1. A system, comprising: an input to receive images from an imager, said images including a first image generated by reflecting light off an object, said first image comprising a pattern of pixels with a first pixel of interest, a selected pixel, and a second pixel located in the pattern; and and a processor, coupled to said input, the processor used to determine a contrast value and then identify an artifact in said first image based on the contrast value, the contrast value being determined by obtaining a first result which is determined by subtracting a pixel value of the first pixel of interest from a pixel value of the selected pixel, and then dividing the first result by a divisor term to obtain a second result, and then subtracting a pixel value of the second pixel from the second result.