Toshiba DP120F Service Manual page 275

When a forward voltage is applied to this semiconductor laser, the holes and electrons
combine at the junction area as in the case of the diode, and the energy discharged upon
the joining of the holes and electrons is discharged as light. The discharged light is en-
closed in the junction area, and is reflected by the reflecting surfaces of both sides, being
reflected reciprocally within the junction area.
Due to the consecutive joining holes and electrons as a result of the reciprocal move-
ment, the light is correspondingly amplified. Then, when the light has become sufficiently
amplified, the semiconductor laser emits a laser beam through the reflecting surfaces.
This is an invisible laser radiation, but it is a good monochromatic light beam with high
luminance at a large-volume output. Consequently, the laser beam can be condensed by
a lens to an extremely small focal point with high luminance, thereby permitting its use in
a laser facsimile.
(2) Laser drive
The Main PBA controls the laser beam drive signal (VIDATA) by the print data.
The laser beam drive signal is sent to the laser driver in the LSU to control the current
flowing to the laser diode.
The laser diode generates a laser beam when a current that equals or is greater than the
stipulated value (I th) flows.
March 2000 © TOSHIBA TEC
I th
Laser driving current
Fig. 5-3-9
5-15 DP120F/DP125F Mechanical Description
05-03-09