Image sensor



An image sensor is a device that converts a visual image to an electric signal. It is used mostly used in digital cameras and other imaging devices. It is a set 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 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]

Performance

There are a 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 a detailed guide to digital sensor performance, see Roger Clark's article.

Specialty sensors

Special sensors are used for various applications. The most important are the sensors for x-rays, IR Rays Infrared Rays and other highly sensitive arrays for astronomy.

See also

References

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

Leading Suppliers of Image Sensors

  • OmniVision Technologies, Inc.
  • Panavision SVI
  • TOSHIBA Semiconductor Company - Click "Products/Imaging Solutions"
  • STMicroelectronics Imaging Division
  • Micron Technology, IncCMOS Image Sensors
  • Galaxy Core, Inc CMOS Image Sensors
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Image_sensor". A list of authors is available in Wikipedia.