Charge-coupled device

A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins.

In recent years CCD has become a major technology for digital imaging. In a CCD image sensor, pixels are represented by p-doped metal-oxide-semiconductors (MOS) capacitors. These capacitors 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; 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 complementary metal-oxide-semiconductors (CMOS) are generally used; the large quality advantage CCDs enjoyed early on has narrowed over time.

Delta-Doped Charged Coupled Devices (CCD) for Ultra-Violet and Visible Detection
A specially developed CCD in a wire-bonded package used for ultraviolet imaging


Nobel Prize 2009-Press Conference KVA-19
George E. Smith and Willard Boyle, 2009

The charge-coupled device was invented in 1969 in the United States at AT&T Bell Labs by Willard Boyle and George E. Smith.[1] The lab was working on semiconductor bubble memory when Boyle and Smith conceived of the design of what they termed, in their notebook, "Charge 'Bubble' Devices".[2] The device could be used as 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 patent (U.S. Patent 4,085,456) on the application of CCDs to imaging was assigned to Michael Tompsett.[3]

The initial paper describing the concept[4] listed possible uses as a memory, a delay line, and an imaging device. The first experimental device[5] demonstrating the principle was a row of closely spaced metal squares on an oxidized silicon surface electrically accessed by wire bonds.

The first working CCD made with integrated circuit technology was a simple 8-bit shift register.[6] 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.[7] Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on 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 2-D 100 x 100 pixel device. Steven Sasson, an electrical engineer working for Kodak, invented the first digital still camera using a Fairchild 100 x 100 CCD in 1975.[8] The first KH-11 KENNEN reconnaissance satellite equipped with charge-coupled device array (800 x 800 pixels)[9] technology for imaging was launched in December 1976.[10] Under the leadership of Kazuo Iwama, Sony also 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.[11]

In January 2006, Boyle and Smith were awarded the National Academy of Engineering Charles Stark Draper Prize,[12] and in 2009 they were awarded the Nobel Prize for Physics,[13] for their invention of 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 charge coupled device (CCD) imagers. He was also awarded the 2012 IEEE Edison Medal "For pioneering contributions to imaging devices including CCD Imagers, cameras and thermal imagers".

Basics of operation

CCD charge transfer animation
The charge packets (electrons, blue) are collected in potential wells (yellow) created by applying positive voltage at the gate electrodes (G). Applying positive voltage to the gate electrode in the correct sequence transfers the charge packets.

In a CCD for capturing images, there 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 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 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 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.[14]

CCD line sensor
"One-dimensional" CCD image sensor from a fax machine

Detailed physics of operation

Charge generation

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 the threshold for strong inversion, which will eventually result in the creation of a 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.[15] 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 a non-equilibrium state called deep depletion.[16] 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:

  • photo-generation (up to 95% of quantum efficiency),
  • generation in the depletion region,
  • generation at the surface, and
  • generation in the neutral bulk.

The last three processes are known as dark-current generation, and add noise to the image; they can limit 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,[17] typically about 105 electrons per pixel.[16]

Design and manufacturing

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 the channel in which the photogenerated charge packets will travel. Simon Sze details the advantages of a buried-channel device:[16]

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 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 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 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 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 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 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 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 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 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 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.

CCD from a 2.1 megapixel Argus digital camera
CCD SONY ICX493AQA sensor side
CCD Sony ICX493AQA 10.14 (Gross 10.75) Mpixels APS-C 1.8" (23.98 x 16.41mm) sensor side
CCD SONY ICX493AQA pins side
CCD Sony ICX493AQA 10.14 (Gross 10.75) Mpixels APS-C 1.8" (23.98 x 16.41mm) pins side

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 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 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 the incident light.

2.1 MP CCD Close Up
CCD from a 2.1 megapixel Hewlett-Packard digital camera

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 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.

Frame transfer CCD

A frame transfer CCD sensor

The frame transfer CCD imager was the first imaging structure proposed for CCD Imaging by Michael Tompsett at Bell Laboratories. A frame transfer CCD 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 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, the CCD cannot be used to collect light while it is being read out. Unfortunately, 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 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 a CCD is the higher cost: the cell area is basically doubled, and more complex control electronics are needed.

Intensified charge-coupled device

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 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 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 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 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. This cooling system adds additional costs to the EMCCD camera and often yields heavy condensation problems in the application.

ICCDs are used in night vision devices and in various scientific applications.

Electron-multiplying CCD

EMCCD2 color en
Electrons are transferred serially through the gain stages making up the multiplication register of an EMCCD. The high voltages used in these serial transfers induce the creation of additional charge carriers through impact ionisation.
Output vs input electrons
in an EMCCD there is a dispersion (variation) in the number of electrons output by the multiplication register for a given (fixed) number of input electrons (shown in the legend on the right). The probability distribution for the number of output electrons is plotted logarithmically on the vertical axis for a simulation of a multiplication register. Also shown are results from the empirical fit equation shown on this page.

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 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 (), with single input electrons giving many thousands of output electrons. Reading 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. It is to be noted that 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 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. 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 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:


where P is the probability of getting n output electrons given m input electrons and a total mean multiplication register gain of g.

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 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 unfortunately 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 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 a wide variety of modern fluorescence microscopy techniques thanks to greater SNR in low-light conditions in comparison with traditional CCDs and ICCDs.

In terms of noise, commercial EMCCD cameras typically have clock-induced charge (CIC) and dark current (dependent on the extent of cooling) that together lead to an effective readout noise ranging from 0.01 to 1 electrons per pixel read. However, recent improvements in EMCCD technology have led to a new generation of cameras capable of producing significantly less CIC, higher charge transfer efficiency and an EM gain 5 times higher than what was previously available. These advances in low-light detection lead to an effective total background noise of 0.001 electrons per pixel read, a noise floor unmatched by any other low-light imaging device.[18]

Use in astronomy

Due to the high quantum efficiencies of CCDs (for a quantum efficiency of 100%, one count equals one photon), linearity of their outputs, ease of use compared to photographic plates, and a variety of other reasons, CCDs were very rapidly adopted by astronomers for nearly all UV-to-infrared applications.

Thermal noise and cosmic rays may alter the pixels in the CCD array. To counter such effects, astronomers take several exposures with the CCD shutter closed and opened. The average of images taken with the shutter closed is necessary to lower the random noise. Once developed, the dark frame average image is then subtracted from the open-shutter image to remove the dark current and other systematic defects (dead pixels, hot pixels, etc.) in the CCD.

The Hubble Space Telescope, in particular, has a highly developed series of steps (“data reduction pipeline”) to convert the raw CCD data to useful images.[19]

CCD cameras used in astrophotography often require sturdy mounts to cope with vibrations from wind and other sources, along with the tremendous weight of most imaging platforms. To take long exposures of galaxies and nebulae, many astronomers use a technique known as auto-guiding. Most autoguiders use a second CCD chip to monitor deviations during imaging. This chip can rapidly detect errors in tracking and command the mount motors to correct for them.

Array of 30 CCDs used on the Sloan Digital Sky Survey telescope imaging camera, an example of "drift-scanning".

An unusual astronomical application of CCDs, called drift-scanning, uses a CCD to make a fixed telescope behave like a tracking telescope and follow the motion of the sky. The charges in the CCD are transferred and read in a direction parallel to the motion of the sky, and at the same speed. In this way, the telescope can image a larger region of the sky than its normal field of view. The Sloan Digital Sky Survey is the most famous example of this, using the technique to a survey of over a quarter of the sky.

In addition to imagers, CCDs are also used in an array of analytical instrumentation including spectrometers[20] and interferometers.[21]

Color cameras

Bayer pattern on sensor
A Bayer filter on a CCD
SONY ICX024AK 10A 1988 494kpix CCD
Sony 2/3" CCD ICX024AK 10A 494496 (816*606) pixels CCD removed from Sony CCD-V88E video camera from 1988, with Yellow, Green and Cyan vertical stripe filter
Webcam CCD - 640x480px Colour
CCD color sensor
An RGGB Bayer Colour Filter on a 1980's vintage Sony PAL Camcorder CCD
x80 microscope view of an RGGB Bayer filter on a 240 line Sony CCD PAL Camcorder CCD sensor

Digital color cameras generally use a Bayer mask over the CCD. Each square of four pixels has one filtered red, one blue, and two green (the human eye is more sensitive to green than either red or blue). The result of this is that luminance information is collected at every pixel, but the color resolution is lower than the luminance resolution.

Better color separation can be reached by three-CCD devices (3CCD) and a dichroic beam splitter prism, that splits the image into red, green and blue components. Each of the three CCDs is arranged to respond to a particular color. Many professional video camcorders, and some semi-professional camcorders, use this technique, although developments in competing CMOS technology have made CMOS sensors, both with beam-splitters and bayer filters, increasingly popular in high-end video and digital cinema cameras. Another advantage of 3CCD over a Bayer mask device is higher quantum efficiency (and therefore higher light sensitivity for a given aperture size). This is because in a 3CCD device most of the light entering the aperture is captured by a sensor, while a Bayer mask absorbs a high proportion (about 2/3) of the light falling on each CCD pixel.

For still scenes, for instance in microscopy, the resolution of a Bayer mask device can be enhanced by microscanning technology. During the process of color co-site sampling, several frames of the scene are produced. Between acquisitions, the sensor is moved in pixel dimensions, so that each point in the visual field is acquired consecutively by elements of the mask that are sensitive to the red, green and blue components of its color. Eventually every pixel in the image has been scanned at least once in each color and the resolution of the three channels become equivalent (the resolutions of red and blue channels are quadrupled while the green channel is doubled).

Sensor sizes

Sensors (CCD / CMOS) come in various sizes, or image sensor formats. These sizes are often referred to with an inch fraction designation such as 1/1.8″ or 2/3″ called the optical format. This measurement actually originates back in the 1950s and the time of Vidicon tubes.


Vertical smear
Vertical smear

When a CCD exposure is long enough, eventually the electrons that collect in the "bins" in the brightest part of the image will overflow the bin, resulting in blooming. The structure of the CCD allows the electrons to flow more easily in one direction than another, resulting in vertical streaking.[22][23][24]

Some anti-blooming features that can be built into a CCD reduce its sensitivity to light by using some of the pixel area for a drain structure.[25] James M. Early developed a vertical anti-blooming drain that would not detract from the light collection area, and so did not reduce light sensitivity.

See also


  1. ^ See U.S. Patent 3,792,322 and U.S. Patent 3,796,927
  2. ^ James R. Janesick (2001). Scientific charge-coupled devices. SPIE Press. p. 4. ISBN 978-0-8194-3698-6.
  3. ^ U.S. Patent 4,085,456
  4. ^ W. S. Boyle; G. E. Smith (April 1970). "Charge Coupled Semiconductor Devices". Bell Syst. Tech. J. 49 (4): 587–593.
  5. ^ G. F. Amelio; M. F. Tompsett; G. E. Smith (April 1970). "Experimental Verification of the Charge Coupled Device Concept". Bell Syst. Tech. J. 49 (4): 593–600. doi:10.1002/j.1538-7305.1970.tb01791.x.
  6. ^ M. F. Tompsett; G. F. Amelio; G. E. Smith (1 August 1970). "Charge Coupled 8-bit Shift Register". Applied Physics Letters. 17: 111–115. Bibcode:1970ApPhL..17..111T. doi:10.1063/1.1653327.
  7. ^ Tompsett, M.F.; Amelio, G.F.; Bertram, W.J., Jr.; Buckley, R.R.; McNamara, W.J.; Mikkelsen, J.C., Jr.; Sealer, D.A. (November 1971). "Charge-coupled imaging devices: Experimental results". IEEE Transactions on Electron Devices. 18 (11): 992–996. Bibcode:1971ITED...18..992T. doi:10.1109/T-ED.1971.17321. ISSN 0018-9383.CS1 maint: Multiple names: authors list (link)
  8. ^ Dobbin, Ben. (2005-09-08) Kodak engineer had revolutionary idea: the first digital camera. Retrieved on 2011-11-15.
  9. ^ - KH-11 KENNAN, 2007-04-24
  10. ^ "NRO review and redaction guide (2006 ed.)" (PDF). National Reconnaissance Office.
  11. ^ Johnstone, B. (1999). We Were Burning: Japanese Entrepreneurs and the Forging of the Electronic Age. New York: Basic Books. ISBN 0-465-09117-2.
  12. ^ "Charles Stark Draper Award". Archived from the original on 2007-12-28.
  13. ^ "Nobel Prize website".
  14. ^ Gilbert F. Amelio (February 1974). "Charge-Coupled Devices". Scientific American. 230 (2).
  15. ^ For instance, the specsheet of PI/Acton's SPEC-10 camera specifies a dark current of 0.3 electron per pixel per hour at -110 °C.
  16. ^ a b c Sze, S. M.; Ng, Kwok K. (2007). Physics of semiconductor devices (3 ed.). John Wiley and Sons. ISBN 978-0-471-14323-9. Chapter 13.6.
  17. ^ Apogee CCD University - Pixel Binning
  18. ^ Daigle, Olivier; Djazovski, Oleg; Laurin, Denis; Doyon, René; Artigau, Étienne (July 2012). "Characterization results of EMCCDs for extreme low light imaging" (PDF).
  19. ^ Hainaut, Oliver R. (December 2006). "Basic CCD image processing". Retrieved January 15, 2011.
    Hainaut, Oliver R. (June 1, 2005). "Signal, Noise and Detection". Retrieved October 7, 2009.
    Hainaut, Oliver R. (May 20, 2009). "Retouching of astronomical data for the production of outreach images". Retrieved October 7, 2009.
    (Hainaut is an astronomer at the European Southern Observatory)
  20. ^ V. Deckert and W. Kiefer, Scanning multichannel technique for improved spectrochemical measurements with a CCD camera and its application to Raman spectroscopy, Appl. Spectros. 46, 322-328 (1992)
  21. ^ F. J. Duarte, On a generalized interference equation and interferometric measurements, Opt. Commun. 103, 8-14 (1993).
  22. ^ Phil Plait. "The Planet X Saga: SOHO Images"
  23. ^ Phil Plait. "Why, King Triton, how nice to see you!"
  24. ^ Thomas J. Fellers and Michael W. Davidson. "CCD Saturation and Blooming" Archived July 27, 2012, at the Wayback Machine
  25. ^ Albert J. P. Theuwissen (1995). Solid-State Imaging With Charge-Coupled Devices. Springer. pp. 177–180. ISBN 9780792334569.

External links

Andor Technology

Andor Technology Ltd is a developer and manufacturer of high performance light measuring solutions (scientific digital cameras). It became a subsidiary of Oxford Instruments after it was purchased for £176m in December 2013.Andor Technology was set up by its founders, Dr. Hugh Cormican, Dr. Donal Denvir and Mr. Mike Pringle in the mid-1980s. While studying at Queen's University Belfast, they "used their physics know-how to build a highly sensitive digital a tool for their laser research." They subsequently set up Andor Technology to develop it into a commercial product for use in scientific research.

Andor Technology Ltd was established in 1989, as a spin out from Queen's University, Belfast. In December 2004 the company became a PLC when it listed on the Alternative Investment Market of the London Stock Exchange.The company is based in Belfast, Northern Ireland. It designs, manufactures and sells scientific imaging equipment including charge-coupled device (CCD), electron-multiplying CCD (EMCCD), scientific CMOS (sCMOS - an improved Active pixel sensor) and Intensified charge-coupled device camera systems, spectroscopy instrumentation, and microscopy systems. The cameras can be used for low light imaging, astronomy, spectroscopy, X-ray, time resolved, and confocal microscopy studies and have a wide range of users including physicists, biologists, life scientists, geneticists and nano-technologists all around the world.

Andor introduced its first EMCCD camera, the DV 465 in 2001 and the company was awarded The Photonics Circle of Excellence Awards from Laurin Publishing, which recognizes the 25 Most Technically Innovative New Products of the Year.EMCCD cameras are based on CCD chips that incorporate electron multiplication, or EMCCD technology. It is used in fields such as drug discovery, where scientists need to watch vats of chemicals in real-time, astrophysics and oceanography.

Bell Labs

Nokia Bell Labs (formerly named AT&T Bell Laboratories and Bell Telephone Laboratories) is an industrial research and scientific development company owned by Finnish company Nokia. Its headquarters are located in Murray Hill, New Jersey. Other laboratories are located around the world (with some in the United States). Bell Labs has its origins in the complex past of the Bell System.

In the late 19th century, the laboratory began as the Western Electric Engineering Department and was located at 463 West Street in New York City. In 1925, after years of conducting research and development under Western Electric, the Engineering Department was reformed into Bell Telephone Laboratories and under the shared ownership of American Telephone & Telegraph Company and Western Electric.

Researchers working at Bell Labs are credited with the development of radio astronomy, the transistor, the laser, the charge-coupled device (CCD), information theory, the Unix operating system, and the programming languages C, C++, and S. Nine Nobel Prizes have been awarded for work completed at Bell Laboratories.

Contax i4R

The Contax i4R is a digital camera manufactured by Kyocera. The i4R was announced on 28 September 2004. Its design was one of the more unusual of Contax's designs. Kyocera released it to the public in November, 2004 with a price of 299 GBP. The i4R features a Carl Zeiss Tessar T* 6.5mm f/2.8 lens. Its image pickup device is a charge-coupled device with 4.19 × 106 gross pixels. The i4R is PictBridge-compliant. Besides its usually small size for the time, its other unusual feature was its ability to focus down to about two inches (five centimetres).

Kyocera announced its plans to discontinue the Contax brand in April 2005, and exited all camera activity in September 2005.

Dark current (physics)

In physics and in electronic engineering, dark current is the relatively small electric current that flows through photosensitive devices such as a photomultiplier tube, photodiode, or charge-coupled device even when no photons are entering the device; it consists of the charges generated in the detector when no outside radiation is entering the detector. It is referred to as reverse bias leakage current in non-optical devices and is present in all diodes. Physically, dark current is due to the random generation of electrons and holes within the depletion region of the device.

The charge generation rate is related to specific crystallographic defects within the depletion region. Dark-current spectroscopy can be used to determine the defects present by monitoring the peaks in the dark current histogram's evolution with temperature.

Dark current is one of the main sources for noise in image sensors such as charge-coupled devices. The pattern of different dark currents can result in a fixed-pattern noise; dark frame subtraction can remove an estimate of the mean fixed pattern, but there still remains a temporal noise, because the dark current itself has a shot noise.

Electro-Optical Targeting System

An Electro-Optical Targeting System (EOTS), is a system employed to track and locate targets in aerial warfare. It can use charge-coupled device TV cameras, laser rangefinders and laser designators.

George E. Smith

George Elwood Smith (born May 10, 1930) is an American scientist, applied physicist, and co-inventor of the charge-coupled device (CCD). He was awarded a one-quarter share in the 2009 Nobel Prize in Physics for "the invention of an imaging semiconductor circuit—the CCD sensor, which has become an electronic eye in almost all areas of photography". In 2017, Smith was announced as one of four winners of the Queen Elizabeth Prize for Engineering, for his contribution to the creation of digital imaging sensors.

Hole accumulation diode

A Hole accumulation diode (HAD) is an electronic noise reduction device in a charge-coupled device (CCD) or CMOS imaging sensor. HAD devices function by reducing dark current that occur in the absence of light falling on the imager for noise reduction and enhanced image quality.

HAD CCDs are used in consumer and professional single, as well as, three-chip video cameras.

James M. Early

James M. Early (July 25, 1922 – January 12, 2004) was an American engineer, best known for his work on transistors and charge-coupled device imagers. He is also known as Jim Early.


Each Pancam is one of two electronic stereo cameras on Mars Exploration Rovers Spirit and Opportunity. It has a filter wheel assembly that enables it to view different wavelengths of light and the pair of Pancams are mounted beside two NavCams on the MER camera bar assembly.According to Cornell University it can work with Mini-TES to analyze surroundings.According to a paper about Mars by JPL, the Pancam system can achieve an angular resolution of 300 microradians, which is three times better than the human eye. It can observe 14 spectral bands, and with two side-by side camera's can generate stereoscopic views of Mars, supporting the creation of large Mars panoroama's in excess of 10 Gbit uncompressed. Spirit rover took the highest resolution image ever taken on the surface of another planet up to that time when it landed in 2004.

Pises Observatory

Pises Observatory is an astronomical observatory at the Parc National des Cévennes in France. It is situated at 1300 m altitude and houses an optical telescope with a charge-coupled device used for asteroid surveys.


A polychromator is an optical device that is used to disperse light into different directions to isolate parts of the spectrum of the light. A prism or diffraction grating can be used to disperse the light. Unlike a monochromator, it outputs multiple beams over a range of wavelengths simultaneously. Monochromators have one exit slit and one wavelength at a time can pass through that slit. Polychromators have multiple exit slits, each of which allows a different wavelength to pass through it. A detector is placed after each slit so that the light at each wavelength is measured by a different detector. Polychromators are often used in spectroscopy.

Spectrograph is a closely related term. Spectrographs generally do not make use of exit slits. Instead, they use a single spatially selective detector (such as photographic film or a charge-coupled device). Spectrographs are generally used to observe a continuous range of wavelengths, while polychromators are more commonly used to observe several discrete wavelengths, leaving gaps in-between.

Quantum efficiency

The term quantum efficiency (QE) may apply to incident photon to converted electron (IPCE) ratio, of a photosensitive device or it may refer to the TMR effect of a Magnetic Tunnel Junction.

This article deals with the term as a measurement of a device's electrical sensitivity to light. In a charge-coupled device (CCD) it is the percentage of photons hitting the device's photoreactive surface that produce charge carriers. It is measured in electrons per photon or amps per watt. Since the energy of a photon is inversely proportional to its wavelength, QE is often measured over a range of different wavelengths to characterize a device's efficiency at each photon energy level. The QE for photons with energy below the band gap is zero. Photographic film typically has a QE of much less than 10%, while CCDs can have a QE of well over 90% at some wavelengths.

Scintillation counter

A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.

It consists of a scintillator which generates photons in response to incident radiation, a sensitive photodetector (usually a photomultiplier tube (PMT), a charge-coupled device (CCD) camera, or a photodiode), which converts the light to an electrical signal and electronics to process this signal.

Scintillation counters are widely used in radiation protection, assay of radioactive materials and physics research because they can be made inexpensively yet with good quantum efficiency, and can measure both the intensity and the energy of incident radiation.

Solid-state electronics

Solid-state electronics means semiconductor electronics; electronic equipment using semiconductor devices such as semiconductor diodes, transistors, and integrated circuits (ICs). The term is also used for devices in which semiconductor electronics which have no moving parts replace devices with moving parts, such as the solid-state relay in which transistor switches are used in place of a moving-arm electromechanical relay, or the solid state disk (SSD) a type of semiconductor memory used in computers to replace hard disk drives, which store data on a rotating disk.The term "solid state" became popular in the beginning of the semiconductor era in the 1960s to distinguish this new technology based on the transistor, in which the electronic action of devices occurred in a solid state, from previous electronic equipment that used vacuum tubes, in which the electronic action occurred in a gaseous state. A semiconductor device works by controlling an electric current consisting of electrons or holes moving within a solid crystalline piece of semiconducting material such as silicon, while the thermionic vacuum tubes it replaced worked by controlling current conducted by a gas of particles, electrons or ions, moving in a vacuum within a sealed tube. Although the first solid state electronic device was the cat's whisker detector, a crude semiconductor diode invented around 1904, solid state electronics really started with the invention of the transistor in 1947. Before that, all electronic equipment used vacuum tubes, because vacuum tubes were the only electronic components that could amplify, an essential capability in all electronics. The replacement of bulky, fragile, energy-wasting vacuum tubes by transistors in the 1960s and 1970s created a revolution not just in technology but in people's habits, making possible the first truly portable consumer electronics such as the transistor radio, cassette tape player, walkie-talkie and quartz watch, as well as the first practical computers and mobile phones.

Today, almost all electronics are solid-state except in some applications such as radio transmitters, in which vacuum tubes are still used, and some power industrial control circuits which use electromechanical devices such as relays. Additional examples of solid state electronic devices are the microprocessor chip, LED lamp, solar cell, charge coupled device (CCD) image sensor used in cameras, and semiconductor laser.

Staring array

A staring array, staring-plane array, focal-plane array (FPA), or focal-plane is an image sensing device consisting of an array (typically rectangular) of light-sensing pixels at the focal plane of a lens. FPAs are used most commonly for imaging purposes (e.g. taking pictures or video imagery), but can also be used for non-imaging purposes such as spectrometry, lidar, and wave-front sensing.

In radio astronomy, the focal-plane array (FPA) is an array at the focus of a radio telescope. At optical and infrared wavelengths it can refer to a variety of imaging device types, but in common usage it refers to two-dimensional devices that are sensitive in the infrared spectrum. Devices sensitive in other spectra are usually referred to by other terms, such as CCD (charge-coupled device) and CMOS image sensor in the visible spectrum. FPAs operate by detecting photons at particular wavelengths and then generating an electrical charge, voltage, or resistance in relation to the number of photons detected at each pixel. This charge, voltage, or resistance is then measured, digitized, and used to construct an image of the object, scene, or phenomenon that emitted the photons.

Applications for infrared FPAs include missile or related weapons guidance sensors, infrared astronomy, manufacturing inspection, thermal imaging for firefighting, medical imaging, and infrared phenomenology (such as observing combustion, weapon impact, rocket motor ignition and other events that are interesting in the infrared spectrum).

Superconducting camera

The superconducting camera, SCAM, is an ultra-fast photon-counting camera developed by the European Space Agency. It is cooled to just 0.3 K (three-tenths of a degree above absolute zero). This enables its sensitive electronic detectors, known as superconducting tunnel junction detectors, to register almost every photon of light that falls into it.

Its advantage over a CCD (charge-coupled device) is that it can measure both the brightness (rate) of the incoming photon stream and the colour (wavelength or energy) of each individual photon.

The number of free primary electrons generated per photon event is proportional to the photon energy and amounts to ~18,000 per electronvolt, and therefore if the device is operated in single-photon count mode the energy of each captured photon can be calculated in the visible-light range, where photons have energies of a few electronvolts, each generating >20,000 electrons. In a normal CCD, only one primary electron is generated per photon, except for very energetic photons, like X-rays, where a normal CCD can operate in a similar way to a SCAM.

Time delay and integration

A time delay and integration or time delay integration (TDI) charge-coupled device (CCD) is an image sensor for capturing images of moving objects at low light levels. The motion it can capture is similar to that captured by a line-scan CCD which uses a single line of photo-sensitive elements to capture one image strip of a scene that is moving at a right angle to the line of elements. A line-scan CCD needs to have high light levels, however, in order to register the light quickly before the motion causes smearing of the image. The TDI CCD overcomes this illumination limitation by having multiple rows of elements which each shift their partial measurements to the adjacent row synchronously with the motion of the image across the array of elements. This provides high sensitivity for moving images unobtainable using conventional CCD arrays or single-line-scan devices.The TDI CCD improves upon the single-line-scan system by adding the photocharges of its multiple lines.

Willard Boyle

Willard Sterling Boyle, (August 19, 1924 – May 7, 2011) was a Canadian physicist. He was a pioneer in the field of laser technology and co-inventor of the charge-coupled device. As director of Space Science and Exploratory Studies at Bellcomm he helped select lunar landing sited and provided support for the Apollo space program.On October 6, 2009, it was announced that he would share the 2009 Nobel Prize in Physics for "the invention of an imaging semiconductor circuit—the CCD sensor, which has become an electronic eye in almost all areas of photography".He was appointed a Companion of the Order of Canada — the award's highest level — on June 30, 2010.

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