Device and method of measuring surface topographies of mirror and mirror-like objects

Abstract

The invention discloses a method and a device for measuring surface topographies of mirror and mirror-like objects. Phase measurement deflectometry is adopted to measure mirror and mirror-like surface shapes, a combination between a liquid crystal display and a planar mirror serves as a calibration plate, the liquid crystal display is fixed and can not move, the planar mirror moves freely for four times, an image reflected by the planar mirror is photographed by a CCD detector, linear solution and beam method adjustment are then used for completing calibration on inner parameters of the camera, global pose estimation is used for completing calibration on the relative relation between the liquid crystal display and the camera, and finally, a three-dimensional topography of a to-be-detected mirror surface is calculated and obtained through a gradient integral of the phase measurement deflectometry. According to the device and the method of the invention, defects that the calibration plate is needed and a precise positioning control point is attached to the planer mirror during the calibration process in the traditional method are overcome, the measurement cost is low, and he measurement speed is quick; and constraint conditions such as rotation matrix orthogonality during a perspective imaging process and a fourier transform method are introduced for corresponding point matching, and influences by high noise and multiframe processing on three-dimensional topography recovery can be overcome.

Description

technical field [0001] The invention belongs to the technical field of object surface topography measurement, in particular to a device and method for measuring the surface topography of mirror surfaces and mirror-like objects. Background technique [0002] With the increasing application of highly reflective objects in industrial production, such as free mirrors in optical components, automotive metal bodies, solar mirrors, etc., accurate measurement and evaluation of the three-dimensional surface shape of mirrors and mirror-like surfaces has become an important tool for improving the processing surface. An important research content of quality and performance. However, due to the characteristic of specular reflection on the surface of highly reflective objects, it is difficult for the traditional computer vision-based 3D shape measurement technology to measure the surface shape of mirror objects. [0003] The existing three-dimensional shape measurement methods of highly ...

AI Technical Summary

Problems solved by technology

[0004] The traditional deflectometry calibration method is to first use the calibration board to calibrate the internal parameters of the camera, then use a high-precision flat mirror or a laser tracker with control points to complete the pose evaluation between the LCD display and the camera, and finally use the light beam The calibration parameters are optimized by the method of adjustment. Since the coordinates of the control points on the plane mirror need to be precisely positioned by photogrammetry or other methods, the cost of the laser tracker is expensive, and the beam adjustment process is a local optimization algorithm. Obviously, the commonly used calibration methods will increase. Measuring cost, no guarantee of convergence of optimization

The matching of homonymous points is generally completed by the phase shift algorithm based on the fringe pattern. Since the out-of-focus shooting of the camera does not affect the phase extraction process of the sinusoidal coded pattern, the phase matching using the fringe pattern has the advantages of high matching accuracy and high spatial resolution. However, The phase shift algorithm requires multiple phase shifts and repeated shooting. Obviously, this multi-frame processing process is not conducive to real-time rapid measurement

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