IP Library › Granted Patent US 7,038,785

Granted Patent B2

US 7,038,785 · App. 10/615,729 · Granted May 2, 2006

Filtered calculation of sensor array induced phase angle independent from demodulation phase offset of phase generated carrier

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Quick Facts

Patent No.: US 7,038,785
App. No.: 10/615,729
Granted: May 2, 2006
Kind: B2

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Abstract

A sensor array employs a parameter to induce a time-varying phase angle on an optical signal that comprises a phase generated carrier with a demodulation phase offset. An output signal from the sensor array is filtered to create a filtered signal. The phase angle is calculated independently of the demodulation phase offset through employment of the filtered signal.

Claims (235)

1. A method, a sensor array that employs a parameter to induce a time-varying phase angle φ on an optical signal that comprises a phase generated carrier with a demodulation phase offset β, the method comprising the steps of:

filtering an output signal from the sensor array to create a filtered signal; and

calculating the phase angle φ substantially independently of the demodulation phase offset β through employment of the filtered signal.

2. The method of claim 1 , further comprising the step of:

sampling an output signal from the sensor array to obtain a plurality of samples S n , wherein n=0 to x;

wherein the step of calculating the phase angle φ substantially independently of the demodulation phase offset β through employment of the filtered signal comprises the step of:

calculating the phase angle φ substantially independently of the demodulation phase offset β through employment of one or more of the plurality of samples S n .

3. The method of claim 2 , wherein the step of calculating the phase angle φ substantially independently of the demodulation phase offset β through employment of the one or more of the plurality of samples S n comprises the steps of:

calculating one or more quadrature terms and one or more in-phase terms through employment of one or more of the plurality of samples S n , wherein one or more of the one or more quadrature terms and one or more of the one or more in-phase terms are substantially independent from the demodulation phase offset β; and

calculating the phase angle φ through employment of the one or more quadrature terms and the one or more in-phase terms.

4. The method of claim 2 , wherein the output signal comprises a period T pulse , wherein the step of sampling the output signal from the sensor array to obtain the plurality of samples S n , wherein n=0 to x comprises the step of:

sampling the output signal from the sensor array to obtain a plurality of samples S n within a period T s , wherein n=0 to x, wherein T s is less than or equal to T pulse .

5. The method of claim 4 , wherein the step of calculating the phase angle φ substantially independently of the demodulation phase offset β through employment of the one or more of the plurality of samples S n comprises the steps of:

calculating the phase angle φ through employment of the one or more quadrature terms and the one or more in-phase terms.

6. The method of claim 5 , wherein the step of calculating the one or more quadrature terms and the one or more in-phase terms through employment of the one or more of the plurality of samples S n , wherein the one or more of the one or more quadrature terms and the one or more of the one or more in-phase terms are substantially independent of the demodulation phase offset β comprises the steps of:

calculating a set of quadrature terms Q j and a set of in-phase terms I k through employment of one or more of the plurality of samples S n , wherein j=0 to y, wherein k=0 to z;

calculating a quadrature term

∑

⁢

wherein Q s is substantially independent of the demodulation phase offset β;

calculating an in-phase term

∑

⁢

wherein I s is substantially independent of the demodulation phase offset β; and

calculating the constant C 1 such that a maximum magnitude of the quadrature term Q s and a maximum magnitude of the in-phase term I s comprise a substantially same magnitude for a modulation depth M of an operating range for the phase generated carrier.

7. The method of claim 6 , wherein x=7, y=3, z=1, wherein the step of calculating the set of quadrature terms Q j and the set of in-phase terms I k through employment of the one or more of the plurality of samples S n , wherein j=0 to y, wherein k=0 to z comprises the steps of:

calculating Q 0 =S 0 −S 4 ;

calculating Q 1 =S 1 −S 5 ;

calculating Q 2 =S 2 −S 6 ;

calculating Q 3 =S 3 −S 7 ;

calculating I 0 =( S 0 +S 4 )−( S 2 +S 6 ); and

calculating I 1 =( S 1 +S 5 )−( S 3 +S 7 ).

8. The method of claim 6 , wherein x=15, y=7, z=3, wherein the step of calculating the set of quadrature terms Q j and the set of in-phase terms I k through employment of the one or more of the plurality of samples S n , wherein j=0 to y, wherein k=0 to z comprises the steps of:

calculating Q 0 =S 0 −S 8 ;

calculating Q 1 =S 1 −S 9 ;

calculating Q 2 =S 2 −S 10 ;

calculating Q 3 =S 3 −S 11 ;

calculating Q 4 =S 4 −S 12 ;

calculating Q 5 =S 5 −S 13 ;

calculating Q 6 =S 6 −S 14 ;

calculating Q 7 =S 7 −S 15 ;

calculating I 0 =( S 0 +S 8 )−( S 4 +S 12 );

calculating I 1 =( S 1 +S 9 )−( S 5 +S 13 );

calculating I 2 =( S 2 +S 10 )−( S 6 +S 14 ); and

calculating I 3 =( S 3 +S 11 )−( S 7 +S 15 ).

9. The method of claim 6 , wherein the step of calculating the phase angle φ through employment of the one or more quadrature terms and the one or more in-phase terms comprises the steps of:

calculating a quadrature term Q from a magnitude of the quadrature term Q s and one or more quadrature terms of the set of quadrature terms Q j ;

calculating an in-phase term I from a magnitude of the in-phase term I s and one or more in-phase terms of the set of in-phase terms I k ; and

calculating the phase angle φ of the output signal from an arctangent of a quantity Q/I.

10. An apparatus, a sensor array that employs a parameter to induce a time-varying phase angle φ on an optical signal that comprises a phase generated carrier with a demodulation phase offset β, the apparatus comprising:

a filter component that filters an output signal from the sensor array to create a filtered signal; and

a processor component that employs the filtered signal to calculate the phase angle φ substantially independent from the demodulation phase offset β.

11. The apparatus of claim 10 , wherein the processor component obtains a plurality of samples S n of the filtered signal, wherein n=0 to x;

wherein the processor component employs one or more of the plurality of samples S n to calculate the phase angle φ substantially independent from the demodulation phase offset β.

12. The apparatus of claim 11 , wherein the processor component employs one or more of the plurality of samples S n of the output signal to calculate one or more quadrature terms and one or more in-phase terms, wherein one or more of the one or more quadrature terms and one or more of the one or more in-phase terms are substantially independent from the demodulation phase offset β of the phase generated carrier;

wherein the processor component employs the one or more quadrature terms and the one or more in-phase terms to calculate the phase angle φ.

13. The apparatus of claim 11 , wherein the output signal comprises a period T pulse , wherein the processor component obtains the plurality of samples S n within a period T s , wherein T s is less than or equal to T pulse .

14. The apparatus of claim 13 , wherein the processor component employs one or more of the plurality of samples S n of the output signal to calculate one or more quadrature terms and one or more in-phase terms, wherein one or more of the one or more quadrature terms and one or more of the one or more in-phase terms are substantially independent from the demodulation phase offset β of the phase generated carrier;

wherein the processor component employs the one or more quadrature terms and the one or more in-phase terms to calculate the phase angle φ.

15. The apparatus of claim 14 , wherein the one or more of the one or more quadrature terms comprise a quadrature term Q s , wherein the one or more of the one or more in-phase terms comprise an in-phase term I s ;

wherein the processor component employs one or more of the plurality of samples S n , the quadrature term Q s , and the in-phase term I s to calculate the phase angle φ.

16. The apparatus of claim 15 , wherein the processor component employs the plurality of samples S n to calculate a set of quadrature terms Q j and a set of in-phase terms I k , wherein j=0 to y, wherein k=0 to z;

wherein the processor component employs the set of quadrature terms Q j and the set of in-phase terms I k to calculate the quadrature term Q s , and the in-phase term I s .

17. The apparatus of claim 16 , wherein the processor component calculates a constant C 1 , wherein the processor component calculates:

∑

⁢

;