Up to now, geometries such as bore holes of injection valves in the automotive industry were difficult to measure optically. The lateral probing of components with vertical surfaces was limited to tactile measuring systems, CT solutions or complex customized solutions. This changes with Vertical Focus Probing, an extension of Focus-Variation technology. Based on areal measurements, the optical probing of components over the entire surface is possible.

Different optical measuring methods allow the measurement of components with different flanks. The spectrum of measurable flanks or slopes has so far covered 0° - 85°, whereby in industrial practice, Focus-Variation has established itself as the most suitable method for steep flanks. However, this technology has also reached its limits for components that show flanks steeper than 85°. Nonetheless, Bruker Alicona has been constantly developing Focus-Variation for 15 years and has complemented their optical measurement principle with a new technique, Vertical Focus Probing. Even surfaces with slopes of more than 90° can now be optically touched and measured in 3D.

Diferentes tecnologías permiten la medición de componentes con diferentes flancos. Aquí: Superficies con 0 °, 60 ° y 90 °

How high the proportion of reflected light rays is, depends on the geometry and the roughness of the surface to be measured as well as on the light source used. The objective also plays a role, as, depending on its diameter, an objective can also capture reflected light from surfaces that show flanks steeper than 90°.

This is where the numerical aperture (AN) comes into play, which is defined by the objective diameter and the working distance. It influences how much the measurable slope of a surface can still exceed the 90° mark.

Optical hole measurement

Typical applications of Vertical Focus Probing are, as of example, the measurement of micro bore holes such as injection nozzles or cooling holes.

The diameter to depth ratio of holes ranges from 1:3 to 1:10, the measurable diameter is 0.1 mm to 2 mm. Users measure parameters such as outer and inner diameter and opening angle.

Multiple hole measurement

In combination with an automatic rotation unit "µCMM Real3D", turning the 3-axis CMM into a 5-axis system, multiple holes including their orientation to each other can be measured. One application which can be achieved is the measurement of injection nozzles including diameter, K-factor, injection angle and side angle.

This new technology is an extension of the Focus-Variation technology and hence a pure optical measurement technology. It allows the measurement of vertical walls and micro holes directly without articulating the sample during the measurement. Read in this recently published R&D paper more about the measurement principle of Vertical Focus Probing and the impact of this method with respect to micro hole measurement and 3D measurements of steep flanks with a slope angle of more than 90°. For all measurements the optical coordinate measurement machine µCMM is used.