Specifications

With the copier set into the Auto Exposure mode (the Touch Panel showing
"Auto Expo."), press the Start Key. Then, LA1 is turned ON at the central
manual exposure level (EXP5) and the Scanner leaves its home position
(PC1 blocked) to travel up to the leading edge position of the original
[where the Image Leading Edge signal (BASE) goes from HIGH to LOW].
This starts the automatic exposure control.
<Operation/Control>
Light reflected off the original strikes PD1H (photodiode) and PWB-H
converts its intensity to a corresponding voltage value, outputting an AE
Sensor analog voltage to Master Board PWB-A. (The higher the intensity of
the light striking PD1H, the lower the AE Sensor analog voltage.)
Control by AE Sensor Board PWB-H
Receiving the AE Sensor analog voltage, PWB-A compares it with the
reference voltage. It increases the Lamp voltage if the input voltage is
higher than the reference, and decreases it if the input is lower than the
reference. It varies the duty ratio of the pulse width of the Exposure Lamp
Control signal (AVRPWM) and outputs the pulse signal to Exposure Lamp
Regulator PU5.
Control by Master Board PWB-A
PU5 controls the Exposure Lamp voltage according to the input pulse
signal.
Control by Exposure Lamp Regulator PU5
Original
Light
Intensity
Analog Output Voltage
Light High Low
Dark Low High
M-39