Basics Optical Sensors
Basic Knowledge of Optical Sensors
Colour sensors are detecting object and light colours which have been taught to the sensor in advance (max. 31 colours). To avouch the best possible adaptation to the different inspection tasks, there exists a large range of different sensor types. The colour sensors are working according to the 3 colour range principle. This means that the received light is separated in red, green and blue for further processing. As light source during inspection, there are used clocked white light LEDs or UV-LEDs for luminescence sensors. Depending on the demands of the application, there can be used sensors with different light spot diameters, with focused light (FCL) or diffuse light (DIL). Because of the modulation of the light source, it is reached a high independency of the ambient light (POL). Colour sensors with polarization filter eliminate the gloss of objects and can therefore detect the colour of high glossy objects. Contrary to this, colour sensors with special gloss recognition (GD types) take a gloss control additionally to the colour control at the object. By doing so, it is possible to distinguish objects with same colour but different gloss characteristics. Multiple colour sensors can be supplied as true-colour-version. With an illumination that is adapted to daylight (D65) it is possible to detect colours that are similar to the human colour perception.
To allow colour detection within narrow rooms we supply a huge range of fiber optics (LWL). By the use of special optics, it is possible to check objects with a distance of 10 to 800 mm. With switching frequencies up to 30kHz, it is no problem to detect fast processes.
The colour sensors are parameterised via Windows® user interface that shows the detection results numerically as well as graphically.
Operation area: |
|
Gloss sensors are sending light in a accurately defined angle on the surface which should be detected. Two specially adjusted receivers are detecting the diffuse reflected as well as the mirrored light. For matt surfaces, the diffuse percentage is higher and for glossy surfaces, the mirrored one. The proportion of both receiving signals is a measure for the degree of gloss.
Operation area: |
|
Contrast sensors are generally energetic light sensors. Because of their special adapted characteristics regarding their light colour, light spot, switching frequency and adjustment of sensibility, they are especially suitable for the detection of contrast differences.
Operation area: |
|
L.A.S.E.R. = Light Amplification by Stimulated Emission of Radiation
Laser light runs almost parallel in one direction. Through focusing of the radiation, lasers achieve a higher efficiency than normal light sources. Because of the small divergency, lasers can transmit energy over large distances. The oscillations in a laser beam are running almost in phase (coherent) and show a big coherence length. This means that the oscillations have no phase shifts over huge distances. Because of the polarising optical components in the resonator, the whole radiation of a laser runs in one polarising level. The laser beam contains only light of one wavelength.
Operation area: |
|
Analogue laser light barriers are working with parallel directed laser light with homogeneous light distribution and circular or rectangular cross section. To use it completely, you need to have an indicator unit. The output supplies an analogue signal (0...10 V or 4...20mA) proportionally to the disconnection of the receiver.
Operation area: |
|
Digital laser light barriers are working with visible, parallel directed laser light. Through the use of round or rectangular screens, the light is dispersed homogeneously and smallest parts are detected over large sender-receiver distances. The integrated barrier tracking of some types results in a compensation of pollutions.
Operation area: |
|
Laser fork light barriers with laser light that is directed parallel with homogeneous light distribution with circular or rectangular cross section detect smallest objects. The sensibility is adjustable by the help of a potentiometer.
Operation area: |
|
The devices of the L-LAS series are divided into 3 different operating modes: Triangulation sensor, transmitted light sensor, reflected light sensor. The physical resolution has up to 1024 pixels. An analogue output (voltage or current output) informs about distance, position or size of an object. The digital output switches at higher or lower deviation of the adjustable threshold value. A serial interface (RS232) allows the communication via PC (or a PLC + RS2332-modul).
Operation area: |
|
With an outer diameter starting from 3 mm or a M4 thread, these laser light barriers are belong to the smallest types worldwide. Because of its compact structural shape, the M-LAS series is used for applications that do not offer much space and that demand a small light spot is (parallel or focused). The sensor is belong to laser class 1 and guarantee a safely use without special protection or precaution.
There are multiple control electronics available:
RS232 version parameterisable with Windows® / Analog version with 4...20mA output / Digital version with barrier tracking
Operation area: |
|
Reflection laser light barriers of type R-LAS-LR are working according to the principle of autocollimation. An integrated polarising filter offers protection against false tripping through reflecting objects. The laser power adapts it-self to the corresponding reflector and the reflector distance. The sensors are parameterisable via Windows® with software LR-scope. Laser reflex sensors of type R-LAS-LT are working according to the principle of triangulation with background suppression. The measured object is detected independently of surface characteristics, colour and background. Standardised evaluation and power readjustment guarantee a high dynamic range. The sensors are parameterisable via Windows® with software RT-scope or LT-scope.
Operation area: |
|
SI-JET laser spray jet monitoring systems are controlling the density, symmetry and aperture angle of a spray jet with the help of three laser or LED beams. The software allows a parameterisation of the system. A pollution of the optics can be avoided through flushing-air.
Operation area: |
|
Distance sensors with light running measurements are suitable for applications where a constant power is demanded over the whole measuring range. The maximum measuring and detection mistake depends mainly on the application as well as the following functions. Here, the linearity is very important. The linearity indicates the maximal deviation of the analog output to optimal value which is proportional to the distance and is specified in percent of full scale. With the laser distance sensors of series KLD, it is possible to have precise measurements over large distances. The principle of function of the sensors is based on the reflection characteristics of natural surfaces. With the help of special reflectors, distances of up to 100 m can be realised. Beside two separately adjustable switching outputs, you can have analogue or alarm outputs as well as serial interfaces for several versions.
Operation area: |
|
Light barriers will be splitted by function and special housing design:
The pulsed light of the emitting diode is only focused by a lense and is directed on a reflector through polarising filter (principle of triple mirrors). A part of the reflected light reaches the receiver by a further polarising filter. The filters are selected and oriented in a way that only the light that is reflected by the reflector reaches the receiver. This arrangement avoids false signals for bright and glossy objects because of direct reflection. An object that interrupts the optical path between sender and receiver (via reflector) causes the switching of the output. In simplified version, there are also available reflective light barriers without polarising filter.
Operation area: |
|
One-way light barriers consist of a transmitter and a receiver in separate housings. The transmitter is directed in a way that a majority of the pulsed light of its transmitter diode reaches the receiver. An interruption of the light beam between sender and receiver causes the switching of the output.
Operation area: |
|
Fork light barriers are one way light barriers where sender and receiver are arranged in a fixed distance to each other (mainly in U-shape). This guarantees the optimal alignment of the optical elements.
Operation area: |
|
Angle light barriers are one way light barriers where the sender and the receiver are arranged in a fixed distance to each other (mainly in L-shape). This guarantees the optimal alignment of the optical elements.
Operation area: |
|
Frame light barriers consist of multiple one way light barriers that are closely arranged in parallel inside a shared housing. This creates a field where objects are detected independently of their exact position.
Operation area: |
|
Luminescence sensors are working with UV light on the side of the transmitter. Surfaces with luminescent characteristics change this UV light in visible light. On the side of the receiver, luminescence sensors are reacting only to visible light, not on UV light. Because of this, these sensors detect only objects with natural luminescence or with special applied markings.
Operation area: |
|
LCC series laser copy counters are primarily created for detecting and counting of printed products that are arranged in overlapping shape. For optimal working areas, there are detected paper edges of a thickness starting from typ. 50 µm. The sensors of the LCC series are characterised by a secure function and a simple handling as well as its solid mechanical construction. This sensor series offers high sampling frequencies of up to 1,5kHz and can be adjusted to bright and dark or small and low moving parts.
operation area: |
|
Light grids are one way systems with different numbers of beams and distances. Special security light curtains are used for applications where the security of persons depends on its proper function.
operation area: |
|