Image sensor: Difference between revisions

Revision as of 02:05, 9 June 2023

Revision as of 23:05, 23 July 2023

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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 journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |title=Active pixel sensors: are CCDs dinosaurs? |journal=SPIE Proceedings Vol. 1900: Charge-Coupled Devices and Solid State Optical Sensors III |series=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 |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.{{Citation needed|date=May 2023}}

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[[File:Absorption-X3.svg|right|thumb|200px|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 journal |last=Dillon |first=Peter |date=Dec 1976 |title=Integral color filter arrays for solid-state imagers |url=https://ieeexplore.ieee.org/document/1478779 |journal=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 |url=https://ieeexplore.ieee.org/document/1484879}}</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 |url=https://ieeexplore.ieee.org/document/1479439}}</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 |url=https://ieeexplore.ieee.org/document/1479440}}</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.

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The basis for modern solid-state image sensors is MOS technology,<ref name="Williams">{{cite book |last1=Williams |first1=J. B. |title=The Electronics Revolution: Inventing the Future |date=2017 |publisher=Springer |isbn=9783319490885 |pages=245–8 |url=https://books.google.com/books?id=v4QlDwAAQBAJ&pg=PA245}}</ref><ref name="Ohta">{{cite book |last1=Ohta |first1=Jun |title=Smart CMOS Image Sensors and Applications |date=2017 |publisher=[[CRC Press]] |isbn=9781420019155 |page=2 |url=https://books.google.com/books?id=_7NLzflrTrcC&pg=PA2}}</ref> which originates from the invention of the MOSFET by [[Mohamed M. Atalla]] and [[Dawon Kahng]] at [[Bell Labs]] in 1959.<ref name="computerhistory">{{cite journal|url=https://www.computerhistory.org/siliconengine/metal-oxide-semiconductor-mos-transistor-demonstrated/|title=1960: Metal Oxide Semiconductor (MOS) Transistor Demonstrated|journal=The Silicon Engine|publisher=[[Computer History Museum]] |access-date=August 31, 2019}}</ref> Later research on MOS technology led to the development of solid-state [[semiconductor]] image sensors, including the [[charge-coupled device]] (CCD) and later the [[active-pixel sensor]] ([[CMOS]] sensor).<ref name="Williams"/><ref name="Ohta"/>

The [[passive-pixel sensor]] (PPS) was the precursor to the active-pixel sensor (APS).<ref name="Fossum2014"/> A PPS consists of passive pixels which are read out without [[amplifier|amplification]], with each pixel consisting of a photodiode and a [[MOSFET]] switch.<ref name="Kozlowski">{{cite journal |last1=Kozlowski |first1=L. J. |last2=Luo |first2=J. |last3=Kleinhans |first3=W. E. |last4=Liu |first4=T. |editor-first1=Bedabrata |editor-first2=Terrence S. |editor-last1=Pain |editor-last2=Lomheim |title=Comparison of passive and active pixel schemes for CMOS visible imagers |journal=Infrared Readout Electronics IV |date=14 September 1998 |volume=3360 |pages=101–110 |doi=10.1117/12.584474 |bibcode=1998SPIE.3360..101K |url=https://www.researchgate.net/publication/268189518 |publisher=International Society for Optics and Photonics|s2cid=123351913 }}</ref> It is a type of [[photodiode array]], with pixels containing a [[p-n junction]], integrated [[capacitor]], and MOSFETs as selection [[transistors]]. A photodiode array was proposed by G. Weckler in 1968.<ref name=fossum93>{{cite journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |title=Active pixel sensors: are CCDs dinosaurs? |journal=SPIE Proceedings Vol. 1900: Charge-Coupled Devices and Solid State Optical Sensors III |series=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> This was the basis for the PPS.<ref name="Fossum2014"/> These early photodiode arrays were complex and impractical, requiring selection transistors to be fabricated within each pixel, along with [[integrated circuit|on-chip]] [[multiplexer]] circuits. The [[noise (electronics)|noise]] of photodiode arrays was also a limitation to performance, as the photodiode readout [[memory bus|bus]] capacitance resulted in increased noise level. [[Correlated double sampling]] (CDS) could also not be used with a photodiode array without external [[computer memory|memory]].<ref name=fossum93/> However, in 1914 Deputy Consul General Carl R. Loop, reported to the state department in a Consular Report on [[Archibald Low|Archibald M. Low's]] Televista system that "It is stated that the selenium in the transmitting screen may be replaced by any [[Diamagnetism|diamagnetic material]]".<ref>Daily Consular Reports No 76–152 Seventeenth Year April, May, June 1914 Page 1731 https://books.google.com/books?id=6VE_AQAAMAAJ</ref>

In June 2022, Samsung Electronics announced that it had created a 200 million pixel image sensor. The 200MP ISOCELL HP3 has 0.56 micrometer pixels with Samsung reporting that previous sensors had 0.64 micrometer pixels, a 12% decrease since 2019. The new sensor contains 200 million pixels in a 2 x 1.4 inch lens.<ref>{{cite news |last=Web |first=Desk |url=https://www.bolnews.com/pakistan/2022/06/samsung-electronics-releases-a-sensor-with-200-million-pixels/ |title=Samsung Electronics releases a sensor with 200 million pixels |work=BOL News |date=2022-06-25 |accessdate=2022-06-25 }}</ref>

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{{Main|Active-pixel sensor}}

The [[NMOS logic|NMOS]] [[active-pixel sensor]] (APS) was invented by [[Olympus Corporation|Olympus]] in Japan during the mid-1980s. This was enabled by advances in MOS [[semiconductor device fabrication]], with [[MOSFET scaling]] reaching smaller [[List of semiconductor scale examples|micron and then sub-micron]] levels.<ref name=fossum93>{{cite journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |title=Active pixel sensors: are CCDs dinosaurs? |journal=SPIE Proceedings Vol. 1900: Charge-Coupled Devices and Solid State Optical Sensors III |series=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>{{cite journal |last1=Fossum |first1=Eric R. |author1-link=Eric Fossum |title=Active Pixel Sensors |website=[[Semantic Scholar]] |year=2007 |s2cid=18831792 |url=http://pdfs.semanticscholar.org/f510/d40cfe0556392bb2d34981f7158327dec169.pdf |archive-url=https://web.archive.org/web/20190309065505/http://pdfs.semanticscholar.org/f510/d40cfe0556392bb2d34981f7158327dec169.pdf |url-status=dead |archive-date=9 March 2019 |access-date=8 October 2019}}</ref> The first NMOS APS was fabricated by Tsutomu Nakamura's team at Olympus in 1985.<ref>{{cite journal |last1=Matsumoto |first1=Kazuya |last2=Nakamura |first2=Tsutomu |last3=Yusa |first3=Atsushi |last4=Nagai |first4=Shohei |display-authors=1|date=1985 |title=A new MOS phototransistor operating in a non-destructive readout mode |journal=Japanese Journal of Applied Physics |volume=24 |issue=5A |page=L323|doi=10.1143/JJAP.24.L323 |bibcode=1985JaJAP..24L.323M |s2cid=108450116 }}</ref> The [[CMOS]] active-pixel sensor (CMOS sensor) was later improved by a group of scientists at the [[NASA]] [[Jet Propulsion Laboratory]] in 1993.<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 |doi-access=free }}</ref> By 2007, sales of CMOS sensors had surpassed CCD sensors.<ref>{{cite news |title=CMOS Image Sensor Sales Stay on Record-Breaking Pace |url=http://www.icinsights.com/news/bulletins/CMOS-Image-Sensor-Sales-Stay-On-RecordBreaking-Pace/ |access-date=6 October 2019 |work=IC Insights |date=May 8, 2018}}</ref> By the 2010s, CMOS sensors largely displaced CCD sensors in all new applications.

===Other image sensors===