Ricoh FT5034 Service Manual page 33

4. Automatic Image Density Sensing (ADS)
This copier has an ADS system for good quality copy images. Light from the
exposure lamp is reflected from the original and travels to the ADS sensor on the
lens base via the mirror.
Sampling starts 3 millimeters from the leading edge of the original in full size
mode.
The length and width differ for each reproduction ratio.
The photosensor circuit converts the light intensity to a voltage.
The detected voltage is amplified and sent to the main board.
It then computes the background density of the original from the maximum
sample voltage and changes the development bias accordingly.
The exposure lamp voltage is constant (equal to the voltage at the manual
density level 4) regardless of the image density of the original.
1) Comparison of the manual image
density key and the auto image
density key.
When the manual image density
mode is selected, the exposure lamp
voltage and the development bias
for each level are as shown to the
right.
Only the exposure lamp voltage
varies according to the input.
This is based on prevention of ID
level decrease at high manual image
density levels.
Original scale
Manual image
density mode
Output voltage + Development Bias Control
V
0
V -4 V
0 0
(V is the voltage of the lamp at the
0
manual image density level 2.)
- 32 -
V +11 V +23
0 0
+6 V
V +16
0
+23
0