THORLABS PDP90A, User Manual

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Lateral Effect Position Sensor
Page 3 Rev G, May 11, 2017
Chapter 2 Description
The PDP90A is a two-dimensional, tetra-lateral position sensing detector (PSD)
that provides X and Y-axis positional information. It is designed to work with
Thorlabs’ KPA101 K-Cube Auto-Aligner. This sensor can be used for general
alignment purposes, as well as precise position measurements. This sensor
gives the position of any spot contained within the active region and supports
spot sizes up to 9 mm in diameter. A spot between Ø0.2 mm and Ø7 mm is
recommended.
Thorlabs also manufactures the PDQ80A quadrant position detector for precision
alignment needs.
2.1. Setup Instructions
a. Unpack and mount the PDP90A position-sensing detector. An AS4M8E
M4 to 8-32 thread adapter is included for customers using metric opto-
mechanics.
b. Connect the sensor to a KPA101 K-Cube Auto-Aligner.
c. Follow the directions in the controller’s operating manual to ensure that
the position-sensing detector is properly communicating with the
controller.
d. Send a beam onto the active area for measurement. The spot size input
beam should be between Ø0.2 and Ø7 mm. For best results, the spot
should be located within the center 80% of the surface of the detector (a
7.2 mm x 7.2 mm square). Adjust the power level so that the
SUM output voltage is
≤ 4 V. This ensures the best signal-to-noise ratio
and avoids signal saturation.
2.2. Details of Operation
This section of the manual discusses the operating principles of 2D lateral effect
position sensing detectors and includes key equations for understanding their
output signals.