An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras 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.
Contents |
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]
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.
There are several main types of color image sensors, differing by the type of color-separation mechanism:
| Width | Height | Aspect ratio | Actual pixel count | Megapixels | Camera examples |
|---|---|---|---|---|---|
| 320 | 240 | 76,800 | 0.07 | 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) | |
| 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 | |
| 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 | Olympus E-410, Olympus E-510, Panasonic FZ50, Fujifilm FinePix HS10 | |
| 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 | |
| 7,500 | 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 | |
| 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) |
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.
The largest companies that manufacture imaging sensors include the following: