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Three-dimensional (3-D) measurement is an important capability in the field of machine vision and automated inspection.
 

Noncontact, 3-D surface measurement is used in many ways, including:

• Dimensional inspection

• Quality assurance

• Damage assessment

• Reverse engineering

• Dimensional documentation

• Scale-model verification

• Recording 3-D tests

A unique method for obtaining 3-D surface measurements, dynamic structured light (DSL) 3-D imaging (patent pending) is an optical measurement technique that is an extension of conventional structured light methods and offers many advantages over previous 3-D measurement techniques, such as:

• Lower cost

• Higher accuracy

• Greater depth of field

• Greater stand-off distance

Previous methods of 3-D surface measuring used contact measurement, laser triangulation, or structured light projection to measure a single point or a line at a time. Southwest Research Institute (SwRI) developed an extension of the structured light technique in which a complete array of points are measured by a computer analysis of a rotating optical pattern projected on the surface.

DSL 3-D imaging replaces complex 2-D pattern analysis with independent 1-D analysis problems and removes ambiguity at surface discontinuities.

The projected pattern is moved over the surface in a known way while the pattern of light and dark changes is recorded at desired measurement points with a machine vision camera. The surface elevation at any location can then be determined by analyzing the light and dark changes at each point without considering any other points on the surface.
 

DSL 3-D System Components

The DSL measurement system uses available off-the-shelf machine vision cameras and Pentium computers, providing a distinct cost advantage over most competing technologies. Proprietary image-processing software and computational algorithms compensate for first-order optical distortion and provide high-accuracy measurements by interpolating between generated quadric surfaces.

Availability

DSL 3-D measurement systems can be configured to meet a wide variety of applications, including:

• Precision small parts measurement

• Reverse engineering of large stamped or assembled panels

SwRI has developed design tools to evaluate specific configurations and select suitable combinations of computer, camera, and grating projection, as well as the geometric layout to provide the desired performance.

3-D Measurement Services

SwRI maintains a 3-D measurement facility based on DSL 3-D technology. This facility is available for measuring objects and devices ranging from an overall size of less than 1 inch to 10 feet. Accuracy and resolution can be scaled to meet measurement requirements. Software is available to convert point measurements to surfaces and to convert the data into standard file interchange formats such as DXF, IGS, or STL.

For more information about DSL 3-D imaging capabilities at SwRI or how you can contract with SwRI, please e-mail Ernest Franke, PhD, PE, or call (210) 522-3678.
 

| Manufacturing Systems Department | Automation and Data Systems Division | SwRI Home |

Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

September 06, 2007