A method for object detection that utilizes a patterned background. Patterned backgrounds are chosen such that each reference image analyzed will have both light and dark pixels. The method calculates the difference between the expected value for the light pixels and the expected value of the dark pixels in the reference image. This difference is used to chose a threshold value. The difference in expected values for the corresponding pixels in a live image is calculated and compared to the threshold value. If the difference in expected values of the live image are less than the threshold value, object detection is indicated.