Patent ID: 7113284
Filing Date: 2006-09-26
Classification: G01B,H01L

Abstract:
1. A system for measuring a height of an object comprising: a first electromagnetic signal source for transmitting an electromagnetic signal; a beam splitter for receiving said electromagnetic signal and outputting a first signal toward a first position on the object at a first angle and a second signal toward said first position on the object at a second angle, wherein said first and second signals are electromagnetic signals; a first retro-reflection unit for reflecting a first single reflected signal toward said first position on said object, wherein said first single reflected signal is a portion of said first signal that reflects off of the object; a first detector to receive a first double reflected signal, wherein said first double reflected signal is a portion of said first single reflected signal that reflects off of said object and for generating a first output in response to said first double reflected signal; a second retro-reflection unit for reflecting a second single reflected signal toward said first position on said object, wherein said second single reflected signal is a portion of said second signal that reflects off of said object; a second detector to receive a second double reflected signal wherein said second double reflected signal is a portion of said second single reflected signal that reflects off of said object and for generating a second output in response to said second double reflected signal; and a processor, that receives said first and second output and generates a material independent signal representing a height of said first position, said material independent signal being independent of the type of material comprising the object.