Optoelectronic sensor

Today's factories, are equipped with optical sensors that can detect objects and control details such as colour or contrast during production. Many such solutions are available on the market and are also offered by Balluff. What are their characteristics and applications? We will try to answer this question in the following article.

Multidimensional functionality

The primary function of optical sensors is to detect the presence of objects - they can recognise their shape, colour, and distance or thickness. That's not all however, as optical sensors are widely used in industrial automation, where we can take full advantage of their potential. A good example of this is the pharmaceutical industry and batch control processes for drug packaging. In this case, an extremely useful feature is the teach - in function, which allows easy and quick parameterisation of the sensor based on the characteristic of the detected component of interest, such as its presence at a given distance. The sensors will also accurately detect the colour of interest, its hue, differences in contrast or luminescent elements. Thanks to the team, it is possible to instantly isolate defective pieces from the production process.

Optoelectronic sensors are very precise and compared to inductive proximity sensors, have a greater detection range. Additionally, with sensors equipped with an IO-link interface, we can remotely parameterise the measurement window, set the switching threshold and have full access to process data. An additional advantage is the preventive maintenance functions. In practice, this means that the sensor informs us, for example, about dirty lens, working position (tilt), vibration, hours worked, or signal quality. For those looking for pragmatic benefits, miniature sensors are available that can be mounted even in very narrow spaces.

Above-standard applications

If the specifics of the process (e.g., product unification and standardisation) require it, sensors with advanced capabilities that have broader applications in addition to their standard functions are also available. A good example of such a solution is multifunction sensors. This is one sensor that can work as 4 sensors with different operating principles. i.e. reflective with background suppression, reflective, retroreflective or barrier. Due to the fact that such a sensor can work in several modes, we do not need to invest in 4 separate devices, and we can parameterise it freely, for example, in the first application it will detect containers passing on the line, and in the next application it will check if there is a lid on the component. What's more, in addition to the standard function, i.e. detecting objects, we can program simple logic functions into the sensor, allowing, for example, to control the speed of rotating components, or counting the detected components. Thanks to this, the sensor will issue a signal at the output only after counting the number of them we assumed. Sensors equipped with IO-Link interface are characterized by simplified parameterisation. After replacing a sensor, IO-link allows remote uploading of parameters. As a result, the user does not have to enter the parameters manually from scratch, everything is done automatically on a "plug and play" basis. We replace the sensor with a new one, and its configuration remains unchanged. Such a solution perfectly reduces the time spent on the entire replacement process. For the detection processes of glass items, such as jars or bottles, advanced reflection sensors with a polarisation filter for detecting transparent surfaces are also an interesting proposition.

An additional advantage of reflective sensors is the background suppression function, useful, for example, in detecting the presence of a plastic pin in a component of the same colour and material. The sensor is able to detect the component even if there is a background immediately behind it that is brighter than the detectable object. The sensor automatically "cuts off" the background and detects only what is directly in front of it. The latest series of sensors allows detection with background elimination up to 5m range.

Reflective sensors with CCD array

In terms of advanced technology, it is worth mentioning the series of reflection sensors with CCD matrix, with the additional ability to analyse and compensate for the background and suppress the impact of changing external lighting. Thanks to these functionalities, the sensor accurately detects even very shiny and reflective parts under changing lighting. Here, a good example is machine tools, where parts covered with coolant or lubricants strongly reflect light, as well as equipment working in halls where, depending on the time of day or year, the lighting changes.

Sensors for "special tasks"

But it doesn't stop there when it comes to advanced sensor capabilities and applications. Where we have very limited installation space, miniature optical sensors with just a 2mm head will be perfect. They look like fibre-optic sensors, but are equipped with an electrical cable and we can mount them even in the narrowest space. If, on the other hand, we need precise colour sensors, then the correct technology will be True-Colour sensors, which allow us to detect colours that differ by mere nuances - such as hue. Such models will find their application, for example, in the automotive industry for distinguishing the colour of components such as car door handles or various types of caps.

Optoelectronic sensors offer a whole range of possibilities in addition to their standard functions. It is enough only to specify the needs that the sensor is to meet and the way it is to be used, and we will certainly find a solution that seems to be "tailor-made" for our needs.