High-resolution optoelectronic and photogrammetric three-dimensional surface geometry acquisition and analysis.

摘要

A high-resolution, high-speed, automatic, and non-contact 3-D surface geometry measuring system has been developed. It is based on a photogrammetric and optoelectronic technique that adopts lateral-photoeffect diode detectors sensitive in the near-infrared range. Two cameras in stereo positions are both equipped with the large 2-axis analog detectors. A light beam is focused and scanned onto the surface of an object as a very small light spot. Excitations on detectors generated by the reflected light from the spot create photocurrents that are transformed into 2-D position signals in a very short time. A simple set of calculations is done to photogrammetrically triangulate two sets of 2-D coordinates from the detectors into the 3-D coordinates of the light spot. Because only one small light spot in the scene is illuminated at a time, the stereo-correspondence problem is solved in real time. The detectors are able to collect data at 10 KHz with 4,096 {dollar}times{dollar} 4,096 resolution based on a 12-bit A/D converter. The resolution and precision can be improved up to eight times by oversampling. The system is able to resolve, for example, less than 10 {dollar}mu{dollar}m from 47 cm away with a nominal viewing volume of (22 cm){dollar}sp3{dollar}. Its performance is better than contemporary coordinate measuring, range finding, shape digitizing, and machine vision systems, and is comparable to the best aspects of each existing system. The irregular 3-D data it generates can be regularized so that data processing algorithms designed for image systems may be applied. The system is designed for the acquisitions of general surface geometries, such as fabricated parts, machined surfaces, biological surfaces, and deformed parts. The system will be useful in solving a variety of 3-D surface geometry measuring problems in engineering design, manufacturing, inspection, robot kinematics measurement, and vision.