A standard light source color box and detection method

Abstract

The application discloses a standard light source color matching box and a detection method, which comprises a box body, a closed detection space is formed in the box body, a placing table is arranged in the box body, and a neutral gray coating is arranged on the inner wall of the box body; a multi-light source system is arranged on the inner side of the top of the box body and is used for providing a plurality of standard light source environments; a camera acquisition module is arranged on the inner side of the top of the box body and is used for acquiring image data of a sample to be detected placed on the placing table; an image processing unit is electrically connected with the camera acquisition module and is used for color calibration, color difference calculation and analysis processing of the acquired image; and a control panel is arranged on the outer side of the box body and is used for controlling switching of the multi-light source system and acquisition parameters of the camera acquisition module. Compared with the prior art, the application can replace the human eye with machine vision to completely eliminate the influence of subjective factors, has good consistency and high repeatability of detection results, and meets the detection requirements of different industries and standards.

Description

Technical Field

[0001] This invention relates to the technical field of color detection equipment, and in particular to the technical field of a standard light source color matching box and detection method. Background Technology

[0002] Standard light source color matching boxes are commonly used equipment in the field of color detection. Their main function is to provide a unified and standardized light source environment, enabling inspectors to perform color comparisons under the same lighting conditions, thereby eliminating the influence of different light source environments on color judgment.

[0003] The standard light source color matching light box with application (patent) number CN201721731118.7 has a tray rotatably connected inside the box. A drive mechanism inside the box drives the tray to rotate horizontally. During product testing, the product is placed on the tray, and the drive mechanism rotates the tray horizontally during observation, causing the product to rotate with the tray. During rotation, different parts of the product move to the front of the box, facilitating testing from multiple locations and reducing obstruction from the side walls of the box, thus improving testing efficiency. However, this color matching light box relies on human visual color comparison. Differences in color sensitivity, experience, and judgment standards among different testers lead to poor consistency and repeatability of test results. Prolonged color comparison can easily cause visual fatigue for testers, further reducing testing accuracy.

[0004] A standard light source colorimetric observation box with application (patent) number CN201610123958.9 includes a digital camera mounted on the top of the observation cavity and a substrate facing the camera at the bottom. When the digital camera is positioned in the middle of the top of the observation cavity, its lens faces directly downwards, and the substrate is either the bottom plate of the box or a plate parallel to the bottom plate. When the digital camera is positioned in the middle of the top of the observation cavity near the opening, its lens is angled at an angle to the bottom plate, and the substrate is angled at an angle to the bottom plate and faces the camera. During testing, the object to be tested is placed on the substrate. The test involves uniformly illuminating the sample from above with a standard light source and acquiring the color data of the sample through a digital camera positioned directly above the substrate. The color difference between the standard sample and the batch sample is then directly compared using computer calculations, eliminating the human influence of visual observation. This method yields more accurate and reliable results than visual observation. However, the specification only describes the computer calculations that directly compare the color difference between the standard sample and the batch sample without disclosing the specific testing method. Those skilled in the art cannot reproduce this technical solution based on the description in the specification. Therefore, the inventor conducted in-depth research to address the shortcomings of the prior art, resulting in this invention. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the prior art by proposing a standard light source color matching box and detection method that can use machine vision to replace human eye judgment, completely eliminate the influence of subjective factors, and achieve good consistency and high repeatability of detection results; thus meeting the detection needs of different industries and standards.

[0006] To achieve the above objectives, this invention proposes a standard light source color matching box, comprising: a box body forming a closed detection space inside the box body; a platform inside the box body; and a neutral gray coating on the inner wall of the box body; a multi-light source system installed on the inner top of the box body to provide multiple standard light source environments; a camera acquisition module installed on the inner top of the box body to acquire image data of the sample to be tested placed on the platform; an image processing unit electrically connected to the camera acquisition module to perform color calibration, color difference calculation, and analysis on the acquired images; and a control panel installed on the outer side of the box body to control the switching of the multi-light source system and the acquisition parameters of the camera acquisition module.

[0007] Preferably, the multi-light source system includes a ring-shaped fluorescent tube for providing a D65 standard daylight source; an LED yellow-white light mixed module for providing an A light source and a TL84 store light source; a red-green-blue light mixed module for providing an adjustable color temperature RGB mixed light source; a tubular metal halide lamp for providing a Horizon daylight source; and LED UVA light beads for providing an ultraviolet fluorescent source.

[0008] Preferably, the camera acquisition module includes a high-resolution industrial camera with a resolution of no less than 12 million pixels; an autofocus lens that supports both manual and automatic focus adjustment; a polarizing filter to eliminate reflections on the sample surface; and an angle adjustment mechanism that can adjust the shooting angle within the range of 0°-45°.

[0009] Preferably, the image processing unit includes a color calibration module for color calibration of images captured by the camera based on a standard color chart, and for establishing a conversion matrix from RGB to Lab color space; a color difference calculation module for calculating the CIEΔE color difference between the sample to be tested and the standard sample; a metamerism analysis module for analyzing the metamerism index of the sample under different light sources; and a data storage module for storing detection results and historical data.

[0010] Preferably, the LED yellow and white light mixed-lay module uses an LED lamp bead matrix arrangement with a color temperature of 2700K-6500K, and continuous color temperature adjustment is achieved by adjusting the brightness ratio of lamp beads with different color temperatures.

[0011] As a preferred option, the red, green and blue LED mixed-lay module uses independently driven red, green and blue three-channel LEDs, and the brightness of each channel can be adjusted independently to achieve the simulation of any spectrum.

[0012] Preferably, the color calibration module is calibrated using a 24-color standard color chart.

[0013] Preferably, it also includes a wireless communication module that supports WiFi and Bluetooth connectivity, which can upload detection data to the cloud or mobile terminal.

[0014] A method for detecting a color box using a standard light source as described above includes the following steps: S1: System calibration: Images are acquired using a 24-color standard color chart under various standard light sources. A color conversion matrix from RGB to Lab is established using a multiple linear regression algorithm to complete system calibration; S2: Sample placement: The sample to be tested and the standard sample are placed simultaneously at designated positions on the stage, ensuring the samples are flat and wrinkle-free; S3: Light source selection: The appropriate standard light source is selected according to the detection requirements; S4: Image acquisition: The camera automatically focuses and acquires high-definition images of the sample to be tested and the standard sample. Multiple exposures are automatically performed and synthesized during the acquisition process to ensure the dynamic range of the image; S5: Color analysis: The image processing unit preprocesses the acquired images, performs color space conversion, extracts the region of interest, and calculates the color difference parameters between the sample to be tested and the standard sample; S6: Metamerism detection: The metamerism detection mode is selected, and the system automatically sequentially activates D65, A, and TL84. Images are acquired and color parameters are calculated for RGB, Horizontal daylight, and ultraviolet fluorescence, respectively, and the metamerism index and evaluation results are given. S7: Results output, displaying the detection results, including color parameters and color difference data, and generating a detection report.

[0015] The beneficial effects of this invention are as follows: First, it uses machine vision to replace human eye judgment, completely eliminating the influence of subjective factors, resulting in good consistency and high repeatability of test results; Second, it integrates multiple standard light sources, supports multiple color difference formula calculations and metamerism analysis, meeting the testing needs of different industries and standards; Third, all test results are automatically stored, supporting historical data query, statistical analysis and report generation, facilitating quality management.

[0016] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is an exploded view of the structure of a standard light source color matching box according to the present invention.

[0018] In the diagram: 1-box, 2-switch, 3-control panel, 4-camera acquisition module, 5-ring fluorescent tube, 6-LED yellow and white light mixed-lay module, 7-red, green and blue light mixed-lay module, 8-tubular metal halide lamp, 9-storage platform, 10-LED UVA light bead. Detailed Implementation

[0019] See Figure 1This invention discloses a standard light source color matching box, comprising a box body 1, the interior of which forms a closed detection space, a platform 9 inside the box body 1, and a neutral gray coating on the inner wall of the box body 1; a multi-light source system installed on the inner top of the box body 1 to provide multiple standard light source environments; a camera acquisition module 4 installed on the inner top of the box body 1 to acquire image data of the sample to be tested placed on the platform 9; an image processing unit electrically connected to the camera acquisition module 4 to perform color calibration, color difference calculation, and analysis on the acquired images; and a control panel 3 installed on the outer side of the box body 1 to control the switching of the multi-light source system and the acquisition parameters of the camera acquisition module 4.

[0020] The enclosure 1 also includes: a switch 2 for controlling the power supply of the equipment; and a light-shielding door for sealing the detection space and isolating it from external light interference. The multi-light source system includes a ring-shaped fluorescent tube 5, using a standard D65 fluorescent tube with a color temperature of 6500K and a color rendering index Ra≥95, used to simulate northern sunlight; and an LED warm white light mixed-lay module 6, which uses a matrix arrangement of 2700K warm white and 6500K cool white LED beads, and independently adjusts the brightness of the two color temperature beads through PWM dimming technology, and can continuously simulate commonly used commercial light sources such as A light source 2700K, TL84 light source 4000K, CWF light source 4150K, and U30 light source 3000K. The store's light source includes: a red, green, and blue LED mixed-lay module 7, which uses high color rendering LEDs with wavelengths of 620nm red, 525nm green, and 450nm blue, driven independently by three channels, allowing for the simulation of arbitrary spectral distributions by adjusting the brightness ratio of each channel, and supporting custom light source settings; a tubular metal halide lamp 8, which uses Horizon's dedicated metal halide lamp tube with a color temperature of 2300K, used to simulate horizontal sunlight during sunrise and sunset; and an LEDUVA LED bead 10, which uses ultraviolet LEDs with a peak wavelength of 365nm, used to detect fluorescent substances.

[0021] The camera acquisition module 4 includes a high-resolution industrial camera with a resolution of no less than 12 million pixels; an autofocus lens that supports both manual and automatic focus adjustment; a polarizing filter, which uses a rotatable linear polarizing mirror to effectively eliminate specular reflections on smooth sample surfaces and improve the accuracy of color detection; and an angle adjustment mechanism that can adjust the shooting angle within the range of 0°-45°.

[0022] The image processing unit includes a color calibration module for color calibration of images captured by the camera based on a standard color chart, establishing a conversion matrix from RGB to Lab color space; a color difference calculation module for calculating the CIEΔE color difference between the test sample and the standard sample; a metamerism analysis module for analyzing the metamerism index of the sample under different light sources; and a data storage module for storing test results and historical data, calibrated using an X-Rite 24-color standard color chart, and establishing a conversion matrix from camera RGB values ​​to CIELab color space using a multiple linear regression algorithm. The color difference calculation module supports the calculation of various color difference formulas such as CIE1976ΔEab, CIE1994ΔE94, CIE2000ΔE00, and CMC1:c. The metamerism analysis module can automatically acquire sample images under multiple light sources, calculate the metamerism index (MI), and evaluate the color consistency of the sample under different light sources. It also includes a wireless communication module that supports WiFi and Bluetooth connectivity, allowing detection data to be uploaded to the cloud or mobile devices.

[0023] A method for testing a color box using a standard light source includes the following steps: S1: System calibration: Images are acquired using a 24-color standard color chart under various standard light sources. A color conversion matrix from RGB to Lab is established using a multiple linear regression algorithm to complete system calibration; S2: Sample placement: The sample to be tested and the standard sample are placed simultaneously at designated positions on the stage, ensuring the samples are flat and wrinkle-free; S3: Light source selection: The appropriate standard light source is selected according to the testing requirements; S4: Image acquisition: The camera automatically focuses and acquires high-definition images of the sample to be tested and the standard sample. Multiple exposures are automatically performed and synthesized during the acquisition process to ensure the dynamic range of the image; S5: Color analysis: The image processing unit preprocesses the acquired images (denoising, white balance adjustment), performs color space conversion, extracts the region of interest, and calculates the color difference parameters between the sample to be tested and the standard sample; S6: Metamerism detection: The metamerism detection mode is selected, and the system automatically sequentially activates D65, A, and TL84. Multiple light sources are used to acquire images and calculate color parameters, ultimately providing the metamerism index and evaluation results; S7: Result output, displaying the detection results, including color parameters and color difference data, and generating a detection report.

[0024] Example 1: The chamber 1 is welded from cold-rolled steel plate, with external dimensions of 710×530×570mm and internal testing space dimensions of 600×400×400mm. The inner wall of the chamber is coated with Munsell N7 neutral gray matte paint with a reflectivity of <10%, effectively avoiding interference from ambient color reflection on the test results. The front of the chamber has an openable light-shielding door, which can be closed during testing to completely block external light. The bottom of the chamber has a shelf 9 made of frosted glass for placing the sample to be tested.

[0025] The multi-light source system is installed on the inner side of the top of the enclosure and includes: a ring fluorescent tube 5: using two F20T12 / D65 standard fluorescent tubes, with a color temperature of 6500K, a color rendering index Ra=98, and a total power of 40W, used to simulate northern sunlight; an LED yellow-white light mixed-lay module 6: using 96 2700K warm white LEDs and 96 6500K cool white LEDs, packaged in SMD 3528, arranged in a matrix, with two independent PWM dimming channels and a dimming accuracy of 12 bits, enabling continuous color temperature adjustment from 2700K to 6500K; a red-green-blue light mixed-lay module 7: using 64 red LEDs (620nm), 64 green LEDs (525nm), and 64 blue LEDs (450nm), driven independently by three channels, capable of simulating arbitrary spectral distributions; and an LED UVA light bead 10: using 12 365nm ultraviolet LEDs, with a total power of 6W, used for fluorescence detection.

[0026] The camera acquisition module 4 is installed at the top center of the housing and includes: an industrial camera: using a SONY IMX258 CMOS sensor, 12 megapixels, supporting RAW12 format output.

[0027] Lens: It uses an 8mm fixed-focus industrial lens with a large F2.0 aperture and supports autofocus.

[0028] Polarizing filter: A CPL circular polarizing filter is used, and the polarization angle can be adjusted by rotation.

[0029] Adjustment mechanism: Supports forward, backward, left and right translation and ±45° angle adjustment.

[0030] The image processing unit uses an ARM Cortex-A72 quad-core processor with a main frequency of 1.8GHz, is equipped with 4GB DDR4 memory and 32GB eMMC storage, runs an embedded Linux operating system, and has a built-in professional color processing algorithm library.

[0031] The control panel 3 uses a seven-inch high-definition touch screen with a resolution of 1024×600, and together with physical buttons, it realizes functions such as light source switching, parameter setting, and result display.

[0032] The working process of this embodiment 1 is as follows: System calibration: When using for the first time or for periodic calibration, place the X-Rite 24-color standard color chart in the center of the platform, turn on each standard light source in sequence, and the camera captures the color chart image under each light source. The image processing unit calculates the RGB to Lab color conversion matrix under each light source through a multivariate linear regression algorithm and stores it in the system. Sample testing: Place the sample to be tested and the standard sample flat on the platform, close the light shield, select the detection light source (e.g., D65) and color difference formula (e.g., ΔE00) on the control panel, click Start Detection, the system automatically turns on the selected light source, the camera automatically focuses and acquires images, the image processing unit extracts the region of interest of the sample and the standard sample, calculates the Lab* value and color difference, and the results are displayed on the screen in real time; Metamerism detection: Select the metamerism detection mode, and the system will automatically turn on multiple light sources such as D65, A, and TL84 in sequence to acquire images and calculate color parameters, and finally give the metamerism index and evaluation results. Data Management: Test results are automatically stored and can be queried by date, batch, and sample number. It supports exporting Excel or PDF reports and can upload data to the enterprise quality management system via WiFi.

[0033] Example 2 Based on Example 1, this example adds a multispectral imaging function. The camera acquisition module adopts a 5-channel multispectral camera, covering the visible light range of 400nm-700nm, with a spectral resolution of 10nm, which can acquire richer spectral information, further improve the color detection accuracy, and support reflectance curve measurement and color formula prediction functions.

[0034] Example 3 Specific steps for metamerism detection mode: 1. System Initialization and Calibration: S1. The system automatically detects whether calibration has been completed. If not, it prompts the user to insert a 24-color standard color chart. S2. The system automatically turns on multiple preset light sources in sequence, including D65 standard daylight source, A source incandescent lamp, and TL84 source cool white light. S3. The camera captures images of the standard color chart under each light source. S4. The image processing unit uses a multiple linear regression algorithm to calculate the conversion matrix from RGB values ​​to the CIELab color space under each light source and establishes a spectral reflectance database. 2. Sample Placement and Positioning: Place the sample to be tested and the standard sample side by side on the platform inside the box, ensuring that the sample surface is flat, without wrinkles or creases, and located in the designated area in the center of the camera's field of view. 3. Multi-source sequential illumination and image acquisition: The first light source is a measurement reference light source, such as D65: 1.1 The system automatically illuminates the D65 light source to simulate north-facing sunlight; 1.2 The camera automatically focuses and captures the sample image; 1.3 The image processing unit extracts the color feature values ​​(L∗,a∗,b∗) of the sample and the standard sample, and calculates the color difference under this light source. Second light source measurement test light source, such as light source A: 1.1 The system automatically switches to light source A to simulate household incandescent light; 1.2 Keep the camera parameters consistent and take images again; 1.3 Extract color data and calculate the color difference ΔEA under this light source; Extended light source options: As needed, the system can continue to switch to TL84, CWF or Horizon light source and repeat the above acquisition process; 4. Spectral reflectance reconstruction and analysis: Using multispectral imaging technology as described in Example 2, the acquired RGB values ​​are converted into spectral reflectance curves. Calculation: Reconstruct the spectral reflectance curves of the sample to be tested and the standard sample respectively; Compare the shape and numerical differences of the two curves. If the curves intersect or have large shape differences, it indicates a high risk of metamerism. Metamerism Index (MI) Calculation: Formula: The system calculates the change in color difference under different light sources. ; For example: ; 5. Judgment logic: MI≈ 0: indicates that the two samples have stable color performance under different light sources and are "same color and same spectrum". MI>0: the larger the value, the more serious the metamerism phenomenon is, that is, they look the same under D65 light, but change color under A light. 6. Result Output and Judgment: The control panel screen displays "Metameric Index: MI = XX". Pass / Fail Judgment: If MI < 0.5, the system judges it as Pass and the green light is on. If MI ≥ 0.5, the system judges it as Fail and the red light is on and an alarm is triggered. Report Generation: The system automatically generates a test report containing Lab values, color difference values ​​and MI index under each light source and uploads it to the cloud via WiFi.

[0035] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A standard light source color matching box, characterized in that: The system includes a housing (1) which forms a closed detection space inside the housing (1) and a platform (9) inside the housing (1). The inner wall of the housing (1) is coated with a neutral gray coating. A multi-light source system is installed on the inner side of the top of the housing (1) to provide a variety of standard light source environments. A camera acquisition module (4) is installed on the inner side of the top of the housing (1) to acquire image data of the sample to be tested placed on the platform (9). An image processing unit is electrically connected to the camera acquisition module (4) to perform color calibration, color difference calculation and analysis on the acquired images. A control panel (3) is installed on the outer side of the housing (1) to control the switching of the multi-light source system and the acquisition parameters of the camera acquisition module (4).

2. The standard light source color matching box as described in claim 1, characterized in that: The multi-light source system includes a ring fluorescent tube (5) for providing D65 standard daylight source; an LED yellow and white light mixed module (6) for providing A light source and TL84 store light source; and a red, green and blue light bead mixed module (7) for providing RGB mixed light source with adjustable color temperature. A tubular metal halide lamp (8) is used to provide a horizontal daylight source; an LED UVA lamp bead (10) is used to provide an ultraviolet fluorescent source.

3. A standard light source color matching box as described in claim 1, characterized in that: The camera acquisition module (4) includes a high-resolution industrial camera with a resolution of not less than 12 million pixels; an autofocus lens that supports manual and automatic focus adjustment; a polarizing filter for eliminating reflections on the sample surface; and an angle adjustment mechanism that can adjust the shooting angle within the range of 0°-45°.

4. A standard light source color matching box as described in claim 1, characterized in that: The image processing unit includes a color calibration module for color calibration of images captured by the camera based on a standard color chart, and for establishing a conversion matrix from RGB to Lab color space; and a color difference calculation module for calculating the CIEΔE color difference between the sample to be tested and the standard sample. Metamerism analysis module, used to analyze the metamerism index of samples under different light sources; The data storage module is used to store test results and historical data.

5. A standard light source color matching box as described in claim 2, characterized in that: The LED yellow and white light mixed-lay module (6) uses an LED lamp bead matrix arrangement with color temperatures of 2700K-6500K, and continuous color temperature adjustment is achieved by adjusting the brightness ratio of lamp beads with different color temperatures.

6. A standard light source color matching box as described in claim 2, characterized in that: The red, green and blue LED mixed-lay module (7) uses independently driven red, green and blue three-channel LEDs, and the brightness of each channel can be adjusted independently to realize the simulation of arbitrary spectrum.

7. A standard light source color matching box as described in claim 4, characterized in that: The color calibration module is calibrated using a 24-color standard color chart.

8. A standard light source color matching box as described in claim 1, characterized in that: It also includes a wireless communication module that supports WiFi and Bluetooth connectivity, allowing detection data to be uploaded to the cloud or mobile devices.

9. A method for detecting a standard light source color box as described in any one of claims 1 to 8, characterized in that: Includes the following steps: S1: System calibration. Images are acquired under various standard light sources using a 24-color standard color chart. An RGB to Lab color conversion matrix is ​​established using a multiple linear regression algorithm to complete the system calibration. S2: Place the sample. Place the sample to be tested and the standard sample at the designated position on the stage, ensuring that the sample is flat and without wrinkles. S3: Light source selection: Select the appropriate standard light source according to the testing requirements; S4: Image acquisition. The camera automatically focuses and acquires high-definition images of the sample to be tested and the standard sample. During the acquisition process, multiple exposures are automatically performed and the images are synthesized to ensure the dynamic range of the images. S5: Color analysis, the image processing unit preprocesses the acquired image, performs color space conversion, extracts the region of interest, and calculates the color difference parameter between the sample to be tested and the standard sample; S6: Metamerism Detection: Select the metamerism detection mode. The system will automatically turn on D65, A, TL84, RGB, Horizon horizontal daylight and ultraviolet fluorescence in sequence, collect images and calculate color parameters respectively, and finally give the metamerism index and evaluation results. S7: Output results, displaying the test results, including color parameters and color difference data, and generating a test report.

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