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  • 8/10/2019 Camcorder - CTS references


    A camcorderis a portable consumer electronicsdevice for recording video

    and audiousing a built-in recorder unit. The camcorder contains both a video

    cameraand a video recorderin one unit, hence its compound name. This

    compares to previous technology where an acquisition and recording devices

    would be separate.

    The earliest camcorders, developed by companies such as JVC, ony, and

    !oda", used analog videotape. ince the #$$%s recording onto digital tape

    has become the norm. tarting from early &%%%s tape as storage media is

    being gradually replaced with tape-free solutions li"e optical dis"s, hard dis"

    drives and solid-state memory.

    All tape-based camcorders have removable media in form of video cassettes.

    olid-state camcorders can have either removable media in form of memory

    cards, or built-in memory, or both. '((-based camcorders usually have non-

    removable media in form of a hard dis" drive.

    Camcorders that do not use magnetic tape are often called tapeless

    camcorders. Camcorders that use two different types of media, li"e built-in

    '(( and memory card, are often called hybrid camcorders.


    )efore the camcorder. This separate portable )etama*recorder and camera

    arrangement slightly predates the first camcorders

    Video cameras were originally designed for broadcastingtelevisionimages +

    see television camera. Cameras found in television broadcast centres were

    e*tremely large, mounted on special trolleys, and wired to remote recorders

    located in separate rooms. As technology advanced, miniaturiation
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    5ithin a short time JVC released its own camcorder using its pre-e*isting

    V'-C format. The V'-C cassette held enough tape to record ?% or #&%

    minutes of V' video, while a mechanical adapter enabled playbac" of V'-

    C videocassettes in home VC/s. This first model can be seen in the movie

    Back to the Future.@#After seeing the popularity of the small V'-C7palmcorders7, ony redesigned its )etama* system to create the Video;

    standard. Video; eliminated the problem of short running time, by using an

    all-new metal composition video cassette. ; mm video used a tape whose

    width is ==B less than V'4)etama* tape 0#&.D mm1, allowing even further

    miniaturiation in the recorder9s tape-transport assembly and cassette media.

    )oth V'-C and ; mm video represented a trade-off for the consumer.

    Although the Video; and 'i; camcorders produced quality equal to V'-C

    and uper V'-C camcorders 0&E%4?&% lines horiontal1, the standard ; mmcassette had the advantage with up to two hours length 0four hours in slow

    mode1. Fn the down side, since the ; mm format was incompatible with V',

    ; mm recordings could not be played in consumers9 V' VC/s. Gqually

    important entry-level V'-C camcorders were priced less than ; mm units,

    and thus neither 7won7 the war. :t became a stalemate. 0ide note - :n #$;8

    companies li"e anasonicbegan releasing full-sied V'4-V'

    camcorders, which offered up to = or $ hours record time, and thus found a

    niche with videophiles, industrial videographers, and college TV studios.1

    :n the mid-#$$%s, the camcorder reached the digitalera with the introduction

    of (V and mini(V. :ts cassette media was even smaller than ; mm media,

    allowing another sie reduction of the tape transport assembly. The digital

    nature of mini(V also improved audio and video quality over the best of the

    analog consumer camcorders 0V'-C, 'i;1, although some users still prefer

    the analog nature of 'i; and uper V'-C, since neither of these produce

    the 7bac"ground blur7 or 7mosquito noise7 of (igital compression. Variations

    on the (V camcorder include the (igital;camcorder and the >GH&-based


    The evolution of the camcorder has seen the growth of the camcorder mar"et

    as price reductions and sie reductions ma"e the technology more accessible

    to a wider audience. 5hen camcorders were first introduced, they were bul"y

    shoulder-operated luggables that cost over I#,E%% 2 dollars @citation needed.As of
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    &%%;, an entry-level camcorders fit in the palm of a person9s hand and is sold

    at a retail price of appro*imately I#%% 2 dollars


    Major components

    Camcorders contain = ma6or components lens, imager, and recorder. The

    lens gathers and focuses light on the imager. The imager 0usually a CC(or

    C>Fsensor on modern camcorders< earlier e*amples often used vidicon

    tubes1 converts incident light into an electrical 0video1 signal. inally, the

    recorder encodes the video signal into a storable form. >ore commonly, the

    optics and imager are referred to as the camerasection.

    The lensis the first component in the camera-section9s 7light-path7. The

    camcorder9s optics generally have one or more of the following ad6ustments

    aperture 0to control the amount of light1, oom 0to control the field-of-view1,

    and shutter speed 0to capture continuous motion.1 :n consumer units, these

    ad6ustments are automatically controlled by the camcorder9s electronics,

    generally to maintain constant exposureonto the imager. rofessional units

    offer direct user control of all ma6or optical functions 0aperture, shutter-speed,

    focus, etc.1

    The imagersection is the eyeof the camcorder, housing a photosensitive

    device0s1. The imager converts light into an electronic video-signal through an

    elaborate electronic process. The camera lens pro6ects an image onto the

    imager surface, e*posing the photosensitive array to light. The light e*posure

    is converted into electrical charge. At the end of the timed e*posure, the

    imager converts the accumulated charge into a continuous analog voltage at

    the imager9s output terminals. After scan-out is complete, the photosites are

    reset to start the e*posure-process for the ne*t video frame. :n modern

    0digital1 camcorders, an analog-to-digital 0A(C1 converter digities the imager

    0analog1 waveform output into a discrete digital-video signal.The third section, the recorder, is responsible for writing the video-signal onto

    a recording medium 0such as magnetic videotape.1 The record function

    involves many signal-processing steps, and historically, the recording-process

    introduced some distortion and noise into the stored video, such that playbac"
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    of the stored-signal may not retain the same characteristics4detail as the live

    video feed.

    All but the most primitive camcorders imaginable also need to have a

    recorder-controlling section which allows the user to control the camcorder,

    switch the recorder into playbac" mode for reviewing the recorded footage

    and an image control section which controls e*posure, focus and white-


    The image recorded need not be limited to what appeared in the viewfinder.

    or documentation of events, such as used by police, the field of view

    overlays such things as the time and date of the recording along the top and

    bottom of the image. uch things as the police car or constable to which the

    recorder has been allotted may also appear< also the speed of the car at the

    time of recording. Compass direction at time of recording and geographical

    coordinates may also be possible. These are not "ept to world-standard fieldsini(V storage allows full resolution video 0D&%*ED8for AL,D&%*?;% for KTC1, unli"e previous analogue video standards. (igital

    video doesn9t e*perience colour bleeding, 6itter, or fade, although some users

    still prefer the analog nature of 'i; and uper V'-C, since neither of these

    produce the 7bac"ground blur7 or 7mosquito noise7 of (igital compression. :n

    many cases, a high-quality analog recording shows more detail 0such as
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    rough te*tures on a wall1 than a compressed digital recording 0which would

    show the same wall as flat and featureless1.

    The highest-quality digital formats, such as >ini(V and (igital )etacam, have

    the advantage over analog of suffering little generation lossin recording,

    dubbing, and editing 0>GH-& and >GH-? do suffer from generation loss in

    the editing process only1. 5hereas noiseand bandwidthissues relating to

    cables, amplifiers, and mi*erscan greatly affect analog recordings, such

    problems are minimal in digital formats using digital connections 0generally

    :GGG #=$?, (:4(T:, or '(>:1.

    Although both analog and digital can suffer from archival problems, digital is

    more prone to complete loss. Theoretically digital information can be stored

    indefinitely with ero deterioration on a digital storage device 0such as a hard

    drive1, however since some digital formats 0li"e mini(V1 often squeee trac"s

    only #% micrometers apart 0versus E%% Mm for V'1, a digital recording is

    more vulnerable to wrin"les or stretches in the tape that could permanently

    erase several scenes worth of digital data. Fn analog media similar damage

    barely registers as 7noise7 in the video, still leaving a deteriorated but

    watchable video. Gven digital recordings on (V( are "nown to suffer from

    (V( rotthat permanently erase huge chun"s of data. Thus the one

    advantage analog seems to have in this respect is that an analog recording

    may be 7usable7 even after the media it is stored on has suffered severedeterioration whereas it has been noticed@#that even slight media

    degradation in digital recordings may cause them to suffer from an 7all or

    nothing7 failure, i.e. the digital recording will end up being totally un-playable

    without very e*pensive restoration wor".

    Modern recording media

    For more information, see tapeless camcorder.

    ome recent camcorders record video on flash memorydevices, >icrodrives,

    small hard dis"s, and sie-reduced (V(-/A>or (V(-/susing >GH-#,

    >GH-&or >GH-?formats. 'owever because these codecs use inter-frame

    compression, frame-specific-editing requires frame regeneration, which incurs

    additional processing and can cause loss of picture information. 0:n

    professional usage, it is common to use a codec that will store every frame

    inidividually. This provides easier and faster frame-specific editing of scenes.1
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    >ost other digital consumer camcorders record in (Vor '(Vformat on tape

    and transfer content over ire5ire0some also use 2) &.%1 to a computer,

    where the huge files 0for (V, #H) for ? to ?.8 minutes in AL4KTC

    resolutions1 can be edited, converted, and 0with many camcorders1 also

    recorded bac" to tape. The transfer is done in real time, so the completetransfer of a 8% minute tape needs one hour to transfer and about #=H) dis"

    space for the raw footage only - e*cluding any space needed for render files,

    and other media. Time spent in post-production 0editing1 to select and cut the

    best shots varies from instantaneous 7magic7 movies to hours of tedious

    selection, arrangement and rendering.

    Consumer market

    As the mainstream consumer mar"et favors ease of use, portability, and price,

    consumer camcorders emphasie these features more than raw technical

    performance. or e*ample, good low-light capabilities require large capturing

    chips, which affects price and sie. Thus, consumer camcorders are often

    unable to shoot useful footage in dim light 0though some units, particularly

    single-chip units by ony, offer night visioncapability1. >anual controls need

    space, either in menus or as buttons and ma"e the use more complicated,

    which goes against the requirement of ease of use. Consumer units offer a

    plethora of :4F options 0:GGG #=$?4irewire, 2) &.%, Composite and -

    Video1, but lac" many manual settings, often e*cluding video e*posure, gaincontrol, or sound level management. or the beginner, entry-level camcorders

    offer basic recording and playbac" capability.

    or the sophisticated hobbyist, high-end units offer improved optical and video

    performance through multi-CC( components and name-brand optics, manual

    control of camera e*posure, and more, but even consumer camcorders which

    are sold for I#%%% such as the anasonic H&E% are not well-suited for

    recording in dim light. 5hen dimly-lit areas are brightened in-camera or in

    post-production, considerable noise distracts the viewer.
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    JVC HN->HEEE hybrid camcorder 0>GH-& (-Video1

    )efore the st century, consumer video editing was a difficult tas" requiring a

    minimum of two recorders. Kow, however, a contemporary ersonal

    Computerof even modest power can perform digital video editingwith editing

    software. >any consumer camcorders bundle a light0feature-limited1 version

    of such software, as do some computers, and more advanced software is

    widely available at a variety of price points.

    As of &%%D, analog camcorders are still available but not widely mar"eted

    anymore< those that are still available are often less than 2I&E%, but require

    special capture hardware for non-linear editing. :n terms of sales, mini(V

    camcorders 0and to a much lesser e*tent, (igital;1 dominate most first world

    mar"ets. Camcorders which record directly on (V( media are also on therise, primarily among users with no plans to edit their footage. Konetheless,

    software for editing video files created by (V( camcorders is available,

    including 5omble (V( and Video/edo.

    'ard dis" based camcorders are appearing as well< JVC and ony are the

    primary manufacturers of these units. :ncreased storage capacity over other

    types of media is the main advantage with these models< however, with this

    follows a slightly reduced image quality and loss of fle*ibility when compared

    to other formats such as >ini(V, ma"ing the ease of transferring the footageto a C for quic" editing the main attraction of 'ard dis" camcorders


    A charge-coupled device0CCD1 is an analog shift register, enabling analog

    signals 0electric charges1 to be transported through successive stages

    0capacitors1 controlled by a cloc"signal. Charge coupled devices can be used

    as a form of memory or for delaying analog, sampled signals. Today, they are

    most widely used for serialiing parallel analog signals, namely in arrays of

    photoelectric light sensors. Kot all image sensorsuse CC( technology< fore*ample, C>Fchips are also commercially available.

    7CC(7 refers to the way that the image signal is read out from the chip. 2nder

    the control of an e*ternal circuit, each capacitor can transfer its electric

    chargeto one or other of its neighbors. CC(s are used in digital photography

    and astronomy0particularly in photometry1, sensors, electron microscopy,
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    medical fluoroscopy, optical and 2Vspectroscopyand high speed techniques

    such as luc"y imaging.

    A specially developed CC( used for ultravioletimaging in a wire bonded pac"age.


    Gugene . Lally of the Jet ropulsion Laboratory wrote a paper published in

    #$8#, 7>osaic Huidance for :nterplanetary Travel7, illustrating a mosaic array

    of optical detectors that formed a photographic image using digital

    processing. (igital photography was conceived by this paper. Lally noted

    such an optical array required development so digital cameras could be

    produced. The required array consisting of CC( technology was invented in#$8$ by 5illard )oyleand Heorge G. mithat AT3T )ell Labs. The lab was

    wor"ing on the picture phone and on the development of semiconductor

    bubble memory. >erging these two initiatives, )oyle and mith conceived of

    the design of what they termed 9Charge 7)ubble7 (evices9. The essence of

    the design was the ability to transfer charge along the surface of a

    semiconductor. As the CC( started its life as a memory device, one could

    only 7in6ect7 charge into the device at an input register. 'owever, it was

    immediately clear that the CC( could receive charge via the photoelectric

    effectand electronic images could be created. )y #$8$, )ell researchers were

    able to capture images with simple linear devices< thus the CC( was born.

    everal companies, including airchild emiconductor, /CAand Te*as

    :nstruments, pic"ed up on the invention and began development programs.

    airchild was the first with commercial devices and by #$D? had a linear E%%

    element device and a &-( #%% * #%% pi*el device. 2nder the leadership of
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    !auo :wama, onyalso started a big development effort on CC(s involving

    a lot of money. Gventually, ony managed to mass produce CC(s for their

    camcorders. )efore this happened, :wama died in August #$;&.

    ubsequently, a CC( chip was placed on his tombstone to ac"nowledge his


    :n January &%%8, )oyle and mith were awarded the Kational Academy of

    Gngineering Charles tar" (raper rie for their wor" on the CC(@&.

    )asics of operation

    :n a CC( for capturing images, there is a photoactive region 0an epita*ial

    layer of silicon1, and a transmission region made out of a shift register 0the

    CC(, properly spea"ing1

    An image is pro6ected by a lenson the capacitor array 0the photoactive

    region1, causing each capacitor to accumulate an electric charge proportional

    to the lightintensity at that location. A one-dimensional array, used in line-

    scan cameras, captures a single slice of the image, while a two-dimensional

    array, used in video and still cameras, captures a two-dimensional picture

    corresponding to the scene pro6ected onto the focal plane of the sensor. Fnce

    the array has been e*posed to the image, a control circuit causes each

    capacitor to transfer its contents to its neighbor. The last capacitor in the array

    dumps its charge into a charge amplifier, which converts the charge into avoltage. )y repeating this process, the controlling circuit converts the entire

    semiconductor contents of the array to a sequence of voltages, which it

    samples, digities and stores in some form of memory. These stored images

    can then be transferred to a printer, digital storage device or video display.

    (etailed physics of operation

    The photoactive region of the CC( is, generally, an epita*iallayer of silicon. :t

    has a doping of pO 0)oron1 and is grown upon the substratematerial, often pO

    O. :n buried channel devices, the type of design utilied in most modern

    CC(s, certain areas of the surface of the silicon are ion implanted with

    phosphorus, giving them an n-doped designation. This region defines the

    channel in which the photogenerated charge pac"ets will travel. The gate

    o*ide, i.e. the capacitor dielectric, is grown on top of the epita*ial layer and

    substrate. Later on in the process polysilicon gates are deposited by chemical
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    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 utiliation of the LFCF process to produce

    the channel stop region. Channel stops are thermally grown o*ides that serve

    to isolate the charge pac"ets in one column from those in another. Thesechannel stops are produced before the polysilicongates are, as the LFCF

    process utilies a high temperature step that would destroy the gate material.

    The channels stops are parallel to, and e*clusive of, the channel, or 7charge

    carrying7, regions. Channel stops often have a pO doped region underlying

    them, providing a further barrier to the electrons in the charge pac"ets 0this

    discussion of the physics of CC( devices assumes an electron transfer

    device, though hole transfer is possible1.

    7Fne-dimensional7 CC( from a fa* machine.

    Fne should note that the cloc"ing of the gates, alternately high and low, will

    forward and reverse bias the diode that is provided by the buried channel 0n-

    doped1 and the epita*ial layer 0p-doped1. This will cause the CC( to deplete,

    near the p-n 6unctionand will collect and move the charge pac"ets beneath

    the gates P and within the channels P of the device.

    :t should be noted that CC( manufacturing and operation can be optimied

    for different uses. The above process describes a frame transfer CC(. 5hile

    CC(s may be manufactured on a heavily doped pOO 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, dar" current, and infrared

    and red response. This method of manufacture is used in the construction of

    interline transfer devices.


    The CC( image sensors can be implemented in several different

    architectures. The most common are full-frame, frame-transfer and interline.
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    The distinguishing characteristic of each of these architectures is their

    approach to the problem of shuttering.

    :n 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 will smear as the device is cloc"ed or read out.

    5ith a frame transfer CC(, half of the silicon area is covered by an opaque

    mas" 0typically aluminium1. The image can be quic"ly transferred from the

    image area to the opaque area or storage region with acceptable smear of a

    few percent. That image can then be read out slowly from the storage region

    while a new image is integrating or e*posing in the active area. rame-

    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 e*tends this concept one step further and mas"s

    every other column of the image sensor for storage. :n this device, only one

    pi*el 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 factorto appro*imately E%B and the

    effective quantum efficiencyby an equivalent amount. >odern designs haveaddressed this deleterious characteristic by adding microlenses on the

    surface of the device to direct light away from the opaque regions and on the

    active area. >icrolenses can bring the fill factor bac" up to $%B or more

    depending on pi*el sie and the overall system9s optical design.

    The choice of architecture comes down to one of utility. :f the application

    cannot tolerate an e*pensive, failure prone, power hungry mechanical shutter,

    then an interline device is the right choice. Consumer snap-shot cameras

    have used interline devices. Fn the other hand, for those applications thatrequire the best possible light collection and issues of money, power and time

    are less important, the full-frame device will be 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 was
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    addressed. Today, the choice of frame-transfer is usually made when an

    interline architecture is not available, such as in a bac"-illuminated device.

    CC(s containing grids of pi*elsare used in digital cameras, optical scanners

    and video cameras as light-sensing devices. They commonly respond to D%B

    of the incidentlight 0meaning a quantum efficiency of about D%B1 ma"ing

    them far more efficient than photographic film, which captures only about &B

    of the incident light.

    CC( from a &.# megapi*elArgusdigital camera.

    CC( from a &.# megapi*el'ewlett-ac"arddigital camera.

    >ost common types of CC(s are sensitive to infraredlight, which allows

    infrared photography, night-visiondevices, and ero lu*0or near ero lu*1

    video-recording4photography. )ecause of their sensitivity to infrared, CC(s

    used in astronomy are usually cooled to liquid nitrogentemperatures,

    because infrared blac" body radiationis emitted from room-temperature

    sources. Fne other consequence of their sensitivity to infrared is that infrared

    from remote controlswill often appear on CC(-based digital cameras or

    camcorders if they don9t have infrared bloc"ers. Cooling also reduces the

    array9s dar" current, improving the sensitivity of the CC( to low light

    intensities, even for ultraviolet and visible wavelengths.
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    Astronomical CC(s

    (ue to the high quantum efficiencies of CC(s, linearity of their outputs 0one

    count for one photon of light1, ease of use compared to photographic plates,

    and a variety of other reasons, CC(s were very rapidly adopted byastronomers for nearly all 2V-to-infrared applications.

    Thermal noise, dar" current, and cosmic raysmay alter the pi*els in the CC(

    array. To counter such effects, astronomers ta"e an average of several

    e*posures with the CC( shutter closed and opened. The average of images

    ta"en with the shutter closed is necessary to lower the random noise. Fnce

    developed, the Qdar" frameR average image is then subtractedfrom the open-

    shutter image to remove the dar" current and other systematic defects in the

    CC( 0dead pi*els, hot pi*els, etc.1. The 'ubble pace Telescope, inparticular, has a highly developed series of steps 0Qdata reduction pipelineR1

    used to convert the raw CC( data to useful images. ee@=for a more in-depth

    description of the steps in processing astronomical CC( data.

    CC( cameras used in astrophotographyoften require sturdy mounts to cope

    with vibrations and breees, along with the tremendous weight of most

    imaging platforms. To ta"e long e*posures of gala*ies and nebulae, many

    astronomers use a technique "nown as auto-guiding. >ost autoguiders use a

    second CC( chip to monitor deviations during imaging. This chip can rapidly

    detect errors in trac"ing and command the mount9s motors to correct for them.

    Array of =% CC(s used on loan (igital "y urveytelescope imaging camera, an

    e*ample of 7drift-scanning.7
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    An interesting unusual astronomical application of CC(s, called 7drift-

    scanning7, is to use a CC( to ma"e a fi*ed telescope behave li"e a trac"ing

    telescope and follow the motion of the s"y. The charges in the CC( are

    transferred and read in a direction parallel to the motion of the s"y, and at the

    same speed. :n this way, the telescope can image a larger region of the s"ythan its normal field of view. The loan (igital "y urveyis the most famous

    e*ample of this, using the technique to produce the largest uniform survey of

    the s"y yet.

    Color cameras

    A)ayer filteron a CC(

    An /H)G filteron a CC(

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    Canon owerhot AD&% :has an #4&,E inch CC(-Colorsenor inside

    (igital color cameras generally use a )ayer mas"over the CC(. Gach square

    of four pi*els has one filtered red, one blue, and two green 0the human eyeis

    more sensitive to green than either red or blue1. The result of this is that

    luminanceinformation is collected at every pi*el, but the color resolution is

    lower than the luminance resolution.

    )etter color separation can be reached by three-CC( devices 0=CC(1 and a

    dichroic beam splitter prism, that splits the imageinto red, greenand blue

    components. Gach of the three CC(s is arranged to respond to a particular

    color. ome semi-professional digital video camcorders 0and most

    professionals1 use this technique. Another advantage of =CC( over a )ayer

    mas" device is higher quantum efficiency0and therefore higher light sensitivity

    for a given aperture sie1. This is because in a =CC( device most of the light

    entering the aperture is captured by a sensor, while a )ayer mas" absorbs a

    high proportion 0about &4=1 of the light falling on each CC( pi*el.

    ince a very-high-resolution CC( chip is very e*pensive as of &%%E, a =CC(

    high-resolution still camera would be beyond the price range even of many

    professional photographers. There are some high-end still cameras that use a

    rotating color filter to achieve both color-fidelity and high-resolution. These

    multi-shot cameras are rare and can only photograph ob6ects that are not


    Sensor sizes

    ensors 0CC( 4 C>F1 are often referred to with an imperial fraction

    designation such as #4#.;7 or &4=7, this measurement actually originates bac"

    in the #$E%9s and the time of Vidicon tubes. Compact digital cameras and

    (igicams typically have much smaller sensors than a (igital L/ and are

    thus less sensitive to light and inherently more prone to noise. ome
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    e*amples of the CC(s found in modern cameras can be found in this tablein

    a (igital hotography /eview article

    Type Aspect Ratioidthmm





    #487 ?= &.=%% #.D=% &.;D; =.$D$ #.%%%

    #4?7 ?= =.&%% &.?%% ?.%%% D.8;% #.$=%

    #4=.87 ?= ?.%%% =.%%% E.%%% #&.%%% =.%#8

    #4=.&7 ?= ?.E=8 =.?#8 E.8D; #E.?$E =.;$?

    #4=7 ?= ?.;%% =.8%% 8.%%% #D.&;% ?.=?=

    #4&.D7 ?= E.&D% =.$8% 8.E$& &%.;8$ E.&?E

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    #ther image sizes as a comparison

    A-C =& &E.#%% #8.D%% =%.#?; ?#$.#D% #%E.=?8

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    Three-CCDor $CCDis a term used to describe an imaging systememployed

    by some still cameras, videocameras, telecineand camcorders. Three-CC(

    cameras have three separate charge-coupled devices0CC(s1, each one

    ta"ing a separate measurement of red, green, and blue light. Light coming

    into the lens is split by a trichroic prism assembly, which directs the

    appropriate wavelength ranges of light to their respective CC(s. Three-CC(

    cameras are generally regarded to provide superior image quality to cameras

    with only one CC(. )y ta"ing a separate reading of red, green, and blue

    values for each pi*el, three-CC( cameras achieve much better precision than

    single-CC( cameras. Almost all single-CC( cameras use a bayer filter, which

    allows them to detect only one-third of the color information for each pi*el.
  • 8/10/2019 Camcorder - CTS references


    The other two-thirds must be interpolatedwith a demosaicingalgorithm to 9fill

    in the gaps9.

    The combination of the three sensors can be done in the following ways

    Composite sampling, where the three sensors are perfectly aligned to avoid

    any color artifact when recombining the information from the three color


    i*el shifting, where the three sensors are shifted by a fraction of a pi*el. After

    recombining the information from the three sensors, higher spatial resolution

    can be achieve[email protected] neededi*el shifting can be horiontal only to provide

    higher horiontal resolution in standard resolution camera, or horiontal and

    vertical to provide high resolution image using standard resolution imager for

    e*ample. The alignment of the three sensors can be achieved by micro

    mechanical movements of the sensors relative to each other.

    Arbitrary alignment, where the random alignment errors due to the optics are

    comparable to or larger than the pi*el sie.

    Three-CC( cameras are generally more e*pensive than single-CC( cameras

    because they require three times as many elements to form the image

    detector, and because they require a precision color-separation beam-splitter

    optical assembly.

    The concept of cameras using three image pic"ups, one for each primary

    color, was first developed for color photography on three glass plates in the

    late nineteenth century, and in the #$8%s through #$;%s was the dominant

    method to record color images in television, as other possibilities to record

    more than one color on the video camera tubewere difficult.

    Three-CC( cameras are often referred to as 7three-chip7 cameras< this term

    is actually more descriptive and inclusive, since it includes cameras that use

    C>Factive pi*el sensorsinstead of CC(s.
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    A color-separation beam splitter prism assembly, with a white beam entering the

    front, and red, green, and blue beams e*iting the three focal-plane faces.

    A hilips type trichroic beam splitter prism schematic, with a different color

    separation order than the assembly shown in the photo. The red beam undergoes

    total internal reflectionat the air gap, while the other reflections are dichroic.


    (ielectric mirrors can be produced as low-pass, high-pass, band-pass, or

    band-stop filters. :n the e*ample shown, a red and a blue mirror reflect the

    respective bands bac", somewhat off a*is. The angles are "ept as small as

    practical to minimie polariation-dependent color effects. To reduce

    unwanted reflections, air-glass interfaces are minimied< the image sensors

    may be attached to the e*it faces with an inde*-matched optical epo*y,
  • 8/10/2019 Camcorder - CTS references


    sometimes with an intervening color trim filter. The hilips type prism includes

    an air gap with total internal reflection in one light path, while the other prism

    shown above does not. A typical )ayer filtersingle-chip image sensor absorbs

    at least two-thirds of the visible light with its filters, while in a three-CC(

    sensor the filters absorb only stray light and invisible light, and possibly a littlemore for color tuning, so that the three-chip sensor has better low light