JPH1123215A - Detection-signal processor in optical-frequency-region-reflection measuring method - Google Patents
Detection-signal processor in optical-frequency-region-reflection measuring methodInfo
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- JPH1123215A JPH1123215A JP9173473A JP17347397A JPH1123215A JP H1123215 A JPH1123215 A JP H1123215A JP 9173473 A JP9173473 A JP 9173473A JP 17347397 A JP17347397 A JP 17347397A JP H1123215 A JPH1123215 A JP H1123215A
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- beat
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- optical
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、連続的な光周波数
掃引が可能な光源を利用した計測原理に基づく距離また
は多重位置計測（ＦＭＣＷ法：Frequency Modulation C
ontinous Wave,ＯＦＤＲ法：Optical Frequency Domain
Reflectometory ，総称して以下、「光周波数領域反射
測定法」と呼ぶ）全般に利用される検出信号処理装置に
関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance or multiple position measurement (FMCW method: Frequency Modulation C) based on a measurement principle using a light source capable of continuous optical frequency sweep.
ontinous Wave, OFDR method: Optical Frequency Domain
Reflectometory, hereinafter collectively referred to as “optical frequency domain reflection measurement method”).
【０００２】[0002]
【従来の技術】光周波数領域反射測定法は、時間的に線
形な繰り返し光周波数掃引可能な光源から出力される光
ＦＭ（周波数変調）出力が干渉計によって参照光と物体
光（測定光）とに二分され、再び反射帰還し干渉したと
きに生じるお互い（参照光と物体光）の光路時間差τが
もたらす光周波数差（ビート周波数）を求めることで光
路差２ΔＬ＝τｃ（ｃ：光速）つまり空間的距離を算出
するものである。このような時間的な繰り返し光周波数
掃引の発生からビート周波数を求め、そこから空間的距
離を求めるまでの構成を本発明の一例を示す図３を利用
して示す。すなわち、本計測法の基本装置構成を図３を
利用して示し、図３の系で得られるビート信号の検出・
信号解析処理の原理および動作を図４に示す。2. Description of the Related Art In an optical frequency domain reflection measurement method, an optical FM (frequency modulation) output from a light source capable of repetitive optical frequency sweeping in time is converted into a reference light and an object light (measurement light) by an interferometer. The optical frequency difference (beat frequency) caused by the optical path time difference τ between each other (reference light and object light), which is generated when the reflected light returns and interferes with each other, is obtained. This is to calculate the target distance. The configuration from the occurrence of such a temporally repeated optical frequency sweep to the determination of the beat frequency and the determination of the spatial distance therefrom will be described with reference to FIG. 3 showing an example of the present invention. That is, the basic device configuration of the present measurement method is shown using FIG. 3, and the detection and detection of the beat signal obtained by the system of FIG.
FIG. 4 shows the principle and operation of the signal analysis processing.
【０００３】図３において、光源に半導体レーザ２を用
いた例を取り上げて説明する。ただし光源は半導体レー
ザに限らず、波長可変可能な光源ならばそれに制約され
ることはない。発振器１からの注入電流にて線形変調さ
れた半導体レーザ２のレーザ光は図４の波形２１や２２
のような光周波数時間変化をする光ＦＭ波３を出力す
る。この場合、鋸波を例にとったが、三角波でも同様な
ことがいえる。光ＦＭ出力３はビームスプリッタ４で参
照光５と物体光（測定光）７に分割される。参照光５は
ビームスプリッタ４から距離Ｌ1 離れた参照ミラー６に
反射され再び折り返しされる。そして、物体光７も同様
に距離Ｌ2 だけ離れた測定対象８に反射され再び折り返
しされる。この場合、距離の差ΔＬは｜Ｌ1 −Ｌ2 ｜と
なる。この結果、それぞれの反射光５，７はビームスプ
リッタ４によって重ね合せられ干渉光９となる。このと
きの反射光５，７の光ＦＭ波の挙動を図４の（ａ）に示
す。干渉光９は光ＦＭ波２１と２２が参照ミラー６と測
定対象８との光路差の往復分２ΔＬに相当する光遅延時
間τ（＝２ΔＬ／Ｃ）だけずれて重ね合せられる。する
と、変調周期１／ｆm （ｆm は光周波数）のほとんど全
領域時間にわたり周波数差ｆb （＝２Δνｆm ・ΔＬ／
Ｃ）が発生する。これがビート周波数である。その周波
数差ｆb の時間変化を表わしたのが図４（ａ）の中段の
図である。この図から低周波ビート２７と高周波ビート
２８の２種類のビート周波数が発生するが高周波側のビ
ート周波数２８はτの時間間隔でしか発生せず、しかも
τ≪１／ｆm の関係からほとんどそれは無視することが
できる。よって、ここで一般的に呼んでいるビート周波
数は低周波側のビート周波数２７である。さて、図３で
の干渉光９は光検出器１０によって自乗検波され電気信
号波形（時間波形）となって検出される。その波形は図
４（ａ）の下段のビート信号強度波形として示した。こ
の波形は変調周期ごとに低周波側のビート信号強度時間
波形２９と、変調の折り返し部分のところでの高周波側
のビート信号強度時間波形３０とで構成されている。た
だし、実際はその高周波側のビート信号波形３０は光Ｆ
Ｍ波の非線形性が極端に大きくかつ非常にビート周波数
が高く、通常の光検出器の帯域では検出することができ
ない領域であるため、実際の観測では、その部分は低周
波側のビート信号の不連続部分として検出される。これ
らのビート信号強度時間波形２９，３０を例えばＦＦＴ
（高速フ−リエ変換）といった周波数解析手法を用いて
ビート周波数スペクトルを求めたのが、図４（ｂ）のｆ
b1の強度波形３２、ｆb2の強度波形３３である。強度波
形３２の場合はそのスペクトルの最大値における周波数
は求めることができ、かつ時間的に安定性が得られる。Referring to FIG. 3, an example in which a semiconductor laser 2 is used as a light source will be described. However, the light source is not limited to a semiconductor laser, and is not limited to a light source whose wavelength can be varied. The laser light of the semiconductor laser 2 linearly modulated by the injection current from the oscillator 1 has waveforms 21 and 22 in FIG.
An optical FM wave 3 having an optical frequency change over time is output. In this case, a sawtooth wave is taken as an example, but the same can be said for a triangular wave. The light FM output 3 is split by a beam splitter 4 into reference light 5 and object light (measurement light) 7. Reference light 5 is reflected on the reference mirror 6 spaced a distance L 1 from the beam splitter 4 is folded again. Even object beam 7 is reflected on the measurement object 8 at a distance of similarly a distance L 2 is folded again. In this case, the distance difference ΔL is | L 1 −L 2 |. As a result, the respective reflected lights 5 and 7 are superposed by the beam splitter 4 to become interference light 9. The behavior of the light FM waves of the reflected lights 5 and 7 at this time is shown in FIG. The interference light 9 is superimposed such that the optical FM waves 21 and 22 are shifted by an optical delay time τ (= 2ΔL / C) corresponding to the reciprocation 2ΔL of the optical path difference between the reference mirror 6 and the measurement target 8. Then, the modulation period 1 / f m (f m is the optical frequency) frequency difference f b over almost the entire region time (= 2Δνf m · ΔL /
C) occurs. This is the beat frequency. As was represents the time variation of the frequency difference f b is the middle part of FIG. 4 (a). The two beat the frequency is generated higher frequency side of the beat frequency 28 from FIG low frequency beats 27 and the high frequency beat 28 does not occur only at time intervals of tau, yet little it from the relationship τ«1 / f m Can be ignored. Therefore, the beat frequency generally called here is the beat frequency 27 on the low frequency side. The interference light 9 in FIG. 3 is square-detected by the photodetector 10 and detected as an electric signal waveform (time waveform). The waveform is shown as a beat signal intensity waveform in the lower part of FIG. This waveform is composed of a beat signal intensity time waveform 29 on the low frequency side and a beat signal intensity time waveform 30 on the high frequency side at the turn-back portion of the modulation for each modulation cycle. However, actually, the beat signal waveform 30 on the high frequency side
Since the nonlinearity of the M wave is extremely large and the beat frequency is extremely high and cannot be detected in the band of a normal photodetector, in an actual observation, that part is a beat signal of a low frequency side. Detected as discontinuous parts. These beat signal intensity time waveforms 29 and 30 are
The beat frequency spectrum obtained by using a frequency analysis method such as (fast Fourier transform) is shown in FIG.
b1 intensity waveform 32, the intensity waveform 33 of f b2. In the case of the intensity waveform 32, the frequency at the maximum value of the spectrum can be obtained, and the temporal stability can be obtained.
【０００４】[0004]
【発明が解決しようとする課題】ところがτの領域の増
大に伴った場合のビート周波数スペクトルｆb2の強度波
形３３は、チャーピング現象によりその最大値における
ビート周波数の値が明瞭に識別できずある幅でしか特定
するしかないため、そのビート周波数値をパラメータと
した計測においては計測精度・分解能の劣化が生じる。
一つの具体例としては、波長の応用においてそのτの領
域の増大は長距離になればなるほど顕著となり計測精度
の劣化を助長することになる。However, in the intensity waveform 33 of the beat frequency spectrum fb2 when the area of τ increases, the beat frequency at its maximum value cannot be clearly identified due to the chirping phenomenon. Since it is necessary to specify only the width, measurement accuracy and resolution are deteriorated in measurement using the beat frequency value as a parameter.
As one specific example, in the application of wavelength, the increase in the region of τ becomes more pronounced as the distance becomes longer, which promotes deterioration of measurement accuracy.
【０００５】本発明は、上述の問題に鑑み、光周波数領
域反射測定法において、ビート周波数のチャーピング現
象に起因する測定精度の劣化並びにビート周波数成分の
選択性の劣化（測定感度の劣化）を除くようにした検出
信号処理装置を得る。The present invention has been made in view of the above problems, and in the optical frequency domain reflection measurement method, the deterioration of measurement accuracy and the deterioration of selectivity of beat frequency components (deterioration of measurement sensitivity) due to the chirping phenomenon of the beat frequency are considered. A detection signal processing device is obtained which is excluded.
【０００６】[0006]
【課題を解決するための手段】上記目的を達成する本発
明は次の発明特定事項を有する。 （１）分岐された光信号を再び重ねて得られたビート信
号時間波形を処理する装置において、上記ビート信号時
間波形に上記光信号の周波数の繰り返し変調周期ごとに
窓関数を掛け合せ、ついでフーリエ変換してビート周波
数成分を特定する演算装置を備えたことを特徴とする。 （２）上記（１）において、Ａ／Ｄ変換器にてデジタラ
イズされたビート信号時間波形に窓関数をトリガ同期に
よりタイミングよく掛け合せ、ついでフーリエ変換する
ことで周波数スペクトラムを求める演算装置を有するこ
とを特徴とする。The present invention that achieves the above object has the following matters specifying the invention. (1) In an apparatus for processing a beat signal time waveform obtained by superimposing a branched optical signal again, the beat signal time waveform is multiplied by a window function for each repetition modulation cycle of the frequency of the optical signal, and then Fourier transformed. And an arithmetic unit for specifying the beat frequency component. (2) In the above (1), there is provided an arithmetic unit which multiplies a beat signal time waveform digitized by the A / D converter by a window function with good timing by trigger synchronization, and then obtains a frequency spectrum by Fourier transform. Features.
【０００７】光周波数領域反射測定法における理想的な
ビート信号検出は線形な繰り返し光周波数掃引が前提で
あるが、現実的にはその光周波数掃引は半導体レーザを
光源の例にとるとき、それは電流等による半導体レーザ
素子内部の熱応答特性であるため繰り返しの部分（変調
波形の立ち上がり、立ち下がり）のところで大きく応答
特性の遅れによる周波数掃引の非線形性が発生する。Ｎ
ｄ−ＹＡＧレーザといった固体レーザも共振器長の温度
変化やピエゾ素子による微小共振器長掃引でも同じよう
に応答遅れが変調周期の両端で大きく非線形性が発生す
るため、それによって得られる現実的なビート信号の周
波数成分は線スペクトルではなくある線幅（帯域幅）を
持つスペクトルとなることは、図４（ｂ）の如くであ
る。よってこれよりそのビート周波数の最大値があいま
いとなって求められる測定パラメータ（今回の例として
は長さ）に誤差が生じる。これらの非線形性の影響を除
去または緩和して測定精度を向上する技術的アプローチ
の一つとして「検出側の信号処理による非線形性の影響
の緩和」があり、この工夫改善により測定精度の向上を
測ろうとするものである。光検出器によって自乗検波さ
れ電気信号に変換されたビート信号は、電算機をつかっ
た演算処理を施すために、検出後Ａ／Ｄ変換器を通しビ
ート信号のアナログ信号をデジタイジング（デジタル信
号に変換すること）する。そのデジタル信号をパーソナ
ルコンピュータを含む電算機へ外部インターフェイス
（例えばＧＰＩＢ，ＲＳ２３２Ｃ）を介して入力する。
そして、変調（光周波数掃引の繰り返し間隔）周期のト
リガー同期を用いてタイミングよく任意の窓関数（例え
ば窓関数としては三角波関数、ハミング関数等）を掛け
合わせ演算し、電算機上でビート信号データを加工す
る。次にその加工したビート信号の時間波形を例えばＦ
ＦＴといった周波数分析手法でビート周波数スペクトル
を求め、その最大値をビート周波数と定義する。この値
を元に測定パラメータ（この場合長さ）を算出する。[0007] The ideal beat signal detection in the optical frequency domain reflection measurement method is based on linear repetitive optical frequency sweep, but in reality, the optical frequency sweep uses a semiconductor laser as an example of a light source. Because of the thermal response characteristic inside the semiconductor laser device due to the above-mentioned factors, nonlinearity of frequency sweep occurs due to a delay in response characteristic at a repetitive portion (rise and fall of the modulation waveform). N
In the case of a solid-state laser such as a d-YAG laser, the response delay is similarly large even at both ends of the modulation period due to the temperature change of the resonator length and the microcavity length sweep by the piezo element. The frequency component of the beat signal is not a line spectrum but a spectrum having a certain line width (bandwidth), as shown in FIG. 4B. Therefore, the maximum value of the beat frequency is ambiguous, and an error occurs in the measurement parameter (length in this example) obtained. One of the technical approaches to remove or mitigate the effects of these non-linearities to improve measurement accuracy is "to reduce the effects of non-linearity by signal processing on the detection side". Is to measure. The beat signal, which has been square-detected by the photodetector and converted into an electric signal, is subjected to arithmetic processing using a computer. After detection, the analog signal of the beat signal is digitized (converted into a digital signal) through an A / D converter. Conversion). The digital signal is input to a computer including a personal computer via an external interface (for example, GPIB, RS232C).
Then, an arbitrary window function (for example, a triangular wave function, a Hamming function, etc. as a window function) is multiplied and calculated with good timing using trigger synchronization of a modulation (repetition interval of optical frequency sweep) cycle, and beat signal data is calculated on a computer. To process. Next, the time waveform of the processed beat signal is represented by, for example, F
A beat frequency spectrum is obtained by a frequency analysis method such as FT, and the maximum value is defined as a beat frequency. A measurement parameter (in this case, length) is calculated based on this value.
【０００８】[0008]
【発明の実施の形態】ここで、図３，図１，図２を参照
して本発明の実施の形態の一例を述べる。図３は本発明
の一例の構成を示しており、従来技術説明にも用いた部
分は変りがないのでその説明は省略する。光周波数領域
反射測定法における干渉光９を自乗検波してビート電気
信号（時間波形）を得る光検出器１０の次段には、この
ビート電気信号をデジタイジングするためのＡ／Ｄ変換
器１１を有し、更には、所望の時間範囲にて波形を切り
出すためトリガー同期によりタイミングよくその波形に
窓関数を掛け合せ、フーリエ変換（例えば高速フーリエ
変換ＦＦＴ）によってビート周波数を抽出・特定する演
算処理を行なうパーソナルコンピュータ等の演算装置１
２を有する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an example of an embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows an example of the configuration of the present invention, and the portions used in the description of the prior art are the same, so that the description thereof will be omitted. An A / D converter 11 for digitizing the beat electric signal is provided next to a photodetector 10 that obtains a beat electric signal (time waveform) by square detection of the interference light 9 in the optical frequency domain reflection measurement method. Furthermore, in order to cut out a waveform in a desired time range, the waveform processing is multiplied by a window function with good timing by trigger synchronization, and a beat frequency is extracted and specified by Fourier transform (for example, fast Fourier transform FFT). Arithmetic device 1 such as personal computer
2
【０００９】かかる構成にあって、検出ビート信号の波
形処理につき図１にて説明し、図２にて計測処理したビ
ート信号の実測例を示す。まず図１の（ａ）に示す線形
の光周波数変調（掃引）波形４０（変調周波数ｆm 、変
調周期Ｔ＝１／ｆm ）を図３の半導体レーザ２にて発生
させる。今回、鋸波を線形波形として用いているが三角
波でもよい。図１（ａ）で示すような線形な光周波数変
調は一般的には半導体レーザ２の場合、注入電流変調に
よって発生させることができる。また、Ｎｄ−ＹＡＧレ
ーザといった固体レーザの場合でも共振器の温度変化、
共振器ミラーの微小掃引等でも実現できる。上記波形４
０から光路長差に基づく図４（ａ）下段波形と同じく光
検出器１０には図１（ｂ）のビート信号波形４１，４２
が検出される。この時のビート信号４１，４２は変調周
期Ｔの間隔で繰り返し検出される。そこで、演算装置１
２では、その変調周期Ｔに同期するようなトリガー４３
を図１（ｃ）のように発生させ図１（ｄ）の窓関数波形
（この場合は、blackman(x) 関数であるが、他には三角
hanning(x), hamming(x), bartlet(x)関数等の種類があ
る）４４をビート信号４１，４２に印加するタイミング
を図る。これにより丁度周期Ｔで図１（ｂ）と（ｄ）の
位相が等しい関係でそれぞれの波形が掛け算され、結果
図１（ｅ）の窓関数処理ビート波形４６のように整形さ
れる。そして搬送波形４５の片側搬送波成分は、図１
（ｂ）のビート信号振幅成分が一定の場合窓関数波形４
４に一致する。窓関数処理ビート波形４６の特徴は、変
調周期Ｔごとになめらかにその振幅が０に収束し連結し
ている波形である。この特性から、精度のよいビート周
波数の抽出を困難にしている図１（ｂ）の周期Ｔ部分の
ビート信号４２の影響を抑えることができ、これよりビ
ート周波数成分の抽出精度を向上することができる。In such a configuration, the waveform processing of the detected beat signal will be described with reference to FIG. 1, and an actual measurement example of the measured beat signal will be shown in FIG. First linear optical frequency modulation (sweep) waveform 40 (the modulation frequency f m, the modulation period T = 1 / f m) shown in FIG. 1 (a) to generate at the semiconductor laser 2 of FIG. This time, a sawtooth wave is used as a linear waveform, but a triangular wave may be used. Generally, linear optical frequency modulation as shown in FIG. 1A can be generated by injection current modulation in the case of the semiconductor laser 2. In addition, even in the case of a solid-state laser such as an Nd-YAG laser, temperature change of the resonator,
It can also be realized by a minute sweep of a resonator mirror or the like. Waveform 4 above
As in the lower waveform of FIG. 4A based on the optical path length difference from 0, the photodetector 10 has the beat signal waveforms 41 and 42 of FIG.
Is detected. The beat signals 41 and 42 at this time are repeatedly detected at intervals of the modulation period T. Therefore, the arithmetic unit 1
2, the trigger 43 is synchronized with the modulation period T.
Is generated as shown in FIG. 1C, and the window function waveform shown in FIG. 1D (in this case, the blackman (x) function is used.
hanning (x), hamming (x), bartlet (x) function, etc.) 44 are applied to the beat signals 41 and 42. As a result, the respective waveforms are multiplied by the relationship that the phases of FIG. 1B and FIG. 1D are equal at the period T, and the result is shaped like the window function processing beat waveform 46 of FIG. The one-sided carrier component of the carrier waveform 45 is shown in FIG.
Window function waveform 4 when beat signal amplitude component of (b) is constant
Matches 4. The feature of the window function processing beat waveform 46 is a waveform whose amplitude smoothly converges to 0 and is connected at every modulation period T. From this characteristic, it is possible to suppress the influence of the beat signal 42 in the period T portion of FIG. 1B, which makes it difficult to extract a beat frequency with high accuracy, thereby improving the extraction accuracy of the beat frequency component. it can.
【００１０】本手法を用いた実際の測定結果である図２
からその有効性を示す。図２の（ａ）は一周期Ｔ区間に
相当する実際のビート信号波形であり図１の（ｂ）のビ
ート波形４１，４２に対応する。図２（ａ）の検出ビー
ト信号波形を窓関数処理した後の波形が図２（ｂ）であ
り、図１（ｅ）の波形４６に対応する。図２の（ａ）と
（ｂ）のそれぞれのＦＦＴによる周波数スペクトラム分
布結果比較を図２の（ｃ）の５１，５２に示す。窓関数
処理後のビート周波数スペクトラム５２の半値幅は処理
していないビート周波数スペクトラム５１の半分までに
狭窄化され、同時にバックグランドノイズとのＳ／Ｎ比
５３は１０〜２０ｄＢ向上している結果となり本発明手
法の有効性を示している。FIG. 2 shows an actual measurement result using this method.
To show its effectiveness. FIG. 2A shows an actual beat signal waveform corresponding to one period T section, and corresponds to the beat waveforms 41 and 42 in FIG. 1B. FIG. 2B shows a waveform obtained by performing the window function processing on the detected beat signal waveform of FIG. 2A, and corresponds to the waveform 46 of FIG. Comparison of frequency spectrum distribution results by FFT of each of FIGS. 2A and 2B is shown in 51 and 52 of FIG. 2C. The half width of the beat frequency spectrum 52 after the window function processing is narrowed to half of the unprocessed beat frequency spectrum 51, and at the same time, the S / N ratio 53 with the background noise is improved by 10 to 20 dB. 9 illustrates the effectiveness of the method of the present invention.
【００１１】[0011]
【発明の効果】以上説明したように本発明によれば分岐
された光信号を再び重ねて得られたビート信号時間波形
を処理する装置において、上記ビート信号時間波形に上
記光信号の周波数の繰り返し変調周期ごとに窓関数を掛
け合せ、ついでフーリエ変換してビート周波数成分を特
定する演算装置を備えたことにより、光周波数変調（掃
引）が可能な様々な光源を用いた光周波数領域反射測定
法の測定精度と分解能の向上が可能となり、また、光周
波数領域反射測定法によって得られるビート信号の周波
数成分の選択抽出の感度が向上し、これより周波数領域
でのＳ／Ｎ比が向上できる。As described above, according to the present invention, in a device for processing a beat signal time waveform obtained by superimposing split optical signals again, the beat signal time waveform has a repetition of the frequency of the optical signal. By providing an arithmetic unit for multiplying a window function for each modulation period and then performing Fourier transform to specify a beat frequency component, the optical frequency domain reflection measurement method using various light sources capable of optical frequency modulation (sweep) is provided. The measurement accuracy and the resolution can be improved, and the sensitivity of selective extraction of the frequency component of the beat signal obtained by the optical frequency domain reflection measurement method can be improved, whereby the S / N ratio in the frequency domain can be improved.
【図面の簡単な説明】[Brief description of the drawings]
【図１】検出ビート信号の波形処理の説明図。FIG. 1 is an explanatory diagram of waveform processing of a detected beat signal.
【図２】実際の測定実験結果の波形図。FIG. 2 is a waveform chart of an actual measurement experiment result.
【図３】本発明の実施の形態を示すブロック図。FIG. 3 is a block diagram illustrating an embodiment of the present invention.
【図４】ビート信号の検出原理図。FIG. 4 is a diagram illustrating the principle of detection of a beat signal.
１０ 光検出器 １１ Ａ／Ｄ変換器 １２ 演算装置 ４０ 光周波数変調波形 ４１，４２ ビート信号 ４３ トリガー ４４ 窓関数波形 ４５ 搬送波形 ４６ 窓関数処理ビート波形 Reference Signs List 10 photodetector 11 A / D converter 12 arithmetic unit 40 optical frequency modulation waveform 41, 42 beat signal 43 trigger 44 window function waveform 45 carrier waveform 46 window function processing beat waveform
─────────────────────────────────────────────────────
────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成９年９月９日[Submission date] September 9, 1997
【手続補正１】[Procedure amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】０００４[Correction target item name] 0004
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【０００４】[0004]
【発明が解決しようとする課題】ところが、τの領域の
増大に伴った場合のビ−ト周波数スペクトルｆb2の強度
波形３３は、チャ−ピング現象によりその最大値におけ
るビ−ト周波数の値が明瞭に識別できずある幅でしか特
定するしかないため、そのビ−ト周波数値をパラメ−タ
とした計測においては計測精度・分解能の劣化が生ず
る。一つの具体例としては、測長の応用においてそのτ
の領域の増大は長距離になればなるほど顕著となり計測
精度の劣化を助長することになる。However, the intensity waveform 33 of the beat frequency spectrum f b2 when the region of τ is increased has a maximum value of the beat frequency due to the chirping phenomenon. Since it cannot be clearly identified but has to be specified only with a certain width, the measurement accuracy and resolution deteriorate in measurement using the beat frequency value as a parameter. As one specific example, the τ in applications of measurement
The increase of the area becomes more remarkable as the distance becomes longer, which promotes the deterioration of the measurement accuracy.
Claims (2)
ビート信号時間波形を処理する装置において、 上記ビート信号時間波形に上記光信号の周波数の繰り返
し変調周期ごとに窓関数を掛け合せ、ついでフーリエ変
換してビート周波数成分を特定する演算装置を備えた光
周波数領域反射測定法の検出信号処理装置。An apparatus for processing a beat signal time waveform obtained by superimposing split optical signals again, wherein the beat signal time waveform is multiplied by a window function for each repetition modulation cycle of the frequency of the optical signal. A detection signal processing device of an optical frequency domain reflection measurement method, comprising an arithmetic device for specifying a beat frequency component by performing a Fourier transform.
ート信号時間波形に窓関数をトリガ同期によりタイミン
グよく掛け合せ、ついでフーリエ変換することで周波数
スペクトラムを求める演算装置を有する請求項１記載の
光周波数領域反射測定法の検出信号処理装置。2. The optical device according to claim 1, further comprising an arithmetic unit for obtaining a frequency spectrum by multiplying the beat signal time waveform digitized by the A / D converter by a window function with good timing by trigger synchronization, and then performing Fourier transform. Detection signal processor for frequency domain reflection measurement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9173473A JPH1123215A (en) | 1997-06-30 | 1997-06-30 | Detection-signal processor in optical-frequency-region-reflection measuring method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9173473A JPH1123215A (en) | 1997-06-30 | 1997-06-30 | Detection-signal processor in optical-frequency-region-reflection measuring method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1123215A true JPH1123215A (en) | 1999-01-29 |
Family
ID=15961144
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9173473A Pending JPH1123215A (en) | 1997-06-30 | 1997-06-30 | Detection-signal processor in optical-frequency-region-reflection measuring method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1123215A (en) |
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|---|---|---|---|---|
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1997
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20110137738A (en) * | 2010-06-17 | 2011-12-23 | 리오스 테크놀러지 게엠베하 | Method and device for spatial-resolved measuring of a physical size |
| JP2012002815A (en) * | 2010-06-17 | 2012-01-05 | Lios Technology Gmbh | Method and device for measuring local resolution of physical amount |
| JP2014103336A (en) * | 2012-11-22 | 2014-06-05 | Anritsu Corp | Mode hop detector and detection method of wavelength sweeping light source |
| JP2018516496A (en) * | 2015-04-13 | 2018-06-21 | ディーエスシージー ソルーションズ，インコーポレイテッド | Voice detection system and method |
| CN107678011A (en) * | 2017-09-28 | 2018-02-09 | 天津大学 | A kind of real-time upload process method of all-wave graphic data applied to laser measurement system |
| CN107678011B (en) * | 2017-09-28 | 2020-08-18 | 天津大学 | Full waveform data real-time uploading processing method applied to laser measurement system |
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