Vibration detecting device based on multi-wavelength non-lens Fourier transform digital holography

Abstract

The invention discloses a vibration detecting device based on real-time multi-wavelength non-lean Fourier transform digital holography. According to the vibration detecting device disclosed by the invention, an amplitude range which can be detected is determined by effective longitudinal depth of digital holography, and the effective longitudinal depth of a system is determined by the wavelength for forming an interference field; a multi-wavelength digital holography interferometry method is adopted, a composite wavelength which is more than 10 mu m to more than 100 mu m can be formed by selecting different optical wavelengths, a longitudinal detection range is amplified, and real-time detection on the vibration amplitude within the longitudinal detection range can be realized; meanwhile, a non-lens Fourier transform digital holography technology is adopted, first imaging is carried out on reference light and object light, imaging positions relative to a CMOS (Complementary Metal Oxide Semiconductor) are located on the same surface, a numerical representation process requires no complicated diffraction transmission, corresponding information can be obtained through one time of FFT (Fast Fourier Transform), resolving is simple, and real-time detection and real-time resolving can be realized; due to introduction of a short-coherence light source, the generation of speckles is inhibited to a certain degree, and the imaging quality and the detection accuracy are increased.

Description

technical field [0001] The invention relates to a multi-wavelength vibration detection system, which is actually a large-depth vibration detection device based on real-time short-coherent multi-wavelength lensless Fourier transform digital holography. Background technique [0002] Digital holography is an imaging technology that combines optical holography with digital image acquisition and numerical processing. With the development of digital technology in the past two decades, its application research fields have become more and more extensive. The development of high-speed image sensor and computer technology and the application in digital holography technology have enabled the rapid development of vibration detection based on digital holography technology. Holographic technology can record the complete object information in the form of interference intensity field. Digital holographic technology obtains the object amplitude and phase information through numerical diffrac...

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Problems solved by technology

[0004] On the other hand, the current vibration detection technology based on digital holographic imaging still has the following disadvantages: ① The image acquisition and transmission rate of the photodetector device are the key factors affecting the method, the vibration frequency range is large, and the low camera rate often cannot It meets the detection of high-frequency vibration targets, so this method is usually used for the detection of vibration modes; ②This is a kind of surface vibration detection method, with many sampling points, which makes the subsequent calculation of diffraction and image processing more time-consuming. Vibration with a higher frequency cannot be detected in real time; ③Digital holography can only directly obtain the detection of the axial vibration amplitude not greater than the wavelength of light, and when the amplitude is large, it will cause a phase jump, which requires further unwrapping and increased calculation The amount is not conducive to real-time detection, and makes the detection results depend on the unwrapping algorithm to reduce the reliability of the detection results; ④ speckle is the inherent noise of coherent imaging, which has a great impact on small-scale measurement and detailed imaging

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