Heterodyne three-frequency unequal range phase displacement solution phase method

Abstract

The invention relates to a heterodyne three-frequency unequal range phase displacement solution phase method, and the method is as follows: selecting three frequencies, firstly adopting four-step phase shift method to obtain the package phase and average light intensity of the middle frequency, adopting two-step phase shift method to obtain the package phase corresponding to the two frequencies under the condition with known light intensity, obtaining the true phase according to the heterodyne method, adopting the contour line sine and cosine filtering method in the optical grating projection three-dimensional measurement, using stripe direction information for filtering the package phase on isophasal line, the method uses less projection picture for exactly measuring and uses the stripe direction information for filtering the package phase picture for effectively removing the inconsistent points in the package phase picture, the heterodyne three-frequency unequal range phase displacement solution phase method is used in the phase method three-dimensional shape measurement for effectively raising the measuring efficiency and measuring accuracy.

Description

technical field [0001] The invention belongs to the technical field of image processing, and in particular relates to a heterodyne three-frequency unequal step phase shifting method for phase resolution, which can efficiently and accurately acquire three-dimensional information of an object. Background technique [0002] The grating projection three-dimensional measurement technology is a method to accurately measure three-dimensional contours by using phase information. At present, the methods for obtaining phase mainly include phase shift method and Fourier transform contour method. The phase-shifting method is widely used because of its high accuracy, high resolution, and insensitivity to changes in object surface reflectance. The method calculates the package phase value containing the deformation information of the measured object surface by collecting multiple frames of phase-shifted fringe images. Since the wrapped phase value is in the interval [-π, π], in order to ...

AI Technical Summary

Problems solved by technology

However, due to the nonlinear output of the projection system, electronic noise interference in the camera equipment, and environmental noise, there is a lot of noise in the gray distribution of the encoded pattern, which will cause errors in phase recovery and affect discontinuity. 3D reconstruction of object surfaces

In the process of using the optimization algorithm to reduce the phase error, it is first necessary to perform nonlinear correction on the projection system, but the correction process takes a lot of time, and the gamma value of the projector is required to be relatively fixed

Secondly, it is necessary to compensate the phase error. The method based on spline fitting needs to go through multiple iterations in the phase calculation, and the calculation amount is large; the method based on the lookup table needs to store the pre-calculated phase error value in a lookup table. It is used to compensate the error. The process of calculating the phase error takes a lot of time and the method has relatively high environmental requirements; the method based on image filtering can filter the phase image in ordinary frequency domain or space domain, which can greatly eliminate noise and reduce phase error. However, for surfaces with height jumps, the object boundary jump information will be lost

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