Sensing or counting clear objects using a standard photoelectric sensor can be difficult. That’s because standard photoelectric sensors are not sensitive enough to detect the small attenuations in light that clear objects cause. To accurately sense glass or plastic bottles, clear packaging, or even transparent films, Pepperl+Fuchs offers special wide-beam diffuse sensors and also advanced retroreflective models, designed specifically for sensing clear objects.
Wide-beam diffuse models, also known as divergent, are available in our popular ML100-8-W Series, along with the small, self-contained 4 mm smooth KT9 and 5 mm threaded KT11 Series. The special wide-beam pattern of divergent models spreads out over the clear object or material rather than burning through. These models are particularly well suited for sensing media cases, clear or semitransparent webs, and even clear or colored shrink-wraps.
More advanced models, like the 18 mm threaded GLV18 Series and the rectangular, subminiature ML6 and compact MLV12 Series, use a reflector and are taught the amount of light returned to the sensor without a target present. A special low-hysteresis circuit in these series can detect even small changes in the amount of returned light that the presence of clear objects cause. Clear glass or PTE bottles, along with clear shrink-wraps and semitransparent trays or cartons are applications that can be solved using these retroreflective models for clear objects.
If you're interested in learning more about this topic, check out my article "Using Sensors to See Clear Objects," as published in the February issue of Design World magazine.