Method for fast recovering surface phase of high-light object based on least square method

Abstract

The invention provides a method for fast recovering a surface phase of a high-light object based on the least square method. The method is different from an original method that valid gray values and invalid gray values in N optical grating pictures are directly substituted into a standard N-step phase shifting formula to solve the phase. The method comprises the steps that firstly, invalid pixel points and invalid gray values are removed, valid gray values of valid pixel points are directly used, a linear equation set is established according to the valid gray values, the optimal solution of the equation set is solved based on the least square method, the high-precision phase value is solved according to the optimal solution, and the phase value of the surface of the high-light object can be fast recovered. The method is simple in step, high in robustness and good in random error rejection capability, extra hardware facilities are not needed, the diaphragm and exposure time of a CCD camera do not need to be adjusted, the surface of the high-light object does not need to be processed, time is saved, the operation is fast, the measuring precision of the surface of the high-light object can be guaranteed, and the measuring accuracy is high.

Description

technical field [0001] The invention belongs to the related field of optical three-dimensional measurement, and relates to a method for quickly acquiring the surface phase of high-gloss objects such as metals in three-dimensional measurement of structured light. Surface Phase Fast Recovery Method. Background technique [0002] Projected grating phase method is a non-contact full-field three-dimensional measurement technology based on structured light, which is widely used in the fields of three-dimensional topography measurement, reverse engineering and quality inspection of industrial product surfaces; it mainly adds phase to the surface of objects by projecting sinusoidal structured light Information, and then the height information of the object surface is mapped by the acquired phase information. The measurement steps include digital grating projection, fringe image acquisition, phase recovery and expansion, object depth information acquisition and three-dimensional rest...

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Problems solved by technology

For example, the patent "A Stereo Vision Inspection Method for Three-dimensional Shape Measurement of Strongly Reflective Surfaces, Application No.: 200910236214.8" applied by Beihang University uses this method, but multiple exposures take a lot of time and cannot meet real-time requirements. In addition, if the exposure time is different, the corresponding quantization error is also different. In addition, too small aperture will reduce the effective quantization level of the image. The final phase map is fused with the results of different quantization error levels, and the measurement accuracy will be affected. influences

In addition, it was also proposed to spray a certain powder on the surface with strong reflection to make the measured object present diffuse reflection characteristics, which is beneficial to optical three-dimensional measurement, but the unevenness of the powder increases the measurement error. In industrial inspection and automatic control processing, this kind of The realization of the method is also very difficult. Many objects, such as clothing industry, art sculptures, cultural relics, etc., do not allow their surface to be processed when the three-dimensional shape is restored.

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