Abstract
Focusing in milliseconds without translational mechanics involved is possible with electrically tunable lenses. Fast
shape-changing lenses enable fast imaging systems which can focus at distances from infinity to a few centimeters with a
high optical quality. Furthermore, rapid laser processing in three dimensions is realized without mechanical translation of
the focusing lens or the sample. With tunable lenses the entire optics can be made compact, robust and abrasion-free.
Different configurations are discussed, how to integrate the tunable lens in the optical path. For machine vision
applications, the achievable optical quality depends on the chosen combination of the tunable lens with a fixed focal
length lens and a camera. It is recommended to use a fixed focus lens with a short distance between the stop position and
the front of the lens. Furthermore, important points are presented how to achieve optimal performance in laser processing
applications such as orientation and position of the tunable lens and the diameter of the beam incident on the lens.
Additionally, different approaches will be discussed for monitoring the focal length of the tunable lens. The focal length
of the tunable lens is sensitive to temperature changes, as the lens material is a fluid. However, in contrast to
conventional lenses, the focal length of the tunable lens can be corrected electrically. For that purpose, the tunable lens
exhibits an integrated temperature sensor for temperature compensation. Also optical feedback solutions will be
presented for applications requiring highest precision and tracking of the absolute focal length value.
