Specifications

3.6 AUTOMATIC IMAGE DENSITY DETECTION
Light from the exposure lamp is reflected from the original and travels to the
lens [A] via the mirrors. The auto ID sensor [B], a photodiode, is mounted on
the upper front frame. The sensor cover [C] has a hole in it to allow light to
fall directly onto the sensor. Sampling starts 10 millimeters from the leading
edge of the original and continued to 40 millimeters from the leading edge of
original in full size mode.
The length A and B in each reproduction ratio are calculated as follows:
The photosensor circuit converts the light intensity to a voltage. The detected
voltage is amplified and sent to the main PCB. The CPU stores the voltage of
each sampled point in RAM. It then computes the image density of the
original from the maximum sample voltage and changes the development
bias accordingly. (See page 2-30 for details.) The exposure lamp voltage is
constant regardless of the image density of the original. (See page 2-18 for
details.)
70 mm
B
Sampled area
A
[A]
[C]
[B]
A=
40 mm
Reproduction Ratio (%)
x100
B=
10 mm
Reproduction Ratio (%)
x100
1 December 1990
2-16