System and equipment for measuring spatial phase delay distribution of liquid crystal phase devices

Abstract

This invention relates to the field of light field modulation and optical information processing technology, and in particular to a system and device for measuring the spatial phase delay distribution of a liquid crystal phase device. The system uses a light source to output light, and a polarization filter module to convert the output light into monochromatic polarized light that can be modulated by the liquid crystal phase device. This light is then modulated by the liquid crystal phase device located in front of the polarization filter module. Finally, an image acquisition module captures the intensity image of the modulated light from the liquid crystal phase device for calculating its spatial phase delay distribution. This system is low in complexity and offers high accuracy and efficiency in measuring the spatial phase delay distribution of the liquid crystal phase device, solving the problems of low efficiency and poor accuracy in existing technologies for measuring the spatial phase delay distribution of liquid crystal phase devices.

Description

Technical Field

[0001] This utility model relates to the field of optical field modulation and optical information processing technology, specifically to a system and device for measuring the spatial phase delay distribution of a liquid crystal phase device. Background Technology

[0002] As a key electro-optic modulation device in polarization equipment, liquid crystal phase devices are advantageous due to their lack of rotational structure, high modulation speed, large aperture, light weight, wide spectral range, low driving voltage, and phase delay of 0~2 seconds. With its advantages such as continuous adjustability, liquid crystal phase devices are widely used in adaptive optics, ground remote sensing, wavefront correction, beamforming, and interferometry. However, due to factors such as alignment process errors of liquid crystal materials, non-uniform distribution of driving voltage, and packaging stress, the phase delay and polarization response characteristics of different regions of the device target surface exhibit spatial non-uniformity, leading to a decrease in spatial phase modulation accuracy. Therefore, to achieve high-precision electrically controlled phase modulation, it is necessary to perform full-domain measurement of the spatial phase delay distribution of liquid crystal phase devices.

[0003] Currently, traditional measurement methods are mainly divided into two categories: single-point interferometry and time-division polarization modulation (TDM). Single-point interferometry can only calculate the phase delay at the center point of the device through interference fringes. To obtain the spatial phase delay distribution characteristics of liquid crystal devices, a high-precision displacement stage must be used to scan the device point by point, which increases measurement time and easily introduces vibration errors during the scanning process. On the other hand, TDM requires measuring the 0° linear polarization intensity, 45° linear polarization intensity, and 90° linear polarization intensity of the modulated light, and requires mechanically rotating waveplates or inserting quarter-waveplates to measure the circular polarization component separately, which complicates the optical path and introduces mechanical errors and polarization crosstalk, reducing measurement efficiency and accuracy. In addition, existing methods rely on multi-frame image stitching or time-series scanning, which is difficult to meet the real-time detection requirements of dynamic phase modulation of liquid crystal phase devices. Therefore, there is an urgent need to develop a spatial phase delay distribution measurement technology that does not require mechanical movement and supports single-shot imaging to address the shortcomings of existing measurement methods in terms of spatial resolution, measurement efficiency, and reliability. Utility Model Content

[0004] To address the problems of low efficiency and poor accuracy in measuring the spatial phase delay distribution of liquid crystal phase devices in existing technologies, this invention provides a system and device for measuring the spatial phase delay distribution of liquid crystal phase devices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a system for measuring the spatial phase delay distribution of a liquid crystal phase device, comprising a light source, a polarization filtering module, and an image acquisition module; The light source is used to emit light to the target surface of the liquid crystal phase device; the polarization filtering module is located between the light source output end of the light source and the target surface of the liquid crystal phase device, and is used to generate monochromatic linearly polarized light that can be modulated by the liquid crystal phase device; the image acquisition module is located at the front end of the liquid crystal phase device, and is used to acquire the light intensity image modulated by the liquid crystal phase device.

[0006] Optionally, the light source is a uniform light source.

[0007] Optionally, the spectral adjustment range of the uniform light source is 350–1000 nm.

[0008] Optionally, the light source output end is provided with a collimator.

[0009] Optionally, the polarization filtering module includes a filter and a linear polarizer sequentially disposed on the optical axis of the light source.

[0010] Optionally, the size of the filter and the linear polarizer is comparable to that of a liquid crystal phase device.

[0011] Optionally, the center wavelength of the filter is 432nm and the bandwidth is 10nm; the diameter of the linear polarizer is 50.8mm.

[0012] Optionally, the image acquisition module is a multi-aperture polarization camera.

[0013] Optionally, the light intensity image modulated by the liquid crystal phase device includes the light intensity in the 0° linear polarization direction, the light intensity in the 45° linear polarization direction, the light intensity in the 90° linear polarization direction, and the light intensity in the right-hand circular polarization direction of the light field modulated by the liquid crystal phase device.

[0014] A polarization device includes the aforementioned liquid crystal phase device spatial phase delay distribution measurement system.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a system for measuring the spatial phase delay distribution of a liquid crystal phase device. The system sets up a light source to output light, and uses a polarization filtering module to polarize the light output from the light source, converting it into monochromatic polarized light that can be modulated by the liquid crystal phase device. The light is then modulated by the liquid crystal phase device located in front of the polarization filtering module. Finally, an image acquisition module is used to acquire the intensity image of the light modulated by the liquid crystal phase device for calculating the spatial phase delay distribution of the liquid crystal phase device. This system, through ingenious light source setup, polarization filter module design, and collaborative operation with liquid crystal phase devices, eliminates the need for frequent rotation of quarter-wave plates to acquire light information under different polarization states when acquiring data on the spatial phase delay distribution of liquid crystal phase devices. This reduces system complexity and significantly minimizes errors caused by mechanical motion. Furthermore, it eliminates the need for high-precision displacement stages to scan the device point-by-point, avoiding the introduction of vibration errors and greatly improving the measurement accuracy of the spatial phase delay distribution of liquid crystal phase devices. Compared to traditional single-point measurements, this system, by eliminating the need for high-precision displacement stages to scan the device point-by-point and avoiding vibration errors, significantly enhances the measurement accuracy and efficiency of the spatial phase delay distribution of liquid crystal phase devices, demonstrating broad application prospects in display manufacturing, optical communication, quantum technology, and biomedicine.

[0016] The light source is a uniform light source. The light emitted by the uniform light source has a uniform distribution of light intensity, phase, and polarization state at all positions. When passing through the polarization filtering module, it can ensure that the light across the entire beam cross-section is subjected to consistent polarization processing, thereby further ensuring the accuracy of the light intensity image acquired by the image acquisition module, and thus improving the accuracy of the spatial phase delay distribution measurement of the liquid crystal phase device.

[0017] The spectral adjustment range of the uniform light source is 350–1000 nm. This wavelength band is the core operating region of the liquid crystal phase device. The uniform light source can provide stable and continuous visible light output, ensuring that the polarization filter module can accurately generate monochromatic polarized light and meet the basic requirements of device modulation.

[0018] The light source output is equipped with a collimator. In the measurement system, the light emitted by the uniform light source originally has a certain divergence angle. If it directly enters the polarization filtering module, the polarization conversion efficiency of light rays at different angles will vary due to differences in the incident angle, resulting in non-uniformity of polarized light. However, the parallel light output from the collimator is incident on the polarization filtering module at an approximately perpendicular angle, ensuring the consistency of polarization conversion. This provides a stable and uniform polarized light input for the subsequent modulation of the liquid crystal phase device, improving the optical path quality from the source.

[0019] The polarization filtering module includes a filter and a linear polarizer sequentially arranged on the optical axis of the light source. The light emitted by the light source typically contains multiple wavelength components, while the liquid crystal phase device modulates light of a specific wavelength band. The filter selectively transmits light of the target wavelength band while blocking light of other wavelength bands. The linear polarizer converts the incident light into linearly polarized light with a single polarization direction, ensuring that the light entering the liquid crystal device has a definite polarization direction, thus providing standardized input conditions for accurately measuring the spatial phase delay distribution.

[0020] The size of the filter and linear polarizer is comparable to that of the liquid crystal phase device to ensure that they can completely cover the beam range passing through the liquid crystal device in the optical path, and ensure that all light entering the liquid crystal device is filtered and polarized first, thereby minimizing light energy loss and improving light transmission efficiency.

[0021] The image acquisition module is a split-aperture polarization camera. By setting up micro-polarizer arrays in different regions of the camera chip, the split-aperture polarization camera can simultaneously acquire images of multiple polarization directions (typically 0°, 45°, 90°, and 135°) in the same scene. In the measurement of spatial phase delay distribution of liquid crystal phase devices, the modulation of light by the liquid crystal device produces complex polarization state changes. Using a split-aperture polarization camera, information on these different polarization directions can be acquired at once, completely capturing the polarization state distribution of the emitted light, providing comprehensive data support for accurately analyzing the phase delay characteristics of the liquid crystal device.

[0022] The light intensity image modulated by the liquid crystal phase device includes the light intensity in the 0° linear polarization direction, the 45° linear polarization direction, the 90° linear polarization direction, and the right-hand circular polarization direction of the light field modulated by the liquid crystal phase device.

[0023] This invention also provides a polarization device, including the aforementioned spatial phase delay distribution measurement system for liquid crystal phase devices. This device can achieve the final measurement of the spatial phase delay distribution of liquid crystal phase devices without the need for a rotating quarter-wave plate, making it suitable for real-time measurement. Compared with traditional single-point interferometry methods, it improves measurement efficiency and reduces vibration errors during the scanning process. Compared with traditional time-division polarization modulation techniques, it effectively simplifies the optical path, features stable operation and flexible control, and can adapt to the spatial distribution measurement requirements of different liquid crystal phase devices after modulation, thus having broad application prospects. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the spatial phase delay distribution measurement system for a liquid crystal phase device according to the present invention.

[0025] Figure 2The spatial phase retarder characteristic curve (a) and the phase retardation variation at each point along the vertical diameter direction of the liquid crystal variable phase retarder (LCVR) are shown in the embodiment of this utility model when the incident light polarization angle is 20°.

[0026] Figure 3 The spatial phase retarder characteristic curve (a) and the phase retarder variation at each point along the vertical diameter direction of the liquid crystal variable phase retarder (LCVR) are shown in the embodiment of this utility model when the incident light polarization angle is 40°.

[0027] Figure 4 This is a comparison of the phase characteristic curves of a liquid crystal variable phase retarder (LCVR) when the incident light wavelength is 432nm, with five different polarization angles of 20°, 30°, 40°, 50°, and 60°.

[0028] Figure 5 The present invention utilizes a preset grating spatial phase distribution map (a) and a measured spatial phase distribution map (b) on a liquid crystal spatial light modulator (LC-SLM) in the embodiment.

[0029] Figure 6 The present invention utilizes a checkerboard spatial phase distribution map (a) preset on a liquid crystal spatial light modulator (LC-SLM) and a measured spatial phase distribution map (b).

[0030] Among them, 1-uniform light source, 2-parallel light tube, 3-filter, 4-linear polarizer, 5-liquid crystal phase device, 6-aperture polarization camera, 7-host computer, A-light source, B-polarization filter module, C-image acquisition module. Detailed Implementation

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

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The present invention will be further described in detail below with reference to specific embodiments. The description is for explanation and not limitation of the present invention.

[0034] See Figure 1 This utility model discloses a spatial phase delay distribution measurement system for a liquid crystal phase device, including a light source A, a polarization filtering module B, and an image acquisition module C; The light source A is used to emit light to the target surface of the liquid crystal phase device 5, providing a stable and uniform parallel light field to the target surface of the liquid crystal phase device 5. The light source A includes a uniform light source 1 and a collimator 2. The collimator 2 is located at the light source output end of the uniform light source 1 and is used to collimate the emitted light from the uniform light source 1. Preferably, the uniform light source 1 in the light source A adopts a multifunctional uniform light source integrating sphere of model CSTM-CT-100-RGBW from Lanfei Optics, with a spectral adjustment range of 350-1000nm, which can provide output light with a spatial intensity distribution uniformity of >98%. The collimator 2 adopts a collimator of model ABF-1000 from Xi'an Angke Optoelectronics Co., Ltd., which can collimate the uniform incident light field before outputting it.

[0035] The polarization filtering module B is located at the light source output end of the light source A and the target surface of the liquid crystal phase device 5, generating a linearly polarized monochromatic uniform light field that can be modulated by the liquid crystal phase device 5. The polarization filtering module B includes a filter 3 and a linear polarizer 4 arranged sequentially along the light source optical axis of the light source A. Preferably, the center wavelength of the filter 3 is 432nm, the bandwidth is 10nm, and the transmittance is >95% within the effective wavelength range. Furthermore, the size of the filter 3 and the linear polarizer 4 is 50.8mm in diameter, and the light passing through the filter 3 and the linear polarizer 4 can completely cover the target surface of the liquid crystal phase device 5.

[0036] The liquid crystal phase device 5 uses the H16209 series liquid crystal variable phase delay (LCVR) and Sn5473 series 1920x1152 resolution liquid crystal spatial light modulator (LC-SLM) from Meadowlark Optics, and the fast axis direction of the liquid crystal phase device (5) is set as the reference axis direction. The liquid crystal phase device 5 is connected to a host computer 7.

[0037] The image acquisition module C is located at the front end of the liquid crystal phase device 5 and is used to acquire the modulated light intensity image of the liquid crystal phase device 5. The image acquisition module C uses a single-aperture polarization camera 6 to simultaneously acquire 0° linearly polarized, 45° linearly polarized, 90° linearly polarized and right-hand circularly polarized light intensity images modulated by the liquid crystal phase device 5, and transmits the images to the host computer 7. The image acquisition module C is located at the front end of the liquid crystal phase device 5 and is used to acquire the modulated light intensity image of the liquid crystal phase device 5. Optionally, the image acquisition module C uses a single-aperture polarization camera 6 to simultaneously acquire 0° linearly polarized, 45° linearly polarized, 90° linearly polarized and right-hand circularly polarized light intensity images modulated by the liquid crystal phase device 5, and transmits the images to the host computer 7. When using the above system to measure the spatial phase delay distribution of the liquid crystal phase device 5, firstly, a measurement system based on a split-aperture polarization camera is built according to the equipment structure. The uniform light source 1 and collimator 2 of light source A are adjusted to output a parallel light field that completely covers the target surface of the liquid crystal phase device 5 and has appropriate optical power. The direction of the linear polarizer 4 is adjusted to generate linearly polarized light with a known polarization direction. A driving voltage is applied to the liquid crystal phase device 5 to modulate the phase of the incident light. After modulation by the liquid crystal phase device 5, the parallel light field is captured by the split-aperture polarization camera 6 in the light intensity images of the outgoing light in the 0°, 45°, 90°, and right-hand circular polarization directions, and uploaded to the host computer 7. The Stokes vector of the modulated light intensity image light field of the liquid crystal phase device 5 satisfies the following condition:

[0038] in, The light intensity in the 0° linear polarization direction of the light field modulated by the liquid crystal phase device 5. The light intensity in the 45° linear polarization direction of the light field modulated by the liquid crystal phase device 5. This represents the light intensity along the 90° linear polarization direction of the light field modulated by the liquid crystal phase device 5. The light intensity in the right-hand circularly polarized direction of the light field modulated by the liquid crystal phase device 5. The light intensity in the left-hand circularly polarized direction of the light field modulated by the liquid crystal phase device 5. This represents the light intensity along the 135° linear polarization direction of the light field modulated by the liquid crystal phase device 5. This represents the total light intensity of the light field after modulation by the liquid crystal phase device 5. The intensity difference between the 0° and 90° polarization components of the optical field modulated by the liquid crystal phase device. The intensity difference between the 45° and 135° polarization components of the optical field modulated by the liquid crystal phase device. The difference in light intensity is the difference between the right-hand and left-hand circularly polarized components of the light field modulated by the liquid crystal phase device.

[0039] The polarization angle and ellipticity angle of the spatial distribution of the light field modulated by the liquid crystal phase device 5 satisfy the following conditions:

[0040]

[0041] in, The polarization angle represents the spatial distribution of the light field modulated by the liquid crystal phase device 5. The ellipticity angle represents the spatial distribution of the light field after modulation by the liquid crystal phase device 5.

[0042] The spatial phase delay distribution of the liquid crystal phase device 5 satisfies the following conditions:

[0043] in, The polarization angle of linear polarizer 4 relative to the reference axis. This refers to the phase delay generated by the liquid crystal phase device 5.

[0044] See Figures 2 to 6 The measurement results of the spatial phase delay characteristics of the above system for liquid crystal devices are divided into two parts: liquid crystal variable phase delay device (LCVR) and liquid crystal spatial light modulator (LC-SLM). Figures 2 to 4 The experimental results of measuring the spatial phase delay of LCVR. Figures 5-6 The results are from the LC-SLM spatial phase delay measurement experiment. Figure 2 , Figure 3 The spatial phase retarding characteristic curves of LCVR and the phase delay variation curves at various points along the vertical diameter are presented when the incident polarization angle is 20° and 40°, respectively. The experiment shows that when the incident polarization angle is changed, the variation trend of the spatial phase retarding characteristic curve of LCVR and the spatial distribution of the phase delay on the target surface are in high agreement with the theoretical model. Figure 4 This further reveals that the phase delay generated by LCVR does not depend on the polarization angle of the incident light, indicating that the measurement method has a certain degree of stability.

[0045] This embodiment of the invention further verifies the universality of the measurement method on liquid crystal phase devices by loading a spatial phase distribution onto an LC-SLM. Loading onto an LC-SLM Figure 5 The binary grating-type phase distribution shown in figure a (with preset phases of 0 rad and π rad corresponding to grayscale values ​​of 0 and 125 respectively) is used to measure the phase delay distribution obtained by a split-aperture polarization camera as follows: Figure 5 As shown in b. The calculated mean measurement value of this method in the 0 rad phase region is 0.031 rad, with a root mean square error (RMSE) of 0.028 rad; the mean measurement value in the π rad phase region is 3.103 rad, with an RMSE of 0.027 rad. Loading on the LC-SLM... Figure 6 The checkerboard phase distribution shown in figure a (with preset phases of 0 rad and π rad corresponding to grayscale values ​​of 0 and 125 respectively) is used to measure the phase delay distribution using a split-aperture polarization camera, as shown in figure a. Figure 6 As shown in b, the calculated mean measurement value of this method in the 0 rad phase region is 0.027 rad, with a root mean square error (RMSE) of 0.022 rad; the mean measurement value in the π rad phase region is 3.086 rad, with an RMSE of 0.051 rad. Comparative analysis verifies that the method for measuring the spatial phase delay distribution of liquid crystal phase devices based on a multi-aperture polarization camera is relatively accurate when applied to LC-SLM. This not only demonstrates the versatility of this system on different liquid crystal phase devices but also proves the effectiveness and stability of the system presented in this paper.

[0046] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the technical solution of the present utility model in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present utility model, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A system for measuring the spatial phase delay distribution of a liquid crystal phase device, characterized in that, Includes a light source, a polarization filtering module, and an image acquisition module; The light source is used to emit light to the target surface of the liquid crystal phase device; the polarization filtering module is located between the light source output end of the light source and the target surface of the liquid crystal phase device, and is used to generate monochromatic linearly polarized light that can be modulated by the liquid crystal phase device; the image acquisition module is located at the front end of the liquid crystal phase device, and is used to acquire the light intensity image modulated by the liquid crystal phase device.

2. The liquid crystal phase device spatial phase delay distribution measurement system according to claim 1, characterized in that, The light source is a uniform light source.

3. The spatial phase delay distribution measurement system for a liquid crystal phase device according to claim 2, characterized in that, The spectral adjustment range of the uniform light source is 350–1000 nm.

4. The liquid crystal phase device spatial phase delay distribution measurement system according to claim 1, characterized in that, The light source output end is equipped with a collimator.

5. The spatial phase delay distribution measurement system for a liquid crystal phase device according to claim 1, characterized in that, The polarization filtering module includes a filter and a linear polarizer arranged sequentially on the optical axis of the light source.

6. The liquid crystal phase device spatial phase delay distribution measurement system according to claim 5, characterized in that, The dimensions of the filter and linear polarizer are comparable to those of a liquid crystal phase device.

7. The liquid crystal phase device spatial phase delay distribution measurement system according to claim 5, characterized in that, The center wavelength of the filter is 432nm and the bandwidth is 10nm; the diameter of the linear polarizer is 50.8mm.

8. The spatial phase delay distribution measurement system for a liquid crystal phase device according to claim 1, characterized in that, The image acquisition module is a multi-aperture polarization camera.

9. The liquid crystal phase device spatial phase delay distribution measurement system according to claim 1, characterized in that, The light intensity image modulated by the liquid crystal phase device includes the light intensity in the 0° linear polarization direction, the 45° linear polarization direction, the 90° linear polarization direction, and the right-hand circular polarization direction of the light field modulated by the liquid crystal phase device.

10. A polarization device, characterized in that, The system includes the spatial phase delay distribution measurement system for liquid crystal phase devices as described in any one of claims 1-9.

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