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Method for measuring higher frequency vibration by utilizing low-speed camera based on fringe projection method

A fringe projection, high-frequency vibration technology, applied in measuring devices, measuring ultrasonic/sonic/infrasonic waves, instruments, etc., can solve the problems of increasing measurement cost, data storage cost, camera cost, etc. Good reliability and portability

Inactive Publication Date: 2018-03-06
TIANJIN UNIV
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AI Technical Summary

Problems solved by technology

The sampling rate of ordinary industrial cameras is 40 frames per second, and the highest frequency signal that can be measured theoretically is 20Hz, which has great limitations
The cost of purchasing a high-speed camera is relatively high, and with the increase of camera sampling frequency, the cost of data storage is also greatly increased, which greatly increases the cost of measurement

Method used

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  • Method for measuring higher frequency vibration by utilizing low-speed camera based on fringe projection method
  • Method for measuring higher frequency vibration by utilizing low-speed camera based on fringe projection method
  • Method for measuring higher frequency vibration by utilizing low-speed camera based on fringe projection method

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Embodiment Construction

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific examples.

[0022] see figure 1 , the schematic diagram of the principle of the present invention based on the fringe projection method: the stable vibrating object to be measured is placed on the reference plane, and its surface is in a different position at each different moment. The black and white stripe images are generated through the program, connected to the projector and projected on the surface of the object, and the CCD camera is responsible for collecting and storing the images of the object at different times.

[0023] The fringe generation device generates the black and white fringes shown in the dotted line box through the program, connects to the projector, and adjusts the focus knob of the projector so that the generated image is clearly projected on the vibrating object to be tested. Controlling a vibrating object produces a low-frequency v...

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Abstract

The invention relates to a method for measuring higher frequency vibration by utilizing a low-speed camera based on a fringe projection method. The method comprises the following steps: projecting generated black and white stripe images onto the surface of an object through a projector; setting camera sampling frequency and exposure time; adjusting camera exposure degree to enable black and whiteportions of the stripe images to be equal in width; measuring system parameters; selecting the striped portions in all of the obtained stripe images, and recovering height change of vibration object surface at each sampling moment through Fourier transform profilometry; drawing a height change curve, that is, a vibration trajectory, of the selected sampling points; and comparing height differencebetween the maximum value and the minimum value of the trajectory curve to obtain vibration amplitude data directly, and vibration frequency data being obtained by multiplying the number of sampled images required in the whole period by the exposure time.

Description

technical field [0001] The invention relates to a method for realizing the measurement of higher frequency vibration by a low-frequency camera, which belongs to the field of optical vibration measurement. Background technique [0002] According to the Nyquist sampling theorem, if the information in the original signal is to be completely restored, the sampling frequency must be greater than twice the highest frequency in the original signal. In general practical applications, the sampling frequency is guaranteed to be 2.56 to 4 times the highest frequency of the signal. The sampling rate of ordinary industrial cameras is 40 frames per second, and the highest frequency signal that can be measured theoretically is 20Hz, which has great limitations. The cost of purchasing a high-speed camera is relatively high, and with the increase of camera sampling frequency, the cost of data storage is also greatly increased, which greatly increases the cost of measurement. Contents of t...

Claims

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Application Information

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IPC IPC(8): G01H9/00
CPCG01H9/00
Inventor 吕辰刚刘宇翔高嘉乐苌雨晴张绪赓刘宁
Owner TIANJIN UNIV
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