Search

CN-121994708-A - Defect detection method and defect detection system for specular reflector

CN121994708ACN 121994708 ACN121994708 ACN 121994708ACN-121994708-A

Abstract

The invention discloses a defect detection method and a defect detection system for a specular reflection object, wherein the specular reflection object is arranged near the critical distance of fringe disappearance, and the local z-axis displacement caused by the curved surface of the defect The Z/slope change (local asperity) will destroy the original fringe cancellation adjustment, which will make direct measurement of the geometric displacement difficult Z conversion into optical parameter variation capable of being precisely controlled and quantized, thereby realizing the control of High sensitivity differential measurement of Z, to detect defects sensitively and at lower cost. Meanwhile, the surface defect information (such as concave-convex points and scratches) of the high-frequency stripes is automatically filtered by utilizing the inherent spatial frequency filtering characteristic of the stripe cancellation phenomenon, so that the defect measurement result is more accurate and reliable, the requirement on the quality of the stripes is low, and the cost is lower.

Inventors

  • TAN ENCHENG
  • WANG LEI
  • LI SHANSHAN

Assignees

  • 厦门威芯泰科技有限公司

Dates

Publication Date
20260508
Application Date
20260326

Claims (6)

  1. 1. The defect detection method of the specular reflection object is characterized by comprising the following steps of: Projecting a plurality of black and white stripes which are alternately arranged in turn onto the surface of a specular reflector (1); enabling the aperture of the telecentric lens (3) to receive even pairs of black and white stripes; And enabling the camera (5) with the telecentric lens (3) to receive signals reflected by the surface of the specular reflection object (1), obtaining an image with a gray value of a first gray level if the surface of the specular reflection object (1) has no defects and generates a fringe cancellation phenomenon, and displaying the image with fringes at the positions of the concave-convex defects if the surface of the specular reflection object (1) has the concave-convex defects.
  2. 2. A method of defect detection of specular reflectors according to claim 1, wherein the telecentric lens (3) has an aperture that allows continuous variation.
  3. 3. A method for detecting defects in a specular reflector as set forth in claim 2, wherein said aperture is size-switched by an electrodynamic diaphragm.
  4. 4. A method for defect detection of a specular reflector according to claim 1, wherein the optical path distance from the light source (10) to the specular reflector (1) is adjustable.
  5. 5. A defect detection method is characterized in that an object to be detected is placed on a critical distance of fringe disappearance, an image is obtained through a telecentric lens (3), when the object to be detected has concave-convex defects, the fringe cancellation phenomenon is destroyed, and the position of the concave-convex defects displays the image with the fringes.
  6. 6. Defect detection system, characterized in that it is adapted to perform a method for defect detection of a specular reflection object (1) according to any one of claims 1-4, comprising A light source (10) having a striped light transmitting sheet thereon to form a plurality of black and white stripes alternately arranged in sequence; A beam splitter (2) adapted to transmit a signal reflected by the surface of the specular reflector (1) and to reflect light from the light source (10) to the surface of the specular reflector (1); And a camera (5) on which a telecentric lens (3) is mounted for imaging.

Description

Defect detection method and defect detection system for specular reflector Technical Field The invention relates to the field of appearance detection, in particular to a defect detection method and a defect detection system for a specular reflector. Background When detecting the surface defects of the specular reflection object, the curvature can be detected by detecting the distortion on the raster image, the defects are easily influenced by the defects, the method detects the defects by means of the sharp jump of the stripes, the requirements on a gradient operation algorithm are high, namely the defect detection is very dependent on the quality of the stripes, the detection requirements are high, the cost is increased, and the inherent bright and dark stripes on the imaging are caused, so that the algorithm processing and the synchronous detection of other non-concave-convex defects are not facilitated. Disclosure of Invention The present invention is directed to overcoming or providing a material basis for overcoming the above-mentioned drawbacks or problems in the prior art, and providing a method and a system for detecting defects of specular reflectors. To achieve the above object, the present invention and its preferred embodiments adopt the following technical solutions but the embodiments are not limited to the following solutions: in a first aspect, a method for detecting defects of a specular reflector includes the steps of: projecting a plurality of black and white stripes which are alternately arranged in sequence onto the surface of the specular reflector; Enabling the aperture of the telecentric lens to receive even pairs of black and white stripes; And enabling the camera with the telecentric lens to receive the signal reflected by the surface of the specular reflection object, if the surface of the specular reflection object has no defect, generating a fringe cancellation phenomenon, obtaining an image with a gray value of a first gray scale, and if the surface of the specular reflection object has a concave-convex defect, displaying the image with fringes at the position of the concave-convex. In a second aspect, based on the first aspect, the telecentric lens has an aperture that allows continuous variation. Based on the third scheme, the aperture is switched in size through the electric diaphragm. In a fourth aspect, based on the first aspect, an optical path distance from the light source to the specular reflector may be adjustable. In the fifth scheme, in the defect detection method, an object to be detected is placed on a critical distance of fringe disappearance, when an image of the object to be detected is obtained through a telecentric lens and the object to be detected has concave-convex defects, the fringe cancellation phenomenon is destroyed, and then the position of the concave-convex defects displays the image with the fringes. A sixth aspect is a defect detection system adapted to perform a method for detecting a defect of a specular reflector as set forth in any one of the first to fourth aspects, which comprises A light source, on which a stripe light-transmitting sheet is arranged to form a plurality of black-white stripes which are alternately arranged in turn; a beam splitter adapted to transmit a signal reflected by the surface of the specular reflector and adapted to reflect light from the light source to the surface of the specular reflector; a camera carrying telecentric lens imaging. As can be seen from the above description of the present invention and the preferred embodiments thereof, compared with the prior art, the technical solution of the present invention and the preferred embodiments thereof have the following beneficial effects due to the following technical means: Placing specular reflectors near the critical distance for fringe extinction, localized z-axis displacement due to the curvature of the defect Z will destroy the original destructive adjustment of the fringes, which will make it difficult to directly measure the geometrical displacementZ conversion into optical parameter variation capable of being precisely controlled and quantized, thereby realizing the control ofHigh sensitivity differential measurement of Z, to detect defects sensitively and at lower cost. Meanwhile, the surface defect information (such as concave-convex points and scratches) of the high-frequency stripes is automatically filtered by utilizing the inherent spatial frequency filtering characteristic of the stripe cancellation phenomenon, so that the defect measurement result is more accurate and reliable, the requirement on the quality of the stripes is low, and the cost is lower. And the imaging scheme for the transmission mode and the reflection mode has the fringe disappearance rule. The stripes with different stripe slices and different cycle sizes have the stripe disappearance rule. Aiming at different apertures of the telecentric lens, different aperture switching mode