 A specially developed CCD used for ultraviolet imaging in a wire bonded package. A charge-coupled device (CCD) is an image sensor, consisting of an integrated circuit containing an array of linked, or coupled, light-sensitive capacitors. Image File history File links Download high resolution version (3060x2036, 1323 KB)Original caption: Delta-Doped Charged Coupled Devices Delta-Doped Charged Coupled Devices (CCD) for Ultra-Violet and Visible Detection CCDs allow scientists to study one of the least explored windows of the electromagnetic spectrum - the extreme ultraviolet. ...
Image File history File links Download high resolution version (3060x2036, 1323 KB)Original caption: Delta-Doped Charged Coupled Devices Delta-Doped Charged Coupled Devices (CCD) for Ultra-Violet and Visible Detection CCDs allow scientists to study one of the least explored windows of the electromagnetic spectrum - the extreme ultraviolet. ...
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. ...
Hello--80. ...
Integrated circuit showing memory blocks, logic and input/output pads around the periphery A monolithic integrated circuit (also known as IC, microchip, silicon chip, computer chip or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) which has been manufactured in the surface...
Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ...
The capacitor perspective is reflective of the history of the development of the CCD and also is indicative of its general mode of operation, with respect to readout, but attempts aimed at optimization of present CCD designs and structures tend towards consideration of the photodiode as the fundamental collecting unit of the CCD. Under the control of an external circuit, each capacitor can transfer its electric charge to one or other of its neighbours. CCDs are used in digital photography and astronomy (particularly in photometry, optical and UV spectroscopy and high speed techniques such as lucky imaging). Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ...
It has been suggested that Digital photography/Temp be merged into this article or section. ...
A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ...
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical objects electromagnetic radiation. ...
Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ...
Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. ...
Lucky image of M15 core Lucky imaging is an astronomical photographic technique using a high-speed camera with exposure times short enough (100ms or less) so that the changes in the atmosphere during the exposure are minimal. ...
History
The CCD was invented in 1969 by Willard Boyle and George Smith at AT&T Bell Labs. The lab was working on the Picture-phone and on the development of semiconductor bubble memory. Merging these two initiatives, Boyle and Smith conceived of the design of what they termed 'Charge "Bubble" Devices'. The essence of the design was the ability to transfer charge along the surface of a semiconductor. As the CCD started its life as a memory device, one could only "inject" charge into the device at an input register. However, it was immediately clear that the CCD could receive charge via the photoelectric effect and electronic images could be created. By 1970 Bell researchers were able to capture images with simple linear devices; thus the CCD was born. Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on the invention and began development programs. Fairchild was the first with commercial devices and by 1974 had a linear 500 element device and a 2-D 100 x 100 pixel device. Willard S Boyle (August 19, 1924 - ) is a Canadian physicist and co-inventor of the Charge-coupled device. ...
The name George Smith refers to a number of people: George Smith, former valet and footman to Charles, Prince of Wales George Smith, Victorian Assyriologist George Smith, founder of the Glenlivet Distillery in Ballindalloch, Scotland George Smith southeast London architect George Smith, Republican representative for Pennsylvania (1809-1812) George Smith...
Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ...
A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ...
The photoelectric effect is the emission of electrons from matter upon the absorption of electromagnetic radiation, such as ultraviolet radiation or x-rays. ...
In January 2006, Boyle and Smith received the Charles Stark Draper Prize which is presented by the National Academy of Engineering for their work on the CCD. The Charles Stark Draper Prize is awarded by the National Academy of Engineering for the advancement of engineering and the education of the public about engineering. ...
Physics of Operation The photoactive region of the CCD is, generally, an epitaxial layer of silicon. It has a doping of p+ (Boron) and is grown upon the 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. The gate oxide, i.e. the capacitor dielectric, is grown on top of the epitaxial layer and substrate. Later on 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 channels 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). Epitaxy is a specialized thin-film deposition technique. ...
DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ...
Photolithography is a process used in semiconductor device fabrication to transfer a pattern from a photomask (also called reticle) to the surface of a substrate. ...
Polycrystalline silicon or polysilicon or poly-Si is a material consisting of multiple small silicon crystals, and has long been used as the conducting gate material in MOSFET and CMOS processing technologies. ...
One should note that 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. A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
It should be noted that 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.
Architecture 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 will smear 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. A frame transfer CCD is a specialized CCD, often used in astronomy, designed for high exposure efficiency and correctness. ...
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% 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% 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 hungry mechanical shutter, then 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 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 addressed. Today, the choice of frame-transfer is usually made when an interline architecture is not available, such as in a back-illuminated device.
Applications CCDs containing grids of pixels are used in digital cameras, optical scanners and video cameras as light-sensing devices. They commonly respond to 70% of the incident light (meaning a quantum efficiency of about 70%) making them more efficient than photographic film, which captures only about 2% of the incident light. As a result CCDs were rapidly adopted by astronomers. This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ...
A SiPix digital camera next to a matchbox to show scale. ...
In computing, a scanner is a device that analyzes an image (such as a photograph, printed text, or handwriting) or an object (such as an ornament) and converts it to a digital image. ...
A graph showing variation of quantum efficiency with wavelength of the CCD chips in the Hubble Space Telescopes Wide Field and Planetary Camera 2. ...
Undeveloped Arista black and white film, ISO 125. ...
An image is projected by a lens on the capacitor array, 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, while a two-dimensional array, used in video and still cameras, captures the whole image or a rectangular portion of it. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbour. The last capacitor in the array dumps its charge into an amplifier that converts the charge into a voltage. By repeating this process, the control circuit converts the entire contents of the array to a varying voltage, which it samples, digitizes and stores in memory. Stored images can be transferred to a printer, storage device or video display. CCDs are also widely used as sensors for astronomical telescopes, and night vision devices. Image File history File links Download high resolution version (2006x679, 211 KB) Summary CCD line sensor in a ceramic dual in-line package, soldered on a printed circuit board. ...
Image File history File links Download high resolution version (2006x679, 211 KB) Summary CCD line sensor in a ceramic dual in-line package, soldered on a printed circuit board. ...
A lens. ...
Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength [citation needed]. The elementary particle that defines light is the photon. ...
Generally, an amplifier is any device that uses a small amount of energy to control a larger amount of energy. ...
now. ...
50 cm refracting telescope at Nice Observatory. ...
An interesting astronomical application is to use 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.
CCDs are typically sensitive to infrared light, which allows infrared photography, night-vision devices, and zero lux (or near zero lux) video-recording/photography. Because of their sensitivity to infrared, CCDs used in astronomy are usually cooled to liquid nitrogen temperatures, because infrared black body radiation is emitted from room-temperature sources. One other consequence of their sensitivity to infrared is that infrared from remote controls will often appear on CCD-based digital cameras or camcorders if they don't have infrared blockers. Cooling also reduces the array's dark current, improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...
Top: tree photographed in the near infrared range. ...
It has been suggested that Night vision goggles be merged into this article or section. ...
The lux (symbol: lx) is the SI derived unit of illuminance or illumination. ...
As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ...
A television remote control A DVDplayer remote control A remote control is an electronic device used for the remote operation of a machine. ...
In electricity, current refers to electric current, which is the flow of electric charge. ...
Thermal noise, dark current, and cosmic rays may alter the pixels in the CCD array. To counter such effects, astronomers take an average of 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 in the CCD (dead pixels, hot pixels, etc). Ray may refer to: A fish in the order Batoidea, especially true rays of the family Rajiformes, such as stingrays Ray (optics), an idealized narrow beam of light An electrical ray, an old name for a laser beam Radiation, emission of energy in the form of waves or particles Ray...
CCD cameras used in astrophotography often require very sturdy mounts to cope with vibrations and breezes, along with the tremendous weight that most imaging platforms inherently cause. To take long CCD exposures of galaxies and nebulae, many astronomers use a technique known as auto-guiding. Most autoguiders use off-axis CCD chips to monitor any deviation from the imaging, however, some have the autoguider CCD and the imaging CCD in the same camera. Auto-guiders use a second CCD chip which can rapidly detect period errors in tracking and command the mount's motors to correct for them. Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ...
Color cameras 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. The Bayer arrangement of color filters on the pixel array of an image sensor Front page of Dr. Bryce Bayers 1976 patent on the Bayer pattern filter mosaic, showing his terminology of luminance-sensitive and chrominance-sensitive elements A Bayer filter mosaic is a color filter array (CFA) for...
The human eye. ...
Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ...
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. Some semi-professional digital video camcorders (and all professionals) use this technique. 3CCD is a term used to describe an imaging system used used by some video camcorders. ...
A beam splitter is an optical device, that splits a beam of light in two. ...
If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ...
For images in Wikipedia, see Wikipedia:Images. ...
Red may be any of a number of similar colors at the lowest frequencies of light discernible by the human eye. ...
Green is a color with many different shades, all within a wavelength of roughly 520–570 nm. ...
The term Blue may refer any of a number of similar colors. ...
Since a very-high-resolution CCD chip is very expensive as of 2005, a 3CCD 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 objects that are not moving. 2005 is a common year starting on Saturday of the Gregorian calendar. ...
See also |
Feeds |
Contact