High resolution compass card position decoder

Apparatus for determining the angular position of a shaft comprising:

• a disk mounted at its center to said shaft, said disk having an inner pattern including a single inner spiral running 360.degree. from a first circular position to a second circular position, and an outer peripheral pattern including a series of lines each running at an angle to the radius of said disk from a third circular position to a fourth circular position;
• means along a first predetermined disk radius for detecting the position along said first radius of said single inner spiral so as to decode gross angular position;
• and
• means along a second predetermined disk radius for detecting the position along said second radius of one of said lines so as to decode fine angular position.

Apparatus for detecting the angular position of a shaft comprising:

• a disk mounted at is center to said shaft, said disk having an inner digital encoding pattern and an outer peripheral pattern, said outer peripheral pattern including a series of lines each running at an angle to a radius of said disk from an inner circular position to an outer circular position;
• means along a first predetermined disk radius for decoding the angular position of said disk from said digital encoding pattern so as to decode gross angular position;
• and
• means along a second predetermined disk radius for detecting the position along said second radius of one of said lines so as to decode fine angular position.