JP2023133433A5

JP2023133433A5 -

Info

Publication number: JP2023133433A5
Application number: JP2023121912A
Authority: JP
Filing date: 2023-07-26
Publication date: 2024-04-01

Description

第１の発明の変位検出装置は、光路長差により生じる複数の干渉強度ピークを持つ、可干渉性の低いマルチモードのレーザ光源と、レーザ光源からの光を集光させるレンズと、レンズで集光され偏波保持ファイバで伝送された光を分岐するビームスプリッタと、分岐された光が照射される回折格子と、回折格子からの回折光を重ね合わせ干渉させた干渉光を受光する受光素子を備え、干渉光の強度変化から、回折格子の変位量を検出する変位検出装置であって、偏波保持ファイバのファイバ長Ｌを、直交する二つの伝搬モード経由の光による干渉光の強度がピークとなる長さ、(2ｍｎ _eff Ｌ _CAV Ｌ _beat )／λと(2(ｍ+1)ｎ _eff Ｌ _CAV Ｌ _beat )／λとの間の干渉強度がほぼ０となる長さに設定した（ただし、ｍは０以上の正の整数、ｎ _eff はレーザ光源の共振器の実効屈折率、Ｌ _CAV はレーザ光源の共振器長、Ｌ _beat は偏波保持ファイバのビート長、λは光源の波長である）。 The displacement detection device of the first invention includes a multi -mode laser light source with low coherence that has a plurality of interference intensity peaks caused by optical path length differences , a lens that focuses light from the laser light source, and a lens that focuses light from the laser light source. A beam splitter that splits the light that has been transmitted through a polarization-maintaining fiber, a diffraction grating that is irradiated with the split light, and a light receiving element that receives the interference light that is obtained by superimposing and interfering the diffracted light from the diffraction grating. This is a displacement detection device that detects the amount of displacement of a diffraction grating from changes in the intensity of interference light, and the intensity of the interference light due to light via two orthogonal propagation modes is the peak of the fiber length L of the polarization-maintaining fiber. The length was set so that the interference strength between (2mn _eff L _CAV L _beat )/λ and (2(m+1)n _eff L _CAV L _beat )/λ was almost 0 (however, , m is a positive integer greater than or equal to 0, n _eff is the effective refractive index of the resonator of the laser light source, L _CAV is the resonator length of the laser light source, L _beat is the beat length of the polarization maintaining fiber, and λ is the wavelength of the light source. be).

第２の発明の変位検出装置は、レーザ光源からの光を集光させるレンズと、偏波保持ファイバで伝送された光を分岐するビームスプリッタと、分岐された光を反射する被測定面の移動に連動して移動するターゲットミラーと、ターゲットミラーから反射された光を重ね合わせ干渉させた干渉光を受光する受光素子を備え、干渉光の強度変化から、ターゲットミラーの変位量を検出する変位検出装置において、偏波保持ファイバのファイバ長Ｌを、直交する二つの伝搬モード経由の光による干渉光の強度がピークとなる長さ、(2ｍｎ _eff Ｌ _CAV Ｌ _beat )／λと(2(ｍ+1)ｎ _eff Ｌ _CAV Ｌ _beat )／λとの間の干渉強度がほぼ０となる長さに設定した（ただし、ｍは０以上の正の整数、ｎ _eff はレーザ光源の共振器の実効屈折率、Ｌ _CAV はレーザ光源の共振器長、Ｌ _beat は偏波保持ファイバのビート長、λは光源の波長である）。
第３の発明の変位検出装置は、光を出射する可干渉距離をもつ可干渉性の低い光源と、レーザ光源からの光を集光させるレンズと、レンズで集光され偏波保持ファイバで伝送された光を分岐するビームスプリッタと、分岐された光が照射される回折格子と、回折格子からの回折光を重ね合わせ干渉させた干渉光を受光する受光素子を備え、干渉光の強度変化から、回折格子の変位量を検出する変位検出装置において、偏波保持ファイバは、レーザ光源から出射した光を偏波保持ファイバに入射した場合、偏波保持ファイバの長さＬは可干渉距離L _low と２つの偏波モードの伝搬定数の差から求められるビート長Ｌ _beat の積から光源の波長λを割った長さよりも長く、偏波保持ファイバの直交する二つの伝搬モード経由の光による干渉光の強度がほぼ０となる、レンズで集光された光を伝送する。
第４の発明の変位検出装置は、レーザ光源からの光を集光させるレンズと、レンズで集光され偏波保持ファイバで伝送された光を分岐するビームスプリッタと、分岐された光を反射する被測定面の移動に連動して移動するターゲットミラーと、ターゲットミラーから反射された光を重ね合わせ干渉させた干渉光を受光する受光素子を備え、干渉光の強度変化から、ターゲットミラーの変位量を検出する変位検出装置において、偏波保持ファイバは、レーザ光源から出射した光を偏波保持ファイバに入射した場合、偏波保持ファイバの長さＬは前記可干渉距離Ｌ _low と２つの偏波モードの伝搬定数の差から求められるビート長Ｌ _beat の積からレーザ光源の波長λを割った長さよりも長く、偏波保持ファイバの直交する二つの伝搬モード経由の光による干渉光の強度がほぼ０となる、前記レンズで集光された光を伝送する。
The displacement detection device of the second invention includes a lens that focuses light from a laser light source, a beam splitter that splits the light transmitted through a polarization-maintaining fiber, and a movement of a surface to be measured that reflects the split light. Displacement detection is equipped with a target mirror that moves in conjunction with the target mirror, and a light receiving element that receives interference light that overlaps and interferes with the light reflected from the target mirror, and detects the amount of displacement of the target mirror from changes in the intensity of the interference light. In the device, the fiber length L of the polarization-maintaining fiber is defined as the length at which the intensity of interference light due to light via two orthogonal propagation modes reaches its peak, (2mn _eff L _CAV L _beat )/λ and (2(m+ 1) The length was set so that the interference intensity between n _eff L _CAV L _beat )/λ is almost 0 (where m is a positive integer greater than or equal to 0, and n _eff is the effective refraction of the resonator of the laser light source. (L _CAV is the cavity length of the laser light source, L _beat is the beat length of the polarization maintaining fiber, and λ is the wavelength of the light source).
The displacement detection device of the third invention includes a light source with low coherence that has a coherence distance that emits light, a lens that focuses light from the laser light source, and the light that is focused by the lens and transmitted through a polarization-maintaining fiber. It is equipped with a beam splitter that splits the split light, a diffraction grating that is irradiated with the split light, and a light receiving element that receives the interference light obtained by superimposing and interfering the diffracted light from the diffraction grating. In a displacement detection device that detects the amount of displacement of a diffraction grating, when light emitted from a laser light source is input to the polarization-maintaining fiber, the length L of the polarization-maintaining fiber is the coherence length L _low The interference light is longer than the length obtained by dividing the light source wavelength λ by the product of the beat length L _beat obtained from the difference in the propagation constant of the two polarization modes, and is caused by light that has passed through two orthogonal propagation modes of the polarization-maintaining fiber. It transmits light that is focused by a lens and has an intensity of almost 0.
The displacement detection device of the fourth invention includes a lens that focuses light from a laser light source, a beam splitter that splits the light that was focused by the lens and was transmitted through a polarization-maintaining fiber, and a beam splitter that reflects the split light. Equipped with a target mirror that moves in conjunction with the movement of the surface to be measured, and a light-receiving element that receives interference light that overlaps and interferes with the light reflected from the target mirror, and detects the amount of displacement of the target mirror from changes in the intensity of the interference light. In a displacement detection device that detects a polarization-maintaining fiber, when light emitted from a laser light source is input to the polarization-maintaining fiber, the length L of the polarization-maintaining fiber is equal to the coherence length L _low and the two polarizations. It is longer than the length obtained by dividing the wavelength λ of the laser light source from the product of the beat length L _beat obtained from the difference in the propagation constants of the modes, and the intensity of the interference light due to the light via the two orthogonal propagation modes of the polarization maintaining fiber is approximately 0, the light focused by the lens is transmitted.

Claims

A multi -mode laser light source with low coherence and having multiple interference intensity peaks caused by optical path length differences ;
a lens that focuses light from the laser light source;
a beam splitter that splits the light focused by the lens and transmitted by the polarization maintaining fiber;
a diffraction grating on which the branched light is irradiated;
comprising a light receiving element that receives interference light obtained by superimposing and interfering the diffracted light from the diffraction grating,
A displacement detection device that detects a displacement amount of the diffraction grating from a change in the intensity of the interference light,
The fiber length L of the polarization maintaining fiber is defined as the length at which the intensity of interference light due to light via two orthogonal propagation modes reaches its peak, (2mn _eff L _CAV L _beat )/λ and (2(m+1) The length was set such that the interference intensity between n _eff L _CAV L _beat )/λ is almost 0 (where m is a positive integer greater than or equal to 0, and n _eff is the effective refractive index of the resonator of the laser light source. , L _CAV is the resonator length of the laser light source, L _beat is the beat length of the polarization maintaining fiber, and λ is the wavelength of the light source)
Displacement detection device.

2. The displacement detection device according to claim 1, wherein a plurality of the polarization-maintaining fibers are connected to a detachable connector, and when a plurality of fitting portions are present, the order of connection of the polarization-maintaining fibers is set so that the total length of the polarization-maintaining fibers, including the last polarization-maintaining fiber and all combinations of the polarization-maintaining fibers other than that, is a length at which the intensity of the interference light due to light passing through two orthogonal propagation modes peaks, and the interference intensity between (2mn _{eff LCAV} _L beat ) _/ λ and (2(m+1)n eff LCAV L _beat ₎ / _λ is set to be approximately zero .

A lens that focuses the light from the laser light source ,
a beam splitter that splits the light transmitted through the polarization-maintaining fiber;
a target mirror that moves in conjunction with the movement of a surface to be measured that reflects the branched light;
comprising a light receiving element that receives interference light obtained by superimposing and interfering the light reflected from the target mirror,
A displacement detection device that detects a displacement amount of the target mirror from a change in the intensity of the interference light,
The fiber length L of the polarization maintaining fiber is defined as the length at which the intensity of interference light due to light via two orthogonal propagation modes reaches its peak, (2mn _eff L _CAV L _beat )/λ and (2(m+1) The length was set such that the interference intensity between n _eff L _CAV L _beat )/λ is almost 0 (where m is a positive integer greater than or equal to 0, and n _eff is the effective refractive index of the resonator of the laser light source. , L _CAV is the resonator length of the laser light source, L _beat is the beat length of the polarization maintaining fiber, and λ is the wavelength of the light source)
Displacement detection device.

4. The displacement detection device according to claim 3, wherein a plurality of the polarization-maintaining fibers are connected to a detachable connector, and when a plurality of fitting portions are present, the total length of the polarization-maintaining fibers, including the last polarization-maintaining fiber in the connection order and all combinations of the polarization-maintaining fibers other than that, is set to a length at which the intensity of the interference light due to light passing through two orthogonal propagation modes peaks, and the interference intensity between (2mn _eff LCAV L beat )/λ and (2(m+1)n eff LCAV L _beat ₎ / λ _is set _to be _{approximately} zero .

a low-coherence light source with a coherence length that emits light;
a lens for collecting light from the light source;
a beam splitter that splits the light collected by the lens and transmitted through the polarization-maintaining fiber;
a diffraction grating on which the branched light is irradiated;
comprising a light receiving element that receives interference light obtained by superimposing and interfering the diffracted light from the diffraction grating,
In a displacement detection device that detects a displacement amount of the diffraction grating from a change in the intensity of the interference light,
In the polarization-maintaining fiber, when the light emitted from the light source is input to the polarization-maintaining fiber, the length L of the polarization-maintaining fiber is a coherence length L. _lowlow The beat length L obtained from the difference between the propagation constants of the two polarization modes and _beatbeat The light focused by the lens is longer than the product of λ divided by the wavelength λ of the light source, and the intensity of interference light due to light passing through two orthogonal propagation modes of the polarization maintaining fiber is approximately 0. to transmit
Displacement detection device.

The polarization-maintaining fibers are connected to a plurality of detachable connectors, and the length of each of the polarization-maintaining fibers is 2. ^ｍm ×L (where m is an integer greater than or equal to 0, and L is the length of the shortest polarization-maintaining fiber), and the length of each polarization-maintaining fiber should be such that there is no same combination.
Ta
The displacement detection device according to claim 5.

A lens that focuses the light from the laser light source,
a beam splitter that splits the light collected by the lens and transmitted through the polarization-maintaining fiber;
a target mirror that moves in conjunction with the movement of a measurement surface that reflects the branched light;
comprising a light receiving element that receives interference light obtained by superimposing and interfering the light reflected from the target mirror,
A displacement detection device that detects a displacement amount of the target mirror from a change in the intensity of the interference light,
When the light emitted from the laser light source is incident on the polarization-maintaining fiber, the length L of the polarization-maintaining fiber is equal to the coherence length L _lowlow and the beat length L obtained from the difference in the propagation constants of the two polarization modes. _beatbeat is longer than the product of the wavelength λ of the laser light source divided by the wavelength λ of the laser light source, and the intensity of the interference light due to the light passing through the two orthogonal propagation modes of the polarization maintaining fiber is approximately 0. transmit light
Displacement detection device.

A plurality of polarization-maintaining fibers are connected to each other by detachable connectors, and each polarization-maintaining fiber has a length of 2 ^ｍm ×L (where m is an integer greater than or equal to 0, and L is the length of the shortest polarization-maintaining fiber), and the length of each polarization-maintaining fiber was such that no combination was the same.
The displacement detection device according to claim 7.