Phase-type spatial light modulator defect detection device and method based on loaded phase lens

Abstract

The present invention relates to a phase-type spatial light modulator defect detection device and method based on a phase lens. The device comprises a laser source, a collimating beam expander, a beam splitter cube, and a detector. The collimating beam expander converts laser light generated by the laser source into uniform parallel light. The uniform parallel light is transmitted through the beam splitter cube to the spatial light modulator to be tested. The light reflected by the spatial light modulator to be tested is then reflected through the beam splitter cube to the input end of the detector. The spatial light modulator is configured to focus the phase pattern of the loaded cylindrical lens. The device determines whether the bright lines in the image captured by the detector are uniform. If so, the surface of the spatial light modulator to be tested is free of defects; otherwise, the surface of the spatial light modulator to be tested has defects. Compared with existing technologies, the present invention has the advantages of improved detection efficiency.

Description

Technical Field

[0001] The present invention relates to, in particular to, a phase-type spatial light modulator defect detection device and method based on a loaded phase lens. Background Art

[0002] A spatial light modulator (SLM) is an optical element capable of modulating light waves in the spatial domain. It typically consists of a liquid crystal array, which modulates the intensity, phase, or polarization of light by controlling the state of the liquid crystals. SLMs have a wide range of applications in optical and imaging systems, including display technology, laser processing, optical communications, optical computing, and interferometry. However, during use, SLMs may develop defects that affect their performance and output quality. For example, the surface of an SLM may have an irregular shape or be uneven, resulting in distortion or uneven light intensity distribution in the optical system, affecting the quality of light transmission and causing image blur or beam distortion. Furthermore, incorrect gamma curve calibration of the SLM can cause the modulation state to deviate from expectations, affecting the final modulation effect. The stability and reliability of the SLM's modulation performance have a significant impact on the overall performance of the system. However, during the SLM production process, surface defects and inaccurate phase modulation may occur.

[0003] Traditional detection methods usually rely on complex equipment or time-consuming detection processes, which not only increases production costs but also reduces detection efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a phase-type spatial light modulator defect detection device and method based on a loaded phase lens.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A phase-type spatial light modulator defect detection device based on a loaded phase lens includes a laser source, a collimating beam expander, a beam splitter cube, and a detector. The collimating beam expander converts laser light generated by the laser source into uniform parallel light. The uniform parallel light is transmitted to the spatial light modulator to be tested through the beam splitter cube. The light reflected by the spatial light modulator to be tested is then reflected to the input end of the detector through the beam splitter cube. The spatial light modulator is configured to focus the phase pattern of the loaded cylindrical lens.

[0007] It is determined whether the bright lines in the image collected by the detector are uniform. If so, the surface of the spatial light modulator to be tested has no defects. Otherwise, the surface of the spatial light modulator to be tested has defects.

[0008] The beam splitting cube includes a half-reflecting half-mirror, and the part of the uniform parallel light transmitted through the half-reflecting half-mirror is directed toward the spatial light modulator to be measured; the part of the light focused by the spatial light modulator to be measured is reflected by the half-reflecting half-mirror and directed toward the detector.

[0009] The positional relationship between the beam splitting cube, the detector and the spatial light modulator to be measured satisfies:

[0010]

[0011] Where: d1 is the distance from the detector to the center of the beamsplitter cube, d2 is the distance from the center of the beamsplitter cube to the spatial light modulator to be measured, f is the focal length of the loaded cylindrical lens, t is the thickness of the beamsplitter cube, and n is the refractive index of the beamsplitter cube.

[0012] The center of the beam splitting cube is the center of the half-reflecting half-mirror.

[0013] The spatial light modulator is a reflective spatial light modulator.

[0014] The detector is a camera.

[0015] A method based on any of the above devices, comprising:

[0016] Step S1: Controlling the spatial light modulator to be tested to load a phase diagram of an ideal cylindrical lens;

[0017] Step S2: determining whether the bright lines in the image collected by the detector are uniform. If so, executing step S3; otherwise, there is a defect on the surface of the spatial light modulator to be tested.

[0018] Step S3: After superimposing different noises on the ideal cylindrical lens, return to step S2 until the bright lines obtained under all noises are uniform.

[0019] The superposition noise takes the form of a phase pattern of a rotating ideal cylindrical lens.

[0020] The rotation angles include 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees.

[0021] The phase expression of the ideal cylindrical lens is:

[0022]

[0023] Where: k is the wave vector and x is the coordinate of the horizontal space position.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. By loading a cylindrical lens for detection, the linear focusing characteristics of the cylindrical lens can be used to focus the SLM modulated light beam into a line. By observing and analyzing the light intensity distribution and phase characteristics of this line, the modulation accuracy of the SLM can be quickly determined. This method does not require complex equipment and tedious calibration processes. It is suitable for large-scale production and quality control, and can also be used for performance evaluation and fault diagnosis of existing SLMs, thereby improving the reliability and stability of the entire system.

[0026] 2. By superimposing some noise, or errors, and observing the focusing results by rotating at different angles, the accuracy of detection can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention;

[0028] Figure 2 is a schematic diagram of focusing of a cylindrical lens;

[0029] Figure 3 is the phase of a cylindrical lens with a focal length of 150 mm;

[0030] Figure 4 This is a schematic diagram of the focusing result of a cylindrical lens with a focal length of 150mm;

[0031] Figure 5 This is a schematic diagram of the light intensity value of the 1080th column;

[0032] Figure 6 Schematic diagram of focusing effect of cylindrical lens rotated at different angles;

[0033] Among them: 1. Laser source, 2. Collimating beam expander, 3. Beam splitter cube, 4. Spatial light modulator, 5. Detector, where (a) is 0 degrees, (b) is 30 degrees, (c) is 45 degrees, (d) is 60 degrees, (e) is 75 degrees, and (f) is 90 degrees. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] In order to simplify and speed up the testing process, the present application proposes a method for detecting modulation defects in phase-type SLM by loading a phase lens. This method utilizes the characteristics of the phase lens. By loading the phase lens, the SLM can be efficiently and accurately detected without the need for complex equipment. Specifically, this method can judge the accuracy of its phase modulation and surface defects by observing the output light field characteristics of the SLM after loading the phase lens. The loading of the phase lens can produce specific light field patterns. By analyzing the changes in these patterns, it can be identified whether there are errors in the phase modulation of the SLM and whether there are defects such as unevenness on the surface. Compared with traditional methods, this detection method is simpler and more efficient, which not only improves the detection speed but also reduces the detection cost. This new method is not only suitable for quality control of SLM in the production process, but can also be used for performance evaluation and fault diagnosis of existing SLM. Through this efficient detection method, the reliability and stability of the SLM in various applications can be ensured, thereby improving the performance and quality of the overall system.

[0036] Conventional methods for detecting the surface shape and modulation of spatial light modulators (SLMs) include interferometry, wavefront sensors, Fourier transforms, beam profiling, microscopy, and coherent beam imaging. Interferometry utilizes interference fringes to analyze phase error and surface shape, offering high precision and resolution, but the equipment is complex and requires strict environmental requirements. Wavefront sensors monitor the SLM's modulation state in real time by capturing wavefront distortion, making it suitable for phase measurement over a wide range. However, this method is costly and requires complex calibration and data processing. Fourier transforms extract modulation characteristics by analyzing frequency domain information, making it suitable for analyzing complex patterns, but data processing is complex. Beam profiling determines the modulation effect by analyzing the cross-sectional profile of the beam. This method is simple to operate and offers good real-time performance, but its accuracy is limited. Microscopy directly observes the SLM surface to detect defects and unevenness. This method is intuitive and offers high resolution, but is limited to surface inspection. Coherent beam imaging captures light field images to analyze phase and intensity distributions, making it suitable for detecting complex modulations. However, this method requires complex equipment and high data processing requirements.

[0037] The advantages of using a cylindrical lens to inspect SLMs lie in their efficiency, simplicity, and cost-effectiveness. Leveraging the linear focusing properties of the cylindrical lens, the SLM-modulated light beam can be focused into a single line. By observing and analyzing the intensity distribution and phase characteristics of this line, the modulation accuracy of the SLM can be quickly determined. This method, which eliminates the need for complex equipment and tedious calibration procedures, is suitable for large-scale production and quality control. It can also be used for performance evaluation and troubleshooting of existing SLMs, thereby improving overall system reliability and stability.

[0038] The phase expression of a conventional spherical lens is: Among them, k is the wave vector, f is the focal length, x is the coordinate of the horizontal space position, y is the coordinate of the vertical space position, and the expression of k is So the phase expression of the cylindrical lens can be expressed as

[0039] From the expression, we can see that cylindrical lenses have different optical properties than spherical lenses. A cylindrical lens is an optical lens that focuses only in one dimension, without changing its vergence in the other direction. Specifically, a cylindrical lens can focus light onto a line, rather than focusing it onto a single point like a spherical lens.

[0040] This property makes cylindrical lenses very useful in certain optical applications. For example, in laser beam shaping, cylindrical lenses can transform a point laser beam into a linear beam, or shape an elliptical beam into a more circular one. In optical communications and imaging systems, cylindrical lenses can also be used to correct optical distortion or achieve specific beam manipulation.

[0041] The focal line of a cylindrical lens is parallel to its cylindrical surface, such as Figure 2 As shown:

[0042] The method of this application fully utilizes the focusing characteristics of cylindrical lenses, and determines the modulation accuracy of the spatial light modulator by observing the focusing effect. Specifically, by combining cylindrical lenses with SLMs and inputting cylindrical lenses in different directions into the spatial light modulator, the SLM modulated light beam can be focused into a line. Then, by analyzing the light intensity distribution of this bright line along different directions, the modulation effect of the SLM can be detected. If the quality of the focused line is poor, it indicates that the SLM has a modulation defect or a surface defect.

[0043] The theoretical part of this application is as follows: From the expression, it can be seen that the phase change along the x direction is 2kx / f, and the focus is at a distance f from the SLM surface along the optical axis. Figure 3 The focal length of the cylindrical lens is f = 150mm along the X direction. The number of its elements is 3840*2160. Since the shape of its phase is rectangular, the intensity distribution of the lens focal length is distributed in the X direction as a sinc function. The focusing result at 150mm is as follows Figure 4 As shown, the brightness is uniform and horizontal. Draw a plane diagram along a column of extracted values, and the light intensity distribution is as follows Figure 5 If the SLM is loaded with a cylindrical lens in the experiment, its light intensity distribution is a sinc distribution, indicating that the SLM has no surface shape and gamma correction defects; otherwise, there are defects.

[0044] Specifically, a phase-type spatial light modulator defect detection device based on a loaded phase lens is provided, such as Figure 1As shown, it includes a laser source 1, a collimating beam expander 2, a beam splitting cube 3 and a detector 5. The collimating beam expander 2 converts the laser light generated by the laser source 1 into uniform parallel light. After the uniform parallel light is transmitted through the beam splitting cube 3 to the spatial light modulator 4 to be measured, the light reflected by the spatial light modulator 4 to be measured is reflected through the beam splitting cube 3 to the input end of the detector 5. The spatial light modulator 4 is configured to load the phase pattern of the cylindrical lens for focusing.

[0045] It is determined whether the bright lines in the image collected by the detector 5 are uniform. If so, the surface of the spatial light modulator 4 to be tested has no defects. Otherwise, the surface of the spatial light modulator 4 to be tested has defects.

[0046] Specifically, the beam splitting cube 3 includes a half-reflecting half-mirror, and the uniform parallel light is transmitted through the half-reflecting half-mirror and directed toward the spatial light modulator 4 to be measured; the light focused by the spatial light modulator 4 to be measured is reflected through the half-reflecting half-mirror and directed toward the detector 5.

[0047] The positional relationship between the beam splitting cube 3, the detector 5 and the spatial light modulator 4 to be measured satisfies:

[0048]

[0049] Wherein: d1 is the distance from the detector 5 to the center of the beam splitter cube 3, d2 is the distance from the center of the beam splitter cube 3 to the spatial light modulator 4 to be measured, f is the focal length of the loaded cylindrical lens, t is the thickness of the beam splitter cube 3, and n is the refractive index of the beam splitter cube 3.

[0050] Furthermore, the center of the beam splitting cube 3 is the center of a half-reflective half-mirror, and the spatial light modulator 4 is a reflective spatial light modulator. Generally, the detector 5 is a camera.

[0051] A method based on the above device includes:

[0052] Step S1: Controlling the spatial light modulator 4 to be tested to load a phase diagram of an ideal cylindrical lens;

[0053] Step S2: determining whether the bright lines in the image collected by the detector 5 are uniform. If so, executing step S3; otherwise, there is a defect on the surface of the spatial light modulator 4 to be tested.

[0054] Step S3: After superimposing different noises on the ideal cylindrical lens, return to step S2 until the bright lines obtained under all noises are uniform.

[0055] The superposition noise takes the form of a phase pattern of a rotating ideal cylindrical lens.

[0056] The rotation angles include 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees. According to the above method, some noise, or error, is superimposed on the phase of the ideal cylindrical lens. The focusing results are observed by rotating at different angles. The results after focusing at the rotation angle are as follows: Figure 6 As shown, through simulation, it is found that at 0°, there is no problem in observation, but when the cylindrical lens is rotated to different angles, it is found that the focused bright line is no longer uniform, and the unevenness is particularly obvious when rotated 90°. Therefore, when the SLM has a surface defect, the focused bright line will not be uniform. Therefore, the method of the present application of judging whether there is a defect in the phase-type spatial light modulator by loading a phase lens is feasible.

[0057] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

Claims

1. A phase-type spatial light modulator defect detection device based on a loaded phase lens, characterized in that: The invention comprises a laser source (1), a collimating beam expander (2), a beam splitting cube (3) and a detector (5), wherein the collimating beam expander (2) converts the laser light generated by the laser source (1) into uniform parallel light, and the uniform parallel light is transmitted to the spatial light modulator (4) to be measured through the beam splitting cube (3), and the light reflected by the spatial light modulator (4) to be measured is reflected to the input end of the detector (5) through the beam splitting cube (3), wherein the spatial light modulator (4) is configured to load the phase pattern of the cylindrical lens for focusing; It is determined whether the bright lines in the image collected by the detector (5) are uniform. If so, the surface of the spatial light modulator (4) to be tested has no defects. Otherwise, the surface of the spatial light modulator (4) to be tested has defects.

2. The phase-type spatial light modulator defect detection device based on a loaded phase lens according to claim 1, characterized in that: The beam splitting cube (3) comprises a half-reflecting half-mirror, and the portion of the uniform parallel light transmitted through the half-reflecting half-mirror is directed toward the spatial light modulator (4) to be measured; and the portion of the light focused by the spatial light modulator (4) to be measured is reflected through the half-reflecting half-mirror and directed toward the detector (5).

3. The phase-type spatial light modulator defect detection device based on a loaded phase lens according to claim 2, characterized in that: The positional relationship between the beam splitting cube (3), the detector (5) and the spatial light modulator (4) to be measured satisfies: in: d 1 is the distance from the detector (5) to the center of the beam splitter cube (3), d 2 is the distance from the center of the beam splitter cube (3) to the spatial light modulator (4) to be measured, f is the focal length of the loaded cylindrical lens, t is the thickness of the beam splitter cube (3), n is the refractive index of the beamsplitter cube (3).

4. The phase-type spatial light modulator defect detection device based on a loaded phase lens according to claim 3, characterized in that: The center of the beam splitting cube (3) is the center of a half-reflecting half-mirror.

5. The phase-type spatial light modulator defect detection device based on a loaded phase lens according to claim 1, characterized in that: The spatial light modulator (4) is a reflective spatial light modulator.

6. The phase-type spatial light modulator defect detection device based on a loaded phase lens according to claim 1, characterized in that: The detector (5) is a camera.

7. A method based on the device according to any one of claims 1 to 6, characterized in that: include: Step S1: Control the spatial light modulator (4) to be tested to load the phase diagram of the ideal cylindrical lens; Step S2: determining whether the bright lines in the image collected by the detector (5) are uniform; if so, executing step S3; otherwise, there is a defect on the surface of the spatial light modulator (4) to be tested; Step S3: After superimposing different noises on the ideal cylindrical lens, return to step S2 until the bright lines obtained under all noises are uniform.

8. The method according to claim 7, characterized in that The superposition noise takes the form of a phase pattern of a rotating ideal cylindrical lens.

9. The method according to claim 8, characterized in that The rotation angles include 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees.

10. The method according to claim 7, characterized in that The phase expression of the ideal cylindrical lens is: in: k is the wave vector, x is the coordinate of the horizontal space position, y is the coordinate of the vertical space position, f is the focal length of the loaded cylindrical lens.

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