Editing Zermatt/Research/Photometric Stereo

= Photometric Stereo for Ear Scanning =
''May 7, 2026''

== Technique ==
Single fixed camera captures images illuminated sequentially from different LED positions around a ring. Surface normals and 3D depth reconstructed computationally. Reported accuracy: 0.05mm. Introduced by Wolfgang Herwald, April 28, 2026.

== MVPS Studio (Reference Implementation) ==
* Developer: Dr. Berkan Lafci, ETH Zurich | Published: February 2024
* GitHub: https://github.com/berkanlafci/mvpsstudio
* Hardware: 24-LED NeoPixel ring (~66mm OD), Raspberry Pi 5, Ubuntu 22.04, GPIO pin 10
* Software: Open-source deep learning reconstruction pipeline for surface normal estimation

== Optics ==
* '''Diffuser:''' Rosco Cinegel 3026 Tough White Diffusion (=LEE 216), 20x24" sheet — 36% transmission (Y), 1.5 stop loss. Cut to fit over LED ring to soften point sources.
* '''Polarizers:''' Selens 7.8x11.8" adhesive linear polarizing sheets (x2) — cross-polarization eliminates specular glare from skin. One sheet over LED ring (source), one over camera lens (analyzer), rotated 90° to each other.

== Calibration Spec ==
LEE 216 = Rosco Cinegel 3026 = 36% luminance transmission, 1.5 stop reduction. Use this when accounting for diffuser attenuation in photometric stereo light intensity calculations.

== Controller ==
Raspberry Pi 5 (8GB RAM), Ubuntu 22.04. GPIO pin 10 (physical pin 19) for LED data line.