accuracy.. The resultant transmittance on the film will have one of

256 quantized levels determined by an integer value provided by the

computer. Quantization occurs when all values in a specified range

are assigned to a quantized value representative of that range. If

the quantization steps become large, the quantized level may be a poor

estimate of the actual values. The estimate is equivalent to the

actual pattern with an additive noise called quantization noise.

Quantization noise occurs in computer-generated holograms because the

computer-graphic devices have limited gray levels and a limited number

of addressable locations in their outputs. Quantizing the holographic

pattern into 256 gray scale levels introduces quantizing noise which

may be considerable when the dynamic range of the pattern is large.

To minimize the quantizing error, the coding scheme must produce a

result with a dynamic range compatible with the writing system.

 Some writing systems are capable of only two quantized levels.

These binary devices are either on or off. Most metal etchers, ink

plotters, dot matrix printers, and lithographic printers are binary.

The mark they create is either completely on or completely off. To

represent the reference pattern on binary media accurately requires

specialized coding schemes.

 Binary Holograms

 Binary holograms are attractive because binary computer-graphics

output devices are widely available and because problems with

nonlinearities in the display and recording medium are circumvented.

When photographic emulsions are involved, granularity noise is

reduced. Using the normal definition of dynamic range, binary

holograms have a dynamic range of 1. The transmittance at each point