Optical sensor for rotational movements having an optical running period element

• US 5,440,389 A
• Filed: 02/17/1994
• Issued: 08/08/1995
• Est. Priority Date: 09/02/1991
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Drabarek, Pawel
• Primary Examiner(s): Turner, Samuel A.
• Application Number:
  US08/196,236
• Time in Patent Office: 537 Days
• Field of Search: 356/350
• US Class Current: 356/460
• CPC Class Codes: G01C 19/723 Heterodyning fibre optic gyrometers

Abstract

An optical sensor for rotational movements is proposed that includes a semiconductor laser that is at least intermittently activated, and whose frequency-modulated beam is split into two partial beams that respectively pass through an annular optical fiber arrangement in opposite directions, are subsequently superposed as coupled-out signals and conducted to a photodetector that emits an output signal that has a predeterminable heterodyne frequency, and whose phase position permits the determination of the rate of rotation of the arrangement with respect to a reference signal. The sensor of the invention can be installed into integrated optics, wherein all of the optical beams can be guided in optical fibers. The sensor of the invention is particularly suited as an optical fiber gyro or a rotation rate sensor.

Claims

1. An optical sensor for detecting rotational movements, comprising:

a laser beam source for emitting a beam;

a modulator for modulating a frequency of the beam of the laser beam source;

means for splitting the beam emitted by the laser into first and second partial beams;

an annular optical fiber arrangement having a first beam path extending in a first direction around the annular optical fiber arrangement and a second beam path extending in a second direction around the annular optical fiber arrangement, the first direction being opposite to the second direction, the first partial beam being coupled into the annular optical fiber arrangement in the first direction, and the second partial beam being coupled into the annular optical fiber arrangement in the second direction;

a first beam coupler in a beam path of the first partial beam and a beam path of the second partial beam which is coupled out of the annular optical fiber arrangement after the second partial beam has passed through the annular optical fiber arrangement;

a second beam coupler in a beam path of the second partial beam and a beam path of the first partial beam which is coupled out of the annular optical fiber arrangement after the first partial beam has passed through the annular optical fiber arrangement;

a photodetector for receiving a first coupled-out partial beam and a second coupled-out partial beam and for generating an output signal, the first coupled-out partial beam being derived from the first partial beam coupled out of the annular optical fiber arrangement, and the second coupled-out partial beam being derived from the second partial beam coupled out of the annular optical fiber arrangement;

an optical running period element in the beam path of one of the first partial beam, the first coupled-out partial beam, the second partial beam, and the second coupled-out partial beam; and

a phase comparator for determining a phase difference between a signal related to the modulation of the frequency of the beam of the laser beam source and the output signal of the photodetector, and for determining a rate of rotation of the annular optical fiber arrangement based on a detected phase difference.

2. A sensor as defined in claim 1, wherein the optical beams are guided in optical fibers.

3. A sensor as defined in claim 1, further comprising a third coupler in the beam paths of the first and second coupled-out partial beams for superposing the first and second coupled-out partial beams.

4. A sensor as defined in claim 1, wherein the signal related to the modulation of the frequency of the beam of the laser beam source has a first time interval and the output signal of the photodetector has a second time interval, the first and second time intervals being substantially equal in duration.

5. A sensor as defined in claim 1, wherein the laser beam source is a semiconductor laser.

6. An optical sensor for detecting rotational movements, comprising:

a laser beam source for emitting a beam, the laser beam source being activated for a first predetermined time interval and deactivated for a second predetermined time interval;

a modulator for modulating a frequency of the beam of the laser beam source;

means for splitting the beam emitted by the laser into first and second partial beams;

an annular optical fiber arrangement having a first beam path extending in a first direction around the annular optical fiber arrangement and a second beam path extending in a second direction around the annular optical fiber arrangement, the first direction being opposite to the second direction, the first partial beam being coupled into the annular optical fiber arrangement in the first direction, and the second partial beam being coupled into the annular optical fiber arrangement in the second direction;

a first beam coupler in a beam path of the first partial beam and a beam path of the second partial beam which is coupled out of the annular optical fiber arrangement after the second partial beam has passed through the annular optical fiber arrangement;

a second beam coupler in a beam path of the second partial beam and a beam path of the first partial beam which is coupled out of the annular optical fiber arrangement after the first partial beam has passed through the annular optical fiber arrangement;

a photodetector for receiving a first coupled-out partial beam and a second coupled-out partial beam and for generating an output signal, the first coupled-out partial beam being derived from the first partial beam coupled out of the annular optical fiber arrangement, and the second coupled-out partial beam being derived from the second partial beam coupled out of the annular optical fiber arrangement;

an optical running period element in the beam path of one of the first partial beam, the first coupled-out partial beam, the second partial beam, and the second coupled-out partial beam;

an optical short-circuit between the first and second couplers for supplying a portion of the first partial beam to the photodetector via the second beam coupler as a first reference beam, and for supplying a portion of the second partial beam to the photodetector via the first beam coupler as a second reference beam; and

a phase comparator for determining a phase difference between a signal related to the modulation of the frequency of the beam of the laser beam source and the output signal of the photodetector, and for determining a rate of rotation of the annular optical fiber arrangement based on a detected phase difference.

7. A sensor as defined in claim 6, wherein the optical beams are guided in optical fibers.

8. A sensor as defined in claim 6, further comprising a third coupler for superposing the first and second coupled-out partial beams.

9. A sensor as defined in claim 6, wherein the first predetermined time interval and the second predetermined time interval are substantially equal in duration.

10. A sensor as defined in claim 6, wherein the laser beam source is a semiconductor laser.

11. An optical sensor for detecting rotational movements, comprising:

a laser beam source for emitting a beam;

a modulator for modulating a frequency of the beam of the laser beam source;

means for splitting the beam emitted by the laser into first and second partial beams;

an annular optical fiber arrangement having a first beam path extending in a first direction around the annular optical fiber arrangement and a second beam path extending in a second direction around the annular optical fiber arrangement, the first direction being opposite to the second direction, the first partial beam being coupled into the annular optical fiber arrangement in the first direction, and the second partial beam being coupled into the annular optical fiber arrangement in the second direction;

a first beam coupler in a beam path of the first partial beam and a beam path of the second partial beam which is coupled out of the annular optical fiber arrangement after the second partial beam has passed through the annular optical fiber arrangement;

a second beam coupler in a beam path of the second partial beam and a beam path of the first partial beam which is coupled out of the annular optical fiber arrangement after the first partial beam has passed through the annular optical fiber arrangement;

a first photodetector for receiving a first coupled-out partial beam and a second coupled-out partial beam and for generating an output signal, the first coupled-out partial beam being derived from the first partial beam coupled out of the annular optical fiber arrangement, and the second coupled-out partial beam being derived from the second partial beam coupled out of the annular optical fiber arrangement;

an optical running period element in the beam path of one of the first partial beam and the second partial beam;

a reference photodetector for receiving a portion of the first partial beam coupled out of the first coupler as a first reference beam and a portion of the second partial beam coupled out of the second coupler as a second reference beam and for generating a reference signal; and

a phase comparator for determining a phase difference between the reference signal of the reference photodetector and the output signal of the first photodetector, and for determining a rate of rotation of the annular optical fiber arrangement based on a detected phase difference.

12. A sensor as defined in claim 11, wherein the optical beams are guided in optical fibers.

13. A sensor as defined in claim 11, further comprising a third coupler in the beam paths of the first and second coupled-out partial beams for superposing the first and second coupled-out partial beams.

14. A sensor as defined in claim 13, further comprising a fourth coupler in a beam path of the first reference beam and a beam path of the second reference beam for superposing the first reference beam and the second reference beam.

15. A sensor as defined in claim 12, wherein the signal related to the modulation of the frequency of the beam of the laser beam source has a first time interval and the reference signal and the output signal of the reference photodetector and of the first photodetector, respectively, have a second time interval, the first and second time intervals being substantially equal in duration.

16. A sensor as defined in claim 14, wherein the means for splitting the beam emitted by the laser into first and second partial beams comprises a fifth coupler.

17. A sensor as defined in claim 11, wherein the laser beam source is a semiconductor laser.