Gamma (Γ) Correction; Gradation Processing - Ricoh A193 Service Manual

2.4.5 Gamma (γ) Correction
Gamma correction ensures accurate generation of the various shades in the
gray scale from black to white, accounting for the characteristics of the
scanner and printer.
Scanner gamma correction corrects the data output to the IPU to account for
the characteristics of the scanner (e.g., CCD response, scanner optics).
Printer gamma correction corrects the data output from the IPU to the laser
diode to account for the characteristics of the printer (e.g., the characteristics
of the drum, laser diode, and lenses).
The data for the scanner gamma correction is fixed and stored in the
memory. The printer gamma correction can be adjusted using the service
program mode, SP 2-916.

2.4.6 Gradation Processing

These are four types of gradation processing:
•
Grayscale processing: This has 64 output levels for each pixel, and is
used only in one-to-one copy mode.
•
Binary picture processing: This has only two output levels (black and
white), and is used in memory copying (e.g., multiple copy, rotate sort,
and editing image) and facsimile transmission.
•
Error diffusion: In Text/Photo mode, this is used with either grayscale
processing or binary processing.
•
Dithering: In Photo mode, this is used with either grayscale processing or
binary processing.
These four processes are used as follows.
1) Grayscale processing mode
Text mode:
Text/Photo mode:
Photo mode:
2) Binary picture processing mode
Text mode:
Text/Photo mode:
Photo mode:
Copying using the memory (e.g., multiple copying) and fax mode always use
binary picture processing. (Users requiring grayscale mode output for
multiple copies will have to make a succession of one-to-one copies.)
For one-to-one copying, the processing mode used depends on the setting of
the service program mode, SP 4-403. The factory setting is for grayscale
processing.
SM
Grayscale processing
Grayscale processing + error diffusion
Grayscale processing + dithering
Binary picture processing
Binary picture processing + error diffusion
Binary picture processing + dithering
2-13
IMAGE PROCESSING
(A193)