Optical Methods: Fourier Filtering and Phase Contrast

This lecture covers various optical methods, focusing on Fourier filtering techniques and phase contrast microscopy. It begins with the propagation of light, explaining how light from a point source behaves at infinity and how lenses transform point sources into plane waves. The instructor discusses the Fourier transform's role in optical systems, particularly in vision and photography, where the image is formed through lens systems. The lecture introduces the concept of an optical roughness tester, illustrating how surface roughness can be analyzed using Fourier optics. The instructor explains the 4F setup for Fourier filtering, detailing how to filter high and low spatial frequencies to enhance images. Finally, the lecture addresses phase contrast, a technique used to visualize transparent objects by manipulating phase variations, highlighting its significance in microscopy. The discussion emphasizes the practical applications of these optical methods in analyzing and enhancing image quality.