Three-dimensional measuring method based on binary grating out-of-focus projection

Abstract

The invention discloses a three-dimensional measuring method based on binary grating out-of-focus projection.The method comprises the steps that 1, a binary grating image is designed and generated by a computer; 2, the grating image is projected to a measured target in an out-of-focus mode through a projector; 3, a deformed grating image is collected with a camera and transmitted to the computer; 4, a principal value phase is obtained through a four-step phase-shifting method; 5, phase unwrapping is conducted on the principal value phase through a gray code method; 6, calibration is conducted on the camera and the projector, and three-dimensional coordinate information of the measured target is calculated according to a space intersection method.According to the three-dimensional measuring method based on binary grating out-of-focus projection, a binary grating needed by measurement is generated based on design of symmetry and periodicity of sine fringes, in different degrees of out-of-focus projection environments of the projector, the quality of phase information can be improved, and the three-dimensional measuring method is more suitable for out-of-focus projection three-dimensional measurement.

Description

technical field [0001] The invention belongs to the field of three-dimensional information reconstruction, and in particular relates to a defocused projection three-dimensional measurement method. Background technique [0002] Optical three-dimensional measurement technology can accurately obtain three-dimensional data of objects, which can be used for three-dimensional model reconstruction, object surface contour measurement, detection of size and shape parameters in industrial environments, etc. There are broad application prospects in the fields of industrial product design, art sculpture and cultural relics protection. [0003] The grating projection method is an important three-dimensional measurement technology. By projecting a sinusoidal grating to the surface of the object, the height information of the object is modulated in the grating in the form of phase, and the grating fringe image of the object surface is obtained by using a CCD camera, and the fringe analysis...

AI Technical Summary

Problems solved by technology

However, when the binary square wave grating is defocused, a large number of high-order harmonics are generated, which greatly affects the quality of the grating. In addition to the limitation of the defocusing degree of the projector, when the period of the binary square wave grating is large, it is difficult for the projector to The approximate sinusoidal grating can be obtained by defocusing, and high-precision measurement cannot be performed

Pulse width modulation (PWM) is used to reduce the influence of high-frequency harmonics on the quality of the grating when defocusing, but this modulation is optimized in one-dimensional direction, and the effect is poor when the grating period is large

Although the dithering technique solves the problem of poor quality of wide-period fringes, it is difficult to deal with the design of narrow-period binary gratings

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