A method to reduce the number of projected images based on multi-frequency phase shift

A technology of projecting images and multi-frequency phase shifting, which is applied in the direction of measuring devices, instruments, and optical devices, etc., can solve the problems of reduced efficiency and increased measurement time, so as to improve installation accuracy, reduce the number of projections, and reduce the number of projected images Effect

Active Publication Date: 2020-09-29
HUAZHONG UNIV OF SCI & TECH
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  • Description
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Problems solved by technology

[0006] However, PMP needs to measure multiple points. Due to the large number of measured points, there is also a lot of data to be processed, which increases the measurement time and reduces the efficiency.

Method used

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  • A method to reduce the number of projected images based on multi-frequency phase shift
  • A method to reduce the number of projected images based on multi-frequency phase shift
  • A method to reduce the number of projected images based on multi-frequency phase shift

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Embodiment 1

[0034] Such as figure 1 and figure 2 Shown, a kind of method of reducing projection image quantity based on multi-frequency phase shift of the present invention comprises the following steps:

[0035] S101. Project a series of standard sinusoidal fringe images with the same phase onto the target surface to form a deformed grating on the surface of the object. Two cameras capture the image information of the deformed grating at the same time, and establish a light intensity distribution function of the deformed grating image:

[0036]

[0037] Among them, (x, y) represents the pixel coordinates, I ji (x,y) is the grayscale of the ith deformed grating image at the jth frequency, A(x,y) is the average grayscale, B(x,y) is the grayscale modulation, δ ji is the phase shift of the image, is the relative phase value to be calculated;

[0038] S102, using the m-frequency N-step phase shift method to solve That is, the grating is shifted by 1 / N of the grating pitch in the ve...

Embodiment 2

[0042] On the basis of Embodiment 1, this embodiment adopts the three-frequency four-step phase shift method to solve When N=4, the light intensity distribution function of each step is obtained as:

[0043]

[0044]

[0045]

[0046]

[0047] Simultaneous formula (2) to formula (5), get where I 1 (x,y), I 1 (x,y), I 1 (x,y) and I 1(x, y) respectively represent the gray levels of the four deformed grating images. If using the traditional method, i.e. sampling m*N+1 times, you need to sample 13 times, one of which is the reference deformed grating image of a simple light source; and using the method of this embodiment, you only need to sample 8 times, one of which is As a reference deformed grating image of a simple light source, the time required for the sampling process in this embodiment is reduced by 38.5% without affecting the measurement accuracy.

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Abstract

The invention provides a method for reducing a number of projected images based on multi-frequency phase shift. When N is an even number, the principle that an i-th deformed grating image and an (i+N / 2)-th deformed grating image at the same frequency are complementary and mutually replaced is utilized to reduce a number of sampling times from m*N+1 to m*N / 2+1, the number of the projected images isreduced, and the time of the measurement process is shortened; the method can reduce the number of required productions, further shortens the projection time; and the method improves the mounting precision of a measuring platform and an optical system, thereby providing the possibility of achieving higher measurement precision with fewer images.

Description

technical field [0001] The invention relates to the field of three-dimensional optical measurement, in particular to a method for reducing the number of projected images based on multi-frequency phase shifting. Background technique [0002] With the development of automatic control technology, three-dimensional measurement has been widely used in more and more fields such as aerospace, weaponry and automobile manufacturing. However, some core components in the forging industry usually have complex structures, irregular curved surfaces, and high precision requirements, so most of them still use manual calipers and templates for inspection. With the development of area array CCD camera and digital projection technology, phase measurement profilometry (PMP) and phase shift interferometry (PSI) have developed rapidly and have been widely used in mutual integration. PMP has the following three characteristics: [0003] (1) The phase value of each point is only related to the li...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01B11/25
CPCG01B11/2527G01B11/254
Inventor 李中伟钟凯张攀张禹泽李蹊何文韬郑鸿辉
Owner HUAZHONG UNIV OF SCI & TECH
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