as the applications of adaptive optics have expanded, these systems need to adapt to different observation environments and conditions. For example, adaptive optics can be applied to the observation of extremely distant celestial objects and in scenarios where atmospheric turbulence changes rapidly.

[0003] Currently, tilted wavefront detection primarily relies on image sensors such as CCD and CMOS to acquire images and calculate the centroid of the wavefront before wavefront detection. In various wavefront detection applications, it is unavoidable to detect faint targets and targets whose wavefront phase is rapidly disturbed by atmospheric turbulence. When the rate of atmospheric turbulence change is rapid and the target light intensity is extremely weak, image sensors cannot acquire and output wavefront images at high speed, and the acquired wavefront images cannot clearly distinguish their contents. This leads to a decrease in the accuracy of the wavefront centroid calculation, ultimately resulting in a reduction in the accuracy of tilted wavefront information calculation.

[0004] Currently, there are also related post-processing algorithms, such as image denoising to enhance spot contrast, but these increase the system's computational load, affect the system's real-time performance, and cannot effectively improve the frequency of wavefront detection. Summary of the Invention

[0005] The technical problem this invention aims to solve is that traditional wavefront detection devices cannot quickly and accurately calculate the centroid position shift of the light spot by acquiring images, resulting in reduced wavefront detection accuracy, when used for tilted wavefront detection of extremely dark and weak targets under conditions of high-speed atmospheric turbulence.

[0006] According to one aspect of the present invention, a high-frequency single-photon tilted wavefront detection device is provided, comprising: a beam splitter prism, an optical mask, a single-photon detector, a counter, and a computer.

[0007] Optionally, the beam splitter can be a single or two.

[0008] The beam splitter is used to split the beam into multiple beams, thereby detecting the offset of the beam in the x and y directions and the intensity of the original beam.

[0009] The optical mask is used to distinguish the light intensity of light spots at different centroid positions;

[0010] The single-photon detector is used to detect the intensity of the light beam passing through the optical mask and the original intensity of the light beam.

[0011] The counter is used to count the output of the single-photon detector;

[0012] The computer is used to process the counter output.

[0013] Another aspect of the present invention provides a high-frequency single-photon tilted wavefront detection method, the method comprising the following steps:

[0014] Step 1: Assume the centroid of the light spot is located at coordinates r0, where vector r0 represents the coordinates in the x and y directions. The transmittance of the optical mask varies at different positions, and its structure function is P(r). Then, the intensity of light transmitted through the optical mask is... The light intensity distribution function is in σ is the peak intensity of the light spot, σ is the equivalent Gaussian width of the light spot, and r0 is the position of the centroid of the light spot;

[0015] Step 2: The detection efficiency of the single-photon detector is η. After detecting the light intensity transmitted through the optical mask, it outputs the light, and the output quantity is M.

[0016] Step 3: Use a counter to count the output of the single-photon detector and obtain the value N;

[0017] Step 4: The light spot is traversed to different positions of the optical mask. After detection by the single-photon detector, the output is counted by the counter to obtain the corresponding different values ​​N(r0). After linear fitting, the mathematical relationship between the centroid of the light spot and the light intensity data transmitted through the optical mask is obtained as r0=kN(r0)+b, where k is the coefficient of the equation and b is a constant term.

[0018] Step 5: Randomly assign a spot position and use the light intensity data transmitted through the optical mask to solve the equation to calculate the centroid coordinates of the spot.

[0019] Step 6: Characterize the tilted wavefront information based on the offset of the centroid position of the light spot.

[0020] The principle of this invention is based on the change in the transmittance of the mask, which reflects the different light intensities of the beam passing through the mask at different centroid positions. An equation is then fitted to inversely deduce the centroid position. A highly sensitive single-photon detector at the back end can detect targets with extremely low light intensity.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The device of the present invention uses an optical mask, and the change of the centroid position of the light spot at different positions is directly reflected by the change of the transmittance of the mask. Therefore, this method can significantly reduce the time for calculating the centroid of the light spot.

[0023] (2) The present invention uses a single-photon detector as the back-end photoelectric sensor, which has high sensitivity and fast output speed. The wavefront detection speed depends on the bandwidth of the single-photon detector, which is much higher than the output frame rate of traditional photoelectric sensors such as CCD and CMOS cameras. It is more suitable for application in scenarios that require fast response, such as when atmospheric turbulence changes drastically.

[0024] (3) The present invention has stronger adaptability, such as being more suitable for high-speed and strong turbulence observation conditions and wavefront detection of faint targets.

[0025] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a high-frequency single-photon tilted wavefront detection device according to the present invention;

[0028] Figure 2 This is a schematic diagram of a high-frequency single-photon tilted wavefront detection device with dual beam-splitting prisms provided in an embodiment of the present invention.

[0029] Figure 3 This is a graph showing the relationship between the number of cycles of the binary optical mask and the centroid error in an embodiment of the present invention.

[0030] Figure 4 This is a schematic diagram of a binary optical mask provided in an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] like Figure 1The diagram shows a schematic of a high-frequency single-photon tilted wavefront detection device according to the present invention. The device includes a beam splitter, an optical mask, a single-photon detector, a counter, and a data processing computer. Its features include: the target beam is split into three beams by the beam splitter; one beam directly enters the single-photon detector to detect the original light intensity; the other two beams pass through the masks in their respective directions to reach the target surface of the single-photon detector. The light intensity of the target beams at different centroid positions after passing through the masks is different, thus the output of the single-photon detector is different. The output signal of the single-photon detector is sent to the counter for counting and then transferred to the computer for processing. The computer fits the relevant parameters of the equation based on the correspondence between the counter output value and the actual centroid position. Based on the fitted polynomial equation, the centroid coordinates of the beam in the x and y directions can be directly calculated from the light intensity information of the target beam passing through the mask.

[0033] Figure 2 This is a schematic diagram of the structure of a high-frequency single-photon tilted wavefront detection device provided by an embodiment of the present invention, as shown below. Figure 2 As shown, the device includes:

[0034] Two binary optical masks, each with a transmittance varying with its periodic position, resulting in different light intensities as the beam passes through the masks at different positions; a fast-reflecting mirror, to which a signal is applied to induce an angular shift, thus shifting the centroid position of the beam; two beam splitters, which divide the light to be measured into three beams; three single-photon detectors, two of which detect the light intensity passing through the masks in the x and y directions respectively, and one of which detects the intensity of the original beam; three counters, which sample the output voltages of the single-photon detectors, convert them into numerical values, and send them to a computer for processing; and a computer, which processes and calculates the light intensity variation information and determines the centroid position of the beam spot.

[0035] The specific implementation method is as follows:

[0036] Step 1: In the specific implementation verification of this invention, a binary optical mask is used. Since the light intensity of the light spot passing through the mask is discretely sampled by the mask, the obtained centroid coordinate measurement value will have a fundamental error compared to the theoretical value. Furthermore, the magnitude and distribution of this error will vary depending on the mask's structure function and the size of the light spot. The relationship between the error RMS value and the number of mask periods and the light spot size is as follows: Figure 3As shown. When the spot size is fixed, the more mask cycles there are, the smaller the discrete sampling error, and therefore the smaller the final centroid position error RMS value. When the number of mask cycles is fixed, the larger the spot size, the smaller the impact of discrete sampling error, and thus the smaller the resulting centroid position error RMS value. Considering the variation law of sampling error, process difficulty, and cost, the binary optical mask used has a total of 25 cycles, with each cycle being 52µm long. The length of the light-blocking part in each cycle increases linearly with a base of 2µm, as shown. Figure 4 As shown, the white area has 100% transmittance, and the black area has 0% transmittance. The beam splitter has a spectral splitting ratio of 50%.

[0037] The second step, to facilitate computer calculation, is to first consider a one-dimensional form, assuming the coordinates of the centroid of the light spot in the x and y directions are r and r, respectively. x and r y The structure function of the mask is P(x), and the light intensity distribution function is... x' and y' represent the components of the light spot intensity in the x and y directions, respectively. Let σ be the peak intensity of the light spot, σ be the equivalent Gaussian width of the light spot, y0 be the initial coordinates of the light spot centroid in the y-direction, and x be the coordinates of the light spot centroid in the x-direction. By controlling the fast-reflection mirror, the light spot coordinates are traversed along the x-direction of the mask, obtaining the light intensity data transmitted through the mask at different positions of the light spot in the x-direction. The output quantity of a single-photon detector after detecting the corresponding light intensity is M x The counter counts to obtain the numerical value N corresponding to the light intensity of light spots passing through the mask at different centroid coordinates. x Then, by performing a linear fit on the data, the equation r is obtained. x =k x N x +b x k x Let b be the coefficient of the equation. x This is a constant term.

[0038] The third step, as described in the second step, yields the equation relating the counter output data r to the light intensity transmitted through the mask at different centroid positions of the light spot in the y-direction. y =k y N y +b y k y Let b be the coefficient of the equation. y This is a constant term.

[0039] Fourth step: Randomly assign the position of the light spot, and substitute the output value of the counter into the equations described in the second and third steps to calculate the horizontal and vertical coordinates of the centroid position of the light spot.

[0040] The fifth step is to characterize the tilt phase difference based on the offset of the centroid coordinates of the light spot.

[0041] The specific embodiments described above are not intended to limit the scope of protection of this invention. 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 substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-frequency single-photon tilted wavefront detection device, comprising a beam splitter, an optical mask, a single-photon detector, a counter, and a data processing computer; wherein, A beam splitter is used to split a target beam into three beams, thereby detecting the beam's offset in the x and y directions as well as the intensity of the original beam. Optical masks are used to distinguish the light intensity of light spots at different centroid positions; A single-photon detector is used to detect the intensity of the target beam transmitted through the optical mask as well as the original intensity of the target beam. The counter is used to count the output of the single-photon detector; The data processing computer is used to process the counter output. The key feature is that the target beam is split into three beams by a beam splitter. One beam directly enters the single-photon detector to detect the original light intensity, while the other two beams pass through optical masks in their respective directions to reach the target surface of the single-photon detector. The light intensity of the target beams at different centroid positions after passing through the optical masks is different, thus the output of the single-photon detector is different. The output signal of the single-photon detector is sent to a counter for counting and then transferred to a computer for processing. The computer fits the relevant parameters of the equation based on the correspondence between the counter output value and the actual centroid position corresponding to the original light intensity. Based on the fitted polynomial equation, the centroid coordinates of the spot in the x and y directions can be directly calculated using the light intensity information of the target beam passing through the optical mask.

2. The high-frequency single-photon tilted wavefront detection method according to claim 1, characterized in that: The beam splitter splits light into three beams, thereby detecting the original light intensity of the light spot and the light intensity passing through the optical mask in the x and y directions.

3. The high-frequency single-photon tilted wavefront detection method according to claim 1, characterized in that: The optical mask is an optical mask whose transmittance varies with position. Therefore, when the light spot is at different positions on the optical mask, the transmitted light intensity and energy are different.

4. The high-frequency single-photon tilted wavefront detection method according to claim 1, characterized in that: The single-photon detector used is a high-sensitivity, high-bandwidth photoelectric sensor to achieve wavefront detection of high-frame-rate, extremely weak light targets.

5. A method for detecting a high-frequency single-photon tilted wavefront using the high-frequency single-photon tilted wavefront detection device according to any one of claims 1-4, characterized in that: The method includes the following steps: Step 1: Assume the centroid of the light spot is located at coordinates r0, where vector r0 represents the coordinates in the x and y directions. The transmittance of the optical mask varies at different positions, and its structure function is P(r). Then, the intensity of light transmitted through the optical mask is... The light intensity distribution function is in σ is the peak intensity of the light spot, σ is the equivalent Gaussian width of the light spot, and r0 is the position of the centroid of the light spot; Step 2: The detection efficiency of the single-photon detector is η. After detecting the light intensity transmitted through the optical mask, it outputs the light, and the output quantity is M. Step 3: Use a counter to count the output of the single-photon detector and obtain the value N; Step 4: The light spot is traversed to different positions of the optical mask. After detection by the single-photon detector, the output is counted by the counter to obtain the corresponding different values ​​N(r0). After linear fitting, the mathematical relationship between the centroid of the light spot and the light intensity data transmitted through the optical mask is obtained as r0=kN(r0)+b, where k is the coefficient of the equation and b is a constant term. Step 5: Randomly assign a spot position and use the light intensity data transmitted through the optical mask to solve the equation to calculate the centroid coordinates of the spot. Step 6: Characterize the tilted wavefront information based on the offset of the centroid position of the light spot.

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