US Patent 7874674 Aberrometer having reduced noise

Methods and apparatus for facilitating determination of centroids of image spots in an image containing an array of image spots generated by an aberrometer, the image comprising a first plurality of pixels each pixel having a corresponding intensity value, the method comprising calculating an average intensity value for a second plurality of pixels in a perimeter around a pixel, the average calculated using a subset of the second plurality exclusive of at least a portion of the pixels in the perimeter.