System Transfer Function of Incoherent Light Illumination System

Abstract

Generally, most imaging cases are incoherent light field illumination, and incoherent light illumination system has the advantages of simple installation and no coherent noise, therefore it has received extensive attention. The optical transfer function of illumination system is an effective method to evaluate the imaging quality of such optical system. In order to evaluate the imaging quality of an optical system, the specific form of the system transfer function should be known. However, due to the in-coherent nature of the optical field, both the input function and the impulse response can only be non-negative real functions, it is difficult to deal with lots of bipolar inputs and impulse responses. In this paper, two methods for calculating the system transfer function of incoherent light illumination system under quasi-monochromatic light illumination are given. Method 1: the coherence of incoherent light is defined, and the coherent system transfer function based on the characteristics of the system transfer itself is deduced. Method 2: based on the theory of partially coherent light, started from Kirchoff’s diffraction integral, the quasi-wavefront aberration is introduced, and the spatial coherence of the light field is described by the mutual intensity instead of the mutual coherent function, finally the system transfer function of incoherent illumination is derived. The calculation formula is simple and the transfer function of incoherent light system can be calculated accurately and easily. The work in this paper is helpful to the study of the new phenomena related to incoherent optical imaging.