Method and device for stabilizing the scale factor of a fiber optic gyroscope

• US 6,373,048 B1
• Filed: 07/20/2000
• Issued: 04/16/2002
• Est. Priority Date: 01/21/1998
• Status: Expired due to Term

• Current Assignee: Litef GmbH (Northrop Grumman Corporation), Litton Systems Incorporated (Northrop Grumman Corporation), Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litef GmbH (Northrop Grumman Corporation)
• Inventors: Tschanun, Wolfgang
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Kiknadze, Irakli
• Application Number:
  US09/600,723
• Time in Patent Office: 635 Days
• Field of Search: 250/231.12, 250/214, 250/205, 356/450, 356/464
• US Class Current: 250/231.12
• CPC Class Codes: G01C 19/721 Details

Abstract

A method and apparatus for stabilizing the scale factor of a fiber optic gyroscope in which a superluminescence diode or broadband multimode laser comprises the light source. The emission bandwidth injected into a fiber end from the light source is limited to a considerably narrower transmission bandwidth within the wavelength band of the intensity characteristic of the light by a narrowband optical filter. The temperature at the filter is measured, and the transmission bandwidth quickly corrected by means of a pre-calibrated look-up table when optical interference filters are employed. The readjusted wavelength value is used for scale factor calculations.

Claims

1. A method for scale factor stabilization of a fiber optic gyroscope of the type in which the emission bandwidth of the intensity characteristic of a light source injected into a fiber end is limited by a narrowband optical filter to a considerably narrower transmission bandwidth, said method comprising the step of readjusting the transmission bandwidth of the optical filter as a function of the measured temperature at said filter.

2. A method as defined in claim 1 further comprising the steps of:

a) measuring the intensity characteristic of the instantaneous light wavelength with respect to the temperature; and

b) employing said intensity characteristic for active electronic readjustment of the transmission bandwidth of said optical filter.

3. A method as defined in claim 2 additionally comprising the step of carrying out the temperature-dependent correction of transmission bandwidth of said optical filter to wavelength values employed for scale factor calculation on the basis of said measured filter temperature with pre-calibrated stored values.

4. In a fiber optic gyroscope of the type that includes an optical filter arrangement in the light path whose passband characteristic is matched to the wavelength band of the gyroscope light source for limiting the bandwidth of the light carried in the fiber, the improvement comprising, in combination:

a) measuring the instantaneous temperature of said optical filter arrangement; and

b) a device for correcting said measured temperature value using a calibrated, stored temperature wavelength table for supplying a corrected value for calculating the scale factor via gyroscope electronics.

5. Apparatus as defined in claim 4 wherein said filter arrangement is arranged in said light path upstream of a first beamsplitter.

6. Apparatus as defined in claim 4 or 5, characterized in that the filter arrangement and/or an additional filter arrangement are arranged in the light path from the first beamsplitter to an electro-optical detector.

7. Apparatus as defined in claim 4 wherein said filter element within said filter arrangement comprises a dielectric optical filter.

8. Apparatus as defined in claim 4 or 7, further including:

a) said filter element within said filter arrangement comprising an optical interference filter; and

b) said filter element comprises a dielectric coating applied on a glass body.

9. Apparatus as defined in claim 8 wherein said filter arrangement comprises:

a) a first refractive index gradient lens coupled to an input fiber;

b) a second refractive index gradient lens coupled to an output fiber; and

c) said interference filter is located between said refractive index gradient lenses.

10. Apparatus as defined in claim 5 wherein the dielectric characteristics of said optical filter arrangement comprise a function of the temperature measured at the filter.

11. Apparatus as defined in claim 9 further including:

a) said filter arrangement is formed from optically bonded elements; and

b) said arrangement is hermetically sealed.

12. Apparatus as defined in claim 11 further including a temperature sensor integrated into said filter arrangement.