Independent Dot Erase; Background Erase; Gradation Processing; Overview - Ricoh Russian-C2a Service Manual

IMAGE PROCESSING
Each characteristic filter consists of a combination of the following features: MTF,
smoothing, error diffusion, dithering, ID gamma correction. For each of these
features, the machine chooses from two types when making up a characteristic
filter.

Independent Dot Erase

Independent dot erase removes unwanted dots from the image.
Independent dot erase is enabled only for Generation Copy mode (according to the
default settings). However, for the "Custom Setting" original modes, independent
dot detection can be enabled and adjusted with SP4-904-2~4. With a larger SP
setting, more dots are detected as independent dots and erased, even if the dot
density is high. However, dots in mesh-like images may be mistakenly detected as
independent dots.

Background Erase

By default, this process is disabled in all original modes. However, it can be
enabled with SP mode.
Usually, dirty background is erased using the Auto Image Density (ADS) function.
However, sometimes, dirty background areas will still appear. These can be erased
with this function.
The threshold level for erasing can be changed with SP4-904-6~10.
ID Gamma ( γ γ γ γ ) Correction
The machine automatically selects the most appropriate ID gamma correction
based on the selected original type.
Also, for certain combinations of reproduction ratio and original type, characteristic
detection is used. In this case, the machine can use one of two gamma correction
tables. The one that is used is decided separately for each pixel, and depends on
the results of characteristic detection.

Gradation Processing

Overview

There are four types of gradation processing:
• Grayscale processing: This has 4 output levels for each pixel.
• Binary picture processing: This has only two output levels (black and white).
• Error diffusion: There are two error diffusion processing types (normal and
characteristic detection)
• Dithering: There are two dithering processing types (normal and characteristic
detection).
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10 August, 2001