A quantum well infrared photodetector QWIP , is an infrared photodetector made from semiconductor materials which contain one or more quantum well s. These can be integrated together with electronics and optics to make infrared camera s for thermography . A very common well material is gallium arsenide , used with barrier material aluminium gallium arsenide . There are several companies world wide manufacturing infrared systems which use QWIPs. It is also considered a game changing technology for such applications as air to air missiles, where it can detect objects which are well outside the visual range of the pilot. External links http qwip.jpl.nasa.gov NASA qwip research http www.armyscienceconference.com manuscripts N NO 001.pdf Corrogated QWIP for megapixel sensors Twenty Seventh Army Science Conference Category Optical devices Category Image sensors Category Infrared imaging optics stub de Quantentopf Infrarot Photodetektor fr QWIP ... more details
Photosensors or photodetectors are sensors of light or other Electromagnetic radiation electromagnetic energy. There are several varieties ref cite journal doi 10.1063 1.2884264 title Study of residual background carriers in midinfrared InAs GaSb superlattices for uncooled detector operation year 2008 last1 Haugan first1 H. J. first2 S. first3 F. first4 B. first5 G. J. first6 W. C. journal Applied Physics Letters volume 92 pages 071102 bibcode 2008ApPhL..92g1102H ref Active pixel sensor s are image sensors consisting of an integrated circuit that contains an array of pixel sensors, each pixel containing a both a light sensor and an active amplifier. There are many types of active pixel sensors including the CMOS APS commonly used in cell phone cameras, web cameras, and some DSLRs. An image sensor produced by a CMOS process is also known as a CMOS sensor, and has emerged as an alternative to Charge coupled device CCD sensors. Charge coupled device s CCD , which are used to record images in astronomy , digital photography , and digital cinematography . Before the 1990s, photographic plate s were most common in astronomy. The next generation of astronomical instruments, such as the Astro E2 , include cryogenic detector s. In experimental particle physics , a particle detector is a device used to track and identify elementary particles. Chemical detectors, such as photographic plate s, in which a silver halide molecule is split into an atom of metallic silver and a halogen atom. The photographic developer causes adjacent molecules to split similarly. Cryogenic detectors are sufficiently sensitive to measure the energy of single x ray, visible and infrared photons. ref cite book author Enss, Christian Editor title Cryogenic Particle Detection publisher Springer, Topics in applied physics 99 year 2005 isbn 3 540 20113 0 ref LED s reverse biased to act as photodiodes. See LEDs as Photodiode Light Sensors . optics Optical detectors, which are mostly quantum devices in which ... more details
BLP unsourced date April 2012 Senior Research Scientist and Group Supervisor at NASA s Jet Propulsion Laboratory. He works primarily in Quantum well infrared photodetector Quantum Well Infrared Photo Detecting . He is also a Board Member of QWIP Technologies LLC. QWIP technology Quantum Well Infrared Photodetector QWIP is a digital sensor that is being utilised in numerous ways, not only by scientists but also by astronomers, meteorologists, firemen, and doctors. Among other things, QWIP cameras are used to detect smog, monitor volcanoes, detect both skin and breast cancer at many institutions, including the University of Southern California s Children s Hospital and Weill Cornell Medical College of Cornell University , and to find hot spots in forest fires. This technology will revolutionize the way we develop new remote sensing instruments, said team leader Dr. Sarath Gunapala and added As a result of all our research work in last decade, QWIP technology has culminated as the most favorable highly sensitive multi band large format focal plane array technology in long wavelength infrared region . Dr. Gunapala has introduced to the world, the 640x512 PixZls Long Wavelength Infrared LWIR Quantum Dot Infrared Photodetector QDIP Focal Plane Array Camera . He currently holds over 17 patents, most relating to his work with QWIP and QSIP Quantum Structured Infrared Photodetector . DEFAULTSORT Gunapala, Sarath Category Year of birth missing living people Category Living people Category NASA personnel ... more details
Optical sorting is a process of visually sorting a product though the use of a photodetector light sensor , camera , ref http www.woodheadpublishing.com en book.aspx?bookID 614&printer yes Detecting foreign bodies in food ref or the human eye . ref Image Processing for the Food Industry , E. R. Davis World Scientific Publishing Co. Pte. Ltd. London, 2000 ref In its simplest operation, a machine will simply see how much light is reflected off the object using a simple photodetector such as a photoresistor and accept or reject the item depending on how reflective it is light or dark . More sophisticated systems use image processing to discriminate the colors of the object, often via a controlled spectrum of light, even beyond the visible spectrum into the IR and UV range. Shape detection is an evolving ability. The common method of removal is jets of compressed air, but others exist. The term optical sorting also includes manual seeing and manipulating processes. See also Colour sorter Further reading reflist optics stub Category Optics ... more details
Responsivity measures the input output gain of a detector system. In the specific case of a photodetector , responsivity measures the electrical output per optical input. The responsivity of a photodetector is usually expressed in units of either ampere s or volt s per watt of incident radiant flux radiant power . For a system that responds linear ly to its input, there is a unique responsivity. For nonlinear system s, the responsivity is the local slope derivative . Many common photodetectors respond linearly as a function of the incident power. Responsivity is a function of the wavelength of the incident Electromagnetic radiation radiation and of the sensor properties, such as the bandgap of the material of which the photodetector is made. One simple expression for the responsivity R of a photodetector in which an optical signal is converted into an electrical current known as a photocurrent is math R eta frac q hf approx eta frac lambda mu m 1.23985 mu m times W A math where math eta math is the quantum efficiency the conversion efficiency of photons to electrons of the detector for a given wavelength, math q math is the electron charge , math f math is the frequency of the optical signal, and math h math is Planck s constant . ref cite book title Multielement Detection Systems for Spectrochemical Analysis author Kenneth W. Busch, Marianna A. Busch publisher Wiley Interscience year 1990 isbn 0 471 81974 3 url http books.google.com books?id 9H0W1J Rku4C&pg PA371&dq responsivity&as brr 0&ei T4AdR8y4MaL6pwKkvZER&sig Y eF UkViCv9V7XkMViMRZOSlz4 ref This expression is also given in terms of math lambda math , the wavelength of the optical signal, and has units of amperes per watt A W . The term responsivity is also used to summarize input output relationship in non electrical systems. For example, a neuroscientist may measure how neurons in the visual pathway respond to light. In this case, responsivity summarizes the change in the neural response per unit signal strength ... more details
HEB may refer to H E B , a supermarket chain named for founder Howard E. Butt Hindu Endowments Board of Singapore High Energy Biscuits The HEB tri city hub of the cities of Hurst, Texas Hurst , Euless, Texas Euless , and Bedford, Texas Bedford in the northeastern portion of Tarrant County in North Texas , including Hurst Euless Bedford Independent School District HEB ISD , a name for the school district centered on the area Bolometer Hot electron bolometer Hot electron bolometer , a type of photodetector disambig Category Initialisms Long comment to avoid being listed on short pages de HEB eo HEB it HEB ... more details
Photoreceptor can refer to In anatomy cell biology Photoreceptor cell a photosensitive cell in the retina of vertebrate eyes Simple eyes in arthropods Ocellus , photoreceptor organ simple eye of invertebrates often composed of a few sensory cells and a single lens Eyespot apparatus microbial photoreceptor the photoreceptor organelle of a unicellular organism that allows for phototaxis In biochemistry Photoreceptor protein a chromoprotein that responds to being exposed to a certain wavelength of light by initiating a signal transduction cascade Photopigment an unstable pigment that undergoes a physical or chemical change upon absorbing a particular wavelength of light also see Photosynthetic pigment molecules involved in transducing light into chemical energy In technology Photodetector or photosensor a device that detects light by capturing photons Electronic Photoreceptor Sensor that converts solar energy into electric energy disamb cs Fotoreceptor de Fotorezeptor fr Photor cepteur ... more details
An opto electronic oscillator OEO is an optoelectronic Electric circuit circuit that produces repetitive electronic sine wave and or modulated optical continuous wave signals. An opto electronic oscillator is based on converting the continuous light energy from a pump laser to radio frequency RF and microwave signals. The OEO is characterized by having very high quality factor Q and Stability mathematics stability , as well as other functional characteristics that are not readily achieved with electronic oscillator s. Its unique behavior results from the use of electro optical E O and photonic components, which are generally characterized with high efficiency, high speed, and low Dispersion optics dispersion in the microwave frequency regime. Operation Most OEOs utilize the transmission characteristics of a modulator together with a fiber optic delay line to convert light energy into stable, Spectral purity spectrally pure RF microwave reference signals. Light from a laser is introduced into an E O modulator, the output of which is passed through a long optical fiber and detected with a photodetector . The output of the photodetector is Amplifier amplified and filtered and fed back to the electric port of the modulator. This configuration supports self sustained oscillations, at a frequency determined by the fiber delay length, the bias setting of the modulator, and the Bandpass filter band pass characteristics of the filter. It also provides for both electric and optical outputs. The conditions for self sustained oscillations include coherent addition of partial waves each way around the loop and a loop gain exceeding losses for the circulating waves in the loop. The first condition implies that all signals that differ in phase waves phase by some multiple of 2 from the fundamental signal may be sustained. Thus the oscillation frequency is limited only by the characteristic frequency response of the modulator and the setting of the filter, which eliminates all oth ... more details
about the optoelectronic component the optical component Optical switch The slotted optical switch , sometimes known as opto switch or optical switch but not to be confused with the optical component, is a device comprising a photoemitter e.g. LED and a photodetector e.g. photodiode mounted in a single package so that the photoemitter normally illuminates the photodetector, but an opaque object can be inserted in a slot between them so as to break the beam. Associated Electronic circuit circuit ry is provided which changes state when the beam is interrupted. For example, the carriage of a computer printer may be fitted with a projection which interrupts the beam of a slotted switch when it reaches the end of its travel, causing circuitry to react appropriately. Another application of the slotted switch is in the type of Mechanical mouse computer mouse with a rotating ball. The ball measures distances moved by rotating orthogonal shafts which drive chopper wheels turning in the slots of slotted switches. ref http books.google.com books?id Qq0CVfcAktUC&pg PA132&dq mouse opto switch&hl en&ei V9uZTM DB42OjAeLo1w&sa X&oi book result&ct result&resnum 4&ved 0CDkQ6AEwAw v onepage&q mouse 20opto 20switch&f false 123 robotics experiments for the evil genius By Michael Predko, Myke Predko description of wheeled mouse operation ref This device uses the same basic components as an opto coupler , but is operated by manipulating the light path instead of the photoemitter input. Illustrations and data on slotted optical switches are to be found in catalogues and manufacturers data sheets. ref http www.optekinc.com datasheets OPB610 611 620 621.PDF Datasheet of typical optical switch ref References reflist Category Optoelectronics electronics stub ... more details
This article is intended for those who are interested in the theoretical description of quantum process of photodetection. Readers who are interested in the applications of photodetection processes may want to read photodetector . In his historic paper, ref R. J. Glauber, Phys. Rev. 130, 2529 1963 . ref entitled The Quantum Theory of Optical Coherence, Roy J. Glauber set a solid foundation for the quantum electronics quantum optics enterprise. The experimental development of the optical maser and later laser at that time had made the classical concept of Coherence physics optical coherence inadequate. Glauber started from the quantum theory of light detection by considering the process of photoionization in which a photodetector is triggered by an ionizing absorption of a photon. In the quantum theory of radiation, the electric field operator in the Coulomb gauge may be written as the sum of positive and negative frequency parts math E mathbf r , t E mathbf r , t E mathbf r , t math where math E mathbf r , t E mathbf r , t dagger math One may expand math E mathbf r , t math in terms of the normal modes as follows math E mathbf r , t i sum j frac hbar omega j 2 1 2 hat a j mathbf varepsilon j e i mathbf k j cdot mathbf r omega j t math where math mathbf varepsilon j math are the unit vectors of polarization this expansion has the same form as the classical expansion except that now the field amplitudes math hat a j math are operators. Glauber showed that, for an ideal photodetector situated at a point math mathbf r math in a radiation field, the probability of observing a photoionization event in this detector between time math t math and math it t d it t math is proportional to math W I mathbf r , t d it t math , where math W I mathbf r , t psi mid E mathbf r , t cdot E mathbf r , t mid psi math and math psi rangle math specifies the state of the field. Since the radiation field is a quantum mechanical one, we do not know the exact properties of the incident light, ... more details
SPAD may refer to In aircraft manufacture Soci t Pour L Aviation et ses D riv s , also Soci t Provisoire des A roplanes Deperdussin and Bl riot SPAD, French aircraft manufacturer 1912 1921 SPAD VII , SPAD S.XII and SPAD S.XIII , French fighter planes of World War I produced by Soci t Pour L Aviation et ses D riv s A 1 Skyraider , nicknamed Spad , an attack aircraft 1950s and 1960s Simple Plastic Airplane Design , a type of radio controlled airplane In science Single pass albumin dialysis, a simple technique for liver dialysis Single photon avalanche diode , a solid state electronic photodetector Specific antipolysaccharide antibody deficiency, a type of primary immunodeficiency Other uses Special advisers in the United Kingdom Special adviser , informal shorthand for a post in the British Government Self propelled air defence, a self propelled anti aircraft weapon Signal passed at danger , when a train passes a signal on red A neologism describing an online classified ad designed to amass email addresses for the purpose of spamming Spam electronic spam ad The Malay language acronym of the Land Public Transport Commission Malaysia Land Public Transport Commission of Malaysia. disambiguation cs SPAD rozcestn k de SPAD es SPAD fr Spad pl SPAD ... more details
Relative intensity noise RIN , describes the instability in the power physics power level of a laser . The noise term is important to describe lasers used in fiber optic communication and LIDAR remote sensing. Relative intensity noise can be generated from Optical cavity cavity vibration, fluctuations in the laser gain medium or simply from transferred intensity noise from a laser pumping pump source . Since intensity noise typically is proportional to the intensity physics intensity , the relative intensity noise is typically independent of laser power. RIN typically falls off with frequency and is a kind of pink noise . Relative intensity noise is measured by sampling the output current of a photodetector over time and transforming this data set into frequency with a fast Fourier transform . RIN is usually presented as relative noise power in decibel s per hertz at one or several intensities. See also Shot noise External reference http www.rp photonics.com intensity noise.html Intensity noise in Encyclopedia of Laser Physics and Technology http www.rp photonics.com relative intensity noise.html Relative Intensity Noise in Encyclopedia of Laser Physics and Technology Category Noise Category Fiber optic communications Category Laser science optics stub ... more details
Unreferenced date November 2008 In physics and in electronic engineering , dark current is the relatively small electric current that flows through photodetector photosensitive devices such as a photomultiplier tube , photodiode , or charge coupled device even when no photon s are entering the device. It is referred to as reverse bias leakage current in non optical devices and is present in all diode s. Physically, dark current is due to the random generation of electron s and electron hole holes within the depletion region of the device that are then swept by the high electric field . The charge generation rate is related to specific crystallographic defect s within the depletion region. Dark current spectroscopy can be used to determine the defects present by monitoring the peaks in the dark current histogram s evolution with temperature. Dark current is one of the main sources for noise in image sensor s such as charge coupled device s. The pattern of different dark currents can result in a fixed pattern noise dark frame subtraction can remove an estimate of the mean fixed pattern, but there still remains a temporal noise, because the dark current itself has a shot noise . Category Electronic engineering Category Optoelectronics de Dunkelstrom es Corriente de oscuridad fr Courant d obscurit ru ... more details
Orphan date February 2011 A Winston cone is a light collection device with a paraboloid parabolic shape and a reflective inner surface. It concentrates the light passing through a relatively large entrance aperture through a smaller exit aperture. ref name fernow1989 The collection of incoming rays is maximized by allowing off axis rays to make multiple reflections before reaching the exit aperture. Winston cones are used to concentrate light from a large area onto a smaller photodetector or photomultiplier . They are widely used for imaging in the far infrared portion of the electromagnetic spectrum in part because there are no suitable materials to form lenses in the range. ref name hanel2003 References reflist refs ref name fernow1989 cite book first Richard Clinton last Fernow year 1989 title Introduction to experimental particle physics page 160 publisher Cambridge University Press isbn 0521379407 url http books.google.com books?id WNhMzhm0SscC&pg PA160 ref ref name hanel2003 cite book first R. A. last Hanel year 2003 title Exploration of the solar system by infrared remote sensing edition 2nd publisher Cambridge University Press page 160 isbn 0521818974 url http books.google.com books?id zT3T5cyZ4zQC&pg PA160 ref Category Optical devices optics stub ... more details
Multiple issues technical February 2012 orphan January 2012 unreferenced January 2012 Time Stretch Dispersive Fourier Transform also known as photonic time stretch technique PTS relies on wavelength to time mapping by employing group velocity dispersion GVD . It hence can be used to perform Fourier transformation on an optical signal. It indeed replaces a diffraction grating and detector array with a dispersive fiber and single pixel detecor, enabling ultrafast real time spectroscopy and optical imaging imaging . Operation principle The PTS technique is a two step process. At the first step, the spectrum of an optical broadband pulse is encoded by the information e.g., temporal, spatial, or chemical information to be captured. At the next step, the encoded spectrum of the optical pulse is mapped by large group velocity Dispersion optics dispersion into a slowed down temporal waveform and amplified simultaneously by the process of stimulated Raman scattering . Consequently, the optical spectrum can be captured with a single pixel photodetector and digitized in real time. Pulses are repeated for repetitive measurements of the optical spectrum. The time stretch dispersive Fourier transformer consists of a dispersive fiber pumped by lasers and wavelength division multiplexers that couple the lasers into and out of the dispersive fiber. It has proven to be an enabling technology for wideband A D conversion time stretch analog to digital converter ultra wideband analog to digital converters and has also been used for high throughput real time spectroscopy and imaging serial time encoded amplified microscopy STEAM . Category Photonics ... more details
common application of photoresistors is as photodetector s, i.e. devices that measure light intensity. Photoresistors are not the only type of photodetector other types include Charge coupled device CCDs ... more details
Single Chip Vision Systems, April 1996 br 9 Laser Focus World Custom Photodetector Arrays Meet Design ... br 14 P. Suni Photodetector Arrays for Optical Processing, Proc. of the SPIE, 1990 br 15 P. Suni et al. A Linear 1024 Element High Speed, Wide Dynamic Range CCD Photodetector Array, Proc. of the SPIE, 1989 br 16 U.S. Patent 4967249 Gain Compression Photodetector Array br 17 U.S. Patent 4958207 Floating Diode Gain Compression br 18 U.S. Patent 5602407 Switched CCD Electrode Photodetector br 19 U.S. ... more details
Noise equivalent power NEP is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal to noise ratio of one in a one hertz output Bandwidth signal processing bandwidth . ref P.L. Richards, Bolometers for infrared and millimeter waves, Journal of Applied Physics 76 , 1 1994 , doi 10.1063 1.357128 ref An output bandwidth of one hertz is equivalent to half a second of integration time. ref The factor of one half is explained by the Nyquist Shannon sampling theorem . ref The units of NEP are watt s per square root hertz . The NEP is equal to the noise spectral density expressed in units of math A Hz 1 2 math or math V Hz 1 2 math divided by the responsivity expressed in units of math A W math or math V W math , respectively . A smaller NEP corresponds to a more sensitive detector. For example, a detector with an NEP of math 10 12 W sqrt Hz math can detect a signal power of one picowatt with a signal to noise ratio SNR of one after one half second of averaging. The SNR improves as the square root of the averaging time, and hence the SNR in this example can be improved to 10 by averaging for 50 seconds. If the NEP refers to the signal power absorbed in the detector, it is known as the electrical NEP. If instead it refers to the signal power incident on the detector system, it is called the optical NEP. The optical NEP is equal to the electrical NEP divided by the optical coupling efficiency of the detector system. References and footnotes references See also Noise equivalent temperature Specific detectivity DEFAULTSORT Noise Equivalent Power Category Noise Category Superconducting detectors cs Ekvivalentn umov v kon uk ... more details
A rubidium standard or rubidium atomic clock is a frequency standard in which a specified hyperfine level hyperfine transition of electron s in rubidium 87 atoms is used to control the output frequency. It is the most inexpensive, compact, and widely used type of atomic clock , used to control the frequency of television station s, cellular base station cell phone base stations , in test equipment, and global navigation satellite system s like Global Positioning System GPS . Commercial rubidium clocks are less accurate than Cesium clock cesium atomic clock s which serve as Primary standard primary frequency standards , so the rubidium clock is a secondary frequency standard . However, rubidium fountains are currently being developed that are even more stable than caesium fountain clocks. All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6 834 682 610.904 324 Hz. The amount of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1 when the rubidium vapor in the resonance cell is exposed to microwave power near the transition frequency . The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an Radio frequency RF frequency synthesizer synthesizer referenced to the crystal through the transition frequency. See also Atomic clock Caesium standard Hydrogen maser References NIST PD http tf.nist.gov general enc re.htm resonancefrequency FS1037C External links http tf.nist.gov general enc re.htm resonancefrequency NIST Time & Frequency A Z Glossary Resonance Frequency http www.npl.co.uk server.php?show ConWebDoc.1727 Secondary Representation of the SI Second http www.ptb.de en org 4 44 441 info2 e.htm PTB Unit of Time http tycho.usno.navy.mil clockdev RubidiumFountain.html USNO Rubidium Fountain Project http www.npl.co.uk science technology time frequency microwave ... more details
Refimprove date November 2010 Image Dynodes.jpg thumb right 300 px Two horizontal rows of arc shaped dynodes in a photomultiplier tube. A dynode is one of a series of electrodes within a photomultiplier tube. Each dynode is at a more positive electrical potential than its predecessor. Secondary emission occurs at the surface of each dynode. Such an arrangement is able to amplify the tiny current emitted by the photocathode , typically by a factor of one million. Operation The electron s emitted from the cathode are accelerated toward the first dynode, which is maintained 90 to 100 V positive with respect to the cathode. Each accelerated photoelectron that strikes the dynode surface produces several electrons, that are then accelerated to the second dynode, which is held 90 to 100V more positive than dynode 1. For conventional dynode materials, such as BeO and MgO, a multiplication factor of 10 can normally be achieved by each dynode stage. ref Glenn F Knoll Radiation Detection and Measurement 3rd ed , 1999, P270, ISBN 0 471 07338 5. ref By the time this process has been repeated at each of the dynodes, 10 sup 5 sup to 10 sup 7 sup electrons have been produced for each incident photon, dependent on the number of dynodes. Naming The dynode is so named because it acts as a middle point between the photo cathode and the anode . References references See also Microchannel plate detector Photoelectric effect Particle detector Photodetector Category Electronic amplifiers Category Particle detectors ca Dinode de Dynode es D nodo fr Dynode it Dinodo kk lv Dinods nl Dynode pl Katoda wt rna ru ur ... more details
through the fringes, they reflect light that is then collected by a receiving optics and focused on a photodetector ..., the electrical signal from the photodetector will then be proportional to the full particle velocity ... optics and transferred to the photodetector. The reference beam is also sent to the photodetector ... more details
An infrared detector is a detector that reacts to infrared IR radiation . The two main types of detectors are thermal and photonic photodetector s . The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometer s and microbolometer s are based on changes in resistance. Thermocouple s and thermopile s use the thermoelectric effect . Golay cells follow thermal expansion. In IR spectrometer s the pyroelectric detector s are the most widespread. The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise . The materials in these are semiconductors with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photovoltaic detectors contain a p n junction on which photoelectric current appears upon illumination. A few detector materials Types type Spectral range m Wavenumber cm 1 Indium gallium arsenide InGaAs photodiode 0.7 2.6 14300 3800 Germanium photodiode 0.8 1.7 12500 5900 Lead sulfide PbS photoconductive 1 3.2 10000 3100 Lead selenide PbSe photoconductive 1.5 5.2 6700 1900 Indium antimonide InSb photoconductive 1 6.7 10000 1500 Indium arsenide InAs photovoltaic 1 3.8 10000 2600 Platinum silicide PtSi photovoltaic 1 5 10000 2000 Indium antimonide InSb photodiode 1 5.5 10000 1800 Mercury cadmium telluride MCT, HgCdTe photoconductive 0.8 25 12500 400 Mercury zinc telluride MZT, HgZnTe photoconductive Lithium tantalate LiTaO sub 3 sub pyroelectric triglycine sulfate TGS and DTGS pyroelectric The range of pyroelectric detector is determined by the window materials used in their construction. Vanadium pentoxide is frequently used as a detector material in uncooled microbolometer arrays. External links http sales.hamamatsu.com assets applications SSD Characteristics and use of infrared detectors.pdf Characteristics and Use of Infrared Detectors ... more details
File P ikese fotomeeter CIMEL 318A.jpg thumb Sun photometer CIMEL 318A in T ravere . A sun photometer is a type of photometer conceived in such a way that it points at the Sun . Recent sun photometers are automated instruments incorporating a Sun tracking unit, an appropriate optical system, a electromagnetic spectrum spectrally filtering device, a photodetector , and a data acquisition system . The measured quantity is called direct Sun radiance . When a sun photometer is placed somewhere within the atmosphere Earth s atmosphere , the measured radiance is not equal to the radiance emitted by the Sun i.e. the solar extraterrestrial radiance , because the solar flux is reduced by atmospheric absorption electromagnetic radiation absorption and scattering . Therefore, the measured radiant flux is due to a combination of what is emitted by the Sun and the effect of the atmosphere the link between these quantities is given by Beer s law . The atmospheric effect can be removed with Langley extrapolation this method therefore allows measuring the solar extraterrestrial radiance with ground based measurements. Once the extraterrestrial radiance is known, one can use the sun photometer for studying the atmosphere , and in particular for determining the atmospheric optical depth . Also, if the signal at two or more suitably selected electromagnetic spectrum spectral intervals is measured, one can use the information derived for calculating the vertically integrated concentration of selected atmospheric gases, such as water vapour , ozone , etc. References Glenn E. Shaw, Sun photometry , Bulletin of the American Meteorological Society 64 , 4 10, 1983. Category Optical devices Category Electromagnetic radiation meters Optics stub de Sonnenphotometer lb Sonnephotometer zh ... more details
For a timepiece with both timekeeping and stopwatch functions chronograph A gun chronograph is an instrument used to measure the velocity of a projectile fired by a gun. History Around 1800, the ballistic pendulum was used to measure the momentum of the projectile fired by a gun dividing the momentum by the projectile mass gives the velocity . An early chronograph that measures velocity directly was built in 1804 by Grobert , a colonel in the French Army. This used a rapidly rotating axle with two disks mounted on it about 13 feet apart. The bullet was fired parallel to the axle, and the angular displacement of the holes in the two disks, together with the rotational speed of the axle, yielded the bullet velocity. Modern chronograph The modern chronograph consists of two sensing areas called chronograph screens , which contain photodetector optical sensors that detect the passage of the bullet. The bullet is fired so it passes through both screens, and the time it takes the bullet to travel the distance between the screens is measured electronically. The first electronic ballistic chronograph was invented by Kiryako Jerry Arvanetakis in the 1950s. Citation needed date May 2011 As consulting engineer under contract by NACA later NASA , he was asked to find a way to accurately measure the velocity of various projectiles fired at hypersonic hyper velocities into a variety of engineered materials in anticipation of manned space flight. His first design was an open rectangular frame of square aluminum tubing with a screen of fine copper wire at both ends. Breaking the first wire started charging a capacitor , breaking the second wire stopped it. Measuring the accumulated voltage and knowing the rate of charge the elapsed time could be accurately calculated. References http www.1911encyclopedia.org Chronograph Category Horology Category Firearm terminology pt Cron grafo bal stico fr Chronographe balistique ... more details
Other uses An electric eye is a photodetector used for detecting obstruction of a light beam. An example is the Door Door related accidents door safety system used on garage door opener s that use a light transmitter and receiver at the bottom of the door to prevent closing if there is any obstruction in the way that breaks the light beam. The device does not provide an image only presence of light is detectable. Visible light may be used, but infrared radiation conceals the operation of the device and typically is used in modern systems. Originally systems used lamps powered by direct current or the power line alternating current frequency, but modern photodetector systems use an infrared LED light emitting diode modulated at a few kilohertz, which allows the detector to reject stray light and improves the range, sensitivity and security of the device. Examples Highway vehicle counter In the 1930s an electric eye vehicle counter was introduced in the US using two IR lamps set apart so that only cars and not pedestrians would be counted. ref http books.google.com books?id dyYDAAAAMBAJ&pg PA36&dq Popular Science motor gun boat&hl en&ei NinuTNraIJ2KnAexu8T4Cg&sa X&oi book result&ct result&resnum 10&ved 0CFMQ6AEwCQ v onepage&q&f true Autos Are Counted By Electric Eye , January 1937, Popular Science ref First compact commercial unit Also, a compact type of electric eye was offered in 1931 that was enclosed in a small steel case and much easier to install compared to older models. ref http books.google.com books?id u IDAAAAMBAJ&pg PA398&dq Popular Mechanics 1931 curtiss&hl en&ei 2kTvTOz A6HfnQfR0 C7Cw&sa X&oi book result&ct result&resnum 3&sqi 2&ved 0CC8Q6AEwAg v onepage&q&f true Electric Eye And Relay Set Combined In Cabinet , March 1931, Popular Mechanics ref Automatic wrapping machines In the 1930s an electric eye apparatus was developed to help a wrapping machine, wrap 82 boxes a minute. ref http books.google.com books?id u IDAAAAMBAJ&pg PA185&dq Popular Mechanics 1931 ... more details
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