We discuss about a fully-staring THz video camera prototype intended for security screening. The camera utilizes so-called kinetic inductance bolometers to detect THz radiation in the bandwidth of 0.3-1 THz. The imaging distance is 2.5 m with the nominal field-of-view of 2 m × 1 m. The camera is equipped with a kilo-pixel detector array, intermediate-scale cryogenics operating at 6 K, and low-noise electronics to read out the whole detector array. Here, we focus on describing the wide field-of-view and close-looking optical system of the imager.
We present a fully-staring THz video camera prototype intended for security screening. The camera utilizes so-called kinetic inductance bolometers to detect THz radiation in the bandwidth of 0.3-1 THz. The imaging distance is 2.5 m with the field-of-view being 2 m × 1 m. The camera is equipped with a kilo-pixel detector array, large field-of-view optics, intermediate-scale cryogenics operating at 6 K, and low-noise electronics to read out the whole detector array. The imaging capabilities of the system are demonstrated through radiometric performance characterization and actual imaging experiments.
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.
Low-cost automotive laser scanners for environmental perception are needed to enable the integration of advanced driver assistant systems into all automotive vehicle segments, which is a key to reduce the number of traffic accidents on roads. Within the scope of the European-funded project MiniFaros, partners from five different countries have been cooperating in developing a small-sized low-cost time-of-flight-based range sensor. An omnidirectional 360-deg laser scanning concept has been developed based on the combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. The concept, design, fabrication, and first measurement results of a resonant biaxial 7-mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives is described. Identical resonant frequencies of the two orthogonal axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen, since it minimizes 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 a large mechanical tilt angle of ±6.5 deg in each axis. Due to the large targeted tilt angle of ±15 deg and because of the MEMS mirror actuator having a diameter of 10 mm, a cavity depth of about 1.6 mm has been realized.
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.
In this paper we given an overview of the design and predicted performance of a passive video-rate THz camera intended
for stand-off and walk-by concealed weapons and explosives detection. The system is based on previously reported
work, and it utilizes a linear array of superconducting antenna-coupled microbolometers. Our present efforts have
focussed on improving the performance, stability, set-up time and cost of production of the camera. The system is
designed to acquire near video frame rate (~10 Hz) passive THz imagery of objects at ~5 meters from the system, with a
field-of-view of 2 m x 1 m and a spatial resolution of 1 cm. The system will be readily integrated to other security
systems as it provides encrypted stream of THz imagery over conventional LAN interface that also allows for remote
Virtual reality projection systems have been used formerly to study if mammals, including humans, are able to act in or
understand virtual environments. Insects have been more difficult to study in such circumstances, one of the factors
being their large, almost hemispherical field of view. Designing such a projection system that is capable of fulfilling the
full field of vision of an insect is a challenging task. Normally, when designing a photographic objective, one of the
goals is to minimize field curvature in order to provide sharp image through the whole sensor surface. However, because
the image surface in this case is a sphere, flat field is not desirable and the design task becomes an opposite of a typical
camera lens. Introducing field curvature becomes mandatory. We have designed and built a system with satisfactory
image quality throughout the whole spherical surface with reasonable number of lenses as an add-on for common digital
projectors. The manufactured system is able to project an image to a solid angle of 11.95 steradians, and when compared
to the whole sphere which is represented with a solid angle of 4π steradians, approximately 5 % of the total sphere area is
We present the design of a 24 mm long variable focus lens for 1/4" sensor. The chosen CMOS color sensor has VGA (640×480) resolution and 5.6 μm pixel size. The lens utilizes one Varioptic Arctic 320 liquid lens that has a voltage-controllable focal length due to the electrowetting effect. There are no mechanical moving parts. The principle of operation of the liquid lens is explained briefly. We discuss designing optical systems with this type of lens. This includes a modeling approach that allows entering a voltage value to modify the configuration of the liquid lens. The presented design consists only of spherical glass surfaces. The choice to use spherical surfaces was made in order to decrease the costs of manufacturing and provide more predictable performance by the better established method. Fabrication tolerances are compensated by the adjustability of the liquid lens, further increasing the feasibility of manufacturing. The lens is manufactured and assembled into a demonstrator camera. It has an f-number of 2.5 and 40 degree full field of view. The effective focal length varies around 6 millimeters as the liquid lens is adjusted. In simulations we have achieved a focus distance controllable between 20 millimeters and infinity. The design differs from previous approaches by having the aperture stop in the middle of the system instead of in front.
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.