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2022 Student Challenge – Optical Profilometry


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The goal of the ASPE 2022 Student Challenge is to measure 8 mm x 8 mm area surface topography of an Alvarez freeform sample with about 50 µm PV. Two main components that each team will be supplied are an Air-bearing XY translation stage capable of 10 mm travel in each axis and a Blu-ray Optical Pick-up Unit (OPU) with an UV laser, focusing lens, flexure guided voice coil lens actuator, and position sensing detector. Surface scanning can be achieved using the built-in photodetector of the OPU by  tracking the focal point by moving its wire flexure guided voice coil and measuring the current supplied to the coil to track. One can calibrate displacement of the OPU lens as it relates to current supplied to the coil using any of the supplied equipment that can measure displacement in terms of meters (mm or µm or nm). Reference surface topography measurements of the freeform sample performed using a commercial optical surface metrology instrument will be used to determine the fidelity of the developed measurement process by the student teams.

References

Koster, μflow – A compact fluorescence detection system that uses DVD pickup for the optical detection of beads, masters thesis, University of Twente, 2011

http://www.diyouware.com/DiyoPCB-MKI

Hwu and Boisen, Hacking CD/DVD/Blu-ray for biosensing, ACS Sensors, 3(7), p.1222-1232, 2018

Sekhar and Ajoy, Synchronous detection to reduce offsets in focus error of an optical pickup unit, IEEE transactions on instrumentation and measurement, vol. 70, 2021