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Charge-coupled device

technology Maturity 7-9 Next article →

A charge-coupled device, or CCD, is a specialized integrated circuit used for digital imaging. It consists of an array of linked, or coupled, capacitors. These tiny components work together to capture light and convert it into electrical signals. While many modern consumer devices now use CMOS sensors, CCDs remain vital for professional, medical, and scientific applications. In these fields, researchers and doctors require extremely high-quality image data.

CCD SONY ICX493AQA sensor side
CCD SONY ICX493AQA sensor side

The mechanism of a CCD relies on a process called charge transfer. The sensor contains a photoactive region, which is usually an epitaxial layer of silicon. When light enters the device through a lens, photons strike the capacitors in this region. This interaction converts the light into electron charges at the semiconductor-oxide interface. Each capacitor accumulates a charge that is proportional to the intensity of the light at that specific location.

CCD charge transfer animation
CCD charge transfer animation

Once the light exposure is complete, the device must read the data. An external control circuit manages the transfer of these charges. The capacitors act like a shift register, where each capacitor transfers its electric charge to its immediate neighbor. This happens in a specific sequence. The last capacitor in the array eventually dumps its charge into a charge amplifier. This amplifier converts the electrical charge into a voltage.

In a digital system, these voltages are sampled and digitized for storage in memory. In analog systems, such as older video cameras, the signal is processed as a continuous wave. There are different types of CCD architectures used for different tasks. For example, a one-dimensional array is used in line-scan cameras to capture a single slice of an image. In contrast, a two-dimensional array is used in video and still cameras to capture a full scene.

IECCD55-20
IECCD55-20

The history of the CCD began at Bell Labs during the late 1960s. Scientists Willard Boyle and George E. Smith were originally researching MOS technology for semiconductor bubble memory. They discovered that an electric charge could serve as an analog to a magnetic bubble. They realized they could store these charges on tiny MOS capacitors. In 1969, they invented the charge-coupled device, which they initially called "Charge 'Bubble' Devices."

Nobel Prize 2009-Press Conference KVA-19
Nobel Prize 2009-Press Conference KVA-19

Experimental progress happened very quickly after their discovery. In April 1970, Gil Amelio, Michael Francis Tompsett, and George Smith demonstrated the first experimental CCD image sensor. This device used a depleted MOS structure as a photodetector. By 1974, Fairchild Semiconductor had developed a 2D device with 100 x 100 pixels. In 1975, Steven Sasson used a CCD to invent the first digital still camera.

An RGGB Bayer Colour Filter on a 1980's vintage Sony PAL Camcorder CCD
An RGGB Bayer Colour Filter on a 1980's vintage Sony PAL Camcorder CCD

Technical improvements helped CCDs move from labs to the real world. Early sensors suffered from shutter lag, which was solved by the invention of the pinned photodiode (PPD) in 1980. This structure, developed at NEC, allowed signal carriers to transfer more efficiently with low noise. Another advancement was the interline transfer CCD, which helped reduce image smear. These innovations allowed CCDs to be used in advanced technology, such as the KH-11 KENNEN reconnaissance satellite launched in 1976.

Vertical smear
Vertical smear

The impact of this technology is recognized by the highest scientific honors. Willard Boyle and George E. Smith were awarded the Nobel Prize in Physics in 2009. Michael Tompsett also received the National Medal of Technology and Innovation for his work on CCD imagers. Today, the CCD serves as a fundamental bridge between the physical world of light and the digital world of data. It remains a cornerstone of how we observe the universe through technology.

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🖼️ Images & Media (14)
File:Delta-Doped Charged Coupled Devices (CCD) for Ultra-Violet and Visible Detection.jpg
Delta-Doped Charged Coupled Devices (CCD)...
File:Nobel Prize 2009-Press Conference KVA-19.jpg
Nobel Prize 2009-Press Conference KVA-19.jpg
File:CCD charge transfer animation.gif
CCD charge transfer animation.gif
File:CCD_SONY_ICX493AQA_sensor_side.jpg
CCD_SONY_ICX493AQA_sensor_side.jpg
File:ArgusCCD.jpg
ArgusCCD.jpg
File:CCD line sensor.JPG
CCD line sensor.JPG
File:IECCD55-20.jpg
IECCD55-20.jpg
File:Propellor with rolling-shutter artifact.jpg
Propellor with rolling-shutter artifact.jpg
File:EMCCD2 color en.svg
EMCCD2 color en.svg
File:Output vs input electrons.png
Output vs input electrons.png
File:SDSSFaceplate.gif
SDSSFaceplate.gif
File:Bayer pattern on sensor.svg
Bayer pattern on sensor.svg

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