Experimental application of low-cost liquid crystal TV to white-light optical signal processing.
About: This article is published in Applied Optics.The article was published on 1986-10-01. It has received 42 citations till now. The article focuses on the topics: Image processing & Signal processing.
Citations
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TL;DR: A new, to the knowledge, technique for encoding amplitude information onto a phase-only filter with a single liquid-crystal spatial light modulator, effectively allowing for amplitude modulation of either the first-order or the zero-order diffracted light.
Abstract: We report a new, to our knowledge, technique for encoding amplitude information onto a phase-only filter with a single liquid-crystal spatial light modulator. In our approach we spatially modulate the phase that is encoded onto the filter and, consequently, spatially modify the diffraction efficiency of the filter. Light that is not diffracted into the first order is sent into the zero order, effectively allowing for amplitude modulation of either the first-order or the zero-order diffracted light. This technique has several applications in both optical pattern recognition and image processing, including amplitude modulation and inverse filters. Experimental results are included for the new technique.
452 citations
TL;DR: A new implementation of the real-time joint transform correlator architecture using inexpensive LCTVs will be discussed and preliminary experimental results are presented to verify the usefulness of the technique.
Abstract: Recently, many applications of the liquid crystal television (LCTV) to real-time signal processing have been reported. A basic description of the application of the LCTV to realtime pattern recognition was first reported by Liu et al. Gregory later also showed a successful space-invariant correlation using a LCTV as a spatial light modulator. Both methods were based on the use of a complex matched (VanderLugt) spatial filter. The joint transform architecture is an alternative approach to optical pattern recognition. The joint transform method has proved to be suitable for adaptive programmable correlation because no matched spatial filter is required. The reference pattern may simply be generated by a computer and input to a low space-bandwidth product (SBP), electronically addressed, spatial light modulator. Conversely, it is very difficult to generate a dynamic matched spatial filter in the Fourier plane. A microcomputer-based programmable optical correlator using a magnetooptical device (MOD) and a liquid crystal light valve (LCLV) was proposed recently by Yu and Ludman. In this Letter, a new implementation of the real-time joint transform correlator architecture using inexpensive LCTVs will be discussed. Preliminary experimental results are presented to verify the usefulness of the technique. There are three major objections to using commercially available liquid crystal TVs for optical processing applications: (1) low contrast ratio, (2) phase nonuniformity, and (3) low resolution and low SBP. These problems must be minimized if a LCTV is to be used as a spatial light modulator in a coherent optical system. The contrast uniformity
183 citations
TL;DR: It is shown that superior phase-only operation can be obtained over a given operating range for the LCD compared with other approaches and that the eigenvectors are elliptically polarized.
Abstract: We derive theoretical expressions for the eigenvalues and the eigenvectors for a twisted-nematic liquid-crystal display (LCD) as a function of the twist angle and the birefringence by use of the Jones-matrix formalism. These polarization eigenvectors are of particular interest for phase-only transmission because they propagate unchanged through the display. We find that the eigenvectors are elliptically polarized and that the ellipticity changes as a function of the birefringence of the LCD (which is proportional to the external voltage applied to the display). We can define an average eigenvector over a desired range for the applied voltage. We show, using Jones matrices, how this average eigenvector can be generated using a quarter-wave plate and a linear polarizer having appropriate orientation angles. Using this average eigenvector, we show that superior phase-only operation can be obtained over a given operating range for the LCD compared with other approaches.
152 citations
TL;DR: It is shown that, if the phase nonuniformity of the LCTV is corrected by a liquid gate, then a simple computer-generated hologram can be written and coherently reconstructed.
Abstract: A novel use of liquid-crystal television (LCTV) is described. It is shown that, if the phase nonuniformity of the LCTV is corrected by a liquid gate, then a simple computer-generated hologram can be written and coherently reconstructed.
136 citations
TL;DR: It is found that it is possible to obtain continuous phase modulation from 0 to PI with essentially no change in the state of polarization of the output light and absorption changes of <2.5%.
Abstract: We used a commercially available liquid crystal television display unit as a spatial optical phase-only modulator. To do this, we removed the integral polarizers from the unit and double passed the light under modulation through it. We found that it was possible to obtain continuous phase modulation from 0 to PI with essentially no change in the state of polarization of the output light and absorption changes of <2.5%. We wrote computer-generated phase-only holograms on the LCTV and reconstructed them optically.
124 citations
References
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TL;DR: It is discovered that the extremely inexpensive Radio Shack liquid-crystal television, with proper modifications, has potential for optical-data-processing applications.
Abstract: The potential of the extremely inexpensive Radio Shack liquid-crystal television (LCTV) as a two-dimensional spatial light modulator has been investigated. The LCTV modulates the transmission of coherent or incoherent light and can either be electronically addressed through a microcomputer or optically addressed with a TV camera. We have measured the transmission characteristics of the device, examined its diffraction pattern, and tested its use as an input device for an optical correlator. We have discovered that, with proper modifications, it has potential for optical-data-processing applications.
183 citations
TL;DR: La television a cristal liquide est utilisee comme modulateur spatial dans un correlateur optique dans l'ouverture de l'entertainment spatial.
Abstract: La television a cristal liquide est utilisee comme modulateur spatial dans un correlateur optique
101 citations
46 citations
42 citations
TL;DR: Qualite de l'image lors de mesures de deplacements dans le plan ou utilisation de lentilles holographiques lors oficiales de lentille holographique.
Abstract: Qualite de l'image lors de mesures de deplacements dans le plan. Utilisation de lentilles holographiques
27 citations