JPS63266302A - Length measuring instrument by laser - Google Patents
Length measuring instrument by laserInfo
- Publication number
- JPS63266302A JPS63266302A JP10284787A JP10284787A JPS63266302A JP S63266302 A JPS63266302 A JP S63266302A JP 10284787 A JP10284787 A JP 10284787A JP 10284787 A JP10284787 A JP 10284787A JP S63266302 A JPS63266302 A JP S63266302A
- Authority
- JP
- Japan
- Prior art keywords
- light
- period
- distance
- laser light
- beam splitter
- 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.)
- Pending
Links
- 239000004065 semiconductor Substances 0.000 claims abstract description 13
- 230000003287 optical effect Effects 0.000 claims description 24
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 14
- 238000013139 quantization Methods 0.000 abstract description 9
- 239000013307 optical fiber Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 230000035559 beat frequency Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 235000008694 Humulus lupulus Nutrition 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
Landscapes
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、たとえばX−Yステージの移動体を精密に位
置決めするときなどに用いるレーザ測長装置に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser length measuring device used, for example, when accurately positioning a moving body of an X-Y stage.
光の干渉を利用した従来のレーザ測長器の構成例を第3
図に示す。この方法はHe −Neレーザ発振器20か
ら単一波長のレーザ光を射出させ、ビームスプリッタ4
によって2つに分岐し、一方の光ビームは基準光路を通
って参照鏡5に、他方の光ビームは移動ステージ11上
に固定した移動鏡6に黒山させ、それぞれの鏡からの反
射光をビームスプリッタ4を介してミキシングし、これ
によって生ずる干渉光を分割ミラー21を介して受光器
22・23に入射させ9位相が90°ずれた2つの波E
、Fを発生させる。この出力をプリアンプ24で増幅し
。The third example shows the configuration of a conventional laser length measuring device that uses optical interference.
As shown in the figure. In this method, a single wavelength laser beam is emitted from a He-Ne laser oscillator 20, and a beam splitter 4
One of the light beams passes through the reference optical path and reaches the reference mirror 5, and the other light beam passes through the movable mirror 6 fixed on the movable stage 11, and the reflected light from each mirror is converted into a beam. The interference light generated by this is mixed through the splitter 4 and is incident on the light receivers 22 and 23 through the splitting mirror 21, resulting in two waves E whose phases are shifted by 90 degrees.
, F is generated. This output is amplified by the preamplifier 24.
加速カウンタ25で、波Eの零クロス点で発生させたパ
ルスP1を移動方向によって波Fのプラス側で発生させ
たパルスP2の1または0との論理演算によって計測し
、距離演算回路26で移動量と移動方向を演算するもの
である。12はステージ移動用モータである。The acceleration counter 25 measures the pulse P1 generated at the zero cross point of the wave E by a logical operation with 1 or 0 of the pulse P2 generated on the positive side of the wave F depending on the direction of movement, and the distance calculation circuit 26 measures the pulse P1 generated at the zero cross point of the wave E. It calculates the amount and direction of movement. 12 is a motor for moving the stage.
しかるに、この方法では受光器からの干渉波によって得
られるパルス信号を、ステージの移動方向ごとにカウン
トするインクリメンタルな計測であるため、なんらかの
障害物が光路中を一瞬でも通過した場合、蓄積データが
更新されステージの位置情報を失なってしまい計測が不
能になる欠点があった。However, since this method is an incremental measurement in which pulse signals obtained by interference waves from the optical receiver are counted in each direction of stage movement, the accumulated data will be updated if any obstacle passes through the optical path even momentarily. This has the disadvantage that the position information of the stage is lost, making measurement impossible.
また、使用しているレーザもガスレーザであるため形状
が大きく、光学系も複雑となり、装置が大型かつ高価に
なっている。Furthermore, since the laser used is a gas laser, the shape is large and the optical system is complicated, making the device large and expensive.
本発明の目的は、外乱ノイズに強くかつ、安価でコンパ
クトなレーザ測長装置を提供することにある。An object of the present invention is to provide an inexpensive and compact laser length measuring device that is resistant to disturbance noise.
上記目的を達成するため1周波数を一定の周波数範囲内
で連続的に一定の割合で増減を繰り返すように変調させ
た半導体レーザ光を用い、参照鏡と被測定物の移動鏡に
照射し、それぞれの鏡から反射してきた光をミキシング
し、これによって参照鏡の基準光路長と移動鏡の測定光
路長との差に比例したビート波を発生させ、その周期を
計測することにより測定光路の絶対距離を検出するよう
にしている。To achieve the above objective, a semiconductor laser beam modulated so that one frequency is continuously increased and decreased at a constant rate within a certain frequency range is used to irradiate the reference mirror and the moving mirror of the object to be measured, respectively. The light reflected from the mirror is mixed, thereby generating a beat wave proportional to the difference between the reference optical path length of the reference mirror and the measurement optical path length of the moving mirror, and by measuring the period of the beat wave, the absolute distance of the measurement optical path can be determined. I am trying to detect it.
したがって、障害物が光路中を一時的に通過するなどに
よってレーザ光が遮断されても、再び照射されたときに
、変調されたレーザ光によるビート波で絶対距離を検出
しているため9位置情報を失うことがなく、継続して精
密な測定が行える。Therefore, even if the laser beam is blocked by an obstacle temporarily passing through the optical path, when the laser beam is irradiated again, the absolute distance is detected using the beat wave generated by the modulated laser beam, so the position information can be obtained. Precise measurements can be made continuously without losing any data.
以下に本発明を実施例によって詳細に説明する。 The present invention will be explained in detail below using examples.
第1図は本発明のレーザ測長器の構成を示す図である。FIG. 1 is a diagram showing the configuration of a laser length measuring device according to the present invention.
1は周波数変調回路で、半導体レーザ発振器2から射出
されるレーザ光の波長を一定の割合で連続的に変調させ
る。このため、半導体レーザ発振器2への注入電流を一
定割合で連続的に変化させる。3は半導体レーザ発振器
からの射出光を平行にするコリメータレンズ、4はレー
ザ光を参照鏡5と、移動鏡6の両方に分配し、またそれ
ぞれの鏡から反射してきた光をミキシングするためのビ
ームスプリッタ、7はミキシングにより生じるビート信
号を検出する受光器、8はビート信号の周期を十分に高
い周波数のクロックを用いて訃
計数する周期係数回路、9は周期データから移動鏡の位
置を演算する距離演算回路、10は出力回路。Reference numeral 1 denotes a frequency modulation circuit that continuously modulates the wavelength of the laser light emitted from the semiconductor laser oscillator 2 at a constant rate. For this reason, the current injected into the semiconductor laser oscillator 2 is continuously changed at a constant rate. 3 is a collimator lens that makes the emitted light from the semiconductor laser oscillator parallel; 4 is a beam that distributes the laser light to both the reference mirror 5 and the movable mirror 6, and also mixes the light reflected from each mirror. Splitter, 7 is a light receiver that detects the beat signal generated by mixing, 8 is a period coefficient circuit that counts the period of the beat signal using a sufficiently high frequency clock, and 9 is used to calculate the position of the movable mirror from the period data. A distance calculation circuit, 10 is an output circuit.
11は移動ステージ、12はステージ移動用モータであ
る。11 is a moving stage, and 12 is a motor for moving the stage.
以下その動作について説明する。The operation will be explained below.
半導体レーザ発振器2からレーザ光を射出させ。Laser light is emitted from the semiconductor laser oscillator 2.
歳
周波数変調回路1からの注入電會を半導体レーザ光の周
波数が急激に変化するモードホップを起こさない周波数
範囲内(0,1%以下)で直線的たとえば三角波状に変
化させると、注入電流に比例して、半導体レーザ光の周
波数が変化し1次式(1)で示される周波数fで周波数
変調される。When the injection current from the frequency modulation circuit 1 is varied linearly, for example in a triangular waveform, within a frequency range (0.1% or less) that does not cause mode hops in which the frequency of the semiconductor laser light changes rapidly, the injection current changes. Proportionally, the frequency of the semiconductor laser light changes and is frequency modulated at a frequency f expressed by linear equation (1).
r= fo+ tt ・・・
・・・・・・(1)(ただしf。は変調開始点の周波数
、iは周波数変化率、tは時間)
この、半導体レーザ光は、コリメータレンズ3を通りビ
ームスプリッタ4で2つに分岐され、方向が90°曲げ
られた一方の光ビームは基準光路の参照鏡5に当って反
射され、ビームスプリッタ4を通り、受光器7に入射す
る。この基準光Aは次式(2)で表わされる。r=fo+tt...
......(1) (where f. is the frequency of the modulation start point, i is the frequency change rate, and t is time) This semiconductor laser light passes through the collimator lens 3 and is split into two by the beam splitter 4. One of the light beams whose direction is bent by 90 degrees is reflected by the reference mirror 5 in the standard optical path, passes through the beam splitter 4, and enters the light receiver 7. This reference light A is expressed by the following equation (2).
Δ=A1exp (−2πj (fo+4t) t)
・+−+・−・(2)(ただしAIは初期の基準
光の強度)
また、ビームスプリッタ4を通過した他方の光ビームは
、移動鏡6に当って反射し、ビームスプリッタ4で方向
が90°曲げられて受光器7に入射される。この測定光
Bは基準光Aに対する時間遅れをτ、光路差をRとすれ
ば次式(3)で表わされる。Δ=A1exp (-2πj (fo+4t) t)
・+−+・−・(2) (However, AI is the intensity of the initial reference light) The other light beam that passed through the beam splitter 4 hits the movable mirror 6 and is reflected, and the direction is changed by the beam splitter 4. The light is bent by 90 degrees and enters the light receiver 7. This measurement light B is expressed by the following equation (3), where τ is the time delay with respect to the reference light A, and R is the optical path difference.
B=Biexp [2πj (f+f (t r)
)×(t−τ)] ・・・・・・・・
・(3)(ただし、Bは初期の測定光強度、τ=2R/
C,Cは光速)
受光器7では基準光Aと測定光Bがミキシングる。B=Biexp [2πj (f+f (t r)
)×(t-τ)] ・・・・・・・・・
・(3) (where B is the initial measurement light intensity, τ=2R/
C and C are the speeds of light) In the light receiver 7, the reference light A and the measurement light B are mixed.
V1= l A+B l =AI +B1 +
2 AIBtCos (2tt (fr +lr t、
rτ2) ) ・===・・I4)ただし、
?τ2<<frで、無視でき、また。V1= l A+B l =AI +B1 +
2 AIBtCos (2tt (fr +lr t,
rτ2) ) ・===...I4) However,
? Since τ2<<fr, it can be ignored.
(4)式の交流分のみをとり出すと、受光器の出力v2
は次式(5)の信号となる。If we take out only the alternating current component of equation (4), the output of the photodetector v2
becomes the signal of the following equation (5).
V2= 2AIBICos [2x (fr +fr
t) )・・・・・・・・・(5)
(5)式の第2項目がビート信号の周波数fbとなり次
式(6)で表わされる。V2= 2AIBICos [2x (fr +fr
(5) The second item in equation (5) is the frequency fb of the beat signal, which is expressed by the following equation (6).
化=i−τ=i・2 R/C・・・・・・・・・(6)
(6)式かられかるようにビート周波数は光路差Rに比
例し、 R=c−rb/2iで表わされる。= i−τ=i・2 R/C・・・・・・・・・(6)
As can be seen from equation (6), the beat frequency is proportional to the optical path difference R, and is expressed as R=c-rb/2i.
しかし、ビート信号の周波数fbを計数する場合。However, when counting the frequency fb of the beat signal.
周波数偏位量をΔFとすればC/(4・ΔF)の量子化
誤差を生じ、ΔFが50GHzの場合はこの量子化誤差
が1.5mmになり、大きな誤差値となる。If the amount of frequency deviation is ΔF, a quantization error of C/(4·ΔF) will occur, and if ΔF is 50 GHz, this quantization error will be 1.5 mm, which is a large error value.
このため1周波数fbを計数するかわりに、ビート信号
の周期Tb (= 1 /fb)を計測し、この周期デ
ータを距離演算回路9に与え、R=C/2?パTbによ
り、光路差Rを演算して出力回路10を介して距離に応
じた信号を出力させる。Therefore, instead of counting one frequency fb, the period Tb (= 1 /fb) of the beat signal is measured, and this period data is given to the distance calculation circuit 9, and R=C/2? The optical path difference R is calculated by the path Tb, and a signal corresponding to the distance is outputted via the output circuit 10.
しかして、ビート周期Tcのクロックを用いて計数すれ
ばその量子化誤差ΔRは次式で表わされる。Therefore, when counting is performed using a clock having a beat period Tc, the quantization error ΔR is expressed by the following equation.
△R/R=Tc/Tb= 1/N
いま、R=10mmでN=105とすれば量子化誤差△
Rは0.1μmになる。△R/R=Tc/Tb= 1/N Now, if R=10mm and N=105, the quantization error is △
R becomes 0.1 μm.
したがって、クロック周期Tcを、光路差Rが最大のと
きのビート周期Tbの1/N(たとえばN=10’〜1
05に相当するようにしておけば量子化誤差△Rを小さ
な値に保持でき精度の良い測定ができる。Therefore, the clock period Tc is set to 1/N of the beat period Tb when the optical path difference R is maximum (for example, N=10' to 1
If the value is set to correspond to 05, the quantization error ΔR can be kept at a small value and accurate measurement can be performed.
本発明の他の応用例を第2図に示す。Another example of application of the present invention is shown in FIG.
この応用例はビームスプリッタ4と移動鏡6との間の光
路に定偏波光ファイバ13を設け、その端を移動鏡に対
向して固定させるようにしである。In this application example, a polarization-constant optical fiber 13 is provided in the optical path between the beam splitter 4 and the movable mirror 6, and its end is fixed opposite to the movable mirror.
定偏波光ファイバは光の位相情報を伝達でき、移動鏡の
位置をビームスプリッタに対向させる必要がなく、移動
ステージと光学系とを自由に配置することができる。The constant polarization optical fiber can transmit optical phase information, and there is no need to position the movable mirror to face the beam splitter, allowing the movable stage and optical system to be freely arranged.
なお、移動ステージを離すことにより測定光路が長くな
ると、ビート周期が短くなり1周期計数クロックとの比
から量子化誤差が増大する恐れがあるが、基準光路にも
定偏波光ファイバを用いて。Note that if the measurement optical path is lengthened by separating the movable stage, the beat period will shorten and there is a risk that the quantization error will increase due to the ratio with the one-period counting clock, but a constant polarization optical fiber is also used for the reference optical path.
その先端部に全反射させるためのコーティング14を施
し、前記測定光路の定偏波光ファイバと同程度の長さに
することによってビート周波数を下げ。A coating 14 is applied to the tip of the optical fiber for total reflection, and the beat frequency is lowered by making the optical fiber as long as the polarization constant optical fiber of the measurement optical path.
量子化誤差の増大を防止することができる。It is possible to prevent quantization errors from increasing.
このように1本発明によるとモードホップを起さない一
定範囲内で連続的に周波数変調した半導体レーザ光を用
い、距離に比例したビート信号の周期から絶対距離を演
算導出するため、たとえ障害物が光路中を一時的に通過
しても位置情報を失うことはなく9周期を計測するため
、測定クロックの周期を小さくして量子化誤差を小さく
することができ、精密な測定を行うことができ、さらに
。In this way, according to the present invention, the absolute distance is calculated and derived from the period of the beat signal proportional to the distance using a semiconductor laser light that is continuously frequency-modulated within a certain range that does not cause mode hopping. Even if the sensor temporarily passes through the optical path, the position information is not lost and nine cycles are measured. Therefore, the measurement clock cycle can be shortened to reduce quantization errors, making it possible to perform precise measurements. Yes, even more.
光学系も簡単であるため、小形で安価な測長装置を提供
できる効果がある。Since the optical system is simple, it is possible to provide a compact and inexpensive length measuring device.
第1図は本発明のレーザ測長装置の構成を示すブロック
図、第2図は2本発明の他の実施例の要部を示すブロッ
ク図、第3図は従来のレーザ測長器の構成を示すブロッ
ク図、第4図は従来装置による干渉光の波形とパルスの
タイムチャートである。
1は周波数変調回路、2は半導体レーザ発振器。
4はビームスプリッタ、5は参照鏡、6は移動鏡。
7は受光器、8は周期計数回路、9は距離演算回路、1
3は定偏波光ファイバを示す。
第 1 図
第 2 圓
第4図
円 ゛Fig. 1 is a block diagram showing the configuration of a laser length measuring device of the present invention, Fig. 2 is a block diagram showing main parts of another embodiment of the present invention, and Fig. 3 is a block diagram showing the configuration of a conventional laser length measuring device. FIG. 4 is a block diagram showing a waveform of interference light and a time chart of pulses in a conventional device. 1 is a frequency modulation circuit, and 2 is a semiconductor laser oscillator. 4 is a beam splitter, 5 is a reference mirror, and 6 is a moving mirror. 7 is a light receiver, 8 is a period counting circuit, 9 is a distance calculation circuit, 1
3 indicates a constant polarization optical fiber. Figure 1 Figure 2 Circle Figure 4 Circle ゛
Claims (1)
ポップを起さない範囲で周波数を連続的に一定割合の増
減を繰り返すように変調させた半導体レーザ光を2方向
に分岐し、一方の光ビームを基準光路端に設けた参照鏡
に他方の光ビームを被測定物に固定した反射鏡に照射し
て、それぞれの反射光をミキシングし、光の干渉によっ
て発生するビート波の周期により前記反射鏡の距離を演
算することを特徴とするレーザ測長装置。In a length measuring device that uses optical interference of laser light, a semiconductor laser light whose frequency is modulated so that the frequency is continuously increased or decreased by a certain percentage within a range that does not cause mode pop is split into two directions, and one light is The beam is irradiated onto a reference mirror installed at the end of the reference optical path, and the other light beam is irradiated onto a reflecting mirror fixed to the object to be measured, and the respective reflected lights are mixed. A laser length measuring device characterized by calculating the distance between mirrors.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10284787A JPS63266302A (en) | 1987-04-24 | 1987-04-24 | Length measuring instrument by laser |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10284787A JPS63266302A (en) | 1987-04-24 | 1987-04-24 | Length measuring instrument by laser |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS63266302A true JPS63266302A (en) | 1988-11-02 |
Family
ID=14338341
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP10284787A Pending JPS63266302A (en) | 1987-04-24 | 1987-04-24 | Length measuring instrument by laser |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS63266302A (en) |
-
1987
- 1987-04-24 JP JP10284787A patent/JPS63266302A/en active Pending
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