Liquid Crystal Logic Elements

More complicated mathematical operations can also be performed using liquid crystal devices. The analogue converter is an example [56] of this. In this, any time-dependent mathematical function can be reconstructed in a liquid crystal element. The diffraction of light by the liquid crystal 

FIGURE 8.10. Layout of an optical filter [59]. 1, Coherent light source 2, 2, 2 , lenses 3, object or transparency 4, spatial filter, specifically, liquid crystal filter 5, control device for the filter and 6, filtered image of the object. 

The combination of a computer and an electronically addressable two-dimensional spatial light modulator is a good device in performing highspeed computations. The modulators could be used for basic logic operations while a computer could be used for programming and memory [57]. The operation speed ranges from 10 ms (pixel for nematics) to 0.5 /iS (pixel in electroclinic effect in smectic A liquid crystals), see Chapter 7. 

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