Effect of Gaussian Source on Differential Confocal Microscopy Pointing Signal

The axial response of conventional confocal microscopy is affected by an extended Gaussian source, so does the differential confocal microscopy which is proposed because of the better signal to noise ratio(SNR) and better resolutions both in axis and lateral. When the specimen is measured with the method based on the differential confocal microscope, Gaussian source influences the output signal , as well as the measuring accuracy and resolution of the differential confocal microscope. In this paper, the principle of the differential confocal microscopy is introduced, and the optical transfer function of that is obtained according to the 3-D coherent image theory with a z-axial symmetric Lorentzian-Gaussian laser source. Considering both the size of the source and of the beam spot of Gaussian beam, their influences on the axial resolution are studied and calculated. The results are also presented and the conclusion of the influences with a relevant source aperture is obtained finally.