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4.5 Image Bus
The image data read by the CCD goes through analog-to-digital
conversion before being output.
The analog image signals output from the CCD are
converted to digital image signals.
The data read by the CCD is proportionate to the
intensity of the light that has passed through the
film. A conversion formula is used to convert the
data read by the CCD into the image density data
which has a characteristic linear to the film density.
The CCD (Charge Coupled Device) reads the data
on the Film.
Shading Correction
If the CCD were to read the reflected light from an
original having a uniform density, the outputs along
the length of that CCD may vary individually due to
uneven light distribution along the length of the
Lamp and varying sensitivities of different CCD
chips. These variations are corrected through
shading correction.
CCD output
Image
After Shading Correction
Black
White
Black
White
White
Black
CCD
Line memory
Density conversion
The pixel signals from the five CCD chips are
output serially in the order of CCD1, CCD2, CCD3,
CCD4, and CCD5.
Shading correction
A/D conversion
PWB-A
PWB-BB
A
The elemental output signals are evened out in
compensation for uneven illuminance of the
Projection Lamp and sensitivity variations among
CCD cells and Projection Lens.