The Operating Principle of InfiniteFocus: Focus Variation
The specimen is placed onto the motorized stage and is illuminated with modulated white light. The coaxial white light is provided by a light source delivered through a beam splitter to a series of selectable, infinity-corrected objectives contained in a six-place nosepiece. The specimen’s reflected light is projected through the beam splitter onto a color digital sensor.
The selection of both, vertical and lateral resolution can be realized through a simple change of objectives. The resulting image is similar to conventional light microscopy in a way that it shows limited depth of focus. As the distance between the object and objective is varied images are continuously captured. Each position in depth is differently imaged depending on the 3D structure of the specimen. The harmonized interaction between modulated illumination, vertical scanning and sensor capturing is crucial for this process. The innovative Alicona SmartFlash® technology realizes this interaction. For each position on the object sharpness is calculated. The variation of sharpness is now utilized for extracting depth information. A dense 3D surface representation of the object is obtained.
The operating principle Focus-Variation has been added to the latest ISO standard for classifying surface texture methods. The new ISO norm 25178 for the first time includes standardized parameters to classify optically area based measurements. As an official member of the responsible ISO committee, Alicona contributes in defining the classifications of methods for surface measurement techniques. Further standards are in work.