Claims
- 1. A position detection apparatus comprising:
- a substrate on which is formed a diffraction grating including a plurality of diffraction-component elements extending in a predetermined direction perpendicular to a direction of arrangement;
- an alignment optical system including means for applying a pair of coherent light beams to said diffraction grating from different directions and means for photo-electrically detecting the intensity of interference fringes formed by diffracted light generated by each of said coherent light beams on said diffraction grating; and
- stop means having an opening with an edge inclined with respect to a direction corresponding to said predetermined direction and positioned in a conjugate relationship with said substrate in said alignment optical system.
- 2. A position detection apparatus according to claim 1, wherein said opening of said stop means has at least a pair of inclined edges which confront each other.
- 3. A position detection apparatus according to claim 2, wherein said opening of said stop means is in the form of a parallelogram shape.
- 4. A position detection apparatus according to claim 1, wherein said stop means is formed so as to meet the following condition: ##EQU42## where the inclination of said edge of said opening is .theta., the pitch of said interference fringes formed on said stop means is P.sub.FS, the pitch of said diffraction grating is P.sub.WM, the length of an edge of said opening of said stop means extending in a direction corresponding to said direction of arrangement of said diffraction grating is W, the length of said edge of said opening of said stop means extending in a direction corresponding to a groove of said diffraction grating is h and allowable detected error on said substrate is X.sub.WM.
- 5. A position detection apparatus according to claim 1 further comprising light shield means disposed in said optical path at a position closer to said substrate than the position of said stop means for the purpose of shielding diffracted light generated from said edge of said opening of said stop means.
- 6. A position detection apparatus according to claim 1, wherein said stop means is formed so as to meet the following condition: ##EQU43## where the inclination of said edge of said opening is .theta., the pitch of said interference fringes formed on said stop means is P.sub.FS, the pitch of said diffraction grating is P.sub.WM, the length of an edge of said opening of said stop means extending in a direction corresponding to said direction of arrangement of said diffraction grating is W, the length of said edge of said opening of said stop means extending in a direction corresponding to a groove of said diffraction grating is h and allowable detected error on said substrate is X.sub.WM.
- 7. A position detection apparatus comprising:
- a substrate on which a diffraction grating is formed;
- an alignment optical system including means for applying a pair of coherent light beams to said diffraction grating from different directions and means for photo-electrically detecting the intensity of interference fringes formed by diffracted light generated by each of said coherent light beams on said diffraction grating; and
- stop means having an opening with a pair of edges confronting each other and having length L which meets the relationship
- L=mP.sub.FS
- where the pitch of interference fringes formed on said stop means is P.sub.FS and an integer is represented by m, said step means being positioned in a conjugate relationship with said substrate of said alignment optical system.
- 8. A position detection apparatus according to claim 7, wherein said stop means has plural pairs of edges confronting each other.
- 9. A position detection apparatus according to claim 8, wherein said opening of said stop means is in the form of a parallelogram shape.
Priority Claims (2)
Number |
Date |
Country |
Kind |
1-48295 |
Feb 1989 |
JPX |
|
1-142377 |
Jun 1989 |
JPX |
|
Parent Case Info
This is a division of application Ser. No. 649,340 (U.S. Pat. No. 5,070,250) filed Feb. 1, 1991, which is a continuation of application Ser. No. 482,557 filed Feb. 21, 1990 (abandoned).
US Referenced Citations (6)
Foreign Referenced Citations (2)
Number |
Date |
Country |
62-261003 |
Nov 1987 |
JPX |
63-283129 |
Nov 1987 |
JPX |
Divisions (1)
|
Number |
Date |
Country |
Parent |
649340 |
Feb 1991 |
|
Continuations (1)
|
Number |
Date |
Country |
Parent |
482557 |
Feb 1990 |
|