Photosensor isn't fooled by the background

Edited by the Engineeringtalk editorial team Oct 2, 2006

Photoelectric sensor incorporates a dual-receiver optical system that allows it to actively "see" both the target and background areas, while suppressing any background reflections.

Optical sensors are vital in ensuring product quality in automated production lines.

But in many systems, ensuring the accurate recognition of objects is a real challenge - especially where the target object is close to a surface that must be ignored, such as a conveyor.

The new 44B photoelectric sensor from Rockwell Automation, equipped with adjustable background and foreground suppression, provides an effective solution to this common problem.

The Bulletin 44B sensor incorporates a dual-receiver optical system, which - unlike standard diffuse-type sensors - allows it to actively "see" both the target and background areas, while suppressing any background reflections.

The result is more reliable object recognition and fewer false alarms, which can cause unnecessary product rejection or loss of production.

The 44B is available in either background suppression or foreground suppression mode, both using a cost-effective, common optics system designed to reduce false triggers due to background reflections.

Both sense modes will recognise the background condition using a second internal receiver.

The behaviour of the sensor will depend on whether it is operating in background or foreground mode.

In background suppression mode, the Bulletin 44B will change its output state when it "sees" reflected light from the target.

While in foreground suppression mode, it will use the background as a reflector and change its output state when a target blocks this reflector.

The background suppression sense mode is best suited for the detection of light targets against a less reflective background.

For example, in the detection of missing bottle caps: the sensor will "see" the bottle cap by the reflected light from the cap, while ignoring the bottle itself.

Foreground suppression is more effective when detecting a dark or irregularly shaped target against a highly reflective background.

This mode is ideal for the detection of products on a reflective white conveyor belt.

The sensor will "see" the product by the absence of reflected light from the belt.

The Bulletin 44B is designed to be robust enough for most industrial applications: The rugged IP67-rated "square-style" housing provides a high degree of environmental protection, allowing it to be used in water washdown environments.

LEDs give a visual indication of power, output and stability status and electrical connection is via a M12 QD connector, designed to help prevent miswiring.

Versatility is further enhanced by dual NPN and PNP outputs and the 90-degree swivel design allows the 44B to be mounted in a wide variety of positions.

With its unique optical design, dual-mode suppression and fast 1ms response time, the Bulletin 44B provides a highly effective yet versatile optical sensing system, helping to ensure high quality production line output with minimum false triggers.