Auto Power Control (Apc) - Ricoh A-P3 Service Manual

6 November, 2001 LASER EXPOSURE

6.4.2 AUTO POWER CONTROL (APC)

The LD board drives the laser diode. Even if a constant electric current is applied to
the laser diode, the intensity of the output light changes with the temperature. The
intensity of the output decreases as the temperature increases.
In order to keep the output level constant, the LD board monitors the electrical
current passing through the photodiode (PD). Then it increases or decreases the
current to the laser diode as necessary, comparing it with the reference level. This
auto power control is done just after the machine is turned on and during printing
while the laser diode is active.
The reference levels are adjusted on the production line. Do not touch the variable
resistors on the LD b oard in the field.
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