Optical System Design And Image Acquisition And Processing Scheme Of Fluorescence Electronic Endoscope

Endoscopy is one of the essential medical equipment in clinical examination at present.With the miniaturization of camera and the development of endoscope insertion,minimally invasive surgery emerged as the times require.Doctors’ judgment of the location and size of the resected site stems from the results of various medical imaging diagnoses before surgery.Endoscopic surgery only plays the role of expanding the field of vision.However,it can not distinguish between healthy areas and pathological tissues,which will reduce the accuracy of surgery.To improve the accuracy of excision,an optical system that can display fluorescent labeling map under normal illumination light source is proposed.Firstly,according to the spectral band range of fluorescent agent,the appropriate CMOS is selected,and the corresponding optical imaging structure system is designed by ZEMAX software.The working wavelength,focal length,FOV and F number of the designed optical system are 0.45~0.90μm,1.11 mm,90°and 5,respectively.The result shows that its total length is 5.5mm and maximum cross sectional diameter is 1.8mm,and The MTF value of the lens is approximately 0.2 at the spatial frequency of 160 lp/mm,which has advantages including large field of view,large depth of field and small volume.Secondly,the frame signal of the camera is used as the control signal of illumination,and the bright and dark field images are captured by time-division frames to obtain the bright and dark field images appearing at intervals.Then the adjacent images are fused and labeled,which achieves the goal of simultaneous display of bright and dark images,and solves the problem of video fusion.Finally,the two kinds of images are pre-processed by piecewise linear transformation,colorization and luminance enhancement algorithms,and then the two kinds of images are labeled by pixel superposition and wavelet transform.The average gradient and information entropy are used to evaluate the output images of the two algorithms.It is shown that the wavelet transform retains more image information when the coefficient is less than 1.