A Calibration Method for 3D Topography Measurement System Based on Telecentric Imaging

Abstract

The present invention provides a method for calibrating a three-dimensional shape measurement system for telecentric imaging, comprising: step S1: building a telecentric three-dimensional shape measurement system; S2: controlling a telecentric projection device to project a sinusoidal fringe pattern on a translation platform, and taking a telecentric camera The equipment collects the sinusoidal fringe pattern; the translation platform is moved multiple times, and the absolute phase value at the pixel point for calibration on the image plane of the telecentric camera equipment is obtained by using the multi-step phase shift method, and the absolute phase value at the pixel point for calibration and the height Values ​​are linearly fitted to obtain the phase-height conversion relation of the measurement system; S3: By calibrating the parameters of the telecentric camera device, the pixel coordinates on the image plane of the telecentric camera device are converted into world coordinates. In the present invention, the phase and the height satisfy the linear relationship, and only need to measure the linear relationship between the absolute phase value of one pixel point and the height of the translation platform, the calculation amount is small, the accuracy is high, the operability is strong, and the practicability is strong; in addition, the present invention The invention also provides an orthographic transformation model of the object-image bi-telecentric lens, which simplifies the calibration process.

Description

technical field [0001] The invention belongs to the fields of three-dimensional data imaging and optical three-dimensional reconstruction, and in particular relates to a calibration method for a three-dimensional shape measurement system of telecentric imaging. Background technique [0002] In the 3D shape measurement system, the 3D shape measurement method based on projected sinusoidal fringe structured light is widely used due to its simple principle, fast calculation speed and high measurement accuracy, including phase detection profilometry and Fourier transform profilometry, etc. . The reference fringe pattern can be obtained by projecting the sinusoidal fringe pattern on the reference plane by the projector. When the object to be tested is placed on the reference plane, the deformed fringe pattern can be obtained. From the two fringe patterns, the 2D absolute phase difference can be obtained, and then the measured object’s phase difference can be obtained. 3D depth in...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to provide a calibration method for a three-dimensional shape measurement system of telecentric imaging, which solves the problem that the calibration of the three-dimensional shape measurement system in the prior art is complicated, and some parameters are difficult to accurately calibrate, thus affecting the three-dimensional shape measurement system. Accuracy and other issues

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