Theoretical And Experimental Research Of Sampling Volume In In-focus And Out-of-focus IPI Systems

Optical imaging system is an important optical information transmission and processing systems,which has important applications in many fields.A conventional imaging system satisfies the condition that the object plane,lens plane,and image plane are parallel to each other.However,in some imaging systems the object plane is not parallel to the lens plane and image plane;thus,the research of tilted imaging system is of great significance.The tilted imaging system is widely used in the measurement of particle field,and Interferometric particle imaging(IPI)system is an important application.The sampling volume of an IPI system is the basis to study the particle number concentration.The sampling volume of an in-focus IPI system is correlated to the depth of field,while the sampling volume of an out-of-focus IPI system has nothing to do with the depth of field.This paper studies the sampling volume of in-focus and out-of-focus IPI systems.The formula for the sampling volume has been derived,and the measurement method has been proposed.The experimental setup of in-focus and out-of-focus IPI systems have been established,the standard grid calibration plate and the standard spherical particles are used respectively to calculate the sampling volume of the in-focus and out-of-focus IPI systems.This work is of great significance to determine the sampling volume in tilted imaging systems.Main work of this paper:1.Based on geometrical optics,the basic theory of the IPI technique has been analyzed,and several key problems to develop IPI experiment system have been discussed.The choice of the best scattering angle in an IPI system has been studied,the influence of the sampling pool with different ways to put has been discussed,the calibration of magnification in an IPI system has been proposed,and the calculation of parameters in an out-of-focus IPI system has been studied.2.The sampling volume in in-focus IPI systems which are only the object plane is inclined to optical axis(Type-I)or both the object plane and image plane are inclined to the optical axis(Type-II)have been studied,the formula for the sampling volume has been derived,and the effects of the tilted angle,central magnification,focal length,and F-number on the sampling volume have been analyzed.Comparing to the two imaging methods,the sampling volume of the Type-II system is larger than that of the Type-I system.3.The experimental setup of two types of in-focus IPI systems has been established,grid calibration plate images have been acquired,the average line width of objective horizontal has been obtained by image processing,the clear imaging range has been determined,and then the sampling volume of in-focus IPI system has been calculated.4.A method to determine the sampling volume in the out-of-focus IPI systems has been proposed.The sampling region is determined by the range of the interferometric fringe circle size at each position of the CCD target surface,that is12pixpixApixA(37)?(37)?(37).The relationship between the interferometric fringe circle size and its position on the CCD target surface or back defocus distance has been analyzed.The formula of the sampling volume in the out-of-focus IPI system has been derived.5.The experimental setup of the out-of-focus IPI system has been established.The interferometric fringe circles of the standard spherical particles have been acquired,the range of interferometric fringe circle size within the whole view has been calibrated,and then the sampling volume of out-of-focus IPI system has been obtained.