A novel optical approach based on speckle effect produced by VCSEL for tracking on glass surface

摘要

The paper presents a novel optical approach to realize tracking on glass based on speckle effect produced by vertical-cavity surface-emitting laser (VCSEL). The range of incident angle has been investigated which shows incident angle in the range of 75 to 90 degrees is favorable to acquire a pure speckle field with purity better than 90%. In the system, nearly grazing angle of incidence 85 degrees is introduced, and big operating current of VCSEL and high gain of CCD are adopted to ensure signal detected. We analyze the cause of background contained in the image and remove them by placing a barrier between the laser diode and charge coupled device (CCD) and an infrared filter in front of CCD. After above-mentioned improvement of the system, a good linear dependence between displacement of speckle images and amount of glass translation is proved by experiment and the slope of the fitted line agrees well with theoretical predictions, the accuracy of tracking system is better than 4%.