Computer constructed optical-rose diagrams

Abstract

Rose diagrams, a circular plot of relative frequencies, are a convenient method of visualizing directional data. One method of obtaining optical-rose diagrams is by sampling the intensity distribution across the Fourier transform. This transform is produced optically using directional data in pictorial form. High-contrast black-and-white reduced transparencies form the input to the optical system containing a monochromatic laser source and a series of lenses to focus the diffraction pattern on the transform plane. Light intensity, recorded digitally over all directions on the transform plane by a set of photodiodes, is normalized and circularly plotted by computer to produce optical-rose diagrams. By selective filtering, certain directions can be eliminated to enhance the effect of the residual major or minor directional features. Directional filtering is achieved by obstructing the light in the transform plane by a wedge and using another lens. These filtered transforms can be reconstructed to form the image with the desired directions. Optical-rose construction is easy, economical, and fast, in addition to having the flexibility of selective directional filtering and reconstructing the filtered image.