Centroid Calculation Algorithm Using Weight Table to Increase Accuracy of Center Position Detection

Abstract

In this paper, a new algorithm that measures the centroid position of a spot in the image obtained from an image sensor with sub-pixel accuracy was presented. The lens forms a spot on the image sensor, which spreads over a few pixels on the image. The algorithm is used to carry out centroid calculation using the brightness values of the spread pixels, and it increases the accuracy of the center detection of the spot image. In the calculation, a weight table is used, which has a circular form with a blurred border. The weight value is multiplied by the corresponding brightness value, which further increases the accuracy. An image containing a spot and random noise is produced in the simulation. Centroid calculation is carried out using the produced image, and the accuracy of the centroid position is evaluated. It is confirmed that the presented algorithm can detect the centroid position with an accuracy of 0.02 = 1/50 pixel when the spot is defocused. It is 1.5 times more accurate comparing with one of the traditional algorithms and the presented algorithm proves to be quite effective.