US 12,241,844 B2
Method and system for detecting a defect on a semi-reflective film by illuminating different light sources along the same optical axis
Hsien-Te Hsiao, Tainan (TW); and Hsuan-Fu Wang, Tainan (TW)
Assigned to HUA YANG Precision Machinery Co., Ltd, Tainan (TW)
Filed by HUA YANG Precision Machinery Co., Ltd, Tainan (TW)
Filed on Mar. 27, 2023, as Appl. No. 18/126,624.
Claims priority of application No. 111133710 (TW), filed on Sep. 6, 2022.
Prior Publication US 2024/0077425 A1, Mar. 7, 2024
Int. Cl. G01N 21/88 (2006.01); G01N 21/47 (2006.01)
CPC G01N 21/8806 (2013.01) [G01N 2021/4735 (2013.01); G01N 2021/8848 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A defect detection method for illuminating a semi-reflective film using different light sources along a single optical axis, including the following steps:
preparing step (A) to prepare the semi-reflective film having an inspection surface to detect one or more defects of known coordinate positions in the semi-reflective film but unknown location as to locating on a front or back surface of the semi-reflective film by preparing a P-polarized light source and an S-polarized light source to illuminate the inspection surface along the optical axis, having an illumination angle between the optical axis and the inspection surface in a range of 5 and 45 degrees, and adjusting the illumination angle based on the surface reflectivity of the semi-reflective film so that a P-polarized light emitted by the P-polarized light source penetrates the inspection surface by over 30%, and an S-polarized light emitted by the S-polarized light source penetrates the inspection surface by less than 10%;
illuminating and imaging step (B) to sequentially illuminate and capture an image of the defects according to the coordinate positions using the P-polarized light source and S-polarized light source to illuminate the inspection surface, and using a camera module to capture one or more images for evaluation, with the camera module located on a normal line of the inspection surface of the semi-reflective film to cover the defects in a region according to the coordinate positions, wherein the captured images from the camera module are obtained based on the following conditions: when there are no defects on the front or back surface of the semi-reflective film, the P-polarized and S-polarized light as respectively emitted by the P-polarized source and the S-polarized light sources and reflected by the semi-reflective film will not enter the camera module; and
detecting and determining step (C) to use a computer in executing an evaluation logic to determine the captured images having the defects, with the evaluation logic having the following rules: for a defect, if there is the S-polarized light entering the camera module in the captured images, then the defect is determined to be located on the front surface of the semi-reflective film, and if there is a P-polarized light but no S-polarized light entering the camera module in the captured images, then the defect is determined to be located on the back surface of the semi-reflective film.