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109-441: In order to capture what the eye is seeing as accurately as possible, an EyeTap uses a beam splitter to send the same scene (with reduced intensity) to both the eye and a camera. The camera then digitizes the reflected image of the scene and sends it to a computer. The computer processes the image and then sends it to a projector. The projector sends the image to the other side of the beam splitter so that this computer-generated image

218-500: A {\displaystyle E_{a}} and E b {\displaystyle E_{b}} are non-zero, and using these two results we obtain where " ∗ {\displaystyle ^{\ast }} " indicates the complex conjugate. It is now easy to show that τ † τ = I {\displaystyle \tau ^{\dagger }\tau =\mathbf {I} } where I {\displaystyle \mathbf {I} }

327-434: A ^ a † , a ^ b † , a ^ c † {\displaystyle {\hat {a}}_{a}^{\dagger },{\hat {a}}_{b}^{\dagger },{\hat {a}}_{c}^{\dagger }} , and a ^ d † {\displaystyle {\hat {a}}_{d}^{\dagger }} , so that where

436-669: A ^ d † {\displaystyle {\hat {a}}_{c}^{\dagger }{\hat {a}}_{d}^{\dagger }} term has cancelled. Therefore the output states always have even numbers of photons in each arm. A famous example of this is the Hong–Ou–Mandel effect , in which the input has n = m = 1 {\displaystyle n=m=1} , the output is always | 20 ⟩ c d {\displaystyle |20\rangle _{cd}} or | 02 ⟩ c d {\displaystyle |02\rangle _{cd}} , i.e.

545-561: A b {\displaystyle |00\rangle _{ab}} and add a photon in port a to produce then the beam splitter creates a superposition on the outputs of The probabilities for the photon to exit at ports c and d are therefore | r a c | 2 {\displaystyle |r_{ac}|^{2}} and | t a d | 2 {\displaystyle |t_{ad}|^{2}} , as might be expected. Likewise, for any input state | n m ⟩

654-401: A b {\displaystyle |nm\rangle _{ab}} and the output is Using the multi-binomial theorem , this can be written where M = n + m − N {\displaystyle M=n+m-N} and the ( n j ) {\displaystyle {\tbinom {n}{j}}} is a binomial coefficient and it is to be understood that

763-514: A c = ϕ 0 + ϕ R {\displaystyle \phi _{ad}=\phi _{0}+\phi _{T},\phi _{bc}=\phi _{0}-\phi _{T},\phi _{ac}=\phi _{0}+\phi _{R}} (and from the constraint ϕ b d = ϕ 0 − ϕ R − π {\displaystyle \phi _{bd}=\phi _{0}-\phi _{R}-\pi } ), so that where 2 ϕ T {\displaystyle 2\phi _{T}}

872-542: A d − ϕ b d + ϕ b c − ϕ a c = π {\displaystyle \phi _{ad}-\phi _{bd}+\phi _{bc}-\phi _{ac}=\pi } . To include the constraints and simplify to 4 independent parameters, we may write ϕ a d = ϕ 0 + ϕ T , ϕ b c = ϕ 0 − ϕ T , ϕ

981-434: A and E b each incident at one of the inputs, the two output fields E c and E d are linearly related to the inputs through where the 2×2 element τ {\displaystyle \tau } is the beam-splitter transfer matrix and r and t are the reflectance and transmittance along a particular path through the beam splitter, that path being indicated by the subscripts. (The values depend on

1090-417: A Mach–Zehnder interferometer . In this case there are two incoming beams, and potentially two outgoing beams. But the amplitudes of the two outgoing beams are the sums of the (complex) amplitudes calculated from each of the incoming beams, and it may result that one of the two outgoing beams has amplitude zero. In order for energy to be conserved (see next section), there must be a phase shift in at least one of

1199-423: A charge amplifier , which converts the charge into a voltage . By repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages. In a digital device, these voltages are then sampled, digitized, and usually stored in memory; in an analog device (such as an analog video camera), they are processed into a continuous analog signal (e.g. by feeding

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1308-455: A head-up display (HUD). The important difference is that the scene available to the eye is also available to the computer that projects the head-up display. This enables the EyeTap to modify the computer generated scene in response to the natural scene. One use, for instance, would be a sports EyeTap: here the wearer, while in a stadium, would be able to follow a particular player in a field and have

1417-402: A physical vapor deposition method. The thickness of the deposit is controlled so that part (typically half) of the light, which is incident at a 45-degree angle and not absorbed by the coating or substrate material, is transmitted and the remainder is reflected. A very thin half-silvered mirror used in photography is often called a pellicle mirror . To reduce loss of light due to absorption by

1526-481: A shift register . The essence of the design was the ability to transfer charge along the surface of a semiconductor from one storage capacitor to the next. The concept was similar in principle to the bucket-brigade device (BBD), which was developed at Philips Research Labs during the late 1960s. The first experimental device demonstrating the principle was a row of closely spaced metal squares on an oxidized silicon surface electrically accessed by wire bonds. It

1635-482: A CCD is the higher cost: the cell area is basically doubled, and more complex control electronics are needed. An intensified charge-coupled device (ICCD) is a CCD that is optically connected to an image intensifier that is mounted in front of the CCD. An image intensifier includes three functional elements: a photocathode , a micro-channel plate (MCP) and a phosphor screen. These three elements are mounted one close behind

1744-448: A beam as it reflects or transmits at that surface. Then we obtain Further simplifying, the relationship becomes which is true when ϕ a d − ϕ b d + ϕ b c − ϕ a c = π {\displaystyle \phi _{ad}-\phi _{bd}+\phi _{bc}-\phi _{ac}=\pi } and

1853-529: A beam-combiner in three- LCD projectors , in which light from three separate monochrome LCD displays is combined into a single full-color image for projection. Beam splitters with single-mode fiber for PON networks use the single-mode behavior to split the beam. The splitter is done by physically splicing two fibers "together" as an X. Arrangements of mirrors or prisms used as camera attachments to photograph stereoscopic image pairs with one lens and one exposure are sometimes called "beam splitters", but that

1962-665: A cooling system—using either thermoelectric cooling or liquid nitrogen—to cool the chip down to temperatures in the range of −65 to −95 °C (−85 to −139 °F). This cooling system adds additional costs to the EMCCD imaging system and may yield condensation problems in the application. However, high-end EMCCD cameras are equipped with a permanent hermetic vacuum system confining the chip to avoid condensation issues. The low-light capabilities of EMCCDs find use in astronomy and biomedical research, among other fields. In particular, their low noise at high readout speeds makes them very useful for

2071-415: A cube, a beam splitter is made from two triangular glass prisms which are glued together at their base using polyester, epoxy , or urethane-based adhesives. (Before these synthetic resins , natural ones were used, e.g. Canada balsam .) The thickness of the resin layer is adjusted such that (for a certain wavelength ) half of the light incident through one "port" (i.e., face of the cube) is reflected and

2180-428: A factor of 2–3 compared to the surface-channel CCD. The gate oxide, i.e. the capacitor dielectric , is grown on top of the epitaxial layer and substrate. Later in the process, polysilicon gates are deposited by chemical vapor deposition , patterned with photolithography , and etched in such a way that the separately phased gates lie perpendicular to the channels. The channels are further defined by utilization of

2289-555: A few percent. That image can then be read out slowly from the storage region while a new image is integrating or exposing in the active area. Frame-transfer devices typically do not require a mechanical shutter and were a common architecture for early solid-state broadcast cameras. The downside to the frame-transfer architecture is that it requires twice the silicon real estate of an equivalent full-frame device; hence, it costs roughly twice as much. The interline architecture extends this concept one step further and masks every other column of

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2398-429: A full-frame device, all of the image area is active, and there is no electronic shutter. A mechanical shutter must be added to this type of sensor or the image smears as the device is clocked or read out. With a frame-transfer CCD, half of the silicon area is covered by an opaque mask (typically aluminum). The image can be quickly transferred from the image area to the opaque area or storage region with acceptable smear of

2507-592: A gain register is placed between the shift register and the output amplifier. The gain register is split up into a large number of stages. In each stage, the electrons are multiplied by impact ionization in a similar way to an avalanche diode . The gain probability at every stage of the register is small ( P < 2%), but as the number of elements is large (N > 500), the overall gain can be very high ( g = ( 1 + P ) N {\displaystyle g=(1+P)^{N}} ), with single input electrons giving many thousands of output electrons. Reading

2616-401: A large lateral electric field from one gate to the next. This provides an additional driving force to aid in transfer of the charge packets. The CCD image sensors can be implemented in several different architectures. The most common are full-frame, frame-transfer, and interline. The distinguishing characteristic of each of these architectures is their approach to the problem of shuttering. In

2725-401: A major technology used in digital imaging . In a CCD image sensor , pixels are represented by p-doped metal–oxide–semiconductor (MOS) capacitors . These MOS capacitors , the basic building blocks of a CCD, are biased above the threshold for inversion when image acquisition begins, allowing the conversion of incoming photons into electron charges at the semiconductor-oxide interface;

2834-505: A medium with a lower refractive index. The behavior is dictated by the Fresnel equations . This does not apply to partial reflection by conductive (metallic) coatings, where other phase shifts occur in all paths (reflected and transmitted). In any case, the details of the phase shifts depend on the type and geometry of the beam splitter. For beam splitters with two incoming beams, using a classical, lossless beam splitter with electric fields E

2943-399: A non-equilibrium state called deep depletion. Then, when electron–hole pairs are generated in the depletion region, they are separated by the electric field, the electrons move toward the surface, and the holes move toward the substrate. Four pair-generation processes can be identified: The last three processes are known as dark-current generation, and add noise to the image; they can limit

3052-417: A p+ doped region underlying them, providing a further barrier to the electrons in the charge packets (this discussion of the physics of CCD devices assumes an electron transfer device, though hole transfer is possible). The clocking of the gates, alternately high and low, will forward and reverse bias the diode that is provided by the buried channel (n-doped) and the epitaxial layer (p-doped). This will cause

3161-453: A prior resource only (this setting hence shares certain similarities with a Gaussian counterpart of the KLM protocol ). The building block of this simulation procedure is the fact that a beam splitter is equivalent to a squeezing transformation under partial time reversal . Reflection beam splitters reflect parts of the incident radiation in different directions. These partial beams show exactly

3270-449: A real, practical device comes to such an ideal. EyeTaps could have great use in any field where the user would benefit from real-time interactive information that is largely visual in nature. This is sometimes referred to as computer-mediated reality , commonly known as augmented reality . Eyetap has been explored as a potential tool for individuals with visual disabilities due to its abilities to direct visual information to parts of

3379-409: A reflective material such as aluminium. When the exposure time is up, the cells are transferred very rapidly to the hidden area. Here, safe from any incoming light, cells can be read out at any speed one deems necessary to correctly measure the cells' charge. At the same time, the exposed part of the CCD is collecting light again, so no delay occurs between successive exposures. The disadvantage of such

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3488-445: A signal from a CCD gives a noise background, typically a few electrons. In an EMCCD, this noise is superimposed on many thousands of electrons rather than a single electron; the devices' primary advantage is thus their negligible readout noise. The use of avalanche breakdown for amplification of photo charges had already been described in the U.S. patent 3,761,744 in 1973 by George E. Smith/Bell Telephone Laboratories. EMCCDs show

3597-422: A similar sensitivity to intensified CCDs (ICCDs). However, as with ICCDs, the gain that is applied in the gain register is stochastic and the exact gain that has been applied to a pixel's charge is impossible to know. At high gains (> 30), this uncertainty has the same effect on the signal-to-noise ratio (SNR) as halving the quantum efficiency (QE) with respect to operation with a gain of unity. This effect

3706-416: A single slice of the image, whereas a two-dimensional array, used in video and still cameras, captures a two-dimensional picture corresponding to the scene projected onto the focal plane of the sensor. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor (operating as a shift register). The last capacitor in the array dumps its charge into

3815-494: A symmetric beam splitter ϕ 0 = ϕ T = 0 , ϕ R = π / 2 {\displaystyle \phi _{0}=\phi _{T}=0,\phi _{R}=\pi /2} ), and for other phases where the output goes to one arm (e.g. the dielectric beam splitter ϕ 0 = ϕ T = ϕ R = 0 {\displaystyle \phi _{0}=\phi _{T}=\phi _{R}=0} )

3924-424: A time. During the readout phase, cells are shifted down the entire area of the CCD. While they are shifted, they continue to collect light. Thus, if the shifting is not fast enough, errors can result from light that falls on a cell holding charge during the transfer. These errors are referred to as "vertical smear" and cause a strong light source to create a vertical line above and below its exact location. In addition,

4033-464: A variety of astronomical applications involving low light sources and transient events such as lucky imaging of faint stars, high speed photon counting photometry, Fabry-Pérot spectroscopy and high-resolution spectroscopy. More recently, these types of CCDs have broken into the field of biomedical research in low-light applications including small animal imaging , single-molecule imaging , Raman spectroscopy , super resolution microscopy as well as

4142-477: A very literally "half-silvered" surface. Instead of a metallic coating, a dichroic optical coating may be used. Depending on its characteristics ( thin-film interference ), the ratio of reflection to transmission will vary as a function of the wavelength of the incident light. Dichroic mirrors are used in some ellipsoidal reflector spotlights to split off unwanted infrared (heat) radiation, and as output couplers in laser construction . A third version of

4251-563: Is a misnomer, as they are effectively a pair of periscopes redirecting rays of light which are already non-coincident. In some very uncommon attachments for stereoscopic photography, mirrors or prism blocks similar to beam splitters perform the opposite function, superimposing views of the subject from two different perspectives through color filters to allow the direct production of an anaglyph 3D image, or through rapidly alternating shutters to record sequential field 3D video. Beam splitters are sometimes used to recombine beams of light, as in

4360-410: Is a photoactive region (an epitaxial layer of silicon), and a transmission region made out of a shift register (the CCD, properly speaking). An image is projected through a lens onto the capacitor array (the photoactive region), causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A one-dimensional array, used in line-scan cameras, captures

4469-430: Is a simplified version of Ref. The relation between the classical field amplitudes E a , E b , E c {\displaystyle {E}_{a},{E}_{b},{E}_{c}} , and E d {\displaystyle {E}_{d}} produced by the beam splitter is translated into the same relation of the corresponding quantum creation (or annihilation) operators

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4578-432: Is a specialized CCD, often used in astronomy and some professional video cameras , designed for high exposure efficiency and correctness. The normal functioning of a CCD, astronomical or otherwise, can be divided into two phases: exposure and readout. During the first phase, the CCD passively collects incoming photons , storing electrons in its cells. After the exposure time is passed, the cells are read out one line at

4687-483: Is an essential component in this scheme since it is the only one that creates entanglement between the Fock states . Similar settings exist for continuous-variable quantum information processing . In fact, it is possible to simulate arbitrary Gaussian (Bogoliubov) transformations of a quantum state of light by means of beam splitters, phase shifters and photodetectors, given two-mode squeezed vacuum states are available as

4796-849: Is given in the Fearn–Loudon 1987 paper and extended in Ref to include statistical mixtures with the density matrix . In general, for a non-symmetric beam-splitter, namely a beam-splitter for which the transmission and reflection coefficients are not equal, one can define an angle θ {\displaystyle \theta } such that { | R | = sin ⁡ ( θ ) | T | = cos ⁡ ( θ ) {\displaystyle {\begin{cases}|R|=\sin(\theta )\\|T|=\cos(\theta )\end{cases}}} where R {\displaystyle R} and T {\displaystyle T} are

4905-557: Is one of the major advantages of the ICCD over the EMCCD cameras. The highest performing ICCD cameras enable shutter times as short as 200 picoseconds . ICCD cameras are in general somewhat higher in price than EMCCD cameras because they need the expensive image intensifier. On the other hand, EMCCD cameras need a cooling system to cool the EMCCD chip down to temperatures around 170  K (−103  °C ). This cooling system adds additional costs to

5014-446: Is possible to create a universal quantum computer solely with beam splitters, phase shifters, photodetectors and single photon sources. The states that form a qubit in this protocol are the one-photon states of two modes, i.e. the states |01⟩ and |10⟩ in the occupation number representation ( Fock state ) of two modes. Using these resources it is possible to implement any single qubit gate and 2-qubit probabilistic gates. The beam splitter

5123-765: Is produced when θ = π / 4 {\displaystyle \theta =\pi /4} . The dielectric beam splitter above, for example, has i.e. ϕ T = ϕ R = ϕ 0 = 0 {\displaystyle \phi _{T}=\phi _{R}=\phi _{0}=0} , while the "symmetric" beam splitter of Loudon has i.e. ϕ T = 0 , ϕ R = − π / 2 , ϕ 0 = π / 2 {\displaystyle \phi _{T}=0,\phi _{R}=-\pi /2,\phi _{0}=\pi /2} . Beam splitters have been used in both thought experiments and real-world experiments in

5232-555: Is referred to as the Excess Noise Factor (ENF). However, at very low light levels (where the quantum efficiency is most important), it can be assumed that a pixel either contains an electron—or not. This removes the noise associated with the stochastic multiplication at the risk of counting multiple electrons in the same pixel as a single electron. To avoid multiple counts in one pixel due to coincident photons in this mode of operation, high frame rates are essential. The dispersion in

5341-404: Is reflected into the eye to be superimposed on the original scene. Stereo EyeTaps modify light passing through both eyes, but many research prototypes (mainly for reasons of ease of construction) only tap one eye. EyeTap is also the name of an organization founded by inventor Steve Mann to develop and promote EyeTap-related technologies such as wearable computers . An EyeTap is somewhat like

5450-433: Is the identity, i.e. the beam-splitter transfer matrix is a unitary matrix . Each r and t can be written as a complex number having an amplitude and phase factor; for instance, r a c = | r a c | e i ϕ a c {\displaystyle r_{ac}=|r_{ac}|e^{i\phi _{ac}}} . The phase factor accounts for possible shifts in phase of

5559-734: Is the phase difference between the transmitted beams and similarly for 2 ϕ R {\displaystyle 2\phi _{R}} , and ϕ 0 {\displaystyle \phi _{0}} is a global phase. Lastly using the other constraint that R 2 + T 2 = 1 {\displaystyle R^{2}+T^{2}=1} we define θ = arctan ⁡ ( R / T ) {\displaystyle \theta =\arctan(R/T)} so that T = cos ⁡ θ , R = sin ⁡ θ {\displaystyle T=\cos \theta ,R=\sin \theta } , hence A 50:50 beam splitter

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5668-512: Is the probability of getting n output electrons given m input electrons and a total mean multiplication register gain of g . For very large numbers of input electrons, this complex distribution function converges towards a Gaussian. Because of the lower costs and better resolution, EMCCDs are capable of replacing ICCDs in many applications. ICCDs still have the advantage that they can be gated very fast and thus are useful in applications like range-gated imaging . EMCCD cameras indispensably need

5777-422: Is the right choice. Consumer snap-shot cameras have used interline devices. On the other hand, for those applications that require the best possible light collection and issues of money, power and time are less important, the full-frame device is the right choice. Astronomers tend to prefer full-frame devices. The frame-transfer falls in between and was a common choice before the fill-factor issue of interline devices

5886-405: Is used in the construction of interline-transfer devices. Another version of CCD is called a peristaltic CCD. In a peristaltic charge-coupled device, the charge-packet transfer operation is analogous to the peristaltic contraction and dilation of the digestive system . The peristaltic CCD has an additional implant that keeps the charge away from the silicon/ silicon dioxide interface and generates

5995-671: The Kodak Apparatus Division, invented a digital still camera using this same Fairchild 100 × 100 CCD in 1975. The interline transfer (ILT) CCD device was proposed by L. Walsh and R. Dyck at Fairchild in 1973 to reduce smear and eliminate a mechanical shutter . To further reduce smear from bright light sources, the frame-interline-transfer (FIT) CCD architecture was developed by K. Horii, T. Kuroda and T. Kunii at Matsushita (now Panasonic) in 1981. The first KH-11 KENNEN reconnaissance satellite equipped with charge-coupled device array ( 800 × 800 pixels) technology for imaging

6104-558: The LOCOS process to produce the channel stop region. Channel stops are thermally grown oxides that serve to isolate the charge packets in one column from those in another. These channel stops are produced before the polysilicon gates are, as the LOCOS process utilizes a high-temperature step that would destroy the gate material. The channel stops are parallel to, and exclusive of, the channel, or "charge carrying", regions. Channel stops often have

6213-473: The photodiode to the CCD. This led to their invention of the pinned photodiode, a photodetector structure with low lag, low noise , high quantum efficiency and low dark current . It was first publicly reported by Teranishi and Ishihara with A. Kohono, E. Oda and K. Arai in 1982, with the addition of an anti-blooming structure. The new photodetector structure invented at NEC was given the name "pinned photodiode" (PPD) by B.C. Burkey at Kodak in 1984. In 1987,

6322-399: The CCD cannot be used to collect light while it is being read out. A faster shifting requires a faster readout, and a faster readout can introduce errors in the cell charge measurement, leading to a higher noise level. A frame transfer CCD solves both problems: it has a shielded, not light sensitive, area containing as many cells as the area exposed to light. Typically, this area is covered by

6431-402: The CCD concept. Michael Tompsett was awarded the 2010 National Medal of Technology and Innovation , for pioneering work and electronic technologies including the design and development of the first CCD imagers. He was also awarded the 2012 IEEE Edison Medal for "pioneering contributions to imaging devices including CCD Imagers, cameras and thermal imagers". In a CCD for capturing images, there

6540-473: The CCD is then used to read out these charges. Although CCDs are not the only technology to allow for light detection, CCD image sensors are widely used in professional, medical, and scientific applications where high-quality image data are required. In applications with less exacting quality demands, such as consumer and professional digital cameras , active pixel sensors , also known as CMOS sensors (complementary MOS sensors), are generally used. However,

6649-545: The CCD to deplete, near the p–n junction and will collect and move the charge packets beneath the gates—and within the channels—of the device. CCD manufacturing and operation can be optimized for different uses. The above process describes a frame transfer CCD. While CCDs may be manufactured on a heavily doped p++ wafer it is also possible to manufacture a device inside p-wells that have been placed on an n-wafer. This second method, reportedly, reduces smear, dark current , and infrared and red response. This method of manufacture

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6758-473: The CCD-G5, was released by Sony in 1983, based on a prototype developed by Yoshiaki Hagiwara in 1981. Early CCD sensors suffered from shutter lag . This was largely resolved with the invention of the pinned photodiode (PPD). It was invented by Nobukazu Teranishi , Hiromitsu Shiraki and Yasuo Ishihara at NEC in 1980. They recognized that lag can be eliminated if the signal carriers could be transferred from

6867-404: The EMCCD camera and often yields heavy condensation problems in the application. ICCDs are used in night vision devices and in various scientific applications. An electron-multiplying CCD (EMCCD, also known as an L3Vision CCD, a product commercialized by e2v Ltd., GB, L3CCD or Impactron CCD, a now-discontinued product offered in the past by Texas Instruments) is a charge-coupled device in which

6976-411: The EyeTap display statistics relevant to that player as a floating box above the player. Another practical use for the EyeTap would be in a construction yard as it would allow the user to reference the blueprints, especially in a 3D manner, to the current state of the building, display a list of current materials and their current locations as well perform basic measurements. Or, even in the business world,

7085-434: The EyeTap has great potential, for it would be capable of delivering to the user constant up to date information on the stock market, the user's corporation, and meeting statuses. On a more day-to-day basis some of Steve Mann's first uses for the technology was using it to keep track of names of people and places, his to-do lists, and keeping track of his other daily ordeals. The EyeTap Criteria are an attempt to define how close

7194-593: The PPD began to be incorporated into most CCD devices, becoming a fixture in consumer electronic video cameras and then digital still cameras . Since then, the PPD has been used in nearly all CCD sensors and then CMOS sensors . In January 2006, Boyle and Smith were awarded the National Academy of Engineering Charles Stark Draper Prize , and in 2009 they were awarded the Nobel Prize for Physics for their invention of

7303-455: The area of quantum theory and relativity theory and other fields of physics . These include: In quantum mechanics, the electric fields are operators as explained by second quantization and Fock states . Each electrical field operator can further be expressed in terms of modes representing the wave behavior and amplitude operators, which are typically represented by the dimensionless creation and annihilation operators . In this theory,

7412-451: The array's dark current , improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths. Professional observatories often cool their detectors with liquid nitrogen to reduce the dark current, and therefore the thermal noise , to negligible levels. The frame transfer CCD imager was the first imaging structure proposed for CCD Imaging by Michael Tompsett at Bell Laboratories. A frame transfer CCD

7521-402: The beam splitter is a dichroic mirrored prism assembly which uses dichroic optical coatings to divide an incoming light beam into a number of spectrally distinct output beams. Such a device was used in three-pickup-tube color television cameras and the three-strip Technicolor movie camera. It is currently used in modern three-CCD cameras. An optically similar system is used in reverse as

7630-426: The channel in which the photogenerated charge packets will travel. Simon Sze details the advantages of a buried-channel device: This thin layer (= 0.2–0.3 micron) is fully depleted and the accumulated photogenerated charge is kept away from the surface. This structure has the advantages of higher transfer efficiency and lower dark current, from reduced surface recombination. The penalty is smaller charge capacity, by

7739-447: The charge could be stepped along from one to the next. This led to the invention of the charge-coupled device by Boyle and Smith in 1969. They conceived of the design of what they termed, in their notebook, "Charge 'Bubble' Devices". The initial paper describing the concept in April 1970 listed possible uses as memory , a delay line, and an imaging device. The device could also be used as

7848-437: The coefficient is zero if j ∉ { 0 , n } {\displaystyle j\notin \{0,n\}} etc. The transmission/reflection coefficient factor in the last equation may be written in terms of the reduced parameters that ensure unitarity: where it can be seen that if the beam splitter is 50:50 then tan ⁡ θ = 1 {\displaystyle \tan \theta =1} and

7957-475: The constraints describing a lossless beam splitter, the initial expression can be rewritten as Applying different values for the amplitudes and phases can account for many different forms of the beam splitter that can be seen widely used. The transfer matrix appears to have 6 amplitude and phase parameters, but it also has 2 constraints: R 2 + T 2 = 1 {\displaystyle R^{2}+T^{2}=1} and ϕ

8066-527: The exponential term reduces to -1. Applying this new condition and squaring both sides, it becomes where substitutions of the form | r a c | 2 = 1 − | t a d | 2 {\displaystyle |r_{ac}|^{2}=1-|t_{ad}|^{2}} were made. This leads to the result and similarly, It follows that R 2 + T 2 = 1 {\displaystyle R^{2}+T^{2}=1} . Having determined

8175-404: The first version of the EyeTap, which consisted of a computer in a backpack wired up to a camera and its viewfinder which in turn was rigged to a helmet. Ever since this first version, it has gone through multiple models as wearable computing evolves, allowing the EyeTap to shrink down to a smaller and less weighty version. Currently the EyeTap consists of the eyepiece used to display the images,

8284-450: The four ports of the beam splitter are represented by a photon number state | n ⟩ {\displaystyle |n\rangle } and the action of a creation operation is a ^ † | n ⟩ = n + 1 | n + 1 ⟩ {\displaystyle {\hat {a}}^{\dagger }|n\rangle ={\sqrt {n+1}}|n+1\rangle } . The following

8393-819: The gain is shown in the graph on the right. For multiplication registers with many elements and large gains it is well modelled by the equation: P ( n ) = ( n − m + 1 ) m − 1 ( m − 1 ) ! ( g − 1 + 1 m ) m exp ⁡ ( − n − m + 1 g − 1 + 1 m )  if  n ≥ m {\displaystyle P\left(n\right)={\frac {\left(n-m+1\right)^{m-1}}{\left(m-1\right)!\left(g-1+{\frac {1}{m}}\right)^{m}}}\exp \left(-{\frac {n-m+1}{g-1+{\frac {1}{m}}}}\right)\quad {\text{ if }}n\geq m} where P

8502-506: The image sensor for storage. In this device, only one pixel shift has to occur to transfer from image area to storage area; thus, shutter times can be less than a microsecond and smear is essentially eliminated. The advantage is not free, however, as the imaging area is now covered by opaque strips dropping the fill factor to approximately 50 percent and the effective quantum efficiency by an equivalent amount. Modern designs have addressed this deleterious characteristic by adding microlenses on

8611-444: The image to the aremac, a display device capable of displaying data at any fitting depth. The output rays from the aremac are reflected off the half-silvered mirror back into the eye of the user along with the original light rays. In these cases, the EyeTap views infrared light, as well as the overall design schematic of how the EyeTap manipulates lightrays. A conceptual diagram of an EyeTap: CCD Cameras ( Charge-coupled device ) are

8720-497: The incident light. Most common types of CCDs are sensitive to near-infrared light, which allows infrared photography , night-vision devices, and zero lux (or near zero lux) video-recording/photography. For normal silicon-based detectors, the sensitivity is limited to 1.1 μm. One other consequence of their sensitivity to infrared is that infrared from remote controls often appears on CCD-based digital cameras or camcorders if they do not have infrared blockers. Cooling reduces

8829-467: The invention and began development programs. Fairchild's effort, led by ex-Bell researcher Gil Amelio, was the first with commercial devices, and by 1974 had a linear 500-element device and a 2D 100 × 100 pixel device. Peter Dillon, a scientist at Kodak Research Labs, invented the first color CCD image sensor by overlaying a color filter array on this Fairchild 100 x 100 pixel Interline CCD starting in 1974. Steven Sasson , an electrical engineer working for

8938-454: The keypad which the user can use to interface with the EyeTap and have it perform the desired tasks, a CPU which can be attached to most articles of clothing and in some cases even a Wi-Fi device so the user can access the Internet and online data . The EyeTap is essentially a half-silvered mirror in front of the user's eye, reflecting some of the light into a sensor. The sensor then sends

9047-431: The large quality advantage CCDs enjoyed early on has narrowed over time and since the late 2010s CMOS sensors are the dominant technology, having largely if not completely replaced CCD image sensors. The basis for the CCD is the metal–oxide–semiconductor (MOS) structure, with MOS capacitors being the basic building blocks of a CCD, and a depleted MOS structure used as the photodetector in early CCD devices. In

9156-411: The late 1960s, Willard Boyle and George E. Smith at Bell Labs were researching MOS technology while working on semiconductor bubble memory . They realized that an electric charge was the analogy of the magnetic bubble and that it could be stored on a tiny MOS capacitor. As it was fairly straightforward to fabricate a series of MOS capacitors in a row, they connected a suitable voltage to them so that

9265-412: The most common type of digital camera used today. Beam splitter A beam splitter or beamsplitter is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers , also finding widespread application in fibre optic telecommunications . In its most common form,

9374-464: The multiplied electrons back to photons which are guided to the CCD by a fiber optic or a lens. An image intensifier inherently includes a shutter functionality: If the control voltage between the photocathode and the MCP is reversed, the emitted photoelectrons are not accelerated towards the MCP but return to the photocathode. Thus, no electrons are multiplied and emitted by the MCP, no electrons are going to

9483-383: The only factor that depends on j is the ( − 1 ) j {\displaystyle (-1)^{j}} term. This factor causes interesting interference cancellations. For example, if n = m {\displaystyle n=m} and the beam splitter is 50:50, then where the a ^ c †

9592-558: The other half is transmitted due to FTIR (frustrated total internal reflection) . Polarizing beam splitters , such as the Wollaston prism , use birefringent materials to split light into two beams of orthogonal polarization states. Another design is the use of a half-silvered mirror. This is composed of an optical substrate, which is often a sheet of glass or plastic, with a partially transparent thin coating of metal. The thin coating can be aluminium deposited from aluminium vapor using

9701-413: The other in the mentioned sequence. The photons which are coming from the light source fall onto the photocathode, thereby generating photoelectrons. The photoelectrons are accelerated towards the MCP by an electrical control voltage, applied between photocathode and MCP. The electrons are multiplied inside of the MCP and thereafter accelerated towards the phosphor screen. The phosphor screen finally converts

9810-409: The outgoing beams. For example (see red arrows in picture on the right), if a polarized light wave in air hits a dielectric surface such as glass, and the electric field of the light wave is in the plane of the surface, then the reflected wave will have a phase shift of π, while the transmitted wave will not have a phase shift; the blue arrow does not pick up a phase-shift, because it is reflected from

9919-570: The output is always in the same arm, not random in either arm as is the case here. From the correspondence principle we might expect the quantum results to tend to the classical one in the limits of large n , but the appearance of large numbers of indistinguishable photons at the input is a non-classical state that does not correspond to a classical field pattern, which instead produces a statistical mixture of different | n , m ⟩ {\displaystyle |n,m\rangle } known as Poissonian light . Rigorous derivation

10028-491: The output of the CCD, and this must be taken into consideration in satellites using CCDs. The photoactive region of a CCD is, generally, an epitaxial layer of silicon . It is lightly p doped (usually with boron ) and is grown upon a substrate material, often p++. In buried-channel devices, the type of design utilized in most modern CCDs, certain areas of the surface of the silicon are ion implanted with phosphorus , giving them an n-doped designation. This region defines

10137-447: The output of the charge amplifier into a low-pass filter), which is then processed and fed out to other circuits for transmission, recording, or other processing. Before the MOS capacitors are exposed to light, they are biased into the depletion region; in n-channel CCDs, the silicon under the bias gate is slightly p -doped or intrinsic. The gate is then biased at a positive potential, above

10246-407: The phosphor screen and no light is emitted from the image intensifier. In this case no light falls onto the CCD, which means that the shutter is closed. The process of reversing the control voltage at the photocathode is called gating and therefore ICCDs are also called gateable CCD cameras. Besides the extremely high sensitivity of ICCD cameras, which enable single photon detection, the gateability

10355-445: The polarization of the light.) If the beam splitter removes no energy from the light beams, the total output energy can be equated with the total input energy, reading Inserting the results from the transfer equation above with E b = 0 {\displaystyle E_{b}=0} produces and similarly for then E a = 0 {\displaystyle E_{a}=0} When both E

10464-405: The probability of output with a photon in each mode (a coincidence event) is zero. Note that this is true for all types of 50:50 beam splitter irrespective of the details of the phases, and the photons need only be indistinguishable. This contrasts with the classical result, in which equal output in both arms for equal inputs on a 50:50 beam splitter does appear for specific beam splitter phases (e.g.

10573-642: The reflection and transmission coefficients. Then the unitary operation associated with the beam-splitter is then U ^ = e i θ ( a ^ a † a ^ b + a ^ a a ^ b † ) . {\displaystyle {\hat {U}}=e^{i\theta \left({\hat {a}}_{a}^{\dagger }{\hat {a}}_{b}+{\hat {a}}_{a}{\hat {a}}_{b}^{\dagger }\right)}.} In 2000 Knill, Laflamme and Milburn ( KLM protocol ) proved that it

10682-399: The reflective coating, so-called " Swiss-cheese " beam-splitter mirrors have been used. Originally, these were sheets of highly polished metal perforated with holes to obtain the desired ratio of reflection to transmission. Later, metal was sputtered onto glass so as to form a discontinuous coating, or small areas of a continuous coating were removed by chemical or mechanical action to produce

10791-443: The retina that function well. As well, Eyetap's role in sousveillance has been explored by Mann, Jason Nolan and Barry Wellman . Users may find that they experience side effects such as headaches and difficulty sleeping if usage occurs shortly before sleep. Mann finds that due to his extensive use of the device that going without it can cause him to feel "nauseous, unsteady, naked" when he removes it. The EyeTap has applications in

10900-407: The same intensity. Typically, reflection beam splitters are made of metal and have a broadband spectral characteristic. Charge-coupled device A charge-coupled device ( CCD ) is an integrated circuit containing an array of linked, or coupled, capacitors . Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are

11009-406: The surface of the device to direct light away from the opaque regions and on the active area. Microlenses can bring the fill factor back up to 90 percent or more depending on pixel size and the overall system's optical design. The choice of architecture comes down to one of utility. If the application cannot tolerate an expensive, failure-prone, power-intensive mechanical shutter, an interline device

11118-407: The threshold for strong inversion, which will eventually result in the creation of an n channel below the gate as in a MOSFET . However, it takes time to reach this thermal equilibrium: up to hours in high-end scientific cameras cooled at low temperature. Initially after biasing, the holes are pushed far into the substrate, and no mobile electrons are at or near the surface; the CCD thus operates in

11227-456: The total usable integration time. The accumulation of electrons at or near the surface can proceed either until image integration is over and charge begins to be transferred, or thermal equilibrium is reached. In this case, the well is said to be full. The maximum capacity of each well is known as the well depth, typically about 10 electrons per pixel. CCDs are normally susceptible to ionizing radiation and energetic particles which causes noise in

11336-418: The transfer matrix is given in classical lossless beam splitter section above: Since τ {\displaystyle \tau } is unitary, τ − 1 = τ † {\displaystyle \tau ^{-1}=\tau ^{\dagger }} , i.e. This is equivalent to saying that if we start from the vacuum state | 00 ⟩

11445-493: The world of cyborg logging, as it allows the user the ability to perform real-time visual capture of their daily lives from their own point of view. In this way, the EyeTap could be used to create a lifelong cyborg log or “glog” of the user's life and the events they participate in, potentially recording enough media to allow producers centuries in the future to present the user's life as interactive entertainment (or historical education) to consumers of that era. Steve Mann created

11554-550: Was a simple 8-bit shift register, reported by Tompsett, Amelio and Smith in August 1970. This device had input and output circuits and was used to demonstrate its use as a shift register and as a crude eight pixel linear imaging device. Development of the device progressed at a rapid rate. By 1971, Bell researchers led by Michael Tompsett were able to capture images with simple linear devices. Several companies, including Fairchild Semiconductor , RCA and Texas Instruments , picked up on

11663-479: Was addressed. Today, frame-transfer is usually chosen when an interline architecture is not available, such as in a back-illuminated device. CCDs containing grids of pixels are used in digital cameras , optical scanners , and video cameras as light-sensing devices. They commonly respond to 70 percent of the incident light (meaning a quantum efficiency of about 70 percent) making them far more efficient than photographic film , which captures only about 2 percent of

11772-450: Was demonstrated by Gil Amelio , Michael Francis Tompsett and George Smith in April 1970. This was the first experimental application of the CCD in image sensor technology, and used a depleted MOS structure as the photodetector. The first patent ( U.S. patent 4,085,456 ) on the application of CCDs to imaging was assigned to Tompsett, who filed the application in 1971. The first working CCD made with integrated circuit technology

11881-466: Was launched in December 1976. Under the leadership of Kazuo Iwama , Sony started a large development effort on CCDs involving a significant investment. Eventually, Sony managed to mass-produce CCDs for their camcorders . Before this happened, Iwama died in August 1982. Subsequently, a CCD chip was placed on his tombstone to acknowledge his contribution. The first mass-produced consumer CCD video camera ,

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