The use of liquid-crystal panels from a commercially available Sanyo video projector as spatial light modulators in a standard joint transform correlator system is investigated. It is found that the flatness distortion of the panels disturbs the output correlation signal in general. Since the reported solutions for the flatness corrections are either expensive (liquid gates) or suffer from low light efficiency (holographic techniques), we have investigated a possibility to minimize the influence of these distortions on the correlation output without flatness correction. First, we quantify optical flatness across the transparent panel area, and then we measure the effects of flatness distortion by changing the display location of the input objects and the resulting joint power spectrum. It is found that the correlation peak is 1 order of magnitude more sensitive to phase distortions of the input scene than to the same distortions of the joint power spectrum. Choosing the flattest location on the panel allows the utilization of the panels to be demonstrated through recognition of cuneiform inscription signs.

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The importance of spatial light modulators (SLMs) in optical systems is increasing. This paper presents our work on an SLM system based on Sony LCD. We show the optimization of the LCD modulation behavior concerning the application as dynamical diffractive element, and the implementation of images and filter functions in optical correlators and pattem projection systems.Measurements of the coupled amplitude and phase modulation and the planarity of the display at different wavelengths lead to correction functions and several optimized operation modes, e.g. gray scale or binary amplitude modulation. The optimization in the amplitude mode leads either to high contrast images of reduced gray levels or to a mostly linearized full gray scale mode. A similar way leads to optimized modes for the phase modulation and to a realization Ofa total phase shift of 2it. The increase of the processing performance of phase-only filters in optical correlators is presented. Furthermore, diffraction efficiency (DE) measurements of Fourier holograms addressed to the SLM prove the optimization process, compared to the non-optimized and the theoretical DE-values. So, estimations can be made concerning the application ofthe SLM as dynamical diffractive element.

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Liquid crystal displays, operating in a linearized phase mode, can achieve a performance to be applicable as diffractive elements. We built up a Fourier-system with a Sony-LCD based spatial light modulator in order to realize dynamic diffraction patterns. The quality measures of our DOE in the output plane of the system are promising for a wide range of applications. The performance oftechnical beam splitters, realized as binary or 8-256 level diffractive elements will be discussed in the paper. Here we will focus on parameters as diffraction efficiency, signal to noise ratio and also speckle effects. Since the display is addressed directly from the graphics card series of diffraction patterns and animations can be realized. Furthermore, beam shaping elements, two-dimensional holograms and the reconstruction of digital holograms will be shown. The latter opens new possibilities for non-destructive testing devices especially in the field of holographic interferometry. The limiting parameters of the performance are mostly due to physical boundary conditions, such as pixel number and size, response time, transmission etc. . We can assume that the fast growing micro-structuring technology will serve us soon with displays of higher resolutions and efficiency. A discussion concerning requirements for medial or micro-fabrication applications, particularly due to the limited efficiency and the intensity-dependent modulation, will finish the paper.

Holographic interferometry with three illumination directions can be applied to detennine all components ofa displacement vector wihtout previous knowledge of the main deformation direction. Combined with a microscopic arrangement this method is utilized for the investigation of the operating parameters of sensor micro-components. The interferometer is adapted to the microscopic demands by conjugate reconstruction. Matching holographic and microscopic requirements is the fimdamental assumption for correct operation of the holographic microscope. By the application of all advantages of conjugate reconstruction the holographic microscope has been optimized in optical and numerical parameters for the evaluation of all components of the deformation vector. Phase shifting and carrier fringe techniques have been applied for interferogram evaluation according to the object shape and deformation behavior. When absolute values ofthe deformation were already determined, electrooptic holography can be used for routine measurements because of its time savings. The method was used for the calibration of cantilevers for micromechanical sensors, the determination of the deformatious of a circular micromembrane, and a solder joint in a microelectronic printed circuit board. The influence of different object orientation on the measurement resuls was investigated additionally.