Optical sensors from Festo

Optical sensors are used in industry, more precisely in factory automation, to detect objects and their characteristics using light as a medium. They are triggered, for example, when the light is interrupted or the intensity of the light has changed. They operate according to certain basic principles: diffuse sensors (with and without background suppression), retro-reflective sensors, colour sensors, distance sensors and fork light barriers.

Fibre-optic unit SOE4

The SOE4 is one of our high-precision fibre-optic units. It enables switching frequencies of up to 8000 Hz, ranges of up to 2000 mm and is available with LED display as well as switching and analogue output. Thanks to the different mounting options (H-rail mounting or with through-hole), our fibre-optic unit SOE4 is easy to fit wherever it is needed.

Colour sensor SOEC-RT-Q50-PS-S-7L

Colour sensors have a transmitter that emits a light beam, which is reflected back by the detected object and then evaluated by the receiver. Evaluation is possible for the colours red, green and blue. The Festo colour sensor SOEC-RT-Q50-PS-S-7L has a range of 12 mm ... 32 mm and can be used in ambient temperatures of -10 °C ... 55 °C.

Optoelectronic sensors SOOD and SOOE

The SOOD and SOOE are sensors that operate optoelectronically. This means, for instance with diffuse sensors, that the transmitted light beam is reflected onto the receiver by the object. The intensity of the reflected light is evaluated and the switching distance can be adjusted by changing the sensitivity of the receiver. With the SOOE, this is done via IO-Link®, potentiometer or teach-in. This type of optical sensors belong to the group of diffuse sensors. They are a cost-effective solution and can be very quick to install. Other basic principles are diffuse sensors with background suppression, retro-reflective sensors, through-beam sensors and distance sensors.

Optoelectronic sensors SOEG-E/S and SOEG-RS/RT

The optoelectronic sensors of the SOEG series are particularly well-suited for applications with long distances. The SOEG-RS/RT has the functions of a retro-reflective sensor and background suppression and is able to detect metallic and non-conductive objects of all sizes. The SOEG-E/S is a through-beam sensor used for ranges of up to 20 m. Characteristic for both optical sensors are the round design and the electrical connection via an open cable end or a plug.

Fork light barrier SOOF

The Festo fork light barrier SOOF belongs to the group of through-beam sensors. The advantage of this type of optical sensor is that they are very reliable and efficient and can be installed very quickly. Thanks to its sturdy housing, the SOOF has an extremely high shock and vibration resistance. The SOOF is available as a polymer or metal variant, depending on which material is more suitable for your application. The fork light barrier SOOF has a 3-pin plug connection and practical LED indicators. The SOOF-M (metallic) has IO-Link® and different operating modes for added flexibility.

In focus: Festo sensors

Increased cycle times, better process control, shorter downtimes: these days system and machine management that ensures the optimal use of resources is a critical factor in the economic success of a company. Sensor technology, too, is an indispensable part of this success in the world of automation. The purpose of an optical sensor is to measure a physical quantity of light and, depending on the type of sensor, then translates it into a form that is readable by an integrated measuring device.

High quality for smooth processes

Optimum performance and maximum reliability: our comprehensive portfolio of sensors combines these important core qualities and ensures smooth and efficient production sequences in different medical applications for example.

The full range

From the position sensor SMAT to pressure sensing with the pressure sensor SPAN and flow sensing with the flow sensor SFAH, our product portfolio covers the full range of classic sensor tasks for pneumatics. In addition, Festo offers sensors such as the sensor that have been developed for precise and reliable contact sensing and special tasks. The new electronic proximity switch SDBT-MSX is the first proximity sensor with automatic switching point adjustment.

Optical sensors

Thanks to their optical measuring method, the sensor series covers a wide range of different functions, from detecting color and miniature components through to laser distance sensing.

• Diffused sensors detect objects when the light beam, emitted towards the target, is reflected back to the sensor by the target. What makes diffused sensors a great automation option is that they are more compact than typical units, as all components are in a single housing.

• Optoelectronic sensors detect objects with light of a part of the spectrum to trigger function to control, to switch or to regulate. Electrical impulses are converted into light impulses by the transmitter of the optoelectronic sensor and back into a electrical signal by the receiver. The amplifier circuit with downstream comparator processes and compares the signal with a default treshold. The switching function of the output amplifier is triggered depending on the interruption of the beam path. Exact positioning and very large sensing ranges can be achieved with optoelectronic sensors, independent from the material of the objects to detect.

What are electro-optical sensors?

Electro-optical sensors are electronic detectors that convert light, or a change in light, into an electronic signal. These sensors are able to detect electromagnetic radiation from the infrared up to the ultraviolet wavelengths. They are used in many industrial and consumer applications. Most common types:

• Lamps that turn on automatically in response to darkness

• Position sensors that activate, have high sensitivity, when an object interrupts a light beam

• Flash detection, to synchronize one photographic flash to another

• Photoelectric sensor that detects the distance, absence, or presence of an object.

• We see ambient light sensors on our mobile handsets.

Function of optical sensor

An optical sensor converts light rays into digital signal. It measures the physical quantity of light and then translates it into a form that is readable by an instrument. An optical sensor is generally part of a larger system that integrates a source of light, a measuring device and the optical sensor. This is often connected to an electrical trigger. The trigger reacts to a change in the signal within the light sensor. An optical sensor can measure the changes from one or several light beams. When a change occurs, the light sensor operates as a photoelectric trigger and therefore either increases or decreases the electrical output.

There are many different types of optical sensors suitable:

• Photoconductive devices convert a change of incident light into a change of resistance.

• Photovoltaics, commonly known as solar cells, convert an amount of incident light into an output voltage.

• Photodiodes convert an amount of incident light into an output current.

• Phototransistors are a type of bipolar transistor where the base-collector junction is exposed to light. This results in the same behavior of a photodiode, but with an internal gain.

• Optical Switches are usually used in optical fibers, where the electro-optic effect is used to switch one circuit to another. These switches can be implemented with, for example, microelectromechanical systems or piezoelectric systems.

Common applications

Electro-optical sensors are used whenever light needs to be converted to energy. Because of this, electro-optical sensors can be seen almost anywhere. Common applications are smartphones where sensors are used to adjust screen brightness, and smartwatches in which sensors are used to measure the wearer's heartbeat.

Optical sensors can be found in the energy field to monitor structures that generate, produce, distribute, and convert electrical power. The distributed and nonconductive nature of optical fibres makes optical sensors perfect for oil and gas applications, including pipeline monitoring. They can also be found in wind turbine blade monitoring, offshore platform monitoring, power line monitoring and downhole monitoring. Other applications include the civil and transportation fields such as bridge, airport landing strip, dam, railway, airplane, wing, fuel tank and ship hull monitoring.

Among other applications, light sensors can be found in thermal methods which vary the refraction index in one leg of an interferometer in order to switch the signal, MEMS approaches involving arrays of micromirrors that can deflect an optical signal to the appropriate receiver, piezoelectric beam steering liquid crystals which rotate polarized light depending on the applied electric field and acousto-optic methods which change the refraction index as a result of strain induced by an acoustic field to deflect light.

Another important application of optical sensor is to measure the concentration of different compounds by both visible and infrared spectroscopy.