Binary grating projection defocusing degree evaluation method based on image difference and LM iteration

Abstract

The invention discloses a binary grating projection defocusing degree evaluation method based on image difference and LM iteration, which comprises the following steps of: adjusting parameters of a projector output grating before testing; in the test process, differential operation is firstly carried out on images acquired by a camera, and then iterative operation is carried out on the differential images by an LM method aiming at a sinusoidal target function; and acquiring absolute errors of data at each point of the image and an actual image when the iteration is ended, and correcting the absolute errors by using image gray scale range to reduce a fluctuation error. The binary grating projection defocusing degree evaluation method based on image difference and LM iteration evaluates thedefocusing degree from the perspective of experiments, and has the advantages of high accuracy of defocusing degree judgment, simple required equipment, convenience, practicability, real-time displayand the like.

Description

Technical field [0001] The invention relates to the field of optical measurement experiment solid mechanics, in particular to a method for evaluating defocusing degree of binary grating projection based on image difference and LM iteration. Background technique [0002] In the field of photometric mechanics, the grating projection method is a basic optical topography measurement method. The raster projection method directly uses the phase distortion information of the modulated raster to obtain the three-dimensional information of the object, uses a mathematical method to demodulate the phase, and can automatically determine the unevenness of the object. Therefore, image processing is easy to realize automation, and has high precision and sensitivity. [0003] In order to facilitate the measurement, in the raster projection method, the projector projects a two-dimensional structure pattern (striped pattern) instead of a 3D sinusoidal pattern, and then the binary pattern is blurred...

AI Technical Summary

Problems solved by technology

There are however some problems with the binary defocus technique: if the degree of defocus is too small, the pattern is not sinusoidal and contains many higher harmonics

The non-sinusoidal structure is caused by high-order harmonics in the binary defocusing technique, which introduces errors into the demodulation phase, which reduces the accuracy of 3D measurements

In addition, in practical applications, if you want to improve the accuracy of measurement, you must consider the problem that the received image has certain non-sinusoidal characteristics due to the β distortion of the electronic device itself.

Such problems affect the accuracy of measurement and are not conducive to the development of high-precision photomechanics

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