DIRECT MEASUREMENT OF RELATIVE ROTATION THROUGH PHASE INTERFEROMETRY

THE WORD DIRECT IN THE TITLE OF THIS PROPOSAL REFERS TO THE DETECTION TECHNIQUE. PREVIOUS ROTATION SENSING SCHEMES ACTUALLY MEASURE THE LINEAR MOTION CAUSED BY ROTATION, SUCH AS, PENDULOUS ACTION OF THE DISPLACEMENT OF THE TIP OF THE CANTILEVER UPON DEFLECTION. THE MAJOR DISADVANTAGE OF THIS METHOD IS THAT IT CANNOT DIFFERENTIATE BETWEEN THE ROTATION AND THE LINEAR MOTION OF THE OBJECT IN QUESTION. THIS RESTRICTS ITS APPLICABILITY TO SITUATIONS WHERE THE AXIS OF ROTATION IS WELL DEFINED. MOREOVER, IT DOES NOT ALLOW SPATIAL AMPLIFICATION, I.E., THE CHANGE IN THE OPTICAL PATH LENGTH DIFFERENCE IS EQUAL TO THE LINEAR DISPLACEMENT OF THE OBJECT. THE DIRECT MEASUREMENT OF ROTATION, ON THE OTHER HAND, IS INHERENTLY INSENSITIVE TO LINEAR MOTION AND ALLOWS A PATH LENGTH DIFFERENCE MANY TIMES THE ACTUAL DISPLACEMENT OF THE OBJECT. INTERFEROMETRIC TECHNIQUES BASED ON THIS PRINCIPLE ARE MUCH MORE SENSITIVE THAN THE PREVIOUS ONES. TWO DIFFERENT METHODS TO EFFECT THE MEASURMENT OF DIRECT ROTATION ARE PRESENTED AND THEIR COMBINATION SUGGESTED TO PRODUCE THE ULTIMATE ROTATION SENSOR. THIS CONCEPT IS EXTENDED TO ALL THE CONVENTIONAL INTERFEROMETER CONFIGURATIONS AND WOULD PRODUCE AT LEAST TWO ORDERS OF MAGNITUDE IMPROVEMENT IN RESOLUTION AND SIGNAL TO NOISE RATIO OVER PREVIOUS INSTRUMENTS.