Mobile systems exploring Planetary surfaces in future will require more autonomy than today. The EU FP7-SPACE
Project ProViScout (2010-2012) establishes the building blocks of such autonomous exploration systems in terms of
robotics vision by a decision-based combination of navigation and scientific target selection, and integrates them into a
framework ready for and exposed to field demonstration.
The PRoViScout on-board system consists of mission management components such as an Executive, a Mars Mission
On-Board Planner and Scheduler, a Science Assessment Module, and Navigation & Vision Processing modules. The
platform hardware consists of the rover with the sensors and pointing devices.
We report on the major building blocks and their
functions & interfaces, emphasizing on the computer vision parts such
as image acquisition (using a novel zoomed 3D-Time-of-Flight & RGB camera), mapping from 3D-TOF data,
panoramic image & stereo reconstruction, hazard and slope maps, visual odometry and the recognition of potential
scientifically interesting targets.
The restricted field of view of traditional camera technology is increasingly limiting in many relevant applications such
as security, surveillance, automotive, robotics, autonomous navigation or domotics. Omnidirectional cameras with their
horizontal field of view of 360° would be ideal devices for these applications if they were small, cost-effective, robust
and lightweight. Conventional catadioptric system designs require mirror diameters and optical path lengths of several
centimeters, often leading to solutions that are too large and too heavy to be practical. We are presenting a novel optical
design for an ultra-miniature camera that is so small and lightweight that it can be used as a key navigation aid for an
autonomous flying micro-robot. The catadioptrical system consists of two components with a field-stop in-between: the
first subsystem consists of a reflecting mirror and two refracting lens surfaces, and the second subsystem contains the
imaging lens with two refractive surfaces. The field of view is 10°(upward) and 35°(downward). A field stop diameter of
1 mm and a back focal length of 2.3 mm have been achieved. For
low-cost mass fabrication, the lens designs are
optimised for production by injection moulding. Measurements of the first omnidirectional lens prototypes with a high-resolution
imager show a performance close to the simulated values concerning spot size and image formation. The total
weight of the optics is only 2 g including all mechanical mounts. The system's outer dimensions are 14.4 mm in height,
with a 11.4 mm × 11.4 mm foot print, including the image sensor and its casing.
Multi-mode VCSEL arrays are candidates for compact illumination modules with applications as flash light illumination
for the detailed imaging of fast moving objects (> 100 m/s) or for time-of-flight cameras with modulation frequency in
the > 10 MHz domain. Rise and fall times have to be as short as a few nanoseconds, while the optical output power has
to be in the order of one Watt. In this paper we investigate, for multi-mode VCSEL arrays, the dependency of the far-field
pattern on the drive current and on the distance to a reflecting surface. We demonstrate that, with the help of
diffusing elements, the current dependency of the far-field pattern can be reduced. We have realized an illumination unit
with modulation frequencies of up to 80 MHz and an optical output of 1 Watt.
CSEM presents a highly integrated ultra-miniature camera module with omni-directional view dedicated to autonomous
micro flying devices. Very tight design and integration requirements (related to size, weight, and power consumption)
for the optical, microelectronic and electronic components are fulfilled. The presented ultra-miniature camera platform is
based on two major components: a catadioptric lens system and a dedicated image sensor. The optical system consists of
a hyperbolic mirror and an imaging lens. The vertical field of view is +10° to -35°.The CMOS image sensor provides a
polar pixel field with 128 (horizontal) by 64 (vertical) pixels. Since the number of pixels for each circle is constant, the
unwrapped panoramic image achieves a constant resolution in polar direction for all image regions. The whole camera
module, delivering 40 frames per second, contains optical image preprocessing for effortless re-mapping of the acquired
image into undistorted cylindrical coordinates. The total weight of the complete camera is less than 5 g. The system's
outer dimensions are 14.4 mm in height, with a 11.4 mm x 11.4 mm foot print. Thanks to the innovative PROGLOGTM, a
dynamic range of over 140 dB is achieved.
Optical time-of-flight (TOF) distance measurements can be performed using so-called smart lock-in pixels. By sampling the optical signal 2, 4 or n times in each pixel synchronously with the modulation frequency, the phase between the emitted and reflected signal is extracted and the object's distance is determined. The high
integration-level of such lock-in pixels enables the real-time acquisition of the three-dimensional environment without using any moving mechanical components. A novel design of the 2-tap lock-in pixel in a 0.6 μm semiconductor technology is presented. The pixel was implemented on a sensor with QCIF resolution. The optimized
pixel design allows for high-speed operation of the device, resulting in a nearly-optimum demodulation performance and precise distance measurements which are almost exclusively limited by photon shot noise. In-pixel background-light suppression allows the sensor to be operated in an outdoor environment with sunlight incidence. The highly complex pixel functionality of the sensor was successfully demonstrated on the new SwissRanger SR3000 3D-TOF camera design. Distance resolutions in the millimeter range have been achieved
while the camera is operating with frame rates of more than 20Hz.
VCSELs (Vertical-Cavity Surface-Emitting Lasers) emit circularly symmetric beams vertical to the substrate; the small footprint of the active area (around 400 um2) enables the simultaneous fabrication of several thousand devices on a single wafer. Micro-optical components can modify the free-space optical properties of VCSELs for applications such as fiber-coupling in transceiver modules, illumination purposes, or beam profiling in sensing applications. However, the alignment of a laser towards a lens, for example, is expensive when performed separately for each device. Here we demonstrate a wafer-scale replication process to realise microlenses directly on top of the undiced VCSEL wafers. The process combines uv-casting and lithography to achieve material-free bonding pads and dicing lines. Several examples of lenses and gratings are given. An organically modified sol-gel material (ORMOCER) has been used as lens material. The micro-optical components on the wafer show good stability while sawing and bonding, where temperatures up to 220°C may occur. We have compared refractive lenses on top of the VCSELs with lenses on glass substrates. The lenses on the glass wafers were illuminated from the back-side by a planar wave. Spot diameters around 1.2 um and focal lengths of 30 um to 100 um were measured depending on the radii of curvature. On the VCSELs the lenses showed a strong influence on the transversal mode behaviour.
A new wafer-scale replication process for fabricating buried ridge
waveguides for telecom/datacom applications using an uv-curable
sol-gel material is proposed. Spin coating of the core material on
the replication mould is used to form the waveguide cores with a
smooth thin layer. The spin parameters allow an accurate control
of the thickness and homogeneity. The bottom-cladding is uv-cast
between a substrate and the mould, which is covered by the spun
core layer. The ridge waveguide cores are demoulded and buried
under a top cladding. This process allows the stacking of several
layers of waveguides on top of each other to form two-dimensional
waveguide arrays. A specially adapted SUSS mask aligner is used to
control the cladding thickness between individual waveguide layers
and to align them. A waveguide loss comparable to lithographically
fabricated waveguides has been achieved.
Tandem chirped grating couplers for spectral measurement applications in optical communications are developed. The current devices are designed to monitor data/telecom dense wavelength-division multiplexing (DWDM) channels in the spectral range from 1528 to 1561 nm (C-Band). A replication process provides the diffractive structures, on the gratings a high-index waveguide material is deposited. Design parameters and fabrication tolerances are discussed in detail, and measurement results of the fabricated devices are presented.
Planar optics is an approach to monolithically integrate free-space optical system. Diffractive microoptical elements are etched into a transparent substrate which serves as a medium for light propagation as well as a board for optoelectronic or electronic components. Mirrors and imaging optics are sued to keep the light traveling within the substrate along a zigzag path. Arrays of VCSEL devices can be integrated on the substrate by means of flip-chip bonding. Among the interesting applications of that technology are optical interconnections for VLSI systems where the optics can provide a large number of parallel channels. A critical issue of the practical realization is the light efficiency of the optical interconnect. Here, we propose a planar-optical implementation of the interconnect using analog grey-scale lithography resulting in a light- efficiency optical system.
Planar integrated free-space optics has been suggested and demonstrated as a micro-optical systems technology for optical interconnection and processing. It is based on the integration of micro-optical elements on a single glass substrate. Active optoelectronic components are mounted onto the substrate using hybrid integration techniques. An important problem related to the packaging is the heat removal from these active device arrays. A high interconnection density -- which is desirable from an architectural point of view -- can cause a dissipated power on the order of 100 W/cm2. This may compromise the performance of individual devices and the system as a whole. As cooling mechanisms, we consider convection which requires sufficiently large surfaces and conduction in an intermediate layer of high thermal conductivity between the passive optics and the optoelectronics. Both, structured silicon coolers and diamond layers are of interest for a practical realization. Here, we discuss material and design aspects of heat spreaders. Both, theoretical modeling and experimental results are presented. A test setup including an array of vertical cavity surface emitting lasers (VCSELs) is analyzed. The temperature distribution on the array is determined experimentally by the shift of the optical wavelength. Computer simulations are used to evaluate the experimental data.