Optimization of liquid crystal displays behavior in optical image processing and in diffractive optics

J. CAMPOS; A. MÁRQUEZ; J. NICOLAS; I. MORENO; C. IEMMI; J. ESCALERA; J. DAVIS; M. YZUEL

Optoelectronic Information Processing: Optics for Information Systems.

SPIE

Lugar: bellingahm; Año: 2001; p. 335 - 364

In this paper we will revise the application of twisted nematic liquid crystal displays (TN-LCD) as spatial light modulators (SLM) for image processing and diffractive optics. In general two kind of responses are desired for the mentioned applications: amplitude-only and phase-only modulation. In general the users of commercially available LCDs do not know the optical properties of the used material. Thus, a reverse-engineering approach is needed to optimize the LCD response. First, we show a simplified model, that we recently proposed, for the orientation of the LC molecules. The model allows the determination of the physical parameters of the LCD by means of simple intensity measurements. Second, we demonstrate the capability of the model to provide very accurate predictions of the optical transmission. Therefore, we can perform computer searches for the optimum orientation of the added polarizing elements to obtain the required optical transmission. We demonstrate the need to insert wave plates in front and behind the LCD to obtain either amplitude-only or phase-only regimes with the LCD. Finally, we show the application of the optimized LCD to display images and filters in optical image processing, as well as we show the design of diffractive optical elements and apodizers.