Relative position detection means and displacement detection device

Patent metadata

Field	Value
Publication number	US-10746533-B2
Application number	US-201816053590-A
Country	US
Kind code	B2
Filing date	Aug 2, 2018
Priority date	Aug 2, 2017
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

Example position detection means and displacement detection devices are described. A relative position detection means optically detects a relative position of displacement of an object to be measured in a measuring direction, including a target mounted on the object to be measured and irradiated with light from a light source; a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the target with respect to the light; and a relative position information output unit for outputting relative position information based on displacement of the target in the measuring direction based on change of polarization state of the reflected light. The target includes a reflector mounted on the object to be measured and a birefringent member on the reflector and having a thickness changing from a tip to a base end along the measuring direction.

First claim

The invention claimed is:

1. A relative position detection means for optically detecting a relative position of displacement of an object to be measured in a measuring direction, comprising:
a target mounted on the object to be measured and irradiated with light from a light source;
a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the target with respect to the light; and
a relative position information output unit for outputting relative position information based on displacement of the target in the measuring direction based on change of polarization state of the reflected light received at the light receiver for detection of relative position,
wherein the target comprises:
a reflector mounted on the object to be measured; and
a birefringent member provided on the reflector and having a thickness changing from a tip to a base end along the measuring direction,
the birefringent member is configured such that tip side of a bottom surface is rotatable with respect to the reflector with base end side of the bottom surface as a center.

2. The relative position detection means according to claim 1 , wherein the light receiver for detection of relative position detects a change of polarization state of the reflected light along with movement of the target in the measuring direction,
the relative position information output unit outputs the relative position information of the target based on a signal obtained by photoelectric conversion of a change of polarization state of the reflected light.

3. The relative position detection means according to claim 1 , wherein the light receiver for detection of relative position comprises:
a beam splitter for splitting the reflected light into two;
a first polarizing beam splitter for transmitting P component and reflecting S component of one reflected light split by the beam splitter;
a first light receiving element for receiving transmitted light of the first polarizing beam splitter;
a second light receiving element for receiving reflected light of the first polarizing beam splitter;
a second polarizing beam splitter for transmitting P component and reflecting S component of another reflected light split by the beam splitter;
a quarter wavelength plate interposed between the beam splitter and the second polarizing beam splitter;
a third light receiving element for receiving reflected light of the second polarizing beam splitter; and
a fourth light receiving element for receiving transmitted light of the second polarizing beam splitter.

4. The relative position detection means according to claim 1 , wherein the birefringent member is configured by arranging a plurality of different members in parallel along the measuring direction, or is configured by laminating a plurality of different members along incident direction of the light.

5. The relative position detection means according to claim 4 , wherein the birefringent member is configured by laminating a plurality of members with different crystal axis direction along incident direction of the light.

6. The relative position detection means according to claim 1 , wherein a correction prism is provided at any of front stage side or rear stage side of the birefringent member with respect to the light source.

7. The relative position detection means according to claim 1 , wherein two light receivers for detection of relative position are arranged along the measuring direction, and it is arranged to estimate and correct wavelength variation amount based on a difference of phase fluctuation amount of polarization state of the reflected light detected by each light receiver for detection of relative position.

8. The relative position detection means according to claim 1 , wherein a polarizing plate is further arranged between the light source and the birefringent member.

9. The relative position detection means according to claim 1 , wherein an azimuth correction unit for performing azimuth correction to the reflected light is further arranged at the light receiver for detection of relative position.

10. A displacement detection device for optically detecting a displacement in a measuring direction of an object to be measured, comprising:
a light source for irradiating light;
a light source side beam splitter for splitting the light from the light source into two;
a relative position detection means for detecting relative position of the displacement of the object to be measured in the measuring direction based on a change of polarization state of reflected light with respect to one light split by the light source side beam splitter;
an absolute position detection means for detecting absolute position of the displacement of the object to be measured in the measuring direction based on a change of light quantity of reflected light with respect to another light split by the light source side beam splitter,
wherein the absolute position detection means and the relative position detection means are arranged on in-line with respect to the measuring direction of the object to be measured,
wherein the relative position detection means comprises:
a target mounted on the object to be measured and irradiated with light from the light source;
a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the target with respect to the light; and
a relative position information output unit for outputting relative position information based on the displacement of the target in the measuring direction based on a change of polarization state of the reflected light received at the light receiver for detection of relative position,

wherein the target comprises:
a reflector mounted on the object to be measured; and
a birefringent member provided on the reflector and having a thickness changing from a tip to a base end along the measuring direction,
the birefringent member is configured such that tip side of a bottom surface is rotatable with respect to the reflector with base end side of the bottom surface as a center.

11. The displacement detection device according to claim 10 , wherein the light receiver for detection of relative position detects a change of polarization state of the reflected light along with movement of the target in the measuring direction, and
the relative position information output unit outputs the relative position information of the target based on a signal obtained by photoelectric conversion of a change of polarization state of the reflected light.

12. The displacement detection device according to claim 10 , wherein the absolute position detection means comprises:
a prism mounted on the object to be measured and irradiated with the light from the light source via a mirror;
a light receiver for detection of absolute position for receiving light by changing light quantity of reflected light at the prism with respect to the light; and
an absolute position information output unit for outputting absolute position information based on displacement of the prism in the measuring direction based on a change of the light quantity of the reflected light received at the light receiver for detection of absolute position,
wherein at top surface side of the prism, a variable reflection film, in which reflection characteristic varies along the measuring direction, is provided.

Assignees

• Dmg Mori Co Ltd

Inventors

• Okuyama Shun
• Suzuki Akinori

Classifications

• G01D5/285 Primary

  using a movable mirror · CPC title

• G01D5/344

  using polarisation (G01D5/35303 takes precedence) · CPC title

• G01D5/30

  the beams of light being detected by photocells · CPC title

• G02B27/283

  used for beam splitting or combining · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title