Buyers of smartphones, tablets or laptops expect absolute perfection in the processing of the devices from the manufacturer. Reliable quality control is therefore required to monitor the individual production steps. This can be done, for example, with the help of laser profile scanners such as the 'Scancontrol 29xx-10/BL' from Micro-Epsilon, which is designed for measuring tiny objects. One of its tasks is the inspection of adhesive beads in smartphone housings.

The particularly fine contours inside the smartphone and the very thin, sometimes semi-transparent adhesive beads are challenging in this test. It is therefore a matter of a 100% check for, among other things, the completeness of the bead or the height and width of the adhesive application. The same applies to logos on tablets or laptops: grooves are milled into the aluminum housing, which are then available for gluing in the logo elements. These elements must be flush with the housing so that logos do not protrude or protruding indentations cannot be felt. Laser line scanners measure these indentations to determine the flatness and depth. The parts to be glued in are also measured to ensure a perfect fit.

A laser profile scanner is used to monitor the production of smartphones, laptops and tablets.

© Mico-Epsilon

The laser profile scanner is equipped with 'Blue Laser' technology. An effective measuring range of 10 mm and a profile resolution of 1280 points result in a point spacing of 7.8 µm; this means that the laser profile scanner has more than twice the resolution of previous laser scanners with a measuring range of 25 mm. The blue laser line can also be imaged much more sharply than would be possible with a red line. As the light does not penetrate the object being measured and is more stable than the red version, even glowing and organic objects and even the smallest objects can be measured reliably.

The laser scanners work on the basis of the triangulation principle for two-dimensional profile detection. Instead of a point, a static laser line is imaged on the object to be measured by expanding it using special optics. A receiving optic detects the diffusely reflected light of this laser line and images it on a highly sensitive sensor matrix. From this matrix image, the controller calculates the position along the laser line (x-axis) in addition to the distance information (z-axis). These measured values are then output in a sensor-fixed, two-dimensional coordinate system. In the case of moving objects or when the sensor is traversed, it is also possible to determine 3D measurement values. The complete electronics are housed in the sensor housing. As the entire signal preparation and processing takes place here, there is no need for an external controller.

Author. Christian Kämmerer is Head of Sales for 2D/3D Optical Measurement Technology at Micro-Epsilon in Ortenburg.