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Image capturing apparatus, method, and program for performing an auto focus operation using invisible and visible light

  • US 8,537,264 B2
  • Filed: 04/28/2008
  • Issued: 09/17/2013
  • Est. Priority Date: 05/01/2007
  • Status: Active Grant
First Claim
Patent Images

1. An image capturing apparatus comprising:

  • image pickup means including an image pickup element configured to capture, in a unit of pixels, a plurality of colors in ranges of visible and invisible light incoming through an image capturing lens;

    pixel value calculating means configured to calculate a pixel value of each pixel regarding at least one of the colors captured by the image pickup means;

    contrast value calculating means configured to calculate a contrast value for each of the at least one color on the basis of the pixel values calculated by the pixel value calculating means;

    contrast value storage memory means configured to store a plurality of contrast values;

    focus correction value calculating means configured to determine whether the contrast values have a relative maximum value and calculate a focus correction value for a distance from a current position of the image capturing lens to a focus position of the image capturing lens on the basis of a temporal change in the contrast values of the at least one color calculated by the contrast value calculating means; and

    image capturing lens driving means configured to drive the image capturing lens on the basis of the focus correction value calculated by the focus correction value calculating means;

    wherein the pixel value calculating means calculates, for each pixel, a luminance value, including the visible light and the invisible light, as a pixel value;

    wherein the contrast value calculating means calculates the contrast value by applying a high-pass filter to the luminance value of each pixel calculated by the pixel value calculating means;

    wherein when the focus correction value calculating means determines that the contrast values do not have a relative maximum value, the focus correction value calculating means calculates the focus correction value for the distance from the current position of the image capturing lens to the focus position of the image capturing lens on the basis of the temporal change in the contrast values calculated by the contrast value calculating means;

    wherein the focus correction value calculating means determines whether the contrast values have a relative maximum value on the basis of a contrast value calculated for incoming colors at a current time, a plurality of contrast values calculated for incoming colors before the current time and stored in the contrast value storage memory means, and a corresponding position of the image capturing lens;

    wherein at least three contrast values are needed for the contrast values to have a relative maximum value; and

    wherein when two or more contrast values exist and the focus correction value calculating means determines that the contrast values do not have a relative maximum value, the focus calculating means sets, as the focus correction value, a distance between the current position of the image capturing lens and a position away from the current position of the image capturing lens corresponding to a maximum value of the plurality of the contrast values calculated before the current time by a predetermined distance in a direction from the current position of image capturing lens toward the position corresponding to the maximum value.

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