Pepperl+Fuchs Blog

Using Photoelectric Sensors with Background Suppression

Posted by Kevin Catalfamo on Thu, Apr 04, 2013

Applications for the printing industry

Photoelectric sensors for the printing industryPhotoelectric sensing applications in the printing industry are just as varied as those found on the industrial floor. There are many types of printing machines—digital printers, web-fed and sheet-fed printers—and these printers use a wide variety of media that range from very thin foils and films to thick cardboard, plastics, reflective or glossy printed material, adhesive films, packaging material, even 3D holograms.

So, photoelectric sensors that are used in these printing machines have to be able to consistently sense the target at the same distance, regardless of media, and still be able to ignore any background or color variation; they require photoelectric sensors with background suppression. These sensors offer precise and reliable sensing without needing a reflector, or frequently re-adjusting the sensitivity.

In addition to color variations, paper dust can be a major problem when it comes to photoelectric sensor reliability. Too much dust can cover the sensor lens and reduce the ability to operate properly. Even paper itself can be very harmful to the sensor lens. If paper comes in contact with the lens, scratching occurs, and the sensor lens becomes like a pair of scratched eyeglasses. The sensor‘s ability to see the target is diminished.

Pepperl+Fuchs has a wide range of photoelectric background suppression sensors designed specifically for the printing industry. There are abundant sizes, detection ranges, outputs, and connection types with a visible red or infrared light source. Unlike most manufacturers, we use a glass lens, not plastic, that has an antistatic coating that inhibits dust build up.  Some sensors are available with an innovative lens contamination system that monitors the sensor’s optical lens. Dust or fibers from the various media are detected and a secondary sensor output signals that the lens should be cleaned. This avoids large amounts of dust from accumulating on the sensor's face, preventing the sensor from detecting reliably.

Additional features and advantages:

  • Excellent background suppression allows the sensor to detect the target, but ignore anything beyond the target including shiny or moving parts
  • Good black to white ratio
  • Best detection characteristics even in the presence of shiny or glossy materials
  • Small, sharp light spot
  • Multiple mounting capabilities
  • Dust proof
  • Shock resistant
  • Insensitivity to various colors, so that you can consistently detect targets at the same distance regardless of color
  • Glass lens reduces scratching
  • Coated lens to repel paper dust
  • 4-in-1 (push-pull) output circuit design allows many different output options from one sensor
  • Precise triggering of object edges

As a company, Pepperl+Fuchs has a long history of dealing with the challenges of the paper industry. We know how to make sensors that withstand the rigors of the printing factory floor.  Understanding these difficult issues has led to the design of a wide range of different background suppression sensors (BGS) and unique sensing faces for many printers around the world.

Download: Sensors for the Printing Industry

Topics: Applications, Photoelectric Sensors

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