Mika Aikio

A fast and flexible panoramic virtual reality system for behavioural and electrophysiological experiments.

Ideally, neuronal functions would be studied by performing experiments with unconstrained animals whilst they behave in their natural environment. Although this is not feasible currently for most animal models, one can mimic the natural environment in the laboratory by using a virtual reality (VR) environment. Here we present a novel VR system based upon a spherical projection of computer generated images using a modified commercial data projector with an add-on fish-eye lens. This system provides equidistant visual stimulation with extensive coverage of the visual field, high spatio-temporal resolution and flexible stimulus generation using a standard computer. It also includes a track-ball system for closed-loop behavioural experiments with walking animals. We present a detailed description of the system and characterize it thoroughly. Finally, we demonstrate the VR system’s performance whilst operating in closed-loop conditions by showing the movement trajectories of the cockroaches during exploratory behaviour in a VR forest.

Fisheye optics for omnidirectional perception

This document describes the design process of fisheye optics designed for omnidirectional perception in automated guided vehicles. Requirements for a custom designed fisheye lens are first derived from the application requirements. Based on these requirements the selected measurement geometry and lens design are explained and justified. Some expected optical performance values are listed and also the upcoming test procedures are described. The overall target of the paper is to present the specification, design and test phases of the application oriented fisheye optics design task which was done as a part of the EC-funded PAN-Robots project.

Add-on laser reading device for a camera phone

A novel add-on device to a mobile camera phone has been developed. The prototype system contains both laser and LED illumination as well as imaging optics. Main idea behind the device is to have a small printable diffractive ROM (Read Only Memory) element, which can be read by illuminating it with a laser-beam and recording the resulting datamatrix pattern with a camera phone. The element contains information in the same manner as a traditional bar-code, but due to the 2D-pattern and diffractive nature of the tag, a much larger amount of information can be packed on a smaller area. Optical and mechanical designs of the prototype device have been made in such a way that the system can be used in three different modes: as a laser reader, as a telescope and as a microscope.

Optical and Electrical Characterization of a Large Kinetic Inductance Bolometer Focal Plane Array

Sub-THz imaging techniques are currently emerging with applications especially in security screening requiring higher throughput in mass transit and public areas. In the context of person imagers, the field of view and the spatial resolution set the requirement for the number of image pixels. We perform an experimental feasibility study on a fully staring radiometric camera with one detector per image pixel. The aim is to avoid the shortcomings characteristic of optomechanical scanners with a limited number of detectors. Our approach is based on superconducting kinetic inductance bolometer arrays. We demonstrate successful fabrication and operation of a focal plane array with 2500 nanomembrane-integrated bolometers, and a compatible optical system enabling standoff imaging at the distance of 5 m. We characterize the system in terms of radiometric contrast and spatial resolution.

Bolometric kinetic inductance detector technology for sub-millimeter radiometric imaging

Radiometric sub-millimeter imaging is a candidate technology especially in security screening applications utilizing the property of radiation in the band of 0.2 – 1.0 THz to penetrate through dielectric substances such as clothing. The challenge of the passive technology is the fact that the irradiance corresponding to the blackbody radiation is very weak in this spectral band: about two orders of magnitude below that of the infrared band. Therefore the role of the detector technology is of ultimate importance to achieve sufficient sensitivity. In this paper we present results related to our technology relying on superconducting kinetic inductance detectors operating in a thermal (bolometric) mode. The detector technology is motivated by the fact that it is naturally suitable for scalable multiplexed readout systems, and operates with relatively simple cryogenics. We will review the basic concepts of the detectors, and provide experimental figures of merit. Furthermore, we will discuss the issues related to the scale-up of our detector technology into large 2D focal plane arrays.

Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning

Low-cost automotive laser scanners for environment perception are needed to enable the integration of advanced driver assistant systems (ADAS) into all automotive vehicle segments, a key to reducing the number of traffic accidents on roads. An omnidirectional 360 degree laser scanning concept has been developed based on combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. This omnidirectional scanning concept is the core of a small sized low-cost time-of-flight based range sensor development. This paper describes concept, design, fabrication and first measurement results of a resonant biaxial 7mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives. Identical frequencies of the two resonant axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen since it allows minimizing the frequency splitting of the two resonant axes. Low mirror curvature is achieved by a thickness of the mirror of more than 500 μm. Hermetic wafer level vacuum packaging of such large mirrors based on multiple wafer bonding has been developed to enable to achieve a large mechanical tilt angle of +/- 6.5 degrees in each axis. The 7mm-MEMS mirror demonstrates large angle circular scanning at 1.5kHz.

Biaxial Tripod MEMS Mirror and Omnidirectional Lens for a Low Cost Wide Angle Laser Range Sensor

Low cost laser scanners for environment perception are a need to facilitate ADAS integration into all vehicle segments. To fulfill the need for mass-producible compact low cost laser range sensors MEMS mirrors in combination with replicable low cost plastic optics are expected to be suitable components. This paper describes concept, design, fabrication and first measurement results of a compact omnidirectional scanning system based on an omnidirectional lens and a biaxial large aperture tripod MEMS mirror. A hermetic vacuum wafer level packaging process of the resonant MEMS mirror is essential to meet automotive requirements and to achieve the required large total optical scan angles of 60 degrees in both scan axes.

Pulsed LED Illumination for High Speed Imaging

High speed imaging with decent image quality is difficult because the available exposure times are very short, which leads to the usage of a large aperture. Unfortunately, large aperture also decreases the depth resolution of the system, which reduces the quality of the image. Thus the source of illumination has to be able to output a high amount of energy in a very short time so that the aperture requirement can be relaxed. There are only a few Xenon flash lamps that fulfill the requirement of sub-microsecond pulses, so the natural choice would be to use lasers. However, when the target surface is rough, high degree of coherence causes black and white interference patterns known as speckle. The sensor might register irradiance values from zero to saturated state. Needless to say, this reduces drastically the quality of the image. There is variety of techniques for speckle removal, ranging from chaotic laser states to digital signal processing [1-5]. In this paper we discuss an alternative, namely LEDs, for this kind of illumination. The authors have performed some experiments and theoretical modeling, and successfully demonstrated an illumination system based on LEDs that can output enough energy to enable imaging with pulse lengths of 100 ns.

The PAN-Robots Project: Advanced Automated Guided Vehicle Systems for Industrial Logistics

In modern manufacturing plants, automation is widely adopted in the production phases, which leads to a high level of productivity and efficiency. However, the same level of automation is generally not achieved in logistics, typically performed by human operators and manually driven vehicles. In fact, even though automated guided vehicles (AGVs) have been used for a few decades for goods transportation in industrial environments [1], they do not yet represent a widespread solution and are typically applied only in specific scenarios.

Fisheye optics for omnidirectional stereo camera performance evaluation for AGV applications

Omnidirectional stereo cameras have been proposed to be applied as a safety sensor in automated guided vehicles. As a part of the EC-funded PAN-Robots project, a custom designed high performance omnidirectional stereo camera with fisheye objectives was designed and manufactured. This paper shows the results of the optical and environmental tests which were done for the fisheye objectives and for the omnidirectional stereo camera system.