The presented vision system integrates a focus tunable lens allows to perform fast autofocus and distance measurement at the same time. By deriving the best focus from the maximum position of a fitted distribution, it is not required to capture the image with the actual best focus during the autofocus sweep, resulting in high speed and robustness of the algorithm. In this work, we demonstrate that a focus tunable lens in conjunction with an autofocus algorithm can reliably measure distance to an arbitrary object in less than a second (depth from focus). The accuracy of the distance measurement is in line with the depth of field of the imaging system. No additional hardware is required apart from the imaging system comprising camera, objective lens and focus tunable lens. The fast and accurate focus and distance measurement enables and simplifies various applications ranging from robot vision to smart manufacturing control. The optics can be tailored to reach the desired precision and focus range, whereas there is generally a trade-off between the two.
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.
Based on selected liquid and elastic polymers, Optotune has developed adaptive optical components, such as focus
tunable lenses and laser speckle reducers.
The lenses range from 2 to 55mm in aperture, are mechanically or electrically actuated and offer a continuous range of
focal powers of several 10 diopters. This additional degree of freedom enables the design of compact optical systems,
typically with less mechanics. We show how tunable lenses can be used to improve optical designs for imaging and
illumination systems in terms of size, quality and speed.
The speckle reducers are based on electroactive polymers and offer an extremely compact and low cost solution for
removing speckles, which is a key benefit for laser projectors and illumination systems.
Several approaches have been demonstrated to build focus tunable lenses. The additional degree of freedom enables the
design of elegant, compact optical systems, typically with less mechanics. We present a new range of electrically and
mechanically focus tunable lenses of different sizes and tuning ranges and discuss their characteristics. We show how
tunable lenses can be used to improve optical design for auto-focus and zoom in terms of size, quality and speed.
Furthermore, we present an LED-based spot light with variable illumination angle, which shows optimal performance in
terms of spot quality and optical efficiency.