measuring the density of the film after developing. A Kodak step

wedge with densities varying in 21 discrete steps from OD 0.05 to OD

3.05 was placed before the test film. The step wedge and film were

then exposed to a known irradiance of laser light for a known duration

of time. The irradiance of the laser was attenuated by each step of

the wedge to give a wide range of exposures to the film. The exposure

for each section of the film is computed based on the laser

irradiance, step density, and exposure time. The film is then

processed in the darkroom using the standardized technique mentioned

previously. This processing plays a major role in the response of the

film and thus must be carefully controlled. The developed film is

placed on a densitometer to measure the resultant density of each

exposed portion. The set of exposure and density points are

incorporated into a polynomial fit routine to produce the

coefficients.

 The output of the polynomial fit routine is shown in Figure 6.2.

 All of the important parameters are recorded in order to reproduce the

 same result in future exposures. The laser irradiance and exposure

 time are recorded to verify that their combination would not suggest

 reciprocity failure which occurs when exposure times are very short or

 very long. It is advised that the exposure time for determining the

 training set be near that to be used in experiments. This may require

 that the experiment be run several times to determine what laser

 irradiance is required. Unfortunately, it may dictate that more laser

 power is needed than is available. In Figure 6.2, it is seen that the

 exposure time was 120 seconds. This is longer than a normal

 holographic exposure but no additional laser power was available to