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3-24

Optics unit

(7)

Optics unit

1)

Construction of optics unit

• The optics unit consists of exposure lamp, lens and reflector mirrors mounted

on fixed as well as scanning assemblies. It uses a slit exposure method that

scans the original with the full-speed unit and forms the image on the drum.

• While moving the full-speed unit with the optics motor, the exposure lamp

illuminates the original. The reflected light from the original is put on the

charged drum with 6 reflector mirrors and lens to form the electrostatic latent

image.

Part description

Function

1

Full-speed unit

Includes exposure lamp and no.1 mirror, to scan
the original.

2

Half-speed unit

Includes no.2 and no.3 mirrors, and guide reflected
light from no.1 mirror to lens. Scanning at half speed
of full-speed unit keeps optical path length from
original to lens constant.

3

Optics cooling fan

Cool optics unit.

4

Optics unit drive motor

Stepping motor which drives full-speed unit and half-
speed unit.

5

Drive belt

Transmit driving force from optics unit to full-speed
unit and half-speed unit.

6

Lens

Form image on drum with reflected light from the
original.

7

4/5 mirror unit

Includes no.4 and no.5 mirrors which guide light from
lens to no.6 mirror. Change optical path length  for
zoom ratios.

8

No.6 mirror

Make incidence reflected light from no.5 mirror to
drum.

9

Exposure lamp

Halogen lamp which illuminates the original.

10

AE sensor

Detect reflecting light density from original, and read
density of original into CPU P.C.B..

Sub Assemblies

3-25

2)

Driving optics unit

• The optics unit (full-speed unit and half-speed unit)is driven by the optics unit

motor.

The optics unit motor revolution drives the full-speed unit and half-speed unit

via optics unit motor belt, full-speed half-speed drive pulley, full-speed unit

drive belt and half-speed unit drive belt.

• The pulley diameter which drives half-speed unit is 1/2 of that driving the full-

speed unit, therefore, the full-speed unit moves at twice the speed of half-

speed unit so the optical path length from the original to the lens is kept

constant.

• The full-speed unit is positioned at the optics home position by the full-speed

unit position detecting plate and the full-speed unit optics home position

sensor.

• The full-speed unit holds the exposure lamp and the No.1 mirror. It scans the

original with the exposure lamp, forwards the reflected light to the No.3 mirror

via No.1 and No.2 mirrors and forms the image on the drum after it passes

through the lens.

Belt drive shaft

Exposure lamp

Full-speed unit
home position
sensor

Pulley 2

Pulley 1

Half-speed unit drive belt

Full-speed unit drive belt

Half-speed unit

Slide rail

Optics drive motor

Optics drive
belt

Optics drive pulley

Aperture
plate

No.1 mirror

No.2 mirror

No.3 mirror

Exposure lamp harness

Half-speed

unit position

detecting plate

Full-speed unit

3-26

3)

Zoom up/down
The following operations are required for zoom.

a) Changing the optical path length between lens and mirrors
b) Setting the scanning speed of optics system
c) Setting luminous exposure
d) Lighting blacking prevention lamp (prevent black belt at both ends in zoom

down)

a) Changing the optical path length between lens and mirror

• For the reduction mode, the further from the lens, the formed image is smaller

with the reference of full size position, and the distance between the lens
and the formed image position on the drum is shorter.

• For the enlargement mode, the original comes nearer to the lens, the

formed image is larger, and the distance between the lens and the formed
image position on the drum is longer.
Accordingly the 1:1/reduction/enlargement is set by moving the position of
lens and mirrors (4/5 mirror unit).

• The copy ratio operation is done by moving the lens and the 4/5 mirror with

the stepping motor as shown below.

• When the rotary pulse is outputted from CPU control P.C.B. according to

the copy ratio, the positioning is performed with the lens position detecting
plate and the lens position sensor.

• For the positioning in driving reverse direction, after driving more than the

target value to absorb the backlash of gear, return to the normal rotation,
drive and stop.

• The movement of 4/5 mirror is done by the same manner as lens with the

mirror moving motor.

• The position of 4/5 mirror is determined with the mirror position detecting

plate and the mirror postion sensor.

4/5 mirror u movement length

200%

b direction   Aprrox.   49mm

100%

0

50%

b direction  Approx.  95mm

Lens unit movement length

200%

a direction   Aprrox.   47mm

100%

0

50%

a direction  Approx.  190mm

Half-speed
unit

Full-speed
unit

Lens

4/5 mirror

b

Drum

Enlargement

a

b

Reduction

100%

Sub Assemblies

3-27

• Lens movement

Lens unit

Forward
direction

Reverse
direction

Lens position
detecting plate

Lens home
position sensor

Slide rail

Drive belt

Lens drive
gear/pulley

Stepping motor

Forward direction

Reverse direction

No. 4/5 mirror

Mirror position
detecting plate

Mirror drive rack

Stepping motor

Mirror home position sensor

Mirror drive gear

• Mirror movement