Phase retrieval in computer generation of schlieren images

Paulo Torrao Fiadeiro; David C. Emmony

doi:10.1117/12.221537

29 September 1995 Phase retrieval in computer generation of schlieren images

Paulo Torrao Fiadeiro, David C. Emmony

Proceedings Volume 2546, Optical Techniques in Fluid, Thermal, and Combustion Flow; (1995) https://doi.org/10.1117/12.221537
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

The schlieren technique involves the manipulation of knife edges to limit the field of view in the image formation process. Practical implementation of this technique is not easy due to difficulties in positioning the knife edge in the optical system. A related problem concerns the reproducibility of an event to generate a series of schlieren images for different knife edge positions. A particularly successful method to overcome this problem is the use of the computer to generate such images from single pictures of the event. Computer generation of schlieren images involves the inverse Fourier transformation of the modified complex-valued diffraction pattern (magnitude and phase) of the event. Recording media in general respond only to light intensity and no difficulty is encountered in recording the intensity, and therefore the magnitude. The phase is either unobservable directly or cannot be determined anywhere nearly as accurately as the intensity. The Gerchberg and Saxton interative algorithm is used to recover the phase from records of intensity (magnitude) taken from the image and Fourier domains of the optical system. The knowledge of magnitude and phase in the Fourier domain (diffraction pattern) will enable us to modify it through a computer knife edge and generate the corresponding schlieren images.

Citation Download Citation

Paulo Torrao Fiadeiro and David C. Emmony "Phase retrieval in computer generation of schlieren images", Proc. SPIE 2546, Optical Techniques in Fluid, Thermal, and Combustion Flow, (29 September 1995); https://doi.org/10.1117/12.221537

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