Source: http://www.google.com/patents/US7043102?dq=%E2%80%9Cconfiguration+using+structure+and+rules+to+provide+a+user+interface.%E2%80%9D&ei=ANUpTrT8BsTm0QHVpJX-Cg
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Patent US7043102 - Optical fiber interferosensor, signal-processing system for optical fiber ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA low coherence light of wide range is fed into a Fabry-Perot load cell having a measured clearance varied in response to physical quantities such as force and pressure or the like to modulate its wavelength. The measured clearance is calculated by the variable gap Fabry-Perot interferometer and the...http://www.google.com/patents/US7043102?utm_source=gb-gplus-sharePatent US7043102 - Optical fiber interferosensor, signal-processing system for optical fiber interferosensor and recording mediumAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7043102 B2Publication typeGrantApplication numberUS 09/955,155Publication dateMay 9, 2006Filing dateSep 19, 2001Priority dateSep 20, 2000Fee statusPaidAlso published asDE10145912A1, DE10145912B4, US20030039428Publication number09955155, 955155, US 7043102 B2, US 7043102B2, US-B2-7043102, US7043102 B2, US7043102B2InventorsKoji Okamoto, Koji HiroseOriginal AssigneeKyowa Electronic Instruments Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (4), Referenced by (25), Classifications (16), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetOptical fiber interferosensor, signal-processing system for optical fiber interferosensor and recording medium
US 7043102 B2Abstract
A low coherence light of wide range is fed into a Fabry-Perot load cell having a measured clearance varied in response to physical quantities such as force and pressure or the like to modulate its wavelength. The measured clearance is calculated by the variable gap Fabry-Perot interferometer and the signal processing part in the optical sensor and further the physical quantities are measured.
an optical correlation signal extracting means for extracting a desired optical correlation signal from the output signal in time-series of said linear image sensor; a non-required component removing and processing means for removing a high frequency non-required component and a low frequency non-required component of the output of said optical correlation signal extracting means; a phase shift processing means for shifting by 90° a phase of the output of said non-required component removing and processing means; an envelope calculating means for attaining an envelope component of the output of said non-required component removing and processing means in reference to an output of said non-required component removing and processing means and an output of said phase shift processing means with its phase being shifted by 90°; and a peak position calculating means for differentiating an output of said envelope calculating means and attaining a zero-cross point where said differentiated value may cross with a level zero. 12. An optical fiber interference sensor according to claim 11, wherein,
said non-required component removing and processing means is comprised of; a low-pass filter processing means for removing a high frequency noise component from an output of said optical correlation signal extracting means by a low-pass filter processing; and a least square processing means for removing a low frequency non-required component from an output of said low pass filter processing means by a least square fitting method. 14. An optical fiber interference sensor according to claim 11, wherein said phase shift processing means includes a phase shift processing means for shifting a phase of an output of said non-required component removing and processing means by 90° by performing a Hilbert transform.
means for calculating a square root of square sum to attain an envelope component of an output of said non-required component removing and processing means by calculating a square root of square sum of an output of said non-required component removing and processing means and an output of said phase shift processing means with its phase being shifted by 90°; and a high frequency removing means for removing a high frequency non-required component of output of said means for calculating a square root of square sum by a low-pass filter processing. 16. An optical fiber interference sensor according to claim 11, wherein said peak position calculating means includes;
an optical correlation signal extracting means for extracting a desired optical correlation signal from the output signal in time-series of said linear image sensor; a non-required component removing and processing means for removing a high frequency non-required component and a low frequency non-required component of an output of said optical correlation signal extracting means; a phase shift processing means for shifting by 90° a phase of an output of said non-required component removing and processing means; an envelope calculating means for attaining an envelope component of output of said non-required component removing and processing means in reference to an output of said non-required component removing and processing means and an output of said phase shift processing means with its phase being shifted by 90°; and a peak position calculating means for differentiating an output of said envelope calculating means to attain a zero-cross point where said differentiated value crosses with a level zero.
The low coherence interference process is a well-known technology in a classical optics as already described in M. Born and E. Wolf's “Principles of Optics, 6th edition” (Pergamon Press) (Oxford, London, New York, 1980). However, a true value of this process is realized under application to the optical fiber sensor.
In addition, a system in which the low coherence interference process is applied to the optical fiber sensor is already described in a total report such as D. A. Jackson's “Monomode optical fiber interferometers for precision measurement”, J.Phys.E: Sci. Instrum., Vol. 18 981-1001 (1985).
As the prior art Fabry-Perot type optical fiber interferosensor applied with a low coherence light source, an optical fiber Fabry-Perot type interference strain sensor system is already indicated in the gazette of U.S. Pat. No. 5,392,117 (issued on Feb. 21, 1995; Belleville et al. “Fabry-Perot optical sensing device for measuring a physical parameter” and the gazette of U.S. Pat. No. 5,202,939 in which a signal light from a sensor having modulated in wavelength is collected in a spatial linear manner at the sensor, the light signal is guided to a Fizeau interferometer, an optical correlation is generated at the Fizeau interferometer to demodulate the light signal and this is detected by a linear image sensor.
The modulated in wavelength optical wave reflected at the sensor part 100 and returned back is divided by a [2×2] coupler 107 and is transmitted to an optical signal demodulation processing part 108.
This optical intensity signal is detected by a linear image sensor 108 c comprised of CCD (Capacitance-Coupled Device) or the like, for example, and a distance from a wedge end of a location where its optical intensity becomes minimum [Lmin(d)|d=G] is calculated, as shown in FIG. 29, thereby an absolute measurement of the clearance size G at the gap of the sensor part 100 can be carried out with [G=Lmin(G)·tan(g)] being applied. A strain ε can be expressed as ɛ = { L min [ G ( ɛ ) ] - L min [ G ( 0 ) } · tan ( γ ) L G ( 1 ) In this system, when a high coherent light source is used as a light source, the optical correlation signal is dispersed to cause either a minimum or maximum position sensing to become difficult.
The present invention has been invented in view of the foregoing circumstances, and it is an object of the present invention to provide an optical fiber interference sensor, a signal processing system for the optical fiber interference sensor and a recording medium in which influence caused by non-required signal components such as fluctuation and noise of the low frequency can be removed or restricted effectively by a simple configuration and the high precision result of measurement can be attained by an easy or convenient adjustment of the optical system or by an easy signal processing of the sensing signal.
Referring now to the drawings, the optical fiber interference sensor of the present invention will be described in detail as follows in reference to its preferred embodiments.
The optical reflection type Fabry-Perot optical fiber interference load cell acting as an optical fiber interference sensor in accordance with the present invention shown in FIG. 1 is comprised of a light source 1, a first optical fiber 2, a [2×2] coupler 3, a second optical fiber 4, a third optical fiber 5, a Fabry-Perot load cell 6, a fourth optical fiber 7, a variable gap type Fabry-Perot interferometer 8, an optical sensor 9, an optical power meter 10, an A/D (analog-digital) converter 11 and a signal processing part 12.
In FIG. 1, the light source 1 may not generate a high coherence light such as a laser or the like, but generate a wide range low coherence light such as white light and the like. As this light source 1, a tungsten halogen lamp and a white LED or the like, for example, can be used. The first optical fiber 2 is an optical fiber for use in guiding the low coherence light from the light source 1 to the [2×2] coupler 3.
The [2×2] coupler 3 has first to fourth ports, wherein light incident from the first port is branched and outputted to the second port and the third port with an intensity ratio of 50%/50%. In addition, the [2×2] coupler 3 may output light incident from the third port to the fourth port. Although the first optical fiber 2 is connected to the first port of the [2×2] coupler 3 as described above, each of the second optical fiber 4, the third optical fiber 5 and the fourth optical fiber 7 is connected to each of the second port, the third port and the fourth port. Since the output light from the second port of the [2×2] coupler 3 is proportional to the input light of the first port, the output of the second port is fed back to a control part (not shown) of the light source 1, for example, through the second optical fiber 4, and is utilized in controlling of light emission of the light source 1. The output light at the third port of the [2×2] coupler 3 is guided to the Fabry-Perot load cell 6 through the third optical fiber 5. The output light corresponding to a measured clearance in the Fabry-Perot load cell 6 is guided to the [2×2] coupler 3 through the third optical fiber 5. The [2×2] coupler 3 guides the output light of the Fabry-Perot load cell 6 guided to the third port through the third optical fiber 5 to a variable gap Fabry-Perot interferometer 8 at a signal demodulation part through the fourth optical fiber 7 connected to the fourth port.
The Fabry-Perot load cell 6 is a load cell having a Fabry-Perot interferometer acting as a Fabry-Perot optical interference sensor assembled therein, wherein it has a base 6 a, a diaphragm 6 b and a load feeding part 6 c. The other end of the third optical fiber 5 having one end connected to the third port of the [2×2] coupler 3 is fixed by an adhesion and the like to the base of the Fabry-Perot load cell 6, and a partial reflection film is formed at the extremity end surface of the third optical fiber 5. The Fabry-Perot load cell 6 has a partial reflection film formed to be faced against the end surface of the third optical fiber 5 where the partial reflection film is formed, and the diaphragm 6 b deformed by a load of weight and the like is arranged with a predetermined gap, i.e. the measured clearance being present. The partial reflection film formed at the portion of the diaphragm 6 b facing against the end surface of the optical fiber is a thin film, for example, that may reflect a part of the incident light and absorb the residual part of it. The Fabry-Perot interferometer described above is constituted by the gap portion facing while forming the aforesaid predetermined gap clearances.
When a load is applied to the Fabry-Perot load cell 6, the diaphragm 6 b is deformed to cause a gap clearance size to be changed. The load can be calculated by sensing the variation in clearance size of the gap. That is, light guided by the third optical fiber 5 to the Fabry-Perot load cell 6 of the Fabry-Perot interferometer is multi-reflected at the gap formed by the opposing partial reflection surfaces and it is modulated in its wavelength in response to the clearance size of the gap. The optical wave modulated in its wavelength, i.e. the light signal is reflected at the sensor of the Fabry-Perot load cell 6, returns back to the third optical fiber 5 and is inputted from the third port to the [2×2] coupler 3.
The fourth optical fiber 7 may guide the wavelength-modulated optical signal inputted into the [2×2] coupler 3 from the Fabry-Perot load cell 6 to the variable gap type Fabry-Perot interferometer 8 at the optical signal demodulation part from the fourth port of the [2×2] coupler 3.
Referring to FIG. 3, there will be described more practically the signal processing method for sensing the minimum optical correlation signal position in reference to the optical correlation signal output practical data of the optical power meter 10. In the following description, the output signal data is meant by the output signal data after it is A/D converted with the A/D converter 13, wherein the step Nos. such as “S1” and “S2” or the like denote a processing step indicated by applying the same symbol to FIG. 3.
S LCOR(n)=S SIG(n)−K·S BACK(n) (2) In this preferred embodiment, since the variable gap Fabry-Perot interferometer is used at the optical signal demodulation part, it is not necessary to condense the light spatially in a linear form as found in a wedge type Fabry-Perot interferometer (a Fizeau interferometer) and a background signal noise is relatively low. In view of this fact, the least square multinomial fitting was used for removing the background signal in this preferred embodiment. Further, in the case of performing this background signal removing processing, a high pass filter (HPF) processing may be used in place of the least square fitting.
In this case, this least square fitting is used for removing the background signal from the measured data. The optical correlation signal to be extracted is a component equally vibrated in an upward or downward direction in regard to a predetermined reference value. Accordingly, in the case that the background signal is overlapped on the optical correlation signal, a curved line expressing the background signal is calculated by the least square fitting to pick up a difference between it and the original signal, resulting in that an appropriate optical correlation signal can be attained. That is, the background signal SBACK,FIT(n) is estimated by the least square multinomial fitting. This SBACK,FIT(n) is a curved line expressing a background signal calculated in reference to the measured data under application of the least square fitting, and a curve equation (a multinomial) such as an equation (3), for example, is used. S BACK , FIT ( x ) = A 0 + A 1 · x + A 2 · x 2 + … + A 10 · x 9 + A 11 · x 10 ( 3 ) where, Am (m=0, 1, . . . , 10) is a coefficient of a curved line equation and it is calculated in reference to the measured data under application of the least square method. Then, SLCOR(n) was calculated under an assumption that K·SBACK(n)=SBACK,FIT(n) is applied in the equation (2).
As the smoothing processing, various kinds of methods can be applied, although a smoothing differentiating method by Savitzky and Golay, for example, can be applied. In this case, a zero position of the smoothing differentiated signal waveform becomes an extreme value. Its details are described in a document entitled “Waveform Data Processing for Scientific Measurement” edited by Shigeo Minami, CQ Publishing Co., Ltd. (1986).
In FIG. 10, the light source 1, the first optical fiber 2, [2×2] coupler 3, the second optical fiber 4, the third optical fiber 5, the Fabry-Perot load cell 6 and the fourth optical fiber 7 are similar to those shown in FIG. 1, and in place of the configuration of the signal demodulating part comprised of the variable gap Fabry-Perot interferometer 8, optical sensor 9 and optical power meter 10, there is provided a signal demodulating part comprised of a collimate lens 21, focusing lens 22, Fizeau interferometer 23, linear image sensor 24 and image sensor control part 25.
That is, the fourth optical fiber 7 guides the modulated in wavelength optical signal inputted from the Fabry-Perot load cell 6 to [2×2] coupler 3, to the collimate lens 21 at the optical signal demodulation part from the fourth port of the [2×2] coupler 3 and causes it to be incident.
In FIG. 11, the light source 1, the first optical fiber 2, the [2×2] coupler 3, the second optical fiber 4, the third optical fiber 5, the Fabry-Perot load cell 6, the fourth optical fiber 7 and the optical power meter 10 are similar to those shown in FIG. 1 and there is provided a Mickelson interferometer 31 in place of the configuration comprised of variable gap Fabry-Perot interferometer 8 and optical sensor 9 as shown in FIG. 1.
The signal processing part 12 processes the signal A/D converted by the A/D converter 11 to attain a result of measurement. The signal processing part 12 extracts the desired optical correlation signal from the signal of time-series attained from the optical sensor 9 through the image sensor control part 10, removes the high frequency noise component of the optical correlation signal through a low pass filter processing, removes the low frequency non-required component through a least square fitting method, removes the high frequency non-required component and the low frequency non-required component, converts its output by a Hilbert transform and shifts its phase by 90°. A square root of square sum of a signal having the non-required component removed and an output having its phase shifted by 90° is calculated in reference to a signal having the high frequency non-required component and the low frequency non-required component removed and a signal shifted by 90° by a Hilbert transform, an envelope component attained by removing the high frequency non-required component by low-pass filter processing is differentiated to attain a zero-cross point where the differentiated value crosses with the level zero.
Then, referring to FIGS. 12 and 13, there will be described more practically the signal processing for detecting the peak position of the optical correlation signal from the output signal practical data of the optical sensor 9 using a CCD. In the following description, the output signal data of the optical sensor 9 using a CCD indicates the output signal data after A/D converted by the A/D converter 11, wherein each of the step Nos. “S1” and “S2” or the like indicates a processing step denoted by the same reference symbols in FIGS. 12 and 13, respectively.
S LCOR(n)=S SIG(n)−K·S BACK(n) (4) In FIG. 17 is indicated a variation of the optical correlation signal SLCOR(n) extracted by the aforesaid method from the signal output practical data of the optical sensor 9 when the measurement is performed under application of the load weight as found in FIG. 15. It is apparent that the position of the optical correlation signal is changed in response to a size of the load. In this case, the coefficient K is adjusted in compliance with a level of output signal when measured.
S FIT(x)=A 0 +A 1 ·x+A 2 ·x 2 +. . . +A 10 ·x 9 +A 11 ·x 10 (6) where, Am (m=0, 1, . . . , 10) denotes a coefficient of a curved line and this is calculated by a least square method in reference to measured data.
<Step S4: Phase Shift by 90° of a Waveform by a Hilbert Transform>
A signal [SDC(n)] having a low frequency component removed at the step S3 is processed with a Hilbert transform to generate a signal with its phase being shifted by 90° indicated by the equation (7).
Upon performing the Hilbert transform Ĥ[SDC(n)], its real number part can attain a signal similar to its original waveform SDC(n) and its imaginary number part can attain a signal with its phase being shifted by 90° in regard to the signal at the real number part. In FIG. 21 are indicated a waveform of an original time-series signal [SDC(n)] and a waveform of a signal [S90(n)] with the former one being Hilbert transformed.
This method is carried out under an assumption that a biasing portion and a frequency component corresponding to the correlation signal are completely separated, i.e. no fluctuation of low frequency is present. Due to this fact, it becomes necessary that “a removal of low frequency component” at the aforesaid step S3 is performed as a pre-treatment.
A signal [SENV(n)] similar to an envelope of the original signal [SDC(n)] is generated from a signal [SDC(n)] with its low frequency component being removed and a signal [S90(n)] having the former signal transformed in a Hilbert transform which are attained at the steps S3 and S4, respectively. This process is expressed as follows in an equation (8); S ENV ( n ) = [ S D C ( n ) ] 2 + [ S 90 ( n ) ] 2 ( 8 ) FIG. 22 shows each of a signal [SDC(n)] having a low frequency component removed, a signal [S90(n)] having the former signal transformed by a Hilbert transform and a signal [SENV(n)] similar to the envelope calculated by the equation (8), respectively.
Then, a straight line image of principle in which an envelope is detected by the Hilbert transform will be described in reference to a response of a vibration system with a degree of freedom 1 in attenuation. This method is already described in N. Thrane, et. al.: “Practical use of the “Hilbert transform”, Application Note, B&K, Denmark, B00437-11, for example. In the following description, the present invention will be described in reference to this document.
h(t)=A·exp(−α·t)·sin(ωo ·t) (9) When the equation (9) is transformed by a Hilbert transform to Ĥ [h(t)], the real number of the transformed waveform (t) is changed into the original waveform h(t) and an imaginary number part is changed into a waveform h (t) (a left lower waveform in FIG. 23) with its phase being shifted by 90° in respect to the original waveform. That is, this equation may become an equation (10); H ^ [ h ( t ) ] = h ( t ) = h ( t ) + j · h ~ ( t ) ( 10 ) where, h(t) and {tilde over (h)}(t) are defined as indicated in the equations (11) and (12);
h(t)=A·exp(−α·t)·sin(ωo t) (11) {tilde over (h)}(t)=A·exp(−α·t)·cos(ωo t) (12) Accordingly, the envelope of h(t) is calculated as indicated in the equations (13) and (14) from an absolute value | (t)| of Ĥ [h(t)]= (t).  h τ ( t )  = [ h ( t ) ] 2 + [ h ~ ( t ) ] 2 ( 13 )  h τ ( t )  = A · exp ( - α · t ) ( 14 ) The waveform of the envelope shown in the equation (14) corresponds to the right side waveform of FIG. 23.
Also in FIG. 1, the light source 1, the first optical fiber 2, the [2×2] coupler 3, the second optical fiber 4, the third optical fiber 5, the Fabry-Perot load cell 6 and the fourth optical fiber 7 are similar to that shown in FIG. 10, wherein there are provided the variable gap type Fabry-Perot interferometer 8 and the optical sensor 9, and the optical power meter 10 similar to that shown in FIG. 11 in place of the configuration of the signal demodulating part comprised of the collimate lens 21, the focusing lens 22, the Fizeau interferometer 23, the linear image sensor 24 and the image sensor control part 25 shown in FIG. 10.
As described above, in accordance with the present invention, it is possible to provide an optical fiber interference sensor, a signal processing system for the optical fiber interference sensor and a recording medium in which influences caused by some non-required signal components such as a low frequency fluctuation and noises are effectively restricted by a simple configuration and a high precision result of measurement can be attained by a convenient adjustment of an optical system and a simple signal processing for the sensing signal.
In addition, in accordance with the optical fiber interference sensor of the present invention, there is provided a Fabry-Perot optical fiber interference sensor having a sensor part having opposed surfaces formed as parallel planes to each other in a measured clearance varied in response to physical quantities such as force, strain, pressure and temperature and the like, having a partial reflection mirror or an end surface of one optical fiber formed with a partial reflection mirror arranged in one surface side of said opposed surfaces, and having an end surface of the other optical fiber formed with a partial reflection mirror arranged in the other surface side of said opposed surfaces, in which a light of low coherence light source is guided to said the other optical fiber, any one of a reflected light and a transmission light modulated in wavelength in correspondence with said clearance size through multiple reflection at said measured clearance is guided by the optical fiber, the light is condensed linearly in a uniform optical intensity distribution, radiated onto a linear image sensor through a Fizeau interferometer, a maximum optical intensity position at said linear image sensor is detected from an output of said linear image sensor to attain said measured clearance, wherein a desired optical correlation signal is extracted from the output signal in time-series of said linear image sensor by an optical correlation signal extracting means; a high frequency non-required component and a low frequency non-required component are removed by a non-required component removing and processing means; an envelope component is attained by an envelope calculating means in response to the signal and signal shifted by 90°.with a phase shift processing means; and at the same time, the envelope component is differentiated by a peak position calculation means, a zero-cross point where said differentiated value crosses with the level zero is attained, a peak position indicating the gap clearance size corresponding to said physical quantities is calculated, thereby influence caused by fluctuation of the low frequency and non-required signal components such as noise can be removed or restricted effectively by a simple configuration and a high precision result of measurement can be attained also by an easy adjustment of the optical system.
a low-pass filter processing means for removing a high frequency noise component from an output of said optical correlation signal extracting means by a low-pass filter processing; and a least square processing means for removing a low frequency non-required component from said low pass filter processing means by a least square fitting method, thereby in particular, high frequency non-required and low frequency components can be removed or restricted effectively. In accordance with the optical fiber interference sensor of the present invention, said phase shift processing means includes a phase shift processing means for shifting a phase of an output of said non-required component removing and processing means by 90° by performing a Hilbert transform against an output of said non-required component removing and processing means.
means for calculating a square root of square sum to attain an envelope component of an output of said non-required component removing and processing means by calculating a square root of square sum of an output of said non-required component removing and processing means and an non-required component removing and processing means and an output of a phase shift processing means with its phase being shifted by 90°, thereby an envelope component of the output of said non-required component removing and processing means; and a high frequency removing means for removing a high frequency non-required component of output of said means for calculating a square root of square sum by a low-pass filter processing, thereby in particular, the non-required component can be removed or restricted effectively and a high precision measurement can be realized. In accordance with the optical fiber interference sensor, said peak position calculating means includes;
a smoothing and differentiating processing means for smoothing and differentiating processing an output of said envelope calculating means in response to a multinomial adaptation smoothing method; and a zero-cross point calculating means for attaining a zero cross-point where an output of said smoothing and differentiating processing means crosses with a level zero, thereby in particular, the non-required components can be removed or restricted effectively and a high precision measurement can be measured. In accordance with the signal processing system of an optical fiber interference sensor of the present invention, there is provided a signal processing system of a Fabry-Perot optical fiber interference sensor having a sensor part having opposed surfaces formed as parallel planes to each other in a measured clearance, having a partial reflection mirror or an end surface of one optical fiber formed with a partial reflection mirror arranged in one surface side of said opposed surfaces, and having an end surface of the other optical fiber formed with a partial reflection mirror arranged in the other surface side of said opposed surfaces, in which a light of low coherence light source is guided to said the other optical fiber, one of a reflected light and a transmission light modulated in wavelength in correspondence with a clearance size of said measured clearance through multiple reflection at said measured clearance is guided by the optical fiber, light is condensed in a linear manner under a uniform optical intensity distribution, radiated onto a linear image sensor through a Fizeau interferometer to measure said measured clearance, a desired optical correlation signal is extracted from the output signal in time-series of said linear image sensor by an optical correlation signal extracting means; a high frequency non-required component and a low frequency non-required component of an output of said optical correlation signal extracting means are removed by the non-required component removing and processing means; a phase of output of said non-required component removing and processing means is shifted by 90° by the phase shift processing means, the envelope component of output of said non-required component removing and processing means is attained by the envelope calculating means in response to an output of said non-required component removing and processing means and an output of the phase shift processing means with its phase being shift by 90 Åã, an output of said envelope calculating means is differentiated by a peak position calculating means to attain a zero-cross point where the differentiated value may cross with the level zero, thereby in particular, a high precision result of measurement can be attained even with a simple configuration.
a low-pass filter processing means for removing a high frequency noise component from an output of said optical correlation signal extracting means through the low-pass filter processing; and a least square processing means for removing a low frequency non-required component from a output of said optical correlation signal extracting means by a least square fitting method, thereby in particular, both a high frequency non-required component and a low frequency non-required component can be effectively removed or restricted. In addition, in accordance with the signal processing system for said optical fiber interference sensor, said phase shift processing means is comprised of a phase shift processing means for shifting its phase by 90 Åãby performing a Hilbert transform against an output of said non-required component removing and processing means, thereby in particular, the non-required component can be removed or restricted more effectively.
means for calculating a square root of square sum to attain an envelope component of an output of said non-calculating a square root of square sum of an output of said non-required component removing and processing means and an output of a phase shift and processing means with its phase being shifted by 90°; and a high frequency removing means for removing a high frequency non-required component of an output of said means for calculating a square root of square sum by the low pass filter processing, thereby in particular the non-required component can be effectively removed or restricted and a high precision measurement can be realized. Further, in accordance with the signal processing system for said optical fiber interference sensor,
an optical correlation signal extracting means for extracting a desired optical correlation signal from an output signal in time-series of said linear image sensor; a non-required component removing and processing means for removing a high frequency non-required component and a low frequency non-required component of an output of said optical correlation signal extracting means; a phase shift processing means for shifting by 90° a phase of an output of said non-required component removing and processing means; an envelope calculating means for attaining an envelope component of the output of said non-required component removing and processing means in response to an output of said non-required component removing and processing means and an output of a phase shift processing means with its phase being shifted by 90°; and a peak position calculating means for differentiating an output of said envelope calculating means to attain a zero-cross point where said differentiated value may cross with a level zero; thereby in particular, as for the signal processing by the optical fiber interference sensor, a high precision result of measurement can be attained even under application of a simple configuration of the measurement system. Although the present invention has been described with reference to the preferred embodiments, it is apparent that the present invention is not limited to the aforesaid preferred embodiments, but various modifications can be attained without departing from its scope.
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