Laser illumination defect detection imaging system

Abstract

The invention belongs to the technical field of defect detection, and particularly discloses a laser illumination defect detection imaging system which comprises a laser illuminator, an objective table and an imaging camera. The laser illuminator comprises a laser emission head; the laser emitting head comprises a laser chip, a collimating lens, a diffractive optical element and a phase delay sheet which are sequentially arranged along the laser irradiation direction; the distance between the laser chip and the collimating lens is 5mm to 7mm; the distance between the collimating lens and the diffractive optical element is 1-3mm; and the distance between the phase delay sheet and the diffractive optical element is 1-3mm. The laser emission head can emit collimated circularly polarized light with uniformly distributed energy, after the collimated circularly polarized light with uniformly distributed energy enters the surface defect of the detected optical element, the light reflected to the imaging camera is stronger, and even if the depth of the defect of the optical element is less than 5 microns, the laser with certain intensity can be reflected, so that the detection accuracy is improved. Reflected light of surface defects is collected, and the defects of the optical element are better detected.

Description

Technical Field

[0001] The present invention relates to the technical field of defect detection, and particularly to a laser illumination defect detection imaging system. Background Art

[0002] Surface defects of optical elements will cause scattering and energy loss of the light beam incident on the element surface. In high-power laser applications, surface defects will cause film layer damage and local energy absorption, affecting the service life and efficiency of optical elements. The complexity of surface defects makes detection difficult, such as the depth and directionality of scratches, the roughness of the side edges of pockmarks, and the irregularity of defect shapes.

[0003] Currently, defect detection usually uses a low-angle LED ring light source, usually visible light, to achieve dark-field illumination. The surface defect images of the product are collected by a camera and then further processed to detect the defect results. However, the dark-field illumination method using an LED ring light source has technical defects such as uneven light intensity, a large divergence angle (more than 15 degrees), and an adjustable incident angle of the light beam. The image quality collected is not good, and the defect contrast does not meet the requirements of subsequent image processing. For some defects, especially those with a depth and width within 5 microns, it is difficult to collect them, resulting in some defects that cannot be detected, affecting the use of optical elements. Or, the surface shape data of the element surface and the defect area is collected by means of optical interference, the data is recorded by a camera and the software is used to analyze and reproduce the shape of the defect area to achieve defect evaluation. However, the method of optical interference to reproduce surface defects is relatively slow, the algorithm is complex and requires a large amount of hardware computing power, resulting in low efficiency of the detection device. Summary of the Invention

[0004] The purpose of the present invention is to provide a laser illumination defect detection imaging system to solve the technical problems in the prior art that the image quality collected by the detection imaging system is not good, the defect contrast does not meet the requirements of subsequent image processing, and for some defects, especially those with a depth and width within 5 microns, it is difficult to collect them, resulting in some defects that cannot be detected, affecting the use of optical elements.

[0005] To achieve the above purpose, the present invention provides a laser illumination defect detection imaging system, which includes: a laser illuminator, a stage, and an imaging camera; the laser illuminator is used to emit light to the optical element on the stage; the imaging camera is used to collect the reflected image of the optical element.

[0006] The laser illuminator includes a laser emitting head; the laser emitting head includes a laser chip, a collimating lens, a diffractive optical element, and a phase delay plate arranged in sequence along the laser irradiation direction; wherein the distance between the laser chip and the collimating lens is 5 mm to 7 mm; the collimating lens has curved surfaces on both sides along the laser irradiation direction, the radius of the curved surface of the collimating lens facing the laser chip is 11 mm to 13 mm, and the radius of the curved surface of the collimating lens facing away from the laser chip is 14 mm to 16 mm; the distance between the collimating lens and the diffractive optical element is 1 to 3 mm; the distance between the phase delay plate and the diffractive optical element is 1 to 3 mm.

[0007] Preferably, it also includes: an angle adjustment device; the angle adjustment device is connected to the laser emitting head, and the angle adjustment device is used to adjust the emission angle of the laser emitting head.

[0008] Preferably, the number of the laser emitting heads is at least three; the laser illuminator comprises: a lighting bracket; the laser emitting heads are hinged to the lighting bracket, and at least three of the laser emitting heads are arranged around the lighting bracket.

[0009] Preferably, it further comprises: a transmitting seat; the transmitting seat is hinged to the lighting bracket, the laser transmitting head is arranged on the transmitting seat, and the laser transmitting head is hinged to the lighting bracket through the transmitting seat.

[0010] Preferably, the angle adjustment device includes a linear drive module and a drive member; the linear drive module is connected to the drive member, and the linear drive module is used to drive the drive member to move linearly; the drive member is in contact with the transmitting seat, and the linear drive module drives the transmitting seat to rotate around the lighting bracket through the drive member.

[0011] Preferably, it further comprises: a return spring, one end of which is connected to the launch seat, and the other end of which is connected to the lighting bracket, and the return spring is used to press the launch seat toward the driving member.

[0012] Preferably, the number of the emitting seats corresponds to the number of the laser emitting heads one by one, and a plurality of the emitting seats are arranged on the lighting bracket in a divergent manner.

[0013] Preferably, the imaging camera, the laser illuminator and the stage are sequentially arranged along an imaging direction; the lighting bracket is provided with an imaging hole; the imaging hole is located at a position of the lighting bracket corresponding to the imaging camera along the imaging direction.

[0014] Preferably, it further comprises: a planar moving mechanism; the loading platform is arranged on the planar moving mechanism.

[0015] Preferably, it further includes: a polarizer; the imaging camera is provided with an imaging lens, and the polarizer is arranged on one side of the imaging lens facing the stage.

[0016] For the laser illumination defect detection imaging system provided by the present invention, its beneficial effects are as follows: the laser emitting head includes a laser chip, a collimating lens, a diffractive optical element, and a phase retarder arranged in sequence along the laser irradiation direction. Then, the laser emitting head can emit collimated circularly polarized light with a uniform energy distribution. After the collimated circularly polarized light with a uniform energy distribution is incident on the surface defect of the optical element to be detected, the light reflected to the imaging camera is stronger. Even if the depth of the defect of the optical element is less than 5 microns, a certain intensity of laser can be reflected, which is beneficial to improving the image contrast at the defect, so as to facilitate the imaging camera to collect the reflected light of the surface defect, better detect the defect of the optical element, ensure the reliability of the optical element, and ensure that the optical element can be used normally.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the laser illumination defect detection imaging system according to an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of the laser emitting head according to an embodiment of the present invention;

[0020] Figure 3 is a schematic structural diagram of the assembled lighting bracket and angle adjusting device according to an embodiment of the present invention;

[0021] Figure 4 is a schematic structural diagram of the assembled lighting bracket and angle adjusting device from another perspective according to an embodiment of the present invention.

[0022] In the figure, 100, laser illuminator; 110, laser emitting head; 111, laser chip; 112, collimating lens; 113, diffractive optical element; 114, phase retarder; 120, lighting bracket; 121, imaging hole; 200, stage; 300, imaging camera; 310, imaging lens; 400, angle adjusting device; 410, linear driving module; 420, driving member; 500, emitting seat; 600, return spring; 700, planar moving mechanism; 800, polarizer; 900, optical element to be measured. Detailed Embodiments

[0023] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0024] In the description of the present invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0025] In the description of the present invention, the meaning of "a number of" is one or more, the meaning of "a plurality of" is two or more, "greater than", "less than", "exceeding", etc. are understood as not including the number itself, and "above", "below", "within", etc. are understood as including the number itself. If there is a description of "first" and "second", it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0026] In the description of the present invention, unless otherwise clearly defined, words such as "arrangement", "installation", "connection", etc. should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0027] Please refer to Figures 1 to 4 together, and now a laser illumination defect detection imaging system provided by an embodiment of the present invention will be described.

[0028] Referring to Figures 1 to 3 , a laser illumination defect detection imaging system according to an embodiment of the present invention includes: a laser illuminator 100, a stage 200, and an imaging camera 300; the laser illuminator 100 is used to emit light to an optical element on the stage 200; the imaging camera 300 is used to collect a reflected image of the optical element; the stage 200 is used to carry the optical element so as to move the optical element to a test position, facilitating the laser illuminator 100 to perform defect detection on the optical element;

[0029] The laser illuminator 100 includes a laser emitting head 110; the laser emitting head 110 includes a laser chip 111, a collimating lens 112, a diffractive optical element 113, and a phase delay plate 114 arranged in sequence along the laser irradiation direction; wherein, the distance D1 between the laser chip 111 and the collimating lens 112 is 5 mm to 7 mm; the collimating lens 112 has curved surfaces on both sides along the laser irradiation direction, the radius of the curved surface of the collimating lens 112 facing the laser chip 111 is 11 mm to 13 mm, and the radius of the curved surface of the collimating lens 112 facing away from the laser chip 111 is 14 mm to 16 mm; the distance D2 between the collimating lens 112 and the diffractive optical element 113 is 1 to 3 mm; the distance D3 between the phase delay plate 114 and the diffractive optical element 113 is 1 to 3 mm. The laser chip 111 is a semiconductor chip. The laser generated by the laser chip 111 forms a collimated Gaussian beam after passing through the collimating lens 112, and then passes through the diffractive optical element 113 to be shaped into a flat-top beam with uniform energy distribution, and finally passes through the phase delay plate 114, so that the beam changes from linear polarized light to circular polarized light, so that the laser emitted by the laser emitter 110 can be collimated circularly polarized light with uniform energy distribution. Therefore, after the collimated circularly polarized light with uniform energy distribution emitted by the laser emitter 110 is incident on the surface defect of the optical element to be detected, the light reflected to the imaging camera 300 is more powerful. Even if the depth of the defect of the optical element is less than 5 microns, it can still reflect a certain intensity of laser light, which is conducive to improving the image contrast at the defect, so as to facilitate the imaging camera 300 to collect the reflected light of the surface defect, better detect the defects of the optical element, ensure the reliability of the optical element, and ensure that the optical element can be used normally.

[0030] It should be noted that, in order to obtain better laser reflection imaging, the distance between the laser chip 111 and the collimating lens 112 is 6 mm; the radius of the curved surface of the collimating lens 112 facing the laser chip 111 is 12 mm, and the radius of the curved surface of the collimating lens 112 away from the laser chip 111 is 15 mm; the distance between the collimating lens 112 and the diffractive optical element 113 is 2 mm; the distance between the phase delay plate 114 and the diffractive optical element 113 is 2 mm. Through such an arrangement, the energy distribution of the laser emitted by the laser transmitting head 110 is more uniform, so as to obtain collimated circularly polarized light for better imaging, so as to better detect defects on optical elements.

[0031] In some embodiments of the present invention, reference Figures 1 to 3, the laser illumination defect detection imaging system further includes: an angle adjustment device 400; the angle adjustment device 400 is connected to the laser emitting head 110, and the angle adjustment device 400 is used to adjust the emission angle of the laser emitting head 110, so that the angle of the laser irradiating on the optical element can be adjusted, so as to perform laser detection irradiation on the optical element from multiple angles, so as to better detect the defects on the surface of the optical element.

[0032] In some embodiments of the present invention, referring to Figures 1 to 3 , the number of the laser emitting heads 110 is at least three; the laser illuminator 100 includes: an illumination bracket 120; the laser emitting heads 110 are hinged to the illumination bracket 120, and at least three of the laser emitting heads 110 are arranged around the illumination bracket 120, so the laser illuminator 100 is an annular laser illumination mirror group. Multiple laser emitting heads 110 can be used to irradiate the optical element from different directions at the same time, and combined with the angle adjustment device 400 to adjust the laser emission directions of the multiple laser emitting heads 110. No matter which direction the side pit at the defective part of the optical element faces, the laser reflected from the defective part can be reflected into the imaging lens 310, so as to better detect the defects on the surface of the optical element.

[0033] In some embodiments of the present invention, referring to Figures 1 to 3 , the laser illumination defect detection imaging system further includes: a launching seat 500; the launching seat 500 is hinged to the illumination bracket 120, the laser emitting head 110 is arranged on the launching seat 500, and the laser emitting head 110 is hinged to the illumination bracket 120 through the launching seat 500. The angle adjustment device 400 can drive the launching seat 500 or the laser emitting head 110 to adjust the laser emission angle of the laser emitting head 110. Specifically, the angle adjustment device 400 can drive the laser emitting head 110 to rotate through the launching seat 500, avoiding the angle adjustment device 400 from damaging the laser emitting head 110 when moving, so as to protect the laser emitting head 110.

[0034] In some embodiments of the present invention, referring to Figures 1 to 3, the angle adjustment device 400 includes a linear drive module 410 and a drive member 420; the linear drive module 410 is connected to the drive member 420, and the linear drive module 410 is used to drive the drive member 420 to move linearly; the drive member 420 contacts the emission seat 500, and the linear drive module 410 drives the emission seat 500 to rotate around the lighting bracket 120 through the drive member 420. The linear drive module 410 can be a screw linear drive mechanism driven by electricity. The drive member 420 contacts the emission seat 500, and the linear drive module 410 pushes the emission seat 500 to rotate around the lighting bracket 120 to adjust the laser emission angle of the laser emitter 110 provided on the emission seat 500, so that the optical element can be irradiated with laser for detection from multiple angles to better detect the defects on the surface of the optical element. It should be noted that in this embodiment, the adjustable laser emission angle of the laser emitter 110 is 10° to 90°, such as Figure 3 and Figure 4 shown, the current laser emission angle of the laser emitter 110 is 45°.

[0035] In some embodiments of the present invention, referring to Figures 3 to 4 , the laser illumination defect detection imaging system further includes: a return spring 600, one end of the return spring 600 is connected to the emission seat 500, and the other end of the return spring 600 is connected to the lighting bracket 120. The return spring 600 is used to press the emission seat 500 against the drive member 420. It can be understood that in this embodiment, the return spring 600 is a tension spring, and the return spring 600 provides a pulling force for the reflection seat to pull the emission seat 500 to always press against the drive member 420, ensuring that the drive member 420 can push the emission seat 500 to rotate around the lighting bracket 120 when moving, and ensuring that the laser emission angle of the adjustable laser emitter 110 can be adjusted. In addition, the return spring 600 can also be a compression spring, a torsion spring, etc., which can provide a force for the reflection seat to press against the drive member 420.

[0036] In some embodiments of the present invention, referring to Figures 3 to 4 , the number of the emission seats 500 corresponds to the number of the laser emitters 110 one by one, and a plurality of the emission seats 500 are arranged on the lighting bracket 120 in a divergent manner. That is, a plurality of laser emitters 110 are distributed in a ring, so that a plurality of laser emitters 110 can be aligned with the optical element for laser irradiation at multiple angles, so as to better detect the defects on the surface of the optical element.

[0037] In some embodiments of the present invention, referring to Figure 1 and Figure 3, the imaging camera 300, the laser illuminator 100, and the stage 200 are arranged in sequence along the imaging direction X; the illumination bracket 120 is provided with an imaging hole 121; the imaging hole 121 is located at the position of the illumination bracket 120 corresponding to the imaging camera 300 along the imaging direction. The imaging camera 300 is aligned with the stage 200 through the imaging hole 121 to collect the reflected light at the defect of the optical element for imaging.

[0038] In some embodiments of the present invention, referring to Figure 1 , the laser illumination defect detection imaging system further includes: a planar moving mechanism 700; the stage 200 is arranged on the planar moving mechanism 700. The planar moving mechanism 700 can use two lead screw driving devices in cooperation, or use two cylinders or other linearly drivable devices in cooperation, so that the stage 200 can be translated in parallel to move the position of the optical element by the stage 200, so that each position of the optical element can be irradiated and detected by the laser illuminator 100, which is convenient for detecting the whole optical element and ensuring that each position of the optical element is detected.

[0039] In some embodiments of the present invention, referring to Figure 1 , the laser illumination defect detection imaging system further includes: a polarizer 800; the imaging camera 300 is provided with an imaging lens 310, and the polarizer 800 is arranged on the side of the imaging lens 310 facing the stage 200. That is, after the laser emitted by the laser emitting head 110 is reflected from the optical element, it will pass through the polarizer 800 and then enter the imaging camera 300; since the laser is linearly polarized light, the phase retardation plate 114 is used to convert the linearly polarized light into circularly polarized light. The polarization states of the reflected light from the smooth surface and the defect in the optical element are different when the polarized light is incident. Adding a polarizer 800 to the imaging lens 310 to screen the reflected light at a specific polarization angle can filter the reflected light from the smooth surface and pass the reflected light from the defect, improving the imaging contrast at the defect to better detect the defect of the optical element.

[0040] When the laser illumination defect detection imaging system is in use, first place the optical element 900 to be measured on the stage 200. Subsequently, the planar moving mechanism 700 moves to move the optical element 900 to a position where the imaging lens 310 can acquire an image. Then, the laser illuminator 100 is activated to irradiate the laser on the surface of the optical element 900 to be measured, and the imaging camera 300 starts to collect images. The imaging camera 300 sends the image information to the industrial control computer for image processing to detect the defects of the optical element. When the detection of the current position of the optical element is completed, the planar moving mechanism 700 moves the optical element to the next detection position to detect different positions of the optical element. It can be understood that whenever the optical element moves to another detection position, the angle adjustment device 400 will quickly drive the laser emitting head 110 to rotate so that the laser emitting head 110 irradiates the optical element with laser from multiple angles. The collected images are transmitted to the industrial control host for processing, and then the clearest frame of the surface defect is retained. Finally, the complete image information of the optical element 900 to be measured is obtained by stitching the images collected multiple times, and the surface defect information is processed.

[0041] In summary, the laser illumination defect detection imaging system has at least the following beneficial effects:

[0042] (1) The laser emitting head 110 of the laser illuminator 100 can emit collimated circularly polarized light with uniform energy distribution. After the collimated circularly polarized light with uniform energy distribution is incident on the surface defect of the optical element to be detected, the light reflected to the imaging camera 300 is stronger. Even if the depth of the defect of the optical element is less than 5 microns, it can reflect a certain intensity of laser, which is beneficial to improving the image contrast at the defect, so as to facilitate the imaging camera 300 to collect the reflected light of the surface defect and better detect the defect of the optical element, ensuring the reliability of the optical element and ensuring that the optical element can be used normally;

[0043] (2) By setting the angle adjustment device 400, the emission angle of the laser emitting head 110 can be adjusted, so that the angle of the laser irradiation on the optical element can be adjusted to perform laser detection irradiation on the optical element from multiple angles to better detect the defects on the surface of the optical element;

[0044] (3) The polarization states of the reflected light of the polarized light incident on the smooth surface and the defect of the optical element are different. By adding a polarizer 800 to the imaging lens 310 to screen the reflected light at a specific polarization angle, the reflected light passing through the defect can be used to improve the imaging contrast at the defect to better detect the defect of the optical element.

[0045] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A laser illumination defect detection imaging system, characterized in that: include: A laser illuminator, a stage, and an imaging camera; the laser illuminator is used to emit light to the optical element on the stage; the imaging camera is used to collect the reflected image of the optical element; The laser illuminator includes a laser emitting head; the laser emitting head includes a laser chip, a collimating lens, a diffractive optical element, and a phase delay plate arranged in sequence along the laser irradiation direction; wherein the distance between the laser chip and the collimating lens is 5 mm to 7 mm; the collimating lens has curved surfaces on both sides along the laser irradiation direction, the radius of the curved surface of the collimating lens facing the laser chip is 11 mm to 13 mm, and the radius of the curved surface of the collimating lens facing away from the laser chip is 14 mm to 16 mm; the distance between the collimating lens and the diffractive optical element is 1 to 3 mm; the distance between the phase delay plate and the diffractive optical element is 1 to 3 mm.

2. The laser illumination defect detection imaging system according to claim 1, characterized in that: Also includes: Angle adjustment device; the angle adjustment device is connected to the laser emitting head, and the angle adjustment device is used to adjust the emission angle of the laser emitting head.

3. The laser illumination defect detection imaging system according to claim 2, characterized in that: The number of the laser emitting heads is at least three; the laser illuminator comprises: an illuminating bracket; the laser emitting heads are hinged to the illuminating bracket, and at least three laser emitting heads are arranged around the illuminating bracket.

4. The laser illumination defect detection imaging system according to claim 3, characterized in that: Also includes: Transmitting seat; the transmitting seat is hinged to the lighting bracket, the laser transmitting head is arranged on the transmitting seat, and the laser transmitting head is hinged to the lighting bracket through the transmitting seat.

5. The laser illumination defect detection imaging system according to claim 4, characterized in that: The angle adjustment device includes a linear drive module and a drive member; the linear drive module is connected to the drive member, and the linear drive module is used to drive the drive member to move linearly; the drive member is in contact with the launch seat, and the linear drive module drives the launch seat to rotate around the lighting bracket through the drive member.

6. The laser illumination defect detection imaging system according to claim 5, characterized in that: Also includes: A return spring, one end of which is connected to the launch seat, and the other end of which is connected to the lighting bracket, and the return spring is used to press the launch seat toward the driving member.

7. The laser illumination defect detection imaging system according to claim 5, characterized in that: The number of the emitting seats corresponds to the number of the laser emitting heads one by one, and a plurality of the emitting seats are arranged on the lighting bracket in a divergent manner.

8. The laser illumination defect detection imaging system according to claim 3, characterized in that: The imaging camera, the laser illuminator and the stage are arranged in sequence along an imaging direction; the lighting bracket is provided with an imaging hole; the imaging hole is located at a position of the lighting bracket corresponding to the imaging camera along the imaging direction.

9. The laser illumination defect detection imaging system according to claim 1, characterized in that: Also includes: Planar moving mechanism; the object carrier is arranged on the planar moving mechanism.

10. The laser illumination defect detection imaging system according to claim 1, characterized in that: Also includes: Polarizer; the imaging camera is provided with an imaging lens, and the polarizer is arranged on a side of the imaging lens facing the stage.

Images