Infrared Sensor Array Research Articles

Microlens for Uncooled Infrared Array Sensor

This paper describes the design and fabrication of a microlens for the sensitivity improvement of uncooled infrared array sensors. We improved the sensitivity by collecting infrared rays to detectors. The microlens is made of silicon, which is a typical substrate for MEMS technology. We fabricated it by photolithography technology using a gray scale mask and an etch-back process by selectivity-controlled dry etching. This process enables us to fabricate a 43-µm-high silicon microlens from only a 2- to 3-µm-high photoresist structure. To confirm the usefulness of the microlens, we developed a small infrared array sensor with microlens. The results show that the sensitivity improvement with the microlens is 4.2 times. Microlens is one promising technology for sensitivity improvement.

Elderly-falling detection using distributed direction-sensitive pyroelectric infrared sensor arrays

This paper presents a new distributed direction-sensitive infrared sensing approach for fall detection in elderly healthcare applications. Pyroelectric infrared (PIR) sensors are employed in sensing human activities. For capturing the characteristics of human normal and abnormal activities, three modules of a direction-sensitive PIR sensor are organized using a distributed sensing structure. The advantage of using the distributed sensing paradigm is that the synergistic motion patterns of head, upper-limb and lower-limb can be efficiently encoded and thus the more discriminative features can be captured. This is the new consideration of using PIR sensors in building a full detection system. In addition, a two-layer hidden Markov model is developed for recognizing a fall event based on the multidimensional signals of the distributed infrared sensing system. Experimental studies are conducted to validate the proposed method.

Real-Time Signal Processing Method for Infrared Sensor Arrays

Infrared sensor arrays is a new type of apperceiving system of robots, which are made up of large-area and flexible sensors with data processing capabilities. In order to meet the requirement of real-time obstacle avoidance, sensors which can be covered on the surface of robots were designed to apperceive the environment and provide the environmental information by the infrared sensors and the controlling circuit on them. To get rid of the environmental disturbance to the infrared sensors, and to meet the requirement of system precision, real time and stability, a kind of reconfigurable architecture based on DSP+FPGA was designed and a kind of spectrum analyzing method based on FFT (Fast Fourier Transform) was used. Tests of the system with different color papers as the measured subjects showed that the output of sensor arrays had low sensitivity.

45.2: Distinguished Paper: Novel LCD Display with a Sensible Backlight

AbstractIn this paper, we describe a novel multi‐touch LCD display architecture with hover sensing capability based on infrared sensor array. The proposed display architecture has an advantage over existing multi‐touch LCD displays in that it maintains a slim form‐factor of LCD displays without loss of a display quality while it is possible to sense multiple touches and hovers simultaneously.

Low-cost approach for integrated long-wavelength infrared sensor arrays

A new low-cost process for mid resolution FIR-Arrays for thermal imaging in the LWIR range (8- 14 μm) has been developed. Integrated array devices with 1k and 5k pixel array size have been designed and manufactured using this process which is fully compatible with semiconductor production. The devices are suitable to support detection of humans e.g. in security and automotive safety applications.

Improved Infrared Position Sensitive Detector

This paper presents an improved infrared position sensitive detector (IRPSD) that is operated in a vacuum condition. IRPSD is a two-dimensional infrared array sensor with two thermometers in each pixel. One thermometer is serially connected in a row and the other is serially connected in a column. The serial connection of these thermometers produces the sum of signals from all pixels in each row and column. With this array architecture, IRPSD extracts specific information without digital image processing. In this study, we developed an IRPSD that uses thermopiles as thermometers. To achieve high responsivity and large signal-to-noise ratio, we optimized the pattern layout of the pixel, considering thermal conductance and Johnson noise. As a result, responsivity of about 170 V/W was obtained.

3-D Modeling of Pyroelectric Sensor Arrays Part II: Modulation Transfer Function

The modulation transfer function (MTF) for a pyroelectric infrared sensor array is determined from a finite-element simulation. Consideration of the full thermoelectromechanical coupling and use of a 3-D sensor model result in a good agreement between calculated and measured data.

Radiation Effects in InGaAs and Microbolometer Infrared Sensor Arrays for Space Applications

Cobalt60, 60 MeV proton and heavy ion tests have been performed on InGaAs and amorphous silicon microbolometer arrays with CMOS readout circuits. The readout circuits showed latch-up at threshold LETs~14 MeV/mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , but the total dose and displacement damage effects were negligible for low earth orbit conditions. Effects in a microbolometer array tested, for use in Mercury orbit, to 100 krd(Si) and 3.2 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> 60 MeV p/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> showed acceptable performance, though there was a significant increase in power consumption for the CMOS readout circuit when biased during cobalt60 irradiation.

Pyroelectric ceramics and thin films for applications in uncooled infra-red sensor arrays

Pyroelectric infra-red detector arrays provide an attractive solution to the problem of collecting spatial information in the far IR. They are only sensitive to changes in the IR flux and are well suited to sensing movements of people. The applications of low cost arrays with limited (a few hundred) elements for people sensing and radiometry will be illustrated. The performances of uncooled pyroelectric arrays are ultimately driven by the materials used. For this reason, continuous improvements in materials technology and figures-of-merit (FoM) are important. The performance of dense, bulk pyroelectric ceramics has not increased for several years, but nevertheless it is possible to obtain significant improvements in performance through the use of tape-cast, functionally gradient materials (FGMs) in which controlled porosity is used to control the permittivity and heat capacity of the material. A model for the performance of such a material will be presented, and compared with experimentally determined properties of FGMs based on a modified-PZT pyroelectric ceramic. The use of ferroelectric thin films is offering considerable potential for low cost and high performance. It will be shown that the introduction of controlled amounts of porosity can have a significant positive effect on the relevant pyroelectric FoM.

Advanced Protection for Vulnerable Road Users: A Case Study

There is increasing international interest in collision avoidance and more recently in safety systems for ‘vulnerable road users’ (VRUs). Pedestrians and cyclists (VRUs) account for approximately one in four of all road deaths in the European Union. The aim of the ‘advanced protection for vulnerable road users’ (APVRU) project was to develop a sensor system capable of detecting VRUs, distinguishing them from the road environment, tracking their position, and predicting potential impacts with the vehicle. The proposed fusion of sensor data from multiple, short-range, high-accuracy, pulse radar units and a low-resolution passive infrared sensor array served to eliminate the majority of clutter by negating false triangulation combinations, while ensuring that only thermally distinct, moving targets are considered. The intention is that a derivative of the sensor system may eventually provide the technological link between VRU detection and a driver warning, collision avoidance, and/or the activation of a safety system on the vehicle (external airbags). The performance of this preliminary, ‘proof-of-concept’ APVRU system was demonstrated during real-world accident scenarios, impacting with an anthropometric dummy, at speeds, limited by current hardware, up to 25 km/h (15.5 mile/h).

High-luminosity multipass cell for infrared imaging spectroscopy

An original imaging multipass cell for infrared spectroscopy has been designed and built. The cell design is aimed at overcoming intrinsic sensitivity limitations associated with the low specific spectral radiance power of blackbody sources. Owing to the implemented low f number, the detector collects a large amount of the energy emitted over a wide angle by a blackbody source. In addition, the adopted optical configuration allows maintenance of the same spatial distribution of the radiance pattern at the cell entrance and exit (imaging capability) within an aperture area of several square millimeters. This feature allows the use of uncollimated blackbody-type emitter arrays and infrared sensor arrays coupled with linear, spectrally variable filters, and performance of spectroscopic measurements of infrared absorption for low concentrated gases detection. In the present design the cell has an f number of about 2, and the optical path is ten times larger than the cell length.

Exposure to undernutrition in fetal life determines fat distribution, locomotor activity and food intake in ageing rats

To assess the long-term impact of undernutrition during specific periods of fetal life, upon central adiposity, control of feeding behaviour and locomotor activity. Pregnant rats were fed a control or low-protein (LP) diet, targeted to early (LPE), mid (LPM) or late (LPL) pregnancy or throughout gestation (LPA). The offspring were studied at 9 and 18 months of age. Adiposity was assessed by measuring weight of abdominal fat depots relative to body weight. Locomotor activity was assessed using an infrared sensor array system in both light and dark conditions. Hypothalamic expression of mRNA for galanin and the galanin 2 receptor (Gal2R) was determined using real-time PCR. At 9 months, male rats exposed to LP in utero had less fat in the gonadal depot, but were of similar body weight to controls. By 18 months, the males of groups LPA and LPM had more abdominal and less subcutaneous fat. Females deposited more fat centrally than males between 9 and 18 months of age, and this was more marked in groups LPA and LPL. Food intake was greater in LPM males. Among females hypophagia was noted in groups LPA and LPL. Expression of galanin and Gal2R were unaffected by maternal diet. Total locomotor activity was reduced in LPE males and all LP females in the light but not in the dark. Locomotor activity and feeding behaviour in aged rats are subject to prenatal programming influences. Fetal undernutrition does not programme obesity in rats without postnatal dietary challenge.

Design, Sensing and Control of a Robotic Prosthetic Eye for Natural Eye Movement

Loss of an eye is a tragedy for a person, who may suffer psychologically and physically. This paper is concerned with the design, sensing and control of a robotic prosthetic eye that moves horizontally in synchronization with the movement of the natural eye. Two generations of robotic prosthetic eye models have been developed. The first generation model uses an external infrared sensor array mounted on the frame of a pair of eyeglasses to detect the natural eye movement and to feed the control system to drive the artificial eye to move with the natural eye. The second generation model removes the impractical usage of the eye glass frame and uses the human brain EOG (electro‐ocular‐graph) signal picked up by electrodes placed on the sides of a person′s temple to carry out the same eye movement detection and control tasks as mentioned above. Theoretical issues on sensor failure detection and recovery, and signal processing techniques used in sensor data fusion, are studied using statistical methods and artificial neural network based techniques. In addition, practical control system design and implementation using micro‐controllers are studied and implemented to carry out the natural eye movement detection and artificial robotic eye control tasks. Simulation and experimental studies are performed, and the results are included to demonstrate the effectiveness of the research project reported in this paper.

Design, Sensing and Control of a Robotic Prosthetic Eye for Natural Eye Movement

Loss of an eye is a tragedy for a person, who may suffer psychologically and physically. This paper is concerned with the design, sensing and control of a robotic prosthetic eye that moves horizontally in synchronization with the movement of the natural eye. Two generations of robotic prosthetic eye models have been developed. The first generation model uses an external infrared sensor array mounted on the frame of a pair of eyeglasses to detect the natural eye movement and to feed the control system to drive the artificial eye to move with the natural eye. The second generation model removes the impractical usage of the eye glass frame and uses the human brain EOG (electro-ocular-graph) signal picked up by electrodes placed on the sides of a person's temple to carry out the same eye movement detection and control tasks as mentioned above. Theoretical issues on sensor failure detection and recovery, and signal processing techniques used in sensor data fusion, are studied using statistical methods and artificial neural network based techniques. In addition, practical control system design and implementation using micro-controllers are studied and implemented to carry out the natural eye movement detection and artificial robotic eye control tasks. Simulation and experimental studies are performed, and the results are included to demonstrate the effectiveness of the research project reported in this paper.

Fabrication and characterization of integrated uncooled infrared sensor arrays using a-Si thin-film transistors as active elements

In this paper, we report on the first realization and characterization of monolithic uncooled 8/spl times/8 infrared sensor arrays, based on amorphous silicon thin-film transistors (a-Si TFT). The a-Si TFT is employed as the active element of the sensor, because it possesses a high temperature coefficient of its drain current of 1.5%-6.5% K/sup -1/ at room temperature. The improved porous silicon micromachining techniques described here enable the integration of the a-Si TFT-based sensor array with the MOS readout circuitry. The sacrificial material of porous silicon is prepared in the first step. It is then well protected all the time during the fabrication of MOSFETs and sensors before being released. Optical tests are performed to characterize the sensor. The influences of the gate voltage of a-Si TFT (V/sub g/) and the voltage source of the circuitry (V/sub dd/) on the sensor performance are investigated. The measurement indicates that the sensor has a maximum detectivity of 8.67/spl times/10/sup 8/ cm Hz/sup 1/2/W/sup -1/ at V/sub g/=-15 V, V/sub dd/=-12 V and a chopping frequency of 30 Hz. The noise equivalent power (NEP) of the sensor is less than 10/sup -10/ W Hz/sup -1/2/, and the noise equivalent temperature difference (NETD) is as low as 67 mK at room temperature, which compares well with the recent results of some uncooled IR sensors developed by other groups. Primary imaging tests indicate that the 8/spl times/8 sensor array has potential for high performance imaging applications.

Technology demonstration by the BIRD-mission

Small satellites have to meet a big challenge: to answer high-performance requirements by means of small equipment and especially of small budgets. Out of all aspects the cost aspect is one of the most important driver for small satellite missions. To keep the costs within the low-budget frame (in comparison to big missions) the demonstration of new and not space-qualified technologies for the spacecraft is one key point in fulfilling high-performance mission requirements. Taking this into account the German DLR micro-satellite mission BIRD (Bi-spectral Infra-Red Detection) has to demonstrate a high-performance capability of spacecraft bus by using and testing new technologies basing on a mixed parts and components qualification level. The basic approach for accomplishing high-performance capability for scientific mission objectives under low-budget constraints is characterized by using • state-of-the-art technologies, • a mixed strategy in the definition of the quality level of the EEE parts and components, • a tailored quality management system according to ISO 9000 and ECSS, • a risk management system, • extensive redundancy strategies, • extensive tests especially on system level, • large designs margins (over-design), • robust design principles. The BIRD-mission is dedicated to the remote sensing of hot spot events like vegetation fires, coal seam fires or active volcanoes from space and to the space demonstration of new technologies. For these objectives a lot of new small satellite technologies and a new generation of cooled infrared array sensors suitable for small satellite missions are developed to fulfil the high scientific requirements of the mission. Some basic features of the BIRD spacecraft bus are • compact micro satellite structure with high mechanical stability and stiffness, • envelope qualification for several launchers, • cubic shape in launch configuration with dimensions of about 620 × 620 × 550 mm 3 and variable launcher interface, • mass ratio bus:payload = 62 kg:30 kg, • high peak power of 200 W at 10–20 min, and average power 60 W, • advanced thermal control system with radiators, heat pipes, MLI, temperature sensors and contingency heaters, • new developed high-performance spacecraft bus computer with integrated latch-up protection and error detection and correction system, • three-axis stabilization of the spacecraft by an attitude control system in state space representation, • integrating the payload platform with its structure, thermal and power requirements, • onboard determination of the spacecraft position and velocity by the onboard navigation system basing on receiving and onboard processing of GPS data, • S-band communication with high bit rate (2.2 Mbps) and low bit rate. The total mass of the complete spacecraft is 92 kg. BIRD shall demonstrate the limits and the advantages of using new developed components, methods, algorithms and technologies. The satellite was launched with the Indian PSLV-C3 from Shar on 22nd October 2001 into an Sun-synchronous circular orbit of an altitude of about 568 km. (The paper describes the new developed technologies like onboard navigation system, the high-performance failure tolerant spacecraft computer, the precision reaction wheels, the star sensor, the attitude control system, the onboard classification experiment and the results and flight experience up to now.)

Micromachined infrared bolometers on flexible polyimide substrates

Micromachined infrared sensor arrays have been fabricated on flexible polyimide substrates using a silicon wafer carrier during the fabrication process. These flexible polyimide substrates containing the micromachined infrared sensors were removed from the silicon wafer at the end of fabrication. The fabrication technique utilized surface micromachining of a bridge structure to form the thermal infrared (IR) sensors on flexible substrates. Semiconducting yttrium barium copper oxide YBCO was used as the radiation sensitive material. 1 × 10 sensor arrays of microbolometers were micromachined using a photo-definable polyimide sacrificial layer and characterized before and after removal of the substrate from the Si wafer carrier. The flexible infrared microsensors showed similar performance to microbolometers fabricated on rigid silicon substrates. The YBCO thermistors exhibited a temperature coefficient of resistance (TCR) of ∼−3.4% K −1 near room temperature. Responsivity and detectivity values as high as 6.1 × 10 4 V/W and 1.2 × 10 8 cm Hz 1/2/W, respectively, were measured in vacuum for a 40 μm × 40 μm microbolometer with 1 μA bias. The lowest observed noise equivalent power was 4.1 × 10 −11 W/Hz 1/2 while the lowest thermal time constant was 5.7 ms.

Method for expanding the dynamic range of the readout integration circuits for uncooled microbolometer sensors

A simple and robust method for expanding the dynamic range of the readout circuits for uncooled microbolometer infrared sensor arrays is presented. The proposed method allows a reduction in the number of bits required for microbolometer nonuniformity compensation, significantly reducing the complexity of the pre-integration compensation circuity.

A Ray-Tracing Approach for Simulating Recognition Abilities of Active Infrared Sensor Arrays

The construction and setup of sensors or sensor arrays determines their maximum resolution and recognition abilities. Therefore, the analysis of certain setups is an important and mandatory task during the design process of a new sensor system. This paper deals with the simulation and evaluation of the recognition abilities of active infrared sensors for autonomous systems. Additionally, the simulation method as well as the results provide useful information for other applications, where infrared sensors are used. The simulation method is based on a Monte Carlo algorithm, which uses ray tracing to calculate the impulse response of the optical channel consisting of the sending and receiving components and the environment. In order to allow a fast simulation of several configurations, an efficient and flexible computation is realized. This means that all rays contribute maximally to the final result, and different sensor characteristics can easily be calculated. Extensive experiments are carried out, and the results show different evaluation options.

US company launches first MEMS‐based IR detector array

Describes the world's first uncooled infrared array sensor based on micro electro‐mechanical systems technology. Each pixel comprises a cantilever which bends as it warms up. The system measures the capacitance between each cantilever and a metal substrate.