Camera-based distance gage can replace position-sensitive detectors

MAY 13, 2009--Researchers have developed a vision solution with embedded computing for distance measurement that eliminates errors associated with surface tilt and surface shape in manufacturing process control applications. The standoff camera system determines the distance between the processing tip and the surface at the point of process.

In surface treatments such as depositions, fine machining, and dispensing of a cover or protective layers, online real-time height measurement may be required to control process quality. In manufacturing process control, position-sensitive detectors (PSDs) are commonly used for distance measurement. However, PSD technology has several drawbacks, such as performance degradation in the presence of multiple reflections, stray light, variations in the beam shape and intensity distribution, and surface tilt.

Gil Abramovich and Kevin Harding at GE Global Research (Niskayuna, NY, USA) developed a high-speed, camera-based distance gage that eliminates some of the challenges associated with PSDs. Analysis of geometrical and illumination efficiency constraints suggested that imaging the reflection of a laser spot is the best method, so their system includes a linescan camera with resolution of 20 microns or better. A significant part of the prototype is an embedded image acquisition and processing unit that uses a FPGA.

Further work is required to create a standalone prototype and to finalize the design and assembly of the FPGA solution. For more information, go to: http://spie.org/x34361.xml?ArticleID=x34361

-- Posted by Conard Holton, Vision Systems Design, www.vision-systems.com