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Plug-and-Play Metrology

Photonics Spectra
Aug 2004
The new "snap-together" standards of machine vision promise simplicity and lower costs.

Shane Jennings, The Imaging Source

The field of metrology historically has been saturated with complicated, proprietary solutions. With such specialization, integration of machine vision into an application has been an expensive and often monumental task for the layman. Those who were experts in their field but who had little experience in the “black art” of machine vision often were forced to hire a systems integrator or to dedicate a substantial period of their time to the syntax and nuances of a particular system.

The niche markets have remained relatively stagnant with respect to ease of use, but the consumer markets have been making tremendous leaps forward in their delivery of the power and flexibility afforded by computer technology. As the concept of plug and play rose in popularity in the computer industry, those in the machine vision industry had similar expectations. Simplicity and cost-effectiveness finally have arrived through high-speed communications protocols such as USB and FireWire, which allow a direct interface with a digital camera, eliminating the extra step of a frame grabber coupled with an analog camera.

Although some environments have highly specialized needs, and a universal approach is more likely to have unsuitable limitations, the majority of day-to-day imaging applications are centered around gathering and manipulating data from standard acquisition sources. Many times, tried-and-true workhorse CCDs are overlooked because the interfaces to the data they acquire have unjustifiable learning curves.

Engineers often decide that, if they are going to put effort into learning a system, it should be as diverse in scope as possible. As a result, many consistently choose to implement unnecessarily elaborate solutions for even simple machine vision tasks for the sake of remaining in a familiar development environment. With the integration of the new standards in the metrology industry, the lines are progressively blurring into the potential for a more consistent, cost-effective interface.

The goal is to simplify data acquisition and focus more on processing. With the demand for what amounts to an uncompressed full-resolution Web camera with a tool kit, cost concerns are diminished for both hardware and software because these devices have not only built-in interfaces for most processors being sold today, but also native operating system support. Data collection arrays are easy to create and, because features such as device selection and frame rate can be easily controlled through the software, bandwidth concerns can be overcome with relatively little impact on a project’s budget.

The standards are consistent, so interfacing the devices becomes a nonissue because they are all filtered through a standard feature enumeration protocol. Besides the hardware protocols, the interface to a common driver standard under popular operating systems such as Windows 2000 and XP allows development to focus on ease of use and the diversity of tool kits and their applications, instead of allocating available resources to interface a given camera. Through this centralization, tool kits become stronger and easier to use. For other operating systems, there are standards such as the DCAM protocol.

Cameras_Imaging-Source.jpg
The single cable and the modularity of most digital cameras make them ideal for environments where flexibility is key.

Besides reduced system costs, simplicity is often the driving force behind the migration from one computer generation to the next. Digital cameras, for example, are much simpler to control than analog because they don’t have jumpers or dip switches. They can be used with just one off-the-shelf cable for image transmission and camera control. Today, instead of analog cameras, frame grabbers and proprietary tool kits, the operating system can recognize cameras in the same way it recognizes any new hardware device.

Meet the author

Shane Jennings is sales manager for the US office of The Imaging Source in Charlotte, N.C.; e-mail: shane@us.theimagingsource.com.


GLOSSARY
frame grabber
Image processing peripheral that converts video images from cameras into digital format and transfers these digital images to PCs.
metrology
The science of measurement, particularly of lengths and angles.
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