Image Sensor

Information about Image Sensor

A dismantled USB webcam, with and without a lens over its (Bayer format) image sensor.

An image sensor is a device that converts a visual image to an electric signal. It is used chiefly in digital cameras and other imaging devices. It is usually an array of charge-coupled devices (CCD) or CMOS sensors such as active-pixel sensors.

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

Bayer sensor, low-cost and most common, using a Bayer filter that passes red, green, or blue light to selected pixels, forming interlaced grids sensitive to red, green, and blue. The image is then interpolated using a demosaicing algorithm.
Foveon X3 sensor, using an array of layered sensors where every pixel contains three stacked sensors sensitive to the individual colors.
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.

CCD Vs CMOS

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

A CCD 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 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 converts the voltage to digital data.

Neither technology has a clear advantage in image quality. CMOS can potentially be implemented with fewer components, use less power and provide data faster than CCDs. CCD is a more mature technology and is in most respects the equal of CMOS.^[1] ^[2]

Specialty sensors

Special sensors are used for various applications. The most important are the sensors for thermal imaging, creation of multi-spectral images, gamma cameras, sensor arrays for x-rays, and highly sensitive arrays for astronomy.

References

1. ^ [1] CCD Vs CMOS from Photonics Spectra 2001
2. ^ [2] Sensors By Vincent Bockaert

Leading Suppliers of Image Sensors

digital camera is an electronic device used to capture and store photographs digitally, instead of using photographic film like conventional cameras, or recording images in an analog format to magnetic tape like many video cameras.
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charge-coupled device (CCD) is an analog shift register, enabling analog signals (electric charges) to be transported through successive stages (capacitors) controlled by a clock signal.
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Complementary metal–oxide–semiconductor (CMOS) ("see-moss", IPA: /ˈsiːmɒs/), is a major class of integrated circuits.
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An active-pixel sensor (APS), also commonly written active pixel sensor, is an image sensor consisting of an integrated circuit containing an array of pixel sensors, each containing a photodetector and connecting to an active transistor reset and readout circuit.
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A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. The term derives from the name of its inventor, Dr. Bryce E.
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A demosaicing algorithm is a digital image process used to interpolate a complete image from the partial raw data received from the color-filtered image sensor (via a color filter array or CFA) internal to many digital cameras in form of a matrix of colored pixels.
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The Foveon X3 sensor is a CMOS^[1] image sensor for digital cameras, designed by Foveon, Inc. and manufactured by National Semiconductor^[2] and Dongbu Electronics.
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A dichroic prism is a prism that splits light into two beams of differing wavelength (colour). They are usually constructed of one or more glass prisms with dichroic optical coatings that selectively reflect or transmit light depending on the light's wavelength.
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Complementary metal–oxide–semiconductor (CMOS) ("see-moss", IPA: /ˈsiːmɒs/), is a major class of integrated circuits.
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Thermography, thermal imaging, or thermal video, is a type of infrared imaging. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9–14 µm) and produce images of that radiation.
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Multi-spectral imaging is a technology originally developed for space-based imaging. Multi-spectral imaging can capture light from frequencies beyond the visible light range, such as infrared.
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A gamma camera is a device used in nuclear medical imaging also known as nuclear medicine, to view and analyse images of the human body of the distribution of medically injected, inhaled, or ingested gamma ray emitting radionuclides.
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X-rays (or Röntgen rays) are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. X-rays are primarily used for diagnostic radiography and crystallography.
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Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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In older video cameras, before the 1990s, a video camera tube or pickup tube was used instead of a charge-coupled device (CCD). Several types were in use from the 1930s to the 1980s. These tubes are a type of cathode ray tube.
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A semiconductor detector is a device that uses a semiconductor (usually silicon or germanium) to detect traversing charged particles or the absorption of photons. In the field of particle physics, these detectors are usually known as silicon detectors.
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Contact Image Sensors (CIS) are a relatively recent technological innovation in the field of optical flatbed scanners that are rapidly replacing CCDs in low power and portable applications.
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