Camera-based 10KHz distance gage

This paper describes preliminary development of a high-speed distance gage for manufacturing process control. The objective of the system was to measure and record the distance from a tool/processing tip to the processed surface at a frequency of 10 Kilohertz with minimal sensitivity of the device to tilt or curvature of the processed surface. This speed is not achievable by use of a standard camera system or by typical position sensitive detectors (PSDs) due to data processing and optical limitations. The proposed solution comprises a linescan camera system and a laser light source positioned diagonally and about the nominal area of interest. In this setup, the line segment, which defines the range of locations of the laser spot, is imaged onto the linescan sensor. The location of the image of the spot is proportional to the location of the spot on the target object. The height relative to a reference tool position is then calculated geometrically. This setup enables flexible analysis of spot location where a multi-layered partly transparent surface is inspected, allows removal of stray light reflections and handles different types of surface finish. A real-time image analysis is enabled through the use of embedded technology.