StarBright User Manual
54
9.2.2
Zoom
The
Zoom
function can be useful for laser power tuning and peaking. Small fluctuations in energy
are more easily seen in this mode.
Press the
Zoom
soft key to focus the Bargraph on the present reading. The Bargraph will show 20%
of the full scale centered on the present reading. Thus, if the full scale of the Bargraph is 20 Joules,
and your reading is 15 Joules, pressing
Zoom
will make the Bargraph scale range between
approximately 13 and 17 Joules.
The legend is highlighted when
Zoom
is active (see
on the right below). Note that the
fiducial marks of the Bargraph are further apart, indicating that
Zoom
is engaged.
Figure
9-3 Pyroelectric Power Bargraph
Figure
9-4 Pyroelectric Power Bargraph with Zoom
Press the
Zoom
key again to return to the unexpanded Bargraph display.
9.2.3
Offset
The
Offset
function can be used to subtract the background and set the current reading to zero.
For Thermopile and Photodiode Sensors Measuring Power
The PD300 and PD300-3W sensors have automatic background. The
Offset
function can be used to
subtract the residual background signal that remains, if desired. The same holds true when the
ambient environment has a thermal background, such that StarBright shows a nonzero power
reading even when there is no laser, you can subtract the background using the zero function. For
example, the StarBright display reads 0.1mW when the laser is blocked and 20.5 mW with laser
power applied. In this case, the true power is 20.5 - 0.1 = 20.4 mW. To subtract the background,
press
Offset
while the laser is blocked. The StarBright will now read zero (0.0), and the 0.1 mW
background will be subtracted from all subsequent readings. The laser power reading will thus be
20.4 mW.