Automatic focus for image sensors
First Claim
1. An automatic focusing apparatus as a part of a digital imaging device, the apparatus comprising:
- an optical system capable of forming an image of an object at a focal plane of the optical system;
a two dimensional array of light sensors for generating pixel data representing the image;
a windowing facility for;
extracting the pixel data of at least one region of the image;
computing at least one value corresponding to a focus condition of the region based on the region'"'"'s extracted pixel data; and
computing at least one value corresponding to a scene activity of the region based on the region'"'"'s extracted pixel data;
a focus condition change detection facility for computing an out-of-focus indicator value based on the scene activity value; and
a tracking state-machine for computing a direction value and a magnitude value for adjusting and repositioning the optical system from a current position, based on the computed focus condition value and the out-of-focus indicator value.
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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.
23 Citations
20 Claims
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1. An automatic focusing apparatus as a part of a digital imaging device, the apparatus comprising:
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an optical system capable of forming an image of an object at a focal plane of the optical system;
a two dimensional array of light sensors for generating pixel data representing the image;
a windowing facility for;
extracting the pixel data of at least one region of the image;
computing at least one value corresponding to a focus condition of the region based on the region'"'"'s extracted pixel data; and
computing at least one value corresponding to a scene activity of the region based on the region'"'"'s extracted pixel data;
a focus condition change detection facility for computing an out-of-focus indicator value based on the scene activity value; and
a tracking state-machine for computing a direction value and a magnitude value for adjusting and repositioning the optical system from a current position, based on the computed focus condition value and the out-of-focus indicator value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An automatic focusing method for a digital image capturing device, the method comprising:
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generating pixel data representing an image, employing a two dimensional array of light sensors located substantially at a focal plane of an optical system;
extracting the pixel data of at least one region of the image;
computing at least one value corresponding to focus condition of the at least one region based on its extracted pixel data;
computing at least one value corresponding to a scene activity of the at least one region based on its extracted pixel data;
computing an out-of-focus indicator value based on the scene activity value; and
computing a direction and a magnitude value for adjusting and repositioning the optical system from a current position, based on the computed focus condition value and the out-of-focus indicator value. - View Dependent Claims (17, 18, 19)
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20. An automatic focusing means in a digital imaging device, comprising:
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a means for generating pixel data representing an image;
a means for extracting the pixel data of at least one region of the image, wherein the extracted pixel data is from green component or luminance component of the image;
a means for computing at least one value corresponding to focus condition of the at least one region based on the extracted pixel data;
a means for computing at least one value corresponding to the image statistics of the at least one region based on its extracted pixel data;
a means for computing an out-of-focus indicator value based on the image statistics value; and
a means for computing a direction and a magnitude value for adjusting the optical system, based on the computed focus condition value and the out-of-focus indicator value.
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Specification