Method and apparatus for online contact lens evaluation

1. A computer-implemented method for use with an aberrometer/wavefront sensor system for determining pupil parameters, comprising the steps of:

a) obtaining a pupil image;

b) compressing the pupil image by a selected amount, n, and compressing the pupil image by a different selected amount, n 1 <n, where n 1 <10;

c) calculating a threshold value for the compressed pupil image;

d) determining a center parameter value of the pupil;

e) determining a multiple-coordinate axes diameter parameters of the pupil;

f) determining a perimeter shape of the pupil based upon the center and multiple-coordinate axes parameters;

g) plotting the shape into the compressed image and determine average pixel signal values inside of the perimeter;

h) enlarging the perimeter by a selected amount, Δ, and repeat steps (c, d) on a new image with the enlarged perimeter;

i) determining a fringe point position at each end of each of the diameter coordinate axes, and fitting a perimeter shape to the points;

j) repeating step (d) on an image obtained from step (i);

k) repeating step (g) on the n 1 compressed pupil image;

l) repeating step (h) on the step (k) image, with a Δ 1 <Δ;

m) repeating steps (d, e) on the step (l) image;

n) making an eyelid-correction on the step (m) image; and

o) repeating steps (d, e) on the step (n) image.

2. The method of claim 1 , where n is an integer, and 1≦n<20.

3. The method of claim 1 , wherein step (c) comprises creating a binary image by setting all pixel values below the threshold to a zero value and all pixel values above the threshold to a high value.

4. The method of claim 3 , wherein a center of mass is determined for the zero value pixels as well as a standard deviation, which is used to determine diameter values along an x-coordinate axis and a y-coordinate axis.

5. The method of claim 4 , wherein the perimeter shape is an ellipse.

6. The method of claim 5 , wherein Δ is in a range between about 5% to 25%, and Δ 1 is in a range between about 5% to 25%.

7. The method of claim 6 , wherein step (i) comprises fitting an ellipse to fringe points at each end of the x-coordinate axis and a y-coordinate axis.

8. The method of claim 7 , wherein step (n) comprises scanning every pixel column that contains a found ellipse perimeter, and computing a difference function between the ellipse perimeter and the pupil fringe as a function of X-position.

9. The method of claim 8 , comprising determining at least two maxima and a minimum in between said maxima of the difference function and, based upon satisfying a selected error-criteria, locating an arc of the found ellipse between the X-positions of the two maxima.

10. The method of claim 9 , comprising determining the pupil center parameter and the pupil size parameter.