Optical metrology

What is optical metrology?

Optical metrology is a method for measuring surface geometries without contact by means of photogrammetry. Using this method, entire surfaces are acquired, not just individual measurement points.  Optical metrology is suitable in particular for complete component analysis. With this method, the surface of the component is digitised without contact using a 3D scanner and analysed quickly and with a very high point density – in our accredited measuring rooms or directly on site in your facility. The spectrum of components ranges from prototypes, through sheet metal to injection moulded and die-cast components, as well as battery trays.

Can analyses using optical metrology be automated?

Checking and quality assurance on individual components can also be fully automated using optical measurement methods. For this purpose, the item inspected is placed in the 3D scanner or the coordinate measuring machine by a robot and the measurement starts. Such an automated surface analysis is particularly advantageous if high quantities of individual components are to be inspected during manufacture or if work in dust-free or sterile conditions is required.

For which applications is optical metrology suitable?

Optical metrology is suitable for numerous workpiece inspections, such as dimensional inspections, surface comparisons or initial sampling. The primary obstacle for optical inspection is the need for high accuracy. In such a case, tactile measurement methods are superior; these methods are accurate to the micron, however they require more time. Which advantage is more important must be considered in each specific situation. In general terms it can be stated that the measurement method applied must be five times more accurate than the largest tolerance that is still acceptable. If you are still unsure which method is most suitable for your requirements, simply talk to us - we will be pleased to help you.

Does quality analysis offer optical measurements also on site in our facility?

Yes, our measurement systems are suitable for mobile use and are therefore excellently suited to a measurement on site in your facility. If you cannot or do not want to have the inspection undertaken in our accredited inspection rooms for logistical, time or production-related reasons, we would be pleased to come to you and undertake the necessary measurements on site. If your parts cannot come to us, we will come to you!

What are the advantages of optical metrology?

Above all else, optical metrology has five key advantages over tactile methods.

Sensitivity to physical contact

Numerous workpieces and materials in modern industrial sectors such as the electrical engineering industry are extremely sensitive to physical contact. Optical 3D metrology is therefore ideal for these parts because there is never any contact between the item and the sensors during the measurement, unlike tactile methods for industrial metrology. In this way damage by the measuring machine is excluded.

Electrically live parts

Particularly in the automotive and e-mobility sector, optical metrology is very important because sampling without physical contact is of course particularly important for electrically live components. Optical metrology plays an important role above all for:

• Vehicle attachment points
• Busbars
• Distortion of the complete battery
• Incoming goods inspection of the individual components to be installed
• Development (load test, simulation of load cycles, etc.)

There are numerous possible applications; one of the most important advantages is that there is no physical contact with the surface and therefore the inspection is non-destructive, which means that the surface of a component must not be damaged and there must not any physical contact with electrically live parts (cells, batteries, delicate materials).

Maximum data density

Optical measurement methods provide a data density that is far superior to that of the tactile methods. Using a 3D scanner, as we use it, not only are individual coordinate points measured on the item inspected, a three-dimensional model is also created. Such a result is not possible with tactile metrology, even with thousands of measurement points.

All data always available

With optical metrology all features from the area scanned are acquired and made available in a 3D model. The information can be retrieved at any time. This means that additional features from the model can be measured also after the measurement. With tactile metrology the component would have to be clamped and measured again.

Time saving thanks to optical metrology

In practice the sampling of just a few hundred measurement points by means of physical contact is a major challenge; although it would be feasible technically, the sampling would be time consuming - this type of inspection process can take several hours. It is a matter of course that such inspections must be limited to random samples during production. Optical measurement methods, on the other hand, are very precise and fast because the measurement and digital transmission occur almost in realtime. These methods are suitable for solving very complex, critical measuring tasks. An optical measurement takes only a few minutes or even just seconds.

What are the disadvantages of optical metrology?

Optical metrology provides a high data density in a very short time. Why is it then not used everywhere?

Optical vs. Tactile measurement - which is more accurate?

This question is very easy to answer: tactile measurement is more accurate. While it is possible to measure to better than a thousandth of a millimetre using tactile methods, the resolution of optical measuring systems is "only" sufficient for measurements in the range of a few hundredths of a millimetre. For many applications, however, that is not precise enough.

Mirror and glass

Due to their characteristics, some surfaces require a pretreatment so that they can be analysed using optical measuring instruments. The workpiece must be treated with a spray to make it matt so that homogeneous and highly accurate data can also be generated for very glossy and transparent surfaces. This spray is applied very thinly and does not affect the accuracy of the measurement. Alternatively, tactile measurement can also be used in some situations.