| Acousto-optic tunable filter(AOTF)is a band-pass filter that can be directly controlled by a computer.It can select wavelengths very quickly and randomly.It has high diffraction efficiency,fast tuning response speed,small size,and relatively large incident aperture,support for various scanning modes and fixed frequency operation.As one of the core components of hyperspectral imaging technology,AOTF is widely used in various fields.Nowadays,the imaging technology combining optics and biomedicine is developing rapidly,and the application of hyperspectral imaging technology in the biomedical field is also attracting more and more attention.With the rapid development of hyperspectral imaging technology and biomedicine,the trend of applying hyperspectral imaging technology to non-destructive medical diagnosis is becoming more and more obvious.From the perspective of hyperspectral imaging methods,there are reflection,transmission and fluorescence,etc.At present,the more mature hyperspectral imaging technology applied in the biomedical field is mainly the transmission and fluorescence imaging system combining acousto-optic tunable filter with microscope.Based on the acousto-optic tunable filter,this paper will carry out relevant experimental research together with fiber endoscopes,and finally observe biological tissues and explore the field of biomedical detection.In this paper,an imaging system that combines endoscopic techniques with hyperspectral techniques is designed to obtain hyperspectral images and spectral information of biological tissues in the visible light range.The main contents of this article are:Firstly,the development status of hyperspectral imaging technology and fiber endoscopy based on acousto-optic tunable filters is introduced,and then the main content and significance of this study are clarified according to the research background and existing conditions in the laboratory.Secondly,starting from acousto-optic interaction,the relevant theoretical basis is discussed,and the coupled wave equation is derived;then the relevant principles of anomalous Bragg diffraction are discussed,and the vector relationship of anomalous Bragg diffraction is clarified;finally,the physical structure and working principle of the AOTF based on tellurium dioxide are studied,which shows that the anomalous Bragg diffraction can only occur when the incident light enters the AOTF if the momentum matching principle is satisfied.At the same time,the theoretical formula of the one-to-one correspondence between ultrasonic frequency and diffracted light wavelength is deduced.Third,an endoscopic hyperspectral imaging system combining fiber endoscope and acousto-optic tunable filter is designed and built,which can simultaneously obtain endoscopic hyperspectral images and spectral information under different diffracted light wavelengths,which has the advantage of integrating image and spectrum.The system is used to conduct experimental study on the resolution test target,and evaluate the system performance from two aspects of spatial resolution and spectral resolution.In order to further determine the feasibility of the system for biological tissue detection,experimental studies were carried out on red,green and blue paper and leaves with pests and diseases.Finally,depending on the applicable environment,we have optimized and improved the endoscopic hyperspectral imaging system based on the acousto-optic tunable filter,and designed a portable reflective endoscopic hyperspectral imaging device.The device can be freely switched between conventional endoscopic mode and endoscopic hyperspectral imaging mode,so the system can not only obtain white light images under conventional endoscopes,but also hyperspectral images and spectral data.Using this system to conduct experimental research on pig testis and pig ovary,more image information and spectral information are obtained.The experimental results show that the hyperspectral image improves the image contrast,and can obtain more information of the measured object,which reflects the superiority of the system.In order to improve the clarity of the image,image processing research was also carried out on the obtained image,and the image noise caused by the optical fiber was denoised.Compared with the conventional endoscope system,the portable endoscopic hyperspectral imaging system can obtain three different kinds of information of the measured object,which provides more useful information for biomedical detection,helps to improve the accuracy of medical diagnosis,and proves the great potential of hyperspectral technology in medical diagnosis. |
