Pulsed polarization device for measuring angle of rotation

Apparatus for measuring rotational angle of a movable target element with relation to a reference position, said apparatus comprising:

• means for directing non-polarized electromagnetic waves along paths toward first and second electromagnetic wave detectors;
• reference position polarizer means mounted transverse to the paths for polarizing the waves in a reference orientation;
• first and second polarization analyzers rotatably mounted on the movable target element in a common plane transverse to the paths between said reference position polarizer means and said first and second detectors, said first and second analyzers being disposed adjacently to provide a fixed angle greater than 0.degree. and less than 90.degree. between polarization directional axes of said first and second adjacent analyzers, said first and second detectors being responsive to the electromagnetic waves for generating first and second output signals representing the intensity of the waves received by each of said first and second detectors along paths corresponding to said first and second analyzers;
• and
• means responsive to said first and second output signals from said detectors for determining equality between the amplitude ratio of first and second output signals corresponding to said first and second analyzers and a reference value and generating a signal representative of rotational angle between the movable element and the reference position when said equality occurs.

In a device for measuring rotational angle wherein plane polarized light is directed to be received by rotatable polarization analyzer means operatively connected to a remote rotary body for which rotational angle relative to a reference position is measured, the improvement which comprises:

• a plurality of polarization analyzers mounted side-by-side transverse to plane polarized light received by said analyzer means, each of said analyzers having a directional axis of linear polarization;
• means for holding said analyzers to maintain a substantially fixed axial angle between said analyzers about an axis of rotation;
• photosensor means for receiving light independently through each of said analyzers and generating time pulsed electrical signals with amplitude representative of modulated light intensity for each analyzer;
• and
• means for determining equality between the amplitude ratio of said time pulses electrical signals and a reference value adjacent photosensor signals and generating an output signal representative of rotational angle when said equality occurs.