A Single-Pixel Touchless Laser Tracker Probe

Publication Details

Abstract

In this article we will describe our development of a laser tracker probe, the Pixel Probe, that does not require physically contacting the object one is measuring and which has 3D spatial resolution of about 25 ?m (in X,Y,Z) in the current configuration. This touchless laser tracker probe uses three machine vision cameras to discretize a scene down to the spatial resolution of a pixel. A single pixel from each camera field of view is linked to a laser tracker through a calibration process. The three pixels define a point in space that is used as a virtual touch probe, where one places these pixels on an object by means of viewing the camera images. This allows one to measure with a laser tracker the location of small features (tens of microns) on an object without needing physical contact. Given that the design of this system is easily scalable to higher-resolution cameras and lenses, it is envisioned that this system could provide better than the current 25-?m resolution. The Pixel Probe excels at measuring objects that may prove difficult for existing laser tracker probes, such as those with sharp edges and corners, and those with amorphous, soft, and intangible features. In addition, one can register to the laser tracker features that appear in the images, and/or geometries that are derived using machine vision edge- and feature-recognition algorithms. With the Pixel Probe it is also envisioned that other physical quantities based on optical imaging, such as thermal infrared data, and spectral and polarimetric data, can be linked to a laser tracker. Following, we will present the concept, design, function, calibration, and operation of this system, as well as measurements using this system.