ENCODER SCALE, ENCODER, DRIVE APPARATUS, AND STAGE APPARATUS

• US 20160209241A1
• Filed: 03/31/2016
• Published: 07/21/2016
• Est. Priority Date: 10/02/2013
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: MITSUHASHI, Yuichi
• Granted Patent: US 10,444,036 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/20 by varying inductance, e.g. by a movable armature
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders
• CPC Class Codes: G01D 5/34792 with only digital scales or both digital and incremental scales

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.

Claims

1. An encoder scale that includes a substrate configured to rotate about a rotation axis and has an optical pattern along a rotating direction on a first surface crossing the rotation axis, of the substrate, the encoder scale comprising:

a first magnet disposed on a second surface different from the first surface, of the substrate, the first magnet having different magnetic poles set therein with the rotation axis therebetween; and

a second magnet or a magnetic yoke disposed on the first surface and 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 disposed on the second surface and 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 of claim 1, wherein the second magnet or the magnetic yoke is disposed between the rotation axis and the optical pattern.

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

6. The encoder scale of claim 5, 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.

7. The encoder scale of claim 5, wherein a back yoke is disposed between the second magnet and the substrate.

8. The encoder scale of claim 4, wherein the magnetic yoke is magnetically connected to the magnetic pole of the first magnet, the magnetic pole differing from the magnetic pole of the first magnet in a direction of the rotation axis.

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

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

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

13. An encoder comprising:

an encoder scale having an optical pattern disposed in a rotation direction of a rotation axis, the encoder scale being configured to rotate about the rotation axis and to make a change in a magnetic field at least once during one rotation;

a light detector configured to detect light through the optical pattern; and

a magnetic detector configured to detect the change in the magnetic field, wherein

the encoder scale is the encoder scale of claim 1.

12. An encoder scale comprising:

a first magnet disposed on one surface of the encoder scale; and

a second magnet or a magnetic yoke disposed on another surface of the encoder scale, the other surface being a back side of the one surface, wherein

the second magnet or the magnetic yoke generates a magnetic field with the first magnet, the magnetic field being to be detected by a magnetic detector.

14. An encoder comprising:

a scale comprises;

a first magnet disposed on one surface of the scale; and

a second magnet or a magnetic yoke disposed on another surface of the scale, the other surface being a back side of the one surface; and

a magnetic detector configured to detect a magnetic field generated between the first magnet and the second magnet or the magnetic yoke.

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

16. The encoder of claim 14, wherein

the magnetic detector is disposed so as to be opposed to the other surface, and

the outer diameter of the second magnet or the magnetic yoke is smaller than the outer diameter of the first magnet.

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

18. The encoder of claim 14, wherein the scale comprises a substrate configured to rotate about a rotation axis, and

the first magnet is disposed on one surface of the substrate in such a manner that the outer diameter thereof protrudes from a peripheral edge of the substrate.

19. The encoder of claim 14, wherein the scale has an optical pattern on the other surface, the optical pattern being formed so as to be closer to an outer circumference of the other surface than the second magnet or the magnetic yoke.

20. A drive apparatus comprising:

a rotating member;

a drive unit configured to rotate the rotating member; and

an encoder fixed to the rotating member and configured to detect position information of the rotating member, wherein

the encoder is the encoder of claim 14.

21. A stage apparatus comprising:

a moving object; and

a drive apparatus configured to move the moving object, wherein

the drive apparatus is the drive apparatus of claim 20.