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Luminescence Sensor Technology

Luminescence sensors detect luminescent markings by shining UV light on an object – regardless of patterns, colors or surface properties. The luminophores contained in the material are activated by the UV light and reflect visible light. If the sensor detects the light that has been previously taught in, it switches the output.

Luminescence

Luminescence refers to a process that takes place due to a chemical reaction through the absorption of radiation energy.

Luminophores

Luminophores are substances that emit light when short-wave light (wavelength range between 420 and 750 nm) is shined on them.

UV Light

UV or ultraviolet light is in the wavelength range up to 380 nm and is not visible to the human eye.

How Luminescence Sensors Work

Luminescence sensors emit UV light with a wavelength of approximately 375 nm, which is not perceptible to the human eye. Now the effect of luminescence becomes apparent: When the emitted UV light hits a fluorescent material, the material is activated and starts to shine.

Luminophores are pigments that are stimulated to glow by UV light. At the same time, the fluorescent substance converts the UV light into long-wave light visible to the human eye (in a wavelength range of 420 to 750 nm). The reflected light is received and processed by luminescence sensors.

It is important here that the activation frequency and emitting frequency match. This reflected light actuates the reflex sensors to send an output signal to a controller.

How Filters Impact the Result

With a filter, specific wavelength ranges are suppressed, meaning that light only reaches the receiver in a certain range. The use of a filter has the advantage that disturbing background luminescences can be suppressed. The luminescence sensor is available in two different versions, which differ in their receiver filter.

Detection of Different Luminescence Colors

The P1PA001 luminescence sensor features a blue-permeable receiver filter. Wavelengths in the range of 420 to 750 nm can be detected with this sensor. One example from practice is the detection of leaflets in the pharmaceutical industry. The white paper in the leaflet contains optical brighteners that light up blue under UV light and are detected by the sensor.

Detection of Markings on Luminescent Objects

The P1PA002 luminescence sensor has a receiver filter for detecting wavelengths in the range from 570 to 750 nm. Due to the restricted receiving range, the sensor reliably detects green, yellow or red marks on luminescent objects and materials. The sensor can be used to detect green to red markings on paper; the blue illuminated paper is not detected.

Luminescent Markings from Two Perspectives

The luminescence sensors detect luminescent marks, regardless of the amount of luminophores they contain. With a small, precise light spot, even the smallest markings in different luminescences can be reliably detected.

Luminescence Sensors for Detecting a Wide Range of Materials

Luminescence sensors can detect luminescent markings on many objects regardless of texture, color or surface finish.

Materials with Natural Luminophores

Natural luminophores, for example, are found in white paper. This lights up blue under UV light and can be detected by the P1PA001 luminescence sensor through its blue-permeable receiver filter.

Materials without Natural Luminophores

Luminophores can be artificially added to almost all materials. As luminophores are not visible to the human eye, they do not impair the appearance of the product.

Color and Contrast Differences

For the luminescence sensors, different colors or contrasts of surfaces have no effect on the detection of luminescent markings.

Strong and Weak Illumination

The reliable detection of luminescent markings using UV light is not influenced by strong or weak ambient lighting.

Possible Uses for Luminescence Sensors

The intelligent luminescence sensors can be used in many industries and sectors.

Presence Check

Luminescence sensors reliably detect the presence of various media, such as glue, oil, ink or lubricant. The sensor also check the presence of leaflets for pharmaceutical products.

Label Monitoring

Luminescence sensors monitor labels on food cans, bottles, pharmaceutical products and other products.

Counterfeit Detection and Quality Control

Application example counterfeit detection quality control

The authenticity of products and materials can be verified with luminescence sensors. The quality of wood is also checked by the detection of knotholes.

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