CN113155845A - Light source, setting method thereof, optical detection method and system - Google Patents
Light source, setting method thereof, optical detection method and system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
- H05B47/155—Coordinated control of two or more light sources
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
- G01N2021/8835—Adjustable illumination, e.g. software adjustable screen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/061—Sources
Abstract
The invention discloses a light source and a setting method thereof, an optical detection method and a system, which are characterized in that image gray scale distribution characteristic data of a standard sample in a camera view field range are obtained; adjusting the light-emitting intensity distribution of a light source according to the image gray scale distribution characteristic data, wherein the light source is an area array light-emitting device which comprises a light-emitting unit with controllable light-emitting intensity; the method utilizes the adjusted light source to illuminate the detected product, adjusts the luminous intensity distribution of the area array illumination light source, feeds the compensated brightness distribution back to the light source to perform illumination of the compensated brightness distribution, avoids the saturation of images in a high reflection area, and simultaneously improves the image brightness in a low reflection area, thereby improving the detection precision of the detected object irradiated by the low reflection area.
Description
Technical Field
The invention belongs to the technical field of optical detection, and particularly relates to a light source, a setting method thereof, an optical detection method and a system.
Background
The device for detecting the appearance defects of the products generally comprises an illumination light source, a light source controller, an industrial camera, a lens and image analysis processing software, wherein the illumination light source is used for showing the defects on the products, and the basic principle for displaying the defects is to highlight the difference between the defect area and the normal area of the products where the defects are located in terms of human-eye-perceivable physical quantities, and the difference is generally light intensity difference and color difference.
For example, area array light emitting devices such as LCD, OLED, Mini LED, Micro LED, etc., which are mainly used for image display at present, are highly flexible and controllable light sources in terms of their own characteristics. These light emitting devices not only break through the limitation of conventional surface light sources in structural form, and can realize curved surfaces, spherical surfaces or free-form surfaces, but also show emission characteristic data, such as color and emission intensity of light emitting units can be controlled at micron level. On the one hand, these features, when used in display applications, bring about a friendly improvement in the human visual perception, allowing the user to enjoy a high quality image presentation. On the other hand, when these features are combined with an optical projection device for defect detection illumination, it is possible to generate a light field with controllable intensity and color distribution in the illumination space, and the intensity, color can be almost freely adjusted in the illumination space. These characteristics will undoubtedly bring new means for defect detection technology.
In the existing defect detection technology, the reflection intensity difference of different positions of a detected target area is large and exceeds the response dynamic range of a camera, and at the moment, the local area of a single image is under-exposed or over-exposed, so that the local information difference of the image is lost. The method of multiple exposure of the camera is usually adopted to solve the problem at present, but the method is limited by specific detection occasions, such as a product in a moving state. One form of illumination source relevant to the technology of the present invention, which is mainly structured light in stripes, is to place a transmissive template with a variable or fixed pattern in front of the light source, and the pattern on the template is illuminated on the projection plane by the light source and the projection optical system, and is mostly used for 3D contour detection. Another form is a commonly used projector or video projector for displaying a broadcast image and video, which can project a rich image on an illuminated plane, but its purpose is to display the projected image, and a feedback adjustment function is not performed according to the projected image.
Disclosure of Invention
In view of the above drawbacks and needs of the prior art, the present invention provides a light source, a method for setting the light source, an optical inspection method and a system, which improve the inspection accuracy of an inspected object illuminated by the light source by adjusting the luminous intensity distribution of the area array illumination light source.
To achieve the above object, according to one aspect of the present invention, there is provided a light source setting method including:
acquiring image gray distribution characteristic data of a standard sample in a camera view field range;
adjusting the light-emitting intensity distribution of a light source according to the image gray scale distribution characteristic data, wherein the light source is an area array light-emitting device which comprises a light-emitting unit with controllable light-emitting intensity;
and illuminating the detected product by using the adjusted light source.
As a further improvement of the present invention, adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data includes:
and if the average gray value of the image sub-region is lower than the set threshold range, the light intensity of the light-emitting unit corresponding to the image sub-region is increased, and if the average gray value of the image sub-region is higher than the set threshold range, the light intensity of the light-emitting unit corresponding to the image sub-region is decreased.
As a further improvement of the present invention, acquiring image gray scale distribution characteristic data of the standard sample in the camera view field range includes:
setting the initial luminous intensity of the luminous units to be the same, imaging or projecting the area array luminous device to the surface of the standard sample in the illumination area, and photographing the surface of the standard sample by using a camera to obtain image gray distribution characteristic data.
As a further improvement of the present invention, adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data includes:
acquiring the corresponding relation between each subarea of the image and the light-emitting unit;
acquiring deviation between the average gray value of each subregion of the image and a preset gray reference value, setting a feedback matrix according to the deviation, and adjusting the luminous intensity of the corresponding luminous unit according to the feedback matrix;
the gray reference value is a gray value when the image is in an equilibrium state, and the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-regions of the image is smaller than a first preset threshold value.
As a further improvement of the present invention, a feedback matrix is set according to the deviation, specifically:
if the deviation is a negative number and the absolute value of the deviation is greater than a second preset threshold, the luminous intensity of the luminous unit corresponding to the image subarea is enhanced proportionally according to the deviation;
if the deviation is positive and the absolute value of the deviation is greater than a second preset threshold, reducing the luminous intensity of the luminous unit corresponding to the image subarea according to the deviation in proportion;
adjusting the luminous intensity of the corresponding luminous unit according to the feedback matrix, specifically:
and updating the image gray scale distribution characteristic data of the standard sample in the camera view field range according to the adjusted luminous intensity to obtain an updated feedback matrix, and enabling the obtained image to be in a balanced state through iteration.
As a further improvement of the present invention, acquiring image gray scale distribution characteristic data of the standard sample in the camera view field range includes:
the method comprises the steps of acquiring pre-stored data, wherein the pre-stored data comprise image gray scale distribution characteristic data of a standard sample in a camera view field range, or pre-storing a feedback matrix which is obtained according to the image gray scale distribution characteristic data of the standard sample in the camera view field range and is used for adjusting the light intensity of each light-emitting unit;
the setting rule of the feedback matrix is that the light intensity of the light-emitting unit corresponding to the image sub-region is increased if the average gray value of the image sub-region is lower than the set threshold range, and the light intensity of the light-emitting unit corresponding to the image sub-region is decreased if the average gray value of the image sub-region is higher than the set threshold range.
As a further improvement of the present invention, adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data includes:
acquiring an initial feedback matrix according to pre-stored data, and setting the initial luminous intensity of a light source according to the initial feedback matrix;
updating image gray scale distribution characteristic data of the standard sample in the camera view field range according to the initial luminous intensity to obtain an updated feedback matrix;
through iteration, the obtained image is in a balanced state, the balanced state is that the average brightness value of the image reaches a preset value, and the absolute value of the brightness difference value between every two sub-regions of the image is smaller than a first preset threshold value.
As a further improvement of the present invention, the light emitted by the area array light emitting device is imaged or projected to the illumination area through the optical assembly such that each sub-area of the illumination area has an optical conjugate relationship with each light emitting unit of the area array light emitting device.
To achieve the above object, according to another aspect of the present invention, there is provided an optical inspection method including the above light source setting method, and
and the camera is used for imaging the standard sample or the product to be measured.
As a further improvement of the present invention, the method further comprises:
before acquiring image gray distribution characteristic data of a standard sample in a camera view field range, fixing adjustable parameters of a camera module;
and acquiring image gray distribution characteristic data of the standard sample in the field of view of the camera by using adjustable parameters of the fixed camera.
As a further improvement of the present invention, the method further comprises:
after the light-emitting intensity distribution of the light source is adjusted according to the image gray scale distribution characteristic data, adjusting adjustable parameters of the camera module so that the brightness of the image reflected by the standard sample is adjusted to be in an equilibrium state, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between each sub-area of the image is smaller than a first preset threshold value.
As a further improvement of the present invention, the adjustable parameters of the camera module include one or more of exposure time, aperture size and gain.
As a further improvement of the present invention, wherein,
the light source and the camera form an on-axis illumination/imaging system using an optical assembly including a beam splitter, or
An included angle is formed between the projection optical axis of the light source and the imaging optical axis of the camera, so that the imaging system images the reflected light or the transmitted light of the detected sample.
To achieve the above object, according to another aspect of the present invention, there is provided a light source, which is an area array light emitting device including a light emitting unit whose light emitting intensity is controllable,
the light source is used for illuminating a detected product, and the luminous intensity distribution of the light source is adjusted through a feedback matrix obtained according to the image gray scale distribution characteristic data of the standard sample in the camera view field range.
To achieve the above object, according to another aspect of the present invention, there is provided an optical detection system including:
the light source described above;
and the camera is used for adjusting the adjustable parameters of the camera module so as to adjust the brightness of the image reflected by the standard sample to an equilibrium state after adjusting the luminous intensity distribution of the light source according to the image gray scale distribution characteristic data, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between each sub-area of the image is smaller than a first preset threshold value.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
according to the light source, the setting method thereof, the optical detection method and the optical detection system, the luminous intensity distribution of the area array illumination light source is adjusted according to the image gray scale distribution of a detected product in the field of view of the camera, the compensated brightness distribution is fed back to the light source, and illumination of the compensated brightness distribution is carried out, so that the image achieves a gray scale uniform state. On the basis, the brightness of the image can be adjusted by adjusting the parameters of the camera. By the means, the saturation of images in a high reflection area is avoided, and the image brightness of a low reflection area is improved, so that the defects of the high reflection area and the low reflection area can be displayed simultaneously, the working principle is simple and clear, and the used unit technologies are mature, such as an imaging technology, a projection technology, a light-emitting element display technology and an image gray level analysis technology, so that the engineering realization and the product production are facilitated, and because the difference of the illumination light intensity is increased, the detection capability of a single-frame image exceeding the self dynamic range can be obtained, multiple exposures of a detected product with large contrast are not needed, the detection time is saved, the detection efficiency is improved, and the cost is reduced.
Drawings
Fig. 1 is a schematic diagram of a mapping relationship between an area array light emitting device and an illumination area according to a technical solution of the present invention;
FIG. 2 is a schematic diagram of a projected pattern of an area array light emitting device according to an embodiment of the present invention;
in all the figures, the same reference numerals denote the same features, in particular:
1-area array light emitting device, 2-imaging/projection optical assembly, 3-illumination area, 4-light emitting unit and 5-illumination sub-area.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. The present invention will be described in further detail with reference to specific embodiments.
The technical terms involved in the present invention are explained as follows:
lcos: liquid Crystal on Silicon, a Liquid Crystal on Silicon.
In one embodiment, there is provided a light source setting method, including the steps of:
acquiring image gray distribution characteristic data of a standard sample in a camera view field range; adjusting the light-emitting intensity distribution of a light source according to the image gray scale distribution characteristic data, wherein the light source is an area array light-emitting device which comprises a light-emitting unit with controllable light-emitting intensity; and illuminating the detected product by using the adjusted light source.
Specifically, the light source used in the method is an area array light emitting device, the area array light emitting device comprises light emitting units with controllable light emitting intensity, thus different light emitting units irradiate different areas corresponding to the detected product, the image gray distribution characteristic data of the standard sample in the camera view field range is obtained by photographing through a camera due to different reflection characteristic data of each area of the detected product, the image gray distribution characteristic data is the gray distribution condition corresponding to each pixel point, the image gray distribution characteristic data of the standard sample in the camera view field range can be obtained by analyzing the gray distribution condition corresponding to each pixel point in the image, the light emitting intensity distribution of the light source is adjusted through the image gray distribution characteristic data, if the average gray value of the image subarea is lower than the set threshold range, the light intensity of the light emitting unit corresponding to the image subarea is improved, and if the average gray value of the image subarea is higher than the set threshold range, reducing the light intensity of the light-emitting unit corresponding to the image subarea, and illuminating the detected product by using the adjusted light source, so that the image of the high-reflection area of the detected product can be prevented from being excessively saturated, and the image brightness of the low-reflection area can be improved, so that the defects of the high-reflection area and the low-reflection area can be simultaneously displayed.
Fig. 1 is a schematic diagram of a mapping relationship between an area array light emitting device and an illumination area according to the technical scheme of the present invention. As shown in fig. 1, the area array light emitting device 1 is composed of a plurality of light emitting units 4, the types of the area array light emitting device include Mini LED, OLED, Micro LED, Lcos, etc., each light emitting unit 4 may be a single color light emitting unit, or a combination of multi-color sub-light emitting units, such as RGB units, and the area array light emitting device can control light emission and light emission intensity independently according to the light emitting unit or the light emitting sub-unit under the driving of the driving circuit. The light emitted by the area array light-emitting device 1 is imaged or projected to the illumination area 3 through the imaging/projection optical assembly 2, the illumination sub-area 5 of the illumination area and the light-emitting unit 4 have an optical conjugate relation, the illumination intensity on the illumination sub-area is determined by the light-emitting intensity of the corresponding light-emitting unit, the detected object is placed in the illumination area, and the imaging photo of the surface of the detected object is photographed through a camera for subsequent analysis.
As a preferred embodiment, the acquiring of the image gray scale distribution characteristic data of the standard sample in the camera view field range includes: setting the initial luminous intensity of the luminous units to be the same, and photographing the surface of the standard sample by using a camera to acquire image gray scale distribution characteristic data.
Specifically, the image of the standard sample in the field of view of the camera may be obtained by photographing in advance, or may be obtained by photographing in the field, where the initial light-emitting intensity of the light-emitting units in the light source when the image is photographed may be set according to the requirement, for example, the area array light-emitting device is set to emit light uniformly, that is, the intensity of each light-emitting unit is set to be the same, and the light intensity is half of the maximum light-emitting intensity. The area array light-emitting device images or projects the image to the surface of the standard sample in the illumination area, and the image gray distribution characteristic data can be obtained by taking a picture of the surface of the standard sample by using a camera. Since the reflectance is wavelength dependent, for example, when a test object having red and blue regions is illuminated with red light of the same intensity, the red region has a higher reflectance and appears as a high gray scale (or overexposed) and the blue region appears as a low gray scale (or underexposed) in the image. For a color sample, the illumination intensity of a low gray area of the image can be increased, and the illumination intensity of a near-saturated or overexposed area of the image can be reduced, so that the gray level of the image can be balanced, and the image which can be effectively processed subsequently can be obtained.
The area array light-emitting device adopts uniform light field illumination, a camera is utilized to shoot an image of the surface of a sample (a first standard product of a product), a light-emitting unit of the area array light-emitting device corresponding to a bright area of an imaged image is dimmed, and a light-emitting unit of the area array light-emitting device corresponding to a dark area of the imaged image is brightened until the average gray scale of the imaged image is within a preset effective range (the preset effective range is a range capable of realizing effective detection of the image, such as 50% -80% of an image saturation value, corresponding to the gray scale of 128-204 in the example), because the projected light field is not uniform, it can increase the brightness of the illumination area corresponding to the area with low reflectivity, and decrease the brightness of the illumination area corresponding to the area with high reflectivity, the luminous intensity of the area array luminous device is compensated in an active mode, so that the reflection intensity of the surface of the detected object is in an effective range which can be detected.
As a preferred embodiment, adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data includes: acquiring the corresponding relation between each subarea of the image and the light-emitting unit; acquiring deviation between the average gray value of each sub-area of the image and a preset gray reference value, acquiring a feedback matrix according to the deviation, and adjusting the luminous intensity of the corresponding luminous unit according to the feedback matrix. The gray reference value is a gray value when the image is in an equilibrium state, and the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-areas of the image is smaller than a first preset threshold value.
Specifically, because a corresponding relationship exists between each sub-region of the image obtained by photographing and the light-emitting unit, an absolute value of a difference value between an average gray value of the sub-region of the image and a gray reference value is calculated, where the absolute value is greater than a first preset threshold range, that is, the average gray value of the sub-region of the image is too large or too small, the light-emitting intensity of the corresponding light-emitting unit is adjusted proportionally according to the difference value, and if the deviation is a negative number and the absolute value of the deviation is greater than a second preset threshold, it indicates that the average gray value of the sub-region of the image is small and the illumination intensity of the corresponding region needs to be improved, specifically, the light-emitting intensity of the light-emitting unit corresponding to the sub-region of the image can be enhanced proportionally, so that the gray value of the image of the low-reflection region of the detected product is improved; if the deviation is a positive number and the absolute value of the deviation is greater than the second preset threshold, it indicates that the average gray value of the image sub-region is large, and the illumination intensity of the corresponding region needs to be reduced. The gray reference value is a gray value when the image is in an equilibrium state, the equilibrium state is that an average brightness value of the image reaches a preset value and an absolute value of a brightness difference value between sub-regions of the image is smaller than a first preset threshold, as an example, effective detection of the image can be realized in the equilibrium state, for example, 50% -80% of a saturation value of the image, which corresponds to 128% -204 gray in the example.
More preferably, the adjusting process may be an iterative process, the image gray scale distribution characteristic data of the standard sample in the camera view field range is updated according to the adjusted luminous intensity to obtain an updated feedback matrix, and the obtained image is in an equilibrium state through iteration, where the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-regions of the image is smaller than a first preset threshold value.
Through the iteration, the value of the feedback matrix corresponding to the area array light-emitting device can be more accurate, so that the acquired image gray scale distribution characteristic data is more accurate, and the iteration is stopped by controlling the corresponding iteration parameters, such as the iteration times or the error of two iterations, within a preset range, so that the value of the feedback matrix corresponding to the area array light-emitting device is more accurate, and the acquired image gray scale distribution characteristic data is more accurate. For example, for a sample surface with 4 areas with different reflection coefficients, the brightest and darkest areas have the defect that the reflection coefficient is not much different from the background of the area, when the area is illuminated by an evenly distributed light field, there may be the situation that the bright area is overexposed, other areas are normal, or the dark area is underexposed and other areas are normal, by using the above method, the area array light emitting device is set to be in the setting state of even light emission, the image is analyzed, the intensity distribution feedback matrix is transmitted to the area array light emitting device, the illumination intensity of each area is adjusted (feedback compensation), the image can be shot and the illumination intensity of each area can be adjusted in a circulating manner until the illumination intensity of each area reaches the ideal state required by image processing; the feedback matrix is recorded and compensated to the area array light emitting device as a setting for detecting defects in the area for the product.
As a preferred embodiment, the acquiring of the image gray scale distribution characteristic data of the standard sample in the camera view field range may further be: the method comprises the steps of acquiring pre-stored data, wherein the pre-stored data comprise image gray scale distribution characteristic data of a standard sample in a camera view field range, or pre-storing a feedback matrix which is obtained according to the image gray scale distribution characteristic data of the standard sample in the camera view field range and is used for adjusting the light intensity of each light-emitting unit; the setting rule of the feedback matrix is that the light intensity of the light-emitting unit corresponding to the image sub-region is increased if the average gray value of the image sub-region is lower than the set threshold range, and the light intensity of the light-emitting unit corresponding to the image sub-region is decreased if the average gray value of the image sub-region is higher than the set threshold range.
Specifically, if the reflection characteristic data of each region of the surface of the standard sample for the light is known, for example, the reflection coefficient of each region of the surface of the standard sample for the light is known, the initial luminous intensity of the corresponding light-emitting unit can be set according to the reflection coefficient of each region of the surface of the standard sample for the light, specifically, if the reflection coefficient of the corresponding region is larger, the light intensity corresponding to the region is smaller, and if the reflection coefficient of the corresponding region is smaller, the light intensity corresponding to the region is increased, so that the obtained image reaches a state of initial equalization.
More preferably, the adjusting process may be an iterative process, an initial feedback matrix is obtained according to pre-stored data, and the initial luminous intensity of the light source is set according to the initial feedback matrix; updating image gray scale distribution characteristic data of the standard sample in the camera view field range according to the initial luminous intensity to obtain an updated feedback matrix; through iteration, the obtained image is in a balanced state, the balanced state is that the average brightness value of the image reaches a preset value, and the absolute value of the brightness difference value between every two sub-regions of the image is smaller than a first preset threshold value. Through iteration, the value of the feedback matrix corresponding to the area array light-emitting device can be more accurate, so that the acquired image gray scale distribution characteristic data is more accurate, and through controlling the corresponding iteration parameters, such as controlling the iteration times or stopping the iteration when the error of two iterations is within a preset range, the value of the feedback matrix corresponding to the area array light-emitting device is more accurate, so that the acquired image gray scale distribution characteristic data is more accurate.
Fig. 2 is a schematic diagram of a projection pattern of the area array light emitting device according to the technical solution of the present invention. As shown in fig. 2, the known gray scale distribution characteristic data is the reflection coefficient of the detected object, and the reflection coefficients of the detected object are respectively a: 10. b, a region: 128. and c, area: 160 and d-zone: 240, wherein when the reflection coefficient is 0, the incident light is totally absorbed and is not reflected; at a reflection coefficient of 255, there is 100% reflection of incident light. Setting the reflection coefficient interval to be 0-255 also corresponds to the gray value of the image collected by the camera to be 0-255, and the pixel gray value of the image is saturated or overexposed when the gray value exceeds 255 and underexposed when the gray value is lower than 50. Adjusting the illumination intensity of each sub-area of the illumination area according to the distribution of the reflection coefficient of the surface of the sample, for example, setting the illumination intensity of each sub-area of the illumination area as a area: 10x255, b region: 255. and c, area: 255 and d regions: 0.5 × 255, the reflection intensity (the gray value corresponding to the image captured by the camera) of each sub-area is respectively the area a: 100. b, a region: 128. and c, area: 160 and d-zone: and 120, the gray values corresponding to the defects (taking the example that the reflection coefficient is reduced by 10%) in each sub-area are respectively a area: (1-10%) 100=90, b region: (1-10%) 128=115, c region: (1-10%) 160=144 and d-block: (1-10%) 120=108, and the gray scale difference between the substrate of each sub-region and the defect is a region: 10. zone b 13, zone c:16 and d-blocks: 12. therefore, compared with the condition that the gray difference between the defect of each sub-area and the substrate is balanced to 10 gray scales, the difference of the original 1 gray scale in the area a is amplified to 10 gray scales, the defect detection of the area a is facilitated, and meanwhile, the difference between the defect of the area d and the substrate gray scale is reduced to 12, so that the defect detection is not influenced.
Compared with the prior art, when the illumination projection uniform light field with the intensity of 255 is illuminated to the surface of the measured object, the reflection intensity (gray value) of each area of the measured object is respectively an area a: 10. b, a region: 128. and c, area: 160. and d, area: 240, when the tested object has defects (taking the example that the reflection coefficient of the defects is different from the background area by 10 percent), the gray values corresponding to the defects (taking the example that the reflection coefficient is reduced by 10 percent) in each area are respectively a area a: (1-10%) 10=9, b region: (1-10%) 128=115, c region: (1-10%) 160=144, d block: (1-10%) 240=216, the difference in gray level between the substrate and the defect of each region is: a:1, b:13, c:16, d: 24. Therefore, the difference between the defect of the a-region and the substrate gray level is as small as 1 gray level compared with the b-, c-, and d-regions, and if the image noise of the camera exceeds 1 gray level, the defect of the a-region is not detected.
Correspondingly, the invention also provides an optical detection method, which comprises the light source setting method. As a preferred embodiment, a projection pattern is output to the area array light emitting device, so that the area array light emitting device emits light according to the projection pattern, and the light is projected to an illumination area where the detected object is placed through an optical system, wherein the optical system may be a coaxial illumination/imaging system formed by an optical assembly including a spectroscope, or an optical system formed in an inclined manner that an imaging optical axis and a projection optical axis form an included angle. The method comprises the steps of photographing an illumination area by using a camera, analyzing an image by using a computer, recording an underexposed area and an overexposed area, forming a feedback matrix and feeding the feedback matrix back to an area array light-emitting device, increasing the luminous intensity of the underexposed illumination area corresponding to a light-emitting unit area and reducing the luminous intensity of the overexposed illumination area corresponding to the light-emitting unit area, and photographing the surface of a detected object again by using the camera to realize the analysis of subsequent steps, such as analyzing the imaging image to realize the accurate detection of the surface defect of the detected object.
Since the image brightness is also related to the camera parameters, as another preferred embodiment, the method further comprises: before acquiring image gray scale distribution characteristic data of a standard sample in a camera view field range, fixing parameters of a camera; acquiring image gray distribution characteristic data of a standard sample in a camera view field range by using parameters of a fixed camera; after the luminous intensity distribution of the light source is adjusted according to the image gray scale distribution characteristic data, parameters of the camera are adjusted, so that the brightness of the image reflected by the standard sample is adjusted to be in an equilibrium state, the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between each sub-area of the image is smaller than a first preset threshold value, and the average brightness value of the imaged image can reach the preset value by adjusting one or more of the exposure time, the aperture size and the gain of the camera.
Corresponding to the light source setting method, the invention also provides a light source which is an area array light-emitting device, the area array light-emitting device comprises a light-emitting unit with controllable light-emitting intensity,
the light source is used for illuminating a detected product, and the light intensity distribution of the light source is adjusted according to the image gray scale distribution characteristic data by acquiring the image gray scale distribution characteristic data of the standard sample in the camera view field range. The implementation principle and technical effect of the light source are similar to those of the light source setting method, and will not be described herein.
Corresponding to the above optical detection method, the present invention also provides an optical detection system, which includes:
the light source described above;
the camera is used for taking a picture by using the fixed parameters to acquire an image of the standard sample in the camera view field range before acquiring the image gray scale distribution characteristic data of the standard sample in the camera view field range; and the parameter is adjusted to adjust the brightness of the image reflected by the standard sample to an equilibrium state after the light-emitting intensity distribution of the light source is adjusted according to the image gray scale distribution characteristic data, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between each sub-area of the image is smaller than a second preset threshold value. The implementation principle and technical effect of the system are similar to those of the optical detection method, and will not be described herein in a repeated manner.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (15)
1. A method of setting a light source, the method comprising:
acquiring image gray distribution characteristic data of a standard sample in a camera view field range;
adjusting the light-emitting intensity distribution of the light source according to the image gray scale distribution characteristic data, wherein the light source is an area array light-emitting device which comprises a light-emitting unit with controllable light-emitting intensity;
and illuminating the detected product by using the adjusted light source.
2. A light source setting method according to claim 1, wherein adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data comprises:
and if the average gray value of the image sub-region is lower than the set threshold range, the light intensity of the light-emitting unit corresponding to the image sub-region is increased, and if the average gray value of the image sub-region is higher than the set threshold range, the light intensity of the light-emitting unit corresponding to the image sub-region is decreased.
3. The light source setting method according to claim 1, wherein acquiring image gray scale distribution characteristic data of the standard sample in the camera view field range comprises:
setting the initial luminous intensity of the luminous units to be the same, imaging or projecting the area array luminous device to the surface of the standard sample in the illumination area, and photographing the surface of the standard sample by using a camera to obtain the gray distribution characteristic data of the image.
4. A light source setting method according to claim 3, wherein adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data comprises:
acquiring the corresponding relation between each subarea of the image and the light-emitting unit;
acquiring deviation between the average gray value of each sub-area of the image and a preset gray reference value, setting a feedback matrix according to the deviation, and adjusting the luminous intensity of the corresponding luminous unit according to the feedback matrix;
the gray reference value is a gray value when the image is in an equilibrium state, and the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-regions of the image is smaller than a first preset threshold value.
5. A light source setting method according to claim 4, wherein a feedback matrix is set according to the deviation, specifically:
if the deviation is a negative number and the absolute value of the deviation is greater than a second preset threshold, the luminous intensity of the luminous unit corresponding to the image subarea is proportionally enhanced according to the deviation;
if the deviation is a positive number and the absolute value of the deviation is greater than a second preset threshold, reducing the luminous intensity of the luminous unit corresponding to the image subarea according to the deviation in proportion;
adjusting the luminous intensity of the corresponding luminous unit according to the feedback matrix, specifically:
and updating the image gray scale distribution characteristic data of the standard sample in the camera view field range according to the adjusted luminous intensity to obtain an updated feedback matrix, and enabling the obtained image to be in a balanced state through iteration.
6. The light source setting method according to claim 1, wherein acquiring image gray scale distribution characteristic data of the standard sample in the camera view field range comprises:
acquiring pre-stored data, wherein the pre-stored data comprises image gray scale distribution characteristic data of the standard sample in a camera view field range, or a feedback matrix which is obtained according to the image gray scale distribution characteristic data of the standard sample in the camera view field range and is used for adjusting the light intensity of each light-emitting unit is pre-stored;
the setting rule of the feedback matrix is that the light intensity of the light-emitting unit corresponding to the image sub-region is increased when the average gray value of the image sub-region is lower than a set threshold range, and the light intensity of the light-emitting unit corresponding to the image sub-region is decreased when the average gray value of the image sub-region is higher than the set threshold range.
7. A light source setting method according to claim 6, wherein adjusting the light emission intensity distribution of the light source according to the image gradation distribution characteristic data comprises:
acquiring an initial feedback matrix according to the pre-stored data, and setting the initial luminous intensity of the light source according to the initial feedback matrix;
updating image gray scale distribution characteristic data of the standard sample in a camera view field range according to the initial luminous intensity to obtain an updated feedback matrix;
and through iteration, the obtained image is in an equilibrium state, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-regions of the image is smaller than a first preset threshold value.
8. A light source arrangement method according to claim 1, wherein the light emitted from the area array light emitting device is imaged or projected onto the illumination area by an optical assembly such that each sub-area of the illumination area has an optical conjugate relationship with each light emitting unit of the area array light emitting device.
9. An optical inspection method, characterized in that the optical inspection method comprises the light source setting method of any one of claims 1 to 8, and
and the camera is used for imaging the standard sample or the product to be detected.
10. An optical inspection method according to claim 9, wherein the method further comprises:
before acquiring image gray scale distribution characteristic data of a standard sample in a camera view field range, fixing adjustable parameters of the camera module;
and acquiring image gray distribution characteristic data of the standard sample in the field of view of the camera by using the adjustable parameters for fixing the camera.
11. An optical inspection method according to claim 9, wherein the method further comprises:
after the light-emitting intensity distribution of the light source is adjusted according to the image gray scale distribution characteristic data, adjusting adjustable parameters of the camera module to enable the brightness of the image reflected by the standard sample to be adjusted to an equilibrium state, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between the sub-regions of the image is smaller than a first preset threshold value.
12. An optical inspection method as claimed in claim 9, wherein the adjustable parameters of the camera module include one or more of exposure time, aperture size and gain.
13. An optical inspection method according to claim 9,
the light source and the camera form a coaxial illumination/imaging system using an optical assembly including a beam splitter, or
An included angle is formed between the projection optical axis of the light source and the imaging optical axis of the camera, so that the imaging system images the reflected light or the transmitted light of the detected sample.
14. A light source is characterized in that the light source is an area array light-emitting device which comprises a light-emitting unit with controllable light-emitting intensity,
the light source is used for illuminating a detected product, and the luminous intensity distribution of the light source is adjusted through a feedback matrix obtained according to image gray scale distribution characteristic data of a standard sample in a camera view field range.
15. An optical inspection system, the system comprising:
the light source of claim 14;
and the camera is used for adjusting the adjustable parameters of the camera module so as to adjust the brightness of the image reflected by the standard sample to an equilibrium state after adjusting the luminous intensity distribution of the light source according to the image gray scale distribution characteristic data, wherein the equilibrium state is that the average brightness value of the image reaches a preset value and the absolute value of the brightness difference value between each sub-area of the image is smaller than a first preset threshold value.
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