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High-Speed Structured Light Sensors for Inline Inspection Applications

Posted By Terry Arden on February 14, 2017

Up until now, laser-based scanning has been the predominant technology for inline 3D inspection. However as 3D inspection requirements in the factory continue to evolve, it is important for sensor manufacturers to continue to develop new and improved solutions.

Laser Line Profilers

Laser line profilers behave like a line scan camera. The part to scan has to travel under the line profiler’s laser (which requires a motion transport system) in order to build a complete 3D point cloud. An encoder is used to stamp each profile with an accurate position so software can stitch all  the profiles together to generate a full 3D model.

Laser Line Profile Sensor

An Alternative to Laser Scanning: Structured Light

In comparison, structured light (SL) scanners take a snapshot of a part that is stationary. This eliminates the need for an expensive motion system and associated vibration that affects measurement repeatability.

Structured Light Snapshot Sensor

Known Limitations of Standard SL Sensors

SL scanners are only used in offline or at-line applications because of their slow cycle times (several seconds required per part scan). In addition, SL sensors are not IP67 rated, which means the optics are not protected from dust and moisture; fans are needed for cooling; and LED projector lifetimes are limited to just 1-2 years of continuous use. All of these issues combined prevent the use of SL sensors for inline operations.

LMI’s Solution

To advance SL technology, LMI has invested heavily in onboard sensor hardware acceleration and industrial LED projector design to deliver fast cycle times and much longer projector lifetimes (eg., 10 years) necessary for inline use.

Hardware acceleration takes place on a Field-Programmable Gate Array (FPGA) in the sensor, which effectively “crunches” stereo camera data into a highly compressed dataset suitable for downstream generation of 3D point clouds in the fastest possible cycle times.

This innovation takes the form of a new generation of Gocator 3D smart snapshot sensor that leverages on-board hardware acceleration to achieve scan rates up to 0.5 Hz for full resolution, full volume scans (no windowing).

Furthermore, with the Gocator Accelerator (GoX), the user can increase scan speeds by 4x (e.g., 2-4 Hz). This breakthrough speed allows SL technology to move into inline applications.

Industrial LED Projection

Standard LED projectors use plastic optics. Plastic optics deteriorate quickly with blue/UV light. In contrast, LMI’s projector is made of glass. LMI has also efficiently managed heat dissipation in the projector design, preventing thermal wear and tear and significantly increasing lifetime. The result is an ultra-bright projector that is capable of lasting up to 10 years of continuous use.

Learn More About Structured Light for Inline Inspection

If you’re interested in learning more about structured light as an inline 3D inspection solution, check out this article on the upcoming Gocator 3210 using hardware acceleration for use in automotive applications.

Posted by: TERRY ARDEN, CEO at LMI Technologies 
Terry has been working in high tech and machine vision for more than 25 years. As LMI’s CEO, Terry drives the overall vision and business development to deliver the benefits of 3D smart sensor technology.
February 14, 2017