Compact three-axis ring laser gyroscope

• US 5,757,490 A
• Filed: 07/31/1996
• Issued: 05/26/1998
• Est. Priority Date: 07/31/1996
• Status: Expired due to Fees

• Current Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Martin, Graham John
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US08/690,482
• Time in Patent Office: 664 Days
• Field of Search: 356/350
• US Class Current: 356/471
• CPC Class Codes: G01C 19/668 Assemblies for measuring along different axes, e.g. triads

Abstract

Compact triaxial multioscillator configurations are based upon frames of rhombic dodecahedron and truncated octahedral shapes as taught by U.S. Pat. No. 4,795,258. Three non-planar cavities, each comprising four intersecting bores, intersect within the frames. External Faraday rotator assemblies comprising reverse mirrors and associated permanent magnets in differing configurations eliminate the need for intracavity elements to obtain nonreciprocal splitting. In the rhombic dodecahedron-shaped frame, external Faraday rotator assemblies are fixed to three planar faces at each of which pairs of segments of each of the internal nonplanar cavities converge. In the truncated tetrahedral frame, a single external Faraday rotator assembly is fixed to the single planar face at which pairs of segments of the three nonplanar cavities converge in a pattern forming the apexes of a centered equilateral triangle. A cavity length control mirror is fixed to each of the other three block surfaces upon which pairs of segments of the three non-planar cavities converge.

Claims

1. A ring laser gyroscope for measuring rotation about three orthogonal axes comprising, in combination:

a) a three-dimensional frame;

b) the exterior of said frame comprising a plurality of planar surfaces defining a rhombic dodecahedron;

c) three intersecting closed non-planar cavities within said frame;

d) each of said cavities comprising four straight segments of equal lengths that converge at planar surfaces of said frame;

e) straight segments of at least two cavities converging at at least one planar surface of said frame;

f) means for creating nonreciprocal splitting of modes in accordance with the Faraday effect being fixed to each of three planar surfaces of said frame; and

g) each of said means includes (i) a disk-shaped mirror substrate, said substrate having opposed upper and lower surfaces, and being fixed to a planar surface of said frame, (ii) said upper surface of said substrate being substantially totally reflective and (iii) a pill-shaped permanent magnet being fixed to the upper surface of and coaxial with said substrate.

2. A ring laser gyroscope as defined in claim 1 wherein said substrate is quartz.

3. A ring laser gyroscope as defined in claim 1 wherein each of said three means for creating nonreciprocal splitting is fixed to a planar surface of said frame at which terminal ends of segments comprising a single nonplanar cavity converge.

4. A ring laser gyroscope for measuring rotation about three orthogonal axes comprising, in combination:

a) a three-dimensional frame;

b) the exterior of said frame comprising fourteen planar surfaces defining a truncated regular octahedron or tetrahedron;

c) three intersecting closed non-planar cavities within said frame;

d) each of said cavities comprising four straight segments of equal lengths, said segments of said cavities being arranged so that ends of adjacent segments of each of said cavities converge at a first, a second, a third and a fourth planar surface of said frame;

e) a pair of adjacent segments of one of each of said three cavities converging at the centers of said first, said second and said third planar surfaces;

f) adjacent segments of all of said cavities converging at said fourth planar surface in a pattern defining an equilateral triangle centered within said fourth planar surface;

g) means for creating nonreciprocal splitting of modes within all of said cavities in accordance with the Faraday effect being fixed to said fourth planar surface of said frame, said means comprising (i) a mirror substrate, (ii) the upper surface of said substrate being capable of reflecting at least a portion of incident light, and (iii) a magnet associated with said mirror substrate;

h) a cavity length control mirror fixed to each of said first, said second and said third planar surfaces of said frame; and

i) each of said cavity length control mirrors comprising (i) a disk having opposed surfaces, (ii) one surface of said disk having a reflective coating throughout, (iii) said surface having a curved central indentation and a flat peripheral region, and (iv) said disk being fixed to said planar surface so that said central indentation overlies said convergence of segments of a nonplanar cavity at the center of said planar surface and said flat peripheral region overlies said convergence of segments of said other two nonplanar cavities.

5. A ring laser gyroscope for measuring rotation about three orthogonal axes comprising, in combination:

a) a three-dimensional frame;

b) the exterior of said frame comprising fourteen planar surfaces defining a truncated regular octahedron or tetrahedron;

c) three intersecting closed non-planar cavities within said frame;

d) each of said cavities comprising four straight segments of equal lengths, said segments of said cavities being arranged so that ends of adjacent segments of each of said cavities converge at a first, a second, a third and a fourth planar surface of said frame;

e) a pair of adjacent segments of one of each of said three cavities converging at the centers of said first, said second and said third planar surfaces;

f) adjacent segments of all of said cavities converging at said fourth planar surface in a pattern defining an equilateral triangle centered within said fourth planar surface;

g) means for creating nonreciprocal splitting of modes within all of said cavities in accordance with the Faraday effect being fixed to said fourth planar surface of said frame, said means comprising (i) a mirror substrate, (ii) the upper surface of said substrate including a partially-transmissive reflective coating, and (iii) a magnet associated with said mirror substrate;

h) said substrate being generally disk-shaped with a central aperture;

i) said magnet being rod-shaped;

j) said rod-shaped magnet being coaxial with and extending both above and beneath said substrate through said aperture; and

k) a bore in said frame at the center of said fourth planar surface for receiving the lower portion of said rod-like magnet.