Encoder scale, encoder, drive apparatus, and stage apparatus

Patent metadata

Field	Value
Publication number	US-10444036-B2
Application number	US-201615086294-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Oct 2, 2013
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

An encoder scale S includes a substrate 10 that rotates about a rotation axis AX and has an optical pattern along a rotation direction D on a first surface 10a crossing the rotation axis AX, of the substrate 10. The scale S also includes a first magnet M1 that is disposed on a second surface 10b of the substrate 10 different from the first surface 10a and has different magnetic poles (N-pole M1n, S-pole M1s) set therein with the rotation axis AX therebetween and a second magnet M2 that is disposed on the first surface 10a and generates magnetic fields with the N-pole M1n and S-pole M1s of the first magnet M1.

First claim

What is claimed is:

1. An encoder scale comprising:
a substrate configured to rotate about a rotation axis and that has a first surface crossing the rotation axis and a second surface different from the first surface;
an optical pattern formed on the first surface;
a first magnet disposed on the second surface, the first magnet having different magnetic poles set therein with the rotation axis therebetween; and
a second magnet or magnetic yoke that (i) is disposed on the first surface, (ii) is disposed between the rotation axis and the optical pattern, and (iii) is configured to generate magnetic fields with the magnetic poles of the first magnet.

2. The encoder scale of claim 1 , wherein the first magnet is disposed so as to partially protrude from a peripheral edge of the substrate.

3. The encoder scale of claim 1 , further comprising a fixed unit that is disposed on the second surface and that is configured to be fixed to a rotating member to be measured,
wherein the first magnet is formed in a circle and disposed so as to surround the fixed unit.

4. The encoder scale of claim 1 , wherein the second magnet is in the shape of a disc, a cone, or a truncated cone about the rotation axis.

5. The encoder scale of claim 4 , wherein the second magnet is disposed in such a manner that magnetic poles thereof differ from the magnetic poles of the first magnet in a direction of the rotation axis.

6. The encoder scale of claim 4 , wherein a back yoke is disposed between the second magnet and the substrate.

7. The encoder scale of claim 1 , wherein the magnetic yoke is magnetically connected to the magnetic poles of the first magnet, magnetic poles of the magnetic yoke differing from the magnetic poles of the first magnet in a direction of the rotation axis.

8. The encoder scale of claim 7 , wherein the magnetic yoke and the first magnet are magnetically connected through a magnetic circuit formed on the substrate.

9. The encoder scale of claim 1 , wherein the first magnet has a larger volume than the second magnet or the magnetic yoke.

10. The encoder scale of claim 1 , wherein the optical pattern is a light reflection pattern.

11. An encoder scale comprising:
a substrate configured to rotate about a rotation axis and that has a first surface and a second surface, the second surface being a back side of the first surface;
an optical pattern formed on the second surface;
a first magnet disposed on the first surface; and
a second magnet or magnetic yoke that (i) is disposed on the second surface, (ii) is disposed between the rotation axis and the optical pattern, and (iii) generates a magnetic field with the first magnet, the magnetic field being detectable by a magnetic detector.

12. An encoder comprising:
the encoder scale of claim 1 , the optical pattern of the encoder scale being disposed in a rotation direction of the rotation axis, and the encoder scale being configured to make a change in the magnetic field at least once during one rotation about the rotation axis;
a light detector configured to detect light through the optical pattern; and
a magnetic detector configured to detect the change in the magnetic field.

13. An encoder comprising:
a scale configured to rotate about a rotation axis and that has a first surface and a second surface, the second surface being a back side of the first surface;
a first magnet disposed on the first surface;
an optical pattern formed on the second surface;
a second magnet or magnetic yoke that is disposed on the second surface and between the rotation axis and the optical pattern; and
a magnetic detector configured to detect a magnetic field generated between the first magnet and the second magnet or magnetic yoke.

14. The encoder of claim 13 , wherein an outer diameter of the second magnet or magnetic yoke is different from an outer diameter of the first magnet.

15. The encoder of claim 13 , wherein
the magnetic detector is disposed so as to be opposed to the second surface, and
an outer diameter of the second magnet or magnetic yoke is smaller than an outer diameter of the first magnet.

16. The encoder of claim 15 , wherein the magnetic detector is disposed outside the outer diameter of the second magnet or magnetic yoke in a radial direction of the scale.

17. The encoder of claim 13 , wherein:
the scale comprises a substrate configured to rotate about the rotation axis, and
the first magnet is disposed on the substrate in such a manner that an outer diameter thereof protrudes from a peripheral edge of the substrate.

18. The encoder of claim 13 , wherein the optical pattern is formed so as to be closer to an outer circumference of the second surface than the second magnet or magnetic yoke.

19. A drive apparatus comprising:
a rotating member;
a drive unit configured to rotate the rotating member; and
the encoder of claim 13 , fixed to the rotating member and configured to detect position information of the rotating member.

20. A stage apparatus comprising:
a moving object; and
the drive apparatus of claim 19 , which is configured to move the moving object.

Assignees

• Nikon Corp

Inventors

• MITSUHASHI Yuichi

Classifications

• G01D5/3473

  Circular or rotary encoders · CPC title

• G01D5/145

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01D5/34715

  Scale reading or illumination devices · CPC title

• G01D5/34792 Primary

  with only digital scales or both digital and incremental scales · CPC title

• G01D5/20 Primary

  by varying inductance, e.g. by a movable armature · CPC title