Binary intensity modulation

Figure 31. Binary intensity versus binary phase modulation.

Due to the binary phase modulation, the distribution of the background power is not uniform and there tend to be small peaks of intensity which may occur at fiber positions. This becomes less of a problem with large numbers of CGH pixels and careful CGH design. 

It should be noted that the MTF expresses the modulation in the image plane of a sinusoidal object and is useful only for incoherent illumination. Under practical conditions for large features (> 3.0 m), the sinusoidal object (mask) is not a good choice when what is really relevant is a binary object. However, as the mask features approach 1.0 pm, the light intensity through the mask becomes sinusoidal and the mathematical formulation for MTF becomes relevant. 

From this analysis it is possible to see why FLC SLMs form a vital part in optical systems. The liquid crystal modulation allows the display of information into coherent optical systems as both intensity and phase images. The nature of the FLC molecular interaction makes it fast and this ideally suits nondisplay applications. Even the restriction of binary modulation does not limit the usefulnes of FLC SLMs, although fast grey scale and multilevel phase modulation would be desirable. In fact, for some applications, binary modulation is a bonus and enhances performance. 

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