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Laser distance sensors

Laser distance sensor OADM

Measuring principle

The optical principal is based on triangulation. The OADM laser puts a small bright spot on the object. The receiver of the sensor detects the position of this spot. The angle increases with the distance of the object. The sensor basically measures this angle and then calculates the distance.

laser sensors

The possible resolution and accuracy changes with distance. The same distance delta d, that causes a large angular change alpha1 close to the sensor, causes a much smaller angular change alpha2 further away (see figure).

laser sensors

The receiver inside the sensor is a linear photo diode array or in the faster versions a PSD. The photodiode array is scanned by the built in micro controller. From the distribution of light along the diode array the controller precisely calculates the angle and from the angle it calculates the distance of the object. This distance is either transferred to the serial port or converted to a distance-proportional output current. The microcontroller assures high linearity and precision of the measurement. The combination of photo diode array and micro controller allows for suppression of disturbing reflections thus providing reliable data on critical surfaces. The sensor adapts to different colors by changing its internal sensitivity, making it nearly independent of the color of the object. A digital output is activated when no object is present within the measuring range. Another digital output activates an alarm, if there is not enough light to detect an object correctly e.g. the sensor is soiled.