What is a Digital Image Sensor?

When you click on camera shutter button,
the exposure process starts

A digital sensor contains an array of literally millions of miniature pixels to be able to create a single photographic image. When you click on the button for the camera, the exposure process starts, each of these tiny pixels contain a "photosite" that is revealed to collect and stockpile photons in a hollow space. Once the exposure is completed, the camera shuts every one of these photosites, then trys to determine how many photons dropped into each. The comparative phototon quantity in each hollow space is then arranged into various levels of intensity, whose precision is ascertained by bit depth from (0 - 255 in an 8-bit photo). ✓

CCD Sensor
CCD A image sensor on a flexible circuit board


Currently, most all still digital cameras contain either a CCD sensor or CMOS image sensor. Either type accomplish the same results of acquiring light and changing it into electronic signals. A CCD sensor is an analog mechanism. As light enters the chip it becomes seized as a tiny electrical charge in every photo sensor. These charges are then converted to voltage a single pixel after another while they are being read from the image chip. Other circuitry inside the camera changes this voltage into digital data.

A CMOS image chip is a style of active pixel sensor created using a CMOS semiconductor process. Additional circuitry adjoining each photo sensor changes light energy to voltage. Added chip circuitry might also be included to change this voltage to digital records. Neither chip technology features a definite image quality advantage over the other. CMOS has the possibility to be put into operation with fewer components, consume less power and allow faster readout than a CCD. CCD is a somewhat more established technology while in the majority of respects equal to CMOS chips.

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There are a great number of considerations that can be employed to evaluate an image sensors performance, which might include its dynamic range, ratio of signal-to-noise, sensitivity to low-light, etc. Looking at sensors of equivalent types, the ratio of signal-to-noise and dynamic range both get better as the size enlarges

Color Sensors

There are a number of basic kinds of color sensors, unique by their color separation devices:
The Bayer sensor, is low-cost and therefore the most common, employing a color filter array like a Bayer filter which moves green, red, or blue Illumination to chosen sensels, or pixels, shaping interlaced grids which are sensitive to green, red, and blue. Then this image is interpolated employing a demosaicing algorithm. The Foveon X3 sensor sensor, employees an array of sensors in layers where each pixel encompasses three sensors that are stacked and sensitive to individual colors. 3CCD, employs three discrete image sensors, with color separation created by using a dichroic prism. deemed the better quality, and most often more costly than single-CCD image sensors.

Specialty Sensors

Special image sensors are often used for a variety of applications like thermal imaging, creatiing of multi-spectral images, gamma type cameras, sensor arrays in x-rays, plus extremely sensitive arrays for use in astronomy
 updated article Jan 24, 2012

See also

  • Video camera tube
  • Semiconductor detector
  • Contact image sensor
  • Image sensor format, the sizes and shapes of common image sensors
  • Sensitometry, the scientific study of light-sensitive materials

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