A CCD image sensor on a flexible circuit board

Image sensor on the motherboard of a Nikon Coolpix L2 6 MP

An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras, camera modules and other imaging devices. Early analog sensors were video camera tubes, most currently used are digital charge-coupled device (CCD) or complementary metal–oxide–semiconductor (CMOS) active pixel sensors.

CCD vs CMOS[link]

Today, most digital still cameras use either a CCD image sensor or a CMOS sensor. Both types of sensor accomplish the same task of capturing light and converting it into electrical signals.

A CCD image sensor is an analog device. When light strikes the chip it is held as a small electrical charge in each photo sensor. The charges are converted to voltage one pixel at a time as they are read from the chip. Additional circuitry in the camera converts the voltage into digital information.

A CMOS imaging chip is a type of active pixel sensor made using the CMOS semiconductor process. Extra circuitry next to each photo sensor converts the light energy to a voltage. Additional circuitry on the chip may be included to convert the voltage to digital data.

Neither technology has a clear advantage in image quality. On one hand, CCD sensors are more susceptible to vertical smear from bright light sources when the sensor is overloaded; high-end frame transfer CCDs in turn do not suffer from this problem. On the other hand, CMOS sensors are susceptible to undesired effects that come as a result of rolling shutter.

CMOS can potentially be implemented with fewer components, use less power, and/or provide faster readout than CCDs. CCD is a more mature technology and is in most respects the equal of CMOS.^[1][2] CMOS sensors are less expensive to manufacture than CCD sensors.

Another hybrid CCD/CMOS architecture, sold under the name "sCMOS", consists of CMOS readout integrated circuits (ROICs) that are bump bonded to a CCD imaging substrate – a technology that was developed for infrared staring arrays and now adapted to silicon-based detector technology.^[3] Another approach is to utilize the very fine dimensions available in modern CMOS technology to implement a CCD like structure entirely in CMOS technology. This can be achieved by separating individual poly-silicon gates by a very small gap. These hybrid sensors are still in the research phase, and can potentially harness the benefits of both the CCDs and the CMOS imagers.^[4]

Performance[link]

An infrared-blocking filter removed from a Canon EOS 350D DSLR.

There are many parameters that can be used to evaluate the performance of an image sensor, including its dynamic range, its signal-to-noise ratio, its low-light sensitivity, etc. For sensors of comparable types, the signal-to-noise ratio and dynamic range improve as the size increases.

Color separation[link]

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

• Bayer sensor, low-cost and most common, using a color filter array that passes red, green, or blue light to selected pixel sensors, forming interlaced grids sensitive to red, green, and blue – the missing color samples are interpolated using a demosaicing algorithm. In order to avoid interpolated color information, techniques like color co-site sampling use a piezo mechanism to shift the color sensor in pixel steps. The Bayer sensors also include back-illuminated sensors, where the light enters the sensitive silicon from the opposite side of where the transistors and metal wires are, such that the metal connections on the devices side are not an obstacle for the light, and the efficiency is higher.^[3][4]
• 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.
• 3CCD, using three discrete image sensors, with the color separation done by a dichroic prism. Considered the best quality, and generally more expensive than single-CCD sensors.

Specialty sensors[link]

Special sensors are used in various applications such as thermography, creation of multi-spectral images, video laryngoscopes, gamma cameras, sensor arrays for x-rays, and other highly sensitive arrays for astronomy.

Sensors used in digital cameras[link]

Width	Height	Aspect ratio	Actual pixel count	Megapixels	Camera examples
100	100	1:1	10,000	0.01	Kodak (by Steven Sasson) Prototype (1975)
640	480		307,200	0.3	Apple QuickTake 100 (1994)
832	608		505,856	0.5	Canon Powershot 600 (1996)
1,024	768		786,432	0.8	Olympus D-300L (1996)
1024	1024	1:1	1,048,576	1.0	Nikon NASA F4 (1991)
1,280	960		1,228,800	1.3	Fujifilm DS-300 (1997)
1,280	1,024	5:4	1,310,720	1.3	Fujifilm MX-700, Fujifilm MX-1700 (1999), Leica Digilux (1998), Leica Digilux Zoom (2000)
1,600	1,200		1,920,000	2	Nikon Coolpix 950, Samsung GT-S3500
2,012	1,324		2,663,888	2.74	Nikon D1
2,048	1,536		3,145,728	3	Canon PowerShot A75, Nikon Coolpix 995
2,272	1,704		3,871,488	4	Olympus Stylus 410, Contax i4R (although CCD is actually square 2,272x2,272)
2,464	1,648		4,060,672	4.1	Canon 1D
2,560	1,920		4,915,200	5	Olympus E-1, Sony Cyber-shot DSC-F707, Sony Cyber-shot DSC-F717
2,816	2,112		5,947,392	5.9	Olympus Stylus 600 Digital
3,008	2,000		6,016,000	6	Nikon D40, D50, D70, D70s, Pentax K100D, Konica Minolta Maxxum 7D, Konica Minolta Maxxum 5D
3,072	2,048		6,291,456	6.3	Canon EOS 10D, Canon EOS 300D
3,072	2,304		7,077,888	7	Olympus FE-210, Canon PowerShot A620
3,456	2,304		7,962,624	8	Canon EOS 350D
3,264	2,448		7,990,272	8	Olympus E-500, Olympus SP-350, Canon PowerShot A720 IS, Apple iPhone 4S
3,504	2,336		8,185,344	8.2	Canon EOS 30D, Canon EOS-1D Mark II, Canon EOS-1D Mark II N
3,520	2,344		8,250,880	8.25	Canon EOS 20D
3,648	2,736		9,980,928	10	Canon PowerShot G11, Canon PowerShot G12, Canon PowerShot S90, Canon PowerShot S95, Nikon CoolPix P7000, Nikon CoolPix P7100, Olympus E-410, Olympus E-510, Panasonic FZ50, Fujifilm FinePix HS10, Samsung EX1
3,872	2,592		10,036,224	10	Nikon D40x, Nikon D60, Nikon D3000, Nikon D200, Nikon D80, Pentax K10D, Pentax K200D, Sony Alpha A100
3,888	2,592		10,077,696	10.1	Canon EOS 40D, Canon EOS 400D, Canon EOS 1000D
4,064	2,704		10,989,056	11	Canon EOS-1Ds
4,000	3,000		12,000,000	12	Canon Powershot G9, Fujifilm FinePix S200EXR, Nikon Coolpix L110
4,256	2,832		12,052,992	12.1	Nikon D3, Nikon D3S, Nikon D700, Fujifilm FinePix S5 Pro
4,272	2,848		12,166,656	12.2	Canon EOS 450D
4,032	3,024		12,192,768	12.2	Olympus PEN E-P1
4,288	2,848		12,212,224	12.2	Nikon D2Xs/D2X, Nikon D300, Nikon D300S, Nikon D90, Nikon D5000, Pentax K-x
4,900	2,580		12,642,000	12.6	RED ONE Mysterium
4,368	2,912		12,719,616	12.7	Canon EOS 5D
5,120	2,700		13,824,000	13.8	RED Mysterium-X
7,920 (2,640 × 3)	1,760		13,939,200	13.9	Sigma SD14, Sigma DP1 (3 layers of pixels, 4.7 MP per layer, in Foveon X3 sensor)
4,672	3,104		14,501,888	14.5	Pentax K20D, Pentax K-7
4,752	3,168		15,054,336	15.1	Canon EOS 50D, Canon EOS 500D
4,928	3,262		16,075,136	16.1	Nikon D7000, Pentax K-5
4,992	3,328		16,613,376	16.6	Canon EOS-1Ds Mark II, Canon EOS-1D Mark IV
5,184	3,456		17,915,904	17.9	Canon EOS 7D, Canon EOS 60D, Canon EOS 600D, Canon EOS 550D
5,270	3,516		18,529,320	18.5	Leica M9
5,616	3,744		21,026,304	21.0	Canon EOS-1Ds Mark III, Canon EOS-5D Mark II
6,048	4,032		24,385,536	24.4	Sony α 850, Sony α 900, Nikon D3X
7,360	4,912		36,152,320	36.2	Nikon D800
7,500	5,000		37,500,000	37.5	Leica S2
7,212	5,142		39,031,344	39.0	Hasselblad H3DII-39
7,216	5,412		39,052,992	39.1	Leica RCD100
7,264	5,440		39,516,160	39.5	Pentax 645D
7,320	5,484		40,142,880	40.1	Phase One IQ140
7,728	5,368	100:69	41,483,904	41.5	Nokia 808 PureView
8,176	6,132		50,135,232	50.1	Hasselblad H3DII-50, Hasselblad H4D-50
11,250	5,000	9:4	56,250,000	56.3	Better Light 4000E-HS (scanned)
8,956	6,708		60,076,848	60.1	Hasselblad H4D-60
8,984	6,732		60,480,288	60.5	Phase One IQ160, Phase One P65+
10,320	7,752		80,000,640	80	Leaf Aptus-II 12, Leaf Aptus-II 12R
10,328	7,760		80,145,280	80.1	Phase One IQ180
9,372	9,372	1:1	87,834,384	87.8	Leica RC30
12,600	10,500	6:5	132,300,000	132.3	Phase One PowerPhase FX/FX+ (scanned)
18,000	8,000	9:4	144,000,000	144	Better Light 6000-HS/6000E-HS (scanned)
21,250	7,500	17:6	159,375,000	159.4	Seitz 6x17 Digital (scanned)
16,352*	12,264*		200,540,928	200.5	Hasselblad H4D-200MS (*actuated)
18,000	12,000		216,000,000	216	Better Light Super 6K-HS (scanned)
24,000	15,990	2,400:1,599	383,760,000	383.8	Better Light Super 8K-HS (scanned)
30,600	13,600	9:4	416,160,000	416.2	Better Light Super 10K-HS (scanned)
62,830	7,500	6,283:750	471,225,000	471.2	Seitz Roundshot D3 (80 mm lens) (scanned)
62,830	13,500	6,283:1,350	848,205,000	848.2	Seitz Roundshot D3 (110 mm lens) (scanned)
38,000	38,000	1:1	1,444,000,000	1,444	Pan-STARRS PS1
157,000	18,000	157:18	2,826,000,000	2,826	Better Light 300 mm lens Digital (scanned)

Companies[link]

The largest companies that manufacture imaging sensors include the following:

• Agilent
• Aptina
• Canesta
• Canon
• Cypress Semiconductor
• Eastman Kodak
• ESS Technology
• Fujifilm
• MagnaChip
• Matsushita
• Micron Technology
• Mitsubishi
• Nikon
• OmniVision Technologies
• PixArt Imaging
• Pixim
• Samsung
• Sharp
• Sony
• STMicroelectronics
• Toshiba
• TowerJazz
• TransChip
• Trusight

See also[link]

• Video camera tube
• Semiconductor detector
• Full-frame digital SLR
• Image sensor format, the sizes and shapes of common image sensors
• Color filter array, mosaic of tiny color filters over color image sensors
• Sensitometry, the scientific study of light-sensitive materials
• History of television, the development of electronic imaging technology since the 1880s.
• List of large sensor interchangeable-lens video cameras

References[link]

External links[link]

• CCD vs CMOS. Performance comparison
• Digital Camera Sensor Performance Summary by Roger Clark.