CN115389526A - Spherical bending surface defect detection system and detection method - Google Patents
Spherical bending surface defect detection system and detection method Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention discloses a spherical bending surface defect detection system and a detection method, comprising the following steps: the device comprises a clamping rotating module and a detection module, wherein the detection module comprises a light source, a bright field imaging unit and a dark field imaging unit. S1: clamping the measured lens by using a clamping and rotating module; s2: the clamping and rotating module clamps the measured lens and rotates by a central shaft of the clamping and rotating module, and meanwhile, the detection module deflects by a spherical center of the upper surface of the measured lens; or the clamping and rotating module clamps the measured lens to rotate around the central shaft of the clamping and rotating module, and meanwhile, the clamping and rotating module clamps the measured lens to deflect around the spherical center of the upper surface of the measured lens; s3: the dark field detection element and the bright field detection element convert the optical signal into an electrical signal. The optical lens for detecting the spherical surface is not only suitable for a plane or a spherical surface with a large curvature radius, but also suitable for a spherical surface with a small curvature radius, and has strong adaptability and high detection precision.
Description
Technical Field
The invention relates to the technical field of detection of defects of a spherical bending surface, in particular to a system and a method for detecting the defects of the spherical bending surface.
Background
The size and number of the surface defects of the optical lens are important indexes of products leaving a factory in a lens processing factory, and the surface defects of the optical lens specifically comprise scratches, point injuries, dirt and the like. The lens with the defects can affect the imaging quality of the assembled lens, and bring adverse effects such as veiling glare and unclear imaging. Therefore, the defect detection of the lens surface is one of important means for realizing quality control, improving the production process and optimizing the product performance. The traditional method for detecting the surface defects of the lens mainly adopts a manual detection mode, and has the following defects: 1. the consistency of lens defect detection is poor, detection personnel need long-term training, and the inconsistency probability of detection results of different personnel is high; 2. high cost, requiring the employment of a large amount of human labor for inspection and occupying a large amount of factory space. 3. The detection speed is slow, and a skilled worker can only detect 3-4 sheets per minute. Therefore, the traditional detection mode is urgently needed to be replaced by high-efficiency and high-accuracy automatic detection equipment.
The automatic detection of optical lenses needs to overcome the following difficulties: 1. the surface of the optical lens is spherical, and the defects are shot and processed by the traditional camera machine vision, so that the optical lens is only suitable for planes or spherical surfaces with large curvature radius. 2. The optical lens surface defects are small in size, typically on the order of microns. 3. The detection speed is high, and the detection speed can exceed the speed of manual detection and can reach more than 5 sheets per minute.
CN103926257A discloses a lens defect detection method based on a terahertz time-domain spectrometer, which adopts the terahertz time-domain spectrometer to scan a lens to be detected line by line, analyzes an absorption coefficient according to a reflection coefficient and a transmission coefficient of a scanning point, and judges whether the lens is a defect, and the method is difficult to detect a tiny defect due to low resolution of terahertz waves and has high cost; CN107741430A discloses a lens detection system based on Contact Image Sensor (CIS), which is low in cost, but is only suitable for detecting lens defects with large curvature radius, and because of the influence of the curvature radius of the lens, the edge definition is lower than the center definition; CN111307421A discloses a defect detection method based on telecentric lens, which utilizes an annular light source and a backlight light source to respectively build dark field and bright field environments, and a stepping motor drives the telecentric lens to shoot and detect defects layer by layer on a lens.
Therefore, a system and a method for detecting the defects of the spherical curved surface are designed to solve the technical problems.
Disclosure of Invention
The invention aims to provide a detection system and a detection method for defects of a spherical curved surface, which solve the problems that in the prior art, the surface of an optical lens is a spherical surface, defects are shot and processed only by the vision of a traditional camera machine and are only suitable for the spherical surface with a plane or a large curvature radius, the size of the defects on the surface of the optical lens is small, the detection precision is low and the detection efficiency is low in a micron order.
The technical scheme adopted by the invention is as follows:
a spherical curved surface defect detection system, comprising:
the clamping and rotating module is used for clamping and rotating the measured lens;
the detection module is used for detecting the spherical curved surface defect of the measured lens;
the detection module comprises a light source, a bright field imaging unit and a dark field imaging unit, wherein the light source is used for irradiating the surface of the measured lens, the bright field imaging unit is used for collecting reflected light on the surface of the measured lens, the dark field imaging unit is used for collecting scattered light on the surface of the measured lens, an optical axis of the dark field imaging unit and incident light of the light source form an included angle of 60 degrees, an optical axis of the bright field imaging unit and an optical axis of the dark field imaging unit form an included angle of 60 degrees, and an optical axis of the bright field imaging unit and incident light of the light source form an included angle of 120 degrees.
Further, the bright field imaging unit comprises a bright field receiving lens and a bright field detection element, the bright field receiving lens is used for receiving the reflected light of the surface of the measured lens, and the received reflected light converts an optical signal into an electric signal through the bright field detection element.
Further, the bright field detection element is a photoresistor or a photodiode.
Further, the dark field imaging unit comprises a dark field receiving lens and a dark field detection element, the dark field receiving lens is used for receiving the scattered light of the measured lens surface, and the received scattered light converts an optical signal into an electric signal through the dark field detection element.
Further, the dark field detection element is a photomultiplier tube or an avalanche diode.
The invention also provides a spherical bending surface defect detection method, which comprises the following steps:
s1: clamping a tested lens by using a clamping and rotating module, and enabling an optical axis of a dark field imaging unit in a detection module to coincide with a central axis of the clamping and rotating module, wherein a detection point of the detection module coincides with the upper surface of the tested lens;
s2: the clamping and rotating module clamps the measured lens and rotates by a central shaft of the clamping and rotating module, and meanwhile, the detection module deflects by a spherical center of the upper surface of the measured lens; or the clamping and rotating module clamps the measured lens to rotate around the central shaft of the clamping and rotating module, and meanwhile, the clamping and rotating module clamps the measured lens to deflect around the spherical center of the upper surface of the measured lens;
s3: an included angle of 60 degrees is formed between incident light of a light source and an optical axis of the dark field imaging unit, an included angle of 60 degrees is formed between the optical axis of a bright field imaging unit in the detection module and the optical axis of the dark field imaging unit, an included angle of 120 degrees is formed between the optical axis of the bright field imaging unit and the incident light of the light source, the light source emits collimated laser to irradiate the upper surface of the measured lens, light scattered by the upper surface of the measured lens is collected by a dark field receiving lens in the dark field imaging unit and converged on a dark field detection element in the dark field imaging unit, light reflected by the upper surface of the measured lens is collected by a bright field receiving lens in the bright field imaging unit and converged on a bright field detection element in the bright field imaging unit, and finally the dark field detection element and the bright field detection element convert optical signals into electric signals.
Further, in step S2, an included angle between a central axis of the clamping rotation module and an optical axis of the dark field imaging unit is a deflection angle θ, and a maximum deflection angle of the detection module
Wherein D is the measured lens effective aperture, and R is the curvature radius of the upper surface sphere of the measured lens.
Further, in the step S3, a distance from a detection point of the detection module to a spherical center of the upper surface of the measured lens is equal to a radius of curvature of the upper surface spherical surface of the measured lens.
The beneficial effects of the invention are:
1. the optical lens for detecting the spherical surface combines bright field imaging and dark field imaging, the bright field imaging can detect the large defects with strong mirror reflection such as dirt, large scratches and the like, the dark field imaging can detect the defects with strong surface scattering such as particles, pits and the like, meanwhile, the dark field imaging can detect the defects with smaller scale than the bright field imaging, can detect the micron-scale surface defects, is not only suitable for the spherical surface with a plane or a large curvature radius, but also suitable for the spherical surface with a small curvature radius, and has strong adaptability and high detection precision.
2. The invention divides the movement of the spherical surface detection system into the rotation movement of the detected lens and the deflection movement of the detection module or the detected lens, and the combination of the two movements scans the surface of the curved surface, thereby well solving the problem that the surface of the curved surface is difficult to detect at present.
3. Compared with the existing lens shooting by machine vision, in order to overcome the problem of limited depth of field, the lens needs to be divided into a plurality of small areas to be shot respectively, but a complex mechanical actuating mechanism is needed, and the lens needs to be stopped and moved to the next position for shooting after shooting one position. The invention is based on a point scanning mode, can rotate and scan the surface at high speed without stopping, and has the advantages of higher efficiency, high detection precision, high detection speed, high consistency of lens defect detection and strong practicability.
Drawings
FIG. 1 is an explanatory view of embodiment 1 of the present invention;
FIG. 2 is an explanatory view of embodiment 1 of the present invention;
FIG. 3 is an explanatory view of embodiment 1 of the present invention;
FIG. 4 is an explanatory view of embodiment 1 of the present invention;
FIG. 5 is an explanatory view of embodiment 1 of the present invention;
FIG. 6 is an explanatory view of embodiment 2 of the present invention;
FIG. 7 is an explanatory view of embodiment 2 of the present invention;
FIG. 8 is an explanatory view of embodiment 2 of the present invention;
FIG. 9 is an explanatory view of embodiment 2 of the present invention;
FIG. 10 is a diagram showing an example of embodiment 3 of the present invention;
FIG. 11 is an explanatory view of embodiment 3 of the present invention;
FIG. 12 is an explanatory view of embodiment 3 of the present invention;
FIG. 13 is an explanatory view of embodiment 4 of the present invention;
FIG. 14 is an explanatory view of embodiment 4 of the present invention;
FIG. 15 is an explanatory view of embodiment 4 of the present invention;
FIG. 16 is a diagram illustrating an example of a comparative example of the present invention;
fig. 17 is an exemplary view for explaining the principle of the present invention.
Detailed Description
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. 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.
Example 1
Referring to fig. 1, a spherical curved surface defect detecting system includes a clamping rotation module 10, a detecting module 30, the detecting module 30 includes a light source 301, a bright field imaging unit and a dark field imaging unit, an optical axis of the dark field imaging unit forms an angle of 60 degrees with an incident light of the light source 301, an optical axis of the bright field imaging unit forms an angle of 60 degrees with an optical axis of the dark field imaging unit, an optical axis of the bright field imaging unit forms an angle of 120 degrees with an incident light of the light source 301, the bright field imaging unit includes a bright field receiving lens 304 and a bright field detecting element 305, the bright field detecting element 305 is a photoresistor, the dark field imaging unit includes a dark field receiving lens 302 and a dark field detecting element 303, and the dark field detecting element 303 is a photomultiplier.
m: a central shaft holding the rotary module 10; n: an optical axis of the dark field imaging unit; a: the detection module 30 is used for detecting the point on the upper surface of the detected lens 20; r: the spherical radius of the upper surface of the measured lens 20; o: an origin which coincides with the spherical center of the upper surface of the test lens 20.
The holding and rotating module 10 holds and fixes the measured lens 20 and rotates around m, which is coaxial with the central axis of the measured lens 20, at a variable angular velocity. In the initial position, n coincides with m, the upper surface of the lens 20 to be measured is a convex spherical surface, the center of the convex spherical surface coincides with O, and the height of the clamping and rotating module 10 is adjustable to adapt to the coincidence of the center of the circle with different spherical radius R and O. The detecting module 30 can deflect around the point O in the plane, and the distance OA between the detecting points A and O of the detecting module 30 on the upper surface of the detected lens 20 is adjustable to meet the detecting requirement of the spherical surfaces with different spherical radii R, L OA And (c) = R. In order to detect the whole surface of the lens to be detected, the whole surface of the lens to be detected needs to be scanned, specifically, the clamping and rotating module 10 clamps the lens to be detected 20 to rotate around a central axis m of the clamping and rotating module 10, and simultaneously, the whole detecting module 30 also deflects around a point O, and a deflection angle θ is an included angle between the central axis m of the clamping and rotating module 10 and an optical axis n of the dark field imaging unit, as shown in fig. 2. The rotation radius OA of the detection module 30 is consistent with the spherical radius R of the upper surface of the measured lens 20, so that the detection module 30 can realize non-defocusing detection at the detection point a of the upper surface of the measured lens 20 at any rotating position, and the detection precision is high. If the effective aperture of the measured lens is D, then
As shown in fig. 3. The detected lens 20 rotates to superpose the offset motion of the detection module 30, and the whole scanning track is a 3D spiral line, as shown in fig. 4 and 5, for the convenience of illustration, the curves in fig. 4 and 5 are relatively sparse.
The light source 301 emits a collimated laser beam to irradiate the point a, the light scattered by the upper surface of the test lens 20 is collected by a dark field receiving lens 302 in a dark field imaging unit and condensed on a dark field detecting element 303 in the dark field imaging unit, and the light reflected by the upper surface of the test lens 20 is collected by a bright field receiving lens 304 in the bright field imaging unit and condensed on a bright field detecting element 305 in the bright field imaging unit.
When the point a has no defect, only a small amount of light is scattered, most of the light is reflected, the light energy received by the dark field detection element 303 is small, and the dark field imaging unit corresponds to a dark point at the point a; the light energy received by the bright field detecting element 305 is strong, and the bright field imaging unit corresponds to a bright spot at the position of the a point. When there are defects such as pits, particles, etc. at the point a, light rays with energy two orders of magnitude higher than that of the defect-free point are scattered, only a small amount of light rays are reflected, and then the light energy received by the dark field detection element 303 is large, and at this time, the dark field imaging unit corresponds to a bright point at the point a; the bright field detector 305 receives less light energy, and the bright field imaging unit corresponds to a dark spot at the position of the a spot. Finally dark field detection element 303 and bright field detection element 305 convert the optical signal into an electrical signal.
Example 2
Referring to fig. 6, a spherical curved surface defect detecting system includes a clamping rotation module 10, a detecting module 30, the detecting module 30 includes a light source 301, a bright field imaging unit and a dark field imaging unit, an optical axis of the dark field imaging unit forms an angle of 60 degrees with an incident light of the light source 301, an optical axis of the bright field imaging unit forms an angle of 60 degrees with an optical axis of the dark field imaging unit, the bright field imaging unit forms an angle of 120 degrees with an incident light of the light source 301, the bright field imaging unit includes a bright field receiving lens 304 and a bright field detecting element 305, where the bright field detecting element 305 is a photodiode, the dark field imaging unit includes a dark field receiving lens 302 and a dark field detecting element 303, where the dark field detecting element 303 is an avalanche diode.
m: a central shaft holding the rotary module 10; n: an optical axis of the dark field imaging unit; a: the detection module 30 is used for detecting the point on the upper surface of the detected lens 20; r: the spherical radius of the upper surface of the test lens 20; o: an origin which coincides with the spherical center of the upper surface of the test lens 20.
The clamping and rotating module 10 clamps and fixes the measured lens 20 and rotates around m at a variable angular speed, wherein m is coaxial with the mechanical central axis of the measured lens 20. In the initial position, n coincides with m, the upper surface of the measured lens 20 is a concave spherical surface, the center of the concave spherical surface coincides with O, and the height of the clamping and rotating module 10 is adjustable to adapt to the coincidence of the center of the circle with different spherical radii R and O. The detecting module 30 can deflect around the point O in the plane, and the distance OA between the detecting points A and O of the detecting module 30 on the upper surface of the detected lens 20 is adjustable to meet the detecting requirement of the spherical surfaces with different spherical radii R, L OA = R. In order to detect the whole surface of the lens to be detected, the whole surface of the lens to be detected needs to be scanned, specifically, the clamping and rotating module 10 clamps the lens to be detected 20 to rotate around a central axis m of the clamping and rotating module 10, and simultaneously, the whole detecting module 30 also deflects around a point O, and a deflection angle θ is an included angle between the central axis m of the clamping and rotating module 10 and an optical axis n of the dark field imaging unit, as shown in fig. 7. The rotation radius OA of the detection module 30 is consistent with the spherical radius R of the upper surface of the measured lens 20, so that the detection module 30 can realize non-defocusing detection at the detection point a of the upper surface of the measured lens 20 at any rotating position, and the detection precision is high. If the effective aperture of the measured lens is D, then
As shown in fig. 8. The detected lens 20 rotates to superpose the offset motion of the detection module 30, and the whole scanning track is a 3D spiral line, as shown in fig. 9, for the convenience of display, the curve of fig. 9 is sparse.
The light source 301 emits a collimated laser beam to irradiate the point a, the light scattered by the upper surface of the test lens 20 is collected by a dark field receiving lens 302 in a dark field imaging unit and condensed on a dark field detecting element 303 in the dark field imaging unit, and the light reflected by the upper surface of the test lens 20 is collected by a bright field receiving lens 304 in the bright field imaging unit and condensed on a bright field detecting element 305 in the bright field imaging unit.
When the point a has no defect, only a small amount of light is scattered, most of the light is reflected, the light energy received by the dark field detection element 303 is small, and the dark field imaging unit corresponds to a dark point at the point a; the bright field detecting element 305 receives strong light energy, and the bright field imaging unit corresponds to a bright spot at the position of the a point. When there are defects such as pits, particles, etc. at the point a, light rays with energy two orders of magnitude higher than that of the case of no defects are scattered, only a small amount of light rays are reflected, and then the light energy received by the dark field detecting element 303 is large, and at this time, the dark field imaging unit corresponds to a bright point at the point a; the bright field detector 305 receives less light energy, and the bright field imaging unit corresponds to a dark spot at the position of the a spot. Finally dark field detecting element 303 and bright field detecting element 305 convert the optical signal into an electrical signal.
Example 3
Referring to fig. 10, a spherical curved surface defect detecting system includes a clamping rotation module 10, a detection module 30, the detection module 30 includes a light source 301, a bright field imaging unit and a dark field imaging unit, an optical axis of the dark field imaging unit forms an included angle of 60 degrees with an incident light of the light source 301, an optical axis of the bright field imaging unit forms an included angle of 60 degrees with an optical axis of the dark field imaging unit, an optical axis of the bright field imaging unit forms an included angle of 120 degrees with an incident light of the light source 301, the bright field imaging unit includes a bright field receiving lens 304 and a bright field detecting element 305, where the bright field detecting element 305 is a photoresistor, the dark field imaging unit includes a dark field receiving lens 302 and a dark field detecting element 303, where the dark field detecting element 303 is an avalanche diode.
m: a central shaft holding the rotary module 10; n: an optical axis of the dark field imaging unit; a: the detection module 30 is used for detecting the point on the upper surface of the detected lens 20; r: the spherical radius of the upper surface of the test lens 20; o: an origin which coincides with the spherical center of the spherical surface of the upper surface of the test lens 20.
The clamping and rotating module 10 clamps and fixes the measured lens 20 and rotates around m at variable angular speed, wherein m is coaxial with the mechanical central axis of the measured lens 20. In the initial position, n coincides with m, the upper surface of the lens 20 to be measured is a convex spherical surface, the center of the convex spherical surface coincides with the point O, and the height of the clamping and rotating module 10 is adjustable to meet the detection requirements of spherical surfaces with different spherical radii R, L OA And (c) = R. In order to detect the whole surface of the lens to be detected, the whole surface of the lens to be detected needs to be scanned, and the specific scanning manner is that the clamping and rotating module 10 clamps the lens to be detected 20 to rotate around a central axis m of the clamping and rotating module 10, meanwhile, the whole clamping and rotating module 10 also deflects around a point O, and the detection module 30 is kept still during the scanning process, and the deflection angle θ is an included angle between the central axis m of the clamping and rotating module 10 and an optical axis n of the dark field imaging unit, as shown in fig. 11. Because the center of the spherical surface of the upper surface of the measured lens 20 is at the point O, the clamping and rotating module 10 rotates around the point O as a whole, the distance OA from the detection point a of the detection module 30 on the upper surface of the measured lens 20 to the point O is consistent with the spherical radius R of the upper surface of the measured lens 20, and the detection point a of the detection module 30 can be on the spherical surface of the upper surface of the measured lens 20 at any rotating position, thereby realizing the detection without defocusing and having high detection precision. When the outer diameter position of the measured lens 20 is detected, the holding rotation module 10 reaches the maximum deflection angle θ max If the effective aperture of the measured lens is D, then
As shown in fig. 12. The rotation of the lens 20 superimposes its own deflection motion, and the detection module 30 is fixed, so that the whole scanning track is a 3D spiral.
The light source 301 emits a collimated laser beam to irradiate the point a, the light scattered by the upper surface of the test lens 20 is collected by a dark field receiving lens 302 in a dark field imaging unit and condensed on a dark field detecting element 303 in the dark field imaging unit, and the light reflected by the upper surface of the test lens 20 is collected by a bright field receiving lens 304 in the bright field imaging unit and condensed on a bright field detecting element 305 in the bright field imaging unit.
When the point a has no defect, only a small amount of light is scattered, most of the light is reflected, the light energy received by the dark field detection element 303 is small, and the dark field imaging unit corresponds to a dark point at the point a; the light energy received by the bright field detecting element 305 is strong, and the bright field imaging unit corresponds to a bright spot at the position of the a point. When there are defects such as pits, particles, etc. at the point a, light rays with energy two orders of magnitude higher than that of the case of no defects are scattered, only a small amount of light rays are reflected, and then the light energy received by the dark field detecting element 303 is large, and at this time, the dark field imaging unit corresponds to a bright point at the point a; the bright field detecting element 305 receives less light energy, and the bright field imaging unit corresponds to a dark spot at the position of the a point. Finally dark field detection element 303 and bright field detection element 305 convert the optical signal into an electrical signal.
Example 4
Referring to fig. 13, a spherical curved surface defect detecting system includes a clamping rotation module 10, a detection module 30, the detection module 30 includes a light source 301, a bright field imaging unit and a dark field imaging unit, an optical axis of the dark field imaging unit forms an included angle of 60 degrees with an incident light of the light source 301, an optical axis of the bright field imaging unit forms an included angle of 60 degrees with an optical axis of the dark field imaging unit, an optical axis of the bright field imaging unit forms an included angle of 120 degrees with an incident light of the light source 301, the bright field imaging unit includes a bright field receiving lens 304 and a bright field detecting element 305, where the bright field detecting element 305 is a photodiode, the dark field imaging unit includes a dark field receiving lens 302 and a dark field detecting element 303, where the dark field detecting element 303 is a photomultiplier.
m: a central shaft holding the rotary module 10; n: an optical axis of the dark field imaging unit; a: the detection module 30 is used for detecting the point on the upper surface of the detected lens 20; r: the spherical radius of the upper surface of the test lens 20; o: an origin which coincides with the spherical center of the spherical surface of the upper surface of the test lens 20.
The clamping and rotating module 10 clamps and fixes the measured lens 20 and rotates around m at variable angular speed, wherein m is coaxial with the mechanical central axis of the measured lens 20.In the initial position, n coincides with m, the upper surface of the lens 20 to be measured is a concave spherical surface, the center of the concave spherical surface coincides with the point O, and the height of the clamping and rotating module 10 is adjustable to meet the detection requirements of spherical surfaces with different spherical radii R, L OA And (c) = R. In order to detect the whole surface of the lens to be detected, the whole surface of the lens to be detected needs to be scanned, and the specific scanning manner is that the clamping and rotating module 10 clamps the lens to be detected 20 to rotate around a central axis m of the clamping and rotating module 10, meanwhile, the whole clamping and rotating module 10 also deflects around a point O, and the detection module 30 is kept still during the scanning process, and the deflection angle θ is an included angle between the central axis m of the clamping and rotating module 10 and an optical axis n of the dark field imaging unit, as shown in fig. 14. Because the center of the spherical surface of the upper surface of the measured lens 20 is at the point O, the clamping and rotating module 10 rotates around the point O as a whole, the distance OA from the detection point a of the detection module 30 on the upper surface of the measured lens 20 to the point O is consistent with the spherical radius R of the upper surface of the measured lens 20, and the detection point a of the detection module 30 can be on the spherical surface of the upper surface of the measured lens 20 at any rotating position, thereby realizing the detection without defocusing and having high detection precision. When the position of the outer diameter of the lens 20 is detected, the holding rotation module 10 reaches the maximum deflection angle θ max If the effective aperture of the measured lens is D, then
As shown in fig. 15. The rotation of the lens 20 superimposes its own deflection motion, and the detection module 30 is fixed, so the whole scanning track is a 3D spiral.
The light source 301 emits a collimated laser beam to irradiate the point a, the light scattered by the upper surface of the test lens 20 is collected by a dark field receiving lens 302 in a dark field imaging unit and condensed on a dark field detecting element 303 in the dark field imaging unit, and the light reflected by the upper surface of the test lens 20 is collected by a bright field receiving lens 304 in the bright field imaging unit and condensed on a bright field detecting element 305 in the bright field imaging unit.
When the point a has no defect, only a small amount of light is scattered, most of the light is reflected, the light energy received by the dark field detection element 303 is small, and the position of the dark field imaging unit at the point a corresponds to a dark point; the light energy received by the bright field detecting element 305 is strong, and the bright field imaging unit corresponds to a bright spot at the position of the a point. When there are defects such as pits, particles, etc. at the point a, light rays with energy two orders of magnitude higher than that of the defect-free point are scattered, only a small amount of light rays are reflected, and then the light energy received by the dark field detection element 303 is large, and at this time, the dark field imaging unit corresponds to a bright point at the point a; the bright field detecting element 305 receives less light energy, and the bright field imaging unit corresponds to a dark spot at the position of the a point. Finally dark field detection element 303 and bright field detection element 305 convert the optical signal into an electrical signal.
Comparative example
Referring to fig. 16, the principle of image shooting by using the conventional collector vision is shown in the figure, and in the application of the optical principle, an object plane and an image plane are conjugated with respect to an imaging lens, dotted lines in front of and behind the object plane are a foreground plane and a background plane respectively, the range between the foreground plane and the background plane is the depth of field, and the camera can shoot clearly in the range. In order to photograph smaller defects, the imaging lens is required to have a higher magnification, and the higher the magnification of the imaging lens, the smaller the depth of field. In the figure, the area 1 and the area 2 are within the visual field range of the camera, but because the curvature of the measured curved surface is larger, the two areas exceed the depth of field range of the imaging system, and therefore the camera cannot clearly image the area 1 and the area 2. Therefore, the traditional collector vision shooting image is not suitable for application scenes with high resolution and high curvature.
To better explain the detection principle of the present invention, see fig. 17, the present invention is based on point imaging, independent of the depth of field range. In addition, the point confocal technology can be used for point imaging, so as to further improve the resolution of the imaging system, for example, in the papers Measuring and interpolating point confocal functions to define a confocal micro resolution and an intensity quality control, the resolution is 0.51 lambda/NA by using the point confocal technology, the resolution of the point confocal imaging is not 0.61 lambda/NA, and the imaging resolution can be improved by 1.2 times.
In summary, the optical lens for detecting spherical surfaces of the present invention is not only suitable for planar surfaces or spherical surfaces with large curvature radius, but also suitable for spherical surfaces with small curvature radius, and has strong adaptability and high detection accuracy.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A spherical curved surface defect detection system, comprising:
the clamping and rotating module is used for clamping and rotating the measured lens;
the detection module is used for detecting the spherical curved surface defect of the measured lens;
the detection module comprises a light source, a bright field imaging unit and a dark field imaging unit, wherein the light source is used for irradiating the surface of the measured lens, the bright field imaging unit is used for collecting reflected light on the surface of the measured lens, the dark field imaging unit is used for collecting scattered light on the surface of the measured lens, an optical axis of the dark field imaging unit and incident light of the light source form a 60-degree included angle, an optical axis of the bright field imaging unit and an optical axis of the dark field imaging unit form a 60-degree included angle, and an optical axis of the bright field imaging unit and incident light of the light source form a 120-degree included angle.
2. The spherical curved surface defect detection system of claim 1, wherein said bright field imaging unit comprises a bright field receiving lens and a bright field detection element, said bright field receiving lens is configured to receive reflected light from said test lens surface, and said received reflected light is configured to convert an optical signal into an electrical signal via said bright field detection element.
3. The spherical curved surface defect detection system of claim 2, wherein said bright field detection element is a photo resistor or a photodiode.
4. The spherical curved surface defect detection system of claim 1, wherein said dark field imaging unit comprises a dark field receiving lens and a dark field detection element, said dark field receiving lens is configured to receive scattered light from said test lens surface, and said received scattered light is configured to convert an optical signal into an electrical signal by said dark field detection element.
5. The spherical curved surface defect detection system of claim 4, wherein said dark field detection element is a photomultiplier tube or an avalanche diode.
6. A spherical bending surface defect detection method is characterized by comprising the following steps:
s1: clamping a tested lens by using a clamping and rotating module, and enabling an optical axis of a dark field imaging unit in a detection module to coincide with a central axis of the clamping and rotating module, wherein a detection point of the detection module coincides with the upper surface of the tested lens;
s2: the clamping and rotating module clamps the measured lens and rotates by a central shaft of the clamping and rotating module, and meanwhile, the detection module deflects by a spherical center of the upper surface of the measured lens; or the clamping and rotating module clamps the measured lens to rotate around the central shaft of the clamping and rotating module, and meanwhile, the clamping and rotating module clamps the measured lens to deflect around the spherical center of the upper surface of the measured lens;
s3: an included angle of 60 degrees is formed between incident light of a light source and an optical axis of the dark field imaging unit, an included angle of 60 degrees is formed between the optical axis of a bright field imaging unit in the detection module and the optical axis of the dark field imaging unit, an included angle of 120 degrees is formed between the optical axis of the bright field imaging unit and the incident light of the light source, the light source emits collimated laser to irradiate the upper surface of the measured lens, light scattered by the upper surface of the measured lens is collected by a dark field receiving lens in the dark field imaging unit and converged by a dark field detection element in the dark field imaging unit, light reflected by the upper surface of the measured lens is collected by a bright field receiving lens in the bright field imaging unit and converged by a bright field detection element in the bright field imaging unit, and finally the dark field detection element and the bright field detection element convert optical signals into electric signals.
7. The method for detecting spherical curved surface defects of claim 6, wherein in step S2, the included angle between the central axis of the clamping rotation module and the optical axis of the dark field imaging unit is a deflection angle θ, and the maximum deflection angle of the detection module is
Wherein D is the effective aperture of the measured lens, and R is the curvature radius of the spherical surface of the upper surface of the measured lens.
8. The method as claimed in claim 6, wherein in step S3, the distance from the detecting point of the detecting module to the spherical center of the upper surface of the measured lens is equal to the radius of curvature of the upper surface of the measured lens.
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| CN116990320A (en) * | 2023-09-27 | 2023-11-03 | 江西驰宇光电科技发展有限公司 | Dark field imaging method and device for defect detection |
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| CN116990320A (en) * | 2023-09-27 | 2023-11-03 | 江西驰宇光电科技发展有限公司 | Dark field imaging method and device for defect detection |
| CN116990320B (en) * | 2023-09-27 | 2023-12-19 | 江西驰宇光电科技发展有限公司 | Dark field imaging method and device for defect detection |
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