Ricoh IS450S Service Manual page 33

22 December 1998
Image processing path
The following image processing is for the scanner (simplex model), not including
the optional IPU. The image processing for each of these units is explained in
separate sections. However, when the optional IPU is installed, the IPU IC on the
SCU only does the shading.
1. Without Optional IPU
S B U
S h a d i n g Magnification/
correction Mirror Process
2. With Optional IPU
Shading Correction
The machine scans the white plate opposite the ADF exposure glass to make a
white waveform. Shading correction prevents uneven images caused by
fluctuations in scanned data due to changes in light intensity and CCD sensitivity.
Magnification
Reduction and enlargement in the sub scan direction are done by changing the
scanner motor speed or paper transport motor speed in the ADF. However,
reduction and enlargement in the main scan direction are done by the IPU.
Mirror Processing
A mirror image of the original must be made for output.
Filtering
There are two software filters: the MTF filter and the smoothing filter. The MTF filter
emphasizes sharpness, and is used with text-only documents or documents that
contain text and photo areas. The smoothing filter is used for photo-image
documents.
S C U
I P U
γ correction
Filtering
S C U
S B U I P U
S h a d i n g
correction
2-19
IMAGE PROCESSING
M e m o r y
Controller
Dither/
Binary process
Error Diffusion
Optional
I P U
White/black
conversion
G411D500.WMF