Laser light sources have inherent advantages in terms of brightness and low beam divergence. However, the coherence of lasers causes speckle to form on the target. In this paper, we show how electroactive polymers can provide a compact and energy-efficient solution to reduce laser speckles. The design parameters are discussed. The speckle reducers are characterized both mechanically and optically. Finally, a case-study is presented, illustrating the implementation of the speckle reducer into a compact laser projector system.
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.
Optical gratings are used for light steering, wavelength separation, and filtering. So far, tunable diffraction gratings were
based on relatively stiff materials allowing only a limited spatial tuning range. In this paper, we describe a technology for
the implementation of shape changing, electrically adjustable, transmissive optical elements. To achieve large shape
changes, soft optical materials and dielectric elastomer actuators (DEAs) are combined. The discussed optical
transmission gratings operate with high transmission (> 90 %), good optical quality, high damage threshold
(> 93 kW/cm2), are polarization independent, and achieve very large, continuous changes in their main optical properties
(7.5 % in-plane compression of the active optical region). Further, the excellent properties of the novel optical
components are highlighted by the implementation of a low cost, objective launched, total internal reflection
fluorescence (TIRF) microscope that can be switched from epifluorescence operation to TIRF mode by simply applying
a voltage to a DEA tuned diffractive transmission grating.
We present an electrically tunable diffraction grating, driven by thin-film dielectric elastomer actuators. The device
combines the advantages of dielectric elastomer actuators, capable of generating very large strains, with the desirable
properties of Micro-Opto-Electro-Mechanical Systems (MOEMS). The soft materials based tunable diffraction grating
achieves a continuous grating period change of 19.2%, when a voltage of 500 V is applied. This is an improvement by a
factor of 90 compared to conventional analog tunable diffraction gratings based on hard materials. Further device
characterization yielded a tunable angular range of more than 100 mrad. Additionally, we show that in combination with
a collimated white light source (e.g. white light emitting diode), the discussed tunable diffraction grating can be used for
wavelength-adjustable luminous sources. Integrated into displays, these light sources could facilitate the first technology
able to reproduce all perceivable colors.