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US 4,790,657 AGranted
Ring laser gyroscope curved blade flexure and support ring assembly and method
AssigneeLitton Systems, Inc.
InventorWilliam Kozma
Life of this patent
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AssigneeLitton Systems, Inc.
InventorWilliam Kozma
Estimating the term…
A dither flexure for a ring laser gyroscope includes a central portion and a plurality of curved vanes extending therefrom to connect to a flexure ring. The flexure ring includes a boss in a central portion thereof. A glass ceramic ring having a pair of end bosses is bonded to the boss around the flexure ring with the end bosses facing outward toward the ring laser gyroscope frame. The end bosses contact the ring laser gyroscope frame so that a void is formed opposite the flexure ring boss, which prevents transmission of radially directed stresses from the dither flexure to the frame. The curved blades have high resistance to off-axis vibrations and have high off-axis resonant frequencies so that very little coning and axis sag occur. Each blade has a curved portion and a straight portion, which provides a convenient location for mounting piezoelectric drive elements for dithering the ring laser gyroscope.
A dither flexure for a ring laser gyroscope formed in a frame having a mounting cavity therein, comprising:
A dither flexure for a ring laser gyroscope formed in a frame having a mounting cavity therein, comprising:
A ring laser gyroscope, comprising:
A ring laser gyroscope, comprising:
A method for dithering a ring laser gyroscope to reduce mode locking, comprising the steps of:
A method for dithering a ring laser gyroscope to reduce mode locking, comprising the steps of:
A method for forming a ring laser gyroscope, comprising the steps of:
A method for forming a ring laser gyroscope, comprising the steps of:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
Lock-in prevention: by mechanical means
Measuring distances, levels or bearings
Term ended 18 Mar 2006 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates generally to rotation sensors and particularly to ring laser gyroscope rotation sensors. Still more particularly, this invention relates to apparatus and methods for supporting a ring laser gyroscope frame to allow rotational motion about the input axis of the ring laser gyroscope to reduce the effects of lock-in and to provide extremely high stiffness for all other degrees of freedom to reduce coning errors.
A ring laser gyroscope employs the Sagnac effect to detect rotation. Two counterpropagating light beams in a closed loop will have transit times that differ in direct proportion to the rotation rate of the loop about an axis perpendicular to the plane of the loop. There are in general two basic techniques for utilizing the Sagnac effect to detect rotations. A first technique is the interferometric approach, which involves measuring the differential phase shift between two counterpropagating beams injected from an external source, typically a laser, into a Sagnac ring. The ring may be defined by mirrors that direct the light beams around the path or by a coil of optical fiber. Beams exiting the path interfere and create a pattern of light and dark lines that is usually called a fringe pattern. Absolute changes in the fringe pattern are indicative of rotation of the ring. The primary difficulty with such devices is that the changes are very small for rotation rates of interest in guidance applications.
The ring laser gyroscope uses the resonant properties of a closed cavity to convert the Sagnac phase difference between the counter propagating beams into a frequency difference. The high optical frequencies of about 10.sup.15 Hz for light used in ring laser gyroscopes cause the minute phase changes to become beat frequencies that are readily measured.
FIG. 1 is a plan view of a ring laser gyroscope showing a frame structure mounted on a curved blade dither flexure according to the present invention;
FIG. 2 is a plan view of the dither flexure of FIG. 1 and a support ring used to support the ring laser gyroscope frame upon the dither flexure of the present invention;
FIG. 3 is a cross sectional view taken along line 3--3 of FIG. 2 showing a bore in a lobe of a central portion of the dither flexure and showing a boss formed on an outer ring portion of the dither flexure of FIG. 2;
Referring to FIG. 1, a ring laser gyroscope 10 includes a frame 12 that has a generally rectangular shape with the corners cut off to form four mounting faces 14-17. A plurality of mirrors 18-21 are mounted on the mounting faces 14-17, respectively. A cavity 22 is formed in the frame 12 to form a path around the frame 12 between the mirrors 18-21.
A lasing medium 24 is positioned in the cavity 22 to produce counterpropagating light beams 26 and 28 therein. The lasing medium is typically a mixture of helium and neon confined to a region 30 of the cavity 22. Energy is delivered to the lasing medium 24 by a power supply (not shown) which applies voltage to a pair of anodes 32 and 34 and to a cathode 36. Other structures may be used for the ring laser gyroscope 10. A basic description of the ring laser gyroscope 10 is presented by way of example and not for limitation of the present invention to a particular ring laser gyroscope structure.
One of the mirrors, for example the mirror 18 is partly transmissive so that a portion of each beam enters a prism 38 mounted to the back of the mirror 18. The prism 38 is formed to combine the counterpropagating beams so that they interfere with one another before impinging upon a photodetector 40.