CN111316090A - Microscopic defect detection system and method for transparent or semitransparent material - Google Patents
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- 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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- 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
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
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- 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
- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
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- G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
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- G01N2021/887—Grading and classifying of flaws using sequentially two or more inspection runs, e.g. coarse and fine, or detecting then analysing the measurements made in two or more directions, angles, positions
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- G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques
Abstract
A microscopic defect detection system and method for transparent or semitransparent materials are disclosed, wherein the detection system comprises: a coherent light source (10) for emitting a coherent light beam to scan a transparent or translucent material to be inspected; the photoelectric sensor (20) is used for acquiring scattered light intensity imaging of the material to be detected; a controller (30) for acquiring the scattered light intensity image corresponding to a scanning position; carrying out Fourier transform on the scattered light intensity image to obtain a corresponding amplitude spectrum and a corresponding phase spectrum, and obtaining cut-off frequencies of the amplitude spectrum and the phase spectrum; the cut-off frequency corresponds to the scanning position and the corresponding relative acquisition position; monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range, taking the scanning position as a defect position, and determining a defect according to the defect position; the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
Description
Technical Field
The invention relates to the technical field of industrial detection, in particular to a system and a method for detecting microscopic defects of a transparent or semitransparent material.
Background
In general, in the production and manufacturing process of products, common micro defects such as bubbles, impurities, cracks, ripples, scratches, bruises and the like are difficult to avoid. For products, these surface defects can seriously affect the service performance and life of the products; scratches are one of the most easily detected and least tolerable defects for consumers. At present, the detection method for the scratch in the industrial detection field is as follows: 1. illuminating the object with low-angle monochromatic light; 2. collecting images by a CCD/CMOS; 3. the image is processed and defects are detected by image processing software. In the traditional method, due to the limitation of the current lighting hardware, the system can only detect the scratch in a certain direction, but in practical application, the direction of the scratch is uncertain, so that the detection is easy to miss and false.
In the conventional technology, a detection method using three-dimensional reconstruction based on active structured light projection is also adopted. However, when the appearance of a specific transparent or semitransparent surface is detected, because the appearance of the transparent or semitransparent surface is detected by using an optical imaging technology, a local brightness saturation region is often generated due to too strong surface reflection, so that the region cannot be subjected to defect segmentation and identification, or the image cannot obtain surface defect information due to too strong transmittance, so that the common optical three-dimensional scanning and two-dimensional imaging methods are difficult to perform microscopic defect detection on the transparent or semitransparent surface.
Disclosure of Invention
Based on the above, the invention provides a microscopic defect detection system for transparent or semitransparent materials, which aims to solve the problems that the conventional optical three-dimensional scanning and two-dimensional imaging methods are difficult to detect microscopic defects on transparent or semitransparent surfaces and have high omission factor and false detection rate.
A transparent or translucent material micro-defect detection system, comprising:
the coherent light source is used for emitting coherent light beams to scan the transparent or semitransparent material to be detected;
the photoelectric sensor is used for acquiring scattered light intensity imaging of the material to be detected, and the photoelectric sensor, the coherent light source and the material to be detected have relative acquisition positions in space, and the relative acquisition positions at least comprise scattering angles and distances to the material to be detected;
the controller is used for acquiring the scattered light intensity image corresponding to the scanning position; performing Fourier transform on the scattered light intensity image to obtain corresponding amplitude-frequency curve information and phase-frequency curve information, and obtaining cut-off frequencies of the amplitude-frequency curve information and the phase-frequency curve information; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position;
monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range, taking the scanning position as a defect position, and determining a defect according to the defect position;
the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
In one embodiment, the system further comprises a stage for carrying the test material;
the object stage also comprises orthogonal X-direction and Y-direction movement mechanisms for driving the material to be detected to move in the X direction and the Y direction for scanning;
the coherent light source and the photoelectric sensor are fixed relative to the material to be detected in the scanning process.
In one embodiment, the controller is configured to move the coherent light source and/or the photosensor to scan the material;
the controller is also used for monitoring the relative acquisition position of the photoelectric sensor relative to the coherent light source and the material to be detected, and acquiring the frequency threshold range corresponding to the relative acquisition position.
In one embodiment, the number of the photoelectric sensors is N, and N is greater than or equal to 2; the N photoelectric sensors, the coherent light source and the material to be detected have N relative acquisition positions in space.
In one embodiment, in the scanning process, for a scanning position, N relative acquisition positions correspond;
the controller is further used for monitoring N cut-off frequencies corresponding to scattered light intensity imaging acquired by N corresponding acquisition positions corresponding to the scanning positions, and if the cut-off frequencies do not belong to corresponding frequency threshold ranges, the scanning positions are recorded as defect positions.
In one embodiment, the coherent light source is a laser light source, and the material to be inspected is scanned in a line scanning manner.
In addition, in order to solve the problems that the common optical three-dimensional scanning and two-dimensional imaging methods are difficult to detect the microscopic defects of the transparent or semitransparent surface and have high omission factor and false detection rate in the traditional technology, the invention also provides a microscopic defect detection method of the transparent or semitransparent material, and the method is based on the controller.
A microscopic defect detection method for a transparent or semitransparent material comprises the following steps:
scanning the material to be detected by coherent light beams;
when scanning to a scanning position: collecting scattered light intensity imaging of the material to be detected at a relative collecting position; performing Fourier transform on the scattered light intensity image to obtain corresponding amplitude-frequency curve information and phase-frequency curve information, and obtaining cut-off frequencies of the amplitude-frequency curve information and the phase-frequency curve information;
the relative acquisition position at least comprises a scattering angle and a distance to the material to be detected; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position;
monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range, taking the scanning position as a defect position, and determining a defect according to the defect position;
the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
In one embodiment, the scan is a line scan, and the scan direction includes orthogonal X and Y directions.
In one embodiment, the number of the relative acquisition positions is N, and N is greater than or equal to 2;
the monitoring of the scanning position when the cut-off frequency does not belong to the frequency threshold range as the defect position comprises:
and for a scanning position, if a cutoff frequency does not belong to a corresponding frequency threshold range in N cutoff frequencies corresponding to scattered light intensity imaging acquired at N relative acquisition positions corresponding to the scanning position, recording the scanning position as a defect position.
In one embodiment, the determining the defect according to the defect position further includes:
checking the defects, and updating the frequency threshold range according to the checking result
The embodiment of the invention has the following beneficial effects:
the transparent or semitransparent material micro defect detection system and the transparent or semitransparent material micro defect detection method based on the controller in the system are adopted, the transparent or semitransparent material is scanned by coherent light, when the transparent or semitransparent material is scanned to a scanning position, scattered light intensity distribution is collected at a certain scattering angle and distance, the scattered light intensity distribution is compared with a reference value calculated according to Lorenz-Mich theory, the scanning position where the scattered light intensity distribution does not accord with the reference value is recorded as a defect position, and therefore after scanning is finished, the size and the type of defects in a material to be detected can be determined by integrating a set of the defect positions in the material to be detected. The system and the method are not influenced by the light transmittance of the transparent or semitransparent material to be detected because of the collected scattered light. Meanwhile, the invention compares the scattered light intensity distribution acquired in real time with the reference value calculated theoretically, so that the false detection rate and the omission factor are lower.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Wherein:
FIG. 1 is a schematic view of a microscopic defect inspection system for transparent or translucent materials in one embodiment;
FIG. 2 is a graph of the spatial scattering intensity distribution for different defect sizes with the same refractive index;
FIG. 3 is an amplitude-frequency curve and a phase-frequency curve of a scattered light intensity distribution with a refractive index of 0.56 and a defect size of 6.6um after FFT in one embodiment;
FIG. 4 is an amplitude-frequency curve and a phase-frequency curve of a scattered light intensity distribution with a refractive index of 0.56 and a defect size of 13.2um after FFT in one embodiment;
FIG. 5 is a schematic diagram of the defect detection principle in one embodiment;
FIG. 6 is a flow chart of a method for microscopic defect detection of a transparent or translucent material in one embodiment.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the problems that the common optical three-dimensional scanning and two-dimensional imaging methods are difficult to detect the microscopic defects of the transparent or semitransparent surface and have high omission factor and false detection rate in the traditional technology, as shown in fig. 1, the invention provides a microscopic defect detection system for a transparent or semitransparent material, which comprises: a coherent light source 10, a photosensor 20, and a controller 30.
The coherent light source 10 is used for emitting coherent light beams to scan transparent or semitransparent materials to be inspected, and may be a laser, a laser diode, a laser array, or the like.
The photoelectric sensor 20 is used for collecting scattered light intensity images of the material to be detected, and may be a camera or other photosensitive elements capable of converting optical signals into electrical signals. The controller 30 may be a computer system based on von neumann system that relies on the execution of a computer program, may be a single chip microcomputer integrated on other components, or may be a separate personal computer, notebook computer, server device.
The microscopic defect detection system of the transparent or semitransparent material is based on the generalized Lorenz-Mich theory.
When light passes through any medium except vacuum, part of the light deviates from the original propagation direction and diffuses to the periphery, namely, the light scattering phenomenon. Light scattering is generally divided into two types: pure medium light scattering and non-pure medium light scattering.
(1) Pure medium light scattering: it means that light scattering phenomenon still occurs when light propagates in pure substances without any defects. This phenomenon is inherent to any substance itself and has no relation to whether the propagator contains defects or not.
(2) Non-pure medium light scattering: refers to a scattering phenomenon that light propagates in a substance containing defects (e.g., bubbles, impurities, cracks, waviness, scratches, bruises, etc.) and occurs when the light encounters these defects. The scattering phenomenon is not inherent to the substance, and the intensity of scattered light is related to the properties of the defect. The frequency of its scattered light and incident light is the same, and the size of its scattered light intensity is also relevant with the wavelength size of incident light, specifically is:
wherein, Iscaλ is the wavelength of the incident light, and a is a positive integer.
Based on the generalized Lorenz-Mich theoryThe relation between the properties of the light beam (a coherent light) and the relative position of the scatterers, and a parameter that can express the positional relation thereof is defined as gnWhen the laser is incident on the scatterer, when the scatterer is positioned at the center of the beam, gnIs expressed as:
wherein, ω is0Is the laser beam waist size of the laser beam.
Then, when the incident laser beam is scattered by the scatterer, the intensity of the light at a point P in space is:
wherein the content of the first and second substances,
is the space coordinate of P point and scatterer as reference system, r is the distance from P point to scatterer, theta is the scattering angle of P point,
is the azimuth angle of point P, q is the particle size parameter, m is the complex refractive index, omega0Is the laser beam waist size of the laser beam, I0Is the intensity of the incident light. To simplify the calculation, can order
Is 0, that is, the P point can be defined as being at azimuth angle
On a circle of distance r.
At this time, the light intensity of the point P can be expressed as:
wherein, an,bn,τn,πnThe mie scattering coefficient.
Since m and q are unknown in actual detection, the detection can be carried out
The photoelectric sensor is controlled to obtain different space light intensity combinations at different space receiving positions, namely, a plurality of P points are selected on the spherical surface of the scattering body to acquire scattering light intensity information, and the correlation between the space light intensity and defect information is established, namely, a database model corresponding to the relative acquisition position (the position of the P point) of the scattering light acquired by the photoelectric sensor and the scattering light intensity space distribution is established by adopting a method combining theoretical simulation and practice, then the scattering light intensity acquired by the photoelectric sensor at a certain relative acquisition position P point is compared with reference scattering light intensity corresponding to the relative acquisition position P point and stored in the database model, and whether the scattering light intensity acquired by the relative acquisition position P point is the scattering light caused by the defect or not can be judged according to the difference, so that whether the defect exists in the material to be detected or not and the size of the defect are determined.
In the present exemplary embodiment, that is to say, the photoelectric sensor 20 has a relative acquisition position in space with the coherent light source 10 and the material to be examined, which relative acquisition position comprises at least the scatter angle and the distance to the material to be examined. The controller 30 is used for acquiring the scattered light intensity image corresponding to the scanning position; performing Fourier transform on the scattered light intensity image to obtain a corresponding amplitude spectrum and a corresponding phase spectrum, and acquiring cut-off frequencies of the amplitude spectrum and the phase spectrum; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position.
The controller 30 is further configured to monitor a scanning position when the cut-off frequency does not belong to the frequency threshold range as a defect position, and determine a defect according to the defect position; and the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
Referring to fig. 2, fig. 2 shows the spatial scattering intensity distribution under the defect with the refractive index of the material being 0.56 and the radius of the defect being 6.6um and 13.2um respectively. Along with the increase or decrease of the size of the scatterer, the distance value between the wave peaks in a space range is decreased, more precisely, the angle value between the two wave peaks is decreased, the distribution of the space scattering light intensity in a certain range is processed by FFT (Fourier transform), and for different q values (different defect sizes) with the same refractive index (same defect material), the cut-off frequency of the phase frequency and amplitude frequency curve is increased along with the increase of the q value, namely along with the increase of the defect size.
Referring again to fig. 3 and 4, fig. 3 and 4 show the amplitude-frequency curve and the phase-frequency curve of the scattered light intensity distribution after FFT. Since the cutoff frequency of the scattered light within the fixed spatial range is also monotonically increased as the size of the scatterer, that is, the size of the defect, is increased, the size of the defect can be determined by the cutoff frequency of the scattered light within the fixed spatial range in the actual detection process. In the actual detection, the existence and the size of the defect can be judged only by comparing the actually received scattered light cut-off frequency with a theoretical calculation simulation value.
Specifically, in this embodiment, the system further includes a stage 40 for carrying the material to be inspected. As shown in fig. 1, the stage further includes orthogonal X-direction and Y-direction moving mechanisms for driving the material to be detected to move in the X-direction and the Y-direction for scanning. The coherent light source and the photoelectric sensor are fixed relative to the position of the material to be detected in the scanning process.
In this embodiment, the scanning process includes moving the object carrying table 40 in the X or Y direction along the X or Y axis with the linear coherent light beam emitted by the coherent light source, so that the coherent light beam linearly scans the transparent or translucent building material, imaging the scattered light intensity of the object by the photoelectric sensor, processing the image to obtain an object scattered light intensity distribution diagram, performing FFT on the scattered light intensity distribution diagram to obtain an amplitude-frequency curve and a phase-frequency curve, monitoring the cutoff frequency of the amplitude-frequency curve information and the phase-frequency curve information generated by FFT of the scattered light intensity of the object to be measured in real time, comparing the cutoff frequency with the frequency threshold range corresponding to the relative acquisition position stored in the database model corresponding to the spatial distribution of the scattered light intensity calculated in advance by the theoretical value in real time, and if the cutoff frequency is not in the frequency threshold range, the scanning position is recorded as a defective position.
For example, referring to fig. 5, when the object stage 40 moves along the X axis to bring the material to be inspected, when the X1 position is reached, the cutoff frequency is detected not to be in the corresponding frequency threshold range, and when the X2 position is reached, the cutoff frequency is detected to be restored in the corresponding frequency threshold range, and the position in the X1 to X2 interval is recorded on the X axis, and there is a defect. Similarly, when the stage 40 moves the material to be inspected along the Y axis, when reaching the position Y1, the cutoff frequency is detected not to be in the corresponding frequency threshold range, and when reaching the position Y2, the cutoff frequency is detected to be restored in the corresponding frequency threshold range, and the position in the interval Y1 to Y2 can be recorded on the Y axis, and there is a defect. Then, it can be determined that there is a defect at the rectangular position determined by the four vertices x1, x2, y1, and y2 of the sample material.
In another embodiment, the controller 30 is configured to move the coherent light source 10 and/or the photosensor 20 to scan the material under test. The controller 30 is further configured to monitor a relative acquisition position of the photoelectric sensor 20 with respect to the coherent light source 10 and the material to be inspected, and acquire a frequency threshold range corresponding to the relative acquisition position.
That is, a fixed stage may be used, and the scanning of the material to be inspected may be realized by moving the coherent light source 10 to move the scanning line without moving the material to be inspected by the stage. However, as for the controller, the defect identification algorithm is consistent, and the relative acquisition position of the photoelectric sensor 20 for acquiring the scattering imaging at that time can be determined only by acquiring the relative positions of the real-time coherent light source 10 and the photoelectric sensor 20, so that the corresponding frequency threshold range is read from the database, and then the corresponding frequency threshold range is compared with the cut-off frequency monitored in real time, and the defect of the material to be inspected can be identified.
In one embodiment, the number of photosensors may be N, and N is greater than or equal to 2. The N photoelectric sensors, the coherent light source and the material to be examined have N relative acquisition positions in space, and during the scanning process, there are N relative acquisition positions corresponding to one scanning position.
The controller is also used for monitoring N cut-off frequencies corresponding to the scattered light intensity images acquired by the N corresponding acquisition positions corresponding to the scanning position, and if the cut-off frequencies do not belong to the corresponding frequency threshold range, the scanning position is recorded as a defect position.
That is, a plurality of photoelectric sensors may be provided, and when scanning to a scanning position, the scanning position may be acquired at a plurality of relative acquisition positions, and as long as a cutoff frequency of a scattered light intensity distribution acquired at one relative acquisition position is not within a frequency threshold range corresponding to the relative acquisition position pre-stored in the database, it is determined that the material under test is defective at the scanning position. Therefore, the condition that the single photoelectric sensor is used for collecting the missed detection possibly caused by the influence of ambient light or other noises is avoided, and the multiple photoelectric sensors can be used for detecting at multiple scattering angles, so that the condition of missed detection is prevented.
After the defect in the material to be inspected, the controller 30 may check the defect in the material to be inspected in other manners, for example, manual re-inspection or other manners, so as to confirm the accuracy of the defect detection, and if the situation is inaccurate, it means that the theoretical reference value stored in the database is not accurate, in this case, the frequency threshold range corresponding to the relative acquisition position corresponding to the defect detected by mistake in the database may be updated according to the situation of the re-inspection, so as to update the theoretical reference value, and when the next detection is performed, the false detection may be reduced, and the accuracy of the detection may be improved.
In order to solve the problems that the conventional optical three-dimensional scanning and two-dimensional imaging methods are difficult to detect the microscopic defects of the transparent or semitransparent surface and have high omission factor and false detection rate, as shown in fig. 6, the invention also provides a microscopic defect detection method for the transparent or semitransparent material, and the implementation of the method depends on a computer program and is based on the controller 30. Specifically, the method comprises the following steps:
step S102: the material under test is scanned by a coherent light beam.
Step S104: when scanning to a scanning position: collecting scattered light intensity imaging of the material to be detected at a relative collecting position; and carrying out Fourier transform on the scattered light intensity image to obtain a corresponding amplitude spectrum and a corresponding phase spectrum, and obtaining the cut-off frequency of the amplitude spectrum and the phase spectrum.
The relative acquisition position at least comprises a scattering angle and a distance to the material to be detected; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position.
Step S106: monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range as a defect position, and determining a defect according to the defect position; the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
In one embodiment, the scan is a line scan, and the scan direction includes orthogonal X and Y directions.
In one embodiment, the relative acquisition positions are N, and N is greater than or equal to 2. Monitoring the scanning position when the cut-off frequency does not belong to the frequency threshold range as a defect position comprises:
and for a scanning position, if a cutoff frequency does not belong to a corresponding frequency threshold range in N cutoff frequencies corresponding to scattered light intensity imaging acquired at N relative acquisition positions corresponding to the scanning position, recording the scanning position as a defect position.
In one embodiment, after determining the defect according to the defect position, the method further comprises: and checking the defects, and updating the frequency threshold range according to the checking result.
The embodiment of the invention has the following beneficial effects:
the transparent or semitransparent material micro defect detection system and the transparent or semitransparent material micro defect detection method based on the controller in the system are adopted, the transparent or semitransparent material is scanned by coherent light, when the transparent or semitransparent material is scanned to a scanning position, scattered light intensity distribution is collected at a certain scattering angle and distance, the scattered light intensity distribution is compared with a reference value calculated according to Lorenz-Mich theory, the scanning position where the scattered light intensity distribution does not accord with the reference value is recorded as a defect position, and therefore after scanning is finished, the size and the type of defects in a material to be detected can be determined by integrating a set of the defect positions in the material to be detected. The system and the method are not influenced by the light transmittance of the transparent or semitransparent material to be detected due to the collected scattered light. Meanwhile, the scattered light intensity distribution acquired in real time is compared with a reference value calculated theoretically, so that the false detection rate and the missed detection rate are low.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.
Claims (10)
1. A microscopic defect inspection system for transparent or translucent materials, comprising:
the coherent light source is used for emitting coherent light beams to scan the transparent or semitransparent material to be detected;
the photoelectric sensor is used for acquiring scattered light intensity imaging of the material to be detected, and the photoelectric sensor, the coherent light source and the material to be detected have relative acquisition positions in space, and the relative acquisition positions at least comprise scattering angles and distances to the material to be detected;
the controller is used for acquiring the scattered light intensity image corresponding to the scanning position; performing Fourier transform on the scattered light intensity image to obtain corresponding amplitude-frequency curve information and phase-frequency curve information, and obtaining cut-off frequencies of the amplitude-frequency curve information and the phase-frequency curve information; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position;
monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range, taking the scanning position as a defect position, and determining a defect according to the defect position;
the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
2. The transparent or translucent material microdefect detection system of claim 1 further comprising a stage for carrying the inspection material;
the object stage also comprises orthogonal X-direction and Y-direction movement mechanisms for driving the material to be detected to move in the X direction and the Y direction for scanning;
the coherent light source and the photoelectric sensor are fixed relative to the material to be detected in the scanning process.
3. The transparent or translucent material microdefect detection system of claim 1, wherein the controller is configured to move the coherent light source and/or the photosensor to scan the material under test;
the controller is also used for monitoring the relative acquisition position of the photoelectric sensor relative to the coherent light source and the material to be detected, and acquiring the frequency threshold range corresponding to the relative acquisition position.
4. The transparent or translucent material microdefect detection system of claim 1 wherein the number of photosensors is N, and N is greater than or equal to 2; the N photoelectric sensors, the coherent light source and the material to be detected have N relative acquisition positions in space.
5. A microscopic defect detection system for transparent or translucent materials according to claim 4, wherein during scanning, there are N corresponding relative acquisition positions for a scanning position;
the controller is further used for monitoring N cut-off frequencies corresponding to scattered light intensity imaging acquired by N corresponding acquisition positions corresponding to the scanning positions, and if the cut-off frequencies do not belong to corresponding frequency threshold ranges, the scanning positions are recorded as defect positions.
6. The transparent or translucent material microdefect detection system of claim 1, wherein the coherent light source is a laser source and the inspection material is scanned in a line scan.
7. A microscopic defect detection method of transparent or semitransparent material based on the controller of any one of claims 1 to 6, characterized by comprising:
scanning the material to be detected by coherent light beams;
when scanning to a scanning position: collecting scattered light intensity imaging of the material to be detected at a relative collecting position; performing Fourier transform on the scattered light intensity image to obtain corresponding amplitude-frequency curve information and phase-frequency curve information, and obtaining cut-off frequencies of the amplitude-frequency curve information and the phase-frequency curve information;
the relative acquisition position at least comprises a scattering angle and a distance to the material to be detected; the cut-off frequency corresponds to the scanning position and a relative acquisition position corresponding to the scanning position;
monitoring a scanning position when the cut-off frequency does not belong to a frequency threshold range, taking the scanning position as a defect position, and determining a defect according to the defect position;
the frequency threshold range is a reference value range which is calculated in advance according to Lorenz-Mich theory and is based on non-pure medium light scattering and corresponds to the relative acquisition position.
8. The method of claim 7, wherein the scanning is line scanning and the scanning direction comprises orthogonal X and Y directions.
9. The method for detecting the microscopic defects of the transparent or semitransparent material according to claim 7, wherein the number of the relative collection positions is N, and N is greater than or equal to 2;
the monitoring of the scanning position when the cut-off frequency does not belong to the frequency threshold range as the defect position comprises:
and for a scanning position, if a cutoff frequency does not belong to a corresponding frequency threshold range in N cutoff frequencies corresponding to scattered light intensity imaging acquired at N relative acquisition positions corresponding to the scanning position, recording the scanning position as a defect position.
10. The method of claim 7, further comprising, after determining the defect based on the defect location:
and checking the defects, and updating the frequency threshold range according to the checking result.
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| PCT/CN2019/081552 WO2020199206A1 (en) | 2019-04-04 | 2019-04-04 | Transparent or semi-transparent material microscopic-defect detection system and method |
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| CN111929310A (en) * | 2020-09-25 | 2020-11-13 | 歌尔股份有限公司 | Surface defect detection method, device, equipment and storage medium |
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