Claims
- 1. An optical encoder comprising a movable scale movable relative to a surface emitting laser light source, the surface emitting laser light source for illuminating part of the movable scale, and a photodetector for receiving a light beam which has been reflected by or passed through the movable scale,wherein in a case where a distance between the movable scale and a light beam emission plane of the surface emitting laser light source along a center axis of the light beam is L, a wavelength of the light beam is λ, a scale pitch of the movable scale is p, an angle between a pitch direction of the movable scale and a plane perpendicular to the center axis of the light beam is θ, and an opening width of the surface emitting laser light source along a direction in which the pitch direction of the movable scale is projected on the plane perpendicular to the center axis of the light beam is a, a relationship, p.cos θ<a, is satisfied when L≦1.0a2/λ.
- 2. The optical encoder according to claim 1, wherein when L≦1.0a2/λ, a relationship, 0.8Lλ/a≦p.cos θ<a, is satisfied.
- 3. The optical encoder according to claim 2, wherein when 0.095a2/λ≦L≦0.11a2/λ, a relationship, 1.6Lλ/a≦p.cos θ≦2.4Lλ/a, is satisfied.
- 4. The optical encoder according to claim 2, wherein when 0.095a2/λ≦L≦0.13a2/λ, a relationship, 4.6Lλ/a≦p.cos θ≦7.4Lλ/a, is satisfied.
- 5. The optical encoder according to claim 2, wherein when 0.13a2/λ≦L≦0.21a2/λ, a relationship, 2Lλ/a≦p.cos θ≦4Lλ/a, is satisfied.
- 6. The optical encoder according to claim 2, wherein when 0.21a2/λ≦L≦0.3a2/λ, a relationship, 1.1Lλ/a≦p.cos θ≦1.6Lλ/a, is satisfied.
- 7. The optical encoder according to claim 2, wherein when 0.3a2/λ≦L≦0.6a2/λ, a relationship, 1.2Lλ/a≦p.cos θ≦a, is satisfied.
- 8. An optical encoder comprising a movable scale movable relative to a surface emitting laser light source, the surface emitting laser light source for illuminating part of the movable scale, and a photodetector for receiving a light beam which has been reflected by or passed through the movable scale,wherein in a case where a distance between the movable scale and a light beam emission plane of the surface emitting laser light source along a center axis of the light beam is L, a wavelength of the light beam is λ, a scale pitch of the movable scale is p, an angle between a pitch direction of the movable scale and a plane perpendicular to the center axis of the light beam is θ, and an opening width of the surface emitting laser light source along a direction in which the pitch direction of the movable scale is projected on the plane perpendicular to the center axis of the light beam is a, a relationship, 0.8Lλ/a≦p.cos θ<1.0Lλ/a, is satisfied when L≧1.0a2/λ.
Priority Claims (2)
Number |
Date |
Country |
Kind |
9-008377 |
Jan 1997 |
JP |
|
10-008576 |
Jan 1998 |
JP |
|
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a Continuation-in-Part application of U.S. patent application No. 09/006,668 filed Jan. 13, 1998, now abandoned the entire contents of which are incorporated herein by reference.
US Referenced Citations (5)
Foreign Referenced Citations (1)
Number |
Date |
Country |
7-306058 |
Nov 1995 |
JP |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09/006668 |
Jan 1998 |
US |
Child |
09/196055 |
|
US |