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Staring Array
A staring array, also known as staring-plane array or focal-plane array (FPA), is an image sensor consisting of an array (typically rectangular) of light-sensing pixels at the focal plane of a lens. FPAs are used most commonly for imaging purposes (e.g. taking pictures or video imagery), but can also be used for non-imaging purposes such as spectrometry, LIDAR, and wave-front sensing. In radio astronomy, the FPA is at the focus of a radio telescope. At optical and infrared wavelengths, it can refer to a variety of imaging device types, but in common usage it refers to two-dimensional devices that are sensitive in the infrared spectrum. Devices sensitive in other spectra are usually referred to by other terms, such as CCD (charge-coupled device) and CMOS image sensor in the visible spectrum. FPAs operate by detecting photons at particular wavelengths and then generating an electrical charge, voltage, or resistance in relation to the number of photons detected at each pixel. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Image Sensor
An image sensor or imager is a sensor that detects and conveys information used to form an image. It does so by converting the variable attenuation of light waves (as they refraction, pass through or reflection (physics), reflect off objects) into signal (electrical engineering), signals, small bursts of electric current, current that convey the information. The waves can be light or other electromagnetic radiation. Image sensors are used in electronics, electronic imaging devices of both analogue electronics, analog and digital electronics, digital types, which include digital cameras, camera modules, camera phones, optical mouse devices, medical imaging equipment, night vision equipment such as thermography, thermal imaging devices, radar, sonar, and others. As technological change, technology changes, electronic and digital imaging tends to replace chemical and analog imaging. The two main types of electronic image sensors are the charge-coupled device (CCD) and the active-pixel s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Indium Antimonide
Indium antimonide (InSb) is a crystalline compound made from the elements indium (In) and antimony (Sb). It is a narrow- gap semiconductor material from the III- V group used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, and in infrared astronomy. Indium antimonide detectors are sensitive to infrared wavelengths between 1 and 5 μm. Indium antimonide was a very common detector in the old, single-detector mechanically scanned thermal imaging systems. Another application is as a terahertz radiation source as it is a strong photo-Dember emitter. History The intermetallic compound was first reported by Liu and Peretti in 1951, who gave its homogeneity range, structure type, and lattice constant. Polycrystalline ingots of InSb were prepared by Heinrich Welker in 1952, although they were not very pure by today's semiconductor standards. Welker was interested in systematically studying the semiconducting p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Air-to-air Missile
An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying another aircraft (including unmanned aircraft such as cruise missiles). AAMs are typically powered by one or more rocket motors, usually solid-fuel rocket, solid fueled but sometimes liquid-fuel rocket, liquid fueled. Ramjet engines, as used on the Meteor (missile), Meteor, are emerging as propulsion that will enable future medium- to long-range missiles to maintain higher average speed across their engagement envelope. Air-to-air missiles are broadly put in two groups. Those designed to engage opposing aircraft at ranges of around 30 km to 40 km maximum are known as short-range or "within visual range" missiles (SRAAMs or WVRAAMs) and are sometimes called "dogfight" missiles because they are designed to optimize their agility rather than range. Most use infrared guidance and are called heat-seeking missiles. In contrast, medium- or long-range missiles (MRAAMs or LRAAMs), which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Field-programmable Gate Array
A field-programmable gate array (FPGA) is a type of configurable integrated circuit that can be repeatedly programmed after manufacturing. FPGAs are a subset of logic devices referred to as programmable logic devices (PLDs). They consist of an array of programmable logic device, programmable logic block, logic blocks with a connecting grid, that can be configured "in the field" to interconnect with other logic blocks to perform various digital functions. FPGAs are often used in limited (low) quantity production of custom-made products, and in research and development, where the higher cost of individual FPGAs is not as important, and where creating and manufacturing a custom circuit would not be feasible. Other applications for FPGAs include the telecommunications, automotive, aerospace, and industrial sectors, which benefit from their flexibility, high signal processing speed, and parallel processing abilities. A FPGA configuration is generally written using a hardware descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Digital Signal Processor
A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on metal–oxide–semiconductor (MOS) integrated circuit chips. They are widely used in audio signal processing, telecommunications, digital image processing, radar, sonar and speech recognition systems, and in common consumer electronic devices such as mobile phones, disk drives and high-definition television (HDTV) products. The goal of a DSP is usually to measure, filter or compress continuous real-world analog signals. Most general-purpose microprocessors can also execute digital signal processing algorithms successfully, but may not be able to keep up with such processing continuously in real-time. Also, dedicated DSPs usually have better power efficiency, thus they are more suitable in portable devices such as mobile phones because of power consumption constraints. DSPs often use special m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Photo Response Non-uniformity
Photo response non-uniformity, pixel response non-uniformity, or PRNU, is a form of fixed-pattern noise related to digital image sensors, as used in cameras and optical instruments. Both CCD and CMOS sensors are two-dimensional arrays of photosensitive cells, each broadly corresponding to an image pixel. Due to the non-uniformity of image sensors, each cell responds with a different voltage level when illuminated with a uniform light source, and this leads to luminance inaccuracy at the pixel level. High-end and metrology camera vendors tend to characterise this non-uniformity during instrument manufacture. The sensor is illuminated with a standardized light source and a two-dimensional table of correction factors is generated. This table is either carried in camera non-volatile memory and dynamically applied to the image on each capture, or ships with the camera to be applied by an external image processing and correcting pipeline. See also * Color balance * Color correction * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Thermo-electric Cooler
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a Solid-state physics, solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC) and occasionally a thermoelectric battery. It can be used either for heating or for cooling, although in practice the main application is cooling since heating can be achieved with simpler devices (with Joule heating). It can also be used as a temperature controller that either heats or cools. This technology is far less commonly applied to refrigeration than vapor-compression refrigeration is. The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Liquid Nitrogen
Liquid nitrogen (LN2) is nitrogen in a liquid state at cryogenics, low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose viscosity is about one-tenth that of acetone (i.e. roughly one-thirtieth that of water at room temperature). Liquid nitrogen is widely used as a coolant. Physical properties The diatomic character of the N2 molecule is retained after liquefaction. The weak van der Waals interaction between the N2 molecules results in little interatomic attraction. This is the cause of nitrogen's unusually low boiling point. The temperature of liquid nitrogen can readily be reduced to its freezing point by placing it in a vacuum chamber pumped by a vacuum pump. Liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in an insulating layer of nitrogen gas bubbles. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Johnson–Nyquist Noise
Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the voltage or current noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage. Thermal noise is present in all electrical circuits, and in sensitive electronic equipment (such as radio receivers) can drown out weak signals, and can be the limiting factor on sensitivity of electrical measuring instruments. Thermal noise is proportional to absolute temperature, so some sensitive electronic equipment such as radio telescope receivers are cooled to cryogenic temperatures to improve their signal-to-noise ratio. The generic, statistical physical derivation of this noise is called the fluctuation-dissipation theorem, where generalized impedance or generalized susceptibility is used to characterize the medium. Thermal noise in an ideal resistor is approximately white, meaning that it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Microbolometer
A microbolometer is a specific type of bolometer used as a detector in a thermal camera. Infrared radiation with wavelengths between 7.5–14 μm strikes the detector material, heating it, and thus changing its electrical resistance. This resistance change is measured and processed into temperatures which can be used to create an image. Unlike other types of infrared detecting equipment, microbolometers do not require cooling. Theory of construction A microbolometer is an uncooled thermal sensor. High resolution thermal sensors require exotic and expensive cooling methods including stirling cycle coolers and liquid nitrogen coolers. These methods of cooling high resolution thermal imagers are expensive to operate and unwieldy to move. Also, high resolution thermal imagers require a cool down time in excess of 10 minutes before being usable. A microbolometer consists of an array of pixels, each pixel being made up of several layers. The cross-sectional diagram shown in Figure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a universal definition of "cryogenics" and "cryogenic" by accepting a threshold of to distinguish these terms from conventional refrigeration. This is a logical dividing line, since the normal boiling points of the so-called permanent gases (such as helium, hydrogen, neon, nitrogen, oxygen, and normal air) lie below 120 K, while the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above 120 K. Discovery of superconducting materials with critical temperatures significantly above the boiling point of nitrogen has provided new interest in reliable, low-cost methods of producing high-temperature cryogenic refrigeration. The term "high temperature cryogenic" describes temperatures ranging from above the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Readout Integrated Circuits
A readout integrated circuit (ROIC) is an integrated circuit (IC) specifically used for reading detectors of a particular type. They are compatible with different types of detectors such as infrared and ultraviolet. The primary purpose for ROICs is to accumulate the photocurrent from each pixel and then transfer the resultant signal onto output taps for readout. Conventional ROIC technology stores the signal charge at each pixel and then routes the signal onto output taps for readout. This requires storing large signal charge at each pixel site and maintaining signal-to-noise ratio (or dynamic range) as the signal is read out and digitized. A ROIC has high-speed analog outputs to transmit pixel data outside of the integrated circuit. If digital outputs are implemented, the IC is referred to as a Digital Readout Integrated Circuit (DROIC). A digital readout integrated circuit (DROIC) is a class of ROIC that uses on-chip analog-to-digital conversion In electronics, an an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |