THORLABS PDP90A, User Manual

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Lateral Effect Position Sensor Chapter 2: Description
17149-D02 Page 6
Low power levels should be used for the position sensor. For the PDP90A, the
max photocurrent is 40 µA. Using the photosensitivity curve below (
Figure 2 ), the
system saturation power can be calculated as:
40 μ
The KPA101 K-Cube PSD Auto Aligner has a sample resolution of 16-bits with
an input voltage range of ±15 V (30 V range), or a voltage resolution of:
30
2
0.458
100
From this, the minimum power required can be determined based on the required
accuracy. For example, if the user requires an accuracy of 1%, the minimum
photocurrent is I
Step
x 100 = 0.458 µA. Use the formula below to find the minimum
optical power for a given wavelength.
0.458 μ
Figure 2 Photosensitivity of PDP90A
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
320 420 520 620 720 820 920 1020 1120
Responsiv
ity
(A/W)
Wavelength λ (nm)
SPECTRAL RESPONSE