JPH02128126A - Light frequency encoder - Google Patents
Light frequency encoderInfo
- Publication number
- JPH02128126A JPH02128126A JP28040488A JP28040488A JPH02128126A JP H02128126 A JPH02128126 A JP H02128126A JP 28040488 A JP28040488 A JP 28040488A JP 28040488 A JP28040488 A JP 28040488A JP H02128126 A JPH02128126 A JP H02128126A
- Authority
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- Prior art keywords
- light
- polarization
- optical frequency
- quartz
- light source
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 230000010287 polarization Effects 0.000 claims abstract description 54
- 239000010453 quartz Substances 0.000 claims abstract description 34
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 34
- 125000006850 spacer group Chemical group 0.000 claims abstract description 21
- 230000003287 optical effect Effects 0.000 claims description 54
- 239000000463 material Substances 0.000 claims description 17
- 238000005259 measurement Methods 0.000 claims description 13
- 239000013307 optical fiber Substances 0.000 claims description 12
- 239000013078 crystal Substances 0.000 abstract description 10
- 239000000126 substance Substances 0.000 abstract description 4
- 238000010276 construction Methods 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 11
- 239000011521 glass Substances 0.000 description 9
- 229910052646 quartz group Inorganic materials 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 5
- 210000000078 claw Anatomy 0.000 description 3
- 241001417495 Serranidae Species 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 208000025174 PANDAS Diseases 0.000 description 1
- 208000021155 Paediatric autoimmune neuropsychiatric disorders associated with streptococcal infection Diseases 0.000 description 1
- 240000000220 Panda oleosa Species 0.000 description 1
- 235000016496 Panda oleosa Nutrition 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
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Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、光計測分野に属し、光干渉を利用して光源光
の光周波数の変化量を検出する光周波数エンコーダに関
するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention belongs to the field of optical measurement and relates to an optical frequency encoder that detects the amount of change in the optical frequency of light source light using optical interference.
（従来の技術）
第２図は、光干渉を利用して光周波数の変化量を検出す
る光周波数エンコーダの第１の従来例を示す構成図であ
る。第２図において、１は光源、２は対物レンズ、３ａ
、３ｂはくさび形ガラスブロックで、それぞれ片面の反
射率を高めてあり、その二つの面が平行に正対し、フィ
ネスの高いファブリ・ベロ干渉計３を構成している。な
お、くさび形ガラスブロック３ａは、くさび形ガラスブ
ロック３ｂとの前記平行状態を保持しながら光軸方向に
移動可能となっている。また、４はファブリ・ベロ干渉
計３の出力光強度を電気信号に変換する光検出器である
。(Prior Art) FIG. 2 is a block diagram showing a first conventional example of an optical frequency encoder that detects the amount of change in optical frequency using optical interference. In Fig. 2, 1 is a light source, 2 is an objective lens, and 3a
, 3b are wedge-shaped glass blocks, each of which has a high reflectance on one side, and the two faces are parallel and face each other, forming a Fabry-Bello interferometer 3 with high finesse. Note that the wedge-shaped glass block 3a is movable in the optical axis direction while maintaining the parallel state with the wedge-shaped glass block 3b. Further, 4 is a photodetector that converts the output light intensity of the Fabry-Bello interferometer 3 into an electrical signal.
このような構成を有する第１の従来例では、光１１ｉＸ
１からの光を対物レンズ２で平行光にし、この平行光を
くさび形ガラスブロック３ａ、３ｂからなるファブリ・
ベロ干渉計３に入射させる。そして、くさび形ガラスブ
ロック３ａを第３図（ａ）に示すように、光軸方向に対
して鋸状に変位させる。In the first conventional example having such a configuration, the optical 11iX
The light from 1 is made into parallel light by objective lens 2, and this parallel light is passed through a Fabry lens consisting of wedge-shaped glass blocks 3a and 3b.
Inject it into the Belo interferometer 3. Then, the wedge-shaped glass block 3a is displaced in a sawtooth manner with respect to the optical axis direction, as shown in FIG. 3(a).
その結果、第３図（ｂ）に示すように、光周波数および
くさび形ガラスブロック３ａと３ｂ間の距離に対応して
、ファブリーベロ干渉計３の出力光の極大値位置が、理
想的には破線■、■、■で示すように時間変化する。こ
の時間変化は、出力光強度を光検出器４で電気信号に変
換し、これを図示しない処理器等で検出していた。As a result, as shown in FIG. 3(b), depending on the optical frequency and the distance between the wedge-shaped glass blocks 3a and 3b, the maximum position of the output light of the Fabry-Bello interferometer 3 is ideally It changes over time as shown by the broken lines ■, ■, ■. This time change is determined by converting the output light intensity into an electrical signal by the photodetector 4, which is detected by a processor or the like (not shown).
第４図は、光干渉を利用して光周波数の変化量を検出す
る光周波数エンコーダの第２の従来例を示す構成図であ
る。この第２の従来例と前記第１の従来例と異なる点は
、二つのくさび形ガラスブロック３ａ、３ｂからなるフ
ァブリ壷ベロ干渉計３の代わりに、両端面が平行なガラ
スブロックからなるフィネスの低いファブリ・ベロ干渉
計５を用いた点にある。FIG. 4 is a configuration diagram showing a second conventional example of an optical frequency encoder that detects the amount of change in optical frequency using optical interference. The difference between this second conventional example and the first conventional example is that instead of the Fabry Urn-Bello interferometer 3 consisting of two wedge-shaped glass blocks 3a and 3b, a finesse interferometer consisting of a glass block whose both end surfaces are parallel is used. The point is that a low Fabry-Bello interferometer 5 is used.
このような構成を有する第２の従来例では、前記第１の
従来例と同様に、光源１からの光を対物レンズ２で平行
光にし、この平行光をファブリ・ベロ干渉計５に入射さ
せると、第５図（ａ）に示すような、光源１からの光周
波数の変化によるファブリ・ベロ干渉計５の出力光の強
度変化が検出される。In the second conventional example having such a configuration, similarly to the first conventional example, the light from the light source 1 is made into parallel light by the objective lens 2, and this parallel light is made to enter the Fabry-Bello interferometer 5. Then, as shown in FIG. 5(a), a change in the intensity of the output light of the Fabry-Bello interferometer 5 due to a change in the optical frequency from the light source 1 is detected.
（発明が解決しようとする課題）
しかしながら、上記第１の従来例によれば、第３図（Ｃ
）の実線Ａで示すように、例えば光源１による光の光周
波数が増加している場合には、第３図（ｂ）に示す破線
■、■、■の位置から同図の実線ａ、ｂ、ｃで示す位置
にずれることになるが、実線ａを例にとると、これが破
線■による位置の波形がずれたものなのか、破線■によ
る位置の波形がずれたものなのか判断できず、同様に実
線すで示す波形も破線■による位置の波形がずれたもの
なのか、破線■による位置の波形がずれたものなのか、
判断できず、結局、実線Ｃによって漸く光源１による光
の光周波数が増加していると判断できる、といったよう
に、光周波数の増減方向の判断が困難であるという問題
点があった。(Problem to be Solved by the Invention) However, according to the first conventional example, as shown in FIG.
), if the optical frequency of the light emitted by the light source 1 is increasing, for example, if the optical frequency of the light from the light source 1 is increasing, the solid lines a, b in the figure will change from the positions of the broken lines ■, ■, ■ shown in FIG. , c, but if we take the solid line a as an example, it cannot be determined whether this is the waveform at the position indicated by the broken line ■ or the waveform at the position indicated by the broken line ■. Similarly, for the waveform shown by the solid line, is the waveform at the position indicated by the broken line ■ shifted, or is the waveform at the position indicated by the broken line ■ shifted?
There was a problem in that it was difficult to determine the direction of increase or decrease in the optical frequency, as in the case where it could be determined from the solid line C that the optical frequency of the light emitted by the light source 1 was finally increasing.
また、くさび形ガラスブロック３ａの変位速度と光周波
数の変化速度との関係で、第３図（ｄ）に示すように、
破線■、■、■による位置の波形が、実線ｄ、ｅのよう
に、破線■、■、■間のほぼ中央にずれた場合等は、第
３図（ｅ）の実線Ｂに示すように、光周波数が増加して
いるのか、あるいは同図中、実線Ｃに示すように、光周
波数が減少しているのかを判断することは極めて困難で
あるという問題点があった。Furthermore, as shown in FIG. 3(d), the relationship between the displacement speed of the wedge-shaped glass block 3a and the change speed of the optical frequency is as follows.
If the waveform at the position indicated by the dashed lines ■, ■, ■ is shifted to the approximate center between the dashed lines ■, ■, ■, as shown by the solid lines d and e, the waveform at the position indicated by the dashed lines However, there is a problem in that it is extremely difficult to determine whether the optical frequency is increasing or decreasing as shown by the solid line C in the figure.
同様に、第２の従来例の場合も、第５図（ａ）に示す検
出波形からは、光源１による光の光周波数が、第５図（
ｂ）に示す実線りのように変化しているのか、あるいは
実線Ｅのように変化しているのか判断できず、光周波数
の増減方向の判断が極めて困難であるという問題点があ
った。Similarly, in the case of the second conventional example, the detected waveform shown in FIG. 5(a) indicates that the optical frequency of the light emitted by the light source 1 is
There was a problem in that it was not possible to determine whether the optical frequency was changing as shown by the solid line shown in b) or as shown by the solid line E, and it was extremely difficult to determine the direction in which the optical frequency increased or decreased.
また、この光周波数の増減方向が判断できないという問
題点を解決するために、二つのファブリ・ベロ干渉計を
独立して用い、これらの二つの出力光の強度変化に位相
差をもたせ、光周波数変化を検出する場合、その構成が
複雑となり、温度による影響を独立に受けるため、不安
定となる問題点がある。In addition, in order to solve the problem of not being able to determine the direction of increase or decrease in the optical frequency, we used two Fabry-Bérot interferometers independently and created a phase difference in the intensity changes of these two output lights. When detecting a change, the structure is complicated and is independently affected by temperature, resulting in instability.
本発明の目的は、上記問題点に鑑み、簡易な構成で、光
周波数の変化量並びにその増減方向を検出することので
きる光周波数エンコーダを提供することにある。SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical frequency encoder that has a simple configuration and can detect the amount of change in optical frequency and the direction of increase or decrease thereof.
（課題を解決するための手段）
上記目的を達成するため、請求項（１）では、光源によ
る光の光周波数変化量を検出する光周波数エンコーダに
おいて、光源光を測定光と参照先に分割する光分割手段
と、測定光を所定の偏波モードに設定する偏波モード設
定手段と、所定の偏波モードに設定された測定光から二
つの偏波モードを励起し、かつ、これら偏波モード間の
位相差が所定値となるようにその長さを設定した複屈折
物質と、該複屈折物質の出力光を二つの偏波に分割する
偏波分割手段と、該偏波分割手段により分割した各偏波
強度をそれぞれ電気信号に変換する第１および第２の光
検出器と、前記参照光強度を電気信号に変換する第３の
光検出器と、該第３の光検出器による参照信号に基づい
て前記第１および第２の光検出器による各偏波信号から
光源光の光強度変化成分を取り除く演算処理部と、該演
算処理部により処理された二つの偏波信号の位相差に対
応したパルスを発生するパルス発生部とを備えた。(Means for Solving the Problem) In order to achieve the above object, claim (1) provides that in an optical frequency encoder that detects the amount of change in optical frequency of light caused by a light source, the light source light is divided into measurement light and reference target light. a light splitting means; a polarization mode setting means for setting the measurement light to a predetermined polarization mode; and a polarization mode setting means for exciting two polarization modes from the measurement light set to the predetermined polarization mode; a birefringent material whose length is set so that the phase difference between the two polarized waves is a predetermined value; a polarization splitting means for splitting the output light of the birefringent material into two polarized waves; a first and second photodetector that converts each of the polarization intensities into electrical signals; a third photodetector that converts the reference light intensity into an electrical signal; and a reference light detector by the third photodetector. an arithmetic processing unit that removes a light intensity change component of the light source light from each polarization signal from the first and second photodetectors based on the signal; and a phase difference between the two polarization signals processed by the arithmetic processing unit. and a pulse generator that generates pulses corresponding to the pulses.
また、請求項（２）では、前記複屈折物質を石英をスペ
ーサとして接合した石英スペーサ付水晶ハタの一波長板
から構成した。Further, in claim (2), the birefringent material is constituted by a single wavelength plate of a quartz group with a quartz spacer bonded with quartz as a spacer.
また、請求項（３）では、前記複屈折物質を応力付与型
複屈折光ファイバから構成した。Moreover, in claim (3), the birefringent substance is constituted by a stress-applying birefringent optical fiber.
（作 用）
請求項（１）または請求項（２）または請求項（３）に
よれば、光源による光は、光分割手段により測定光と参
照光とに分割され、参照光は第３の光検出器にて受光さ
れ、電気信号の参照信号に変換され演算処理部に人力す
る。(Function) According to claim (1), claim (2), or claim (3), the light emitted from the light source is split into measurement light and reference light by the light splitting means, and the reference light is split into third light. The light is received by a photodetector, converted into an electrical reference signal, and sent to the arithmetic processing section.
一方、測定光は、偏波モード設定手段によって所定の偏
波モードに設定された後、複屈折物質に入射する。所定
の偏波モードの測定光がら、この複屈折物質により二つ
の偏波モードが励起され、これら二つの偏波がそれぞれ
多重反射して干ルする。複屈折物質は、この二つの偏波
の位相差が所定値となるようにその長さを設定しである
ので、この複屈折物質による二つの偏波の出力光強度は
所定の位相差をもって変化する。On the other hand, the measurement light is set to a predetermined polarization mode by the polarization mode setting means, and then enters the birefringent material. Two polarization modes are excited by the birefringent material from the measurement light of a predetermined polarization mode, and these two polarization waves are subjected to multiple reflections, respectively. The length of the birefringent material is set so that the phase difference between these two polarized waves is a predetermined value, so the output light intensity of the two polarized waves by this birefringent material changes with the predetermined phase difference. do.
このような、複屈折物質の出力光は、偏波分割手段によ
って、二つの偏波に分割され、一方の偏波は第１の光検
出器で受光されて、電気信号の偏波信号に変換されて、
演算処理部に入力する。同様に、分割された他方の偏波
は第２の光検出器で受光され、電気信号の偏波信号に変
換されて、演算処理部に入力する。The output light of the birefringent material is split into two polarized waves by the polarization splitting means, and one polarized wave is received by the first photodetector and converted into a polarized electrical signal. Been,
Input to the arithmetic processing section. Similarly, the other divided polarized wave is received by the second photodetector, converted into a polarized electric signal, and input to the arithmetic processing section.
演算処理部は、入力した参照信号に基づいて、二つの偏
波信号の光強度変化成分を取り除き、この処理後の二つ
の偏波信号がパルス発生手段に人力する。The arithmetic processing section removes light intensity change components of the two polarized signals based on the input reference signal, and the two polarized signals after this processing are inputted to the pulse generating means.
パルス発生手段は入力した二つの信号の位相差から光源
光の光周波数の増減方向並びにその光周波数の変化量に
対応したパルスを発生する。The pulse generating means generates a pulse corresponding to the direction of increase/decrease in the optical frequency of the light source light and the amount of change in the optical frequency from the phase difference between the two input signals.
（実施例）
第１図は、本発明による光周波数エンコーダの第１の実
施例を示す構成図である。第１図において、１１は波長
１．３μ層の半導体レーザからなる光源、１２は光源１
１による光を平行光束とする対物レンズ、１３は光ｉｌ
ｌによる光を測定光ＰＢと参照光ＲＢに分割するビーム
スプリッタ（光分割手段）、１４は測定光ＰＢを直線偏
波とする偏光子（偏波モード設定手段）、１５はファブ
リ・ペロ干渉計を構成する石英１５ａ１水晶１５ｂを備
えた石英スペーサ付き水晶ハタの一波長板で、偏光子１
４による直線偏波がらＸおよびｙの二つの偏波モードを
励起し、がっ、これら二つの偏波モード間の位相差が所
定値となるようにその長さを、例えば２０ｍｍに設定し
ており、端面の反射率Ｒは、例えば０．０４としている
。１６は偏光ビームスプリッタ（偏波分割手段）で、石
英スペーサ付き水晶ハタの一波長板１５の出力光をＸ偏
波ＰＢｘとｙ偏波ＰＢｙに分割する。１７ａはＸ偏波Ｐ
ＢＸを受光して電気信号のＸ偏波信号ＰＥｘに変換する
第１の光検出器、１７ｂはｙ偏波ＰＢｙを受光して電気
信号のｙ偏波信号ＰＥｙに変換する第２の光検出器、１
７ｃは参照光ＲＢを受光して電気信号の参照信号ＲＥに
変換する第３の光検出器で、これら第１乃至第３の光検
出器１７ａ、１７ｂ、１７ｃは、例えばＩｎＧａＡｓ−
ＰＩＮにより構成している。(Embodiment) FIG. 1 is a block diagram showing a first embodiment of an optical frequency encoder according to the present invention. In FIG. 1, 11 is a light source consisting of a semiconductor laser with a wavelength of 1.3μ layer, and 12 is a light source 1.
1 is an objective lens that converts the light from 1 into a parallel beam; 13 is a light beam;
14 is a polarizer (polarization mode setting means) that makes the measurement light PB linearly polarized; 15 is a Fabry-Perot interferometer; A single-wavelength plate of a quartz group with a quartz spacer, including quartz 15a1 and quartz 15b constituting the polarizer 1.
Excite the two polarization modes of X and y from the linearly polarized wave according to 4, and set the length to, for example, 20 mm so that the phase difference between these two polarization modes becomes a predetermined value. The reflectance R of the end face is, for example, 0.04. Reference numeral 16 denotes a polarizing beam splitter (polarization splitting means) which splits the output light from the single-wavelength plate 15 made of a quartz group with a quartz spacer into an X-polarized wave PBx and a y-polarized wave PBy. 17a is the X polarization P
The first photodetector 17b receives the y-polarized wave PBy and converts it into the y-polarized electric signal PEy. ,1
A third photodetector 7c receives the reference light RB and converts it into an electric reference signal RE.
It is configured using a PIN.
１８は演算処理部で、第１および第２の光検出器１７ａ
、１７ｂによるＸ偏波信号ＰＥｘおよびｙ偏波信号ＰＥ
ｙを光検出器１７ｃによる参照信号ＲＥで除算して、光
源１１の光強度変化成分を取り除き、交流成分の信号Ｅ
Ｘ、Ｅｙを取り出す。18 is an arithmetic processing unit, and the first and second photodetectors 17a
, 17b, the X polarization signal PEx and the y polarization signal PE
y is divided by the reference signal RE from the photodetector 17c to remove the light intensity change component of the light source 11, and the alternating current component signal E is obtained.
Take out X and Ey.
１つはパルス発生部で、演算処理部１８の出力信号ＥＸ
、Ｅｙの入力により、光源１１からの光周波数の変化に
より生じる強度変化の二つの偏波モードｘ、ｙ間、即ち
、Ｘ偏波ＰＢｘとｙ偏波ＰＢｙ間の位相差から光周波数
が増加している場合には、前進パルスを、減少している
場合には、後進パルスをその変化量に応じて発生し、出
力する。One is a pulse generation section, which receives the output signal EX of the arithmetic processing section 18.
, Ey, the optical frequency increases due to the phase difference between the two polarization modes x and y of the intensity change caused by the change in the optical frequency from the light source 11, that is, between the X polarization PBx and the y polarization PBy. If it is decreasing, a forward pulse is generated, and if it is decreasing, a backward pulse is generated and output in accordance with the amount of change.
次に、上記構成による動作を、第６図を参照しながら順
を追って説明する。Next, the operation of the above configuration will be explained step by step with reference to FIG.
まず、波長１．３μ置の半導体レーザである光源１１へ
の注入電流を変化させることで、光源１１による光の光
周波数を第６図（ａ）に示すように、Δｆ〜３０ＧＩｌ
ｚ（波長換算で、１．７オングストローム）変化させる
。この光源１１による光は、対物レンズ１２により平行
ビーム光となり、ビームスプリッタ１３で測定光ＰＢと
参照光ＲＢに分割され、測定光ＰＢは偏光子１４に入射
し、参照光ＲＢは、光検出器１７ｃに受光されて、電気
信号の参照信号ＲＥに変換される。First, by changing the current injected into the light source 11, which is a semiconductor laser with a wavelength of 1.3μ, the optical frequency of the light from the light source 11 is changed from Δf to 30GIl, as shown in FIG. 6(a).
z (1.7 angstroms in terms of wavelength). The light from this light source 11 is converted into a parallel beam by an objective lens 12, and is split into a measuring beam PB and a reference beam RB by a beam splitter 13. The measuring beam PB is incident on a polarizer 14, and the reference beam RB is transmitted to a photodetector. The light is received by 17c and converted into a reference signal RE of an electric signal.
一方、偏光子１４に入射した測定光ＰＢは、石英スペー
サ付き水晶ハタの一波長板１５の水晶１５ｂの複屈折軸
に対して４５°にその偏波面が設定された直線偏波とな
って、石英スペーサ付き水晶ハタの一波長板１５に石英
スペーサ１５ａ側から入射する。これにより、Ｘおよび
ｙの二つの偏波モードが励起され、Ｘ偏波ＰＢＸおよび
ｙ偏波ＰＢｙがそれぞれ多重反射し干渉する。On the other hand, the measurement light PB incident on the polarizer 14 becomes a linearly polarized wave whose plane of polarization is set at 45 degrees with respect to the birefringence axis of the crystal 15b of the single-wavelength plate 15 of the crystal group with a quartz spacer. The light enters the single-wavelength plate 15 made of a quartz group with a quartz spacer from the quartz spacer 15a side. As a result, two polarization modes, X and y, are excited, and the X-polarized wave PBX and the y-polarized wave PBy are each reflected multiple times and interfere with each other.
ここで、石英スペーサ付き水晶ハタの一波長板１５の石
英１５ａの長さをＬｇ、石英１５ａの屈折率を０１水晶
１５ｂの長さをＬｃ、水晶１５ｂの２軸の屈折率をそれ
ぞれｎｘ、ｎｙとし、レーザ光の光周波数をｆとすると
、多重反射光の、ある光とその１つ前の光との位相差Φ
Ｘ、Φｙは、Ｃを光速度として、
Φｘ−２π・２ （ｎＬｇ ＋ｎＸ Ｌｃ ） ／λ−
４π（ｎＬｇ＋ｎｘＬｃ）ｆ／ｃ （１）Φｙ −
２ｙｒ ・２ （ｎＬｇ ＋ｎｙ Ｌｃ ） ／λ−４
π（ｎＬｇ 十ｎｙ Ｌｃ ）ｆ／ｃ （２）とな
り、光周波数ｆに比例する。干渉の結果、石英スペーサ
付き水晶ハタの一波長板１５の出力光強度１ ｏｕｔｘ
、 Ｉ ｏｕｔｙは、ΦＸ、Φｙを位相としてＩ ｏ
ｕｔｘ／ Ｉ １ｎ
＝１／ （１＋Ｆ ５ｉｎ２（Φｘ／２））（３）１
ｏｕｔｙ／ Ｉ １ｎ
＝１／（１＋Ｆ ５ｉｎ２（Φｙ／２））（４）Ｆ−
４Ｒ／ （１−Ｒ） ２
となり、光周波数ｆの変化に対応して変化する。Here, the length of the quartz 15a of the single-wavelength plate 15 of the quartz group with a quartz spacer is Lg, the refractive index of the quartz 15a is 01, the length of the crystal 15b is Lc, and the refractive index of the two axes of the crystal 15b is nx, ny, respectively. If the optical frequency of the laser beam is f, then the phase difference Φ between a certain light and the previous light in the multiple reflected light is
X, Φy are Φx−2π・2 (nLg +nX Lc) /λ−, where C is the speed of light.
4π(nLg+nxLc)f/c (1)Φy −
2yr ・2 (nLg +ny Lc) /λ-4
π(nLg +ny Lc)f/c (2), which is proportional to the optical frequency f. As a result of the interference, the output light intensity of the single-wavelength plate 15 made of quartz crystal with a quartz spacer is 1 outx
, I outy is I o with ΦX and Φy as phases.
utx/ I 1n = 1/ (1+F 5in2 (Φx/2)) (3) 1
outy/ I 1n = 1/(1+F 5in2(Φy/2)) (4)F-
4R/(1-R) 2 and changes in response to changes in the optical frequency f.
なお、Ｒは石英スペーサ付きハタの一波長板１５の端面
の反射率である。本節１の実施例では反射率Ｒ−０，０
４と小さくとったので出力光強度は、１ ｏｕＬｘ／
Ｉ Ｉｎ 〜１− Ｆ ５ｉｎ２（Φｘ／２）−１−
Ｆ／２ （１−ｃｏｓΦｘ ） （６）
Ｉ ｏｕｔｙ／ Ｉ ｉｎ 〜１− Ｆ ５ｉｎ２（
Φｙ／２）−１−Ｆ／２ （１−ｃｏｓΦｙ ）
（７）と近似できる。。ここで、石英スペー
サ付水晶ハタの一波長板１５は、
（ｎｘ −ｎｙ ） Ｌｃ −１／８ ・λ−１／ ８
争 ｃ／ｆ （８）従って、上記（１）およ
び（２）式からΦＸ−Φｙ
＝４πＩＩ（ｎｘ −ｎｙ ）Ｌｃ Ｑｆ／ｃ−π ／
２
（９）となり、Ｘ偏波ＰＢＸおよび
ｙ偏波ＰＢｙの出力光強度がπ／２の位相差をもって変
化する。Note that R is the reflectance of the end face of the grouper single-wavelength plate 15 with a quartz spacer. In the example of this section 1, the reflectance R-0,0
Since the output light intensity is set as low as 4, the output light intensity is 1 ouLx/
I In ~1- F 5in2 (Φx/2)-1-
F/2 (1-cosΦx) (6)
I outy/I in ~1-F5in2(
Φy/2)-1-F/2 (1-cosΦy)
(7) can be approximated. . Here, the single-wavelength plate 15 made of quartz crystal with a quartz spacer has the following formula: (nx −ny) Lc −1/8 ・λ−1/8
Conflict c/f (8) Therefore, from equations (1) and (2) above, ΦX-Φy = 4πII (nx - ny) Lc Qf/c-π /
2
(9), and the output light intensities of the X-polarized wave PBX and the y-polarized wave PBy change with a phase difference of π/2.
次に、この石英スペーサ付水晶ハタの一波長板１５の出
力光のＸ偏波ＰＢＸおよびｙ偏波ＰＢｙは偏光ビームス
プリッタ１６により分割され、光検出器１７ａ、１７ｂ
によりＸ偏波ＰＢｘおよびｙ偏波ＰＢｙがそれぞれ受光
され、その出力光強度が電気信号ＰＥｘ、ＰＥｙ、に変
換される。Next, the X-polarized wave PBX and the y-polarized wave PBy of the output light of the single-wavelength plate 15 of the quartz group with a quartz spacer are split by a polarizing beam splitter 16, and are transmitted to the photodetectors 17a, 17b.
The X-polarized wave PBx and the y-polarized wave PBy are respectively received, and their output light intensities are converted into electrical signals PEx, PEy.
次に、演算処理部１８において、光検出器１７ａ、１７
ｂによるＸおよびｙ偏波信号ＰＥｘ。Next, in the arithmetic processing section 18, the photodetectors 17a, 17
b X and y polarization signals PEx.
ＰＥｙをそれぞれ参照信号ＲＥで割り算し、光源１１に
よる光、即ち、レーザ光の光強度変化成分を取り除き、
交流成分を取り出す。ここで、ｎ 〜ｎｘ 〜ｎｙ 〜
１．５ （１０）Ｌ−Ｌｇ ＋Ｌｃ
−２０＋ｓｍ （１０ｃ −３，ＯＸ
１０８ｍ１ｓ （１２）として、
位相Φを概算すると、
Φｒ＋ｆ−Φｆｍ４πｎＬΔｆ ／ ｃ−４πＸ１．５
Ｘ２０Ｘ１０’Ｘ３０ＸＩＯ／３．０Ｘ１０８
−１２π （１
３）となり、第６図（ｂ）および（Ｃ）に示すような、
二つの信号Ｅｘ、Ｅｙが得られる。ここで、光源１１に
よる光の光周波数が増加している場合、Ｘ偏波ＰＢｘの
光強度変化の位相がｙ偏波に比べてπ／２進み、逆に光
周波数が減少している場合、ｙ偏波ＰＢｙがＸ偏波ＰＢ
ｘに比べてπ／２進んでいる。Divide each PEy by the reference signal RE to remove the light intensity change component of the light from the light source 11, that is, the laser light,
Take out the AC component. Here, n ~ nx ~ ny ~
1.5 (10) L-Lg +Lc
-20+sm (10c -3,OX
As 108m1s (12),
Approximately the phase Φ is: Φr+f−Φfm4πnLΔf/c−4πX1.5
X20X10'X30XIO/3.0X108 -12π (1
3), as shown in Figures 6(b) and (C),
Two signals Ex and Ey are obtained. Here, when the optical frequency of the light from the light source 11 is increasing, the phase of the optical intensity change of the Y polarization PBy becomes X polarization PB
It is ahead of x by π/2.
次に、これら位相がπ／２互いに進退する２つの信号Ｅ
ｘ、Ｅｙから前進および後進パルスを発生させることの
できるパルス発生部１９に、第６図（ｂ）および（Ｃ）
に示す二つの信号ＥＸ、Ｅｙが入力し、これが例えば４
逓倍されて、第６図（ｄ）に示すように、レーザ光の光
周波数が増加している場合には前進パルスが、また、減
少している場合には後進パルスが、光周波数の変化量に
対応して発生される。Next, two signals E whose phases advance and retreat from each other by π/2
The pulse generator 19 that can generate forward and backward pulses from
Two signals EX and Ey shown in are input, and this is, for example, 4
After being multiplied, as shown in Figure 6(d), if the optical frequency of the laser beam is increasing, the forward pulse is used, and if it is decreasing, the backward pulse is the amount of change in the optical frequency. is generated in response to.
本第１の実施例によれば、屈折率差が小さく反射率の小
さい接合が可能な石英１５ａと水晶１５ｂとからなる石
英スペーサ付き水晶爪付の一波長板１５を、その屈折率
の違う２軸を二つの独立したファブリ・ベロ干渉計とし
て用いることにより、構成が簡易となり、水晶１５ｂ部
分を薄くし熱膨張係数の低い石英１５ａで長さを確保す
ることにより、温度変化による長さ変化を小さく抑える
ことができ、かつ、上記（１）および（２）式から分か
るように位相Φが長さしに比例するので、分解能の高い
光周波数の変化量検出を実現できる。According to the first embodiment, a single-wavelength plate 15 with a quartz spacer and a crystal claw made of quartz 15a and quartz 15b, which have a small refractive index difference and can be bonded with a low reflectance, is used as a single-wavelength plate 15 with a quartz claw and a quartz spacer, and a single-wavelength plate 15 with a quartz claw with a quartz spacer, which can be bonded with a small refractive index difference and a low reflectance. By using the shaft as two independent Fabry-Bello interferometers, the configuration is simplified, and by making the crystal 15b portion thinner and securing the length with the quartz 15a, which has a low coefficient of thermal expansion, changes in length due to temperature changes can be avoided. This can be kept small, and since the phase Φ is proportional to the length as seen from equations (1) and (2) above, detection of the amount of change in optical frequency with high resolution can be realized.
第７図は、本発明による光周波数エンコーダの第２の実
施例を示す構成図である。FIG. 7 is a block diagram showing a second embodiment of the optical frequency encoder according to the present invention.
本第２の実施例と前記第１の実施例の異なる点は、スペ
ーサ付きハタの一波長板１５の代わりに、応力付与型複
屈折光ファイブ２０、例えば複屈折率Ｂが、
Ｂ−ｎｘ −ｎｙ −４Ｘ １０−’ （１
４）であるＰＡＮＤＡファイバを採用している。また、
対物レンズ２１により、偏光子１４による直線偏波光を
複屈折光ファイバ２０に導入し、偏波面をこの複屈折光
ファイバ２０の偏波軸に対して４５°になるように設定
し、複屈折光ファイバ２０のＸおよびｙの二つの偏波モ
ードを励起し、対物レンズ２２により複屈折光ファイバ
２０からの出力光を平行ビームとする。さらに、この複
屈折光ファイバ２０の出射端は回転し、偏光ビームスプ
リッタ１６と軸合わせ可能で、偏光ビームスプリッタ１
６でＸおよびｙモードを伝搬した光を分割する構成とな
っている。The difference between the second embodiment and the first embodiment is that instead of the single-wavelength plate 15 with a spacer, a stress-applying birefringent optical fiber 20, for example, a birefringent index B of B-nx- ny -4X 10-' (1
4) PANDA fiber is used. Also,
The linearly polarized light from the polarizer 14 is introduced into the birefringent optical fiber 20 by the objective lens 21, and the plane of polarization is set at 45 degrees with respect to the polarization axis of the birefringent optical fiber 20. The two polarization modes, X and Y, of the fiber 20 are excited, and the output light from the birefringent optical fiber 20 is made into a parallel beam by the objective lens 22. Furthermore, the output end of this birefringent optical fiber 20 can be rotated and aligned with the polarizing beam splitter 16,
6 splits the light propagated in the X and y modes.
本第２の実施例において、複屈折光ファイバ２０の長さ
しを
Ｌ −１３０，４０６３關 （１
５）とし、サブミクロンオーダの調節を行うことにより
、Δｆ 〜３０ ＧＨｚで、
Φｒ＋ｆ−Φｆ’ 〜７８π（１Ｂ）
ΦＸ−Φｙ−π／ ２ （１７）と
することができた。In the second embodiment, the length of the birefringent optical fiber 20 is L −130,4063 cm (1
5) and by making adjustments on the submicron order, it was possible to obtain Φr + f - Φf' ~ 78π (1B) ΦX - Φy - π/2 (17) at Δf ~ 30 GHz.
本第２の実施例によれば、応力付与型複屈折光ファイバ
２０を用いることにより、長さおよび端面の調節が容易
にできるようになり、構成面、そして、コアが同質のも
の、例えば石英でできていることから、温度の影響面、
さらに、長さを比較的長くしても干渉性が落ちないこと
から、分解能面において、第１の実施例を上回る性能を
有する利点がある。According to the second embodiment, by using the stress-applied birefringent optical fiber 20, the length and end face can be easily adjusted. Because it is made of
Furthermore, since the coherence does not deteriorate even if the length is relatively long, there is an advantage that the performance is superior to that of the first embodiment in terms of resolution.
（発明の効果）
以上説明したように、請求項（１）によれば、その構成
要素の一つに複屈折物質を用いることにより、位相差を
もった二つのファブリ・ペロ干渉計が一つの材料内に同
時に構成されることになるので、この二つのファブリ・
ベロ干渉計が独立に温度の影響を受けることはなく、シ
かも軸合わせが極めて容易であり、容易に光周波数の変
化量並びにその増減方向を検出することができ、光源か
らの出射光の周波数変化を利用する光計測に極めて有効
な光周波数エンコーダを実現できる。(Effect of the invention) As explained above, according to claim (1), by using a birefringent material as one of the constituent elements, two Fabry-Perot interferometers having a phase difference can be integrated into one. These two fabrics are constructed simultaneously in the material.
Vero interferometers are not independently affected by temperature, are extremely easy to align, and can easily detect the amount of change in optical frequency as well as the direction of increase or decrease. It is possible to realize an optical frequency encoder that is extremely effective for optical measurement that utilizes changes.
また、請求項（２）によれば、請求項（１）の効果に加
えて、水晶部分を薄くし熱膨張係数の低い石英で長さを
確保することにより、温度変化による長さ変化を小さく
抑えることができ、かつ、位相差は石英スペーサ付き部
分の一波長板の長さに比例するので、分解能の高い光周
波数の変化量検出を実現できる。According to claim (2), in addition to the effect of claim (1), by making the crystal part thinner and securing the length with quartz having a low coefficient of thermal expansion, changes in length due to temperature changes are reduced. In addition, since the phase difference is proportional to the length of the single-wavelength plate in the portion with the quartz spacer, it is possible to detect the amount of change in optical frequency with high resolution.
また、請求項（３）によれば、応力付与型複屈折光ファ
イバを用いることにより、長さおよび端面の調節が容易
にできるようになり、構成面、そして、コアが同質の材
料でできていることから、温度の影響面、さらに、長さ
を比較的長くしても干渉性が落ちることがないので、分
解能面において、請求項（２）の場合を上回る性能を得
られる利点がある。According to claim (3), by using a stress-applied birefringent optical fiber, the length and end face can be easily adjusted, and the constituent faces and core are made of the same material. Therefore, there is an advantage that performance superior to the case of claim (2) can be obtained in terms of the influence of temperature, and since the coherence does not deteriorate even if the length is made relatively long, in terms of resolution.
第１図は本発明による光周波数エンコーダの第１の実施
例を示す構成図、第２図は第１の従来例の構成図、第３
図は第１の従来例の動作並びに問題点の説明図、第４図
は第２の従来例の構成図、第５図は第２の従来例の動作
並びに問題点の説明図、第６図は本発明に係る第１の実
施例の動作説明図、第７図は本発明による光周波数エン
コーダの第２の実施例を示す構成図である。
図中、１１・・・光源、１２，２１．２２・・・対物レ
ンズ、１３・・・ビームスプリッタ（光分割手段）、１
４・・・偏光子（偏波モード設定手段）、１５・・・石
英スペーサ付水晶ハタの一波長板（複屈折物質）、１６
・・・偏光ビームスプリッタ（偏波分割手段）、１７ａ
、１７ｂ、 １７ｃｍ・・第１乃至第３の光検出器、
１８・・・演算処理部、１９・・・パルス発生手段、２
０・・・応力付与型複屈折光ファイバ（Ｉ屈折物質）。
特許出願人 日本電信電話株式会社
代理人 弁理士 吉 １） 精 孝ファフ゛す・穴
口干渉計
第２図
出力
尤周ｊ反数
光強度
光」ｎう反数
光強度
変イＩＬｘFIG. 1 is a block diagram showing a first embodiment of an optical frequency encoder according to the present invention, FIG. 2 is a block diagram of a first conventional example, and FIG.
The figure is an explanatory diagram of the operation and problems of the first conventional example, FIG. 4 is a configuration diagram of the second conventional example, FIG. 5 is an explanatory diagram of the operation and problems of the second conventional example, and FIG. 7 is an explanatory diagram of the operation of the first embodiment according to the present invention, and FIG. 7 is a configuration diagram showing the second embodiment of the optical frequency encoder according to the present invention. In the figure, 11... Light source, 12, 21.22... Objective lens, 13... Beam splitter (light splitting means), 1
4... Polarizer (polarization mode setting means), 15... Quartz grouper single wavelength plate with quartz spacer (birefringent material), 16
...Polarizing beam splitter (polarization splitting means), 17a
, 17b, 17cm...first to third photodetectors,
18... Arithmetic processing unit, 19... Pulse generating means, 2
0... Stress-applying birefringent optical fiber (I refractive material). Patent applicant: Nippon Telegraph and Telephone Corporation Agent Patent attorney: Yoshi 1) Precision optical fiber/hole mouth interferometer Figure 2: Output frequency (reciprocal light intensity)
Claims (3)
数エンコーダにおいて、 光源光を測定光と参照光に分割する光分割手段と、 測定光を所定の偏波モードに設定する偏波モード設定手
段と、 所定の偏波モードに設定された測定光から二つの偏波モ
ードを励起し、かつ、これら偏波モード間の位相差が所
定値となるようにその長さを設定した複屈折物質と、 該複屈折物質の出力光を二つの偏波に分割する偏波分割
手段と、 該偏波分割手段により分割した各偏波強度をそれぞれ電
気信号に変換する第１および第２の光検出器と、 前記参照光強度を電気信号に変換する第３の光検出器と
、 該第３の光検出器による参照信号に基づいて前記第１お
よび第２の光検出器による各偏波信号から光源光の光強
度変化成分を取り除く演算処理部と、 該演算処理部により処理された二つの偏波信号の位相差
に対応したパルスを発生するパルス発生部とを備えた ことを特徴とする光周波数エンコーダ。(1) An optical frequency encoder that detects the amount of change in optical frequency of light caused by a light source includes a light splitting means that splits the light source light into a measurement light and a reference light, and a polarization mode setting that sets the measurement light to a predetermined polarization mode. a birefringent material that excites two polarization modes from measurement light set to a predetermined polarization mode, and whose length is set so that the phase difference between these polarization modes is a predetermined value. , a polarization splitting means for splitting the output light of the birefringent material into two polarized waves, and first and second photodetectors for converting each polarization intensity divided by the polarization splitting means into electrical signals, respectively. a third photodetector that converts the reference light intensity into an electrical signal; and a third photodetector that converts the reference light intensity into an electrical signal, and converts each polarization signal from the first and second photodetectors based on the reference signal from the third photodetector. A light source comprising: an arithmetic processing unit that removes a light intensity variation component of the light source light; and a pulse generator that generates a pulse corresponding to a phase difference between two polarized signals processed by the arithmetic processing unit. frequency encoder.
石英スペーサ付水晶八分の一波長板から構成した請求項
（１）記載の光周波数エンコーダ。(2) The optical frequency encoder according to claim (1), wherein the birefringent material is constituted by a quartz one-eighth wavelength plate with a quartz spacer bonded with quartz as a spacer.
ら構成した請求項（１）記載の光周波数エンコーダ。(3) The optical frequency encoder according to claim (1), wherein the birefringent material is composed of a stress-applying birefringent optical fiber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28040488A JPH076845B2 (en) | 1988-11-08 | 1988-11-08 | Optical frequency encoder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28040488A JPH076845B2 (en) | 1988-11-08 | 1988-11-08 | Optical frequency encoder |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02128126A true JPH02128126A (en) | 1990-05-16 |
| JPH076845B2 JPH076845B2 (en) | 1995-01-30 |
Family
ID=17624562
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28040488A Expired - Fee Related JPH076845B2 (en) | 1988-11-08 | 1988-11-08 | Optical frequency encoder |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH076845B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004004080A (en) * | 2002-05-24 | 2004-01-08 | Tektronix Inc | Sweep wavemeter and wavelength calibration method |
| JP2008070385A (en) * | 2001-01-30 | 2008-03-27 | Thorlabs Inc | Device and method for wavelength calibration of swept laser |
-
1988
- 1988-11-08 JP JP28040488A patent/JPH076845B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008070385A (en) * | 2001-01-30 | 2008-03-27 | Thorlabs Inc | Device and method for wavelength calibration of swept laser |
| JP4722110B2 (en) * | 2001-01-30 | 2011-07-13 | ソルラブス、 インコーポレイテッド | Wavelength calibration apparatus and method for swept laser |
| JP2004004080A (en) * | 2002-05-24 | 2004-01-08 | Tektronix Inc | Sweep wavemeter and wavelength calibration method |
| JP4667728B2 (en) * | 2002-05-24 | 2011-04-13 | ソルラブス、 インコーポレイテッド | Sweep wavelength meter and wavelength calibration method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH076845B2 (en) | 1995-01-30 |
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| LAPS | Cancellation because of no payment of annual fees |