Repair manual

2-11
THEORY OF OPERATION
P.C. Board increment the stepper motor. As the stepper motor turns, it
rotates the filter wheel assembly until the specified colored filter (red,
green, or blue) is positioned between the CRT and the film.
e. Auto Luminance Photodiode Assembly (Brightness Sensor)
The auto luminance photodiode assembly is a photosensitive diode that is
mounted on the Digital Palette housing. This photosensitive diode, in
conjunction with the auto luminance network and the microprocessor
control circuit on the Logic Controller P.C. Board, monitors the CRT so
that its proper brightness is maintained.
2. Exposure Description
Digital Palette uses the ability of the photographic film to remember light, and
create a final image of a sequence of colored exposures, each one contributing
shape, blending color, or improving resolution. The exposures are made from a
two-level black and white computer-generated video image.
Upon command from the host computer, a black and white video image is
exposed through different colored filters (red, green, or blue) for specified
amounts of time. With this technique, full color images can be created and
recorded on film.
For example, if an image was created with three intensities of red, the
programmer would create and exposure algorithm which would create on film the
image described. The input to the exposure algorithm would be a list of image
items, each to be assigned a different intensity of red on film. Refer to the
Digital palette Software Guide for a detailed description on how to create an
exposure algorithm.
When the image with the three intensities of red is to be recorded by the
Digital Palette, the host computer sends an Expose Color command to it. The
microprocessor control circuit on the Logic Controller P.C. Board decodes the
Expose Color command and positions the red filter on the filter wheel assembly
between the CRT and the film. The CRT turns on to expose the first red image
items through the filter to the film for the specified time. Once the first exposure
is completed, the CRT turns off. This action continues until the film records the
image with the three intensities of red.
This sequential exposure technique can also be used to combine exposures of
each of the primary colors to produce almost any shade or hue desired. Refer to
the Digital Palette Specification Manual for a detailed description of a sequential
exposure.