Sharp SF-1014 Service Manual download pdf (Page 35)

2. Optical unit correction (Dirt correction)

The purpose of this correction is to maintain the copy density even

though the optical unit is contaminated and to reduce troublesome

cleaning of the optical unit.

When the lamp, the mirror, and the reflector are dirtied with dusts and

toner, the light quantity radiated to the photoconductor drum is

reduced, increasing the copy density and producing unnecessary

background copy.

The above trouble is removed by changing the copy lamp voltage to

adjust the copy density. It, however, requires serviceman’s operation.

In this model, the AE sensor senses dirt on the copy lamp, the mirror,

and the reflector, and the copy lamp light quantity is changed accord-

ing to the dirt level to reduce the change in the copy density due to

the optical unit dirt.

When the optical parts are dirtied, the reflection rate is reduced to

reduce the quantity of light which is passed to the optical dirt sensor.

In this manner the dirt level is sensed.

[Initial setting]

After making a copy by Simulation 46, the scanner unit stops at the

position of the standard reflection plate on the back of the document

stopper to light the copy lamp at a certain level, and the AE sensor

output level at that time is recorded as the reference value. (The

reference value can be checked with Simulation 44-2.)

[Correction timing]

The correction is performed after the copy cycle after turning on the

power, or after the specified time of rotation of the photoconductor

drum.

[Correction operation]

The same operation as the initializing is performed to change the

copy lamp voltage until the AE sensor output level reaches the same

level as the reference value, performing the correction.

The copy lamp voltage is revised to a new value at every correction,

and the new value will be used in the next correction.

(The correction voltage value can be checked with Simulation 44-3.)

[Correction timing]

• When the power is turned on.

• Once for every 155 min. of drum rotation.

AE SENSORMirror

Referance refrection plate

Copy

lamp

AMP

A/D

converter

Timer

Arithmetic unit

Copy lamp control

clock generator

Driver

AC power supply unit

(Copy lamp control circuit)

Copy lamp

referance control

level

EE-PROM

MAIN CONTROL PWB

CPU

Table glass

Referance refrection plate

AE sensor

(Next to the lens)

Diagram of correction system in the optical section

YES

START

The scanner unit stops

at the standard reflection

plate position.

Correction mode ?

Optical dirt sensor

reference level

(DSENS) memory

END

The scanner starts

initializing.

Copy lamp ON

(67.7V/135V)

Copy lamp ON

(67.7V/135V)

No correction is made.

Copy lamp ON

Copy lamp voltage

0.3V (0.6V) down

Copy lamp ON

Copy lamp voltage

0.3V (0.6V) up

Copy lamp voltage

correction

Copy lamp correction

voltage calculation

Sensor output =

Reference level

(DSENS) ?

Sensor output

< Reference level

(DSENS) ?

Sensor output =

Reference level

(DSENS) ?

Sensor output =

Reference level

(DSENS) ?

YES

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Sharp SF-1014 Service Manual Page 35

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