Authored by Michael Anissimov and can also be found here: http://is.gd/I2Q7Dp
Instead of exposing a photosensitive chemical known as film to a scene to create an imprinted image, most digital cameras use a charge-coupled device (CCD), an electronics instrument that creates a pixel map based on the electric charge generated when photons slam into a sensitive material. This phenomenon is called the photoelectric effect, and was elucidated by Albert Einstein in a famous 1905 paper. Less frequently used than a CCD is a complementary-metal-oxide-semiconductor (CMOS). Because it is the digital camera mechanism in the minority, the CMOS will not be discussed in this article.
The term CCD-based camera is sometimes used interchangeably with digital camera, because by its very nature the CCD-based camera takes digital camera pictures – pictures with a certain pixel-by-pixel resolution that can be encoded digitally. Nowadays, we can transfer these files from a digital camera to many devices, including computers, screens, phones, and printers.
A charge-coupled device is an integrated circuit, meaning it uses multiple semiconductor elements on a unified platform to achieve its goals. The active components of the charge-coupled device in a digital camera or other CCD-based camera are the capacitors. These are linked in a circuit, hence the term charge-coupled. A capacitor is a basic electronics device that stores a potential difference, or voltage, in the variance between two plates with equal but opposite electrical charges.
A lens projects the image onto the CCDs. Each capacitor acquires a charge proportional to the brightness of incoming light. CCDs are not inherently color-sensitive, and to take color photos, a Bayer mask must be employed to selectively filter light into designated pixels based on color. Upon acquiring the charge, the capacitors begin passing their charge to adjacent capacitors in a charge-coupled, daisy-chain fashion. A register at the end of a capacitor array makes the appropriate measurements, and a 2D pixel map is created.
Because their sensitivity to light is about 35 times that of a conventional camera, approaching the quantum limit, the digital camera is favored by event photographers and astrophotographers alike. Because of the lack of active chemical components, images on a digitalcamera do not need to be “developed” and are stored directly in the camera shortly after exposure.
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