Sharp AR-651 (serv.man23) Service Manual ▷ View online
AR-651/810 SCANNING SECTION 6 - 2
6. 2. Construction
The construction and purpose of the scanning system are described in this section.
(1) Original glass
This is the glass on which originals to be copied are placed. The light from the exposure lamp is irradiated
to the original through this glass.
(2) Carriage-1
The carriage-1 consists of the exposure lamp, lamp inverter, reflector, mirror-1, etc. It is driven by the
scanner motor and scans the original on the glass.
a. Exposure lamp
This lamp is the light source to irradiate the original on the glass (one 29W Xenon lamp).
b.
Lamp inverter
This inverter controls lighting of the Xenon lamp.
c. Reflector
This is a plate to direct the light from the exposure lamp efficiently to the surface of the original on the
glass.
d. Mirror-1
This is a mirror to direct the reflected light from the original to the mirror-2 that is described later.
Original glass
Exposure lamp
Original
Reflector
Mirror-1
AR-651/810 SCANNING SECTION 6 - 3
(3) Carriage-2
The carriage-2 consists of mirror-2, mirror-3, etc. and directs the reflected light from the mirror-1 through
mirrors-2 and -3 to the lens.
This carriage-2 is driven by the scanner motor as the carriage-1, at half the scanning speed of carriage-1
(the scanning distance is also half of carriage-1).
(4) Lens unit
The light reflected from mirror-3 is led to the CCD placed at the focal point of the lens which is fixed in
position.
(5) CCD board
Processes such as signal amplification, signal integration, A/D conversion and shading correction are
applied to the electrical signal which has been converted by the CCD.
(6) Automatic original detection sensor
The size of the original placed on the glass is instantly detected using the automatic original detection
sensors (APS sensor) fixed on the optics base frame without carriage-1 having to move.
AR-651/810 SCANNING SECTION 6 - 4
Carriage-1
Carriage wire
Scanner motor
Pulleys for carriage-2
6. 3. Operation
6. 3. 1. Scanner motor
(a) Scanning original on original glass
This motor drives the carriages-1 and -2 through the timing belt and carriage wire. The scanner motor
first drives carriages-1 and -2 to their respective home positions. The home positions are detected
when carriage-1 passes the home position sensor. When the [START] key is pressed, both carriages
start to move and scan the original on the glass.
(b) Scanning original on RADF
Carriage-1 starts at the shading position during the shading correction. Then moves to the fixed posi-
tion for RADF exposure operations.
Ø20
Ø30.83/2GT-Z84
Ø20
2GT-Z24
Motor pulley
Idler pulley
C a r r i a g e - 2
Wire pulley
Exposure glass for scanning operation
Shading correction plate
Slit glass for RADF exposure operations (Scanner fixed)
AR-651/810 SCANNING SECTION 6 - 5
6. 3. 2. Two-phase motor drive circuit (fixed-current type)
The scanner motor is driven by the unipolar transistors as shown below. The current chopper method is
employed by the driver circuit to improve motor torque STK672-080 (IC4).
15
14
13
12
11
10
9
8
6
7
ENABLE
Mol
RESET
M3
CLOCK
CWB
M2
M1
Vcc2
Vref
A
A
B
B
BB
PG
SUB
5
4
3
2
1
Excitation
mode setting
Switching pulse
ON/OFF detection
Excitation
status monitor
CR oscillation
Phase
counter
Generation of
reference clock
PWM control
Generation of phase
excitation signal
Generation
of pseudo
sine wave
Switching
current
fraction ratio
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