AR-C150 (serv.man5). ARC150-Basic Manual - Sharp Copying Equipment Service Manual (repair manual). Page 51

The toner image patch density on the transfer belt is precisely de-
tected by correcting changes in sensitivity due to dirt on the image
density sensor and a change in the temperature during the high den-
sity (saturation) image correction and the half tone image correction.
Thus the above correction is made correctly.
There are two sensor; one for color and the other for monochrome. 
The correction is made for each of them. 

(Calibration operation 1 of the image density sensor for color) 
1) Perform calibration of the image density sensor by attaching the

adjustment sheet to the transfer belt with SIM 44-4. 
Read the reflection lights from the adjustment sheet to obtain the
LED drive voltage (Vref) which provides the specified output. 
Specified output (PSS C TARGET ID): Vmin + 2.0v

Vmin: Sensor output level (dark voltage) when the sensor output
is zero.

2) The calibration plate in the sensor section is shifted to the sensor

position (driven by the solenoid), and the reflection ratio of the cali-
bration plate is read by the sensor at the LED drive voltage (Vref)
obtained in the above procedure.
The sensor output level at that time is stored as Vssc.

(Calibration 2 of the image density sensor for color) 
This operation is automatically performed before the harf tone image
density correction and the high density (saturation density) image cor-
rection. 
The calibration plate in the sensor section is shifted to the sensor po-
sition (driven by the solenoid) to obtain the LED drive voltage (Vrefc)
so that the sensor output level is Vssc. 
The obtained LED drive voltage (Vrefc) is used for detection of the im-
age density.

(Calibration of image density sensor for monochrome)
The sensor LED drive voltage is changed and the reflection lights
from the transfer belt surface are read by the sensor. Obtain the sen-
sor LED drive voltage (Vrefk) when the sensor output voltage is at the
specified level (Reference Level (PSS B TARGET ID)(Vmin + 2.6v).

Vmin: Sensor output level (dark voltage) when the sensor output is
zero. 

The obtained LED drive voltage (Vrefb) is used for detection of the
image density. 

A change in the sensitivity due to dirt on the OPC drum marking sen-
sor and a change in the temperature is corrected to make precise de-
tection of the number and the position of the OPC drum marking. 

By detecting the OPC drum marking position, the following operations
are performed. 

1) Control of the toner image patch formation position in the high

density (saturation density) image correction and the half tone im-
age correction.

2) Control of each OPC drum phase in printing

3) By detecting the number of the OPC drum marking, the type of the

OPC drum is identified and the laser beam power and the main
charger grid voltage are switched depending on the OPC drum
type.

(Calibration)
The sensor LED drive voltage is changed and the reflection lights
from the OPC drum surface are read by the sensor. Obtain the sen-
sor LED drive voltage (Vrefd) when the sensor output voltage is at the
specified level (3.6V). 

Vmin: Sensor output level (dark voltage) with the sensor input is zero.

LSU

LSU

LSU

LSU

Y

C

M

BK

Drum mark
sensor

Drum mark
sensor

Drum mark
sensor

Drum mark
sensor

Humidity sensor

Calibration plate

Image density sensor

Sensor drive (LED) voltage

IMAGE DENSITY SENSOR CALIBRATION 1 (for Color sensor)

Sensor output
level (voltage)

V min (LED off)

Reference Level
(PSS C TARGET ID)
(Vmin + 2.0v)
(Set by SIM44-4)

Reference sensor drive (LED) voltage (Vref)

Used by sensor adjusting
sheet and SIM44-4

Reference Level
(Vssc)

Step 2

Used by sensor reference
plate and SIM44-4

Step 3

Step 1

Sensor drive (LED) voltage

IMAGE DENSITY SENSOR CALIBRATION 2 (for Color sensor)

Sensor output
level (voltage)

V min (LED off)

Reference sensor drive (LED) voltage (Vrefc)
(Actual sensor drive (LED) voltage

Reference
Level (Vssc)

Used by sensor calibration
plate and SIM44-4

Step 1

Step 2

Sensor drive(LED) voltage

IMAGE DENSITY SENSOR CALIBRATION 1 (for Monochrome sensor)

Sensor output
level (voltage)

V min (LED off)

Reference Level
(PSS B TARGET ID)
(Vmin + 2.6v)

Set by SIM44-4
(Transfer belt serface level)

Step 1

Step 2

Reference sensor drive (LED) voltage (Vrefk)
(Actual sensor drive (LED) voltage

AR-C150

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