Tracking Apparatus and Method

Abstract

A tracking apparatus includes a photosensor. The apparatus includes a pattern emitting base station. The apparatus includes a computer that tracks the photosensor to sub-millimeter accuracy using the pattern emitted by the base station. A method for tracking.

1 . A tracking apparatus comprising:
 a photosensor;   a pattern emitting base station; and   a computer that tracks the photosensor to sub-millimeter accuracy using the pattern emitted by the base station.   
     
     
         2 . The apparatus of  claim 1  wherein the base station includes a disk with a motor that rotates the disk. 
     
     
         3 . The apparatus of  claim 2  wherein the disk has an outer edge with a sequence of transmissive fraction patterns. 
     
     
         4 . The apparatus of  claim 3  wherein there are between 40 and 240 diffraction patterns. 
     
     
         5 . The apparatus of  claim 4  wherein the base station includes at least one laser behind the rotating patterns of the disk which emits light through the rotating patterns. 
     
     
         6 . The apparatus of  claim 5  wherein the base station includes 4 lasers placed at regular angular locations of 0, π/2, π and 3 π/2 with respect to the disk. 
     
     
         7 . The apparatus of  claim 6  wherein each pattern causes collimated laser light which impinges upon it from behind to scatter in a structured stripe pattern. 
     
     
         8 . The apparatus of  claim 7  wherein each emitted stripe runs perpendicular to a radius of the disk, and the stripe pattern varies in the disk's radial direction. 
     
     
         9 . The apparatus of  claim 8  wherein at least one of the diffraction patterns is a synchronization pattern. 
     
     
         10 . The apparatus of  claim 9  wherein there is a blanking interval between two diffraction patterns. 
     
     
         11 . The apparatus of  claim 10  wherein a micro-position of the photosensor is determined by fitting a sine wave to a received time-varying micro-measurement associated with the micro-patterns, where a phase of the sine wave determines the micro disposition of the photosensor, with the phase shifting linearly with position of the photosensor. 
     
     
         12 . A method for tracking comprising the steps of:
 a photosensor;   emitting a pattern with a base station. and   tracking a photosensor with a computer to sub-millimeter accuracy using the pattern emitted by the base station.