Projector calibration method based on double four-step phase shift

Abstract

The invention relate to a projector calibration method based on double four-step phase shift. The method comprises the following steps that 1) a calibration board is selected; 2) a projector calibration system is established; 3) an image of the calibration board is shot by a camera; 4) a DLP projector projects horizontal and vertical sine stripes onto the calibration board, and images formed on the calibration board are shot; 5) the step 4) is repeated to obtain a group of 4 horizontal images and a group of 4 vertical images; 6) phase extraction is carried on the two groups of horizontal images and two groups of vertical images, obtained in the steps 4) and 5) respectively, in the four-step phase shift method to obtain two horizontal phase principal-value images and two vertical phase principal-value images, and every two principal-value images in the same direction are overlapped to obtain an overlapped phase principal-value image; 7) phase expansion is carried out on each overlapped phase principal-value image obtained in the same direction to obtain a phase expansion image; and 8) absolute horizontal and vertical phases are obtained via the phase expansion images, and a pixel coordinate (mu, theta) of a corresponding point in a projector pixel coordinate is obtained, and the projector is calibrated.

Description

technical field [0001] The invention belongs to phase measurement profilometry in the field of machine vision. Background technique [0002] In the field of machine vision, structured light measurement method is the main three-dimensional stereo vision measurement method, which has the advantages of non-contact, high precision and fast speed. It has been widely developed in industrial testing, reverse engineering, film and television special effects production, medicine, cultural relics protection, etc. Before using the structured light 3D measurement system composed of single camera and single projector, the camera and projector need to be calibrated. [0003] The camera calibration method and technology are relatively mature, but the projector calibration is not satisfactory. The existing calibration methods of projectors can be generally divided into two categories: one is to calibrate the camera first, and then use the calibration parameters of the camera to calibrate ...

AI Technical Summary

Problems solved by technology

Li Zhongwei and others proposed a solution to the above problems. Firstly, the horizontal and vertical sinusoidal grating stripes were projected to the calibration plate and photographed, and then the phase was extracted from the image. A phase compensation lookup table was established, and the phase error was calculated for the extracted phase. Compensation solves the phase error caused by the non-sinusoidalization of fringes. This method improves the calibration accuracy very well, but the operation of establishing an error lookup table is complicated and time-consuming, which is not conducive to the rapidity requirements of 3D measurement.

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