How passive autofocus works with camera's microprocessor and lens
How passive autofocus works with camera's microprocessor and lens | ||
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Light passing through the lens of a camera is diverted from the image sensor at the back of the camera by a mirror, or prism. The light falls on a strip of 100–200 photocells, called linear sensors, which are similar to those that make up the imaging sensor. The strip is positioned so that the distance the light travels to it is equal to the distance to the imaging sensor. The camera's processor compares the intensity of the light falling on each photocell to the intensities of the adjacent cells. If the image is out of focus, adjacent pixels have similar intensities; there is little contrast among them. The microprocessor moves the lens and again compares the photocell intensities. As the scene comes more into focus, the contrast between adjacent photodiodes increases. When the microprocessor gauges that the difference in intensity is at its maximum, the scene is in focus. | ||