shutter button and lens are virtually the only parts of the camera that remain in digital cameras.
The film has been replaced with a light sensitive chip, called a Charge Coupled Device (CCD). This chip is an array of millions elements that are sensitive to light. When light hits an element in the CCD array, a electrical charge is accumulated at a rate determined by the amount of light striking it. This charge is then measured by an analog to digital converter that converts the voltage to a digital value that can be stored in memory. The raw image derived from the CCD is too big to store. The camera contains a specialized chip know as the compression engine, which takes the raw image and compresses it to a size that can be stored on the memory card. This compression reduces the overall storage requirement by a factor of 3 to 16.
This is a block diagram of a camera from the Texas Instrument web site (www.ti.com). They want designers to use their integrated circuits, so they supply much of the design for the camera.
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