Image sensor: Difference between revisions

Revision as of 13:18, 16 July 2025

Latest revision as of 13:01, 26 August 2025

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[[File:Image sensor and motherbord nikon coolpix l2.JPG|thumb|Image sensor (upper left) on the motherboard of a {{nowrap|Nikon Coolpix L2 6 MP}}]]

The two main types of [[digital image]] sensors are the [[charge-coupled device]] (CCD) and the [[active-pixel sensor]] (CMOS sensor), [[semiconductor device fabrication|fabricated]] in [[complementary MOS]] (CMOS) or [[N-type semiconductor|N-type]] MOS ([[NMOS logic|NMOS]] or [[Live MOS]]) technologies. Both CCD and CMOS sensors are based on the [[MOS technology]],<ref>{{cite book |last1=Cressler |first1=John D. |title=Silicon Earth: Introduction to Microelectronics and Nanotechnology, Second Edition |date=2017 |publisher=[[CRC Press]] |isbn=978-1-351-83020-1 |chapter=Let There Be Light: The Bright World of Photonics |page=29 |chapter-url=https://books.google.com/books?id=i-5HDwAAQBAJ&pg=SA12-PA29}}</ref> with [[MOS capacitor]]s being the building blocks of a CCD,<ref>{{cite book |last1=Sze |first1=Simon Min |author1-link=Simon Sze |last2=Lee |first2=Ming-Kwei |chapter=MOS Capacitor and MOSFET |title=Semiconductor Devices: Physics and Technology : International Student Version |date=May 2012 |publisher=[[John Wiley & Sons]] |isbn=9780470537947 |chapter-url=https://www.oreilly.com/library/view/semiconductor-devices-physics/9780470537947/13_chap05.html |access-date=6 October 2019}}</ref> and [[MOSFET]] amplifiers being the building blocks of a CMOS sensor.<ref name="fossum93">{{cite book |last1=Fossum |first1=Eric R. |chapter=Active pixel sensors: Are CCDS dinosaurs? |author1-link=Eric Fossum |title=Charge-Coupled Devices and Solid State Optical Sensors III |volume=1900 |date=12 July 1993 |doi=10.1117/12.148585 |bibcode=1993SPIE.1900....2F |publisher=International Society for Optics and Photonics |pages=2–14 |editor1-last=Blouke |editor1-first=Morley M.|citeseerx=10.1.1.408.6558 |s2cid=10556755 }}</ref><ref name="Fossum2014">{{cite journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |last2=Hondongwa |first2=D. B. |title=A Review of the Pinned Photodiode for CCD and CMOS Image Sensors |journal=IEEE Journal of the Electron Devices Society |date=2014 |volume=2 |issue=3 |pages=33–43 |doi=10.1109/JEDS.2014.2306412 |bibcode=2014IJEDS...2...33F |doi-access=free }}</ref>

Cameras integrated in small consumer products generally use CMOS sensors, which are usually cheaper and have lower power consumption in battery powered devices than CCDs.<ref>{{cite web |url=http://www.techhive.com/article/246931/cmos_is_winning_the_camera_sensor_battle_and_heres_why.html |title=CMOS Is Winning the Camera Sensor Battle, and Here's Why |website=techhive.com |date=2011-12-29 |access-date=2017-04-27 |url-status=live |archive-url=https://web.archive.org/web/20170501024004/http://www.techhive.com/article/246931/cmos_is_winning_the_camera_sensor_battle_and_heres_why.html |archive-date=2017-05-01 }}</ref> CCD sensors are used for high end broadcast quality video cameras, and CMOS sensors dominate in still photography and consumer goods where overall cost is a major concern. Both types of sensor accomplish the same task of capturing light and converting it into electrical signals.

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[[File:Absorption-X3.svg|thumb|Foveon's scheme of vertical filtering for color sensing]]

There are several main types of color image sensors, differing by the type of color-separation mechanism:

* '''Integral color sensors'''<ref>{{Cite conference <!-- Citation bot no -->|last=Dillon |first=Peter |title=1976 International Electron Devices Meeting |chapter=Integral color filter arrays for solid state imagers |date=Dec 1976 |chapter-url=https://ieeexplore.ieee.org/document/1478779 |conference=Technical Digest International Electron Device Meeting (IEDM), Washington, DC, Dec 1976 |pages=400–403 |doi=10.1109/IEDM.1976.189067 |s2cid=35103154 |via=IEEE}}</ref> use a [[color filter array]] fabricated on top of a single monochrome CCD or CMOS image sensor. The most common color filter array pattern, the [[Bayer pattern]], uses a checkerboard arrangement of two green pixels for each red and blue pixel, although many other color filter patterns have been developed, including patterns using cyan, magenta, yellow, and white pixels.<ref>{{Cite journal |last=Parulski |first=Kenneth |date=August 1985 |title=Color Filters and Processing Alternatives for One-chip Cameras |journal=IEEE Transactions on Electron Devices |volume=32 |issue=8 |pages=1381–1389 |doi=10.1109/T-ED.1985.22133 |bibcode=1985ITED...32.1381P |s2cid=9008653 }}</ref> Integral color sensors were initially manufactured by transferring colored dyes through photoresist windows onto a polymer receiving layer coated on top of a monochrome CCD sensor.<ref>{{Cite journal |last=Dillon |first=Peter |date=February 1978 |title=Fabrication and performance of color filter arrays for solid-state imagers |journal=IEEE Transactions on Electron Devices |volume=25 |issue=2 |pages=97–101 |doi=10.1109/T-ED.1978.19045 |bibcode=1978ITED...25...97D }}</ref> Since each pixel provides only a single color (such as green), the "missing" color values (such as red and blue) for the pixel are interpolated using neighboring pixels.<ref>{{Cite journal |last=Dillon |first=Peter |date=February 1978 |title=Color imaging system using a single CCD area array |journal=IEEE Transactions on Electron Devices |volume=25 |issue=2 |pages=102–107 |doi=10.1109/T-ED.1978.19046 |bibcode=1978ITED...25..102D }}</ref> This processing is also referred to as [[demosaicing]] or de-bayering.

* '''[[Foveon X3 sensor]]''', using an array of layered pixel sensors, separating light via the inherent wavelength-dependent absorption property of silicon, such that every ___location senses all three color channels. This method is similar to how color film for photography works.

* '''[[Three-CCD camera|3CCD]]''', using three discrete image sensors, with the color separation done by a [[dichroic prism]]. The dichroic elements provide a sharper color separation, thus improving color quality. Because each sensor is equally sensitive within its [[passband]], and at full resolution, 3-CCD sensors produce better color quality and better low light performance. 3-CCD sensors produce a full [[Chroma subsampling|4:4:4]] signal, which is preferred in [[television broadcasting]], [[video editing]] and [[chroma key]] visual effects.