This paper describes the measurement principle and structure,and optimizes the key technique in the system. By the design of a gradient index lens,pinhole,light source and detector,high precision and small optical focus detection can be realized.
It is pointed that,in order to obtain high axial resolution,parameter A related to fiber optical spot should be less than 3,the high magnification gradient index lens should be selected,the numerical aperture a gradient index lens should less than that of a fiber,and precision assembly between a gradient index lens and the fiber should be abtained.
In order to use the gradient index lens in the micro system, math model on dispersion of Grin lens was constituted. According to SLW -3.0 lens form NSG Company by ZEMMAX software, equivalent dispersion coefficient in two kinds of cases and the way of dispersion for lens were gained.