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Resumo da aula anterior

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1 Resumo da aula anterior
Apresentação de Nathália sobre Aceleradores de Partículas – Projeto Sirius Detectores fotoemissivos, fotomultiplicadoras, ganho, channeltron, visão noturna. Superficies e materiais fotoemissivos, espectroscopia emissiva de elétrons. Fotodiodo de silício. Célula solar, diferentes dispositivos: cristalino, policristalino, junção singular e multijunções, orgânicos, desenvolvimento da eficiências das células solares. Dinodos: BeO, MgO 10X dispotic 2013

2 Aula de hj Continuação sobre detectores. dispotic 2013

3 Fotocondutividade Dois tipos de material, dois processos:
Processo para fotocondutividade intrínseca: fotoexcitação provoca geração de portadores de carga que vão para a banda de condução. Desde que exista uma ddp aplicada, permite a mudança de corrente sobre o efeito da luz. Para o caso extrínseco, portador de carga doador pode ser excitado para banda de condução, aumentando a condutividade, como tb pode ocorrer a criação de buracos com a excitação de elétrons para o nível aceitador. dispoptic 2013

4 Detectores fotocondutivos intrínsecos
dispoptic 2013

5 Detector fotocondutivo
Tempo de vida do portador # de portadores em excesso gerados pela luz Função degrau Solução td é o tempo que o portador atravessa o gap(d) provocando uma corrente q/ td. i é a corr. externa dispoptic 2013

6 Outros detectores Detectores PIN e APD (fibras ópticas)
Detectores térmicos Fotoacústicos dispoptic 2013

7 Detectores usados em fibras ópticas
PIN diode ou diodo PIN (P Intrinsic N). O diodo PIN possui uma camada intrínseca entre as camadas P e N de um diodo. APD (Avalanche PhotoDiode) ou fotodiodo de avalanche. Mais sensível que o fotodiodo pin dispoptic 2013

8 Fotodiodo pn (a) e fotodiodo pin (b)
PIN diodes A PIN diode is a fast low capacitance switching diode. Do not confuse a PIN switching diode with a PIN photo diode here. A PIN diode is manufactured like a silicon switching diode with an intrinsic region added between the PN junction layers. This yields a thicker depletion region, the insulating layer at the junction of a reverse biased diode. This results in lower capacitance than a reverse biased switching diode. Pin diode: Cross section aligned with schematic symbol. PIN diodes are used in place of switching diodes in radio frequency (RF) applications, for example, a T/R switch here. The 1n V, 1 A general purpose power diode is reported to be usable as a PIN switching diode. The high voltage rating of this diode is achieved by the inclusion of an intrinsic layer dividing the PN junction. This intrinsic layer makes the 1n4007 a PIN diode. Another PIN diode application is as the antenna switch here for a direction finder receiver. PIN diodes serve as variable resistors when the forward bias is varied. One such application is the voltage variable attenuator here. The low capacitance characteristic of PIN diodes, extends the frequency flat response of the attenuator to microwave frequencies. dispoptic 2013

9 dispoptic 2013

10 Fotodiodo pin A camada intrínseca serve para aumentar a região da junção, conseqüentemente melhora a fotoconversão. Modo fotovoltaico qdo não há campo externo Modo fotocondutor qdo polarizado por fonte externa dispoptic 2013

11 Resposta espectral fotodiodo pin de Si
Responsividade típica R A – REALÇADO PARA 900nm B – REALÇADO PARA 1060nm Destaque para algumas fontes emissivas dispoptic 2013

12 Fotodiodo avalanche (APD)
A desvantagem de um fotodiodo pin produzir apenas um par de portadores de carga. No APD uma ddp aplicada de forma reversa de até 2kV acelera os fotoelétrons de maneira que cada fotoelétron primário resulta em milhares de elétrons no eletrodo. dispoptic 2013

13 http://micro. magnet. fsu
Ver arquivo APDFinalPaper.doc dispoptic 2013

14 PIN e APD Tabela 1 – Comparação de fotodiodo PIN e APDs Parametro PIN
Tipo de material Si, Ge, InGaAs Largura de banda DC a 40+ GHz Comprimento de onda 0.6 to 1.8 µm Eficiência de conversão 0.5 to 1.0 Amps/Watt 0.5 to 100 Amps/Watt Circuito eletrônico de apoio Não precisa Alta tensão, temperatura estabilizada Custos (pronto para fibra) $1 to $500 $100 to $2,000 dispoptic 2013

15 Sem esquecer o fototransistor
Photo Transistor:   One of the most popular light detectors is the photo transistor. They are cheap, readily available and have been used in many published communications circuits. But as I have indicated above, the PIN photodiode is still a much better choice if you want systems with better performance. As shown in Figure 2b-1, a phototransistor is a silicon photodiode connected to the base-emitter terminals of a silicon transistor. Since the phototransistor it is made of silicon, it has a similar response curve as a standard silicon PIN photodiode.   Figure 2b-1The photodiode is connected directly to the transistor, it is not reversed biased and operates in a photovoltaic mode. The current produced by the photodiode is routed to the transistor that provides a sizable current gain. This amplification gives the photo transistor much more light sensitivity than a standard PIN diode. But, with the gain comes a price. The photodiode/transistor connection dramatically slows down the otherwise fast response time of the diode inside. Most phototransistors will have response times measured in tens of microseconds, which is some 100 times slower than similar PIN diodes. Such slow speeds reduce the usefulness of the device in most communications systems. They also have the disadvantage of having small active areas and high noise levels. You will often find them being used for simple light reflector and detector applications that do not rely on fast light pulses. But, overall, they are a poor substitute for a good PIN diode when connected to well designed receiver circuit. Prático, mas convêm ainda o APD dispoptic 2013

16 Como aumentar a absorção de luz do detector?
Aumentar a sensitividade do detector com filmes anti-refletores. Criar armadilhas de fótons através de bobinas de nano-fios refrigerados THeL. Aumento de fótons armadilhados => aumento na eficiência de conversão. dispoptic 2013

17 Detectores térmicos Termopar Piroelétrico Bolômetro dispoptic 2013

18 Origem do termopar Efeito Seebeck Thomas Johann Seebeck (1770-1831)
Profissão Descoberta – bússola Também denominado de efeito termoelétrico. Existem outros efeitos termoelétricos. dispoptic 2013

19 Efeitos termoelétricos
Ocorre quando portadores de carga moveis estão sujeitos à influencia de gradientes de temperatura e/ou gradientes de potencial elétrico. Na ausência de um campo magnético existem três tipos de efeitos termoelétricos. Efeito Seebeck Efeito Peltier Efeito Thomson Thomson effect One of three reversible thermoelectric phenomena (often known simply as thermoelectric effects), the others being the Seebeck effect and a Peltier effect. In 1851 William Thomson (later Lord Kelvin) was led by thermodynamic reasoning to conclude that sources of electromotive force (emf) exist in a thermoelectric circuit in addition to those located at the junctions. In particular, he predicted that an emf would arise within in a single conductor whenever a temperature gradient was present. The truth of this prediction can be demonstrated by the experiment illustrated in the diagram here. In this experiment a current passes through an iron rod which is bent into a U-shape. Resistance coils, R1 and R2, are wound about the two sides of the U, as shown. These form two arms of a balanced Wheatstone bridge. The bottom of the U is then heated. This establishes two temperature gradients – a positive one extending from A to C, and a negative one extending from C to B. As a result of this operation, the bridge becomes in such a direction as to indicate that the resistance of R1 has increased more than that of R2. Evidently, heat has been liberated R1 and absorbed at R2. Absorption of heat is evidence for an electromotive force (emf) that is acting in the same direction as that of the current, that is to say, electrical energy is being supplied to the circuit at the expense of heat energy of the environment. Such is the case in the section. Likewise, in the section AC, the current is opposed by an emf, with consequent transformation of electrical energy into heat energy. Thus, in iron, the Thomson emf would would give rise to a current in the iron from hot to cold regions. many metals, including bismuth, cobalt, nickel, and platinum, in addition to iron, exhibit this same property, which is referred to as the negative Thomson effect. Another group of metals, including antimony, cadmium, copper, and silver, display a positive Thomson effect; in these, the direction of the Thomson emf is such as to support a current within the metal from cold to hot regions. In one metal, lead, the Thomson effect is zero. In certain metals the effect reverses sign as the temperature is raised or as the crystal structure is altered. The magnitude of the Thomson emf for a given material, a, is expressed in terms of the Thomson coefficient, σa, which has dimensions of emf/degree. Thus σa dt is the emf that exists between two points whose temperatures differ by dt °C. Hence, the heat absorbed per second between two points at temperature t1 and t2, respectively, when a current of I amperes passes through the material, is given by Heat absorbed/sec = I [integral between t1 and t2]σa dt - I2R The Thomson coefficient, σa, is positive (negative) for materials exhibiting the positive (negative) Thomson effect. The term in the equation above is simply the Joule heat that is always liberated when a current flows through an imperfect conductor. It has no relation to the Thomson effect, but is included in the equation for completeness. It appears that the total Thomson emf along a conductor depends only upon the temperatures of the two ends, and not in any way upon the particular manner in which the temperature gradient varies. This empirically observed fact is known, after its discoverer, as the law of Malus (1851). In 1851 William Thomson (later Lord Kelvin) dispoptic 2013 S.O. Kasap -Thermoelectric effects in metals

20 Efeito Seebeck dispoptic 2013
Uma diferença de temperatura entre dois pontos de um condutor ou de um semicondutor resulta numa ddp entre esses dois pontos. De outra forma: a gradiente de temperatura num condutor ou semicondutor da lugar a um campo elétrico. O coeficiente Seebeck calibra a magnitude desse efeito. A voltagem termoelétrica desenvolvida por unidade de diferença de temperatura num condutor é denominada de coeficiente Seebeck. Somente a ddp neto de Seebeck entre metais diferentes pode ser medido. O principio do termopar é baseado no efeito Seebeck. 1. The Seebeck Effect and Normal Metals Consider an aluminum rod that is heated at one end and cooled at the other end as depicted in Figure 1. The electrons in the hot region are more energetic and therefore have greater velocities than those in the cold region1. Consequently there is a net diffusion of electrons from the hot end toward the cold end which leaves behind exposed positive metal ions in the hot region and accumulates electrons in the cold region. This situation prevails until the electric field developed between the positive ions in the hot region and the excess electrons in the cold region prevents further electron motion from the hot to cold end. A voltage is therefore developed between the hot and cold ends with the hot end at positive potential. dispoptic 2013

21 Efeito Seebeck (Notes on using thermocouples - Dr. Robert J
Efeito Seebeck (Notes on using thermocouples - Dr. Robert J. Moffat, Stanford University) O coeficiente de Seebeck: Ferro-constantan (J) Cromel-alumel (K) Cobre-constantan (T) Outros Any two wires of different materials can be used as a thermocouple if connected together as in Figure 1. The AB connection is called the "junction". When the junction temperature, TJct, is different from the reference temperature, TRef, a low-level DC voltage, E , will be available at the +/- terminals. The value of E depends on the materials A and B, on the reference temperature, and on the junction temperature. The governing equations for two-wire thermocouples are shown in Eq. 1 through to Eq. 4. If a circuit has more than two wires, more terms would be needed. From Eq. 1, we can see that the EMF is generated by the wires, not the junction: the junction being just an electrical connection between the two wires. The signal is generated in the wires where the temperature gradient, dt/dx, is not zero: uniform temperature wires do not generate any EMF. If both wires are uniform in calibration, then Eq. 2 can be used, and if the two wires both begin at TRef and end at TJct, then Eq. 3 applies. EMF-Temperature tables can only be used when the circuit consists of only two wires, both of which are uniform in calibration, and both of which begin at TRef and end at TJct. When only small temperature differences are involved, the values of A and B can be treated as constants, and Eq. 4 gives a good approximation to the EMF. dispoptic 2013

22 Efeito Peltier É o efeito reverso do Seebeck Metal Semicondutor
é o coeficiente de Peltier Refrigeração, uso doméstico, detectores The Peltier effect is the reverse of the Seebeck effect; a creation of a heat difference from an electric voltage. It occurs when a current is passed through two dissimilar metals or semiconductors (n-type and p-type) that are connected to each other at two junctions (Peltier junctions). The current drives a transfer of heat from one junction to the other: one junction cools off while the other heats up; as a result, the effect is often used for thermoelectric cooling. This effect was observed in 1834 by Jean Peltier, 13 years after Seebeck's initial discovery. When a current I is made to flow through the circuit, heat is evolved at the upper junction (at T2), and absorbed at the lower junction (at T1). The Peltier heat absorbed by the lower junction per unit time, is equal to Where Π is the Peltier coefficient ΠAB of the entire thermocouple, and ΠA and ΠB are the coefficients of each material. P-type silicon typically has a positive Peltier coefficient (though not above ~550 K), and n-type silicon is typically negative. The conductors are attempting to return to the electron equilibrium that existed before the current was applied by absorbing energy at one connector and releasing it at the other. The individual couples can be connected in series to enhance the effect. The direction of heat transfer is controlled by the polarity of the current; reversing the polarity will change the direction of transfer and thus the sign of the heat absorbed/evolved. A Peltier cooler/heater or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other. Peltier coolers are also called thermo-electric coolers (TEC). dispoptic 2013

23 Efeito Thomson – Lord Kelvin 1851
Descreve o aquecimento ou resfriamento de um condutor portador de carga com a gradiente de temperatura. r resistividade J densidade de corrente m coeficiente de Thomson(pode ser +-, depende do material) dT/dx gradiente de temperatura Thomson effect Thomson effect, named for William Thomson (Lord Kelvin), describes the heating or cooling of a current-carrying conductor with a temperature gradient. Any current-carrying conductor, with a temperature difference between two points, will either absorb or emit heat, depending on the material. If a current density J is passed through a homogeneous conductor, heat production per unit volume is where ρ is the resistivity of the material dT/dx is the temperature gradient along the wire μ is the Thompson coefficient. The first term ρ J is simply the Joule heating, which is not reversible. The second term is the Thomson heat, which changes sign when J changes directions. The Peltier and Seebeck coefficients are related by the Thomson relation dispoptic 2013

24 Série termoelétrica Mercury Lead Tin Chromium Molybdenum Rhodinium Iridium Gold Silver Silicon Bismuth Nickel Cobalt Palladium Platinum Uranium Copper Manganese Titanium Aluminium Zinc Tungsten Cadmium Iron Arsenic Tellurium Germanium dispoptic 2013

25 Demonstração prática do efeito termoelétrico
Varetas metálicas de Fe, Ag, Al e latão aquecidas com um isqueiro numa extremidade e medimos a voltagem entre as extremidades a fem gerada. Al => V Fe => V Ag => V Latão => V dispoptic 2013

26 Série termoelétrica dispoptic 2013

27 Termopar - Termopilha Termopilha Leybold Resposta de 0,16 mV/mW
The Seebeck effectThe discovery of thermoelectricity dates back to Seebeck [1] ( ). Thomas Johann Seebeck was born in Revel (now Tallinn), the capital of Estonia which at that time was part of East Prussia. Seebeck was a member of a prominent merchant family with ancestral roots in Sweden. He studied medicine in Germany and qualified as a doctor in Seebeck spent most of his life involved in scientific research. In 1821 he discovered that a compass needle deflected when placed in the vicinity of a closed loop formed from two dissimilar metal conductors if the junctions were maintained at different temperatures. He also observed that the magnitude of the deflection was proportional to the temperature difference and depended on the type of conducting material, and does not depend on the temperature distribution along the conductors. Seebeck tested a wide range of materials, including the naturally found semiconductors ZnSb and PbS. It is interesting to note that if these materials had been used at that time to construct a thermoelectric generator, it could have had an efficiency of around 3% - similar to that of contemporary steam engines. The Seebeck coefficient is defined as the open circuit voltage produced between two points on a conductor, where a uniform temperature difference of 1K exists between those points. Thermoelectric potential and contact potential In introductory texts the thermoelectric potential is usually attributed to the temperature dependence of the contact potential between different metals. As one of the junctions in a thermoelectric circuit is heated the contact potential there changes compared with the other junction. According to this explanation, the difference of the contact potentials yields the thermoelectric potential of the circuit. In the following it is shown that this explanation is incorrect. The contact potential between two metals is caused by their different work functions , which are the energies needed to remove an electron from the metal. The work function of a metal is the difference between the energy of a free electron (with no kinetic energy) outside the metal, which we choose as the zero of energy, and the chemical potential of the conduction electrons (Fig. 6) according to The mean occupation number of a one-electron state with energy in a metal or semiconductor is given by the Fermi distribution as (6) VER At room temperature, apart from a relatively narrow thermal energy shell of width , states with energies are occupied, states with are vacant (Fig. 7). As the temperature decreases, the transition between occupied and vacant states sharpens. In the limit the chemical potential is also known as Fermi energy. dispoptic 2013

28 Outro esquema da termopilha
dispoptic 2013

29 Detector IV JonDetech - Termopilha
Carcteristicas Vídeo demo dispoptic 2013

30 Outros detectores considerados térmicos
Piroelétrico Material não-condutor DT ~ DQ Baixa potência de detecção Não recomendável para CW TGS DTGS Pyroelectricity can be visualized as one side of a triangle, where each corner represents energy states in the crystal: kinetic, electrical and thermal energy. The side between electrical and thermal corners represents the pyroelectric effect and produces no kinetic energy. The side between kinetic and electrical corners represents the piezoelectric effect and produces no heat. Although artificial pyroelectric materials have been engineered, the effect was first discovered in minerals such as quartz and tourmaline and other ionic crystals. The pyroelectric effect is also present in both bone and tendon. The name is derived from the Greek pyr, fire, and electricity. Pyroelectric charge in minerals develops on the opposite faces of asymmetric crystals. The direction in which the propagation of the charge tends toward is usually constant throughout a pyroelectric material, but in some materials this direction can be changed by a nearby electric field. These materials are said to exhibit ferroelectricity. All pyroelectric materials are also piezoelectric, the two properties being closely related. Very small changes in temperature can produce an electric potential due to a materials' pyroelectricity. Motion detection devices are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a difference in charge. dispoptic 2013

31 Efeito piroelétrico dispoptic 2013

32 Outro tipo de detecção mas não menos importante - Fotoacústica
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33 Fotoacustica – 1880 – AG Bell - fotofone
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34 Variante Fotoacústica – janela opto-térmica
The operational principle of opto-thermal window technique (OW), actually a variant of conventional PA spectroscopy is as follows: a modulated (laser) radiation passes through the OW cell before impinging on the sample. The OW cell is actually an optically transparent disc (having large thermal expansion coefficient) the rear side of which is provided with piezoelectric transducer. Due to the absorption of radiation, sample's temperature rises and the generated heat diffuses into the disc (being in a good thermal contact with the sample) that expands the induced stress is detected by a lock-in amplifier. In comparison to conventional PA spectroscopy, the OW method offers some attractive features. At first, the requirement for accommodating the sample in the sealed cell is no longer an impetus. In addition, the OW signal not only remains unaffected by thermal expansion of the sample but is also less susceptible to the effect of other sample's thermal parameters. Finally, as long as it exceeds sample's thermal diffusion length, the thickness of the sample is not relevant making OW technique more practical for quantitative IR analysis of strongly absorbing fluids and semi fluids. For an optically opaque and thermally thick (an ideal) sample, making a good thermal contact with a thermally thick OW, the amplitude of the normalized, dimensionless optothermal signal is related to the product of the absorption coefficient and the thermal diffusion length. This forms the basis for obtaining the absorption spectrum of the sample under investigation, provided optical and thermal properties of a reference sample at a given wavelength and modulation frequency are known. Janela com propriedades de coef. de expansão térmica alto dispotic 2013

35 Fotoacústica During a photoacoustic measurement the sample is enclosed in a small, tightly closed sample compartment called photoacoustic cell (usually cylindrical in shape).The photoacoustic effect is based on the sensitive detection of acoustic waves launched by the absorption of pulsed or modulated laser radiation via transient localized heating and expansion in a gas, liquid, or solid. When the laser hits the sample, some of the energy is absorbed by the molecules in the samples resulting in a region of higher temperature. The rise in temperature will generate an expanding region and a pressure wave will propagate away from the heat source. The periodic pressure wave can be detected using a pressure transducer in contact with sample (piezo electric)or in contact with contact gas (microphone) in the photoacoustic cell. Please see Fig. (1) for details. The pressure transducer signal is proportional to the amplitude of the pressure wave. dispotic 2013

36 Fotoacústica Variable Temperature Photoacoustic Cell dispotic 2013

37 Fotoacústica Liquid Photoacoustic Cell dispotic 2013

38 Eletreto = cera de abelha, cera de carnaúba, resina
Fotoacústica – microfone de eletreto Eletreto = cera de abelha, cera de carnaúba, resina Como polarizar Microfone de eletreto Como testar Electret, material that maintains electrical polarity after exposure to a powerful electric field. In such a material, one end has a slightly positive electric charge and the other end has a slightly negative charge, but the net charge of the material is zero. Electrets are widely used in all kinds of microphones, from telephone mouthpieces to hearing aids. They are also used in loudspeakers, some electrical meters, and keys or buttons on devices such as telephones and calculators. Electrets are made from materials such as wax, plastic, or ceramics. The individual molecules of these materials each have a positively charged and negatively charged end. These polarized molecules are arranged randomly so that the material has no overall polarization. When the material is exposed to a strong electric field (about 1 million v/m, or about 300,000 v/ft) the molecules of the material rotate into permanent alignment and their orientation remains unchanged even after they are no longer subject to the electrical field. Some electrets are created by subjecting molten material to a strong electric field, then allowing the material to harden while still in the field. The electret microphone of a telephone, the most familiar application of an electret, is made by solidifying a molten material. In this type of microphone, a diaphragm that vibrates as sound waves hit it is made of a plastic electret coated with a thin film of metal. The metal side of the diaphragm faces the mouthpiece and the plastic side faces a metal disk. The permanent charge of the electret causes an electric field between the diaphragm and the disk. As the diaphragm vibrates, the distance between it and the disk changes, affecting the intensity of the electric field. This produces an electric current through wires attached to the diaphragm and disk. This current can be sent through telephone lines and translated back into sound by the receiver of another telephone. Microsoft ® Encarta ® © Microsoft Corporation. All rights reserved. dispotic 2013

39 Fotoacústica – espectrômetro
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40 Ainda outros detectores
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41 Bolômetro – 1878 – Samuel Pierpoint Langley
DI ~ DR 200m – 1mm 50mK – 300mK Astronomia Partículas A detector which measures the amount of radiation falling upon it by measuring changes in resistance produced by heating due to the radiation. Detector que mede a qtd de radiação incidente medindo mudança de resistência produzido pelo aquecimento provocado pela radiação By 1880, Langley's bolometer was refined enough to detect thermal radiation from a cow a quarter of a mile away. dispotic 2013

42 Tipo de bolômetro de Pt New infrared sensors are small, simple, and sensitive Pauline Renoux A nanoscale platinum thermal detector with a simple design has promising properties for sensing near- to mid-infrared radiation. 5 March 2012, SPIE Newsroom. DOI: / Infrared detectors have long provoked a strong interest in research and industry, and they are now used in many domains, including fire detection and defense systems. Small sensor size is an important factor, being linked to resolution of thermal imaging devices. These days detectors are commonly tens of microns in size. Much effort has gone into making devices smaller while improving their sensing ability, but often only by increasing cost or sacrificing ease of use. 5 March 2012, SPIE Newsroom. Bolômetro de Pt com fio detector de 300nm×4μm. Imagem MEV, não a escala, substrato de Si e camada isolante de SiO2. Radiação IV aquece o fio alterando sua resistência. dispotic 2013

43 Célula de Golay – (1947 – MJE Golay)
1.- janela 2.- filme semitransparente 3.- 4.- 5.- sistema re-focagem 6.- 7.- 8.- LED 9.- 10.- 11.- fotodiodo Useful frequency range 1 1 to 4 mm (70 GHz-300 THz) Calibrated frequency range M ( GHz) Noise equivalent power (NEP) 7 X W/HzlI2 Responsivity 350 V/W Time constant 6 msec Sensitive area 1 mm X 1 mm A modulated signal passes through the window of the device (1) and is incident upon the semi-transparent film (2) located in the centre of a sealed chamber. The energy absorbed in the film heats the gas in the chamber, causing the pressure to rise. This pressure change distorts the membrane forming the wall of the chamber. A light emitting diode (LED) (8) sends a signal through re-focussing optics (5) and onto the mirrored back surface of the chamber containing the absorbing membrane. This radiation is reflected back through the lower half of the optics via a grating as shown in the diagram, and re-focussed onto a photodiode (11). The degree of illumination of the photodiode by radiation from the LED is a function of the shape of the front chamber. A preamplification circuit is included in the device. This is based on an operational amplifier and double FET circuit that converts the output from the photodiode into a useful AC voltage output. Faixa espectral: 1m – 4mm NEP: 7x10-10 W/Hz1/2 Responsividade: 350V/W Tau: 6ms Área sensitiva: 1mmX1mm dispotic 2013

44 Outra célula de Golay dispotic 2013 Technical specification:
Diameter of entrance cone, mm: 11.0 Diameter of entrance window, mm: 6.0 Material of entrance window: High-Density Polyethylene (HDPE) Optimal operating wavelength range, μm: 15 ÷ 8000 Recommended detected power, W, up to: 1 x 10-5 Optimum modulation frequency, Hz: 15 ± 5 Noise-equivalent 20Hz: typical, W/Hz1/2 minimum, W/Hz1/2 1.4 x x 10-10 Optical 20Hz: typical, V/W maximum, V/W 1 x x 105 Response rate: typical, ms minimum, ms 30 25 Detectivity (D*) at entrance cone aperture: typical, cm x Hz1/2/W maximum, cm 7.0 x x 109 Ambient operating pressure range, mm Hg 760 ÷ 10-3 Operational and storage temperature range, °C 5 ÷ 40 Humidity, % 45 ÷ 80 Vibration avoid vibrations at 1 ÷ 100 Hz Rated voltage, VAC 100/115 ± 10%, 220/230 ± 10% Line frequency, Hz 50 ÷ 60 Overall dimensions, L x W x H, mm3 126 x 45 x 87 Weight, kg 0.8 Technical specification: Diameter of entrance cone, mm: 11.0 Diameter of entrance window, mm: 6.0 Material of entrance window: High-Density Polyethylene (HDPE) Optimal operating wavelength range, μm: 15 ÷ 8000 Recommended detected power, W, up to: 1 x 10-5 Optimum modulation frequency, Hz: 15 ± 5 Noise-equivalent 20Hz: typical, W/Hz1/2 minimum, W/Hz1/2 1.4 x x Optical 20Hz: typical, V/W maximum, V/W 1 x x 105 Response rate: typical, ms minimum, ms Detectivity (D*) at entrance cone aperture: typical, cm x Hz1/2/W maximum, cm 7.0 x x 109 Ambient operating pressure range, mm Hg 760 ÷ 10-3 Operational and storage temperature range, °C 5 ÷ 40 Humidity, % 45 ÷ 80 Vibration avoid vibrations at 1 ÷ 100 Hz Rated voltage, VAC 100/115 ± 10%, 220/230 ± 10% Line frequency, Hz 50 ÷ 60 Overall dimensions, L x W x H, mm3 126 x 45 x 87 Weight, kg 0.8   dispotic 2013

45 Câmera CCD CCD = Charge Coupled Device – 1969 – Willard Boyle & George Smith - ATT A device made up of semiconductors arranged in such a way that the electric charge output of one semiconductor charges an adjacent one. Charge-Coupled Device (CCD) sensor CCDs (Charge Coupled Devices) a solid-state chip containing a series of tiny, light-sensitive photosites and was originally developed by Honeywell (and it won a legal case took against ALL major camera makers including Minolta, who first popularizing autofocus camera with the original Maxxum, and other major makers like Canon, Nikon, Pentax in which have performed a out of court settlement with infringement of the copyrights a few years ago). It forms like the heart of all electronic and digital cameras. CCD's can be thought of as film for electronic cameras, but they are also found in video cameras and desktop scanners. CCDs consist of thousands or even millions of cells, each of which is light-sensitive and capable of producing varying amounts of charge in response to the amount of light they receive. Similar to a video camera, digital camera use the lens which focuses the image onto a Charge Coupled Device (CCD), which then converts the image into electrical pulses. These pulses are then saved into memory In short, Just as the film in a conventional camera records an image when light hits it, the CCD records the image electronically The photosites convert light into electrons. The electrons pass through an analog-to-digital converter, which produces a file of encoded digital information in which bits represent the color and tonal values of a subject. CCD's are usually arranged as either a line of cells or a rectangular (a square is also a type of rectangle) array of cells. Both types of sensors can be used in digital imaging backs and cameras. Sensors employing video technology have rectangular pixels, while sensors with square pixels were created specifically for use on computerThe performance of a CCD is often measured by its output resolution, which in turn is a function of the number of photosites on the CCD's surface. The CCD employ in the top of the line Kodak DCS-460 digital camera has 3060 photosites on its horizontal axis and 2036 photosites on its vertical axis (that's how it reads in the advertisement they put Megapixel CCD (3060 x 2060 pixels) ). On output, the photo sites deliver an effective resolution of six million Charge-Coupled Device (CCD), sensitive electronic device that stores packets of information as electric charge. Because of their versatility in storing charge, CCDs are often used as analog-to-digital and digital-to-analog converters and signal scramblers, but their main function is recoding information about light hitting the surface of the CCD to create light images electronically. A CCD used for recording visual information is made of an array of photodiodes (devices that conduct electricity when light strikes them) on top of a semiconductor (a material that conducts electricity better than electrical insulators but not as well as electrical conductors). When light strikes a photodiode, an electric current proportional to the amount of light is sent to a capacitor, which stores the charge. The semiconductor processes the signal from the capacitor and sends it to a computer or other device that can analyze the data about the light that hit the CCD. CCDs are used in facsimile machines, photocopiers (see Xerography), bar-code readers, and cameras. In astronomy CCDs have almost completely replaced photographic film as an image-capturing method. A CCD is about a hundred times more sensitive to light than photographic film or a photographic plate. The signal from a CCD is also easier than a photographic image to convert into digital code for storage in a computer. Microsoft ® Encarta ® © Microsoft Corporation. All rights reserved. dispotic 2013

46 Simulação de CCD http://astro. unl
dispotic 2013

47 CCD Capturar e armazenar imagens: Scanners Telescópio
Leitora codigo de barras Cameras de video e fotográficas dispotic 2013

48 Câmera CCD e CMOS Simplified GIF animation of a CCD image sensor with Interline Transfer technology.  After the buckets of charge accumulate in the individual photo sensors, they are simultaneously transferred into the vertical shift registers.  Buckets of charge move down the vertical registers and across the horizontal register.  At the end, charge is converted to voltage and amplified. Simplified GIF animation of a CMOS image sensor with active pixel sensor (APS) technology.  Where a CCD converts charge to voltage at the end of the process, a CMOS sensor performs this conversion at the outset.  The voltages can then be output over compact, energy-saving micro wires. dispotic 2013

49 Resumo de detectores Dispositivo Parâmetro sensitivo Região espectral
Fotocelula, fotomultiplicadora Emissão de elétrons uv, vis, iv Emulsão fotográfica Reação química Câmera CCD e CMOS (CCD) Carga fotovoltaico, piroelétrico, termopar voltagem bolômetro, fotocondutivo (LDR) resistência iv Célula de Golay Pressão de gás Olho humano vis dispotic 2013

50 Próxima aula conectores, acopladores e adaptadores
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