Milestones:Charge-Coupled Device, 1969

Title

Charge-Coupled Device, 1969

Citation

The charge-coupled device (CCD), originally conceived for digital memory applications, was later shown to offer a compact, sensitive, and efficient way to convert light into digital signals by storing light-generated charges in a series of tiny capacitors. Invented and developed by Bell Labs scientists Willard Boyle, George Smith, and Michael Tompsett, CCDs found wide use in astronomical instruments, medical imaging, and consumer electronics.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

600 Mountain Avenue, Murray Hill, NJ 07974 40.684031, -74.401783, 600 Mountain Avenue, Murray Hill, NJ 07974 40.684031, -74.401783

Details of the physical location of the plaque

On a wall in the front lobby, to left of reception desk.

How the plaque site is protected/secured

There is security in the lobby.

Historical significance of the work

Justification for Inclusion of Names(s) In 2009, Willard Boyle and George E. Smith were awarded the Nobel Prize in Physics "for the invention of an imaging semiconductor circuit – the CCD sensor". Boyle and Smith worked together on the initial design and fabrication of the CCD at AT&T Bell Labs in Murray Hill, NJ and are the only authors of the key patents surrounding this invention. Michael Tompsett, a colleague of Boyle and Smith at Bell Labs, realized the use of the CCD as a useful imaging device with wide application.

Charge-coupled device

A charge-coupled device (CCD) is an integrated circuit containing a silicon semiconductor device and an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCDs are used in digital cameras, optical scanners and video cameras as image sensors. They have also found uses in astronomy and spectroscopy.

Prior to CCD, there were a number of analog image sensors such as the Vidicon TV camera tube. Initially, these were better quality than the original CCD. However, they were expensive, fragile, and required a high voltage. Key benefits of the CCD included power efficiency, ruggedness, reliability, and the ability to do long exposures well. As the CCD is an analog device, it requires an external A/D converter to provide a digital output.

History

The CCD was invented on October 17, 1969, at AT&T Bell Labs by Willard Boyle and George E. Smith.[1] and key patents associated with this discover are US Patent 3,792,322 “Buried Channel Charge Coupled Devices” ; Willard S. Boyle and George E. Smith and US Patent 3,796,927 “Three Dimensional Charge Coupled Devices” ; Willard S. Boyle and George E. Smith. For their work, Boyle and Smith were awarded the Nobel Prize in Physics in 2009.[2]. The initial concept was a memory device, in which data could be transferred along the surface of a semiconductor. However, within a short time, the potential of the device to collect and read out signals produced by light was recognized.

Boyle and Smith were tasked by Jack Morton, Bell Labs' vice president of Electronics Technology, to create a solid-state bubble memory device. They drew inspiration from the magnetic bubble memory work being done at Bell Labs at the time. In a brainstorming session lasting less than an hour, they sketched out the basic structure of what was originally called a "charge bubble device" and outlined its principle of operation. Later this structure became known as the Charge-Coupled Device or CCD.

The first experimental device demonstrating the principle was fabricated by Michael Tompsett, George Amelio, and Bill Bertram in 1970.[3] This device had 8 bits and was a linear array. Tompsett also received a patent on the first application of CCDs for imaging applications. By 1971, Bell Labs researchers had produced the first area imaging CCD array with 100 x 100 pixels.

Basic principles

A CCD is a silicon chip with a two-dimensional array of metal-oxide-semiconductor (MOS) capacitors. These capacitors are called "pixels" and are arranged in columns and rows. When light falls on a pixel, it generates electrons through the photoelectric effect. These electrons are stored in a potential well beneath the capacitor.

The CCD operates by shifting these stored charges from one capacitor to the next, controlled by a sequence of voltage pulses applied to the electrodes. This process is called "charge coupling". At the end of each column, the charge is amplified and converted to a voltage. By repeating this process for each row, the entire image can be read out.

Key features of CCDs include:

1. High sensitivity to light

2. Low noise

3. Good linearity and dynamic range

4. Ability to integrate light over long periods

Structure and operation

A typical CCD consists of several main components:

1. Photosensitive area: An array of MOS capacitors that convert light into electrical charge.

2. Shift register: A series of electrodes that move the charge packets across the device.

3. Output amplifier: Converts the charge packets into a voltage signal.

4. Control circuitry: Generates the timing signals to operate the device.

The operation of a CCD can be broken down into four main steps:

1. Charge generation: Photons striking the silicon create electron-hole pairs.

2. Charge collection: The electrons are collected in potential wells beneath the electrodes.

3. Charge transfer: The collected charge is shifted across the device by manipulating the voltages on the electrodes.

4. Charge measurement: The charge is converted to a voltage and amplified.

Types of CCDs

Several types of CCD architectures have been developed:

1. Full-frame CCD: The entire array is used for both image capture and readout. This requires a mechanical shutter to prevent smearing during readout.

2. Frame-transfer CCD: The array is divided into two areas - one for image capture and one for storage. The image is quickly transferred to the storage area, allowing for faster operation.

3. Interline-transfer CCD: Alternating columns of pixels are masked for storage. This allows for electronic shuttering but reduces the light-sensitive area.

4. Time-delay and integration (TDI) CCD: Used for imaging moving objects, this type of CCD shifts the charge in synchronization with the object's movement.

Applications

CCDs have found widespread use in various fields:

1. Digital photography: CCDs were the dominant image sensor in digital cameras until the mid-2000s when CMOS sensors became more prevalent.

2. Astronomy: CCDs are widely used in telescopes due to their high sensitivity and ability to integrate light over long periods.

3. Spectroscopy: CCDs are used to detect and measure light in spectroscopic instruments.

4. Medical imaging: CCDs are used in various medical imaging devices, including those for endoscopy and microscopy.

5. Machine vision: CCDs are used in industrial applications for quality control and automation.

Limitations and alternatives

While CCDs offer excellent image quality, they have some limitations:

1. Blooming: When a pixel becomes saturated with charge, it can overflow into adjacent pixels.

2. Smearing: In some CCD architectures, bright light sources can cause vertical streaks in the image.

3. Power consumption: CCDs typically require higher voltages and consume more power than CMOS sensors.

4. Cost: The specialized manufacturing process for CCDs makes them more expensive than CMOS sensors.

Due to these limitations, CMOS image sensors have largely replaced CCDs in many consumer applications, particularly in smartphones and low-cost digital cameras. However, CCDs continue to be used in high-end scientific and industrial applications where their superior image quality is crucial.

Nobel Prize

In 2009, Willard Boyle and George E. Smith were awarded the Nobel Prize in Physics "for the invention of an imaging semiconductor circuit – the CCD sensor".[2] They shared the prize with Charles K. Kao, who was recognized for his work on fiber optic communication.

The Nobel Committee highlighted the importance of the CCD in digital imaging technology and its wide-ranging applications in science and everyday life. The invention of the CCD has been described as a cornerstone in the development of digital photography and has had a profound impact on fields such as astronomy, medicine, and consumer electronics.

[1] W.S. Boyle and G. E. Smith, "Charge Coupled Semiconductor Devices" BSTJ 29 January 1970, pp 587-593

[2] The Nobel Prize in Physics 2009. NobelPrize.org.

[3] Tompsett M. F, et al "Charge-Coupled Imaging Devices: Experimental Results" IEEE Trans on Electron Devices v ED-18, No.11, November 1971, pp992-996

Obstacles that needed to be overcome

The invention of the CCD was sparked by the commercial need for a compact solid-state based memory which could be read out in a serial fashion, similar to the magnetic bubble memory. The inventors quickly realized that their solution could solve an even more challenging problem: the accurate collection and read-out of charges induced by photons illuminating a photo-sensitive area integrated on a semiconductor. Building the first operational CCD required the development and processing of precise and novel semiconductor layers to capture, isolate and hold the photo-induced charges. Additionally, it required a completely new electronic circuit to accurately transfer these charges to the perimeter of the CCD array such that they could be read out sequentially and a 2-D image could be formed.

Features that set this work apart from similar achievements

The CCD array was the first implementation of a fully integrated solid-state imager. It combined the collection, storage and read-out of photon-induced charges in a single two-dimensional array. It enabled the capture and read-out of high-quality images using a very compact form factor. As such, CCD's were rapidly adopted and revolutionized the field of photography and video recording until then dominated by film or vacuum tubes. Thanks to their high sensitivity spanning from infrared to UV, CCD's enabled many scientific discoveries in fields like astronomy.

Significant references

W.S. Boyle and G. E. Smith, "Charge Coupled Semiconductor Devices" BSTJ 29 January 1970, pp 587-593

Tompsett M. F, et al "Charge-Coupled Imaging Devices: Experimental Results" IEEE Trans on Electron Devices v ED-18, No.11, November 1971, pp992-996

W.S. Boyle, G.E. Smith, "Charge coupled devices - A new approach to MIS device structures" IEEE Spectrum v8, #7, 1971

US Patent 3796927 12 March 1974, "Three Dimensional Charge Coupled Devices"

W.S. Boyle, G.E. Smith, "The Inception of Charge-Coupled Devices" IEEE Trans on Electron Devices v ED-23, #7 1976 pp661-663

References

1. Boyle, W. S., & Smith, G. E. (1970). Charge coupled semiconductor devices. Bell System Technical Journal, 49(4), 587-593.

2. Amelio, G. F., Bertram, W. J., & Tompsett, M. F. (1970). Charge-coupled imaging devices: Design considerations. IEEE Transactions on Electron Devices, 18(11), 986-992.

3. Tompsett, M. F., Amelio, G. F., Bertram, W. J., Buckley, R. R., McNamara, W. J., Mikkelsen, J. C., & Sealer, D. A. (1970). Charge-coupled imaging devices: Experimental results. IEEE Transactions on Electron Devices, 18(11), 992-996.

4. Boyle, W. S., & Smith, G. E. (1976). Charge coupled semiconductor devices. IEEE Transactions on Electron Devices, 23(7), 661-663.

5. Janesick, J. R. (2001). Scientific charge-coupled devices. SPIE press.

6. Fossum, E. R. (1997). CMOS image sensors: Electronic camera-on-a-chip. IEEE transactions on electron devices, 44(10), 1689-1698.

7. The Nobel Prize in Physics 2009. NobelPrize.org. Nobel Prize Outreach AB 2023.

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