Optical Lens Designed For Measuring Laser Speckle Of Projector

Measuring laser projection speckle consists mainly of two modules:Optical;ens for measuring and image processing,the speckle pattern on the screen is collected by optical lens,and then the contrast of images are analyzed using the computer image processing module.At present,laser projector has not yet reached the popularization stage,but the laser has a high saturation image,high conversion efficiency,small size and other advantages,attracting many scholars and companies to research.One of obstructions is the presence of laser speckles that seriously affect the quality ofprojector images.For the study of laser speckle measurement,there is no uniform testing and evaluation criteria,projection lens,CCD chip,image processing and other factors will affect the test results,this paper is based on this issue to research.Firstly,the difference between speckle patterns according to the human eye resolution size area for segmentation and processing by pixel was simulated by images processing software.The simulation results show that the speckle pattern contrast of the human eye resolution size is lower than that of the pixel.Speckle contrast calculation according to the size of the human eye to distinguish can more truly reflect the feelings of the human eye.Secondly,the experimental system for measuring laser speckle was built up using the standard CCD lens.After imaging experiments and images processing,the relationship between the main parameters of CCD,the optical lens parameters and laser speckle contrast was present.According to the requirements of measuring parameters,a CCD lens for laser projector speckle measurement was designed using ZEMAX software.Its F number is 2.1,the focal length f' is 37.23mm,For all fields of view,the results of the lens optimization show that the modulation transfer(MTF)is greater than 0.3 at a spatial frequency of 115 lp/mm,The maximum distortion is controlled below 0.05%,the Root Mean Square radius(RMS)is within 4?m,the design results to meet the imaging requirements,and the result of the tolerance analysis shows that the lens group can meet the processing and assemble requirements.