Canon 1000 Service Manual page 117

The video signals from the video controller
PCB are 8-bit signals and assume a value between
0 (00H) through 255 (FFH). Pulse signals that suit
the signals are generated in the 400-/200-/266-line
laser drive signal generation block. (Figure 3-418)
The selector switches between 400 lines and
200 lines and turns off or on the laser in response
to the mode signal.
The laser drive signals generated in this way
are applied to the semiconductor laser to turn on
the laser beam.
The laser beam has characteristics which
cause its intensity to increase rapidly when the
applied current exceeds the activation current.
Since the activation current (I) varies according to
the ambient temperature, the intensity at the point
of activation is monitored at all times and the
activation current is controlled so as to maintain a
specific intensity.
The laser power adjustment mechanism used
when servicing the CLC1000 varies the activation
current (by volumes VR1 and VR2 on the laser
power adjustment PCB), thereby properly setting
the upper and the lower limits of the intensity.
If a correct intensity cannot be obtained
because of an error in the semiconductor laser, the
activation current will abnormally increase; such a
condition is detected by the activation current error
signal (E100-xx02).
COPYRIGHT © 2001 CANON INC. CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATION AND TIMING
ON ON
Figure 3-418
Intensity
Point of activation
Intensity
Upper
limit
Point of activation
Activation current
Intensity
Lower
limit
Point of activation
Activation
current
Figure 3-419
ON
ON
I
Current
Current
ON current
Current
ON
current
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