Rotary encoder using reflected light

Claim 2

An encoder arranged to detect the state of movement between a diffraction grating and a light incident on the diffraction grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto a movable diffraction grating to be diffracted; reflecting means for reflecting a particular order of diffracted light beams with exit from the diffraction grating and have a phase which varies with the rotation thereof, said reflecting means including a lens, having an optical axis, arranged in the light paths of said diffracted light beams and a reflecting surface disposed at a position on which said diffracted light beams are focused by said lens, and said reflecting means directing said diffracted light beams back to the position on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of the particular order of diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating and mutually interfering so as to detect the state of movement of the diffraction grating.

Claim 3

An encoder as claimed in claim 1, wherein said lens is a gradient index lens having flat surfaces opposite to each other.

Claim 4

An encoder according to claim 2, wherein said gradient index lens has said reflecting surface formed in one of said flat surfaces thereof.

Claim 5

An encoder according to claim 3, wherein said reflecting surface is formed only near a center portion of said flat surface.

Claim 6

An encoder as claimed in claim 1 further includes a beam limiting mask disposed at the front of said reflecting surface.

Claim 7

An encoder according to claim 1, wherein said directing means directs a plurality of light beams onto the diffraction grating.

Claim 8

An encoder as claimed in claim 1, wherein said reflecting means is movable along an optical path of said particular order of diffracted light beams entering said reflecting means, and the difference between the optical path lengths of said light beams forming said interference fringes is adjusted by movement of said reflecting means.

Claim 9

An encoder arranged to detect the state of movement between a diffraction grating and a light incident on the diffraction grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto a movable diffraction grating to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams with exit from the diffraction grating and vary with the rotation thereof, said reflecting means including a lens, having an optical axis, arranged in the light path of said diffracted light beams and a reflecting surface reflecting said diffracted light beams converged by said lens, and said reflecting means directing said diffracted light beams to the positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of said particular order of said diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating to be mutually interfered so as to detect the state of movement of the diffraction grating.

Claim 10

An encoder arranged to detect the state of movement between a diffraction grating and a light incident on the diffraction grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto a movable diffraction grating to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams with exit from the diffraction grating and vary with the rotation thereof, said reflecting means including a lens, having an optical axis, arranged in the light path of said diffracted light beams and a reflecting surface reflecting said diffracted light beams converged by said lens, and said reflecting means directing said diffracted light beams to the positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of said particular order of said diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating to be mutually interfered so as to detect the state of movement of the diffraction grating.

Claim 11

An encoder arranged to detect the state of movement of a grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto different positions on a movable diffraction grating to be diffracted; first and second reflecting means for reflecting a particular order of diffracted light beams which exit from the diffraction grating and have a phase which varies with the rotation thereof, said first and second reflecting means each including a lens having an optical axis, and being arranged in the light path of said diffracted light beams and a respective reflecting surface disposed at positions where said diffracted light beams are focused by said respective lens, and said first and second reflecting means directing said diffracted light beams to positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said first and second reflecting means through cooperation between said respective lens and said respective reflecting surface, said first and second reflecting means being arranged at different positions from each other so that the respective light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of the respective lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from each of the different positions to mutually interfere so as to detect the state of movement of the diffraction grating.

Claim 12

An encoder arranged to detect the state of movement of a grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto different positions on a movable diffraction grating to be diffracted; first and second reflecting means for reflecting a particular order of diffracted light beams which exit from the diffraction grating and have a phase which varies with the rotation thereof, said first and second reflecting means each including a lens having an optical axis, and being arranged in the light path of said diffracted light beams and a respective reflecting surface disposed at positions where said diffracted light beams are focused by said respective lens, and said first and second reflecting means directing said diffracted light beams to positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said first and second reflecting means through cooperation between said respective lens and said respective reflecting surface, said first and second reflecting means being arranged at different positions from each other so that the respective light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of the respective lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from each of the different positions to mutually interfere so as to detect the state of movement of the diffraction grating.

Claim 13

An encoder as claimed in claim 9, wherein said first and second reflecting means are movable along an optical path of said particular order of diffracted light beams entering said first and second reflecting means, and the difference between optical path lengths of said light beams forming said interference fringes is adjusted by movement of said first and second reflecting means.

Claim 14

An encoder according to claim 9, wherein each said lens is a gradient index lens having flat surfaces opposite to each other, and each said reflecting surface is formed on one of said flat surfaces of each respective lens.

Claim 15

A rotary encoder arranged to detect the state of rotation of an object, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; optical means for directing the plurality of light beams onto a diffraction grating formed along the direction of rotation of a rotating object to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams which exit from the diffraction grating and have a phase which varies with the rotation thereof, said reflecting means including a lens, having an optical axis, arranged in the light path of said diffracted light beams and a reflecting surface disposed at a position on which said diffracted light beams are focused by said lens, and said reflecting means directing said diffracted light beams back to the position on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating and mutually interfering so as to detect the state of rotation of the rotating object.

Claim 16

A rotary encoder arranged to detect the state of rotation of an object, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; optical means for directing the plurality of light beams onto a diffraction grating formed along the direction of rotation of a rotating object to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams which exit from the diffraction grating and have a phase which varies with the rotation thereof, said reflecting means including a lens, having an optical axis, arranged in the light path of said diffracted light beams and a reflecting surface disposed at a position on which said diffracted light beams are focused by said lens, and said reflecting means directing said diffracted light beams back to the position on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating and mutually interfering so as to detect the state of rotation of the rotating object.

Claim 17

A rotary encoder as claimed in claim 12 further includes a beam limiting mask disposed in front of said reflecting surface.

Claim 18

A rotary encoder as claimed in claim 12, wherein: said plurality of light beams are made incident on different positions of the diffraction grating.

Claim 19

An encoder as claimed in claim 12, wherein said reflecting means is movable along an optical path of said particular order of diffracted light beams entering said reflecting means, and the difference between the optical path lengths of said light beams forming said interference fringes is adjusted by movement of said reflecting means.

Claim 20

A rotary encoder according to claim 12, wherein said lens is a gradient index lens having flat surfaces opposite to each other and said reflecting surface is formed on one of said flat surfaces of said lens.

Claim 21

A rotary encoder for detecting the state of rotation of an object comprising: light source means for supplying a light beam; splitting means for splitting the light beam into a plurality of beams of light which are directed onto different positions on a diffraction grating formed along the direction of rotation of a rotating object to be diffracted; first and second reflecting means for reflecting a particular order of diffracted light beams which exit from the diffraction grating and vary with the rotation thereof, said first and second reflecting means each including a lens having an optical axis, and being arranged in the light path of said diffracted light beams and a respective reflecting surface disposed at a position where said diffracted light beams are focused by said respective lens, and said first and second reflecting means directing said diffracted light beams to positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said first and second reflecting means through cooperation between said respective lens and said respective reflective surface, said first and second reflecting means being arranged at different positions from each other so that the respective light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of the respective lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said rediffracted light beams exiting from the different positions to be mutually interfered so as to detect the state of rotation of the rotating object.

Claim 22

A rotary encoder for detecting the state of rotation of an object comprising: light source means for supplying a light beam; splitting means for splitting the light beam into a plurality of beams of light which are directed onto different positions on a diffraction grating formed along the direction of rotation of a rotating object to be diffracted; first and second reflecting means for reflecting a particular order of diffracted light beams which exit from the diffraction grating and vary with the rotation thereof, said first and second reflecting means each including a lens having an optical axis, and being arranged in the light path of said diffracted light beams and a respective reflecting surface disposed at a position where said diffracted light beams are focused by said respective lens, and said first and second reflecting means directing said diffracted light beams to positions on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said first and second reflecting means through cooperation between said respective lens and said respective reflective surface, said first and second reflecting means being arranged at different positions from each other so that the respective light path of the particular order of said diffracted light beams is substantially parallel with the optical axis of the respective lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said rediffracted light beams exiting from the different positions to be mutually interfered so as to detect the state of rotation of the rotating object.

Claim 23

An encoder as claimed in claim 17, wherein said first and second reflecting means are movable along an optical path of said particular order of diffracted light beams entering said first and second reflecting means, and the difference between optical path lengths of said light beams forming said interference fringes is adjusted by movement of said first and second reflecting means.

Claim 24

A rotary encoder according to claim 17, wherein each said lens is a gradient index lens having flat surfaces opposite to each other, and each said reflecting surface is formed on one of said flat surfaces of each respective lens.

Claim 25

A rotary encoder as claimed in claim 17, wherein said light source means includes a semiconductor laser.

Claim 26

A rotary encoder as claimed in claim 17, wherein said splitting means is a polarizing beam splitter.

Claim 27

A rotary encoder as claimed in claim 21, wherein at least one quarter-wave plate is present in the optical paths of the split beams generated by said polarizing beam splitter.

Claim 28

A rotary encoder according to claim 17, wherein one of said first and second reflecting means is adapted to be movable along said optical axis.

Claim 29

An encoder arranged to detect the state of movement between a diffraction grating and a light incident on the diffraction grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto a movable diffraction grating to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams which exit from the diffraction grating and have a phase which varies with the movement thereof, said reflecting means including a lens, having an optical axis, arranged in the light paths of said diffracted light beams and a reflecting surface disposed at a position on which said diffracted light beams are focused by said lens, and said reflecting means directing said diffracted light beams back to the position on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of the particular order of diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating and mutually interfering so as to detect the state of movement of the diffraction grating.

Claim 30

An encoder arranged to detect the state of movement between a diffraction grating and a light incident on the diffraction grating, comprising: light source means for supplying light; splitting means for splitting the light into a plurality of beams of light; directing means for directing the plurality of light beams onto a movable diffraction grating to be diffracted; reflecting means for reflecting a particular order of said diffracted light beams which exit from the diffraction grating and have a phase which varies with the movement thereof, said reflecting means including a lens, having an optical axis, arranged in the light paths of said diffracted light beams and a reflecting surface disposed at a position on which said diffracted light beams are focused by said lens, and said reflecting means directing said diffracted light beams back to the position on the diffraction grating where said diffracted light beams exit so as to be re-diffracted, wherein said diffracted light beams travel along substantially the same light path as the incident light received by said reflecting means through cooperation between said lens and said reflecting surface, said reflecting means being arranged so that the light path of the particular order of diffracted light beams is substantially parallel with the optical axis of said lens; and photoelectric conversion means for photoelectrically converting interference fringes formed by said re-diffracted light beams exiting from the diffraction grating and mutually interfering so as to detect the state of movement of the diffraction grating.