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AR-651/810  SCANNING SECTION  6 - 10

A CCD (charge-coupled device) is used to produce an electrical signal corresponding to the reflected light

amount from the original. The CCD is a one-chip opto-electronic conversion device, comprised of several

thousand light-receiving elements arranged in a line; each one of them is a few microns square.

This model is equipped with a CCD which has 7,500 light-receiving elements.

Each element of the light-receiving section consists of the semiconductive layers P and N. When the light

irradiates the element, the light energy produces a (-) charge in the P layer, the amount of the charge

produced is proportional to the energy and irradiating time. The charges produced in the light-receiving

section are then sent to the transfer section where they are shifted by the transfer clock from left to right as

shown in the figure below, and are finally output from the CCD. At this time, to increase the transfer speed

of the CCD, image signals in the even-number and odd-number elements are separated and output in

parallel via two channels.

Signal voltages read by the CCD have the following characteristics.

(1) Light source has variation in its light distribution.

(2) Since the light beam reflected from the original is converged using a lens, the light path is the

shortest at the center of the CCD and the longest at ends. This causes difference in the amount of

light reaching the CCD (i.e. the light amount is maximum at the CCD center, gradually decreases

towards the ends).

(3) Each of the 7,500 elements varies slightly in their opto-electronic conversion efficiency.

These variations need to be corrected and this correction is referred to as shading correction. Based on the

black and white data obtained in advance, a normalization process using the following formula is applied to

the raw image data to correct lighting variance and element variation of the image data.

I = k ×

(S — K)

(W — K)

k : Coefficient

S : Image data before correction

K : Black data (stored in “black” memory)

W : White data (stored in “white” memory)

1

7497 7498

7499 7500

2

3

4

Transfer section

Light receiving

section

Transfer section

Shift register

Transfer clock

Light energy

layer N

layer P

Details of light receiving element

Transfer clock

AR-651/810  SCANNING SECTION  6 - 11

This circuit detects the size of original (standard sizes only) using the reflection type photosensors ar-

ranged on the base frame of the scanner unit.

The reflection type photosensors are placed on the base frame of the scanner unit as shown in the Fig. 6.6-

1. Each sensor consists of an infrared light emitting diode (LED) on the light emitting side, and a phototransistor

on the light receiving side.

When there is an original on the original glass, light beams from the LEDs are reflected by the original and

led to the phototransistors. This means that the size of the original is detected by checking which

phototransistors are turned on or are not.

(1) When the copier is in the original size detection mode, the carriage-1 is set at its home position.

(2) When the RADF is opened, the sensors receive the light reflected from the original and if one of the

matrix conditions shown in (4) for original sizes is satisfied, the size of the original is instantly de-

tected.

(3) The output signal from each sensor is input to the CPU on the scanner control PC board to determine

the size of the original.

V

DD

P81

33

30

29

28

GND

PWA-SLG

P80

P96

P95

APS-4

APS-3

APS-2

APS-5

Reflection type

photosensor

[LT Series]

[A4 Series]

V

DD

P81

33

32

30

29

28

GND

PWA-SLG

P80

P96

P95

P94

APS-4

APS-3

APS-2

APS-1

APS-5

Reflection type

photosensor

Original

Original glass

APS-2

APS-3

APS-4

APS-1

APS-5

Original glass

Original

APS-4

APS-5

APS-3

APS-2

AR-651/810  SCANNING SECTION  6 - 12

ST

LT

LG

LD

ST–R

LT–R

APS-5

APS-4

APS-2

APS-3

A5

B5

A4

B4

A3

A5–R

A4–R

B5–R

APS-5

APS-1

APS-2

APS-3

APS-4

AR-651/810  SCANNING SECTION  6 - 13

(4) Original size is determined by the combination of the presence/absence of signals which are output at

each detection point. The combination chart for size determination of A4 series and LT series are as

followed.

[A4 Series]

Size

APS-1

APS-2

APS-3

APS-4

APS-5

A3

0

0

0

0

0

A4

0

0

0

0

1

B4

0

0

0

1

0

B5

1

0

0

1

1

A4-R

0

0

1

1

0

A5

1

0

1

1

1

B5-R

0

1

1

1

0

A5-R

0

1

1

1

1

[LT Series]

Size

APS-2

APS-3

APS-4

APS-5

LD

0

0

0

0

LT

0

0

0

1

LG

0

0

1

0

LT-R

0

0

1

1

ST

1

0

1

1

ST-R

0

1

1

1

Code

Output signal

Original

1

H

Absent

0

L

Present

* When the APS operation sensor is OFF;

• The following points are determined by the output signals from APS sensors

Size (The combination of the signals satisfy the above chart)

: Size is displayed on the control panel and an appropriate paper and reproduction ratio are selected.

Size retention (The combination of the signals do not satisfy the above chart)

: Retains the latest original size recognized (or no original state) until a new paper size is recognized.

No original (output from all the sensors are “1”.)

: Reproduction ratio and paper size are not selected.

• Size change is always observed and detected.
• Carriage-1 stays at the standby position even if the reproduction ratio changes corresponding to the change of

the original size.

* When the APS operation sensor is ON;

Retains the latest original size (or no original state) recognized right before the APS operation sensor is turned
ON regardless of the state of the APS sensor output signals.