Service manual

5.4 AUTO POWER CONTROL (APC)

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 output light intensity is

monitored through a photodiode (PD) enclosed in the laser diode. The

photodiode passes an electrical current that is proportional to the light

intensity. The output is not affected by temperature, so it faithfully reflects the

changes in the LD output, without adding anything itself.

Just after the main switch is turned on, the current drive IC on the LD drive

board energizes the laser diode to full power (power level 32) and stores the

output of the photodiode as a reference. The IC monitors the current passing

through the photodiode. Then it increases or decreases the current to the

laser diode as necessary, comparing it with the reference level. Such auto

power control is done during printing while the laser diode is active.

The laser power level is adjusted on the production line. Do not touch the

variable resistors on the LD unit in the field.

Detailed

Section

Descriptions

LASER EXPOSURE

SM 2-71 A166/A187/A189

CÓPIA NÃO CONTROLADA