Rethinking the optical sensor

17 July 2018

In response to feedback from industry customers SICK has recently upgraded its optical sensor technology to meet industry needs today and in the future.

Following a consultation with machine designers and photoelectric sensor users in food and beverage processing, bottling and packaging operations SICK identified that, in addition to the expected features, such as being Industry 4.0 read and being robust and reliable, customers wanted more simple product selection, quick configuration and ease of use.

SICK set out to meet these needs by simplifying its optical sensor range. The result is the SICK W16 and W26 smart sensors with ‘BluePilot’ alignment. The new proximity, reflex and through-beam laser sensors will be manufactured at a purpose-built, fully-automated factory in southern Germany.

BluePilot alignment
The most significant development is SICK’s BluePilot assistant. Sensor applications that use a reflector, or a transmitter and receiver, need careful adjustment to ensure optimal alignment – and this can be tricky, especially over longer distances. If the light spot is not in the correct position it could lead to production failures or stoppages.

Traditionally, a machine designer or end-user could have a difficult choice between using a time-consuming potentiometer, with many fine adjustments before achieving the desired level of precision, or else compromising on manual adjustment in favour of a teach-in button, where you must trust the sensor to do the thinking for you.

The BluePilot assistant overcomes this issue by using a line of five LEDs mounted on the top of the sensor for quick, easy and accurate alignment of the light spot, even over long distances. The blue LEDs also provide an ongoing visual status indication to verify that the sensor is still in alignment. This can minimise set-up and maintenance times.

The company also set out to optimise its optical technologies. Its Twin-Eye technology, for example, is suited to detection of reflective materials such as films, foils, contrast-rich or uneven surfaces when they need to be detected from above. False signals lead to production failures that cause machine downtime while an operation is reset, or lead to unnecessary product wastage. In a standard sensor, films, foiled designs, print on glossy foils, high-gloss UV varnish, high-contrast prints, fluorescent or reflective inks could all lead to deflections, which mean the light spot is not reflected consistently to the receiver.

The second receiving channel of the Twin-Eye design overcomes this problem. Even when the laser light spot is deflected by a shiny or wavy surface, the light is reflected back onto both receivers, causing the sensor to switch on and detect the object. Or, if the reflected light is still detected by at least one of the two receivers, the switching signal is maintained and operation continues reliably.

Optical filter technology
For semi-transparent and transparent objects, such as bottles and plastic trays the ClearSens optical filter technology can offer a solution. Intuitive mode selection on the device makes set up easy, and according to the characteristics of the object to be detected, the on-board potentiometer enables maximum detection certainty to be combined with maximum accuracy.

ClearSens provides a solution for object detection where the laser light may be refracted, magnified or diffused, depending on the packaging or the properties of the contents, or even scattered by inclusions within a transparent product such as a gel.

Detection of clear glass bottles filled with water pose the ultimate challenge. Due to an optical effect, the detection can be interrupted as soon as the light beam reaches the centre of the glass bottle. ClearSens technology in the new WLG16 photoelectric sensor overcomes this. The effect is compensated for through the intelligent evaluation of light intensity and scatter, in combination with switch-on and switch-off thresholds that have been specifically designed for use in detecting bottles and trays.

Ambient light issues
The ambient lighting of a factory, flashes of light or reflections from surrounding machinery, can all affect an inferior sensor’s performance and lead to false or missed signals. However, SICK’s new OptoFilter technology, makes the W16 and W26 sensors immune to interference from unwanted light sources and reflections, LED lighting which is increasingly common in factories or hi-viz safety workwear.

The new streamlined portfolio also incorporates IO-link two-way communication as standard on all devices. A Bluetooth wireless option is also available to enable easy monitoring and commissioning from smart phones or tablets.

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