Three-dimensional optical metrology and models for non-contact diffuse optical tomography of small animals

Abstract

We introduce a novel approach for calibrating an axis of rotation in a 3D optical metrology system. The system uses a stereo camera pair, along with rotation and translation stages for obtaining a 3D model of the surface of small animals. The metrology system will be part of a fully non-contact diffuse optical tomography (DOT) scanner for small animal imaging. The rotation axis calibration technique is based on measuring, with the stereo pair, the 3D position of a small ball as it is moved by the rotation stage (turntable). Our system has the advantage of using the tomograph's laser beam to measure the outer shape of the subject, thereby reducing overall system complexity, and allowing simultaneous surface and DOT measurements. Additionnaly, the exact position where laser light penetrates the animal is measured, while traditionally, this information is indirectly inferred with less accuracy. This information plays an important role in a tomographic reconstruction algorithm. Our new approach for the calibration of the rotation axis is compared to another technique we previously developed, where a checkerboard pattern is tracked instead of a ball. We present measurements of a reference shape and a small animal taken by our system.