Abbe Imaging and Spatial Filtering Experiment 

The Abbe imaging principle believes that the imaging process of a lens can be divided into two steps: the first step is to form a spatial spectrum on the rear focal plane (spectrum plane) of the lens by diffracted light from the object, which is the "frequency division" effect caused by diffraction ; The second step is to coherently superimpose the beams of different spatial frequencies on the image plane to form an image of the object, which is the "synthesis" effect caused by interference. The two steps of the imaging process are essentially two Fourier transforms. If these two Fourier transforms are completely ideal, that is, there is no loss of information, then the image and the object should be completely similar. If various spatial filters are set on the spectrum surface to block certain spatial frequency components of the spectrum, the image will change. Spatial filtering is to place various spatial filters on the spectrum surface of the optical system, remove (or choose to pass) certain spatial frequencies or change their amplitude and phase, so that the two-dimensional object image can be improved as required. This is also the essence of coherent optical processing.

Experiments
1. Strengthen the understanding of the concepts of spatial frequency, spatial frequency spectrum and spatial filtering in Fourier optics
2. Familiar with the optical path of spatial filtering and the methods to realize high-pass, low-pass and directional filtering

Specifications