Time-sharing polarization imaging method and system, and industrial detection device

Abstract

The present application relates to a time-sharing polarization imaging method and system, and an industrial inspection device, wherein a first linear polarized light is incident on a high-speed liquid crystal panel; the high-speed liquid crystal panel displays a calibration image and converts the first linear polarized light into adjusted polarized light and incidents it on a subject; the subject generates reflected or transmitted light that is incident on a second linear polarizer and then incident on a camera, and the camera captures a polarization image corresponding to the second linear polarized light of the calibration image; it is determined that three calibration images corresponding to the first linear polarizer and the second linear polarizer at 90 degrees, 45 degrees, and 0 degrees have all been captured to obtain polarization images; and the polarization parameters of the subject at each pixel are calculated based on the three polarization images. This method avoids the accuracy and efficiency problems caused by the traditional time-sharing polarization imaging system that uses a rotating polarizer to collect images, and avoids the complex structure and high cost of the simultaneous polarization imaging system. It can be integrated with traditional visual inspection methods and is particularly suitable for application in the field of industrial inspection.

Description

Technical Field

[0001] The present application relates to the fields of machine vision and industrial inspection, and in particular to a time-sharing polarization imaging method and system, and an industrial inspection device. Background Art

[0002] The polarization state of light waves is a rich source of information. For example, the polarization states of radiated, reflected, transmitted, and scattered light carry a wealth of valuable information, making their measurement crucial. Polarimetry and ellipsometry are widely used in fields such as physics, chemistry, optics, electronics, metallurgy, biology, and medicine, and can be applied in machine vision, industrial inspection, and measurement.

[0003] Commonly used polarization measurement methods are as follows:

[0004] 1. Time-sharing polarization imaging

[0005] A division of time polarimeter (DoTP) system uses dynamic components to capture intensity images of different polarization directions at different times and then deconstruct the polarization information. The simplest method involves rotating the polarizer to capture images, but this method can produce significant errors, reducing imaging accuracy. Furthermore, manual or mechanical movement can cause beam drift and slow the process.

[0006] 2. Simultaneous polarization imaging system

[0007] Compared to time-sharing polarization imaging, simultaneous polarization imaging systems can acquire multiple polarization images of a target at different angles with a single exposure. Image acquisition and decomposition occur simultaneously, making them less susceptible to the target's motion and polarization characteristics. Furthermore, without the need for polarizer rotation, simultaneous polarization imaging offers relatively high stability and accuracy, making it suitable for dynamic measurement of moving targets. Typical simultaneous polarization imaging methods include amplitude-based, aperture-based, and focal-plane-based methods.

[0008] 2.1 Division of Amplitude Polarimeter (DoAmP)

[0009] The incident light is split into multiple beams simultaneously using a spectroscopic prism, which are then modulated by a spectroscopic device and incident on the corresponding detector to obtain an intensity image with different polarization information, which is then fused into a polarization image through an algorithm.

[0010] Incident light is split into two beams by a beamsplitter prism, each of which then passes through a polarization beamsplitter prism to produce four polarized beams. Four CCDs detect these beams, yielding four polarization images and, subsequently, four Stokes vector images. This system can simultaneously capture multiple polarization component images, offering fast response and high processing efficiency. However, due to the multiple optical subsystems and CCD detection system, it is bulky and expensive, and variations in the parameters of each subsystem can easily lead to errors.

[0011] 2.2 Division of Aperture Polarimeter (DoAP)

[0012] Unlike amplitude-splitting polarization beamsplitting prisms, aperture-splitting polarization imaging systems utilize an off-axis eccentricity to simultaneously split the incident light into four beams. Different polarizers are placed in each optical path, allowing simultaneous acquisition of polarization information from the same target in multiple, different directions at the detector's focal plane. Ploaris Sensor Technologies, a US company, has developed an aperture-splitting polarization imaging system implemented using a microlens assembly. This microlens assembly splits the incident light into four components, which are then passed through four micro-polarizers at angles of 0, 45, 90, and 135 degrees, respectively. Four images containing different polarization information are then captured on the CCD. This system offers advantages such as fast response, ease of processing, and a simple structure, but suffers from a loss of spatial resolution. The resulting composite polarization image is only one-quarter the detector's detection area. Furthermore, the optimal imaging focal plane for each channel is difficult to align, making it difficult to ensure the accuracy of the polarization information.

[0013] 2.3 Division of focal-plane polarimeter (DoFP)

[0014] This is a micro-polarization array integrated into the camera sensor for real-time polarization measurement. Representative examples include the PolarCam developed by 4D Tech in 2016 and the IMX250MZR CMOS polarization sensor developed by Sony. These use a metal wire-grid micro-polarization array as the core component. Each group of four micro-polarization elements is called a superpixel, each depicting four polarization directions, known as sub-pixels: 0, 45, 90, and 135 degrees. Each sub-pixel independently extracts the intensity signal of the target light's polarization direction, then decomposes the first three components of the Stokes vector to obtain information such as the degree of polarization and polarization angle of the target light field. This method is costly, resulting in a limited number of device models and low spatial resolution.

[0015] However, no matter whether it is amplitude-based, aperture-based, or focal plane-based simultaneous polarization imaging, there are problems such as complex structure that is difficult to simplify and high cost that is difficult to reduce.

[0016] In summary, existing polarization imaging methods include: time-sharing polarization imaging methods, which are low-cost but have mechanical transmission components, slow speed, and poor reliability; and simultaneous polarization imaging methods, which require complex and costly customized optical paths and sensors. Summary of the Invention

[0017] Based on this, it is necessary to provide a time-sharing polarization imaging method and system, and an industrial detection device.

[0018] In one embodiment, a time-sharing polarization imaging method includes a polarization imaging process, the polarization imaging process comprising the following steps: S220, a light source emits light, which passes through a first linear polarizer to form first linear polarized light, which is incident on a liquid crystal panel; S230, a liquid crystal panel controller controls the liquid crystal panel to display a calibration image, the liquid crystal panel converts the first linear polarized light into adjusted polarized light based on the calibration image, and the adjusted polarized light is incident on a subject; S240, the subject generates reflected light or transmitted light from the adjusted polarized light, which is incident on a second linear polarizer to form second linear polarized light; S250, the second linear polarized light is incident on a camera, and the camera captures a polarization image corresponding to the second linear polarized light of the calibration image; S260, determining whether the polarization image has been captured for three calibration images corresponding to the first linear polarizer and the second linear polarizer at 90 degrees, 45 degrees, and 0 degrees, if not, continuing to execute step S230; and S270, calculating the polarization parameter of the subject at each pixel point based on the three polarization images. The above-mentioned time-sharing polarization imaging method is based on a high-speed liquid crystal panel as a controllable polarized light generator, replacing mechanical moving parts. Since no transmission parts are required, it avoids the accuracy and efficiency problems caused by the traditional time-sharing polarization imaging system that uses rotating polarizers to collect images. In addition, since time-sharing polarization imaging is used, the complex structure and high cost of the simultaneous polarization imaging system are avoided. Therefore, it has the advantages of low cost, fast speed, high resolution, and strong customizability. It can also be integrated with traditional visual inspection methods and is particularly suitable for application in the field of industrial inspection.

[0019] Furthermore, after step S270, the time-sharing polarization imaging method further includes step S280 of identifying the object using the polarization parameters. Furthermore, after step S280, the time-sharing polarization imaging method further includes step S290 of adjusting the environmental parameters of the object based on the polarization parameters. Furthermore, in step S230, the LCD panel controller writes a first calibration image, a second calibration image, and a third calibration image to the LCD panel, corresponding to the first linear polarizer and the second linear polarizer being at 90 degrees, 45 degrees, and 0 degrees, respectively, converting the first linear polarized light into regulated polarized light with a controlled polarization direction, which is incident on the object; and in step S260, the camera captures a first polarization image, a second polarization image, and a third polarization image of the second linear polarized light corresponding to the first calibration image, the second calibration image, and the third calibration image, respectively.

[0020] In one embodiment, before the polarization imaging process, the time-sharing polarization imaging method further includes a polarization direction calibration process; the polarization direction calibration process includes the following steps: S110, a light source, a first linear polarizer, a liquid crystal panel, and a second linear polarizer are placed in parallel; S120, the light source emits light, which passes through the first linear polarizer to form first linear polarized light, which is incident on the liquid crystal panel; S130, a liquid crystal panel controller controls the liquid crystal deflection direction of the liquid crystal panel to convert the first linear polarized light into regulated polarized light with a controlled polarization direction, which is incident on the second linear polarizer; S140, The adjusted polarized light forms a second linear polarized light through the second linear polarizer and is incident on the camera; S150, the camera captures the second linear polarized light to obtain a series of images, the darkest image of which is used as the first calibration image to present the state where the first linear polarizer and the second linear polarizer are at 90 degrees, the brightest image is used as the second calibration image to present the state where the first linear polarizer and the second linear polarizer are at 0 degrees, and the image with an intermediate value between the darkest and the brightest is used as the third calibration image to present the state where the first linear polarizer and the second linear polarizer are at 45 degrees.

[0021] In one embodiment, in step S110, the first linear polarizer and the second linear polarizer maintain the same linear polarization direction; and / or,

[0022] In step S130 , the liquid crystal panel controller writes a control image into the liquid crystal panel and the liquid crystal panel displays the control image, so as to indirectly control the liquid crystal deflection direction of the liquid crystal panel.

[0023] In one embodiment, in step S130 , the pixels of the control image all have the same pixel value; and / or the control images have the same shape and / or size.

[0024] In one embodiment, in step S130, the LCD panel controller sequentially writes a control image V[n] to the LCD panel, where n is an integer from 0 to m, and the R, G, and B values ​​of the pixels of the control image V[n] are all n; wherein m is a preset natural number and m is greater than 10. Further, in step S130, the LCD panel controller sequentially writes a control image V[n] to the LCD panel, where n is an integer from 0 to 255, and the R, G, and B values ​​of the pixels of the control image V[n] are all n, that is, m is 255.

[0025] In one embodiment, the liquid crystal panel converts the first linearly polarized light into adjusted polarized light based on the control image.

[0026] In one embodiment, the response speed of the liquid crystal panel is less than 16 milliseconds; and / or the light source is a backlight source.

[0027] In one embodiment, in step S230, the LCD panel controller controls the LCD panel to display a calibration image in a preset order or a random order; and / or, in step S270, the polarization parameters of the object are calculated using the Stokes equation based on the three polarization images.

[0028] In one embodiment, before step S220, the time-sharing polarization imaging method further includes step S210, where the light source, the first linear polarizer, and the liquid crystal panel are placed in parallel.

[0029] In one embodiment, a time-sharing polarization imaging system includes: a light source, a first linear polarizer, a liquid crystal panel, a liquid crystal panel controller, a second linear polarizer, a camera, and an analysis module; the light source, the first linear polarizer, and the liquid crystal panel are placed in parallel, the liquid crystal panel controller is connected to the liquid crystal panel, and the camera is adjacent to the second linear polarizer; the light source is used to emit light, which forms first linear polarized light through the first linear polarizer and is incident on the liquid crystal panel; the liquid crystal panel controller controls the liquid crystal panel to display three calibration images in which the first linear polarizer and the second linear polarizer are at 90 degrees, 45 degrees, and 0 degrees, respectively; the liquid crystal panel is used to use the calibration images to convert the first linear polarized light into adjusted polarized light, which is incident on a subject; the second linear polarizer is used to receive light reflected by the subject from the adjusted polarized light, forming second linear polarized light that is incident on the camera, and the camera respectively captures three polarization images corresponding to the second linear polarized light of the three calibration images; and the analysis module calculates the polarization parameters of the subject based on the three polarization images.

[0030] In one embodiment, an industrial detection device includes a control device and any one of the time-sharing polarization imaging systems connected to the control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is a flow chart of an embodiment of the time-sharing polarization imaging method described in this application. Figure 2 This is a flowchart of the polarization direction calibration process of another embodiment of the time-sharing polarization imaging method described in this application. Figure 3 for Figure 2 Schematic diagram of the calibration environment of the illustrated embodiment. Figure 4 This is a flow chart of the polarization imaging process of another embodiment of the time-sharing polarization imaging method described in this application. Figure 5 for Figure 4 Schematic diagram of the calibration environment of the illustrated embodiment. Figure 6 This is a flow chart of the polarization imaging process of another embodiment of the time-sharing polarization imaging method described in this application. Figure 7 This is a flow chart of the polarization imaging process of another embodiment of the time-sharing polarization imaging method described in this application. Figure 8 This is a flow chart of the polarization imaging process of another embodiment of the time-sharing polarization imaging method described in this application. Figure 9 This is a flow chart of the polarization imaging process of another embodiment of the time-sharing polarization imaging method described in this application.

[0033] Reference numerals: light source 100 , first linear polarizing plate 200 , liquid crystal panel 300 , liquid crystal panel controller 400 , second linear polarizing plate 500 , camera 600 , object 700 . DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0037] In this application, unless otherwise expressly specified or limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or that the first feature and the second feature are indirectly in contact through an intermediate medium. Furthermore, a first feature being “above,” “above,” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below,” “below,” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0038] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more of the relevant listed items.

[0039] The present application discloses a time-sharing polarization imaging method, which includes part of the structure or all of the steps of the following embodiments; the present application also discloses a time-sharing polarization imaging system and an industrial detection device, which include part of the structure or all of the structure of the following embodiments; that is, the time-sharing polarization imaging method, the time-sharing polarization imaging system and the industrial detection device include part of the following technical features or all of the following technical features.

[0040] Polarizers are usually thin films made by artificial methods, formed by regularly arranging selectively absorbing microcrystals in a transparent adhesive layer. Polarizers allow light with a certain electric vector vibration direction to pass through, and this vibration direction is the polarization direction, or polarization direction, while absorbing light that vibrates perpendicular to the polarization direction, thus having dichroism. Therefore, after light, such as natural light, passes through the polarizer, the transmitted light basically becomes plane polarized light. When the polarizer rotates one circle and the light spot brightness is two strong and two dark, it is linearly polarized light; when the polarizer rotates one circle and the light spot brightness is two strong and two weak, it is elliptically polarized light; when the polarizer rotates one circle and the light spot brightness does not change, it may be non-polarized light or circularly polarized light. Various embodiments of the present application utilize linear polarizers. In one embodiment of the present application, a time-sharing polarization imaging method includes a polarization imaging process. In other embodiments, the time-sharing polarization imaging method also includes a polarization direction calibration process. The purpose of the calibration is to find the correspondence between the control image output by the liquid crystal panel controller and the polarization direction.

[0041] In one embodiment, Figure 1 As shown, the time-sharing polarization imaging method includes: S100, a polarization direction calibration process; and S200, a polarization imaging process. Typically, the polarization direction calibration process is completed before the polarization imaging process, meaning the time-sharing polarization imaging method includes both the polarization direction calibration process and the polarization imaging process. In specific applications, the polarization imaging process can be performed once, twice, or multiple times after completing the polarization direction calibration process. Alternatively, the polarization direction calibration process can be performed again after completing the polarization direction calibration process once, twice, or multiple times. Alternatively, the polarization direction calibration process can be performed before each polarization imaging process.

[0042] In one embodiment, Figure 2 and Figure 3As shown, the polarization direction calibration process includes the following steps: S110, a light source 100, a first linear polarizer 200, a liquid crystal panel 300 and a second linear polarizer 500 are placed in parallel; S120, the light source 100 emits light, which passes through the first linear polarizer 200 to form a first linear polarized light, which is incident on the liquid crystal panel 300; S130, the liquid crystal panel controller 400 controls the liquid crystal deflection direction of the liquid crystal panel 300, converts the first linear polarized light into an adjusted polarized light with a controlled polarization direction, which is incident on the second linear polarizer 500; S140, the adjusted polarized light passes through the second linear polarizer 50 0 forms a second linear polarized light, which enters the camera 600. At S150, the camera 600 captures the second linear polarized light to obtain a series of images. The darkest image is used as the first calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are at a 90-degree angle. The brightest image is used as the second calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are at a 0-degree angle. The image intermediate between the darkest and brightest values ​​is used as the third calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are at a 45-degree angle. In one embodiment, the response speed of the liquid crystal panel 300 is less than 16 milliseconds. Typically, an liquid crystal panel 300 with a response speed less than 16 milliseconds is considered a high-speed liquid crystal panel 300, or a high-speed liquid crystal panel 300. Due to its relatively fast response speed, it can be used to improve calibration and detection efficiency. Furthermore, in one embodiment, the response speed of the liquid crystal panel 300 is less than 8 milliseconds, 5 milliseconds, or 2 milliseconds. The embodiments of the present application, by adopting the liquid crystal panel 300, are conducive to quickly calibrating a large number of control images and efficiently determining the first calibration image, the second calibration image and the third calibration image; on this premise, time-sharing polarization imaging of the object is realized, and its polarization parameters are obtained quickly and accurately, which is conducive to application in machine vision and realizing fast and accurate industrial detection and application detection, and is particularly suitable for various highly reflective or locally specific objects, as well as applications in special environments such as high temperature and smoke.

[0043] Based on structural positional considerations, in one embodiment, in step S110, the light source 100, the first linear polarizer 200, the liquid crystal panel 300, and the second linear polarizer 500 are placed in parallel. The various embodiments of the present application have limited restrictions on the light source. In one embodiment, the light source 100 is a backlight, which has the advantages of low cost, easy availability, and easy assembly of the first linear polarizer. Furthermore, in one embodiment, the light source 100 is a monochromatic light source. Furthermore, in one embodiment, the light source 100 is a single wavelength light source. In one embodiment, in step S110, the first linear polarizer 200 and the second linear polarizer 500 maintain the same linear polarization direction; or during initial setting, the first linear polarizer 200 and the second linear polarizer 500 are kept in the same linear polarization direction as much as possible, so that the first linear polarizer 200 and the second linear polarizer 500 are in a nearly parallel state, that is, the linear polarization directions of the two are in a nearly parallel state, which can also be understood as the linear polarization direction of the first linear polarizer 200 and the linear polarization direction of the second linear polarizer 500 form an angle close to 0 degrees.

[0044] Considering the impact of light on liquid crystals, in one embodiment, in step S120, the light source 100 emits light, which is transformed into first linearly polarized light by the first linear polarizer 200 and then incident on the liquid crystal panel 300. Because the positional relationship between the light source 100, the first linear polarizer 200, and the liquid crystal panel 300 is defined in the previous step, the formation of the first linearly polarized light and its effective incidence on the liquid crystal panel 300 are ensured. In each embodiment, the liquid crystal panel 300, the first linear polarizer 200, and the second linear polarizer 500 form a three-layer directional control structure.

[0045] To facilitate control of a high-speed liquid crystal panel to adjust polarized light, in one embodiment, in step S130, the liquid crystal panel controller 400 controls the liquid crystal deflection direction of the liquid crystal panel 300, converting the first linearly polarized light into regulated polarized light with a controlled polarization direction, which is incident on the second linear polarizer 500. Furthermore, the liquid crystal panel 300 is configured to deflect the incident first linearly polarized light between 0 and 90 degrees. The deflection angle of each pixel in the liquid crystal panel 300 is controlled by the pixel value written by the liquid crystal panel controller 400. A pixel value of 0 to 255 corresponds to a deflection angle of 0 to 90 degrees, and vice versa, a deflection angle of 90 to 0 degrees. Specifically, due to the inherent nonlinearity of the liquid crystal panel, the relationship between its controlled variable, i.e., the pixel value, and the actual deflection angle is not necessarily strictly linear, so calibration is required to accurately determine this relationship. In one embodiment, in step S130, the LCD panel controller 400 writes a control image to the LCD panel 300, and the LCD panel 300 displays the control image, thereby indirectly controlling the deflection direction of the liquid crystal in the LCD panel 300. In one embodiment, in step S110, the first linear polarizer 200 and the second linear polarizer 500 maintain the same linear polarization direction; and in step S130, the LCD panel controller 400 writes a control image to the LCD panel 300, and the LCD panel 300 displays the control image, thereby indirectly controlling the deflection direction of the liquid crystal in the LCD panel 300. The remaining embodiments are similar and are not further described.

[0046] To further facilitate controlling the high-speed LCD panel to adjust polarized light, in one embodiment, in step S130, the pixels of the control image all have identical pixel values; that is, the pixel values ​​of each pixel are identically set, that is, the R, G, and B values ​​of the pixels of the control image are identically set. For example, for a certain control image, the pixel values ​​of each color of each pixel are EE or 66, such as the pixel values ​​of the pixels are #EEEEEE or #666666. In one embodiment, in step S130, the LCD panel controller 400 sequentially writes the control image V[n] to the LCD panel 300, where n is an integer from 0 to m, and the R, G, and B values ​​of the pixels of the control image V[n] are all n; where m is a preset natural number greater than 10. Furthermore, in step S130, the LCD panel controller 400 sequentially writes the control image V[n] to the LCD panel 300, where n is an integer from 0 to 255, and the R, G, and B values ​​of the pixels of the control image V[n] are all n, that is, m is 255. In other embodiments, m may be 99, 100, 200, 300 or other natural numbers.

[0047] Taking a specific number as an example, in one embodiment, in step S130, the LCD panel controller 400 sequentially writes a control image V[n] to the LCD panel 300, where n is an integer from 0 to 255, and the R, G, and B values ​​of the pixels of the control image V[n] are all n; that is, during the polarization direction calibration process, the LCD panel controller 400 writes 256 control images to the LCD panel 300, and the camera 600 respectively captures the second linear polarized light to obtain a series of 256 images as polarization images for calibration. According to the accuracy requirements, in other embodiments, n is an integer from 0 to 63 or 127, that is, during the polarization direction calibration process, the LCD panel controller 400 writes 64 or 128 control images to the LCD panel 300; or, n is an integer from 0 to 511, 1023, 2047 or 65535, that is, during the polarization direction calibration process, the LCD panel controller 400 writes 512, 1024, 2048 or 65536 control images to the LCD panel 300. The remaining embodiments are similar and will not be elaborated on.

[0048] In one embodiment, in step S130, the liquid crystal panel 300 converts the first linear polarized light into adjusted polarized light based on the control image, that is, after the first linear polarized light is incident on the liquid crystal panel 300, it is deflected under the action of the liquid crystal to obtain adjusted polarized light that conforms to the polarization direction. In one embodiment, in step S130, the control images have the same shape and / or size. In one embodiment, the control image can be an ellipse, a circle, a triangle, a pentagon, a hexagon or a rectangle, etc. In one embodiment, the control image is a 16:9 rectangle with a resolution of 1920*1080 or 1600*900. In other embodiments, the control image can be a rectangle of other sizes. Such a design is conducive to making full use of the shape characteristics of the conventional liquid crystal panel 300 without the need for additional customization of a special liquid crystal panel 300.

[0049] In one embodiment, in step S140, the adjusted polarized light passes through the second linear polarizer 500 to form second linear polarized light, which is incident on the camera 600. During the polarization direction calibration process, each time the adjusted polarized light passes through the second linear polarizer 500 to form second linear polarized light, which is incident on the camera 600, the number of times the LCD panel controller 400 controls the liquid crystal deflection direction of the LCD panel 300, i.e., the number of times the first linear polarized light is converted into adjusted polarized light with controlled polarization direction, the same number of times second linear polarized light is formed, and the second linear polarized light is incident on the camera 600. Furthermore, the LCD panel 300 remains stationary during each step, i.e., during each step of the polarization direction calibration process and the polarization imaging process, the LCD panel 300 remains stationary, or during the polarization direction calibration process and / or the polarization imaging process, the light source 100, the first linear polarizer 200, the LCD panel 300, the second linear polarizer 500, and the camera 600 all remain stationary. This design adjusts the intensity of the polarized light by adjusting the polarized light after passing through the liquid crystal panel 300, while the liquid crystal panel 300 remains stationary during this process, thereby overcoming the problems of low precision and low efficiency caused by the traditional time-sharing polarization imaging system that uses rotating polarizers to collect images.

[0050] In one embodiment, in step S150, the camera 600 captures the second linear polarized light to obtain a series of images, namely, polarization images for calibration, and the darkest image is used as the first calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are in a state of 90 degrees, that is, they are orthogonal, that is, the linear polarization directions of the first linear polarizer 200 and the second linear polarizer 500 are orthogonal; the brightest image is used as the second calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are in a state of 0 degrees. The first linear polarizer 200 and the second linear polarizer 500 are parallel to each other; an image intermediate between the darkest image and the brightest image is used as the third calibration image to show that the first linear polarizer 200 and the second linear polarizer 500 are at a 45-degree angle. The image intermediate between the first and second calibration images is used as the third calibration image. If there are two images intermediate between the first and second calibration images, one of them is selected as the third calibration image. In other words, in a series of images, assuming that the darkest image is the yth image and the brightest image is the y+80th image, the y+y+80 / 2=y+40th image is used as the third calibration image. Assuming the brightest image is the y+81th image, the y+40th image or the y+41th image is used as the third calibration image. Alternatively, if the average brightness value of the darkest image and the brightest image is 1, the images y+1 to y+79th are traversed, and the image with the brightness value closest to 1 is used as the third calibration image. The remaining embodiments are similar and are not described in detail here.

[0051] In one embodiment, Figure 4 and Figure 5As shown, the polarization imaging process includes the following steps: S220, the light source 100 emits light, which passes through the first linear polarizer 200 to form a first linear polarized light, which is incident on the liquid crystal panel 300; S230, the liquid crystal panel controller 400 controls the liquid crystal panel 300 to display a calibration image, and the liquid crystal panel 300 converts the first linear polarized light into an adjusted polarized light based on the calibration image, which is incident on the object 700; S240, the object 700 generates reflected light or transmitted light for the adjusted polarized light, which is incident on the second linear polarizer 500 to form a second linear polarized light; generally, the adjusted polarized light is incident on the object 700 from above, and the object 700 is sensitive to the adjusted polarized light. Generate reflected light; for the translucent object 700, adjust the polarized light and enter the object 700 from below, so that the object 700 generates transmitted light for the adjusted polarized light; S250, the second linearly polarized light enters the camera 600, and the camera 600 captures a polarization image corresponding to the second linearly polarized light of the calibration image; S260, determine whether the polarization images have been captured for the three calibration images corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees, and 0 degrees; otherwise, continue to step S230; S270, calculate the polarization parameter of each pixel of the object 700 based on the three polarization images. Further, in step S270, the polarization parameter of the object 700 is calculated based on the three polarization images; further, the polarization parameter is an array that reflects information about each pixel of the object 700 in the image of the camera 600, and the information is used as the polarization parameter.

[0052] In one embodiment, before step S220, the time-sharing polarization imaging method further includes step S210, where the light source 100, the first linear polarizer 200 and the liquid crystal panel 300 are placed in parallel. Figure 6 or Figure 7As shown, the polarization imaging process includes the following steps: S210, the light source 100, the first linear polarizer 200 and the liquid crystal panel 300 are placed in parallel; S220, the light source 100 emits light, which is formed into a first linear polarized light through the first linear polarizer 200 and is incident on the liquid crystal panel 300; S230, the liquid crystal panel controller 400 controls the liquid crystal panel 300 to display a calibration image, and the liquid crystal panel 300 converts the first linear polarized light into an adjusted polarized light based on the calibration image, and the adjusted polarized light is incident on the object 700; S240, the object 700 generates reflected light for the adjusted polarized light. The second linear polarized light is incident on the second linear polarizer 500 to form a second linear polarized light. At step S250, the second linear polarized light is incident on the camera 600, and the camera 600 captures a polarization image corresponding to the second linear polarized light of the calibration image. At step S260, it is determined whether the polarization images have been captured for the three calibration images corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees, and 0 degrees. If not, the process continues with step S230. At step S270, the polarization parameter of each pixel of the object 700 is calculated based on the three polarization images. The remaining embodiments are similar and are not described in detail here.

[0053] In one embodiment, in step S220, the light source 100 emits light, which passes through the first linear polarizer 200 to form first linear polarized light, which is incident on the liquid crystal panel 300; this step S220 is similar to step S120 of the polarization direction calibration process, and both emit the first linear polarized light to be incident on the liquid crystal panel 300.

[0054] In one embodiment, in step S230, the LCD panel controller 400 controls the LCD panel 300 to display a calibration image. Based on the calibration image, the LCD panel 300 converts the first linearly polarized light into adjusted polarized light, which is incident on the object 700. This step S230 uses calibration images from the polarization direction calibration process, including the first calibration image, the second calibration image, and the third calibration image. In one embodiment, in step S230, the LCD panel controller 400 controls the LCD panel 300 to display a calibration image in a preset order or a random order.

[0055] In one embodiment, in step S240, the object 700 generates reflected light or transmitted light in response to the adjusted polarized light, which is incident on the second linear polarizer 500 to form second linear polarized light; the object 700 can remain motionless and passively receive the adjusted polarized light, which is then reflected to form reflected light. Since the reflected light is generated by polarized light, the reflected light has the polarization state as described above.

[0056] In one embodiment, in step S250, the second linearly polarized light is incident on the camera 600, and the camera 600 captures a polarization image corresponding to the second linearly polarized light of the calibration image; step S250 is similar to step S150 of the polarization direction calibration process, except that there is only one polarization image and it is generated in response to the previous calibration image after being reflected by the object 700, thereby presenting the polarization characteristics of the object 700.

[0057] In one embodiment, in step S260, it is determined whether the polarization images have been captured for the three calibration images corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees, and 0 degrees. If not, step S230 is continued. In specific applications, the determination can be made using a mark recognition method, a read completion method, or an existing execution order. Further, in step S230, the LCD panel controller 400 writes the first calibration image, the second calibration image, and the third calibration image to the LCD panel 300, respectively, corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees, and 0 degrees, respectively, converting the first linear polarized light into regulated polarized light with a controlled polarization direction, which is incident on the object 700. In step S260, the camera 600 captures the first polarization image, the second polarization image, and the third polarization image of the second linear polarized light corresponding to the first calibration image, the second calibration image, and the third calibration image, respectively.

[0058] In one embodiment, in step S270, the polarization parameters of the object 700 at each pixel are calculated based on the three polarization images. In one embodiment, in step S270, the polarization parameters of the object 700 are calculated based on the three polarization images using the Stokes equation.

[0059] Furthermore, after step S270, the time-sharing polarization imaging method further includes step S280, using the polarization parameters to identify the object 700. In one embodiment, Figure 8As shown, the polarization imaging process includes the following steps: S210, the light source 100, the first linear polarizer 200 and the liquid crystal panel 300 are placed in parallel; S220, the light source 100 emits light, which is formed into a first linear polarized light through the first linear polarizer 200 and is incident on the liquid crystal panel 300; S230, the liquid crystal panel controller 400 controls the liquid crystal panel 300 to display a calibration image, and the liquid crystal panel 300 converts the first linear polarized light into an adjusted polarized light based on the calibration image, and the adjusted polarized light is incident on the object 700; S240, the object 700 generates reflected light or transmitted light for the adjusted polarized light, which is incident on the second The linear polarizer 500 forms a second linear polarized light; S250, the second linear polarized light is incident on the camera 600, and the camera 600 captures a polarization image corresponding to the second linear polarized light of the calibration image; S260, determining whether the three calibration images corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees and 0 degrees have all been captured to obtain the polarization image, otherwise continuing to execute step S230; S270, based on the three polarization images, calculating the polarization parameters of the object 700 at each pixel point; S280, using the polarization parameters to identify the object 700.

[0060] Furthermore, after step S280, the time-sharing polarization imaging method further includes step S290, adjusting the environmental parameters of the object 700 according to the polarization parameters. Figure 9As shown, the polarization imaging process includes the following steps: S220, the light source 100 emits light, which is incident on the liquid crystal panel 300 by forming a first linear polarized light through the first linear polarizer 200; S230, the liquid crystal panel controller 400 controls the liquid crystal panel 300 to display a calibration image, and the liquid crystal panel 300 converts the first linear polarized light into an adjusted polarized light based on the calibration image, and the adjusted polarized light is incident on the object 700; S240, the object 700 generates reflected light or transmitted light for the adjusted polarized light, which is incident on the second linear polarizer 500 to form a second linear polarized light; S250, the second linear polarized light is incident The camera 600 captures a polarization image corresponding to the second linear polarization light of the calibration image. At step S260, it is determined whether the polarization images have been captured for the three calibration images corresponding to the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees, and 0 degrees. Otherwise, the process continues with step S230. At step S270, a polarization parameter of each pixel of the object 700 is calculated based on the three polarization images. At step S280, the object 700 is identified using the polarization parameter. At step S290, environmental parameters of the object 700 are adjusted based on the polarization parameter. Environmental parameters include, but are not limited to, the direction of the object 700 relative to other measurement devices, the location of the object 700, the brightness of the environment in which the object 700 is located, and any reprocessing requirements for the object 700.

[0061] In a specific application embodiment, the time-sharing polarization imaging method includes a polarization direction calibration process and a polarization imaging process, and the polarization direction calibration process includes the steps of:

[0062] Step 1: In a dark room, place the backlight source, the first linear polarizer, the liquid crystal panel, and the second linear polarizer in parallel, with the first linear polarizer and the second linear polarizer in the same direction.

[0063] Step 2: The LCD panel controller, such as a computer, writes a control image V[n] to the LCD panel. Its pixel values ​​are all identical, indirectly controlling the deflection direction of the LCD, thereby producing polarized light with a controllable polarization angle range of 0 to 90 degrees. The camera captures the corresponding image Image[n].

[0064] Step 3. Repeat Step 2 with n = 0, 1, ..., 255 to obtain a series of images. In the image sequence Image[n], the darkest and lightest images correspond to the first and second linear polarizers being orthogonal (90 degrees) and parallel (0 degrees), respectively. The intermediate value between the brightest and darkest corresponds to the state of 45 degrees. The corresponding control images are denoted as: V_0, V_45, V_90.

[0065] The polarization imaging process comprises the following steps:

[0066] Step 1: Light passes through the first linear polarizer and irradiates the liquid crystal panel, generating linearly polarized light that irradiates the liquid crystal panel.

[0067] Step 2: The LCD panel controller outputs the calibration image V[n] obtained by the above polarization direction calibration process, where n is 0, 45, and 90, respectively, to control the polarization direction of the linearly polarized light.

[0068] Step 3: The polarized light is irradiated on the surface of the object and modulated by the polarization characteristics of the surface of the object, which will modulate the incident light, produce a polarization angle θ, and then reflect or transmit it out.

[0069] Step 4: The reflected light is filtered by the second linear polarizer and enters the camera to obtain the image Image[n].

[0070] Step 5. Repeat steps 2 to 4 to obtain polarization images I_0, I_45, I_90 under 0-degree, 45-degree, and 90-degree polarized light illumination. Substitute them into the Stokes equation to obtain its various parameters.

[0071] Specifically, for linearly polarized light, the Stokes vector is:

[0072] S0(x,y)=I0(x,y)+I 90 (x, y)

[0073] S1(x, y)=I0(x, y)-I 90 (x, y)

[0074] S2(x, y)=2I 45 (x, y)-S0(x, y)

[0075] Among them, I0, I 45 , I 90 They represent the image light intensity obtained by the polarizer at 0 degrees, 45 degrees and 90 degrees respectively; S0 represents the total light intensity, and S1 and S2 represent the linearly polarized light components.

[0076] The degree of polarization DoP of the object 700 is:

[0077] DoP is the ratio of the intensity of polarized light in a beam to the total light intensity.

[0078] The polarization angle AoP of the object 700 is:

[0079] In one embodiment, a time-sharing polarization imaging system is implemented based on the time-sharing polarization imaging method described in any embodiment. Specifically, the time-sharing polarization imaging system is implemented using the time-sharing polarization imaging method described in any embodiment. In one embodiment, the time-sharing polarization imaging system includes functional modules corresponding to each step of the time-sharing polarization imaging method to achieve the corresponding functions.

[0080] In one embodiment, a time-sharing polarization imaging system such as Figure 3 and Figure 5 As shown, it includes: a light source 100, a first linear polarizer 200, a liquid crystal panel 300, a liquid crystal panel controller 400, a second linear polarizer 500, a camera 600 and an analysis module; the analysis module can be provided separately or integrated with the liquid crystal panel controller 400. The light source 100, the first linear polarizer 200 and the liquid crystal panel 300 are placed in parallel, the liquid crystal panel controller 400 is connected to the liquid crystal panel 300, and the camera 600 is adjacent to the second linear polarizer 500; the light source 100 is used to emit light, which forms a first linear polarized light through the first linear polarizer 200 and is incident on the liquid crystal panel 300; the liquid crystal panel controller 400 controls the liquid crystal panel 300 to display the first linear polarizer 200 and the second linear polarizer 500 at 90 degrees, 45 degrees and 50 degrees, respectively. The LCD panel 300 is configured to use the calibration images to convert the first linearly polarized light into adjusted polarized light, which is incident on the object 700. The second linear polarizer 500 is configured to receive the reflected light from the object 700 in response to the adjusted polarized light, forming second linear polarized light that is incident on the camera 600. The camera 600 captures three polarization images corresponding to the second linear polarized light of the three calibration images. The analysis module calculates the polarization parameters of the object 700 based on the three polarization images. Furthermore, in each embodiment, the LCD panel 300 is configured to deflect the incident linearly polarized light from 0 to 90 degrees, with the deflection angle of each pixel being controlled by the pixel value written by the LCD panel controller 400. A pixel value from 0 to 255 corresponds to a deflection angle from 0 to 90 degrees, and vice versa, from 90 to 0 degrees.

[0081] Furthermore, in one embodiment, the analysis module is connected to the LCD panel controller 400 or is integrated into the LCD panel controller 400. This design, based on a high-speed LCD panel as a controllable polarized light generator, replaces mechanical moving parts. Since no transmission parts are required, it avoids the accuracy and efficiency issues caused by the traditional time-sharing polarization imaging system that uses rotating polarizers to collect images. In addition, the use of time-sharing polarization imaging avoids the complex structure and high cost of simultaneous polarization imaging systems. Therefore, it has the advantages of low cost, high speed, high resolution, and strong customizability. It can also be integrated with traditional visual inspection methods and is particularly suitable for application in the field of industrial inspection.

[0082] Furthermore, industrial inspection, especially machine vision technology, usually relies on electronic imagers. In harsh environments or when the field of view contains extremely bright areas or special hot spots, there may be misalignment problems. The misalignment problems caused by these special conditions can be overcome by combining the time-sharing polarization imaging system described in each embodiment of the present application. In one embodiment, an industrial inspection device includes a control device and the time-sharing polarization imaging system described in any embodiment connected to the control device. The industrial inspection device uses the time-sharing polarization imaging system to achieve machine vision functions or improve machine vision effects, including but not limited to eliminating hot spots to achieve uniform lighting effects, enhancing contrast to present surface details, and evaluating stress to control product strength. Specifically, the machine vision system of the industrial inspection device, such as the time-sharing polarization imaging system, is based on a high-speed liquid crystal panel as a controllable polarized light generator, replacing mechanical moving parts, and has the advantages of low cost, high speed, high resolution, and strong customizability. It can also be integrated with traditional visual inspection methods and is particularly suitable for application in the field of industrial inspection.

[0083] It should be noted that other embodiments of the present application also include time-sharing polarization imaging methods and systems, and industrial detection devices that can be implemented by combining the technical features in the above embodiments.

[0084] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-described embodiments only express several implementation methods of the present application. The descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. Therefore, the scope of patent protection of the present application shall be based on the attached claims.

Claims

1. A time-sharing polarization imaging method, characterized in that: The method comprises a polarization imaging process, wherein the polarization imaging process comprises the steps of: S220, the light source (100) emits light, which passes through the first linear polarizer (200) to form first linear polarized light, which is incident on the liquid crystal panel (300); S230, the liquid crystal panel controller (400) controls the liquid crystal panel (300) to display a calibration image, and the liquid crystal panel (300) converts the first linearly polarized light into adjusted polarized light based on the calibration image, and the light is incident on the object (700); S240, the photographed object (700) generates reflected light or transmitted light in response to the adjusted polarized light, which is incident on the second linear polarizer (500) to form second linear polarized light; S250, the second linearly polarized light is incident on a camera (600), and the camera (600) captures a polarization image corresponding to the second linearly polarized light of the calibration image; S260, determining whether the polarization images have been obtained by capturing the three calibration images corresponding to the first linear polarizer (200) and the second linear polarizer (500) at 90 degrees, 45 degrees, and 0 degrees, and otherwise continuing to execute step S230; S270, calculating and obtaining the polarization parameter of the photographed object (700) at each pixel point based on the three polarization images; Furthermore, during the polarization imaging process, the light source (100), the first linear polarizer (200), the liquid crystal panel (300), the second linear polarizer (500), and the camera (600) all remain stationary.

2. The time-sharing polarization imaging method according to claim 1, characterized in that: Before the polarization imaging process, the time-sharing polarization imaging method further includes a polarization direction calibration process; The polarization direction calibration process includes the following steps: S110, the light source (100), the first linear polarizer (200), the liquid crystal panel (300), and the second linear polarizer (500) are placed in parallel; S120, the light source (100) emits light, which passes through the first linear polarizer (200) to form first linear polarized light, which is incident on the liquid crystal panel (300); S130, the liquid crystal panel controller (400) controls the liquid crystal deflection direction of the liquid crystal panel (300), converts the first linear polarized light into regulated polarized light with a controlled polarization direction, and makes the light incident on the second linear polarizer (500); S140, the adjusted polarized light passes through the second linear polarizer (500) to form second linear polarized light, which is incident on the camera (600); S150, the camera (600) captures the second linear polarized light to obtain a series of images, the darkest image being used as a first calibration image to present a state where the first linear polarizer (200) and the second linear polarizer (500) are at 90 degrees, the brightest image being used as a second calibration image to present a state where the first linear polarizer (200) and the second linear polarizer (500) are at 0 degrees, and an image intermediate between the darkest and brightest values ​​being used as a third calibration image to present a state where the first linear polarizer (200) and the second linear polarizer (500) are at 45 degrees; Furthermore, during the polarization direction calibration process, the light source (100), the first linear polarizer (200), the liquid crystal panel (300), the second linear polarizer (500), and the camera (600) all remain stationary.

3. The time-sharing polarization imaging method according to claim 2, characterized in that: In step S110, the first linear polarizer (200) and the second linear polarizer (500) maintain the same linear polarization direction; and / or, In step S130, the liquid crystal panel controller (400) writes a control image into the liquid crystal panel (300) and the liquid crystal panel (300) displays the control image, so as to indirectly control the liquid crystal deflection direction of the liquid crystal panel (300).

4. The time-sharing polarization imaging method according to claim 3, characterized in that: In step S130, the pixels of the control image all have the same pixel value; and / or, The control images have the same shape and / or size.

5. The time-sharing polarization imaging method according to claim 4, characterized in that: The liquid crystal panel (300) converts the first linearly polarized light into adjusted polarized light based on the control image.

6. The time-sharing polarization imaging method according to claim 1, characterized in that: The response speed of the liquid crystal panel (300) is less than 16 milliseconds; and / or, The light source (100) is a backlight source.

7. The time-sharing polarization imaging method according to claim 1, characterized in that: In step S230, the liquid crystal panel controller (400) controls the liquid crystal panel (300) to display a calibration image in a preset order or a random order; and / or, In step S270, the polarization parameters of the object (700) are calculated based on the three polarization images using the Stokes equation.

8. The time-sharing polarization imaging method according to any one of claims 1 to 7, characterized in that: Before step S220, the time-sharing polarization imaging method further includes step S210, where the light source (100), the first linear polarizer (200), and the liquid crystal panel (300) are placed in parallel.

9. A time-sharing polarization imaging system, characterized in that: include: A light source (100), a first linear polarizer (200), a liquid crystal panel (300), a liquid crystal panel controller (400), a second linear polarizer (500), a camera (600), and an analysis module; The light source (100), the first linear polarizer (200), and the liquid crystal panel (300) are placed in parallel, the liquid crystal panel controller (400) is connected to the liquid crystal panel (300), and the camera (600) is adjacent to the second linear polarizer (500); The light source (100) is used to emit light, which passes through the first linear polarizer (200) to form first linear polarized light, and is incident on the liquid crystal panel (300); The liquid crystal panel controller (400) controls the liquid crystal panel (300) to display three calibration images in which the first linear polarizer (200) and the second linear polarizer (500) are at 90 degrees, 45 degrees, and 0 degrees, respectively. The liquid crystal panel (300) is used to convert the first linear polarized light into adjusted polarized light using the calibration images, and to inject the adjusted polarized light into the object (700). The second linear polarizer (500) is used to receive the reflected light generated by the photographed object (700) in response to the adjusted polarized light, forming second linear polarized light incident on the camera (600), and the camera (600) respectively captures three polarized images corresponding to the second linear polarized light of the three calibration images; The analysis module calculates the polarization parameters of the photographed object (700) based on the three polarization images; The light source (100), the first linear polarizer (200), the liquid crystal panel (300), the second linear polarizer (500) and the camera (600) all remain stationary.

10. An industrial detection device, characterized in that: The invention comprises a control device and the time-sharing polarization imaging system as claimed in claim 9 connected to the control device.

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