Philips Laou

Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO2 layer.

Vanadium oxide films for optical modulation applications

Thin films of vanadium oxide were prepared and studied for the electro-optical properties of semiconductor-metal transition. Vanadium oxide films with thickness of ~ 0.15μm were deposited on SiO2/Si substrates by reactive RF magnetron sputtering using a pure vanadium target under various ratios of argon and oxygen gases. The oxygen content in the mixed atmosphere has a significant influence on the semiconductor-metal transition characteristics. Both thermochromic and electrochromic modes were studied. In thermochromic mode, the oxide film deposited in an O2/Ar ratio of 1.2% exhibits 90% optical transmission in semiconducting state at room temperatures, while very low transmission at 5% in metallic state at 65°C, in the wavelength region of 8 to 12μm. In the near infrared region of 1 to 2μm, the transmission is about 60% in the semiconducting state and a few percents in the metal state. A corresponding three-order variation of resistivity was observed over the transition. The refractive indices (n and k) of the vanadium oxide films were measured using an ellipsometer in the near infrared region between 1 and 2 μm in both states. The index n decreases in metal state while k increases. The electrochromic phase transition of vanadium oxide was investigated by applying a pulsed voltage to minimize the heating effect. The required charge density for the phase transition is consistence with the Mott metal-insulator model. Longwave IR switching and modulation were demonstrated by electrically induced semiconductor-metal transition.

Lightweight uncooled TWS equipped with catadioptric optics and microscan mechanism

A rugged lightweight thermal weapon sight (TWS) prototype was developed at INO in collaboration with DRDC-Valcartier. This TWS model is based on uncooled bolometer technology, ultralight catadioptric optics, ruggedized mechanics and electronics, and extensive onboard processing capabilities. The TWS prototype operates in a single 8-12 μm infrared (IR) band. It is equipped with a unique lightweight athermalized catadioptric objective and a bolometric IR imager with an INO focal plane array (FPA). Microscan technology allows the use of a 160 x 120 pixel FPA with a pitch of 50 μm to achieve a 320 × 240 pixel resolution image thereby avoiding the size (larger optics) and cost (expensive IR optical components) penalties associated with the use of larger format arrays. The TWS is equipped with a miniature shutter for automatic offset calibration. Based on the operation of the FPA at 100 frames per second (fps), real-time imaging with 320 x 240 pixel resolution at 25 fps is available. This TWS is also equipped with a high resolution (857 x 600 pixels) OLED color microdisplay and an integrated wireless digital RF link. The sight has an adjustable and selectable electronic reticule or crosshair (five possible reticules) and a manual focus from 5 m to infinity standoff distance. Processing capabilities are added to introduce specific functionalities such as image inversion (black hot and white hot), image enhancement, and pixel smoothing. This TWS prototype is very lightweight (~ 1100 grams) and compact (volume of 93 cubic inches). It offers human size target detection at 800 m and recognition at 200 m (Johnson criteria). With 6 Li AA batteries, it operates continuously for 5 hours and 20 minutes at room temperature. It can operate over the temperature range of -30oC to +40oC and its housing is completely sealed. The TWS is adapted to weaver or Picatinny rail mounting. The overall design of the TWS prototype is based on feedbacks of users to achieve improved user-friendly (e.g. no pull-down menus and no electronic focusing) and ergonomic (e.g. locations of buttons) features.

Dual-band dual field-of-view TVWS prototype

A dual band thermal/visible weapon sight (TVWS) prototype was developed by INO in collaboration with DRDC Valcartier. The TVWS operates in the 8-12 μm infrared (IR) and 300-900 nm visible wavebands for enhanced vision capabilities in day and night operations. It is equipped with lightweight athermalized coaxial catadioptric objectives, a bolometric IR imager operating in a microscan mode providing an effective resolution of 320 x 240 pixels and a visible image intensifier of 768 x 493 pixels. The TVWS is equipped with a miniature shutter for automatic offset calibration. Real-time imaging at 30 fps is available. Both the visible and IR images can be toggled with a single touch button and displayed on an integrated color micro liquid crystal display (LCD). The TVWS also has a standard video output via a coaxial connector. An integrated wireless analog RF link can be used to send images to a remote command control. The sight has an adjustable electronic crosshair and two manual focuses from 25 m to infinity. On-board processing capabilities were added to introduce specific functionalities such as image polarity inversion (black hot/white hot) and image enhancement. This TVWS model is also very lightweight (~ 1900 grams) and compact (volume of 142 cubic inches). It offers human size target detection at 800 m and recognition at 200 m (Johnson criteria) with the IR waveband while offering the human recognition at up to 800 m with the visible waveband. The TVWS is adapted for weaver or Picatinny rail mounting.

Enhancement of YBCO microbolometer performances with regionally thinned microbridges

Silicon nitride microbridges (50x50 mm2, 0.6 mm thick), suspended over a silicon substrate, were patterned and thinned. These patterns consist of 2 to 12 windows that were thinned to approximately 0.3 mm. Microbolometers were fabricated by sputtering a YBaCuO thin film over the bridges. The experimental results showed that the regionally thinned microbridges have a lower thermal time constants t (about 1.6 ms) than that of the standard pixel configuration (2.6 ms). On the other hand, the fact that the regionally thinned microbolometers having detectivity D* values comparable to or even six times superior than that of the standard pixel showed that the decrease in response time is not penalized by loss of detection performance. The simulation results also show that as the amount of material removed is increased, the thermal time constant drops significantly while the (τ/G)1/2 ratio (where G is the thermal conductance of the pixel) only decreases slightly, suggesting that the reduced response time will not cause a significant drop in detectivity D*. The simulation results of mechanical integrity show that a specific regionally thinned microbridge design has 22 % higher stiffness than that of a standard pixel design with similar thermal properties. The fact that thick regions remained on the regionally thinned pixels (like the edges of the pixels) provide significant mechanical support to the microstructures. This confirms the validity of the regionally thinned microbridges approach.

Novel lightweight uncooled thermal weapon sight

INO in collaboration with DRDC Valcartier has been involved in the design and development of uncooled IR bolometric detector technology since the early 1990s for a broad range of military and commercial applications. From the beginning, the strategy has been to develop small-size bidimensional detector arrays and specialty linear arrays, both equipped with on-chip readout electronics. The detector arrays have been implemented in various instruments for both imaging and non-imaging applications. This paper describes two TWS1 and TWS2 prototypes of single band thermal weapon sights (TWS) making use of a novel catadioptric, i.e. refractive/reflective, optics and INOs miniature IR cameras. These cameras employ a 160x120 pixel uncooled bolometric FPA with a 52 µm pitch and NETD at 50 mK, and modular electronics consisting of three boards stacked together to fit into a 3-inch cube volume. The ultra lightweight catadioptric objective is inherently athermalized in the -30°C to +40°C range. The TWS1 is also equipped with a miniature RF link allowing bi-directional video transmission. This TWS1 weighs only 900 g and has a total volume of about 75 in3. Its power consumption is 2 W. The experimental performance showed that human detection, recognition and identification could be achieved at 800 m, 200 m, and 120 m, respectively. Construction of an improved TWS2 model is in progress. The objective is the reduction of TWS2 model weight down to 700 g, its volume down to 50 in3, replacing the RF video link with a wireless digital link, and increasing resolution to 320x240 pixels.

Study of laser reflection of infrared cameras with germanium optics

Infrared cameras are widely used in todays battlefield for surveillance purpose. Because of retroreflection, an incident laser beam entering the camera optics results in a beam reflecting back to the direction of the laser source. An IR detector positioned close to the laser source can then detect the reflected beam. This effect can reveal the location of the cameras and thus increases the risk of covert operations. In the present work, the characteristics of the retroreflection is studied. It is found that the reflection intensity is high when the incident beam enters through the middle part of the lenses while it is low and the beam is diverged when entering through the outer part of the lenses. The reflection is symmetric when the incident beam is normal to the lenses while asymmetric when it is incident with an angle to the lenses. In order to study the potential effects on retroreflection of modified camera optics, IR low index slides (ZnSe and KCl with refractive indices of 2.49 and 1.54, respectively) with different thicknesses (2mm, 4mm and 6mm) are placed in the optical system. The result shows that the focal point of the lenses is changed by the addition of the slide but the optical paths of the reflection remain unchanged. The relationship between the different slides and beam intensity is also studied.

Hadamard spectrometer for passive LWIR standoff surveillance

Based on the principle of the Integrated Optical Spectrometer (IOSPEC), a waveguide-based, longwave infrared (LWIR) dispersive spectrometer with multiple input slits for Hadamard spectroscopy was designed and built intended for passive standoff chemical agent detection in 8 to 12μm spectral range. This prototype unit equips with a three-inch input telescope providing a field-of-view of 1.2 degrees, a 16-microslit array (each slit 60 μm by 1.8 mm) module for Hadamard binary coding, a 2-mm core ZnS/ZnSe/ZnS slab waveguide with a 2 by 2 mm2 optical input and micro-machined integrated optical output condensor, a Si micro-machined blazing grating, a customized 128-pixel LWIR mercury-cadmium-telluride (MCT) LN2 cooled detector array, proprietary signal processing technique, software and electronics. According to the current configuration, it was estimated that the total system weight to be ~4 kg, spectral resolution <4cm-1 and Noise Equivalent Spectral Radiance (NESR) <10-8 Wcm-2 sr-1cm-1 in 8 to 12 μm. System design and preliminary test results of some components will be presented. Upon the arrival of the MCT detector array, the prototype unit will be further tested and its performance validated in fall of 2007.

Optomechanical design of a field-deployable thermal weapon sight

The use of uncooled infrared (IR) imaging technology in Thermal Weapon Sight (TWS) systems produces a unique tool that perfectly fulfills the all-weather, day-and-night vision demands in modern battlefields by significantly increasing the effectiveness and survivability of a dismounted soldier. The main advantage of IR imaging is that no illumination is required; therefore, observation can be accomplished in a passive mode. It is particularly well adapted for target detection even through smoke, dust, fog, haze, and other battlefield obscurants. In collaboration with the Defense Research and Development Canada (DRDC Valcartier), INO engineering team developed, produced, and tested a rugged thermal weapon sight. An infrared channel provides for human detection at 800m and recognition at 200m. Technical system requirements included very low overall weight as well as the need to be field-deployable and user-friendly in harsh conditions. This paper describes the optomechanical design and focuses on the catadioptric-based system integration. The system requirements forced the optomechanical engineers to minimize weight while maintaining a sufficient level of rigidity in order to keep the tight optical tolerances. The optical systems main features are: a precision manual focus, a watertight vibration insulated front lens, a bolometer and two gold coated aluminum mirrors. Finite element analyses using ANSYS were performed to validate the subsystems performance. Some of the finite element computations were validated using different laboratory setups.