Geometric Modeling of a Multi-Aperture-Array-Projector for 3D Measurement


A common technique to achieve fast, accurate, and contactless 3D shape measurement is to implement a stereophotogrammetric setup paired with active illumination. These systems provide greater measurement accuracy than time-of-flight sensors.

Commercial off-the-shelf digital projectors that provide a source of active illumination are limited in projection speed <100 Hz, limiting the 3D measurement frame rate between 1-60 Hz since N unique illumination patterns must be projected through a single aperture.

Fraunhofer IOF has developed a projector, termed a Multi-Aperture-Array-Projector (MAAP), capable of projection speeds <3 kHz, thus permitting 3D measurement frame rates >330 Hz. This is achieved as N unique illumination patterns are projected through N different apertures.

In single camera setups, the projector itself can be calibrated such that the recovery of 3D coordinates occurs through camera-projector triangulation instead of the usual stereophotogrammetric approach. Previous studies have calibrated commercial single aperture Digital Light Projectors (DLP) by treating them as inverse cameras since the projector chip instead projects an image into space. As a result, the pinhole model can be applied to create a projector homography between 2D image coordinates and 3D world coordinates.

This method of calibration cannot be performed on a MAAP as no single chip is responsible for pattern projection. Instead, a cluster of microprojection units are responsible for the projection of a single image.

This project is focused on developing a MAAP calibration technique that enables single camera 3D measurement, resulting in decreased cost of high-speed 3D measurement systems that utilize a MAAP.