Liquid lens wavefront detection device and method based on background schlieren method

Abstract

The present invention discloses a liquid lens wavefront detection device and method based on a background schlieren method. The detection device includes a first reference wavefront beam generating component, a bilateral telecentric lens, and a camera. The reference wavefront beam emitted from the first reference wavefront beam generating component is incident on the liquid lens to be tested, is incident on the bilateral telecentric lens after being transmitted by the liquid lens to be tested, and is then collected by the camera after being transmitted by the bilateral telecentric lens. The present invention uses the detection device to collect reference images and dynamic images of the liquid lens to be tested, thereby obtaining background displacement, and then obtaining a wavefront slope distribution. Finally, after integral reconstruction of the wavefront slope distribution, the wavefront distribution and wave aberration of the liquid lens to be tested are obtained. The present invention uses the telecentric background schlieren method to perform liquid lens wave aberration detection, which overcomes the problem that the traditional Shack-Hartmann wavefront detection technology requires the use of a microlens array to divide the wavefront to be tested into several sub-waves, and the spatial resolution is limited by the size and duty cycle of the microlens.

Description

Technical Field

[0001] The present invention relates to a lens wavefront detection device and method in the field of optical measurement, and in particular to a liquid lens wavefront detection device and method based on a background schlieren method. Background Art

[0002] Liquid lenses are optical components composed of liquids without solid mechanical structures. They are widely used in imaging systems such as immersion lithography, microscopy, and machine vision. Because the refractive index distribution of the fluid within a liquid lens is affected by various factors such as density, temperature, pressure, and flow, it can easily cause dynamic changes in the wavefront, thereby degrading the imaging quality of the optical system. Therefore, accurate and real-time detection of wavefront aberrations in liquid lenses is crucial to ensuring their performance under various operating conditions.

[0003] Existing wavefront measurement technologies include traditional interferometry, the Hartmann method, shearing interferometry, and point diffraction. While these methods have achieved promising results in objective lens wavefront aberration detection, they still face challenges. Interferometry typically requires a reference optical path and is suitable for offline detection. The Hartmann and shearing interferometry methods can be used for online detection, but they only measure the wavefront slope and require complex calculations to reconstruct the wavefront. The point diffraction method also suffers from reduced light throughput and decreased accuracy. For high-resolution lithography or microscopy systems, the current mainstream detection method is phase measuring interferometer (PMI), such as Nikon's P-PMI technology based on the Shack-Hartmann sensor, Canon's in-situ wavefront aberration detection interferometer based on the linear diffraction principle, and ASML's ILIAS lateral shearing interferometry technology based on the shearing interferometry principle. However, as the final objective lens, the liquid lens directly contacts the photoresist and cannot compensate for wavefront aberration like a solid lens. Therefore, a method for detecting wavefront aberration in liquid lenses is needed.

[0004] The Background Oriented Schlieren Technique (BOS) is a relatively new flow measurement technology, first proposed by Meier et al. around 2000. BOS overcomes the difficulties inherent in illumination variations caused by self-luminescence in traditional Schlieren techniques. By utilizing PIV or optical flow algorithms, BOS eliminates the complex and expensive experimental setup required by traditional Schlieren techniques. BOS was first applied to quantitatively measure density fields in aerodynamic optics and has subsequently expanded to fluid temperature measurement, free-surface measurement, and aerodynamic wavefront measurement. BOS possesses a simple setup, and its measurement sensitivity and accuracy are primarily determined by optical path design, camera resolution, background pattern design, and background displacement algorithms.

[0005] Existing methods for detecting wavefront aberrations in optical systems include lateral shearing interferometry (CN102368139A, CN104111161A) and the Shack-Hartmann technique (US9574967B2, US7391497B2). Unlike solid lens systems, the refractive index distribution of liquid lenses exhibits temporal and spatial inhomogeneity. Therefore, it is necessary to develop a wavefront detection device and method for liquid lenses. Summary of the Invention

[0006] In order to overcome the deficiencies in the background technology, the present invention provides a liquid lens wavefront detection device and method based on a background schlieren method.

[0007] The first objective of the present invention is to provide a liquid lens wavefront detection device based on the background schlieren method. This device can measure the refractive index inhomogeneity caused by temperature in incompressible flow fields. It also reduces system complexity, eliminating the need for traditional interferometry methods or microlens arrays, and avoiding the use of multiple gratings or the systematic errors introduced by microlens arrays. The use of bilateral telecentric background schlieren overcomes the conflict between spatial resolution and sensitivity in traditional BOS systems, while the use of a high-speed camera as an image receiver ensures temporal resolution.

[0008] A second objective of the present invention is to provide a liquid lens wavefront detection method based on the background schlieren method. This method can obtain the wavefront slope from the measured background displacement, and then reconstruct the wavefront distribution of the dynamic flow field, thereby achieving real-time wavefront detection.

[0009] The technical solutions adopted in the present invention are as follows:

[0010] 1. A liquid lens wavefront detection device based on background schlieren method

[0011] The liquid lens wavefront detection device includes a first reference wavefront beam generating component, a bilateral telecentric lens and a camera. The first reference wavefront beam generating component, the bilateral telecentric lens and the camera are arranged in sequence along the optical axis. The liquid lens to be tested is placed between the first reference wavefront beam generating component and the bilateral telecentric lens. The reference wavefront beam emitted from the first reference wavefront beam generating component is incident on the liquid lens to be tested, is transmitted by the liquid lens to be tested, is incident on the bilateral telecentric lens, and is then collected by the camera after being transmitted by the bilateral telecentric lens.

[0012] The liquid lens to be tested includes a fluid, a transparent glass cover plate and a lens shell. A through groove arranged along the optical axis is opened in the lens shell, and corresponding transparent glass cover plates are respectively installed in the lens shell at both ends of the through groove, so that the lens shell has a sealed structure; a fluid cavity is formed in the lens shell between the two transparent glass cover plates, and a water inlet and a drain port are also opened in the lens shell. The water inlet and the drain port are connected to the fluid cavity, and the fluid cavity is filled with fluid.

[0013] The device also includes a disturbance correction component, which includes a second reference wavefront beam generating component, a disturbance correction liquid lens, a reflector and a spectroscopic prism; the wavelength of the reference wavefront beam emitted from the second reference wavefront beam generating component is different from the wavelength of the reference wavefront beam emitted from the first reference wavefront beam generating component; the second reference wavefront beam generating component is arranged on the side of the first reference wavefront beam generating component, and the reference wavefront beam emitted from the second reference wavefront beam generating component is incident on the disturbance correction liquid lens, the structure and fluid type of the disturbance correction liquid lens are the same as those of the liquid lens to be measured, and the fluid in the disturbance correction liquid lens is the same as that of the liquid lens to be measured. The body is in a stationary state, and the light beam emitted after being transmitted by the disturbance correction liquid lens is incident on the reflector. The dichroic prism is arranged between the liquid lens to be measured and the double-sided telecentric lens. The light beam transmitted by the liquid lens to be measured is incident on the dichroic prism for transmission, and the light beam reflected by the reflector is incident on the dichroic prism for emission. The light beams transmitted and reflected by the dichroic prism are both incident on the double-sided telecentric lens. A first optical path is formed between the first reference wavefront beam generating component, the liquid lens to be measured and the dichroic prism, and a second optical path is formed between the second reference wavefront beam generating component, the disturbance correction liquid lens, the reflector and the dichroic prism. The optical path of the first optical path and the second optical path is the same.

[0014] The first reference wavefront beam generating component includes a background pattern plate and an LED lighting system. The background pattern plate is a transparent screen with random dot matrix scattered on it; the LED lighting system is used to generate a parallel light beam.

[0015] The double-sided telecentric lens includes a first positive lens and a second positive lens arranged in sequence along the optical axis. The aperture is located between the first positive lens and the second positive lens. The aperture is located at the focus of the first positive lens and the focus of the second positive lens.

[0016] 2. A Liquid Lens Wavefront Detection Method Based on Background Schlieren Method

[0017] Step 1: Install the liquid lens to be tested in the liquid lens wavefront detection device;

[0018] Step 2: Use the camera to sequentially capture the reference image I of the liquid lens to be tested in an undisturbed state ref And the dynamic image of disturbance under the action of temperature gradient I disturbed ;

[0019] Step 3: Obtain reference image I ref With dynamic image I disturbed After processing, the background displacement (△x',△y') is obtained;

[0020] Step 4: Based on the background displacement (△x', △y'), the background displacement (△x', △y'), the light deflection angle (ε x ,ε y ) and the wavefront slope, thereby calculating the wavefront slope distribution;

[0021] Step 5: After integral reconstruction of the wavefront slope distribution, the wavefront distribution and wave aberration of the liquid lens to be tested are obtained.

[0022] In step 3, the reference image I is obtained by using a cross-correlation or optical flow algorithm. ref With dynamic image I disturbed to be processed.

[0023] In step 5, a trapezoidal integration algorithm or an iterative reconstruction algorithm is used to perform integral reconstruction on the wavefront slope distribution.

[0024] 3. A liquid lens wavefront detection method based on background schlieren method

[0025] Step 1: Install the liquid lens to be tested in the liquid lens wavefront detection device;

[0026] Step 2: The camera records the reference image I of the liquid lens to be tested in the undisturbed state in sequence in dual-frame mode ref and the first calibration reference image of the disturbance correction liquid lens; then, the camera sequentially records the dynamic image I of the disturbance generated by the liquid lens to be tested under the action of the temperature gradient in the dual-frame mode disturbed and a second corrected reference image of the perturbation-corrected liquid lens;

[0027] Step 3: Obtain reference image I ref With dynamic image I disturbed After processing, the original background displacement (△x', △y') is obtained; and after processing the first corrected reference image and the second corrected reference image, the perturbation displacement is obtained; after subtracting the original background displacement (△x', △y') from the perturbation displacement, the corrected background displacement is obtained;

[0028] Step 4: Based on the corrected background displacement, use the Fermat principle and Malus law in geometric optics to establish the background displacement (△x',△y'), the light deflection angle (ε x ,ε y ) and the wavefront slope, thereby calculating the wavefront slope distribution;

[0029] Step 5: After integral reconstruction of the wavefront slope distribution, the wavefront distribution and wave aberration of the liquid lens to be tested are obtained.

[0030] The present invention applies the background schlieren method to quantitatively measure the wavefront gradient of an incompressible liquid lens, and then reconstruct the wave aberration. It is particularly suitable for real-time quantitative measurement of dynamic changes in wave aberration caused by factors such as temperature and density inside the liquid lens.

[0031] The beneficial effects of the present invention are:

[0032] The present invention provides a liquid lens wavefront detection device based on the background schlieren method. By replacing the microlens array measurement method with the background schlieren method, the device can obtain the wavefront slope of parallel light waves after passing through the liquid lens under test, and then reconstruct the entire wavefront distribution. This overcomes the shortcomings of the microlens array itself, such as insufficient spatial resolution and high duty cycle.

[0033] The present invention uses a background schlieren method to reduce system complexity and alleviate the disadvantage of introducing more system errors by using multiple gratings or microlens arrays.

[0034] The device and method proposed in the present invention can not only measure the wavefront aberration of the liquid lens, but also simultaneously obtain flow information of the flow field inside the liquid lens, thereby enhancing the understanding and control of the optical quality of the liquid lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the liquid lens wavefront detection device in the present invention.

[0036] Figure 2 Schematic diagram of the structure of the liquid lens in the present invention, wherein (a) is a side sectional view of the liquid lens, and (b) is an end sectional view of the liquid lens.

[0037] Figure 3 Schematic diagram of the displacement of the background Schlieren pattern in the present invention.

[0038] Figure 4 Schematic diagram of the structure of the liquid lens wavefront detection device in Example 1.

[0039] Figure 5 Schematic diagram of the structure of the liquid lens wavefront detection device in Example 2.

[0040] Figure 6 This is a flow chart of the liquid lens wavefront detection method in Example 1.

[0041] In the figure, 1: background pattern plate; 2: liquid lens; 21: fluid; 22: transparent glass cover; 23: lens shell; 3: bilateral telecentric lens; 31: first positive lens; 32: aperture; 33: second positive lens; 4: LED lighting system; 41: blue light LED with a wavelength of 450nm; 42: red light LED with a wavelength of 660nm; 5: camera; 6: data processor; 7: reflector; 8: spectrometer. DETAILED DESCRIPTION

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Example 1

[0044] like Figure 1 and Figure 4 As shown, the liquid lens wavefront detection device includes a first reference wavefront beam generating assembly, a bilateral telecentric lens 3, and a high-speed camera 5. The first reference wavefront beam generating assembly, the bilateral telecentric lens 3, and the high-speed camera 5 are sequentially spaced along the optical axis. The liquid lens 2 to be tested is placed between the first reference wavefront beam generating assembly and the bilateral telecentric lens 3. The reference wavefront beam emitted from the first reference wavefront beam generating assembly is incident on the liquid lens 2 to be tested, is transmitted through the liquid lens 2 to be tested, is incident on the bilateral telecentric lens 3, and is then transmitted through the bilateral telecentric lens 3 before being captured by the high-speed camera 5. The high-speed camera 5 is connected to a data processor 6. The bilateral telecentric lens 3 and the camera 5 are arranged on the same optical axis, and the beam incident on the bilateral telecentric lens 3 may be at an angle to the optical axis.

[0045] The bilateral telecentric lens 3 includes a first positive lens 31 and a second positive lens 33 spaced apart along the optical axis. A stop 32 is located between the first and second positive lenses 31, 33. The stop 32 is located at the focal points of the first and second positive lenses 31, 33. The first and second positive lenses 31, 33 are thin positive lenses with focal lengths f1 and f2, respectively.

[0046] like Figure 4 As shown, the liquid lens wavefront detection device is set vertically, and the liquid lens to be tested 2 is set horizontally. The reference wavefront beam generating assembly is arranged on the same optical axis as the double-sided telecentric lens 3 and the high-speed camera 5. The light emitted by the illumination system is incident approximately parallel to the background pattern plate 1. The double-sided telecentric lens 3 and the high-speed camera 5 ensure that the background image is incident approximately parallel to the imaging plane. The magnification of the assembly composed of the double-sided telecentric lens 3 and the high-speed camera 5 is related to the focal length of the two thin lenses in the double-sided telecentric lens, and is independent of the relative distance between the schlieren object and the background and the camera.

[0047] Figure 1 where Z_D represents the distance between the flow field to be measured and the background pattern plate; Z_A represents the distance between the flow field to be measured and the first positive lens; Z_i represents the distance between the second positive lens and the camera imaging plane; Δy' represents the displacement of the background pattern at the background pattern plate in the y direction due to light deflection; Δy represents the displacement of the pattern at the background pattern plate in the y direction corresponding to the displacement on the camera imaging plane.

[0048] like Figure 2 (a) and Figure 2As shown in (b), the liquid lens 2 to be tested comprises a fluid 21, a transparent glass cover plate 22, and a lens housing 23. The lens housing 23 is made of opaque material and has a through slot arranged along the optical axis. Corresponding transparent glass cover plates 22 are installed in the lens housing 23 at both ends of the through slot, making the lens housing 23 a sealed structure. A fluid cavity is formed in the lens housing 23 between the two transparent glass cover plates 22. The lens housing 23 also has a water inlet and a water outlet, which are connected to the fluid cavity. The fluid 21 is continuously refreshed through the water inlet and outlet, and a flow field with a temperature gradient can be formed through the two water inlets. The fluid is ultrapure water.

[0049] The first reference wavefront beam generating assembly includes a background pattern plate 1 and an LED lighting system 4. The background pattern plate 1 is a transparent screen with random dot arrays, such as Figure 3 As shown in the figure, its dot matrix features generate displacement information that can be used to reconstruct the wavefront after passing through the liquid lens. The image size of the background pattern speckle on the photosensitive element of camera 5 should be 3-5 pixels. The speckle spacing should be larger than the speckle diameter to avoid aliasing, and the grayscale gradient of the speckle edge should be clear. After passing through liquid lens 2, background pattern 1 is distorted and displaced (△x', △y'). All background displacement vectors constitute the displacement vector field.

[0050] The LED lighting system 4 is used to generate a parallel light beam and includes a light source and a collimator. A light beam of a specific wavelength emitted from the light source is converted into a plane wave by the collimator. After passing through the background pattern plate 1, a plane wave containing the background pattern image is obtained. Due to the uneven temporal and spatial distribution of the refractive index of the flow field within the liquid lens, the plane wave containing the background pattern image experiences wavefront distortion after passing through the liquid lens. This disturbed wavefront is then filtered by the bilateral telecentric lens 3, returning it to parallelism with the principal optical axis and converging onto the photosensitive element of the camera 5. The camera then captures the image, obtaining a continuous image that is then output to the data processor 6 for post-processing.

[0051] The data processor 6 is used to receive and store the background pattern output by the high-speed camera and perform post-processing calculations, including background displacement estimation, light deflection angle calculation, wavefront slope calculation, and wavefront reconstruction.

[0052] The detection method relies on the background displacement information collected by the liquid lens wavefront detection device based on the background schlieren method. According to Malus's law, after a light ray perpendicular to the wavefront undergoes any number of refractions or reflections, the exit wavefront of the light must be perpendicular to the exiting light ray, and the optical path lengths of all light rays between the corresponding points of the exit wavefront and the exit wavefront are equal. Figure 1 As shown, the angle between the disturbed wavefront and the y-axis is equal to the deflection angle ε of the light after passing through the liquid lens y, using trapezoidal integration algorithm or iterative algorithm to obtain liquid lens wavefront distribution information. The present invention proposes a liquid lens wavefront detection method based on background schlieren method, such as Figure 6 As shown, the detection method includes the following steps:

[0053] Step 1: Install the liquid lens 2 to be tested in the liquid lens wavefront detection device, that is, build the liquid lens wavefront detection device;

[0054] Step 2: Use the high-speed camera 5 to sequentially capture the reference image I of the liquid lens 2 under undisturbed conditions. ref (i.e. the fluid in the liquid lens 2 to be tested is in a static state, and the liquid lens 2 to be tested is a static flow field) and a dynamic image I of disturbance generated under the action of temperature gradient disturbed (That is, the fluid in the liquid lens 2 to be tested is in a flow state with a temperature gradient, and the liquid lens 2 to be tested is a flow field with a temperature gradient);

[0055] Step 3: Use the cross-correlation method to obtain the reference image I ref With dynamic image I disturbed After processing, the background displacement (△x',△y') is obtained. Specifically, the background displacement is obtained by selecting an appropriate window size and performing cross-correlation between the processed reference image and a series of dynamic images. Alternatively, an appropriate optical flow algorithm is used to perform displacement estimation to obtain the background displacement.

[0056] Step 4: Based on the background displacement (△x', △y'), the background displacement (△x', △y'), the light deflection angle (ε x ,ε y ) and the wavefront slope, thereby calculating the wavefront slope distribution; specifically, the relationship between background displacement and light deflection angle, as well as the relationship between light deflection angle and wavefront slope, are used to obtain the wavefront slope at each location of the liquid lens, thereby obtaining the wavefront slope distribution.

[0057] according to Figure 1 The geometric relationship and small angle assumption of the background displacement (△x',△y') and the light deflection angle (ε x ,ε y ) relationship:

[0058] ε x ≈tanε x =△x' / Z_D

[0059] ε y ≈tanε y =△y' / Z_D

[0060] and the light deflection angle (ε x ,εy ) and the wavefront slope:

[0061]

[0062] Among them, △x' is the displacement of the background pattern in the x direction, △y' is the displacement of the background pattern in the y direction, ε x is the deflection angle of the light in the x direction, ε y is the deflection angle of the light in the y direction, OPL(x,y) refers to the optical path, OPL=∫ s nds, n is the refractive index, and s is the distance along the optical path. So the optical path difference OPD can be defined as:

[0063] OPD=OPL-OPL'

[0064] Where OPL represents the optical path length and OPL' refers to the average optical path length, so the phase distortion △Φ of the light wave is:

[0065] △Φ=2π·OPD / λ

[0066] Here, λ represents the wavelength of light.

[0067] Step 5: After integrating and reconstructing the wavefront slope distribution using the trapezoidal integration algorithm, the wavefront distribution and wave aberration of the liquid lens 2 to be tested are obtained. Specifically, according to the currently obtained light deflection angle (ε x ,ε y ), use the trapezoidal integration algorithm or iterative algorithm to reconstruct the two-dimensional wavefront, so as to obtain the wavefront distribution and wave aberration information of the liquid lens. The iterative algorithm can discretize the wavefront to be measured, perform finite difference fitting on the optical path OPL of each node, and then use singular value decomposition to solve the entire matrix. This method requires more computing power as the size of the matrix increases. Another iterative algorithm is the Southwell integration algorithm. The optical path OPL of each node is represented by the four nodes around it, and finally the four values obtained are weighted averaged to obtain the wavefront distribution of the current liquid lens.

[0068] Example 2

[0069] like Figure 5As shown, the liquid lens wavefront detection device includes a first reference wavefront beam generating assembly, a disturbance correction assembly, a bilateral telecentric lens 3, and a high-speed camera 5. The first reference wavefront beam generating assembly, the bilateral telecentric lens 3, and the high-speed camera 5 are sequentially spaced along the optical axis. The liquid lens 2 to be tested is placed between the first reference wavefront beam generating assembly and the bilateral telecentric lens 3. The reference wavefront beam emitted from the first reference wavefront beam generating assembly is incident on the liquid lens to be tested 2. After being transmitted by the liquid lens 2 to be tested, it is incident on the bilateral telecentric lens 3. After being transmitted by the bilateral telecentric lens 3, it is collected by the high-speed camera 5. The high-speed camera 5 is connected to a data processor 6. The bilateral telecentric lens 3 includes a first positive lens 31 and a second positive lens 33, which are sequentially spaced along the optical axis. The aperture 32 is located between the first positive lens 31 and the second positive lens 33. The aperture 32 is located at the focus of the first positive lens 31 and the focus of the second positive lens 33.

[0070] The disturbance correction component is used to correct the system error caused by the disturbance along the optical path, the cooling fan of the high-speed camera 5 and other factors in the system. The disturbance correction component includes a second reference wavefront beam generating component, a disturbance correction liquid lens, a reflector 7 and a beam splitter prism 8; the wavelength of the reference wavefront beam emitted from the second reference wavefront beam generating component is different from the wavelength of the reference wavefront beam emitted from the first reference wavefront beam generating component, and the other parts are the same; the second reference wavefront beam generating component is arranged on the side of the first reference wavefront beam generating component, and the reference wavefront beam emitted from the second reference wavefront beam generating component is incident on the disturbance correction liquid lens. The structure and fluid type of the disturbance correction liquid lens are the same as those of the liquid lens 2 to be tested, and the fluid in the disturbance correction liquid lens is in a static state (that is, not updated, the first reference wavefront beam generating component is not updated, and the second reference wavefront beam generating component is not updated). The reference light beam generated in the two optical paths remains distortion-free after passing through the liquid lens), the light beam emitted after being transmitted through the disturbance correction liquid lens is incident on the reflector 7, the dichroic prism 8 is arranged between the liquid lens to be measured 2 and the bilateral telecentric lens 3 and is coaxially arranged with the liquid lens to be measured 2 and the bilateral telecentric lens 3, the light beam transmitted through the liquid lens to be measured 2 is incident on the dichroic prism 8 for transmission, the light beam reflected through the reflector 7 is incident on the dichroic prism 8 for emission, and the light beams transmitted and reflected through the dichroic prism 8 are both incident on the bilateral telecentric lens 3; a first optical path is formed between the first reference wavefront beam generating component, the liquid lens to be measured 2 and the dichroic prism 8, a second optical path is formed between the second reference wavefront beam generating component, the disturbance correction liquid lens, the reflector 7 and the dichroic prism 8, and the optical path of the first optical path and the second optical path are the same. Therefore, the generated background displacement can be regarded as a systematic error composed of disturbances along the optical path, low-frequency disturbances introduced by the cooling fan of the high-speed camera 5, and other factors. The background displacements in the two optical paths are quickly recorded by the dual-frame mode of the high-speed camera 5, and the false displacement caused by the systematic error in the first optical path is removed, thereby improving the accuracy of liquid lens wavefront detection.

[0071] like Figure 2 (a) and Figure 2 As shown in (b), the liquid lens 2 to be tested comprises a fluid 21, a transparent glass cover plate 22, and a lens housing 23. The lens housing 23 is made of a light-transmitting material and has a through-slot along the optical axis. Corresponding transparent glass cover plates 22 are mounted in the lens housing 23 at either end of the through-slot, making the lens housing 23 a sealed structure. A fluid cavity is formed within the lens housing 23 between the two transparent glass cover plates 22. The lens housing 23 also has a water inlet and a water outlet, which communicate with the fluid cavity. The fluid cavity is filled with fluid, which can form a dynamic flow field with a temperature gradient. The fluid is ultrapure water.

[0072] The background pattern plate 1 in the first and second reference wavefront beam generating assemblies is identical, but the wavelengths of light emitted by the LED illumination system 4 are different. The light source for the first reference wavefront beam generating assembly is a blue LED 41 with a wavelength of 450nm; the light source for the second reference wavefront beam generating assembly is a red LED 42 with a wavelength of 660nm. To better reflect false displacement caused by system errors, the interval between capturing the background pattern along the two optical paths must be extremely short. Using the dual-frame mode of the high-speed camera 5, the first optical path is first exposed for approximately 20μs. After the first optical path, the second optical path is exposed approximately 10μs later, also for approximately 20μs.

[0073] The present invention proposes a liquid lens wavefront detection method based on background schlieren method, which includes the following steps:

[0074] Step 1: Install the liquid lens 2 to be tested in the liquid lens wavefront detection device;

[0075] Step 2: The high-speed camera 5 records the reference image I of the liquid lens 2 to be tested in the undisturbed state in sequence in the dual-frame mode. ref (i.e. the fluid in the liquid lens 2 to be tested is in a static state, and the liquid lens 2 to be tested is in a static flow field) and the first correction reference image of the disturbance correction liquid lens; then, the high-speed camera 5 sequentially records the dynamic image I of the disturbance generated by the liquid lens 2 to be tested under the action of the temperature gradient in a dual-frame mode. disturbed (i.e., the fluid in the liquid lens 2 to be tested is in a flow state with a temperature gradient, and the liquid lens 2 to be tested is a flow field with a temperature gradient) and a second correction reference image of the disturbance correction liquid lens;

[0076] Step 3: Use the optical flow algorithm to obtain the reference image I ref With dynamic image I disturbedAfter processing, the original background displacement (△x', △y') is obtained; and after processing the first corrected reference image and the second corrected reference image, the perturbation displacement is obtained; after subtracting the original background displacement (△x', △y') from the perturbation displacement, the corrected background displacement is obtained; in the cross-correlation or optical flow algorithm, by selecting an appropriate observation window size, the processed reference image is convolved with a series of dynamic images to obtain a continuous background displacement.

[0077] Step 4: Based on the corrected background displacement, use the Fermat principle and Malus law in geometric optics to establish the background displacement (△x',△y'), the light deflection angle (ε x ,ε y ) and the wavefront slope, thereby calculating the wavefront slope distribution;

[0078] Step 5: After integrally reconstructing the wavefront slope distribution using an iterative reconstruction algorithm, the wavefront distribution and wave aberration of the liquid lens 2 to be tested are obtained.

[0079] Example 2 shares some of the same optical system layout and apparatus as Example 1, differing in the wavelength of the illumination system. The wavelength of the illumination system in the first reference wavefront beam generating assembly is 450nm, while the wavelength of the illumination system in the second reference wavefront beam generating assembly is 660nm. To better reflect false displacements caused by system errors, the background pattern images along the two optical paths must be captured with an extremely short interval. High-speed camera 5 records in dual-frame mode, first exposing the first optical path for approximately 20μs. After the first optical path is completed, the second optical path is exposed approximately 10μs later, also for approximately 20μs. This is suitable for situations requiring high-precision measurements.

[0080] In Example 2, the background displacement (△1x', △1y') obtained by the first optical path is composed of the background displacement (△x' disturb ,△y' disturb ) and false displacement caused by system error (△x' system ,△y' system ) together. The background displacement (△2x',△2y') obtained by the second optical path only includes the false displacement (△x' system ,△y' system ).so

[0081] △x'=△1x'-△2x'=(△x' disturb +△x' system )-△x' system

[0082] △y'=△1y'-△2y'=(△y' disturb +△y' system)-△y' system

[0083] Because the exposure time interval between the two optical paths is extremely short, the false displacement caused by low-frequency disturbances such as high-speed camera fan vibration and ambient temperature fluctuation can be considered the same in the two optical paths. Therefore, Example II is suitable for situations requiring high-precision measurement.

[0084] In the description of the positional relationship of the present invention, the terms "inside", "outside", "up", "down", "left", "right" and the like indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "parallel", "vertical" and the like do not mean that the components are required to be absolutely parallel or vertical, but are allowed to be slightly tilted. At the same time, although the steps shown in the flowchart of the accompanying drawings show a logical order in the flowchart, in some cases, the steps shown or described can be performed in an order different from that here.

[0085] The above content and structure describe the basic principles, main features, and advantages of the product of the present invention, which should be understood by those skilled in the art. The above examples and description are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications are intended to be within the scope of the invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A liquid lens wavefront detection device based on background schlieren method, characterized in that: The liquid lens wavefront detection device comprises a first reference wavefront beam generating component, a bilateral telecentric lens (3) and a camera (5), wherein the first reference wavefront beam generating component, the bilateral telecentric lens (3) and the camera (5) are sequentially spaced along the optical axis, and the liquid lens to be tested (2) is placed between the first reference wavefront beam generating component and the bilateral telecentric lens (3). The reference wavefront beam emitted from the first reference wavefront beam generating component is incident on the liquid lens to be tested (2), is transmitted through the liquid lens to be tested (2), is incident on the bilateral telecentric lens (3), and is then transmitted through the bilateral telecentric lens (3) and collected by the camera (5). The liquid lens wavefront detection device further includes a disturbance correction component, which includes a second reference wavefront beam generating component, a disturbance correction liquid lens, a reflector (7), and a beam splitter prism (8); the wavelength of the reference wavefront beam emitted from the second reference wavefront beam generating component is different from the wavelength of the reference wavefront beam emitted from the first reference wavefront beam generating component; The second reference wavefront beam generating component is arranged on the side of the first reference wavefront beam generating component. The reference wavefront beam emitted from the second reference wavefront beam generating component is incident on the disturbance correction liquid lens. The structure and fluid type of the disturbance correction liquid lens are the same as those of the liquid lens to be tested (2). The fluid in the disturbance correction liquid lens is in a static state. The light beam emitted after being transmitted through the disturbance correction liquid lens is incident on the reflector (7). The beam splitter prism (8) is arranged between the liquid lens to be tested (2) and the double-sided telecentric lens (3). (2) The transmitted light beam is incident on the dichroic prism (8) and is transmitted, and the light beam reflected by the reflector (7) is incident on the dichroic prism (8) and is reflected, and the light beams transmitted and reflected by the dichroic prism (8) are both incident on the double-sided telecentric lens (3); a first light path is formed between the first reference wavefront light beam generating component, the liquid lens to be measured (2) and the dichroic prism (8), and a second light path is formed between the second reference wavefront light beam generating component, the disturbance correction liquid lens, the reflector (7) and the dichroic prism (8), and the optical path of the first light path and the second light path are the same.

2. The liquid lens wavefront detection device based on the background schlieren method according to claim 1, characterized in that: The liquid lens (2) to be tested comprises a fluid (21), a transparent glass cover plate (22) and a lens shell (23); a through groove arranged along the optical axis is provided in the lens shell (23); corresponding transparent glass cover plates (22) are respectively installed in the lens shell (23) at both ends of the through groove, so that the lens shell (23) has a sealed structure; a fluid cavity is formed in the lens shell (23) between the two transparent glass cover plates (22); a water inlet and a water outlet are further provided in the lens shell (23); the water inlet and the water outlet are communicated with the fluid cavity, and the fluid cavity is filled with fluid.

3. The liquid lens wavefront detection device based on the background schlieren method according to claim 1, characterized in that: The first reference wavefront beam generating component comprises a background pattern plate (1) and an LED lighting system (4), wherein the background pattern plate (1) is a transparent screen with random dot arrays scattered thereon; and the LED lighting system (4) is used to generate parallel light beams.

4. The liquid lens wavefront detection device based on the background schlieren method according to claim 1, characterized in that: The bilateral telecentric lens (3) comprises a first positive lens (31) and a second positive lens (33) which are sequentially arranged at intervals along the optical axis; the aperture (32) is located between the first positive lens (31) and the second positive lens (33); and the aperture (32) is located at the focal point of the first positive lens (31) and the focal point of the second positive lens (33).

5. A liquid lens wavefront detection method based on background schlieren method, characterized in that: The following steps are involved: Step 1: Install the liquid lens (2) to be tested in the liquid lens wavefront detection device according to claim 1; Step 2: The camera (5) records the reference image I of the liquid lens (2) to be tested in the undisturbed state in sequence in the dual-frame mode. ref and a first correction reference image of the disturbance correction liquid lens; then, the camera (5) sequentially records the dynamic image I of the disturbance generated by the liquid lens to be tested (2) under the action of the temperature gradient in a dual-frame mode. disturbed and a second corrected reference image of the perturbation-corrected liquid lens; Step 3: Obtain reference image I ref With dynamic image I disturbed After processing, the original background displacement (△x', △y') is obtained; and after processing the first corrected reference image and the second corrected reference image, the perturbation displacement is obtained; after subtracting the original background displacement (△x', △y') from the perturbation displacement, the corrected background displacement is obtained; Step 4: Based on the corrected background displacement, use the Fermat principle and Malus law in geometric optics to establish the background displacement (△x',△y'), the light deflection angle (ε x ,ε y ) and the wavefront slope, thereby calculating the wavefront slope distribution; Step 5: After integrally reconstructing the wavefront slope distribution, the wavefront distribution and wave aberration of the liquid lens (2) to be tested are obtained.

6. The liquid lens wavefront detection method based on background schlieren method according to claim 4, characterized in that: In step 3, the reference image I is obtained by using a cross-correlation or optical flow algorithm. ref With dynamic image I disturbed to be processed.

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