Clear Object Detection

Clear Object Detection

Clear Object Detection

Clear object detection applications can be found on the bottling applications in many manufacturing industries such as pharma, cosmetic and food & beverage. They are present on filling and labelling machinery where there is a need to detect the transparent materials of containers that could be vials, flask, bottles or jars which have been filled with either liquids or solid products.

The containers could be made of many different materials with a large variety of formats and colors and, in the case of shiny features, the transparency can be very high compromising a stable detection of the object.

This great and huge variety of containers can be a challenging detection issue since the reflection and filtering of the light beam of a photoelectric sensor can be diverted or totally filtered by the material’s color and features. The materials of the containers can be glossy or shiny with different colors, from dark black up to very bright surfaces. This large variety can be a problem for stable detection of these objects, and they need to be detected with no contact techniques, for example using optoelectronic sensors which can detect these objects without touching them. Optic sensors are a good solution, but they need to be designed with several reliable technical features to be stable and adaptable to the huge array of materials and surfaces.




The optoelectronic sensors for these applications can have different mechanical formats and optical functions. The most used are the tubular M18, in compact, miniature and subminiature versions. The machines for these applications are becoming more and more compact and the detection distances are decreasing meaning the objects to detect are not very far from the sensor.

The technology is becoming less expensive, allowing large-scale integration for optoelectronic sensors, and since the machinery is growing ever more compact, the solutions are orientated to miniature sensors. We also see an interesting increase in the subminiature format.

The clear object detection is performed using several optical functions like fork sensor with projector and receiver method, projector and receiver barrier sensors, retro reflex polarized sensor which is an optical barrier with reflector. These are the most used in terms of price and easy installation, with a robust detection performance, but in case of projector/receiver it needs two sensors and a sensor plus a reflector for the retro reflex polarized function.

If better performances are required, the most used product for these applications is the background suppressor optical function for shiny objects. In this case the detection distance can be regulated by a trimmer or a push button, detecting the object but not the background. This optical function is a little more expensive, but needs only one sensor to be mounted without other devices like another sensor or a reflector on the opposite side. The detection distances are not at the same level of retro reflex or projector and receiver, but the solution is very compact. An important characteristic is the color independence or black and white shift, that is an indicator of quality for color or type surface independence.

When very clear objects must be detected, the optical function more frequently used is the specific retro reflex polarized barrier with reflector. This optical function is composed by a sensor and a reflector on the opposite side in front of the sensor. When the transparent object passes through the light beam, the reflected light will slightly decrease, and since the sensitivity of the optoelectronic sensor is very high the object will be detected. This kind of feature is not easy to implement, since a very high sensitivity leads to issues on stable detection, but a good sensor designed for transparent objects can easily avoid this problem.

Another important factor for this kind of application is the emission light type. Usually the request on the color is for red emission, which is visible to the human eye, so that the customer can see the sensor spot and aim in the best way for the target surface.

The light beam can be generated by LED or laser emission, depending on the specification of the customer application. The LED emission is mostly used in basic applications with good detection performance and good price, but without special request and performance on detection precision and speed. When speed and precision are required, the laser emission is the main solution. These characteristics are often requested by bottling and pharma machineries, where the production level is very high together with the need for speed and precision in positioning.

Clear object detection is also a highly used technology in packaging and intralogistics applications where the stable detection of transparent film is important. In the packaging application the main purpose is to detect the presence of film even if it is very thin and transparent. In intralogistics application the main purpose is to detect in a stable way the objects passing through the conveyor wrapped by shiny or very reflective films.



The precise sensitivity regulation is very important to reach good stability for clear applications to cover all the different type of objects that could be detected, also with very particular geometrical shapes and material reflections.

To simplify this application, a smart sensor can be used to set the different parameters to fulfil all the different glass, films or materials to detect through fieldbus, Ethernet communication, or IO-Link. Today the maximum in terms of specification is a smart vision sensor that can use the vison technology to detect easily and reliably a huge range of format and material with any kind of surface. The benefit is being independent by format, color and surface type with the same set up easiness of a standard optical sensor, decreasing the total cost of ownership (TCO) and having a great adaptability to any kind of application. And without the need of skilled people to set up camera, vision sensor or smart camera. The graphic user interface is made very simple thanks to the web server technology. The sensor can also be set up by simply pressing a push button three times on the vision smart sensor user interface. In this way, any kind of clear inspection is accomplished with a very affordable price, very low starting effort and a very fast learning curve for the technology.

The IO-Link technology can be a great advantage for optoelectronic sensors to adapt the machinery automatically “on the fly” and setting the sensors with different menus for different type of objects to detect in production.

Connecting the sensor to an IO-Link Master unit, it is possible to interface several sensors through a fieldbus communicating IO status and uploading and downloading parameters with a fast, easy and standard simple connectivity. In this way, it is possible to avoid many connections through the machinery and saving cost for PLC unit. The OPC-UA technology on board of the master unit allows the sensors to communicate production data through the cloud as much as parametrizations and setting from HMI or SCADA system to set automatically the customer production. With IO-Link technology is also possible to minimize stop production on machinery with predictive maintenance, extended diagnosis, and direct product substitution uploading and downloading parametrizations immediately.

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