Guest Editorial: Special Section on Optical Methods for Shape Measurement

Abstract

In industry, there is a need for accurately measuring the 3-D shape of objects to speed up and ensure product development and manufacturing quality. There are a variety of applications of 3-D shape measurement, such as: control for intelligent robots, obstacle detection for vehicle guidance, dimension measurement for die development, stamping panel geometry checking, and accurate stress/ strain and vibration measurement. Moreover, automatic online inspection and recognition issues can be reduced to the 3-D shape measurement of, for example, body panel paint defects and dent inspection. The principles of triangulation, structured light, and interferometry have been in existence for decades. However, it is only with the recent availability of advanced and low cost computers, electro-optical elements, and lasers that such techniques have reached the breakthrough point to be commercialized, and ever increasingly be applied in industry. To make it even more acceptable in industry and to strive to achieve 10 to 10 accuracy, there are still some challenges that need to be addressed, such as: the shading issue, the specular surface headache, accurate data patching from different view directions, geometric parameter determination and calibration, absolute phase measurement, local and global coordinates tracking and transforming, real-time computing, sensor planing, and optimization. This special section is designed to promote research activity and to serve as a forum both for academia and industry. This special section includes a variety of development and application examples such as: optimization of an optical system which results in one part in 20,000 accuracy, new techniques using a diffraction grating or defocus to overcome the shading issue, direct digital wavefront reconstruction combined with wavelength scanning to attack the absolute phase measurement issue, and develop-