Primes HP-MSM-HB, Оригинальное руководство пользователя

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93 Revision 00 EN - 01/2021
HP-MSM-HB
35,0(6
A total of four states can always be differentiated on the way from low to high pulse frequencies or from short
to long integration times. This is demonstrated by the following example for measuring pulsed irradiation dur-
ing untriggered operation.
t in μs
∆
t in μs
I in W/cm²
Fig. 22.4: Measuring with different integration times

12 – 200 µs: Sporadic measuring of pulses

200 – 400 µs: 1 pulse

200 – 2 ms: Quantization noise cause by a varied number of pulses

2 – 200 ms: Virtually continual integration time control
Fig. 22.4 on page 93 shows pulsed irradiation. The pulse pauses amount to 200 µs. The required integra-
tion time of the sensor correlates directly with the intensity of the laser beam.
If it is smaller than the pulse pause as in Case 1, no more than one pulse will be in the measurement statisti-
cally speaking. The probability of there being one pulse during each measurement of integration time control
as well as during the actual measurement is slim.
If the optimal integration time falls exactly between the simple and double duration of the pulse pause, there
will always be just one pulse in each measurement (Case 1). This is the perfect state for measuring on one
plane. The caustic can also be measured with this setup, since the dynamics of the CCD sensors is 55 dB
for a single pulse, with the intensity only varying by a factor of 5 in the relevant caustic range. Here it is im-
portant to make sure that the signal saturation for the measurement in the beam waist is as high as possible.
Only then is it possible to ensure that there is a sufficient S/N ratio when measuring a plane far outside of the
focus.
Case 3 describes a situation where the integration time falls between the simple duration and the duration
times ten of the pulse pause. Within this range, every pulse is more or less noticeable as a clear signal jump
during the integration time. Integration time control is only possible with quantization. The measuring results
often have a bad S/N ratio or the signal level is too high.
If the integration time increases even more, the signal jumps become flatter. Integration time control pretty
much operates continuously (Case 4). The laser being measured can now be measured as a cw laser.
The neutral-density filters, which can be inserted into the optical path, make it possible to always work within
the desired range 1 - 4.
Furthermore, as was mentioned in the initial consideration, the HP-MSM-HB is equipped with quite a few op-
tions for triggering. Combined with integration time control and delay time control, it is possible to take good
measurements even in Case 1.