Speckle measurement method based on spectrum

Abstract

The invention provides a speckle measurement method based on a spectrum, which is used for measuring the single-dispersion speckle contrast ratio of a measured picture, and comprises the following measurement steps: S1, starting a color speckle tester and measured measurement equipment, projecting a preset measured picture by the measured measurement equipment, and preheating the equipment; s2, acquiring spectral information of a measured picture projected by the measured measuring equipment by using the spectral measuring equipment; s3, selecting a monochromatic optical filter according to the characteristic wavelength in the spectral information obtained in the step S2 by means of a wavelength-optical filter transmittance change curve; s4, configuring the optical filter selected in the step S3 into an optical path of a color speckle tester; s5, readjusting the focal length of the lens of the color speckle tester to avoid the chromatic aberration defect of the lens; s6, adjusting the integral time of the color speckle tester to prevent the collected speckle image from having an overexposure or underexposure phenomenon; and S7, collecting a speckle image of the measured picture, and calculating the single-dispersion speckle contrast of the speckle image.

Description

Technical Field

[0001] The present invention relates to the technical field of speckle measurement, and in particular to a speckle measurement method in the field of laser display. Background Art

[0002] With the rapid development of laser technology and its wide application in civilian fields such as display and lighting, the problem of laser speckle has received increasing attention. The speckle phenomenon is an interference phenomenon caused by the coherence of the laser, which occurs when the light beam is irradiated onto a rough surface or passes through an inhomogeneous medium. It manifests as randomly distributed bright and dark spots, which seriously affects the picture quality of laser display and lighting. In order to quantitatively evaluate the severity of the speckle phenomenon, academia and industry have proposed the concept of speckle contrast to describe the degree of speckle obviousness. The industry urgently needs equipment and methods that can quickly and accurately measure speckle on the production line to achieve effective control of product quality and optimization of production processes.

[0003] Although some speckle measurement devices and methods have been proposed and have achieved speckle measurement to a certain extent, the existing speckle measurement technologies generally have the problem of insufficient intelligence and cannot meet the needs of rapid measurement on production lines and large-scale applications.

[0004] Many existing speckle measurement devices require a lot of manual intervention during the measurement process. From equipment configuration and parameter adjustment before the test, to data collection during the test, and then to data processing after the test, many links require manual operation. For example, for light sources with different characteristics, it is often necessary to manually replace hardware or adjust equipment parameters. These cumbersome manual operations not only consume a lot of time and manpower, but also greatly reduce the measurement speed, making it difficult to meet the efficient and fast measurement cycle requirements of the production line, and unable to achieve large-scale automated detection.

[0005] Since different types of laser light sources (e.g. different wavelengths, different powers) and different measurement conditions (e.g. different ambient brightness, different measurement distances) have different requirements for speckle measurement equipment, existing measurement equipment often needs to be cumbersomely configured for different measurement scenarios. This configuration process usually involves the adjustment of multiple parameters, such as the selection of filters, the adjustment of lens focal length, the setting of exposure time, and so on. There is often a coupling relationship between these parameters, which requires operators to have certain professional knowledge and experience to make reasonable configurations. This not only increases the difficulty of using the equipment, but more importantly, it hinders the rapid switching between different products or batches, seriously affecting production efficiency and flexibility, and it is difficult to adapt to the diverse measurement needs of the production line.

[0006] Ideal speckle measurement equipment should be able to automatically identify the characteristics of the light source being measured, and automatically adjust the measurement parameters according to the measurement environment to obtain the best measurement results. However, existing speckle measurement equipment generally lacks such intelligent judgment and adaptive capabilities. They can often only measure according to pre-set fixed parameters and cannot be flexibly adjusted according to actual conditions. For example, it is impossible to automatically identify the spectral characteristics of the light source being measured and automatically select the appropriate filter based on this, it is impossible to automatically adjust the exposure time according to the intensity of the ambient light, and it is impossible to automatically adjust the focal length according to the distance of the object being measured, etc. This lack of intelligence makes it difficult for the equipment to adapt to the complex and changing production line environment, it is difficult to ensure the consistency and reliability of the measurement results, and it is impossible to meet the high-precision and high-standard quality control requirements.

[0007] In summary, the existing speckle measurement technology has significant deficiencies in terms of automation, convenience of configuration process, intelligent judgment and adaptive capabilities. These defects lead to cumbersome and inefficient measurement process, and the measurement results are easily affected by human factors. More importantly, it is difficult to meet the urgent needs of production lines for rapid measurement, automated detection and consistency control. Therefore, there is an urgent need to develop a speckle measurement method that is highly intelligent, can automatically identify the measurement object, automatically configure and adjust parameters, and can quickly give measurement results, so as to promote the quality improvement and rapid development of related industries such as laser display and laser lighting. Summary of the invention

[0008] In view of the problems of existing speckle measurement technology, such as insufficient intelligence, low automation, complex configuration process, lack of intelligent judgment and adaptive capabilities, and especially the problem of difficulty in meeting the needs of rapid measurement and large-scale application of production lines, the present invention provides a spectral-based speckle rapid measurement method, which realizes the intelligence and automation of the speckle measurement process, is suitable for batch, rapid and high-precision measurement in a production line environment, and improves measurement efficiency, accuracy and ease of use.

[0009] The present invention provides a spectral-based rapid speckle measurement method, the core of which is to use spectral information to guide each link of the speckle measurement process, realize intelligent and automated parameter configuration and measurement process, and thus achieve rapid measurement and production line application.

[0010] The measuring method is used to measure the monochromatic speckle contrast of the measured picture, and the measuring method comprises the following steps:

[0011] S1: Turn on the color speckle tester and the measured device under test, project the preset measured picture on the measured device under test, preheat the device, and wait for the color speckle tester and the measured device under test to stabilize;

[0012] S2: using a spectrum measuring device to obtain spectrum information of the measured picture projected by the measured device;

[0013] S3: selecting a monochromatic filter according to the characteristic wavelength in the spectral information obtained in step S2 by means of a wavelength-filter transmittance variation curve;

[0014] S4: placing the filter selected in step S3 into the optical path of the color speckle tester;

[0015] S5: re-adjusting the focal length of the lens of the color speckle tester to avoid chromatic aberration defects of the lens;

[0016] S6: adjusting the integration time of the color speckle tester to prevent the collected speckle image from being overexposed or underexposed;

[0017] S7: collecting a speckle image of the measured picture, and calculating a monochromatic speckle contrast of the speckle image.

[0018] Preferably, in step S2, the spectrum measuring device is a spectrum measuring module integrated in a color speckle tester; or, the spectrum measuring device is an external spectrum measuring instrument.

[0019] Preferably, in step S3, the characteristic wavelength is a centroid wavelength or a center wavelength.

[0020] Preferably, the centroid wavelength calculation formula is: ,in is the centroid wavelength, is the wavelength, The wavelength The central wavelength is the wavelength corresponding to the maximum spectral intensity.

[0021] Preferably, in step S4, the filter is configured by: configuring through a color filter wheel inside the color speckle tester, or by installing the filter in front of a light inlet of an imaging system of the color speckle tester.

[0022] Preferably, in step S5, the step of adjusting the focal length of the lens is: adjusting the focal length of the lens by electronic control, or adjusting the focal length of the lens by manual control.

[0023] Preferably, in the wavelength-filter transmittance variation curve, the monochromatic filters are respectively an X filter, a Y filter and a Z filter, and each of the monochromatic filters has a different transmittance at a specific wavelength, so that the monochromatic filter with the highest transmittance at the characteristic wavelength is selected according to the characteristic wavelength.

[0024] Preferably, in step S7, the calculation formula of the monochromatic speckle contrast is: ,in is the speckle contrast, is the standard deviation of the speckle image, is the average gray value of the speckle image.

[0025] Preferably, the speckle measurement method is applicable to an integrated color speckle tester integrated with a spectral measurement module, the spectral measurement module serving as the spectral measurement device, and the color speckle tester further comprising a spectroscopic system for splitting incident light into two beams of light, wherein one beam of light is used to enter the spectral measurement module for spectral measurement, and the other beam of light is used for speckle measurement.

[0026] This method matches the appropriate filter through spectral information, automatically adjusts the lens focal length and integration time, and realizes a highly intelligent and automated measurement process. It is particularly suitable for batch, fast and high-precision measurements in production line environments.

[0027] This method realizes automatic configuration and adjustment of equipment parameters and automatic control of the measurement process by integrating spectral measurement equipment, thereby improving the degree of automation, reducing manual intervention, lowering the skill requirements for operators, and can be easily integrated into an automated production line.

[0028] This method can automatically select appropriate measurement parameters according to the spectral information of the measured light source, adapt to different measurement objects and measurement environments, has strong self-adaptation ability, and ensures the consistency and reliability of measurement between different products and batches.

[0029] Through the above technical scheme, the present invention effectively solves the problem that the existing speckle measurement technology is not intelligent enough and is difficult to meet the needs of rapid measurement of production lines and large-scale applications, and realizes fast, accurate and intelligent speckle measurement, which provides strong support for product quality control and technological progress in the field of laser display, and is of great significance to improving production line yield and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of a fast speckle measurement method based on spectroscopy

[0031] Figure 2 Schematic diagram of the spectrum curve of the light source of the device under test and all filter curves DETAILED DESCRIPTION

[0032] Example 1

[0033] See also Figure 1As shown, the present invention proposes a speckle measurement method based on spectroscopy, which is applicable to an integrated color speckle tester integrated with a spectral measurement module. The color speckle tester system includes a spectroscopic system, which divides an incident light beam into two beams, one of which is used for speckle measurement, and the other is used to enter the spectral measurement module for spectral measurement. At the same time, as a color speckle tester, the color speckle tester integrates a filter switching system, such as a color filter wheel, which switches the corresponding monochromatic filter by rotating the color filter wheel to filter the light of the measured picture, so that the picture collected by the color speckle tester has only monochromatic light, thereby measuring the monochromatic speckle contrast of the speckle image.

[0034] The measurement method includes the following steps:

[0035] S1: Equipment startup and preheating. Turn on the color speckle tester and the measured device (such as a laser projector, laser display, etc.). The measured device projects a preset test screen as needed, such as a pure color screen of a specific color or grayscale. Preheat the color speckle tester and the measured device, usually for 30 minutes, to ensure that the equipment is in a stable working state and eliminate the influence of factors such as temperature on the measurement results.

[0036] S2: Spectral information acquisition. Use a spectral measurement device to obtain the spectral information of the test screen projected by the measured device under test. The spectral measurement device in this embodiment is an integrated spectral measurement device: that is, the spectral measurement module is integrated into the color speckle tester to achieve an integrated design and simplify the device connection and operation. In other embodiments, the spectral measurement device can also be an external spectral measurement device, which is connected to the host computer through a data cable (such as USB, serial port, etc.), and the spectral measurement device is controlled by the host computer program of the spectral measurement device to collect the spectrum, and the collected spectral data is transmitted to the host computer program of the color speckle tester.

[0037] The spectral information includes the light intensity distribution of the test image at different wavelengths, which is the basis for intelligent matching and parameter configuration in subsequent steps.

[0038] S3: Intelligent filter matching. With the help of the wavelength-filter transmittance change curve, a monochromatic filter is selected according to the characteristic wavelength in the spectral information obtained in step S2, and the filter that best matches the spectral characteristics of the measured light source is selected. The specific matching method is as follows:

[0039] Calculate characteristic wavelength: Calculate the characteristic wavelength of the measured light source based on the spectral information, such as the centroid wavelength or center wavelength. Centroid wavelength calculation formula: ,in is the centroid wavelength, is the wavelength, i.e. the wavelength measured in the spectral measurement device, The wavelength The corresponding spectral intensity; the central wavelength can select the wavelength corresponding to the maximum spectral intensity.

[0040] Filter selection: Based on the calculated characteristic wavelength, search the pre-established filter database and select the filter with the highest transmittance at the characteristic wavelength as the best match. The filter database contains various monochromatic filter models and their corresponding wavelength-transmittance curves. The three monochromatic filters in this embodiment are X filter, Y filter and Z filter. The wavelength-transmittance curves of the three monochromatic filters are as follows: Figure 2 As shown, Figure 2 The yellow line in the figure represents the power spectrum of the light source being measured, the red line represents the transmittance of the X filter, the green line represents the transmittance of the Y filter, and the blue line represents the transmittance of the Z filter. Figure 2 In the embodiment shown, we calculate the centroid wavelength of the measured light source to be 464.36nm through the centroid wavelength calculation formula. At a wavelength of 464.36nm, the X, Y, and Z filters all have certain transmittances, but the Z filter has the highest transmittance, so for this measured light source, we choose the Z filter to perform monochromatic speckle measurement.

[0041] S4: Configure the filter. Automatically configure the filter selected in step S3 to the optical path of the color speckle tester. In this embodiment, the color speckle tester is integrated with an electric color filter wheel. Accordingly, the filter configuration steps are: a variety of commonly used filters are installed on the color filter wheel, and the internal control system of the color speckle tester controls the rotation of the color filter wheel according to the matching result of step S3 to switch the selected filter to the optical path. In other embodiments, the filter can also be a bracket installed in front of the light inlet of the imaging system, that is, it is not integrated in the color speckle tester, and the operator manually installs the selected filter on the bracket according to the host computer program or the monochrome filter selected by the color speckle tester.

[0042] S5: Lens focusing of the color speckle tester. Since light of different wavelengths will be refracted to different degrees after passing through the lens, that is, there is chromatic aberration, which causes light of different colors to be focused at different positions. In order to eliminate the influence of chromatic aberration on speckle measurement, it is necessary to readjust the lens focal length of the color speckle tester according to the selected monochromatic filter. In this embodiment, the focusing method adopts electric control automatic focusing, and the electric focusing lens equipped with the color speckle tester is used. The internal control system of the color speckle tester automatically controls the lens to perform fine focusing according to the selected filter information, so that the imaging system can clearly image the central wavelength of the filter. Among them, the electric control focusing of the color speckle tester is a prior art and will not be repeated here. In other embodiments, manual auxiliary focusing can also be used. This focusing method is suitable for color speckle testers that are not internally matched with electric focusing lenses. The user manually performs precise focusing according to the clarity indicators (such as gradient value, contrast, etc.) of the speckle image displayed in real time on the display screen of the color speckle tester.

[0043] S6: Integration time adjustment. Adjust the integration time of the color speckle tester to ensure that the acquired speckle image has appropriate brightness and avoid overexposure or underexposure. The integration time can be adjusted according to the following principles:

[0044] Automatic adjustment strategy: The color speckle tester collects preview images in real time and calculates the average brightness of the image or the peak brightness of a specific area. If the brightness exceeds the preset target range, the integration time is automatically increased or decreased until the image brightness meets the requirements.

[0045] Histogram-assisted judgment: The user can use the histogram of the image displayed in real time by the color speckle tester to assist in judging whether the image is overexposed or underexposed, and manually adjust the integration time accordingly.

[0046] S7: Speckle image acquisition and calculation. After completing the above steps, the color speckle tester acquires a clear speckle image with appropriate brightness, and calculates the monochrome speckle contrast based on the image data. The calculation formula is: , is the standard deviation of the speckle image, is the average gray value of the speckle image.

Claims

1. A speckle measurement method based on spectroscopy, characterized in that: The measuring method is used to measure the monochromatic speckle contrast of the measured picture, and the measuring method comprises the following steps: S1: Turn on the color speckle tester and the measured device under test, project the preset measured picture on the measured device under test, preheat the device, and wait for the color speckle tester and the measured device under test to stabilize; S2: using a spectrum measuring device to obtain spectrum information of the measured picture projected by the measured device; S3: selecting a monochromatic filter according to the characteristic wavelength in the spectral information obtained in step S2 by means of a wavelength-filter transmittance variation curve; S4: placing the filter selected in step S3 into the optical path of the color speckle tester; S5: re-adjusting the focal length of the lens of the color speckle tester to avoid chromatic aberration defects of the lens; S6: adjusting the integration time of the color speckle tester to prevent the collected speckle image from being overexposed or underexposed; S7: collecting a speckle image of the measured picture, and calculating a monochromatic speckle contrast of the speckle image.

2. The speckle measurement method based on spectrum according to claim 1, characterized in that: In step S2, the spectrum measurement device is a spectrum measurement module integrated in a color speckle tester; or, the spectrum measurement device is an external spectrum measurement instrument.

3. The speckle measurement method based on spectrum according to claim 1, characterized in that: In step S3, the characteristic wavelength is a centroid wavelength or a center wavelength.

4. The speckle measurement method based on spectrum according to claim 3, characterized in that: The centroid wavelength calculation formula is: ,in is the centroid wavelength, is the wavelength, The wavelength The central wavelength is the wavelength corresponding to the maximum spectral intensity.

5. The speckle measurement method based on spectrum according to claim 1, characterized in that: In step S4, the filter is configured by: configuring through a color filter wheel inside the color speckle tester, or by installing the filter in front of a light inlet of an imaging system of the color speckle tester.

6. The speckle measurement method based on spectrum according to claim 1, characterized in that: In step S5, the step of adjusting the focal length of the lens is: adjusting the focal length of the lens by electronic control, or adjusting the focal length of the lens by manual control.

7. The method for rapid speckle measurement based on spectrum according to claim 1, characterized in that: In the wavelength-filter transmittance variation curve, the monochromatic filters are respectively an X filter, a Y filter, a Z filter, or an R filter, a G filter, and a B filter; because each monochromatic filter has a different transmittance at a specific wavelength, the monochromatic filter with the highest transmittance at the characteristic wavelength is selected according to the characteristic wavelength.

8. The speckle measurement method based on spectrum according to claim 1, characterized in that: In step S7, the calculation formula of the monochromatic speckle contrast is: ,in is the speckle contrast, is the standard deviation of the speckle image, is the average gray value of the speckle image.

9. The speckle measurement method based on spectrum according to claim 1, characterized in that: The speckle measurement method is applicable to an integrated color speckle tester integrated with a spectrum measurement module, wherein the spectrum measurement module serves as the spectrum measurement device, and the color speckle tester further comprises a spectroscopic system for splitting incident light into two beams of light, wherein one beam of light is used to enter the spectrum measurement module for spectrum measurement, and the other beam of light is used for speckle measurement.

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