Fast focus assessment system and method for imaging

Claim 3

The method according to claim 1 , wherein said step of determining said focus score comprises the step of nonlinearly compressing said summation.

Claim 4

The method according to claim 2 , wherein said step of nonlinearly compressing said summation is of the form f(x)=100 x 2 /(x 2 +c 2 ), thereby generating said focus score in a range between 0 and 100.

Claim 5

The method according to claim 1 , wherein said predetermined ratio is −3:1, said first sum:said second sum.

Claim 6

The method according to claim 1 , further comprising the step of comparing said focus score to a predetermined threshold to assess said focus to determine a focus assessment.

Claim 7

The method according to claim 5 , wherein if said focus score is not less than said predetermined threshold, then said focus assessment is determined to be acceptable, and if said focus score is less than said predetermined threshold, then said focus assessment is determined to be unacceptable.

Claim 8

The method according to claim 6 , further comprising the step of activating an indicator responsive to said focus assessment.

Claim 9

A iris imaging apparatus for obtaining an image of an iris of an eye and for assessing the focus quality of the image, comprising: a camera having a front surface and captures the image; a lens having a image plane disposed in front of said front surface of said camera; a mirror disposed on a side of said lens opposite said camera; an illuminator disposed along a side of said mirror; and a focus assessment processor coupled to said camera, said focus assessment processor comprising a microprocessor for convolving the image with a convolution kernel into a convolved image by (a) isolating one portion of a plurality of portions of said image; (b) summing a central group of pixels of said portion to obtain a first sum; (c) summing a plurality of outer pairs of rows and columns outside said central group of pixels to obtain a second sum; (d) combining said first sum and said second sum in a predetermined ratio; and (e) squaring the convolution result; for determining a spectral energy of said convolved image by repeating steps (a)-(e) for further portions of said plurality of portions of said image and accumulating each said convolution result to generate a summation representative of said spectral energy; and for determining a focus score responsive to said spectral energy, said focus score being indicative of the focus quality of the image.

Claim 10

A iris imaging apparatus for obtaining an image of an iris of an eye and for assessing the focus quality of the image, comprising: a camera having a front surface and captures the image; a lens having a image plane disposed in front of said front surface of said camera; a mirror disposed on a side of said lens opposite said camera; an illuminator disposed along a side of said mirror; and a focus assessment processor coupled to said camera, said focus assessment processor comprising a microprocessor for convolving the image with a convolution kernel into a convolved image by (a) isolating one portion of a plurality of portions of said image; (b) summing a central group of pixels of said portion to obtain a first sum; (c) summing a plurality of outer pairs of rows and columns outside said central group of pixels to obtain a second sum; (d) combining said first sum and said second sum in a predetermined ratio; and (e) squaring the convolution result; for determining a spectral energy of said convolved image by repeating steps (a)-(e) for further portions of said plurality of portions of said image and accumulating each said convolution result to generate a summation representative of said spectral energy; and for determining a focus score responsive to said spectral energy, said focus score being indicative of the focus quality of the image.

Claim 11

The apparatus according to claim 8 , further comprising an analog to digital converter and a frame buffer disposed between said camera and said focus assessment processor.

Claim 12

The apparatus according to claim 8 , further comprising at least one of a visible indicator and an audible indicator, said focus assessment processor coupled to said at least one of a visible indicator and an audible indicator.

Claim 13

The apparatus according to claim 8 , wherein said microprocessor comprises means for nonlinearly compressing said summation.

Claim 14

The apparatus according to claim 11 , wherein said means for nonlinearly compressing said summation is of the form f(x)=100 x 2 /(x 2 +c 2 ), thereby generating said focus score in a range between 0 and 100.

Claim 15

The apparatus according to claim 8 , wherein said predetermined ratio is −3:1, said first sum:said second sum.

Claim 16

The apparatus according to claim 8 , further comprising means for comparing said focus score to a predetermined threshold to assess said focus to determine the focus quality.

Claim 17

The apparatus according to claim 14 , wherein if said focus score is not less than said predetermined threshold, then the focus quality is determined to be acceptable, and if said focus score is less than said predetermined threshold, then the focus quality is determined to be unacceptable.

Claim 18

The apparatus according to claim 15 , further comprising: at least one of a visible indicator and an audible indicator, said focus assessment processor coupled to said at least one of a visible indicator and an audible indicator; and means for activating said at least one of a visible indicator and an audible indicator responsive to the focus quality.

Claim 21

The system according to claim 17 , wherein said means for determining said focus score comprises means for nonlinearly compressing said summation.

Claim 22

The system according to claim 18 , wherein said means for nonlinearly compressing said summation is of the form f(x)=100 x 2 /(x 2 +c 2 ), thereby generating said focus score in a range between 0 and 100.

Claim 23

The system according to claim 17 , wherein said predetermined ratio is −3:1, said first sum:said second sum.

Claim 24

The system according to claim 17 , further comprising means for comparing said focus score to a predetermined threshold to assess said focus to determine the focus quality.

Claim 25

The system according to claim 21 , wherein if said focus score is not less than said predetermined threshold, then the focus quality is determined to be acceptable, and if said focus score is less than said predetermined threshold, then the focus quality is determined to be unacceptable.

Claim 26

The system according to claim 22 , further comprising: at least one of a visible indicator and an audible indicator, and means for activating said at least one of a visible indicator and an audible indicator responsive to the focus quality.