Fundamental Research On Marginal Apodization Based Microscopy

The simple structure of the broad field microscope makes it easy to realize and is now broadly adopted in the Surface topography measurement, biomedical testing, geological research, etc. However, this method is limited by the diffraction of light and may disappoint the requirement of higher resolution. Compared with it, the confocal microscope improves the contrast of the image by point illumination and point detection, while the two dimensional scanning strategy decreasing the imaging velocity. Therefore, this thesis proposed a novel method to obtain a higher contrast image in a faster speed.First, proposed the marginal apodization microscopy and modeled the imaging process. By placing two optical knife edges in the illumination and detection system, respectively, the imaging beam is then been marginal apodized, which leads to a reduction of the information aliasing and an improvement of the image contrast. After analyzing the effects caused by two knife edges, the system configuration is then simplified. Then the information aliasing of marginal apodization method is compared with that of broad field microscopy to prove that the former one has a higher contrast.Second, the marginal apodization method is combined with one dimensional scanning strategy, which is much faster than the two dimensional one in confocal microscopy. The imaging results of the step-function-reflectivity sample in different scanning moment are calculated and compared to clarify the scanning process. Next, by comparing the image function of the tri-line-sample with different detecting position, determined the best position of the detector is in the marginal zone deviated to the dark region. Afterwards, the stability of the system is testified by adding different power of White Gaussian Noise, which showed a contrast about 20% with the power of 10 dB.Finally, an marginal apodization system was realized to image the 228lp/mm on the resolution test chart USAF1951. Based on the comparison among the imaging results of different detecting position, the one deviated to the dark region next to the central line in the marginal zone was confirmed to have the highest image contrast of 38.94%, and this contrast was 1.77 times larger than 22% of the broad field contrast.