Image sensor

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
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 CMOS 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. 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. 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.

Performance
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
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.
 * 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
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

 * {| class="wikitable sortable"

! 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
 * Aspect-ratio-4x3.svg
 * 307,200
 * 0.3
 * Apple QuickTake 100 (1994)
 * 832
 * 608
 * Aspect-ratio-4x3.svg
 * 505,856
 * 0.5
 * Canon Powershot 600 (1996)
 * 1,024
 * 768
 * Aspect-ratio-4x3.svg
 * 786,432
 * 0.8
 * Olympus D-300L (1996)
 * 1024
 * 1024
 * 1:1
 * 1,048,576
 * 1.0
 * Nikon NASA F4 (1991)
 * 1,280
 * 960
 * Aspect-ratio-4x3.svg
 * 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
 * Aspect-ratio-4x3.svg
 * 1,920,000
 * 2
 * Nikon Coolpix 950, Samsung GT-S3500
 * 2,012
 * 1,324
 * Aspect-ratio-3x2.svg
 * 2,663,888
 * 2.74
 * Nikon D1
 * 2,048
 * 1,536
 * Aspect-ratio-4x3.svg
 * 3,145,728
 * 3
 * Canon PowerShot A75, Nikon Coolpix 995
 * 2,272
 * 1,704
 * Aspect-ratio-4x3.svg
 * 3,871,488
 * 4
 * Olympus Stylus 410, Contax i4R (although CCD is actually square 2,272×2,272)
 * 2,464
 * 1,648
 * Aspect-ratio-3x2.svg
 * 4,060,672
 * 4.1
 * Canon 1D
 * 2,560
 * 1,920
 * Aspect-ratio-4x3.svg
 * 4,915,200
 * 5
 * Olympus E-1, Sony Cyber-shot DSC-F707, Sony Cyber-shot DSC-F717
 * 2,816
 * 2,112
 * Aspect-ratio-4x3.svg
 * 5,947,392
 * 5.9
 * Olympus Stylus 600 Digital
 * 3,008
 * 2,000
 * Aspect-ratio-3x2.svg
 * 6,016,000
 * 6
 * Nikon D40, D50, D70, D70s, Pentax K100D, Konica Minolta Maxxum 7D, Konica Minolta Maxxum 5D
 * 3,072
 * 2,048
 * Aspect-ratio-3x2.svg
 * 6,291,456
 * 6.3
 * Canon EOS 10D, Canon EOS 300D
 * 3,072
 * 2,304
 * Aspect-ratio-4x3.svg
 * 7,077,888
 * 7
 * Olympus FE-210, Canon PowerShot A620
 * 3,456
 * 2,304
 * Aspect-ratio-3x2.svg
 * 7,962,624
 * 8
 * Canon EOS 350D
 * 3,264
 * 2,448
 * Aspect-ratio-4x3.svg
 * 7,990,272
 * 8
 * Olympus E-500, Olympus SP-350, Canon PowerShot A720 IS, Nokia 701, HTC Desire HD, Apple iPhone 4S
 * 3,504
 * 2,336
 * Aspect-ratio-3x2.svg
 * 8,185,344
 * 8.2
 * Canon EOS 30D, Canon EOS-1D Mark II, Canon EOS-1D Mark II N
 * 3,520
 * 2,344
 * Aspect-ratio-3x2.svg
 * 8,250,880
 * 8.25
 * Canon EOS 20D
 * 3,648
 * 2,736
 * Aspect-ratio-4x3.svg
 * 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
 * Aspect-ratio-3x2.svg
 * 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
 * Aspect-ratio-3x2.svg
 * 10,077,696
 * 10.1
 * Canon EOS 40D, Canon EOS 400D, Canon EOS 1000D
 * 4,064
 * 2,704
 * Aspect-ratio-3x2.svg
 * 10,989,056
 * 11
 * Canon EOS-1Ds
 * 4,000
 * 3,000
 * Aspect-ratio-4x3.svg
 * 12,000,000
 * 12
 * Canon Powershot G9, Fujifilm FinePix S200EXR, Nikon Coolpix L110, Kodak Easyshare Max Z990
 * 4,256
 * 2,832
 * Aspect-ratio-3x2.svg
 * 12,052,992
 * 12.1
 * Nikon D3, Nikon D3S, Nikon D700, Fujifilm FinePix S5 Pro
 * 4,272
 * 2,848
 * Aspect-ratio-3x2.svg
 * 12,166,656
 * 12.2
 * Canon EOS 450D
 * 4,032
 * 3,024
 * Aspect-ratio-4x3.svg
 * 12,192,768
 * 12.2
 * Olympus PEN E-P1
 * 4,288
 * 2,848
 * Aspect-ratio-3x2.svg
 * 12,212,224
 * 12.2
 * Nikon D2Xs/D2X, Nikon D300, Nikon D300S, Nikon D90, Nikon D5000, Pentax K-x
 * 4,900
 * 2,580
 * Aspect-ratio-16x9.svg
 * 12,642,000
 * 12.6
 * RED ONE Mysterium
 * 4,368
 * 2,912
 * Aspect-ratio-3x2.svg
 * 12,719,616
 * 12.7
 * Canon EOS 5D
 * 5,120
 * 2,700
 * Aspect-ratio-16x9.svg
 * 13,824,000
 * 13.8
 * RED Mysterium-X
 * 7,920 (2,640 &times; 3)
 * 1,760
 * Aspect-ratio-3x2.svg
 * 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
 * Aspect-ratio-3x2.svg
 * 14,501,888
 * 14.5
 * Pentax K20D, Pentax K-7
 * 4,752
 * 3,168
 * Aspect-ratio-3x2.svg
 * 15,054,336
 * 15.1
 * Canon EOS 50D, Canon EOS 500D, Sigma SD1
 * 4,928
 * 3,262
 * Aspect-ratio-3x2.svg
 * 16,075,136
 * 16.1
 * Nikon D7000, Nikon D5100, Pentax K-5
 * 4,992
 * 3,328
 * Aspect-ratio-3x2.svg
 * 16,613,376
 * 16.6
 * Canon EOS-1Ds Mark II, Canon EOS-1D Mark IV
 * 5,184
 * 3,456
 * Aspect-ratio-3x2.svg
 * 17,915,904
 * 17.9
 * Canon EOS 7D, Canon EOS 60D, Canon EOS 600D, Canon EOS 550D
 * 5,270
 * 3,516
 * Aspect-ratio-3x2.svg
 * 18,529,320
 * 18.5
 * Leica M9
 * 5,616
 * 3,744
 * Aspect-ratio-3x2.svg
 * 21,026,304
 * 21.0
 * Canon EOS-1Ds Mark III, Canon EOS-5D Mark II
 * 6,048
 * 4,032
 * Aspect-ratio-3x2.svg
 * 24,385,536
 * 24.4
 * Sony α 850, Sony α 900, Sony Alpha 99, Nikon D3X and Nikon D600
 * 7,360
 * 4,912
 * Aspect-ratio-3x2.svg
 * 36,152,320
 * 36.2
 * Nikon D800
 * 7,500
 * 5,000
 * Aspect-ratio-3x2.svg
 * 37,500,000
 * 37.5
 * Leica S2
 * 7,212
 * 5,142
 * Aspect-ratio-4x3.svg
 * 39,031,344
 * 39.0
 * Hasselblad H3DII-39
 * 7,216
 * 5,412
 * Aspect-ratio-4x3.svg
 * 39,052,992
 * 39.1
 * Leica RCD100
 * 7,264
 * 5,440
 * Aspect-ratio-4x3.svg
 * 39,516,160
 * 39.5
 * Pentax 645D
 * 7,320
 * 5,484
 * Aspect-ratio-4x3.svg
 * 40,142,880
 * 40.1
 * Phase One IQ140
 * 7,728
 * 5,368
 * ~ 10:7
 * 41,483,904
 * 41.5
 * Nokia 808 PureView
 * 8,176
 * 6,132
 * Aspect-ratio-4x3.svg
 * 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
 * Aspect-ratio-4x3.svg
 * 60,076,848
 * 60.1
 * Hasselblad H4D-60
 * 8,984
 * 6,732
 * Aspect-ratio-4x3.svg
 * 60,480,288
 * 60.5
 * Phase One IQ160, Phase One P65+
 * 10,320
 * 7,752
 * Aspect-ratio-4x3.svg
 * 80,000,640
 * 80
 * Leaf Aptus-II 12, Leaf Aptus-II 12R
 * 10,328
 * 7,760
 * Aspect-ratio-4x3.svg
 * 80,145,280
 * 80.1
 * Phase One IQ180
 * 9,372
 * 9,372
 * 1:1
 * 87,834,384
 * 87.8
 * Leica RC30 (point scanner)
 * 12,600
 * 10,500
 * 6:5
 * 132,300,000
 * 132.3
 * Phase One PowerPhase FX/FX+ (line scanner)
 * 18,000
 * 8,000
 * 9:4
 * 144,000,000
 * 144
 * Better Light 6000-HS/6000E-HS (line scanner)
 * 21,250
 * 7,500
 * 17:6
 * 159,375,000
 * 159.4
 * Seitz 6x17 Digital (line scanner)
 * 16,352*
 * 12,264*
 * Aspect-ratio-4x3.svg
 * 200,540,928
 * 200.5
 * Hasselblad H4D-200MS (*actuated multi (6x) shot)
 * 18,000
 * 12,000
 * Aspect-ratio-4x3.svg
 * 216,000,000
 * 216
 * Better Light Super 6K-HS (line scanner)
 * 24,000
 * 15,990
 * ~ Aspect-ratio-3x2.svg
 * 383,760,000
 * 383.8
 * Better Light Super 8K-HS (line scanner)
 * 30,600
 * 13,600
 * 9:4
 * 416,160,000
 * 416.2
 * Better Light Super 10K-HS (line scanner)
 * 62,830
 * 7,500
 * ~ 25:3
 * 471,225,000
 * 471.2
 * Seitz Roundshot D3 (80 mm lens) (scanned)
 * 62,830
 * 13,500
 * ~ 5:1
 * 848,205,000
 * 848.2
 * Seitz Roundshot D3 (110 mm lens) (line scanner)
 * 38,000
 * 38,000
 * 1:1
 * 1,444,000,000
 * 1,444
 * Pan-STARRS PS1
 * 157,000
 * 18,000
 * ~ 26:3
 * 2,826,000,000
 * 2,826
 * Better Light 300 mm lens Digital (line scanner)
 * }
 * 144,000,000
 * 144
 * Better Light 6000-HS/6000E-HS (line scanner)
 * 21,250
 * 7,500
 * 17:6
 * 159,375,000
 * 159.4
 * Seitz 6x17 Digital (line scanner)
 * 16,352*
 * 12,264*
 * Aspect-ratio-4x3.svg
 * 200,540,928
 * 200.5
 * Hasselblad H4D-200MS (*actuated multi (6x) shot)
 * 18,000
 * 12,000
 * Aspect-ratio-4x3.svg
 * 216,000,000
 * 216
 * Better Light Super 6K-HS (line scanner)
 * 24,000
 * 15,990
 * ~ Aspect-ratio-3x2.svg
 * 383,760,000
 * 383.8
 * Better Light Super 8K-HS (line scanner)
 * 30,600
 * 13,600
 * 9:4
 * 416,160,000
 * 416.2
 * Better Light Super 10K-HS (line scanner)
 * 62,830
 * 7,500
 * ~ 25:3
 * 471,225,000
 * 471.2
 * Seitz Roundshot D3 (80 mm lens) (scanned)
 * 62,830
 * 13,500
 * ~ 5:1
 * 848,205,000
 * 848.2
 * Seitz Roundshot D3 (110 mm lens) (line scanner)
 * 38,000
 * 38,000
 * 1:1
 * 1,444,000,000
 * 1,444
 * Pan-STARRS PS1
 * 157,000
 * 18,000
 * ~ 26:3
 * 2,826,000,000
 * 2,826
 * Better Light 300 mm lens Digital (line scanner)
 * }
 * Pan-STARRS PS1
 * 157,000
 * 18,000
 * ~ 26:3
 * 2,826,000,000
 * 2,826
 * Better Light 300 mm lens Digital (line scanner)
 * }
 * }
 * }

Companies
The largest companies that manufacture imaging sensors include the following:
 * Agilent
 * Aptina ( formerly division of Micron Technology)
 * Canesta
 * Canon
 * Dalsa
 * Eastman Kodak
 * ESS Technology
 * Fujifilm
 * MagnaChip
 * Matsushita
 * MAZeT GmbH
 * Mitsubishi
 * Nikon
 * OmniVision Technologies
 * On Semiconductor ( formerly Cypress Semiconductor )
 * PixArt Imaging
 * Pixim
 * Samsung
 * Sharp
 * Sony
 * STMicroelectronics
 * Toshiba
 * TowerJazz
 * TransChip
 * Trusight
 * Trusense imaging

Origin
The contents of this page were copied from the Wikipedia article Image_sensor on 8 January 2013.