head
fs_laser_mod
fmod
Thermal
This parameter affects the performance and stability of the lens positioning
servo. It has been set to 0, and should never be changed in the field.
This parameter, and fpower, should always be set to 0 except during head alignment
in the factory. When fmod and fpower are both set to 0 (the normal case) the
modulation is optimally adjusted internally and the focus laser power set by the
"hdm sr" setting. The rest of this description applies only if these values are
not set to 0.
If fmod is nonzero, it specifies the modulation depth of the light output from the
autofocus laser diode. The focus laser beam is amplitude-modulated to improve the
noise rejection of the optical distance sensor.
The modulation depth depends on the fpower setting. If fpower is changed, fmod
has to be changed to maintain the same modulation depth.
The units are not calibrated.
The output of the optical sensor is proportional to the modulation depth and not
to the average output power of the diode. To increase the amplitude of the signal
emerging from the optical distance sensor, fmod, not fpower, should be increased.
If fmod is too large, the sinusoidal modulation becomes clipped, which may
degrade the sensor's performance.
integer