Comprehensive introduction

3D surface detection of transparent materials is always considered to be a challenging problem. The difficulty is that most light, when it encounters a transparent material, passes directly through the surface and is refracted. In addition, the environmental background will affect the detection by imaging on the surface of the transparent material. The most obvious solution is to spray a powder or dye on the surface of a transparent material to make it opaque. However, there are various disadvantages such as subsequent cleaning, and the thickness and uniformity of the surface powder or dye can easily affect the detection.

Key points of innovation

A simultaneous detection system and method for 3D surface and thickness distribution of large area and thickness transparent material are provided. Based on the physical model of polarized light, an industrial camera is used to collect polarizing images of the surface of a transparent material with large area and thickness by means of a rotatable linear polarizer with a scale. The relationship between pixel gray value and rotation angle of linear polarizer is obtained by fitting each pixel of polarization image. A TOF depth sensor is used to determine the correspondence between refracted light and surface normals. Specifically, the unique azimuth Angle is determined and used to correct the polarization normal vector by combining gray code encoding and decoding with baseline method, so as to reconstruct the whole three-dimensional surface for detection. The thickness distribution of large area transparent material surface is also measured to realize thickness detection.

Technical index

The whole three-dimensional surface is reconstructed to realize the detection. The thickness distribution of large area transparent material surface is also measured to realize thickness detection.