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Method for measuring low-pass filtering characteristics of binary fringe defocusing projection system

A binary fringe and projection system technology, which is applied in the direction of measuring devices, instruments, and optical devices, can solve the problems of low-pass filtering characteristics and the inability to meet the measurement requirements of projection objectives, and achieve the effect of convenient collection process and simplified detection steps

Active Publication Date: 2019-04-05
BEIJING INSTITUTE OF TECHNOLOGYGY
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Problems solved by technology

[0009] The purpose of the present invention is to solve the problem that the projection lens needs to be disassembled when testing the modulation transfer function of the projection system, and usually can only be measured under the condition of infinite object distance, which cannot meet the measurement requirements of the projection system projection objective lens with limited object distance and image distance. , a new method for measuring the low-pass filter characteristics of binary fringe defocused projection systems is proposed

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  • Method for measuring low-pass filtering characteristics of binary fringe defocusing projection system
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  • Method for measuring low-pass filtering characteristics of binary fringe defocusing projection system

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[0033] The specific parameters of the projection system and camera measured in this example are as follows:

[0034] Projection system model: SHARP XR-D255XA, resolution: 1024×768, contrast ratio: 2000:1, aperture range: F=2.4-2.6, actual focal length: f=19-22.7mm, zoom ratio: 1.2×, projection distance: 1.02-7.62m. Camera model: MER-302-56U3C / M, resolution: 2048×1536, pixel size 3.45μm×3.45μm, signal-to-noise ratio 40dB, frame rate 56fps.

[0035] Such as figure 1 As shown, a method for low-pass filtering characteristics of a binary fringe defocus projection system disclosed in this embodiment, the specific implementation steps are as follows:

[0036] Step 1: The camera collects the image of the knife edge, such as figure 2 shown. Select the edge image, read the gray value of each row of the edge image, and average the multiple rows of edge images to obtain the edge transfer function ESF of the camera, and differentiate the ESF to obtain the line transfer function LSF of...

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Abstract

The invention provides a method for measuring the low-pass filtering characteristics of a binary fringe defocusing projection system, and belongs to the technical field of optical three-dimensional measurement. The method comprises the steps that first, a camera is used for collecting an image of a knife edge, and a camera point spread function is obtained; the projection system projects a binaryfringe in a defocusing mode, and a defocused binary fringe image is captured by the camera; then, the camera point spread function is adopted, a Wiener filtering restoration algorithm is used for obtaining a spectrogram of the restored defocused binary fringe image; and finally, a modulation transfer function of the projection system is measured according to the original binary fringe image spectrogram and the restored defocused binary fringe image spectrogram input into the projection system, and the modulation transfer function reflects the low-pass filtering characteristics of the projection system. By adopting the method for measuring the low-pass filtering characteristics of the binary fringe defocusing projection system, the detection steps are simplified without removing a projection objective from the projection system for detection; and meanwhile, the projection system is directly used, no other intermediate auxiliary system is needed, other system errors are not brought in the detection process, and the whole collecting process is convenient, real-time and fast.

Description

technical field [0001] The invention relates to a method for measuring low-pass filter characteristics of a binary fringe defocus projection system, belonging to the technical field of optical three-dimensional measurement. Background technique [0002] Optical three-dimensional measurement technology has the advantages of non-contact measurement, fast speed, high accuracy, and high degree of automation. It is widely used in machine vision, reverse engineering, medical diagnosis and medical cosmetology, anthropometry, manufacturing industry and other fields. [0003] Existing optical three-dimensional measurement research methods include: Moiré profilometry, phase measurement profilometry, Fourier transform profilometry, spatial phase detection, etc. Among these methods, phase measurement profilometry is a universally applicable three-dimensional measurement method because it can simultaneously obtain the spatial information of the full-field fringes and the timing informati...

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Application Information

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IPC IPC(8): G01B11/24G01B11/25
CPCG01B11/2433G01B11/254
Inventor 郝群赵亚如胡摇张韶辉付诗航
Owner BEIJING INSTITUTE OF TECHNOLOGYGY
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