Adaptive lighting method and device based on multi-polarization and hybrid coded lighting mode

Abstract

The present invention discloses an adaptive lighting method and device based on multi-polarization and hybrid coding lighting modes. The present invention is based on a circular LED linear polarization light source with four polarizations, and the light intensity of each polarization angle can be individually controlled in real time; the present invention first determines the image intensity of the target area under the initial parameter configuration, and then obtains the contribution ratio of each channel light beam to the image intensity of the target area, calculates and solves the optimal value, determines the optimal lighting parameter configuration of each channel, and finally controls the output of the light source with the optimized parameter encoding to achieve adaptive removal of high light reflections and uniform lighting. The method of the present invention has a simple optical path structure and is easy to use. While providing multi-polarization lighting, it adds a hybrid coding adaptive lighting mode, which overcomes the limitation of needing mechanical rotation to find the optimal lighting angle; the present invention can quickly and adaptively achieve the effect of removing high light reflections while maintaining uniform lighting of the target area, thereby obtaining better detection results.

Description

Technical Field

[0001] The present invention belongs to the technical field of polarized illumination in optical detection, and specifically relates to an adaptive illumination method and device based on multi-polarization and hybrid coded illumination modes. Background Art

[0002] With the continuous development of processing and manufacturing technology, the requirements for workpiece detection accuracy are becoming increasingly higher. As a non-contact and rapid detection method, optical detection technology has been widely used in aerospace, military, medical equipment, energy, and automotive manufacturing. In optical detection, for non-transparent objects, reflective light sources are usually used for illumination. However, when using an optical system with reflective lighting to measure the surface, it is often encountered that the surface of the object generates mirror-reflected light, causing the photosensitive element to be overexposed, resulting in incomplete images, insufficient contrast, and affecting the accuracy of the results. Therefore, removing mirror-reflected light and improving image contrast during the detection process are crucial to achieving higher measurement accuracy in optical detection.

[0003] Currently, researchers have developed methods and devices using polarization technology to improve illumination and ultimately enhance detection results by using polarized light illumination and adding polarizers to lenses for filtering. However, existing polarized illumination methods are limited by the single polarization type of the light source and the need to mechanically rotate the polarizer to find the optimal angle to eliminate specular reflections. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention aims to provide an adaptive illumination method and device based on multi-polarization and hybrid coded illumination modes for use in optical detection. This method has a simple optical path structure and is easy to use. It combines multi-polarization illumination with a hybrid coded adaptive illumination mode, overcoming the limitation of mechanical rotation to find the optimal illumination angle. Results demonstrate that the present invention can rapidly and adaptively remove high light reflections while maintaining uniform illumination of the target area, thereby achieving better detection results. The device and method of the present invention are widely applicable in optical imaging and detection, and can also be applied to scenarios such as biological sample illumination and object type identification illumination.

[0005] The device of the present invention is a circular LED linearly polarized light source with four polarization angles. The light intensity of each polarization angle can be independently controlled in real time. The basic steps of the method of the present invention include: determining the image intensity of the target area under the initial parameter configuration; obtaining the contribution ratio of each channel light beam to the target area image intensity; calculating and solving the optimal value to determine the optimal lighting parameter configuration for each channel; encoding the optimized parameters to control the light source output, achieving adaptive high light reflection removal and uniform illumination. The inventive objectives are achieved through the following technical solutions.

[0006] An adaptive lighting method based on multi-polarization and hybrid coded lighting modes is implemented using a circular LED linearly polarized light source with four polarizations. In the circular LED linearly polarized light source, four light sources with different linear polarization angles are arranged around the center of the circle at certain angle intervals. These groups are repeated several times, and light sources with the same polarization angle channel are symmetrically distributed to form a 360-degree circular light source surface. At the same time, the light beam intensity of each polarization angle can be independently controlled in real time. Based on the difference in the contribution of light beams with different polarization states to the image intensity of the target area and the linear relationship between the output beam intensity of the LED light source and the high-level duration of the PWM wave signal, the method achieves adaptive de-highlighting and uniform illumination of the sample through hybrid coding control of the multi-polarization beam intensity. The specific steps are as follows:

[0007] (1) In the initial state, that is, when the LED light sources of the four different polarization angle channels are all driven by PWM waves with the same frequency and duty cycle, an image A of the illuminated target area is collected to determine the image intensity of the target area illuminated by the light source under the initial parameter configuration conditions;

[0008] (2) The duty cycle of the PWM wave of the LED light source of each polarization angle channel is reduced by d%, 100>d>0, while the PWM wave of the other channels remains at the initial state. Images B1, B2, B3, and B4 of the illuminated area of ​​each polarization angle channel under the corresponding conditions are collected.

[0009] (3) Converting image A obtained in step (1) and images B1, B2, B3, and B4 obtained in step (2) into the HSV domain, and counting the number of pixels OE, OE1, OE2, OE3, and OE4 of the corresponding images whose V channel values ​​exceed the threshold; and counting the number of pixels max, max1, max2, max3, and max4 of images A, B1, B2, B3, and B4 whose V channel values ​​exceed 1.35 times the threshold;

[0010] (4) Subtract the V channel values ​​corresponding to images B1, B2, B3, and B4 from those in Figure A to obtain four values: diff_th1, diff_th2, diff_th3, and diff_th4. Divide the differences by OE to obtain the contribution ratios α1, α2, α3, and α4 of the four channel beams to the target area image intensity exceeding the threshold.

[0011] (5) Subtract the number of pixels whose V channel values ​​of images B1, B2, B3, and B4 exceed 1.35 times the threshold from that of Figure A to obtain four values: diff_max1, diff_max2, diff_max3, and diff_max4. Divide the difference by max to obtain the contribution ratios θ1, θ2, θ3, and θ4 of the four channel beams to the pixels whose image intensity in the target area exceeds 1.35 times the threshold;

[0012] (6) Substitute the contribution ratios α1 to α4 of the four channel beams to the target area image intensity exceeding the threshold and the contribution ratios θ1 to θ4 of the four channel beams to the pixel points where the target area image intensity exceeds 1.35 times the threshold into the multivariate linear equation to jointly find the optimal solution:

[0013]

[0014] Calculate and solve the optimal solution coefficients M1, M2, M3 and M4 corresponding to four channels with different polarization angles;

[0015] (7) Combining the initial state PWM wave parameters in step (1) and the reduced duty cycle d% in step (2), the optimal solution coefficients M1 to M4 are converted into the optimized PWM wave frequency and duty cycle parameters of the corresponding polarization angle channel, and sent to the light source to realize the coded control output to adaptively remove high light reflections and uniform illumination.

[0016] M1~M4 correspond to the multiples of the previous reduction of d%, which is converted into the corresponding value for the total high-level duration. Taking the 0° channel as an example, the initial 1KHz PWM wave, when the duty cycle is reduced by d%, corresponds to d%*M1*0.001=1 / f*duty. According to the situation, it can be converted to the frequency f and duty cycle duty value that meet this formula, and these two values ​​can be directly sent to the light source to realize the coded control output.

[0017] In the present invention, the quad-polarized annular LED linear polarization light source has four linear polarization angles of 0°, 45°, 90° and 135°.

[0018] In the present invention, in the four-polarization annular LED linear polarization light source, light sources with four linear polarization angles are sequentially arranged around the center of the circle at intervals of 22.5°, and repeated in four groups.

[0019] The present invention also provides an adaptive lighting device based on a multi-polarization and hybrid coded lighting mode for the above method, which includes an annular LED linearly polarized light source with four polarizations, and the annular LED linearly polarized light source includes an LED light source module and an LED driver module; wherein the LED light source module includes light sources with four linear polarization angles, and the light sources with different linear polarization angles are arranged around the center of a circle at the same angle interval, repeated in several groups, and the light sources in the same polarization angle channel are symmetrically distributed to form a 360-degree annular light source surface, and the light intensity of each polarization angle is independently controllable; the LED driver module is composed of an FPGA circuit and integrated on a printed circuit board (PCB) of the LED light source module, and the LED light source module and the LED driver module are connected. The LED driver module receives external configuration parameters in real time through a UART serial port protocol, and outputs a pulse width modulation (PWM) wave with a corresponding frequency and duty cycle to drive the light source of the corresponding polarization angle channel, thereby realizing real-time regulation of the light sources with different linear polarization angles in the LED light source module.

[0020] In this invention, the annular LED linearly polarized light source operates in constant current mode, with PWM waves controlling its on / off and operating duration. It also features a Universal Asynchronous Receiver / Transmitter (UART) serial port asynchronous communication capability, allowing it to receive externally configured parameters in real time and adjust the light source's output accordingly.

[0021] In the present invention, the annular LED linearly polarized light source can simultaneously output a variety of linearly polarized light beams with known polarization angles and intensities. Each light source point of the annular LED linearly polarized light source, that is, a light source group with the same polarization angle, has the same parameters and can be driven and controlled individually. The contribution of each LED light source point to the intensity reflected into the image detector pixel is inconsistent.

[0022] The present invention combines multi-polarized illumination with hybrid coded adaptive illumination, and uses electronic control to quickly remove high light reflections while maintaining uniform illumination. Compared with the prior art, the present invention has the following advantages:

[0023] The present invention adopts a multi-polarization annular LED linear polarization light source, and takes advantage of the physical characteristics that light sources with different polarization angles contribute inconsistently to the reflected light intensity of the illuminated target surface. By adding hybrid coded adaptive lighting while multi-polarization illumination, the invention uses electronic control to quickly remove high light reflections while maintaining uniform illumination, thereby obtaining better detection results.

[0024] The method of the present invention has a simple optical path structure and is easy to use. While providing multi-polarization illumination, it adds a hybrid-coded adaptive illumination mode, overcoming the limitations of existing polarized illumination methods in which the light source has a single polarization type and a mechanically rotating polarizer is required to find the optimal angle to remove specular reflected light. It provides a simple and feasible polarized illumination method and device for conveniently and quickly removing high light reflections in optical detection and improving the accuracy of detection results. The application of the method of the present invention can realize fast adaptive polarized uniform illumination, and ultimately achieve better measurement results.

[0025] The present invention can use an annular LED linear polarization light source with four or more polarization angles to achieve adaptive lighting. The more polarization angles there are, the higher the degree of controllability and the better the adaptive lighting accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a multi-polarized annular LED lighting device.

[0027] Figure 2 This is a diagram of the polarization state detection results of the multi-polarization annular LED lighting device.

[0028] Figure 3 This is a brief introduction to the experimental system of the embodiment.

[0029] Figure 4 It is a flow chart of the adaptive lighting method based on multi-polarization and hybrid coded lighting modes of the present invention.

[0030] Figure 5 is a V channel intensity diagram of the target HSV domain in the initial state of the experimental system of the embodiment.

[0031] Figure 6 3 is a V-channel intensity diagram of the target HSV domain under the condition that the experimental system of the embodiment reduces the intensity of each polarization channel respectively.

[0032] Figure 7 is a V channel intensity map of the target HSV domain after adaptive illumination of the experimental system of the embodiment.

[0033] Figure 8 It is a target three-dimensional depth map restored by the experimental system of the embodiment from the image in the initial state and the image after adaptive illumination.

[0034] Figure 9 3D depth map of the sample in the embodiment measured under the Keyence VHX-5000 ultra-depth microscope. DETAILED DESCRIPTION

[0035] The following examples specifically describe the implementation of the adaptive illumination method and device based on multiple polarization and illumination modes of the present invention. To verify the effectiveness of the present invention, we conducted the following experimental verification in conjunction with a light field microscopy system. The specific implementation of the solution will be further described below with reference to the accompanying drawings.

[0036] like Figure 1 As shown, the multi-polarization annular LED linear polarization light source includes an LED light source module and an LED driver module; the LED light source module has four linear polarization angles of 0°, 45°, 90° and 135°, which are arranged in sequence around the center of a circle at intervals of 22.5°, repeated in four groups to form a 360° annular light source surface, and the light intensity of the light source at each polarization angle is independently controllable; the LED driver module is composed of an FPGA circuit and integrated on the LED light source PCB. It can receive external configuration parameters in real time through the UART serial port protocol, and output a PWM wave with the corresponding frequency and duty cycle to drive the light source of the corresponding polarization angle channel, realizing real-time regulation of the light source.

[0037] After the light source is made, its control and polarization state are verified. The results are as follows: Figure 2 As shown, it can be seen that the designed light source has achieved the designed function and effect.

[0038] Based on the above multi-polarized annular LED light source, the experiment was conducted in combination with the light field microscopy system. In a specific embodiment, the experimental system is set up as follows Figure 3 As shown in Figure 1, the experimental system consists of a multi-polarized annular LED illumination system, a light-field microscopy optical system, an image acquisition unit (a standard CCD or CMOS camera with an arbitrary-angle linear polarizer integrated in front of the lens), and a computer control unit (a standard computer). The multi-polarized annular LED illuminates the sample, and light reflected from the sample surface passes through the light-field microscopy system and converges onto the image acquisition unit. The computer control unit is also connected to the image acquisition unit, receiving image data for image processing and sending commands via the UART serial port to control the light output.

[0039] The specific operation steps of the adaptive lighting method based on multi-polarization and hybrid coding lighting mode of the present invention are as follows: Figure 4 ):

[0040] (1) In the initial state, that is, when the LED light source of each polarization angle channel is driven by a PWM wave with the same frequency and duty cycle, the image A of the illuminated target area is collected (see Figure 5 );

[0041] (2) The duty cycle of the PWM wave of the LED light source of a single polarization channel is reduced by d%, and the PWM waves of other channels are kept at the initial state. The images of the illumination area under the corresponding conditions are collected: B1 (when the duty cycle is reduced by 0°), B2 (when the duty cycle is reduced by 45°), B3 (when the duty cycle is reduced by 90°), and B4 (when the duty cycle is reduced by 135°) (see Figure 6 );

[0042] (3) Convert the images A, B1, B2, B3, and B4 obtained in steps (1) and (2) to the HSV domain, and count the number of pixels OE(image A), OE1(image B1), OE2(image B2), OE3(image B3), and OE4(image B4) whose V channel values ​​of the corresponding images exceed the threshold value; and count the number of pixels max(image A), max1(image B1), max2(image B2), max3(image B3), and max4(image B4) whose V channel values ​​of the corresponding images exceed 1.35 times the threshold value;

[0043] (4) Subtract the V channel values ​​corresponding to B1 to B4 from those in Figure A to obtain four values: diff_th1 to diff_th4. Divide the differences by OE to obtain the contribution ratios of the four channel beams to the target area image intensity exceeding the threshold, α1 (0° channel), α2 (45° channel), α3 (90° channel), and α4 (135° channel).

[0044] (5) Subtract the number of pixels in the V channels corresponding to B1 to B4 that exceed 1.35 times the threshold from that in Figure A to obtain four values: diff_max1 to diff_max4. Divide the difference by max to obtain the contribution ratios of the four channel beams to the pixels in the target area whose image intensity exceeds 1.35 times the threshold: θ1 (0° channel), θ2 (45° channel), θ3 (90° channel), and θ4 (135° channel).

[0045] (6) Substitute the contribution ratios α1 to α4 corresponding to the four polarization channels and the contribution ratios θ1, θ2, θ3, and θ4 corresponding to the pixels whose image intensity in the target area exceeds 1.35 times the threshold into the following multivariate linear equation to jointly find the optimal solution:

[0046]

[0047] Calculate and solve the optimal solution coefficients M1, M2, M3 and M4 corresponding to each channel;

[0048] (VII) Convert M1 to M4 into corresponding PWM wave parameters, encode the optimized parameters to control the light source output, and achieve adaptive removal of high light reflection and uniform illumination. Figure 7 The image results shown;

[0049] (8) Perform three-dimensional restoration on the image data before and after adaptive optimization, and obtain the three-dimensional depth map of the sample. Figure 8 As shown;

[0050] (IX) To further verify the accuracy of the system, the samples were observed using a Keyence VHX-5000 ultra-depth microscope. The results are as follows: Figure 9 shown.

[0051] The final experimental system is as follows Figure 8 The three-dimensional imaging test results shown and Figure 9 The test results of the commercial equipment shown in the embodiment show that the method and device of the present invention can achieve fast adaptive polarization uniform illumination, and ultimately achieve better measurement results.

Claims

1. An adaptive lighting method based on multi-polarization and hybrid coded lighting mode, characterized in that: It is achieved using a circular LED linearly polarized light source with four polarizations. In the circular LED linearly polarized light source, four light sources with different linear polarization angles are arranged around the center of the circle at certain angle intervals. These are repeated several times, and the light sources with the same polarization angle channels are symmetrically distributed to form a 360-degree circular light source surface. At the same time, the light intensity of each polarization angle can be individually controlled in real time. Based on the difference in the contribution of light beams with different polarization states to the image intensity of the target area and the linear relationship between the output beam intensity of the LED light source and the high-level duration of the PWM wave signal, it achieves adaptive de-highlighting and uniform illumination of the sample through hybrid coding control of the multi-polarization beam intensity. The specific steps are as follows: (1) In the initial state, that is, when the LED light sources of the four different polarization angle channels are all driven by PWM waves with the same frequency and duty cycle, an image A of the illuminated target area is collected to determine the image intensity of the target area illuminated by the light source under the initial parameter configuration conditions; (2) The duty cycle of the PWM wave of the LED light source of each polarization angle channel is reduced by d%, 100>d>0, while the PWM wave of the other channels remains at the initial state. Images B1, B2, B3, and B4 of the illuminated area of ​​each polarization angle channel under the corresponding conditions are collected. (3) Converting image A obtained in step (1) and images B1, B2, B3, and B4 obtained in step (2) into the HSV domain, and counting the number of pixels OE, OE1, OE2, OE3, and OE4 of the corresponding images whose V channel values ​​exceed the threshold; and counting the number of pixels max, max1, max2, max3, and max4 of images A, B1, B2, B3, and B4 whose V channel values ​​exceed 1.35 times the threshold; (4) Subtract the V channel values ​​corresponding to images B1, B2, B3, and B4 from those in Figure A to obtain four values: diff_th1, diff_th2, diff_th3, and diff_th4. Divide the differences by OE to obtain the contribution ratios α1, α2, α3, and α4 of the four channel beams to the target area image intensity exceeding the threshold. (5) Subtract the number of pixels whose V channel values ​​of images B1, B2, B3, and B4 exceed 1.35 times the threshold from that of Figure A to obtain four values: diff_max1, diff_max2, diff_max3, and diff_max4. Divide the difference by max to obtain the contribution ratios θ1, θ2, θ3, and θ4 of the four channel beams to the pixels whose image intensity in the target area exceeds 1.35 times the threshold; (6) Substitute the contribution ratios α1 to α4 of the four channel beams to the target area image intensity exceeding the threshold and the contribution ratios θ1 to θ4 of the four channel beams to the pixel points where the target area image intensity exceeds 1.35 times the threshold into the multivariate linear equation to jointly find the optimal solution: Calculate and solve the optimal solution coefficients M1, M2, M3 and M4 corresponding to four channels with different polarization angles; (7) Combining the initial state PWM wave parameters in step (1) and the reduced duty cycle d% in step (2), the optimal solution coefficients M1 to M4 are converted into the optimized PWM wave frequency and duty cycle parameters of the corresponding polarization angle channel, and sent to the light source to realize the coded control output to adaptively remove high light reflections and uniform illumination.

2. The adaptive lighting method based on multi-polarization and hybrid coded lighting mode according to claim 1, characterized in that: The four-polarization annular LED linear polarization light source has four linear polarization angles of 0°, 45°, 90° and 135°.

3. The adaptive lighting method based on multi-polarization and hybrid coded lighting mode according to claim 1, characterized in that: In the four-polarization circular LED linear polarization light source, light sources with four linear polarization angles are arranged in sequence around the center of the circle at intervals of 22.5°, and repeated in 4 groups.

4. An adaptive lighting device based on multi-polarization and hybrid coded lighting mode for use in the method of claim 1, characterized in that: It includes a circular LED linearly polarized light source with four polarizations, which includes an LED light source module and an LED driver module. The LED light source module includes light sources with four linear polarization angles. Light sources with different linear polarization angles are arranged around the center of a circle at the same angle intervals, repeated in several groups. Light sources in the same polarization angle channel are symmetrically distributed to form a 360-degree circular light source surface. At the same time, the light beam intensity of each polarization angle is individually controllable. The LED driver module is composed of an FPGA circuit and integrated on the printed circuit board (PCB) of the LED light source module. The LED light source module and the LED driver module are connected. The LED driver module receives external configuration parameters in real time through the UART serial port protocol, and outputs a pulse width modulation (PWM) wave with the corresponding frequency and duty cycle to drive the light source of the corresponding polarization angle channel, thereby realizing real-time control of the light sources with different linear polarization angles in the LED light source module.

5. The adaptive lighting device based on multi-polarization and hybrid coded lighting mode according to claim 4, characterized in that: The four-polarization annular LED linear polarization light source has four linear polarization angles of 0°, 45°, 90° and 135°.

6. The device of the adaptive lighting method based on multi-polarization and hybrid coded lighting mode according to claim 4, characterized in that: The light sources of four different linear polarization angle channels are arranged around the center of the circle at intervals of 22.5°, and repeated in four groups.

Images