Color speckle deflectometry for three-dimensional surface transient measurement

Abstract

Transient measurement technology has broad application prospects in fields such as mirror processing, automotive painting, and precision mechanical processing. It can help us monitor and analyze instantaneous changes in the processing process in real-time. The existing contact and non-contact measurement methods have drawbacks in both non-destructive testing and transient measurement directions. This paper develops a transient measurement system for color speckle deflectometry, aiming to improve efficiency in the field of optical measurement. The core components of the system described in this paper include a liquid crystal display (LCD) screen, a camera, and a beam splitter. By using multi-channel speckle fusion and color correction, one color image is captured to achieve the same effect as the previous three monochromatic images. The gradient of each point on the surface under test (SUT) is obtained through speckle shift, and then the surface shape of the SUT is obtained through integration. The feasibility is verified by the actual measurement with a flat mirror. By utilizing these devices and methods, transient measurement of the three-dimensional shape of a mirror can be achieved, and reliable results can be obtained in both laboratory environments and processing sites. Compared with traditional measurement methods, this system not only has a significant improvement in measurement speed, but also can achieve non-destructive and in place measurement.