KEYWORDS: Calibration, 3D displays, Distortion, 3D vision, Semiconductor lasers, Microelectromechanical systems, Mirrors, 3D image processing, Laser based displays, LCDs
We have developed a calibration method for synchronizing the autostereoscopic viewing zones displayed by an array of “trixels”, i.e., laser modules with integrated MEMS mirrors. Calibration patterns are projected onto a calibration screen and recorded by a camera. The distortion functions, which map the laser diode driving signals from the time domain to the intensity distributions in the spatial domain, are extracted from the recorded calibration patterns. Unlike conventional autostereoscopic displays, e.g., with lenticular lenses or parallax barriers, the optimal 3D viewing distance of the display can be adapted on-the-fly by transforming the distortion functions using linear operations.
For many applications of MEMS actuators a well-defined trajectory of the movable device component is crucial when using a simple and inexpensive open-loop controller. We have applied to quasi-statically actuated electromagnetic MEMS mirrors the control technique called "input shaping", which is widely used for systems at the macro-scale and to a lesser extent also to systems at the micro-scale. We derive the impulse response of a filter which suppresses the excitation of undesired resonant modes and present simulation and measurement results of the oscillation-free linear MEMS mirror movement. The robustness of different input shaping filter types with respect to errors in the estimation of the system parameters, i.e., resonance frequency and damping ratio, is analyzed.
We have developed highly compact RGB laser light modules to be used as light sources in multi-view autostereoscopic
outdoor displays and projection devices. Each light module consists of an AlGaInP red laser diode, a GaInN blue laser
diode, a GaInN green laser diode, as well as a common cylindrical microlens. The plano-convex microlens is a so-called
“fast axis collimator”, which is widely used for collimating light beams emitted from high-power laser diode bars, and
has been optimized for polychromatic RGB laser diodes. The three light beams emitted from the red, green, and blue
laser diodes are collimated in only one transverse direction, the so-called “fast axis”, and in the orthogonal direction, the
so-called “slow axis”, the beams pass the microlens uncollimated. In the far field of the integrated RGB light module this
produces Gaussian beams with a large ellipticity which are required, e.g., for the application in autostereoscopic outdoor
displays. For this application only very low optical output powers of a few milliwatts per laser diode are required and
therefore we have developed tailored low-power laser diode chips with short cavity lengths of 250 μm for red and
300 μm for blue. Our RGB laser light module including the three laser diode chips, associated monitor photodiodes, the
common microlens, as well as the hermetically sealed package has a total volume of only 0.45 cm³, which to our
knowledge is the smallest RGB laser light source to date.
The ongoing miniaturization of micro-opto-electro-mechanical-systems requires compact multifunctional packaging
solutions like offered by the three-dimensional MID (molded interconnect device) technology which combines
integrated electronic circuitry and mechanical support structures directly into one compact housing. Due to the
inherently large thermal resistance of thermoplastic MID substrate materials, temperature-sensitive applications
require carefully arranged thermal vias in order to reduce the thermal resistance of the packaging effectively.
This paper presents the analysis and optimization of various laser-drilled thermal via design parameters of MIDs
including hole diameter, pitch, plating thickness of the Cu/Ni/Au metallization layers as well as the void level
of the filling material inside the vias.
State-of-the-art autostereoscopic displays are often limited in size, effective brightness, number of 3D viewing zones, and maximum 3D viewing distances, all of which are mandatory requirements for large-scale outdoor displays. Conventional autostereoscopic indoor concepts like lenticular lenses or parallax barriers cannot simply be adapted for these screens due to the inherent loss of effective resolution and brightness, which would reduce both image quality and sunlight readability. We have developed a modular autostereoscopic multi-view laser display concept with sunlight readable effective brightness, theoretically up to several thousand 3D viewing zones, and maximum 3D viewing distances of up to 60 meters. For proof-of-concept purposes a prototype display with two pixels was realized. Due to various manufacturing tolerances each individual pixel has slightly different optical properties, and hence the 3D image quality of the display has to be calculated stochastically. In this paper we present the corresponding stochastic model, we evaluate the simulation and measurement results of the prototype display, and we calculate the achievable autostereoscopic image quality to be expected for our concept.
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