Displacement detecting device with controlled heat generation

Patent metadata

Field	Value
Publication number	US-10451401-B2
Application number	US-201815979645-A
Country	US
Kind code	B2
Filing date	May 15, 2018
Priority date	May 23, 2017
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

A displacement detecting device includes a first diffraction grating, a light source, a displacement detecting unit, and a light receiving unit. The displacement detecting unit includes a light flux dividing unit, a second diffraction grating, and a reference reflecting member. An incident angle of a first light flux to the first diffraction grating, a diffraction angle of the first diffraction grating, an incident angle of the first light flux to the second diffraction grating, and a diffraction angle of the second diffraction grating are angles at which a displacement amount in an optical path length of the first light flux from the light flux dividing unit to the first diffraction grating and a displacement amount in an optical path length of the first light flux from the first diffraction grating to the second diffraction grating become equal in a case where a measured member is displaced in a direction orthogonal to a measured surface.

First claim

What is claimed is:

1. A displacement detecting device comprising:
a first diffraction grating provided in a measured surface of a measured member; and
a head arranged in such a manner as to face the measured surface of the measured member,
wherein the head and the measured member are relatively movable at least in one of a direction in parallel with the measured surface and a direction orthogonal to the measured surface,
the head includes
a light source that emits light,
a displacement detecting unit that divides the light emitted from the light source into a first light flux and a second light flux and that emits the first light flux toward the first diffraction grating, and
a light receiving unit that receives the second light flux, and the first light flux that returns from the first diffraction grating through the displacement detecting unit,
the displacement detecting unit includes, as configuration elements:
a light flux dividing unit that divides the light into the first light flux and the second light flux and that emits the divided first light flux toward the first diffraction grating,
a second diffraction grating that diffracts the first light flux divided by the light flux dividing unit and diffracted by the first diffraction grating and that emits the first light flux to the first diffraction grating again,
a reference reflecting member that reflects the second light flux divided by the light flux dividing unit, and
a light flux combining unit that superposes the first light flux diffracted by the first diffraction grating and the second diffraction grating and the second light flux reflected by the reference reflecting member, and that performs emission thereof to the light receiving unit, and

an incident angle of the first light flux to the first diffraction grating, a diffraction angle of the first diffraction grating, an incident angle of the first light flux to the second diffraction grating, and a diffraction angle of the second diffraction grating are angles at which a displacement amount in an optical path length of the first light flux from the light flux dividing unit to the first diffraction grating and a displacement amount in an optical path length of the first light flux from the first diffraction grating to the second diffraction grating become equal in a case where at least one of the head and the measured member is displaced in the direction orthogonal to the measured surface.

2. The displacement detecting device according to claim 1 ,
wherein in the displacement detecting unit, an optical path length of the first light flux from the light flux dividing unit to the light flux combining unit through the first diffraction grating and an optical path length of the second light flux from the light flux dividing unit to the light flux combining unit through the reference reflecting member become equal.

3. The displacement detecting device according to claim 1 ,
wherein an incident angle θ R of the first light flux to the first diffraction grating, a diffraction angle θ of the first diffraction grating, an incident angle θ 1 of the first light flux to the second diffraction grating, and a diffraction angle θ 2 of the second diffraction grating satisfy the following expression
−cos(θ 1 +θ+θ R )/cos θ 1 +{sin(θ 1 +θ+θ R )−cos(θ 1 +θ+θ R )tan θ 1 } sin θ 2 =1  [Expression]

4. The displacement detecting device according to claim 1 ,
wherein the displacement detecting unit makes the first light flux, which is divided by the light flux dividing unit, vertically enter the first diffraction grating.

5. The displacement detecting device according to claim 1 ,
wherein diffraction by the second diffraction grating satisfies a Bragg condition.

6. The displacement detecting device according to claim 1 ,
wherein the head includes
a first displacement detecting unit that includes the displacement detecting unit and that is arranged on one side in a grating vector direction of the first diffraction grating,
a second displacement detecting unit that is arranged on the other side in the grating vector direction of the first diffraction grating with respect to the first displacement detecting unit and that includes same configuration elements as the first displacement detecting unit, and
an optical distributor that distributes the light emitted from the light source into light emitted to the first displacement detecting unit and light emitted to the second displacement detecting unit, and
the configuration elements of the second displacement detecting unit are arranged in a manner reversed in the grating vector direction of the first diffraction grating from the configuration elements of the first displacement detecting unit.

7. The displacement detecting device according to claim 1 ,
wherein the first diffraction grating has a first grating vector direction in parallel with the measured surface, and
a second grating vector direction that is in parallel with the measured surface and that intersects with the first grating vector direction,
the head includes
a first displacement detecting unit that includes the displacement detecting unit and that is arranged on one side in the first grating vector direction of the first diffraction grating,
a second displacement detecting unit that is arranged on the other side in the first grating vector direction of the first diffraction grating with respect to the first displacement detecting unit and that includes same configuration elements as the first displacement detecting unit,
a third displacement detecting unit that is arranged on one side in the second grating vector direction of the first diffraction grating and that includes same configuration elements as the first displacement detecting unit,
a fourth displacement detecting unit that is arranged on an opposite side in the second grating vector direction of the first diffraction grating with respect to the third displacement detecting unit and that includes same configuration elements as the first displacement detecting unit, and
an optical distributor that distributes the light emitted from the light source into light emitted to the first displacement detecting unit, light emitted to the second displacement detecting unit, light emitted to the third displacement detecting unit, and light emitted to the fourth displacement detecting unit,
the configuration elements of the second displacement detecting unit are arranged in a manner reversed in the first grating vector direction of the first diffraction grating from the configuration elements of the first displacement detecting unit,
the configuration elements of the third displacement detecting unit are arranged in the second grating vector direction, and
the configuration elements of the fourth displacement detecting unit are arranged in a manner reversed in the second grating vector direction of the first diffraction grating from the configuration elements of the third displacement detecting unit.

8. The displacement detecting device according to claim 1 ,
wherein the displacement detecting unit includes
a re-reflection unit that emits, toward the first diffraction grating again, the first light flux that is emitted to the first diffraction grating again by the second diffraction grating and that returns by being diffracted by the first diffraction grating, and
a third diffraction grating that diffracts the first light flux emitted to the first diffraction grating by the re-reflection unit and diffracted by the first diffraction grating and that emits the first light flux to the first diffraction grating again, and
the third diffraction grating is arranged in a manner reversed in a grating vector direction of the first diffraction grating from the se

Assignees

• Dmg Mori Co Ltd

Inventors

• Tamiya Hideaki
• Noda Kazuki

Classifications

• G02B27/4233

  having a diffractive element [DOE] contributing to a non-imaging application (diffusers having a diffractive element G02B5/0252; filters having a diffractive element G02B5/203; systems for controlling the direction of light having diffractive elements G02B26/0808; scanning systems having diffractive elements G02B26/106; beam shaping systems using diffractive optical elements G02B27/0944; beam splitting or combining systems operating by diffraction G02B27/1086) · CPC title

• G01B2290/70

  Using polarization in the interferometer · CPC title

• G01B9/02041 Primary

  characterised by particular imaging or detection techniques · CPC title

• G02B27/283

  used for beam splitting or combining · CPC title

• G01B9/02019

  contacting different points on same face of object · CPC title