Automatic focus for image sensors

Abstract

The embodiments of the invention relate to automatic focusing methods and apparatus suitable for use in digital imaging devices. The proposed methods and apparatus evaluate the focus condition of the optical system by evaluating the digitized image, without requiring additional hardware besides the digital image-capture signal flow path. A method for computing the appropriate direction and magnitude of optical system adjustment, based on the evaluated focus condition, is provided. The computed quantities are communicated to the lens driving apparatus to reposition and adjust the optical system and to incrementally obtain a better focus. Upon reaching a desired focus quality, the device is prevented from controlling the lens driving apparatus.

Description

technical field

[0001] The present invention relates to digital imaging, and more particularly, the present invention relates to a mechanism and method for autofocus of a digital imaging device. Background technique

[0002] Generally, digital imaging devices can be divided into two types: auto-focus and fixed-focus. A fixed focus setup typically cannot adjust the lens or change the aperture, instead relying on a large depth of field where the object of interest appears in focus. Although fixed-focus devices can be used in many situations, the images they capture are not as sharp as those captured by auto-focus devices.

[0003] The image captured at the focal point of the lens is in sharp focus, where focus is defined as the actual or virtual point of convergence of the rays on the axis of the camera lens. However, as long as the subject is within the depth of field of the lens, a fairly sharp image can be produced. Depth of field is the range of distance from the camera...

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