Electricity + Control June 2018

PLANT MAINTENANCE + TEST + MEASUREMENT

Point to line: Laser triangulation Information provided by Micro-Epsilon

Optical measurement techniques play an essential role in the increasing automation of manufacturing and inspection processes.

M odern laser triangulation technology is re- sponsible for fast, high precision and relia- ble measurements of manufactured com- ponents and their measuring points. Measurement data is generally available in real time and so can be used to automatically correct and control the produc- tion process. The triangulation principle involves the measurement of distanceon awide rangeofmaterial surfaces where different measurement techniques are employed: the measurement of displacement, distance and position using a laser point, and pro- file or gap measurement using a laser line. Regard- less of how different these techniques are, they are united by their high precision, high speed and reli- ability. Optimised processes improve product quality, and reduce raw materials and energy, which mini- mises production costs. Laser point sensors The laser triangulation principle is based on a sim- ple geometric relation. A laser diode transmits the laser beam onto the measurement object. A lens focuses the reflected rays onto a CCD/CMOS ar- ray.The distance to the measurement object can be determined by the three-point relationship between the laser diode, the measuring point on the target object, and the projection on the CCD array. The measurement resolution can achieve a fraction of a

micrometre. As well as analogue interfaces, digital interfaces are also available for direct connection with the existing environment. Sensors with digital interfaces are configured via an external PC. Laser-based optical displacement sensors can measure the target from a long distance. Using a very small spot, which enables measurements on the smallest of parts, the measurement dis- tance in turn enables measurements to be taken against difficult target surfaces such as hot met- als. The non-contact principle enables wear-free measurement as the sensors are not subject to any physical contact with the target. Furthermore, the laser triangulation principle is ideal for very fast measurements with high accuracy and resolution. An example that requires fast, high precision measurements in a minimum design envelope are automated pick-and-place machines. Here, laser point sensors demonstrate their advantage when it comes to quality control of tiny components as they must be positioned with the correct side up, at the correct location and at the correct height. Other challenges include the inspection of even smaller IC pins of a component in order to insure that they are positioned at precisely the correct distance from the circuit board. These pins later enable connection to the circuit board. In order to guarantee proper soldering, the distance between both components cannot be too high.

Take Note!

The laser triangulation prin- ciple is based on a simple geometric relation. A laser diode transmits the laser beam onto the measurement object. A lens focuses the re- flected rays onto a CCD/ CMOS array. The distance to the measurement object can be determined by the three-point relationship between the laser diode, the measuring point on the target object, and the projection on the CCD array. 1 2 3

26 Electricity + Control

JUNE 2018