A simple experiment in non-coherent image processing

Abstract

On observing a black line against a white background through a single slit parallel to the line, it is found that the line becomes practically invisible. On the contrary, when the slit and the line are orthogonal, the line remains perfectly clear. Starting from this particularly simple principle, a simple and quick directional filtering can be created. The use of a reflex camera allows both observation and photography of the filtered image at the same time.

An undergraduate experiment to illustrate spatial transfer function concepts in Fourier optics

“…Indeed, common experiments on Fourier optics limit laboratory work only to basic ideas relating to the Fourier Transform (FT) such as FT spectrometry, 7 Fraunhofer diffraction patterns measured over long distances 8,9 or descreening or spatial filtering in the Fourier plane. 10 In contrast, we have designed an experiment using only relatively simple and inexpensive equipment that directly yields the MTF and associated autocorrelation function, allowing students to rapidly learn these advanced imaging concepts in parallel with their lecture material. The experiment provides experience in a number of different areas: geometric optics (thin lens equation, magnification); physical optics (polarization, birefringence, phase); optical instrumentation (SLM, CCD camera, an optical bench); and numerical processing (image encoding, Fast Fourier Transform).…”