New Principle for 3D Inline Inspection

ZFokus Depth-from-Focus

Optical 3D inspection has already established itself in many industrial manufacturing environments. So far, most processes have failed when it comes to small components. Senswork answers the problems with the new 3D inline camera ZFokus.

Laser line triangulation, strip light projection or time-of-flight cameras capture the third dimension of products in production. In this way, errors can be recognized and components localized. Nevertheless, the three-dimensional inspection of small components such as connector components, micro-injection molded parts, electronic SMD components or even soldered joints poses great, if not insurmountable, challenges for the currently available 3D sensors. The company senswork (a system house for industrial image processing) has dedicated itself to this topic and, with ZFokus, has launched a new type of 3D inline camera based on the depth-from-focus principle.

Accuracy up to 10 µm

ZFokus is used in clocked inline processes or in offline testing in the high-resolution 3D evaluation of small and very small components. The classic technologies such as laser scanning and strip light projection are unsuitable for checking for numerous reasons. The main reasons are disruptive artifacts on component edges, problems with overexposure and reflection on the component as well as shadowing, which are generally caused by the triangulation principle.

With the depth-from-focus method (DfF or focus variation), several hundred images are recorded in a very short time (typically 1-2 seconds) by the ZFocus system to calculate the 3D image information. The camera then calculates a 3D height map of the component based on location-dependent focus values in the image. The ZFokus-Controller takes care of the feed-synchronous recording, the calculation of the 3D data takes place on a commercially available but powerful embedded PC almost in real time for the image recording sequence.

Parallel Data Processing

The strengths of the system lie in the high-performance parallel processing of the large amount of image data per scan (several gigabytes per scan), as well as the intelligent calculation of the Z information by taking into account the reflection conditions on the component. With the aid of fast, robust interpolation algorithms, the height information is calculated with a very high level of quality and precision.

The currently achievable resolution in the Z direction is 10 µm with a maximum field of view of 12 x 12 mm². The scan duration depends on various factors and is typically 1-3 seconds. A further development of the camera towards even larger fields of view is currently being planned. ZFokus is used in various industries, whereby the aim of developing senswork was to test connector modules, electronic components or micro-injection molded parts.

Wear-Free Test

Since ZFokus is based on a non-contact measurement, the advantage over mechanical probing methods for coplanarity testing or pin height testing is obvious: the component is not mechanically influenced during the measurement, the method is wear-free, and in addition to the maximum Z position of For example, a contact surface can also be used to determine the angular position or the orientation of the surface in space.

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