A lens astigmatism measuring method and device based on liquid lens and umbrella-shaped target

Abstract

The application relates to the technical field of optical measurement, in particular to a lens astigmatism measurement method and device based on a liquid lens and an umbrella-shaped target, which comprises the following steps: first, the power of the electrically controlled liquid lens is scanned, and the target power of the electrically controlled liquid lens is found by using image definition; then, the image of the umbrella-shaped target is collected under the target power, the target angle with the highest definition is found by combining polar coordinate transformation and definition analysis; finally, the power range is constructed based on the target power, scanning and polar coordinate transformation are carried out in the power range, the vertical best power is extracted, and the lens astigmatism is calculated by using the target power and the vertical best power. The application decomposes the compound astigmatism into two independent optimization problems in orthogonal directions, avoids the measurement instability caused by the coupling of multiple parameters in the traditional method, discards the complex mechanical structure and optical path structure, and does not need artificial subjective judgment. The application has the advantages of high measurement efficiency, high measurement precision and low cost.

Description

A method and apparatus for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target. Technical Field

[0001] This application relates to the field of optical measurement technology, specifically a method and apparatus for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target. Background Technology

[0002] Astigmatism testing is a core challenge in measuring spectacle lens parameters. Current mainstream testing methods include:

[0003] (1) Subjective refraction method, representative techniques: FanChart Test and cross-cylinder test. The principle is that the patient observes the pattern of the astigmatic disc and subjectively judges which direction the lines are clearest. The optometrist gradually adjusts the spherical and cylindrical lenses in the trial frame based on the patient's feedback. The typical equipment is the phoropter (opconCV-5000).

[0004] (2) Hartmann method, represented by technologies such as automatic refractometers and wavefront aberrometers. Its principle is to project a dot matrix light source onto a lens through a microlens array and calculate astigmatism based on the displacement of the image points. It requires precise calibration of the distance between the microlens and the sensor, making the system complex (requiring 200+ sampling points) and costly.

[0005] (3) Lens transmission measurement method, representative technology: Lensometer, principle: the change in the refraction angle of light after passing through the lens being measured reflects the focal length. Rotate the prism or probe to find the maximum / minimum focal length meridian. Relies on a stepper motor (response time > 500ms), and there is a mechanical backlash error (axis position error ±3°). A typical device is the Nidek LM-990A automatic focimeter.

[0006] The aforementioned existing technologies either rely on subjective human testing or suffer from drawbacks such as low speed due to mechanical structure movement, incomplete discrete angle sampling, and increased costs due to complex optical paths. Summary of the Invention

[0007] In view of this, the purpose of this application is to provide a method and apparatus for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target, so as to solve the problems in the prior art.

[0008] To achieve the above objectives, this application adopts the following technical solution:

[0009] This application discloses a method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target, comprising the following steps:

[0010] The system controls a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, and extracts the sharpness of multiple umbrella-shaped target images from the image sequence, and takes the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length. The imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order.

[0011] The imaging system is controlled to acquire a target focal length image of the umbrella-shaped target using the target focal length, and the target focal length image is transformed into polar coordinates to obtain a polar coordinate image containing stripes representing multiple angles; and the sharpness analysis of multiple stripes in the polar coordinate image is performed to obtain the target angle corresponding to the stripe with the maximum sharpness.

[0012] The imaging system is controlled to acquire multiple frames of scanned images based on the target focal length, the target stripes of the multiple frames of scanned images are located based on the target angle, the vertical optimal focal length is determined based on the sharpness of the target stripes of the multiple frames of scanned images, and the lens astigmatism of the lens under test is calculated based on the target focal length and the vertical optimal focal length.

[0013] In one embodiment of this application, controlling the imaging system to acquire multiple frames of scanned images based on the target focal length, and locating target stripes in the multiple frames of scanned images based on the target angle, includes:

[0014] The process of determining the optimal vertical focal length based on the sharpness of target fringes in multi-frame scanned images, and calculating the lens astigmatism of the lens under test based on the target focal length and the optimal vertical focal length, includes:

[0015] Construct based on the target focal length The focal range of the center ,in, This represents the unit of focal length;

[0016] Within the focal range The focal length of the liquid lens is scanned and adjusted with a target step size to obtain multiple scan images corresponding to multiple scan adjustment points, wherein the multiple scan adjustment points are extracted from the focal length range.

[0017] In one embodiment of this application, determining the optimal vertical focal length based on the sharpness of target stripes in multi-frame scanned images, and calculating the lens astigmatism of the lens under test based on the target focal length and the optimal vertical focal length, includes:

[0018] Perform polar coordinate transformation on the scanned image to obtain a scanned polar coordinate image;

[0019] Based on the target angle Extracting vertical angle The target stripe corresponding to the vertical angle is extracted from the scanned polar coordinate image, and the sharpness of the target stripe is calculated, wherein the sharpness is the average gradient of multiple pixels of the target stripe, and the vertical angle is... The mathematical expression is:

[0020]

[0021] The focal length of the scanned image containing the target stripe with the highest clarity is taken as the optimal vertical focal length. ;

[0022] Based on the aforementioned vertical optimal focal length and the target focal length Calculate the lens astigmatism of the lens under test. , .

[0023] In one embodiment of this application, controlling a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extracting the sharpness of multiple umbrella-shaped target images from the image sequence, and using the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length, includes:

[0024] Multiple focal length points are extracted from the pre-constructed full focal length range with a target step size, and the liquid lens is controlled based on the multiple focal length points to obtain an image sequence of umbrella-shaped targets corresponding to the multiple focal length points.

[0025] Extract the region of interest (ROI) at the center of each frame of the umbrella-shaped target image in the image sequence, calculate the gray-level variance of the ROI, and measure the sharpness of the umbrella-shaped target image based on the gray-level variance.

[0026] The umbrella-shaped target image with the largest grayscale variance is taken as the umbrella-shaped target image with the highest clarity, and the focal length corresponding to the umbrella-shaped target image with the highest clarity is taken as the target focal length.

[0027] In one embodiment of this application, the target focal length image is subjected to polar coordinate transformation to obtain a polar coordinate image containing stripes representing multiple angles, including:

[0028] Using the center point coordinates of the target focal length image as the origin of the polar coordinates ;

[0029] Based on the origin of the polar coordinates The target focal length image is transformed into a polar coordinate system to obtain a polar coordinate image containing stripes representing multiple angles. The polar coordinate image The mathematical expression is:

[0030]

[0031]

[0032] In the formula, Indicates the polar angle. Indicates the polar radius. Represents the pixel coordinates of the target focal length image.

[0033] In one embodiment of this application, a sharpness analysis is performed on multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the highest sharpness, including:

[0034] Extract stripes corresponding to multiple angles from the polar coordinate image;

[0035] Extract column vectors of multiple pixels from the stripes corresponding to each angle, and calculate the gradient sharpness of each column vector. , wherein the gradient sharpness The mathematical expression is:

[0036]

[0037] In the formula, This represents the function for finding the average. Represents the Sobel gradient;

[0038] Gradient sharpness based on multiple angles Constructing a resolution map ,in, Indicates angle;

[0039] From the resolution map Extracting gradient sharpness The target angle corresponding to the largest stripe.

[0040] In one embodiment of this application, controlling a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence includes:

[0041] The temperature value at the current time point is obtained, and the target focal length value is extracted from the focal length scanning sequence; the fitting parameters and temperature compensation coefficients are extracted from the pre-built focal length mapping model.

[0042] The initial control voltage is calculated based on the fitted parameters and the target focal length value. The initial control voltage The mathematical expression is:

[0043]

[0044] In the formula, Indicates the focal length of the liquid lens. Represents the proportional fitting parameters. Indicates the fitting parameters for the deviation term;

[0045] Based on the temperature compensation coefficient The temperature value at the current time point and reference temperature value For the initial control voltage Compensation is performed to obtain the compensation voltage. The mathematical expression for the compensation voltage is:

[0046]

[0047] Based on the compensation voltage, a pre-built imaging system is used to acquire image sequences of an umbrella-shaped target using a pre-built focal length scanning sequence.

[0048] In one embodiment of this application, the method for constructing the focal length mapping model includes:

[0049] Standard lenses of various focal lengths are installed into the imaging system; the imaging system containing the standard lenses is controlled by a pre-built voltage sequence to perform image acquisition and obtain target image sequence samples;

[0050] Extract the optimal voltage value sample corresponding to the maximum clarity from the target image sequence sample, and construct a data sample based on the optimal voltage value sample, temperature value and timestamp;

[0051] A sample set is constructed based on data samples from multiple standard lenses, and outlier removal and data completion are performed on the sample set to obtain a standard sample set.

[0052] The parameter model of the imaging system is fitted using the least squares method based on the standard sample set to obtain the fitted parameters, wherein the mathematical expression of the parameter model is:

[0053]

[0054]

[0055] In the formula, Indicates the power of a standard lens. and All represent system constants. Indicates voltage;

[0056] Calculate the theoretical driving voltage value The difference between the actual voltage value and the actual voltage value is used to obtain a voltage difference sample. It calculates the difference between the actual temperature value and the reference temperature value to obtain a temperature difference sample. ;

[0057] A linear fitting model is constructed for voltage difference and temperature difference, wherein the mathematical expression of the linear fitting model is:

[0058]

[0059] Based on the voltage difference sample and the temperature difference sample The linear fitting model is fitted to obtain the temperature compensation coefficient. ;

[0060] Based on the parameter model, fitting parameters, and temperature compensation coefficient of the imaging system Construct a focal length mapping model.

[0061] In one embodiment of this application, the imaging system includes a light source, a light homogenizing device, an umbrella-shaped target, a small aperture aperture, a lens under test, a liquid lens, an imaging lens, a junction box, and an image sensor arranged sequentially along the optical path.

[0062] This application also provides a lens astigmatism measurement device based on a liquid lens and an umbrella-shaped target, comprising:

[0063] A focal length determination module is used to control a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extract the sharpness of multiple umbrella-shaped target images from the image sequence, and take the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length. The imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order.

[0064] The focal length determination module is used to control the imaging system to acquire a target focal length image of the umbrella-shaped target based on the target focal length, perform polar coordinate transformation on the target focal length image to obtain a polar coordinate image containing stripes representing multiple angles, and perform sharpness analysis on the multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the maximum sharpness.

[0065] The astigmatism determination module is used to control the imaging system to acquire multiple frames of scanned images based on the target focal length, locate the target stripes in the multiple frames of scanned images based on the target angle, determine the vertical optimal focal length based on the sharpness of the target stripes in the multiple frames of scanned images, and calculate the lens astigmatism of the lens under test based on the target focal length and the vertical optimal focal length.

[0066] The beneficial effects of this application are as follows: This application discloses a method and apparatus for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target. The process of this application is divided into three stages. First, the focal length is scanned using an electrically controlled liquid lens, and the target focal length of the liquid lens is found by utilizing image sharpness. Then, at the target focal length, an image of the umbrella-shaped target is acquired. Using polar coordinate transformation, the rays of the umbrella-shaped target image are converted into horizontal stripes. By extracting the sharpness of each horizontal stripe, the target angle with the highest sharpness is found. Finally, a focal length range is constructed based on the target focal length, and scanning and polar coordinate transformation are performed within the focal length range to extract the vertically optimal focal length. The lens astigmatism is calculated using the target focal length and the vertically optimal focal length. This application decomposes complex astigmatism into two independent optimization problems in orthogonal directions, avoiding the measurement instability caused by multi-parameter coupling in traditional methods. In addition, this application uses an electrically controlled hydraulic lens to adjust the optical path, eliminating complex mechanical and optical path structures and eliminating the need for subjective human judgment. It has the advantages of high measurement efficiency, high measurement accuracy, and low cost. Attached Figure Description

[0067] The present application will be further described below with reference to the accompanying drawings and embodiments:

[0068] Figure 1 is a schematic diagram of a lens astigmatism measurement system based on a liquid lens and an umbrella-shaped target according to an embodiment of this application.

[0069] Figure 2 is a schematic diagram of the geometric design of the umbrella-shaped target shown in the embodiments of this application;

[0070] Figure 3 is a flowchart illustrating a method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target in one embodiment of this application;

[0071] Figure 4 is a flowchart illustrating the target focal power measurement principle of a lens under test in one embodiment of this application.

[0072] Figure 5 is a flowchart of the measurement process of the target angle of the lens under test in one embodiment of this application;

[0073] Figure 6 is a schematic diagram of a polar coordinate image in one embodiment of this application;

[0074] Figure 7 is a schematic diagram of the measurement process of lens astigmatism in one embodiment of this application;

[0075] Figure 8 is an optical path diagram of an imaging system according to an embodiment of this application. Detailed Implementation

[0076] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0077] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the layers related to this application and are not drawn according to the actual number, shape and size of the layers in the actual implementation. In the actual implementation, the form, number and proportion of each layer can be arbitrarily changed, and the layer layout may also be more complex.

[0078] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these specific details.

[0079] Figure 1 is a schematic diagram of a lens astigmatism measurement system based on a liquid lens and an umbrella-shaped target according to an embodiment of this application. As shown in Figure 1, the imaging system of this application includes an illumination subsystem, a sample optical path subsystem, an imaging subsystem, and an image processing and display subsystem.

[0080] The sample optical path subsystem includes a sample tray 201 and a sample under test 202; the imaging subsystem includes a liquid lens 301, a rear imaging lens 302, a junction box 303, and a CMOS image sensor 304; the image processing and display subsystem includes an embedded processor 401 and a display 402, which together constitute a compact optical and control collaborative system for achieving fully automatic measurement of lens power.

[0081] The light source module 101 emits 530nm green monochromatic light, which enters the light homogenizer 102 to provide uniform illumination, ensuring that the reticle 104 and the high-resolution target 103 obtain high-quality optical patterns. This pattern is refracted by the sample under test 202 (placed in the sample tray 201), which integrates a 4.5mm small aperture diaphragm to limit the beam and reduce positioning errors, while the low contact force design protects the soft contact lens.

[0082] The liquid lens 301 dynamically adjusts its focal length via voltage control to compensate for the focal length of the sample 202 under test, ensuring that the target pattern is clearly imaged onto the fixed image plane of the CMOS image sensor 304 through the rear imaging lens 302 and the adapter ring 303. The CMOS image sensor 304 captures the high-resolution image and transmits it to the embedded processor 401, which analyzes the image using a multi-index sharpness algorithm, controls the voltage of the liquid lens 301, and calculates the focal length parameters. The final result is presented through the display 402 and output via the storage / communication interface, completing the closed-loop process of measurement, display, and data management.

[0083] Figure 2 is a geometric design schematic diagram of the umbrella-shaped target shown in the embodiments of this application. As shown in Figure 2, the target includes a central bright spot (5mm in diameter, high brightness ≥500cd / m², used for SPH sharpness judgment) and 36 radial lines (1mm in width, 10° interval, used for...). The image includes a directional analysis module and a circular outer frame (2mm line width, 60mm diameter, serving as a reference boundary for polar coordinate transformation). The background is low-reflectivity black (reflectivity <5%), placed within the reticle target module. This design ensures that directional blur caused by astigmatism is significantly represented in the image, facilitating subsequent polar coordinate analysis.

[0084] Figure 3 is a flowchart illustrating a method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target in one embodiment of this application. As shown in Figure 3, the method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target in this embodiment includes the following steps:

[0085] S310, control a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extract the sharpness of multiple umbrella-shaped target images from the image sequence, and take the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length, wherein the imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order;

[0086] The first stage is For spherical power measurement, the system scans the liquid lens power starting from -10D in 0.05D steps, while simultaneously acquiring a 30fps high-speed image sequence. For the central bright area (20×20 pixel ROI) of each frame, the grayscale variance is calculated as a sharpness indicator. When the variance reaches its minimum value, the corresponding liquid lens power is recorded as [the minimum value]. value.

[0087] Furthermore, the focal length of the liquid lens in this application is essentially adjusted by voltage. A pre-constructed focal length mapping model characterizes the relationship between voltage and focal length. Additionally, temperature compensation can be performed, making the focal length adjustment process more precise. Specifically, the use and construction method of the fitting model are described later.

[0088] S320, the imaging system is controlled to acquire a target focal length image of the umbrella-shaped target based on the target focal length, and the target focal length image is transformed into polar coordinates to obtain a polar coordinate image containing stripes representing multiple angles; and the sharpness analysis of multiple stripes in the polar coordinate image is performed to obtain the target angle corresponding to the stripe with the maximum sharpness.

[0089] The second stage is Axial measurement, setting the liquid lens to... For the corresponding focal length, high-resolution standard images are acquired and preprocessed (noise reduction, contrast enhancement). Then, polar coordinate transformation is performed to convert radial lines into horizontal stripes. Gradient sharpness in each direction is analyzed column by column within the angular domain (0°-180°) to determine the angle corresponding to maximum sharpness. value.

[0090] S330, based on the target focal length, control the imaging system to acquire multiple frames of scanned images, locate the target stripes in the multiple frames of scanned images based on the target angle, determine the vertical optimal focal length based on the sharpness of the target stripes in the multiple frames of scanned images, and calculate the lens astigmatism of the lens under test based on the target focal length and the vertical optimal focal length.

[0091] The third stage is Cylindrical power measurement and calculation vertical direction ( ),exist A fine-tuning scan within ±2D range is performed at the reference focal length to find the optimal focal length that maximizes vertical sharpness. The difference is value.

[0092] The methods and principles of the above three stages will be explained in detail below.

[0093] Phase 1:

[0094] In the first phase, The principle of spherical power measurement is based on the isotropic focusing characteristics of a central bright spot. In the measurement optical path, a circular central bright spot with a diameter of 5mm serves as a point light source. When the light emitted from this spot passes through the astigmatic lens being measured, the spherical component... It produces an equal refractive effect in all directions, with no direction selectivity. The light then enters a liquid-focusable lens for focal compensation, and finally forms an image on the image sensor.

[0095] Figure 4 is a flowchart illustrating the target focal length measurement principle of a lens under test in one embodiment of this application. As shown in Figure 4, the target focal length measurement process includes:

[0096] S410 extracts multiple focal length points from a pre-constructed full focal length range with a target step size, and controls the liquid lens based on the multiple focal length points to obtain an image sequence of the umbrella-shaped target corresponding to the multiple focal length points.

[0097] Specifically, a focal length scanning strategy is adopted, starting from -10.0D and increasing in steps of 0.05D to +10.0D. For each focal length point, the image is acquired after waiting 20ms for the lens to stabilize.

[0098] S420, extract the region of interest at the center position of each frame of the umbrella-shaped target image in the image sequence, calculate the gray-level variance of the region of interest, and measure the sharpness of the umbrella-shaped target image based on the gray-level variance;

[0099] S430, the umbrella-shaped target image with the largest grayscale variance is taken as the umbrella-shaped target image with the highest clarity, and the focal length corresponding to the umbrella-shaped target image with the highest clarity is taken as the target focal length.

[0100] Specifically, the grayscale variance is calculated by extracting the central 20×20 pixel ROI region. As an indicator of sharpness, when the liquid lens power precisely compensates for the spherical component of the astigmatic lens, the central bright spot reaches its optimal focus state, at which point the bright spot edges are sharpest, the contrast between light and dark is strongest, and the grayscale variance is smallest. The system records the liquid lens power corresponding to the minimum variance as... The measurement results show that the measurement accuracy can reach ±0.05D.

[0101] Phase Two:

[0102] In the second phase, The axis measurement principle utilizes the direction-selective imaging characteristics of astigmatic lenses. Thirty-six equally angularly distributed radial lines, after passing through the astigmatic lens, form a clear image along the principal axis and a blurred image along the secondary axis, exhibiting a significant difference in direction selectivity. A liquid lens is fixed at SPH (Special Power Phosphorus) to eliminate the influence of the spherical component, ensuring the purity of the measurement.

[0103] Figure 5 is a flowchart of the measurement process of the target angle of the lens under test in one embodiment of this application. As shown in Figure 5, the measurement process of the target angle includes:

[0104] S510, the imaging system is controlled to acquire a target focal length image of the umbrella-shaped target using the target focal length;

[0105] The measurement algorithm first sets the liquid lens to... To determine the focal length, acquire a high-resolution image of 2592×1944 and preprocess it (grayscale conversion, filtering, etc.), then perform polar coordinate transformation.

[0106] S520, using the center point coordinates of the target focal length image as the origin of the polar coordinates. ;

[0107] S530, based on the polar coordinate origin The target focal length image is transformed into a polar coordinate system to obtain a polar coordinate image containing stripes representing multiple angles. The polar coordinate image The mathematical expression is:

[0108]

[0109]

[0110] In the formula, Indicates the polar angle. Indicates the polar radius. Represents the pixel coordinates of the target focal length image.

[0111] The polar coordinate transformation algorithm is the core innovation, transforming the original rectangular coordinate image... Convert to polar coordinates using coordinate mapping relationships. After the transformation, the original radial lines are converted into horizontal stripes, which facilitates column-by-column analysis in the angular domain. Figure 6 is a schematic diagram of a polar coordinate image in one embodiment of this application. The polar coordinate image after polar coordinate transformation is shown in Figure 6.

[0112] S540, extract stripes corresponding to multiple angles from the polar coordinate image;

[0113] The S550 extracts column vectors of multiple pixels from the stripes corresponding to each angle and calculates the gradient sharpness of each column vector. , wherein the gradient sharpness The mathematical expression is:

[0114]

[0115] In the formula, This represents the function for finding the average. Represents the Sobel gradient;

[0116] S560, based on gradient sharpness from multiple angles Constructing a resolution map ,in, Indicates angle;

[0117] S570, from the aforementioned resolution map Extracting gradient sharpness The target angle corresponding to the largest stripe.

[0118] Steps S540-S570 extract column vectors and calculate gradient sharpness for each column (corresponding to an angular direction) of the transformed image. Construct a complete resolution map Radiation in the clear direction has sharp edges, a large gradient value, and high clarity, while the opposite is true for the blurry direction. The principal axis angle of astigmatism is determined by finding the maximum value in the clarity spectrum. The measurement accuracy can reach ±1°.

[0119] Phase Three:

[0120] In the third stage, Based on focal length, calculate the vertical direction. correspond Scan the additional focal length (-2D to +2D, step size 0.05D), calculate the mean gradient of the column, and the maximum value corresponds to the total focal length. This achieves decoupling of cylindrical power with an accuracy of ≤0.1D.

[0121] The principle of cylinder power measurement is based on the bifocal characteristic of astigmatic lenses, namely, the focal power along the principal axis. and secondary axis direction focal length The difference The measurement strategy employs a bidirectional independent optimization method: principal axis direction ( The optimal focal length has been determined during the SPH measurement phase, in the secondary axis direction ( The optimal focal length (+90°) needs to be determined by liquid lens focal length scanning.

[0122] Figure 7 is a schematic diagram of the measurement process of lens astigmatism in one embodiment of this application. As shown in Figure 7, the process for determining astigmatism includes:

[0123] S710, constructing with the target focal length The focal range of the center ,in, This represents the unit of focal length;

[0124] S720, in the focal length range The focal length of the liquid lens is scanned and adjusted with a target step size to obtain multiple scan images corresponding to multiple scan adjustment points, wherein the multiple scan adjustment points are extracted from the focal length range.

[0125] S730, Perform polar coordinate transformation on the scanned image to obtain a scanned polar coordinate image;

[0126] S740, based on the target angle Extracting vertical angle The target stripe corresponding to the vertical angle is extracted from the scanned polar coordinate image, and the sharpness of the target stripe is calculated, wherein the sharpness is the average gradient of multiple pixels of the target stripe, and the vertical angle is... The mathematical expression is:

[0127]

[0128] The S750 uses the focal length of the scanned image of the target stripe with the highest clarity as the optimal vertical focal length. ;

[0129] S760, based on the aforementioned vertical optimal focal length and the target focal length Calculate the lens astigmatism of the lens under test. , .

[0130] In the above process, the known parameters are first obtained. and Calculate the vertical angle Then The liquid lens focal length is scanned within a range with a step size of 0.05D. For each focal length point, an image is acquired and a polar coordinate transformation is performed. The column vector corresponding to the vertical direction is extracted, and the gradient sharpness of that column is calculated. When the vertical direction achieves optimal focus, the corresponding liquid lens focal length is... , The value is calculated as follows .

[0131] The advantage of the above method lies in decomposing compound astigmatism into two independent optimization problems in orthogonal directions, avoiding the measurement instability caused by multi-parameter coupling in traditional methods. The system can also automatically determine the type of astigmatism: simple myopic astigmatism (… Simple hyperopic astigmatism ( It measures both complex astigmatism and optical distortion, and performs corresponding sign correction to ensure that the output results meet clinical standards. The measurement accuracy can reach ±0.05D, meeting the accuracy requirements for eyeglass fitting.

[0132] Specifically, in one embodiment of this application, the simulation process for astigmatism detection is as follows:

[0133] 1. Cases without astigmatism lenses (or without astigmatism)

[0134] Step 1: Focus on the center bright spot: Adjust the focal length of the liquid lens until the center bright spot is the clearest (at this point, the grayscale variance of the center bright spot is the smallest).

[0135] Step 2: Capture the image and perform a polar coordinate transformation. Capture the image at the optimal focal length. Perform a polar coordinate transformation centered on the central bright spot, converting the circular radial lines of the original image into horizontal lines in polar coordinates.

[0136] The effect of polar coordinate transformation under normal circumstances:

[0137] In a polar coordinate image, the original radial lines become horizontal parallel lines (each line represents a ray at an angle in the original image). Because there is no astigmatism, rays in all directions are equally sharp; therefore, all horizontal lines in a polar coordinate image have consistent sharpness.

[0138] After polar coordinate transformation, the circular border becomes a vertical straight line (located at the top or bottom of the polar coordinate image, depending on the transformation method).

[0139] II. Cases with astigmatic lenses

[0140] Step 1: Focus on the center bright spot (determine the SPH): Adjust the focal length of the liquid lens to make the center bright spot the sharpest. Record the focal length at this point as SPH.

[0141] Step 2: Capture the image at SPH focal length, perform polar coordinate transformation, and determine the axis position AXIS. At this time, due to the presence of astigmatism, the sharpness of rays in different directions is different.

[0142] After polar coordinate transformation, an image of horizontal lines is obtained (each line represents an angle direction).

[0143] Along the horizontal direction of the polar coordinate image ( (Axis) Analyze the sharpness of each line (e.g., calculate the gradient mean or variance of each line).

[0144] The angle corresponding to the line with the highest clarity is the axis. (Because the refractive power of astigmatic lenses is weakest in the axial direction, the rays in that direction are the clearest).

[0145] Step 3: Adjust the focus of the liquid lens to make it... The rays at +90° are the clearest (to determine astigmatism / cylindrical power). ).

[0146] Maintain spherical power Based on this, an additional focal length adjustment (cylindrical power adjustment) is added, the adjustment direction being targeted at... The +90° direction (i.e. the direction perpendicular to the axis, where the refractive power is strongest and additional correction is required).

[0147] Adjust the focal length of the liquid lens (at this point, the total focal length = (+additional focal length), until in the polar coordinate image. The horizontal line corresponding to the +90° direction is the clearest.

[0148] Record the total focal length at this moment, and subtract... That is, the cylindrical power is obtained. .

[0149] In one embodiment of this application, the focal length of the liquid lens is directly assumed above. However, in actual control, the focal length of the liquid lens is controlled by voltage. This application uses a pre-built focal length mapping model to characterize the mapping relationship between the control voltage and focal length of the liquid lens, and introduces temperature compensation to improve control accuracy. Specifically, the focal length mapping model between voltage and focal length is described below:

[0150] The preceding text describes controlling a pre-built imaging system to acquire image sequences of an umbrella-shaped target using a pre-built focal length scanning sequence, including:

[0151] (1) Obtain the temperature value at the current time point and extract the target focal value from the focal value scanning sequence; and extract the fitting parameters and temperature compensation coefficient from the pre-constructed focal value mapping model;

[0152] (2) Calculate the initial control voltage based on the fitting parameters and the target focal length value. The initial control voltage The mathematical expression is:

[0153]

[0154] In the formula, Indicates the focal length of the liquid lens. Represents the proportional fitting parameters. Indicates the fitting parameters for the deviation term;

[0155] (3) Based on the temperature compensation coefficient The temperature value at the current time point and reference temperature value For the initial control voltage Compensation is performed to obtain the compensation voltage. The mathematical expression for the compensation voltage is:

[0156]

[0157] (4) Based on the compensation voltage, the pre-built imaging system acquires an image sequence of the umbrella-shaped target using a pre-built focal length scanning sequence.

[0158] The aforementioned control process relies on a pre-constructed focal length mapping model. Before constructing the focal length mapping model, the optical path involved in this application needs to be analyzed. Figure 8 is an optical path diagram of the imaging system in one embodiment of this application; please refer to Figure 8 for understanding. Figure 8 illustrates the core optical principle and calculation model of this system for focal length measurement. The system is based on the thin lens combination theory, and achieves accurate and rapid focal length measurement by analyzing the optical characteristics of the combination of the lens under test and the liquid lens.

[0159] The imaging optical path of the system can be modeled as a variable focal length system consisting of two thin lenses, followed by an imaging module with a fixed image plane.

[0160] Fixed conjugate substrate: The object plane (reticle target) and image plane (CMOS sensor) of the system are positioned at fixed positions, forming a fixed object-image conjugate relationship. The rear imaging lens, as part of this fixed imaging module, ensures clear imaging of the target in the reference state.

[0161] When the target is clearly imaged, the following conditions must be met:

[0162]

[0163] In the formula, This indicates the object distance from the reticle to the lens being measured (a fixed value determined by the optical path design). Indicates the image distance (the fixed distance from the liquid lens to the CMOS sensor). This indicates the total focal power of the lens under test and the liquid lens.

[0164] Dual-lens combination: The lens under test inserted into the optical path (focal power) ) and liquid lenses used for compensating for focusing (focus) These are considered as two independent thin lenses, with their optical centers separated by a fixed distance determined by the mechanical structure. .

[0165] Clear imaging conditions: When the system is in sharp focus, the total equivalent focal length of the tested lens and the liquid lens combination is [value missing]. The focal length compensation must precisely compensate for the defocusing caused by inserting the lens under test, restoring the entire system to a fixed object-image conjugate state. The focal length compensation required for this fixed object-image relationship is defined as the geometric constant of the system. .

[0166] According to the thin lens combination formula, the total combined focal length is... The relationship between the focal power and spacing of a single lens is as follows:

[0167]

[0168] The conditions for a clear image are:

[0169]

[0170] Combining equations (1) and (2), we obtain the core equation upon which the system measurement is based:

[0171]

[0172] In the formula, The desired focal length of the lens being tested is... This refers to the real-time focal length of the liquid lens at the point of sharp imaging. and These are constants determined through system calibration.

[0173] [Electro-optical properties model of liquid lens]

[0174] Focal value of liquid lens Its drive control signal (such as the corresponding digital voltage value) Within the effective range, the relationship is linear:

[0175]

[0176] In the formula, For proportional parameters, is a constant term, representing parameters obtained through calibration. This model implicitly includes the optical power of the rear fixed lens group.

[0177] In practical applications, the driving value needs to be... Temperature compensation can be performed; compensation can be performed at any time. value or The values ​​are used for calculation. The complete characteristic model can be represented as:

[0178] in, Representing temperature, function The specific form is determined by the calibration.

[0179] [Focus Calculation Link]

[0180] For an unknown lens, its power Calculated via the following link:

[0181] Focusing and Measurement: Adjust the liquid lens voltage and find the drive value that makes the target image sharpest using the sharpness evaluation function. (Corresponding to liquid lens focal length) ).

[0182] Parameter acquisition: Read the system constants from the calibration parameters. and .

[0183] Solving the formula, , , Substituting into the calculation formula derived from the core equation (Equation 3), the focal length of the measured lens can be directly solved:

[0184] Based on the fundamental principles of the imaging system involved in this application as described above, the method for constructing the focal length mapping model includes:

[0185] (1) Install standard lenses of various focal lengths into the imaging system; control the imaging system containing the standard lenses based on a pre-constructed voltage sequence to perform image acquisition and obtain target image sequence samples;

[0186] Specifically, select a set of standard lenses covering the target range (e.g., {-20, -15, -10, -5, 0, +5, +10, +15, +20}D), and record the nominal values, batch numbers, and manufacturing tolerances (if any). Construct an imaging system based on the standard lenses with the above specifications, and then perform the initialization process as follows:

[0187] Environmental preheating and stabilization: After powering on the light source, liquid lens and processor, wait for the temperature to stabilize (rate of change <0.2°C / min) and record the reference temperature T0.

[0188] Lens surface cleanliness confirmation: Use an air blower or cleaning pad to remove dust and fingerprints to avoid scattering that could affect the F curve.

[0189] After initialization, image acquisition is performed directly as described above to obtain target image sequence samples.

[0190] (2) Extract the optimal voltage value sample corresponding to the maximum clarity from the target image sequence sample, and construct a data sample based on the optimal voltage value sample, temperature value and timestamp;

[0191] Perform the complete measurement procedure (refer to the previous text; the voltage value of the sample with the highest sharpness is the optimal voltage value sample) n times (n≥3) on the first standard lens to obtain its Vbest sample set. Let it be ( , (timestamp).

[0192] (3) Construct a sample set based on the data samples of multiple standard lenses, and perform outlier removal and data completion on the sample set to obtain a standard sample set;

[0193] Specifically, use or the IQR method to remove the outlier Vbest points. If the remaining valid samples after removal < n_min trigger retesting.

[0194] At the same time, calculate the representative value (average value) and standard deviation of Vbest for this lens. If the standard deviation is greater than the threshold (for example, 0.15V corresponds to > 0.01D), then retest after checking the placement / light source / algorithm noise.

[0195] Finally, obtain the data set D by traversing all standard lenses.

[0196] (4) Perform least squares fitting on the parameter model of the imaging system based on the standard sample set to obtain fitting parameters. Among them, the mathematical expression of the parameter model is:

[0197]

[0198]

[0199] In the formula, represents the diopter of the standard lens, and both represent system constants, represents the voltage;

[0200] The loss function located during the least squares fitting process is: <00​​​​​​​​​​​​​​​​​​​​​​

[0206] After the fitting is completed, the obtained fitting parameters are combined with the linear relationship. This allows for a preliminary characterization of the mapping relationship between the control voltage and the focal length of the liquid lens. Furthermore, to more accurately map this relationship, temperature compensation is introduced in this application, as detailed below.

[0207] (5) Calculate the theoretical driving voltage value The difference between the actual voltage value and the actual voltage value is used to obtain a voltage difference sample. It calculates the difference between the actual temperature value and the reference temperature value to obtain a temperature difference sample. ;

[0208] (6) Construct a linear fitting model for voltage difference and temperature difference, wherein the mathematical expression of the linear fitting model is:

[0209]

[0210] (7) Based on the voltage difference sample and the temperature difference sample The linear fitting model is fitted to obtain the temperature compensation coefficient. ;

[0211] The principle of the temperature coefficient fitting process in steps (5)-(7) is as follows:

[0212] The above process determines the temperature compensation coefficient by comparing theoretical references with measured data:

[0213] First, based on the calibrated physical model, the theoretical driving voltage that a standard lens with a known focal length should have at the reference temperature is calculated.

[0214] Then, the deviation between the actual measured voltage and the theoretical voltage is compared, and this deviation is correlated with the corresponding temperature change;

[0215] Finally, the influence coefficient of temperature change on driving voltage was obtained through linear regression analysis. This allows for the unified conversion of measured values ​​at different temperatures to equivalent values ​​at the reference temperature, ensuring the system's measurement accuracy and stability across the entire temperature range.

[0216] (8) Based on the parameter model, fitting parameters and temperature compensation coefficient of the imaging system Construct a focal length mapping model.

[0217] In addition, after building the model, post-processing is required, including:

[0218] Cross-validation: Use either one-lens-left-lens or K-fold validation (K = number of lenses) to calculate the average error, maximum error, and RMSE; determine whether the accuracy index is met.

[0219] Extended data supplement (optional): If the error in a certain local interval still exceeds the standard, introduce intermediate focal length lenses (e.g., ±7D, +12D) to supplement the data and repeat.

[0220] Model encapsulation and versioning: forming CalVer = timestamp + hash {k,b,d,K_sys, temperature coefficient k_T, segment node (if any)}.

[0221] Write to device and verify: Write CalVer and parameters to non-volatile storage, and read back to verify hash consistency; old version archives can be rolled back.

[0222] Calibration report generation: Outputs residual curves, fitted curves, temperature fitted distribution, hysteresis difference curves, outlier list and statistical indicators, providing a basis for quality traceability and subsequent recalibration.

[0223] The above model can calculate the voltage value based on the current temperature and the target focal length, and adjust the liquid lens based on the voltage value, thereby making the control process of this application more precise.

[0224] The beneficial effects of this application are as follows:

[0225] (1) High precision: Polar coordinate analysis and high precision sine fitting algorithm make the axis measurement accuracy reach ±0.5° and the astigmatism accuracy ±0.03D.

[0226] (2) High speed: No mechanical movement is required. A single electronic scan can complete the acquisition of data at all angles within milliseconds, and the measurement speed is significantly better than that of rotary equipment.

[0227] (3) High reliability: Fully electronic operation, no wear, long life, and strong resistance to vibration and interference.

[0228] (4) Embedded integration: The algorithm can run efficiently on embedded platforms such as Raspberry Pi, making it easy to miniaturize and reduce the cost of the device.

[0229] This application also provides a lens astigmatism measurement device based on a liquid lens and an umbrella-shaped target, comprising:

[0230] A focal length determination module is used to control a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extract the sharpness of multiple umbrella-shaped target images from the image sequence, and take the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length. The imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order.

[0231] The focal length determination module is used to control the imaging system to acquire a target focal length image of the umbrella-shaped target based on the target focal length, perform polar coordinate transformation on the target focal length image to obtain a polar coordinate image containing stripes representing multiple angles, and perform sharpness analysis on the multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the maximum sharpness.

[0232] The astigmatism determination module is used to control the imaging system to acquire multiple frames of scanned images based on the target focal length, locate the target stripes in the multiple frames of scanned images based on the target angle, determine the vertical optimal focal length based on the sharpness of the target stripes in the multiple frames of scanned images, and calculate the lens astigmatism of the lens under test based on the target focal length and the vertical optimal focal length.

[0233] This application discloses a method and apparatus for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target. The process consists of three stages: First, a focal length scan is performed using an electrically controlled liquid lens to determine the target focal length by utilizing image sharpness. Then, at the target focal length, an image of the umbrella-shaped target is acquired. Polar coordinate transformation is used to convert the rays of the umbrella-shaped target image into horizontal stripes. Sharpness is extracted from each horizontal stripe to find the target angle with the highest sharpness. Finally, a focal length range is constructed based on the target focal length, and scanning and polar coordinate transformation are performed within this range to extract the vertically optimal focal length. The lens astigmatism is then calculated using the target focal length and the vertically optimal focal length. This application decomposes complex astigmatism into two independent optimization problems in orthogonal directions, avoiding measurement instability caused by multi-parameter coupling in traditional methods. Furthermore, this application uses an electrically controlled hydraulic lens to adjust the optical path, eliminating complex mechanical and optical path structures and eliminating the need for subjective human judgment. It offers advantages such as high measurement efficiency, high measurement accuracy, and low cost.

[0234] This embodiment also provides an electronic terminal, including: a processor and a memory;

[0235] The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory so that the terminal performs any of the methods in this embodiment.

[0236] As will be understood by those skilled in the art, the computer-readable storage medium described in this embodiment allows for the implementation of all or part of the steps in the above method embodiments by computer program-related hardware. The aforementioned computer program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0237] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver, and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication between them. The memory is used to store computer programs, the communication interface is used to perform communication, and the processor and the transceiver are used to run the computer programs, so that the electronic terminal performs the steps of the above method.

[0238] In this embodiment, the memory may include random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device.

[0239] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0240] In the above embodiments, although the present application has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art based on the foregoing description. The embodiments of the present application are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims.

[0241] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target, characterized in that, The steps include: controlling a pre-constructed imaging system to acquire an image sequence of an umbrella-shaped target using a pre-constructed focal length scanning sequence, extracting the sharpness of multiple umbrella-shaped target images from the image sequence, and taking the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length. The imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order. The imaging system is controlled to acquire a target focal length image of the umbrella-shaped target using the target focal length. The target focal length image is then transformed into polar coordinates to obtain a polar coordinate image containing stripes representing multiple angles. Sharpness analysis is performed on the multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the highest sharpness. Based on the target focal length, the imaging system is controlled to acquire multiple frames of scanning images. The target stripes in the multiple frames of scanning images are located based on the target angle, and the vertical optimal focal length is determined based on the sharpness of the target stripes in the multiple frames of scanning images. Finally, the lens astigmatism of the lens under test is calculated based on the target focal length and the vertical optimal focal length. This includes: constructing a target focal length... The focal range of the center ,in, Represents units of focal length; within the focal length range The focal length of the liquid lens is scanned and adjusted using a target step size to obtain multiple scanned images corresponding to multiple scanned adjustment points, wherein the multiple scanned adjustment points are extracted from the focal length range; the scanned images are then subjected to polar coordinate transformation to obtain scanned polar coordinate images; based on the target angle... Extracting vertical angle The target stripe corresponding to the vertical angle is extracted from the scanned polar coordinate image, and the sharpness of the target stripe is calculated, wherein the sharpness is the average gradient of multiple pixels of the target stripe, and the vertical angle is... The mathematical expression is: The focal length of the scanned image containing the target stripe with the highest clarity is taken as the optimal vertical focal length. Based on the aforementioned vertical optimal focal length and the target focal length Calculate the lens astigmatism of the lens under test. ， 。 2. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 1, characterized in that, Controlling a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extracting the sharpness of multiple umbrella-shaped target images from the image sequence, and taking the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length, includes: extracting multiple focal length points from a pre-built full focal length range with a target step size, and controlling a liquid lens based on the multiple focal length points to obtain an image sequence of umbrella-shaped targets corresponding to the multiple focal length points; extracting the region of interest at the center position of each frame of the umbrella-shaped target image in the image sequence, calculating the gray-level variance of the region of interest, and measuring the sharpness of the umbrella-shaped target image based on the gray-level variance; taking the umbrella-shaped target image with the largest gray-level variance as the umbrella-shaped target image with the highest sharpness, and taking the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length.

3. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 1, characterized in that, Performing polar coordinate transformation on the target focal length image to obtain a polar coordinate image containing stripes representing multiple angles includes: using the center point coordinates of the target focal length image as the origin of the polar coordinates. Based on the origin of the polar coordinates The target focal length image is transformed into a polar coordinate system to obtain a polar coordinate image containing stripes representing multiple angles. The polar coordinate image The mathematical expression is: In the formula, Indicates the polar angle. Indicates the polar radius. Represents the pixel coordinates of the target focal length image.

4. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 3, characterized in that, Analyzing the sharpness of multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the highest sharpness includes: extracting stripes corresponding to multiple angles from the polar coordinate image; extracting column vectors of multiple pixels from the stripes corresponding to each angle; and calculating the gradient sharpness of each column vector. , wherein the gradient sharpness The mathematical expression is: In the formula, This represents the function for finding the average. express Gradient; Gradient sharpness based on multiple angles Constructing a resolution map ,in, Indicates angle; from the aforementioned sharpness map Extracting gradient sharpness The target angle corresponding to the largest stripe.

5. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 1, characterized in that, Controlling a pre-built imaging system to acquire image sequences of an umbrella-shaped target using a pre-built focal length scanning sequence includes: obtaining the temperature value at the current time point and extracting the target focal length value from the focal length scanning sequence; extracting fitting parameters and temperature compensation coefficients from a pre-built focal length mapping model; and calculating an initial control voltage based on the fitting parameters and the target focal length value. The initial control voltage The mathematical expression is: In the formula, Indicates the focal length of the liquid lens. Represents the proportional fitting parameters. The deviation term fitting parameters are represented by the temperature compensation coefficient. The temperature value at the current time point and reference temperature value For the initial control voltage Compensation is performed to obtain the compensation voltage. The mathematical expression for the compensation voltage is: Based on the compensation voltage, a pre-built imaging system is used to acquire image sequences of an umbrella-shaped target using a pre-built focal length scanning sequence.

6. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 5, characterized in that, The method for constructing the focal length mapping model includes: installing standard lenses of various focal lengths into the imaging system; controlling the imaging system containing the standard lenses to perform image acquisition based on a pre-constructed voltage sequence to obtain target image sequence samples; extracting the optimal voltage value sample corresponding to the maximum sharpness from the target image sequence samples, and constructing data samples based on the optimal voltage value sample, temperature value, and timestamp; constructing a sample set based on the data samples of multiple standard lenses, and performing outlier removal and data completion on the sample set to obtain a standard sample set; and performing least squares fitting on the parameter model of the imaging system based on the standard sample set to obtain fitting parameters, wherein the mathematical expression of the parameter model is: In the formula, Indicates the power of a standard lens. and All represent system constants. Represents voltage; calculates the theoretical driving voltage value. The difference between the actual voltage value and the actual voltage value is used to obtain a voltage difference sample. It calculates the difference between the actual temperature value and the reference temperature value to obtain a temperature difference sample. A linear fitting model of voltage difference and temperature difference is constructed, wherein the mathematical expression of the linear fitting model is: Based on the voltage difference sample and the temperature difference sample The linear fitting model is fitted to obtain the temperature compensation coefficient. Based on the parameter model, fitting parameters, and temperature compensation coefficient of the imaging system Construct a focal length mapping model.

7. The method for measuring lens astigmatism based on a liquid lens and an umbrella-shaped target according to claim 1, characterized in that, The imaging system includes a light source, a light homogenizing device, an umbrella-shaped target, a small aperture aperture, a lens under test, a liquid lens, an imaging lens, a junction box, and an image sensor arranged sequentially along the optical path.

8. A lens astigmatism measurement device based on a liquid lens and an umbrella-shaped target, characterized in that, include: A focal length determination module is used to control a pre-built imaging system to acquire an image sequence of an umbrella-shaped target using a pre-built focal length scanning sequence, extract the sharpness of multiple umbrella-shaped target images from the image sequence, and select the focal length corresponding to the umbrella-shaped target image with the highest sharpness as the target focal length. The imaging system includes a coaxial liquid lens and a lens under test, and the focal length scanning sequence includes multiple focal length values ​​arranged in a preset order. The focal length determination module is used to control the imaging system to acquire a target focal length image of the umbrella-shaped target using the target focal length, and to perform extreme polarization on the target focal length image. Coordinate transformation is performed to obtain a polar coordinate image containing stripes representing multiple angles; and sharpness analysis is performed on the multiple stripes in the polar coordinate image to obtain the target angle corresponding to the stripe with the highest sharpness; an astigmatism determination module is used to control the imaging system to acquire multiple frames of scanning images based on the target focal length, locate the target stripes in the multiple frames of scanning images based on the target angle, determine the vertical optimal focal length based on the sharpness of the target stripes in the multiple frames of scanning images, and calculate the lens astigmatism of the lens under test based on the target focal length and the vertical optimal focal length, including: constructing a system based on the target focal length. The focal range of the center ,in, Represents units of focal length; within the focal length range The focal length of the liquid lens is scanned and adjusted using a target step size to obtain multiple scanned images corresponding to multiple scanned adjustment points, wherein the multiple scanned adjustment points are extracted from the focal length range; the scanned images are then subjected to polar coordinate transformation to obtain scanned polar coordinate images; based on the target angle... Extracting vertical angle The target stripe corresponding to the vertical angle is extracted from the scanned polar coordinate image, and the sharpness of the target stripe is calculated, wherein the sharpness is the average gradient of multiple pixels of the target stripe, and the vertical angle is... The mathematical expression is: The focal length of the scanned image containing the target stripe with the highest clarity is taken as the optimal vertical focal length. Based on the aforementioned vertical optimal focal length and the target focal length Calculate the lens astigmatism of the lens under test. ， 。

Images