Optical measurement system with polarization compensation, and corresponding method

• US 20150146192A1
• Filed: 06/04/2013
• Published: 05/28/2015
• Est. Priority Date: 06/05/2012
• Status: Active Grant

• Current Assignee: VC VIII Polytech Holding APS
• Original Assignee: Technische Universitat Munchen
• Inventors: Buck, Thorbjrn, Hoffmann, Lars, Mller, Mathias, Wojtech, Rolf
• Granted Patent: US 9,383,272 B2
• Time in Patent Office: Days
• US Class Current: 356/33
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: G01L 25/00 Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency

Abstract

A method for the adjustment of an optical measurement system comprises providing an optical measurement system, which comprises, as optical elements, a beam splitter; a first photo sensor, exposed by a first partial beam from the beam splitter; an optical filter; a second photo sensor, arranged downstream of the optical filter, exposed by a second partial beam from the beam splitter. Additionally, the angularity and relative position between multiple optical elements is designed to be adjustable. The method further comprises providing a device for generating a difference signal from the two photo sensors; providing a light source with periodically varying polarization; irradiating the light in the beam splitter, so that the two respective photo sensors are exposed by a partial beam; generating a difference signal of the output signals of the photo sensors; varying the position and/or angularity of at least one optical element, and observing the difference signal, determine the combination of angularity/position of the elements where a minimum difference signal is achieved, and configuring the angularity of the optical elements to the determined values. Further, a corresponding system is proposed.

Claims

1-10. -10. (canceled)

11. A Method for the adjustment of an optical measurement system, comprising:

providing an optical measurement system, which comprises, as optical elements;

a beam splitter;

a first photo sensor, exposed by a first partial beam from the beam splitter;

an optical filter;

a second photo sensor, arranged downstream of the optical filter, exposed by a second partial beam from the beam splitter,

wherein the angularity and relative position between multiple optical elements is arranged to be adjustable;

providing a device for generating a difference signal from the signals of both photo sensors;

providing a light source with periodically varying polarization;

irradiating the light into the beam splitter, so that both photo sensors are exposed by each respective partial beam;

generating a difference signal of the output signals of the photo sensors;

varying the position and/or angularity of at least one optical element, and observation of the difference signal;

determining the combination of angularity/position of the elements which achieves a minimum difference signal.

12. The method according to claim 11, further comprising:

varying the frequency of the incident light in addition to the variation of the polarization.

13. The method for adjustment of a measurement system according to claim 11, wherein the respective difference signals from the output signals of the photo sensors are stored with the corresponding angular data of the individual components in an electronic storage device.

14. The method for adjustment of a measurement system according to claim 11, wherein after scanning over the adjustment range of the optical elements, it is automatically determined which angularities result in a minimum difference output signal, and whereupon the respective photo sensor is attached and fixed in the corresponding position.

15. The method for adjustment of a measurement system according to claim 11, wherein the polarization of the incident light is generated through shifted λ

/4 plates.

16. A system for polarization-compensated adjustment of an optical measurement system, comprising:

a beam splitter;

a first photo sensor, arranged to be exposed by a first partial beam from the beam splitter;

an optical filter, arranged to be exposed by a second partial beam from the beam splitter;

a second photo sensor arranged downstream of the optical filter;

a light source for light with periodically varying polarization, wherein the polarization is periodically varied by active elements.

17. The system according to claim 16, further comprising an electronic controlling device for determining the difference output signals of the photo sensors;

as well as regulator control elements for varying the angularity of the photo sensor.

18. The system according to claim 17, wherein the controlling device is designed to perform an adjustment method comprising:

providing an optical measurement system, which comprises, as optical elements;

a beam splitter;

a first photo sensor, exposed by a first partial beam from the beam splitter;

an optical filter;

a second photo sensor, arranged downstream of the optical filter, exposed by a second partial beam from the beam splitter,

wherein the angularity and relative position between multiple optical elements is arranged to be adjustable;

providing a device for generating a difference signal from the signals of both photo sensors;

providing a light source with periodically varying polarization;

irradiating the light into the beam splitter, so that both photo sensors are exposed by each respective partial beam;

generating a difference signal of the output signals of the photo sensors;

varying the position and/or angularity of at least one optical element, and observation of the difference signal;

determining the combination of angularity/position of the elements which achieves a minimum difference signal.

19. Use of a system according claim 16 for measuring a mechanical quantity, wherein the system further comprises a fiber Bragg grating.

20. Use according to claim 19, comprising:

applying the mechanical quantity to the fiber Bragg grating, so that the Bragg wavelength of the fiber Bragg grating is changed by the mechanical quantity;

splitting the secondary light output from the fiber Bragg grating by use of a beam splitter into a first and second partial beam;

filtering the secondary light modified by the fiber Bragg grating depending on the mechanical quantity, by use of the optical filter.

determining the intensity of the filtered first and second partial beams of secondary light;

comparing the determined intensities of the filtered first and second secondary light; and

determining the mechanical quantity from the intensity comparison.