Complex Spatial Filtering with Binary Masks

Abstract

Usually a hologram is produced by means of an interference experiment. Here, however, we let a computer- guided plotter draw the hologram. The plot, which has to be minified and recorded on film, contains no grey, only binary transmittance values. Our binary holograms yield reconstructed images of a quality equal to that of images obtained from usual holograms of comparable dimensions. When a Fourier hologram is inserted into the Fraunhofer plane of a coherent image forming system, it acts as a special type of a spatial filter, a so-called optical matched filter. Our binary matched filter is suitable for optical character recognition, the same as the usual optical matched filter introduced by Vander Lugt.

Holographic 3-D Displays - Electro-holography within the Grasp of Commercialization

“…Decomposition methods: Since the very beginning of computational holography decomposition methods for complex-valued wavefields have been developed 1 . Famous examples of holograms utilizing the detour-phase concept are those from Brown and Lohmann (Brown & Lohmann, 1966), Lee (Lee, 1970), Burckhardt (Burckhardt, 1970) and the double-phase holograms from Hsueh and Sawchuck (Hsueh & Sawchuk, 1978). All methods have in common that the hologram is divided into discrete resolution cells having apertures or stops of different size and position or having a certain number of sub-cells.…”

Computer-generated holograms

“…7), and we will obtain a picture of the cat centred on the direction of the published in 1967 [2], entitled "Binary Fraunhofer Holograms, Generated by Computer". This secret is the so-called detour phase method that Lohmann had described a year earlier [3]. In his article he wrote: "There are three possibilities to influence the phase of a light wave: retardation while traveling through a dielectric, phase jump at reflection, and detour phase.…”

Iterative Fourier Transform Algorithm Based on the Segmentation of Target Image for a High-Speed Binary Spatial Light Modulator

“…Early research on binary holograms was performed by Brown and Lohmann [1][2][3]. In these studies, there was some freedom to design the structure of every pixel independently where each pixel presents both amplitude and phase modulations of the optical wave.…”