perform normal navigation functions e g by increasing its speed level of integration memory capacity etc to support pattern detection the surface 20 may be any type of surface examples of the surface 20 include paper cardboard painted surfaces wood surfaces metals etc the pattern 22 may be any pattern examples of the pattern 22 include bar codes watermarks including invisible watermarks fingerprints text icons forensic features etc the image sensor 12 takes images of the surface 20 for example the image sensor 12 acquires a series of images 30 of the surface 20 as a user moves the optical navigation device 10 across the surface 20 when detecting the pattern 22 each image in the series of images 30 includes a two dimensional array of pixel data values sampled from the surface 20 the optical navigation device 10 may include a light source for illuminating the surface 20 when taking images with the image sensor 12 a light source of the optical navigation device 10 may be adapted to a pattern recognition application for example an infrared led may be used to illuminated the surface 20 when the optical navigation device 10 is used to detect invisible patterns in the surface 20 e g patterns produced by infrared absorbing or reflecting ink a light source may be selected for its utility in illuminating particular types of patterns.