Optical measuring device using optical fibers

• US 4,249,076 A
• Filed: 11/17/1978
• Issued: 02/03/1981
• Est. Priority Date: 11/23/1977
• Status: Expired due to Term

• Current Assignee: Asea Aktiebolag (ABB Limited)
• Original Assignee: Asea Aktiebolag (ABB Limited)
• Inventors: Brogardh, Torgny, Persson, Anders, Bergstrom, Jan, Bertilson, Hans
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Hostetter, Darwin R.
• Application Number:
  US05/961,847
• Time in Patent Office: 809 Days
• Field of Search: 250/227, 250/231 R, 250/551, 250/205
• US Class Current: 250/227.23
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence
• CPC Class Codes: G01J 5/42 using Golay cells
• CPC Class Codes: G01L 9/0007 using photoelectric means G01L9/0076 takes precedence
• CPC Class Codes: G01L 9/0076 using photoelectric means

Abstract

In an optical measuring device for measuring physical magnitudes a sensor is actuated by the physical magnitude to be measured. An optical signal generator and processor provides light signals to the sensor and processes optical output signals transmitted from the sensor. Optical fibers conduct light to the sensor and transmit light signals therefrom to optical detectors. The sensor modulates at least a portion of the light transmitted thereto such that the modulated light output therefrom transmitted to the optic processor contains measuring components representative of the magnitude to be measured and stabilizing component signals independent of the magnitude. The optical processor separates the measuring components and the stabilizing components and generates at least one measuring signal and compensating signals for stabilizing the measuring device.

Claims

1. Optical measuring device for measuring physical magnitudes, comprising:

a sensor actuated by the physical magnitude to be measured;

means for generating optic input signals to said sensor;

means for processing optic output signals emanating from said sensor and including at least two optical detection means;

at least one optical input fiber for transmitting said optic input signals to said sensor and at least two optical output fibers for transmitting said optic output signals to said at least two optical detection means;

said sensor including means for modulating at least a portion of the light conducted thereto such that said optic output signals contain at least one measuring component representative of the magnitude to be measured and at least one stabilizing component with a smaller dependence on said physical magnitude than said measuring component; and

said means for processing further including means for separating said at least one measuring component and said at least one stabilizing component, and means for generating therefrom at least one measuring signal and at least one compensating signal, and means responsive to said at least one compensating signal for reducing the dependence of said measuring signal on instabilities in the the measuring device.

2. Optical measuring device according to claim 1 wherein said at least one measuring component is transmitted from said sensor to said means for processing by only one of said at least two optical output fibers, and said at least one stabilizing component is transmitted from said sensor to said means for processing by another of said at least two optical output fibers.

3. Optical measuring device according to claim 1 wherein each of said at least two optical output fibers transmits at least one of said measuring and one of said stabilizing components, and wherein said means for processing further includes subtraction means for forming said at least one measuring signal from the difference between the optic output signals transmitted by said at least two optical output fibers, and summation means for generating said at least one compensating signal from the sum of the optic output signals transmitted by said at least two optical fibers.

4. Optical measuring device according to claim 1 wherein each of said at least two optical output fibers transmits at least one of said measuring and one of said stabilizing components, said means for processing further includes summation means for forming said at least one measuring signal from the sum of the optic output signals transmitted by said at least two optical output fibers, and subtraction means for generating said at least one compensating signal from the difference between the optic output signals transmitted by said at least two optical output fibers.

5. Optical measuring device as in claim 1 wherein each of said at least two optical output fibers transmits at least one of said stabilizing components, said means for processing further includes subtraction means for forming at least one compensating signal from the difference between said stabilizing components from said at least two optical output fibers, and further comprising means responsive to said at least one compensating signal for controlling signal instabilities in said at least two optical output fibers, said means for generating, and said means for processing.

6. Optical measuring device as in claim 1 wherein said means for generating optic input signals generates two optic input signals and includes means for modulating said two optic input signals with different frequencies, there being one optical input fiber for transmitting each modulated optic input signal to said sensor, and said means for processing further includes separate filtering circuits for dividing the optic output signals from said at least two optical output fibers into at least two optical components, each originating respectively in each one of said two optic input signals, and means for forming said at least one measuring signal and said at least one compensating signal from said at least two optical components.

7. Optical measuring device as in claim 1 wherein said means for generating optic input signals generates two optic input signals during different time intervals, and said means for processing further includes sampling circuits for dividing the optic output signals from said at least two optic output fibers into at least two optical components, each originating respectively in each one of said two optic input signals, and means for forming said at least one measuring signal and said at least one compensating signal from said at least two optical components.

8. Optical measuring device as in claim 1, further comprising means for compensating for instabilities in said at least one optical input fiber, said at least two optical output fibers, said means for generating optic input signals and said means for processing by regulating said means for generating optic input signals to maintain said at least one compensating signal constant.

9. Optical measuring device as in claim 1 further comprising means for compensating for instabilities in said at least one optical input fiber, said at least two optical output fibers, and in said at least two optical detection means by regulating said at least two optical detection means to maintain said at least one compensating signal constant.

10. Optical measuring device as in claim 1 wherein said means for processing includes subtraction means for forming a compensating signal from the difference between the optic output signals transmitted from said at least two optical output fibers, with respect to stabilizing components originating in said means for generating optic input signals, and including means for controlling the sensitivity of said at least two detection means such that said compensating signal is substantially kept equal to zero.

11. Optical measuring device as in claim 1 wherein said means for generating optic input signals generates two optic input signals and there being an optical input fiber for transmitting each of said optic input signals, and said means for modulating including a screening plate having a transparent field therein for passing light from one of said two optic input fibers to said at least two optic output fibers on the opposite side of said screening plate, whereby movement of said one optic input fiber relative to said at least two optic output fibers generates measuring and stabilizing components therein, and said means for modulating further including means for transmitting light to said at least two optic output fibers with a constant relationship and independent of said movement, thereby generating stabilizing component signals for stabilization of said at least two optic output fibers and said at least two optical detection means.

12. Optical measuring device as in claim 1 wherein said means for generating optic input signals generates two optic input signals and there being an optical input fiber for transmitting each of said optic input signals, and said means for modulating including a screen having at least one gap therein extending between the two optic input and said at least two optic output fibers, and a mirror positioned behind said screen, whereby light reflected from one of said optical input fibers to said at least two optical output fibers is modulated to generate measuring and stabilizing components when said screen and/or mirror is moved relative to the two optical input and said at least two optical output fibers, and said sensor including a light path for transmission of the light from the other of the two optical input fibers to said at least two optical output fibers, which is not affected by movement of said screen and/or mirror.

13. Optical measuring device as in claim 1 including two optical input fibers, one of which conducts light to said sensor, two optical output fibers for transmitting light from said sensor to said at least two optical detection means, the other of said optical input fibers positioned close to said two optical output fibers to direct light substantially equally therein to generate stabilizing component signals.

14. Optical measuring device as in claim 1 including two optical input fibers for conducting light to said sensor, and said means for modulating including a mirror mounted to said sensor, and two optical output fibers for transmitting light reflected from said mirror to said optical detection means, one of said optical input fibers directing light onto said mirror to be reflected into each of said two optical output fibers, and the other of said optical input fibers being positioned to direct light equally into each of said two optical output fibers, one of said optical output fibers transmitting said at least one measuring component and the other of said optical output fibers transmitting said at least one stabilizing component.

15. Optical measuring device as in claim 1 further comprising a branched optical fiber having one branch for conducting light to said sensor, and another branch for transmitting light reflected from said sensor to one of said at least two optical output fibers, and another of said at least two optical output fibers mounted to receive light from said at least one optical input fiber.