Radio frequency excited ring laser gyroscope

• US 5,196,905 A
• Filed: 04/06/1990
• Issued: 03/23/1993
• Est. Priority Date: 06/22/1988
• Status: Expired due to Fees

• Current Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Hahn, Tae W., Jabr, Salim N.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US07/517,644
• Time in Patent Office: 1,082 Days
• Field of Search: 372/94, 372/87, 372/64, 372/137, 372/82, 356/350
• US Class Current: 356/467
• CPC Class Codes: G01C 19/661 details
• CPC Class Codes: H01S 3/038 Electrodes, e.g. special shape, configuration or composition
• CPC Class Codes: H01S 3/083 Ring lasers fibre ring lasers H01S3/06791
• CPC Class Codes: H01S 3/0975 using inductive or capacitive excitation

Abstract

A radio frequency excitation system is disclosed for use in conjunction with a ring laser gyroscope. The radio frequency excitation system is comprised of a closed resonant cavity which surrounds a helical coil driven at a high radio frequency at a range of 5 to 550 megahertz. This closed resonant coil surrounds one leg of a ring laser gyroscope which is carved out and exposed so that it may be surrounded by the resonant cavity. Using such a radio frequency excitation system eliminates the need for high power DC discharge components such as cathodes and anodes, as well as problems inherent with properly sealing the cathodes and anodes to the monolithic frame of the ring laser gyroscope.

Claims

1. A ring laser gyroscope, comprising:

a resonant optical cavity formed within a monolithic block, said block defining a closed optical path, defined by at least three legs, having a gain medium therein; and

,

a closed Radio-Frequency cavity resonator positioned along a portion of said closed optical path, including at least one of said legs, which applies a localized longitudinal radio frequency signal for exciting discharge of the gain medium;

said closed Radio-Frequency cavity resonator having a helical coil powered up by a power source exhibiting reduced power dissipation surrounding a portion of said closed optical path; and

,

said helical coil contained within an enclosed conductive resonator shield, said helical coil and enclosed conductive resonator shield forming a high-Q, distributed parameter coaxial Radio-Frequency resonator assembly, and substantially aligned according to the following equations;

space="preserve" listing-type="equation">Q.sub.u =50 D f.sub.o.sup.1/2 ;

and,

space="preserve" listing-type="equation">N=(1900/f.sub.o D) turns;

where,

Q_u is unloaded Q (quality factor);

D is the inside diameter of the resonator shield;

f_o is a resonant frequency (MHz) of said resonator assembly; and

,

N is the total number of windings of said helical coil.

2. The ring laser gyroscope of claim 1, wherein:

said block is made from a dielectric material having a plurality of tubular bores connected end to end in a polygonal configuration defining said closed optical path;

at least one side of said body being carved out to allow at least one of said tubular bores to be surrounded by said helical coil and enclosed conductive resonator shield;

whereby discharge of the gain medium of the ring laser gyroscope is achieved.

3. The ring laser gyroscope of claim 1, wherein an RF oscillator is connected to said closed Radio-Frequency cavity resonator to supply said localized longitudinal radio frequency signal to said resonant optical cavity to achieve gain medium discharge within said ring laser gyroscope.

4. The ring laser gyroscope of claim 3, wherein the RF oscillator provides a radio frequency signal within a range of 5 to 550 megahertz.

5. The ring laser gyroscope of claim 1, wherein:

said closed Radio-Frequency cavity resonator applies a localized longitudinal half wave radio frequency signal along a portion of said closed optical path for exciting discharge of the gain medium.

6. The ring laser gyroscope of claim 1, wherein:

said closed Radio-Frequency cavity resonator applies a localized longitudinal quarterwave wave radio frequency signal along a portion of said closed optical path for exciting discharge of the gain medium.

7. The ring laser gyroscope of claim 1, wherein the helical coil of said closed Radio-Frequency cavity resonator is powered up by an RF oscillator system connected to said closed Radio-Frequency cavity resonator to supply radio frequency signals to said cavity resonator, said oscillator system including:

an RF oscillator;

means for regulating said RF oscillator to provide a radio frequency signal to said helical coil within a predetermined rane;

said regulating means including frequency control means coupled to phase lock loop means, said phase lock loop means controlling regulation of frequency provided by said RF oscillator to said helical coil; and

means for controlling power provided to said Radio-Frequency cavity resonator including photodetection means coupled to a signal comparator means, said signal comparator means adjusting an attenuator means with reference to a pre-determine optimum power supply level.

8. The ring laser gyroscope of claim 1, including:

feedback means for regulating said Radio-Frequency cavity resonator to provide a stable radio frequency signal to said helical coil within a predetermined frequency and power range;

whereby, excitation is lowered with minimal power dissipation and radio frequency interference.

9. The ring laser gyroscope of claim 8, wherein:

said feedback means for regulating said Radio-Frequency cavity resonator includes;

photodetection means for controlling and stabilizing the power provided to said Radio-Frequency cavity resonator; and

,

frequency control means for locking in the Radio-Frequency cavity resonator at a stable frequency.

10. In a split gain multi-mode ring laser gyroscope, including a resonant cavity defining a cloed out-of-plane optical path having a gain medium therein, comprising:

an optical pathway having at least four legs;

at least on of said legs of said optical pathway being carved out to form an exposed leg that is integral with a ringe laser gyroscope frame;

said exposed leg having a radio frequency helical coil wound around its length;

said radio frequency helical coil surrounded by a closed resonant shield forming a resonant cavity around said radio frequency coil;

a permanent magnet surrounding said resonator shield, said coil and said resonator shield being concentric within said permanent magnet;

whereby, a radio frequency-excited split gain multi-mode ring laser gyroscope is provided where a permanent magnet necessary to achieve split gain within the ring laser gyroscope is positioned along the same axis as the radio frequency helical coil and closed resonant shield so that the excited active medium which arises is confined to the length of said permanent magnet.

11. A ring laser gyroscope comprising:

a resonant cavity defining a closed optical path having a gain medium therein;

a closed Radio-Frequency cavity resonator which applies a radio frequency signal for exciting discharge of the gain medium, including;

a helical coil surrounding a portion of said closed optical path;

said helical coil contained within an enclosed conductive resonator shield;

an RF oscillator connected to said closed Radio-Frequency cavity resonator to supply radio frequency signals to said resonant cavity;

means for regulating said RF oscillator to provide a radio frequency signal to said helical coil within a predetermined range;

said regulating means including frequency control means further comprising frequency detection coupling and amplification means coupled to phase lock loop means, said phase lock loop means controlling regulation of frequency provided by said RF oscillator to said helical coil; and

means for controlling power provided to said closed Radio-Frequency cavity resonator including photodetection means coupled to a signal comparator means, said signal comparator means adjusting an attenuator means with reference to a pre-determined optimum power supply level;

whereby, discharge of the gain medium of the ring laser gyroscope is achieved.