3-D shape measurement based on an adaptive lighting-pattern projection method

The authors have developed a sensor-combined measurement system to realize a speedy three-dimensional shape measurement at production lines. The system consists of a camera with both area and line sensors, an image input unit with two LUTs, a computer of the workstation type, and a Gray-type lighting-pattern projector with a liquid-crystal mask. The authors discuss high speed image data processing techniques to obtain the space-encoded images of a measurement space and a shape recognition analysis using a gradient histogram on space-encoded stripes of each segmented object image. Although the measurement space encoding of the area sensor image is carried out in a speedy hardware manner, that of the line sensor binary-image consisting of specified subregion images requires a specific technique to copy pertinent stripe codes. without breaking line sensor image resolution, from those of the area sensor space-encoded image. The adaptive lighting-pattern projection method is used for this purpose. Size measurement accuracy, is improved by the present system to seven times higher than that of conventional area sensor measurement