AR-C150 (serv.man5). ARC150-Basic Manual - Sharp Copying Equipment Service Manual (repair manual). Page 58

The image forming section characteristics change such as the OPC
drum/developing section (developer/toner) characteristics change
(temperature/humidity change, OPC drum/developer/toner deteriora-
tion) are corrected to maintain the initially adjusted (set) color balance
(gamma).

(Operating conditions)
Developing bias voltage: Voltage after the high density (saturation
density) image correction 

Main charger grid voltage: Voltage after the high density (saturation
density) image correction 

Laser power: Voltage after the OPC drum deterioration correction 

Dot matrix: 2 x 2 (256 gradation, 1 dot 64 gradations)

Toner patch forming sequence: Y/M/C/K

The toner patch forming positions on the OPC drum are the same. 

1) Toner patches are formed with the laser ON duty at the initial set

up of half tone image correction.

2) Compare the relationship between the toner patch density at the

initial set up of half tone image correction and the laser ON duty
(initial data) with the toner patch density formed in procedure 1),
and obtain the correction laser ON duty (

∆

LDc1) from the density

difference. This operation is performed at two or more positions. 

3) The relationship between the input (scanning density level) and

the output (print density level) is determined by SIM46-24(21).
Add the correction laser ON duty (

∆

LDc1) to it.

This adjustment is used to set the gamma characteristics of each
color in the print engine section to the specified gamma charac-
teristics.
In other words, the purpose of this adjustment is to provide an even
density level for all colors.
The gamma characteristics are changed by changing the dot density
(laser ON duty) based on the dither process method.
This determines the relationship between the input (scanning density
level) and the output (print density level) (laser ON duty).

There are following two method:

Automatic method (SIM46-24)
Manual method (SIM 46-21)

a. Automatic method (SIM46-24)
1) Print the color patch patterns of different densities based on the

currently set gamma table.

2) Scan the printed color patch patterns with the scanner and com-

pare the gamma characteristics and the specified gamma charac-
teristics.

3) Make the gamma table which is the closest to the specified

gamma characteristics.

4) Print color patch patterns of different densities based on the

gamma table of procedure 3).
Repeat procedures 2) – 4) to make the gamma table which is the
closest to the specified gamma characteristics.
By repeating the above operations several times, the gamma table
virtually the same as the specified gamma table is obtained.

b. Manual method (SIM46-21)
In this method, the print density adjustment value at the specified
density point is inputted to adjust the gamma directly. This method al-
lows to set an optional gamma characteristics. This method provides
more accurate and finer adjustment than the automatic method. 
It is also advisable to perform a fine adjustment by this manual
method after a rough adjustment by the automatic method.   
The above operation is performed for each color. 

The half tone image correction reference data are made according to
the color balance which is initially adjusted (set) by SIM 46-24 and 21.
Then half tone image correction is properly performed according to
the correction reference data.

(Operating condition)

Developing bias voltage: Voltage after the high density (saturation
density) image correction 
Main charger grid voltage: Voltage after the high density (saturation
density) image correction 
Laser power: Voltage after the OPC drum deterioration correction 
Dot matrix: 2 

×

 2 (256 gradation, 1 dot 64 gradations)

Toner patch forming sequence: Y/M/C/K
The toner patch forming positions on the OPC drum are the same. 

Laser ON duty

ID1

ID2

ID3

ID4

ID15

ID6

ID7

ID8

ID9

ID10

ID11

ID12

ID13

ID14

ID16

Toner patch

density

Half tone image correction

Initial data for the half tone image
correction when executing SIM 44-21

Linear approximation of point 15 is
made and the relationship between
the toner patch density and the
laser ON duty is stored.

∆

LDc1 (Correction level)

Data after the half toner
image correction

Output
density

Input density
Laser diode ON duty

Standard 

Set by SIM46-21, 
63-7 (SIM63-8)

Adjusted 

Output
density

Input density

Laser diode ON duty

Standard 

Previous

Adjusted 

AR-C150

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