A system for sensing an absolute two-dimensional position of an object
having a two-dimensional target pattern thereon comprises a sensor and a
controller. The sensor is for capturing an image of a subset of the
target pattern. The controller is for generating a first image vector
representing summations of rows of pixel values from the image, and a
second image vector representing summations of columns of pixel values
from the image. The controller is configured to determine an absolute
two-dimensional position of the subset of the target pattern with respect
to the origin of the target pattern based on the first image vector, the
second image vector and target vectors that represent the target pattern.