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The Camera Image Sensors

Last Updated 14th July 2012

There are two kinds of digital image sensors generally used: a charge-coupled device (CCD) and a complementary metal oxide semiconductor (CMOS).

Figure on left basically shows the method of digitising the image or photo. Figure on right are examples of Digital Image Sensors found on Digital Cameras.

Bayer Pattern. A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photo-sensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called RGBG, GRGB, or RGGB. It is named after its inventor, Bryce E. Bayer of Eastman Kodak.

Charged-Coupled Device – CCD

CCD sensors were initially developed for video cameras. CCD sensors record the image pixel by pixel and row by row. The voltage information from each element in the row is passed on prior to descending to the next row and only one row is active at a time. It does not convert the voltage information into digital but to accomplish the feat, another circuitry is added to the camera to digitise the voltage information prior to transferring the data to the storage medium like SD Cards.

Complementary Metal Oxide Semiconductor – CMOS

CMOS sensors are capable of recording the entire image provided by the light-sensitive elements in parallel all at once, resulting in a higher rate of data transfer to the storage medium. Additional circuitry is added to each individual element to convert the voltage information to digital data. A small coloured micro lens is fixed on each element to increase its ability to read the colour of light. Advances have been made in recent years in the sensitivity and speed of CMOS sensors, making them the most common type of digital image sensor found in most Digital Cameras.

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