Investigation of the properties of a sharp-focusing schlieren system by means of Fourier analysis

The sharp-focusing schlieren system is analysed by means of a Fourier approach. The signal received in the imaging plane is governed by the phase distribution in a particular object plane normal to the optical axis, while the contributions from other planes in the object that are out-of-focus can be considered as noise. A numerical simulation performed for a specific test object shows that the best spatial resolution is obtained with a system of five channels and that further increase of the number of channels does not improve the signal quality.