Laser-based deflection measuring method and apparatus
AssigneeStandard Oil Company (Indiana)
InventorRobert M. Kiehn
Life of this patent
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Abstract
A laser beam is passed through a naturally birefringent or optically active device contained within the laser cavity. The device is oriented so that its optical axis is parallel to the laser beam, thus producing no birefringence or optical activity in the cavity in the steady state. The slightest tilting of the birefringent, or optically active, element causes significant changes in the modes of excitation of the optical cavity which are detected by a photosensitive beat detector. Thus the deflection angle of the optical axis is measured directly in terms of a beat frequency. By combining Faraday or Fresnel-Fizeau effects with optical activity, quadrature mode operation of a ring-laser embodiment is achieved, and is used to improve signal stability and noise rejection.
Claims28
A displacement sensor comprising
- a laser including a plurality of reflectors which establish an optical path therebetween, one or more of said reflectors being partially light-transmissive;
- a laser amplifier contained within said optical path for generating a laser beam therein;
- an optically transmissive means disposed in said path, said optically transmissive means having an optical axis in a normal position parallel to the axis of said laser beam, and said optically transmissive means exhibiting optical anisotropy;
- means responsive to an external force to displace said optical axis of said optically transmissive means from said normal position;
- and
- a photosensitive beat detector positioned to intercept radiant energy exiting from said optical path through one or more of said partially light-transmissive reflectors, for detecting one or more difference frequencies between different modes of operation of said laser beam, said one or more difference frequencies resulting from the displacement of said optical axis of said optically transmissive means from said normal position.
A method for measuring displacement comprising the use of a laser including a plurality of reflectors which establish an optical path therebetween, one or more of said reflectors being partially light-transmissive, including the steps of:
- positioning a laser amplifier within said optical path for generating a laser beam therein;
- placing an optically transmissive means in said path, said optically transmissive means having an optical axis in a normal position parallel to the axis of said laser beam, and said optically transmissive means exhibiting optical anisotropy;
- supporting said optically transmissive means with means responsive to an external force to displace said optical axis of said optically transmissive means from said normal position;
- and
- positioning a photosensitive beat detector to intercept radiant energy exiting from said optical path through one or more of said partially light-transmissive reflectors, for detecting one or more difference frequencies between different modes of operation of said laser beam, said one or more difference frequencies resulting from the displacement of said optical axis of said optically transmissive means from said normal position.
A displacement sensor comprising
- a laser including a plurality of reflectors which establish an optical path for a ring laser beam, one or more of said reflectors being partially light-transmissive;
- a laser amplifier contained within said optical path for generating said ring laser beam;
- an optically transmissive means disposed in said path, said optically transmissive means having an optical axis in a normal position parallel to the axis of said ring laser beam, and said optically transmissive means exhibiting optical anisotropy;
- means responsive to an external force to displace said optical axis of said optically transmissive means from said normal position;
- and
- a photosensitive beat detector positioned to intercept radiant energy exiting from said optical path through one or more of said light-transmissive reflectors, for detecting one or more difference frequencies between different modes of operation of said ring laser beam, said one or more difference frequencies resulting from the displacement of said optical axis of said optically transmissive means from said normal position.
A method for measuring displacement comprising the use of a laser including a plurality of reflectors which establish an optical path for a ring laser beam, one or more of said reflectors being partially light-transmissive, including the step of:
- positioning a laser amplifier within said optical path for generating said ring laser beam therein;
- placing an optically transmissive means in said path, said optically transmissive means having an optical axis in a normal position parallel to the axis of said ring laser beam, and said optically transmissive means exhibiting optical anisotropy;
- supporting said optically transmissive means with means responsive to an external force to displace said optical axis of said optically transmissive means from said normal position;
- and
- positioning a photosensitive beat detector to intercept radiant energy exiting from said optical path through one or more of said partially light-transmissive reflectors, for detecting one or more difference frequencies between different modes of operation of said ring laser beam, said one or more difference frequencies resulting from the displacement of said optical axis of said optically transmissive means from said normal position.
Dependencies are inferred from the claim text.