Advanced Color Sensing

DN Staff

August 26, 2009

3 Min Read
Advanced Color Sensing

A more powerful generation of color sensors is emerging to fill the gap between the limitations of basic color sensors and color vision systems. These new devices offer better detection capabilities, multiple methods for evaluating colors and PC software tools that simplify the setup and fine-tuning of applications.

"Advanced color sensors provide more control for the user, more visibility into the process and more flexibility without the need for external lighting, customized software and the complicated setup often associated with a vision system," says Jeff Allison, product manager, photoelectric sensing for Pepperl+Fuchs. "The trend has been to fill the gap where customers need more than a standard color sensor but less overall capability than a color vision system can offer."

Allison says a key advancement from the customer perspective is better software tools to gain visibility into what is happening inside the color sensor. PC software packages allow the user to use graphical tools to map the colors the sensor is identifying and, by fluctuating the color, see exactly what hues and other attributes are changing when the object is moved. By graphically viewing what is happening, it provides the user more control in how to identify color.

Advanced color sensors learn and evaluate colors much like human vision using an additive approach, looking at each color as a component of high, medium and low frequency colors. Basic color sensors normally evaluate only one frequency band of light and do not account for brightness.

Allison says the advanced sensors also provide the ability to choose the optimal color space for the application. Different types of color spaces define coordinates using different methods, and most color spaces are three-dimensional. As a result, it may make sense to evaluate colors in one color space for one application and a completely different color space, with its own uniquely derived coordinates, for another application.

"When the sensor identifies a color, it assigns a numeric value and coordinates in a 3D color space, says Allison. "Each point in the color space corresponds to a specific color."

Color spaces can be used to identify color attributes for glossy materials, translucent objects and the illumination of an object such as a color LED.

New VCS210 color sensors from Pepperl+Fuchs enable users to program, evaluate, process, and display up to 255 distinct colors. Allison says its 100mus optimal response time is up to 10 times faster than competitive color sensors. In many applications, the added speed improves productivity by reducing instances where the process would otherwise need to slow down, or even stop for an inspection.

"Unlike many RGB and other color sensors, the VCS210 can evaluate colors quite similar to human vision," Allison says. This means that the sensor can look at the true color of the target and not be affected by its glossiness or brightness, resulting in consistent, repeatable checks of a target color."
Advanced color sensors are targeting packaging applications where multiple product types need to be identified and diverted to different packaging lines, as well as automotive applications where molded interior parts, carpeting or upholstery need to be sorted or verified by color. Other applications include sorting, verifying the correct order of wires in connectors (by color), checking fabric and leather colors and controlling the mixing process in paint applications.

A white paper on Advanced Color Sensing is available on the Pepperl+Fuchs website:
(Select "Factory Automation White Papers" and download "Advanced Color Sensing - Shades Above The Rest"

Windows-based software tools provide visibility into the operation of the sensor and how it interprets individual colors.

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