Triangulation measurement: how it works and what to use it for

In this article we discuss the step-by-step effect of a triangulation measurement.

The fundamentals of a triangulation measurement

In sensors based on triangulation, the (laser) light source, the measured surface and the line sensor form a triangle. We call these sensors triangulation lasers or laser displacement sensors. Triangulation sensors are used to measure distances to an object fast and accurately.

Triangulation with displacement lasers

How exactly does triangulation work?

How a triangulation works - illustrated schematically

Through the laser or LED diode a concentrated light beam is projected on an object. The light is deflected in all directions by the surface of the object. A part of this deflected light is caught by a special line sensor with small photo sensors in a row, so-called pixels.

The line sensor of a triangulation sensor

Where the deflected part falls on the chip exactly is dependent of the position of the object. A displacement of the object causes a displacement of the light on the line sensor.

You can think of a ceramic tile with a glossy surface. This reflects the emitted light of the line sensor to its receiver. During the movement of the tile the angle of incidence and reflection are constantly changing. 

A good example of a laser displacement sensor is the L-WELD-LT-250-AL. This is a triangulation sensor with a measuring range of 440 mm, a resolution of 250 µm and a top speed for measurements per second of 3.8 kHz!   

The row of pixels in a line sensor as part of a laser displacement sensor in a triangulation measurement.

The result

Displacement of an object is measured or detected with a triangulation measurement.

This way, the displacement of the object can very accurately be translated to a distance. By manual or automatic settings it is possible to adjust the intensity of the laser. This allows these sensors to determine the position of transparent or reflecting objects. The displacement lasers or triangulation sensors are used for very accurate distance measurements in micrometer range with high measurement speeds up to several kHz. Or for distance measurements on different materials, surfaces and colors.

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