New Dimensions For 3-D Measurements

Three Questions: Need to acquire 4 million data points per square meter in less than a minute? Want to collect surface data from automotive clay models or measure aircraft assembly surfaces? Required to exchange the data with CAD or analysis software? Those are just some of the capabilities of a precision 3-D, non-contact surface measurement system, the AFI 4000, now undergoing beta testing at Toyota Tsusho, Northrop Grumman Corp. and General Electric Co. Dimensional Photonics Inc. (DPI), Southborough, Mass., is the provider. The core technology of the measurement system is accordion fringe interferometry (AFI), a technology that emerged from the Lincoln Laboratory of the Massachusetts Institute of Technology (MIT), Cambridge. Lyle Shirley, now DPI's CEO and president, led the development team at MIT. AFI employs laser light from two point sources to illuminate an object with an interference fringe pattern. A CCD camera records the curvature of the fringes from a viewpoint offset from the projector by about 30 degrees. The degree of apparent curvature coupled with the known angle between the camera and laser source enables the AFI system's software to digitize the surface being measured. AFI's benefits are quantified in factors of 10 by Scott Ackerson, vice president of sales and marketing. "In the automotive sector, surface measurement of dies and parts take one-tenth the time. In aerospace the advantage is a field of view that is 10 times bigger. In power generation the non-contact AFI solution can inspect turbine blades at one-tenth the cost of conventional methods using contact gages." Ackerson says no surface preparation is typically required for AFI applications. "That contrasts with the sprays, special lighting, photogammetry and powders common to conventional structured light methods." Portability also contributes to easy deployment throughout a manufacturing plant. Exclusive of mounting structures, the hardware weighs approximately 30 pounds, adds Ackerson. DPI's initial focus is on industrial applications, primarily automotive and aerospace, but Ackerson foresees broader potential for AFI technology. In health care, he says AFI can enable faster and more accurate design of crowns, dentures, prosthetics and orthopedic aids.