Method and device for optical distance measurement

Claim 2

Method for optical distance measurement, wherein an entry beam (4; 4a; 7; 55; 405) is diffracted at a displaceable optical measuring grating (3; 43) for generating a measuring beam (9; 4b; 58) whose phase is determined by superimposition with a reference beam (4a; 8; 57), characterized in that the reference beam (4a; 8; 57) is collinear with and polarized perpendicularly to the measuring beam (9; 4b; 58), and that the phase difference between the measuring and the reference beam occurring during the displacement of the measuring grating (3; 43) is determined by electrooptical phase compensation.

Claim 3

Method according to claim 1, characterized in that the reference beam is guided substantially along the same optical path as the measuring beam.

Claim 4

Method according to claim 1 or 2, characterized in that for generating the reference beam (8), a stationary second optical grating (2) is provided at which a beam (6) parallel to and polarized perpendicularly to the entry beam (7) is diffracted and picked up at the same diffraction angle (9) at which the measuring beam at the measuring grating (3) is generated.

Claim 5

Method according to claim 1 or 2, characterized in that the reference beam at the measuring grating is generated from a diffraction order of the entry beam which differs from the diffraction order of the measuring beam.

Claim 6

Method according to claim 4, characterized in that the measuring grating (43) is alluminated with a polarized entry beam (4a), and that the direction of polarization of the measuring beam (4b) is rotated by 90°.

Claim 7

Method according to claim 4, characterized in that a second entry beam (406) is provided which is polarized perpendicularly to the first entry beam (405) and which symmetrically thereto is incident at the same angle of incidence (0) on the measuring grating (43), and that the measuring beam and the reference beam (407) are collinear diffraction orders of the entry beam.

Claim 8

Arrangement for optical distance measurement, comprising means directing an entry beam (4; 4a; 7; 55; 405) onto a displaceable optical measuring grating (3; 43) at which a measuring beam (4b; 9; 58) is generated by diffraction, and means for determining the phase of the measuring beam by superimposition with a reference beam (4a; 8; 57), in particular for implementing the method according to claim 3, characterized in that a birefringent plate (5; 27) is provided splitting an entry beam (4) into two parallel beams (6; 7) staggered relative to each other, directing them onto the measuring grating and a second stationary grating (2), respectively, and collinearly recombining in an exit beam (10) identical diffraction orders emanating from the gratings, and that the phase difference between the measuring and the reference beam occurring during the displacement of the measuring grating is determined by means (23; 29; 30) for electrooptical phase compensation.

Claim 9

Arrangement according to claim 7, characterized in that in front of the birefringent plate (27) a collector lens (26) is provided for focusing the entry beam (4) onto the measuring gratings (43).

Claim 10

Arrangement for optical distance measurement comprising means directing an entry beam (4; 4a; 7; 55; 405) onto a displaceable optical measuring grating (3; 43) at which a measuring beam (4b; 9; 58) is generated by diffraction, and means for determining the phase of the measuring beam by superimposition with a reference beam (4a; 8; 57), in particular for implementing the method according to claim 5, characterized in that in the optical path in front of the measuring grating (43) a birefringent plate (40), a )J2 plate (41) with a center hole and a lens (42) are positioned and the distance of the lens from the measuring grating corresponds to its focal length, that the entry beam (4) extends in the optical axis, that the reflected diffracted beam of the first order after rotation of its direction of polarization in the λ/2 plate is recombined by the birefringent plate with the diffracted beam of the zeroth order, and that the phase difference between the measuring and the reference beam occurring upon displacement of the measuring grating is determined by means (23; 29; 30) for electrooptical phase compensation.

Claim 11

Arrangement for optical distance measurement comprising means directing an entry beam (4; 4a; 7; 55; 405) onto a displaceable optical measuring grating (3; 43) at which a measuring beam (4b; 9; 58) is generated by diffraction, and means for determining the phase of the measuring beam by superimposition with a reference beam (4a; 8; 57), in particular for implementing the method according to claim 5, characterized in that in the optical path of the entry beam (4) in front of the measuring grating (43) a birefringent plate (40), a Rochon prism (48) and a λ12 plate (49) are positioned, that the measuring beam diffracted in its first order at the measuring grating, prior to entering the birefringent plate (40), passes the Rochon prism (48), being diffracted to form a paraxial beam which by the birefringent plate (40) is recombined with the reflected diffracted beam of the zeroth order, and that the phase difference between the measuring and the reference beam occurring during the displacement of the measuring grating is determined by means (23; 29; 30) for electrooptical phase compensation.

Claim 12

Arrangement for optical distance measurement comprising means directing an entry beam (4; 4a; 7; 55; 405) onto a displaceable optical measuring grating (3; 43) at which a measuring beam (4b; 9; 58) is generated by diffraction, and means for determining the phase of the measuring beam by superimposition with a reference beam (4a; 8; 57), in particular for implementing the method according to claim 6, characterized in that in the optical path of the entry beam (401) a Wollaston prism (402) and a collector lens (404) are positioned for generating two entry beams symmetrically incident to the measuring grating (43), the angle of incidence (0) corresponding to the diffraction angle of the first order, and the + 1th and the -1th diffraction order serving as collinear exit beams, and that the phase difference between the measuring beam and the reference beam occurring during the displacement of the measuring grating is determined by means (23; 29; 30) for electrooptical phase compensation.

Claim 13

Arrangement for optical distance measurement comprising means directing an entry beam (4; 4a; 7; 55; 405) onto a displaceable optical measuring grating (3; 43) at which a measuring beam (4b; 9; 58) is generated by diffraction, and means for determining the phase of the measuring beam by superimposition with a reference beam, in particular for implementing the method according to claim 4, characterized in that in the optical path of the entry beam (4) along the optical axis a birefringent plate (52), a Wollaston prism (53) with a center hole and a 3X/2 plate (54) with a thinned out center portion corresponding to a ),/2 plate are provided, that the deflection angle of the Wollaston prism (53) corresponds to the diffraction angle (0) of the first order, that the zeroth diffraction order reflected at the measuring grating is recombined by the birefringent plate (52) with the first diffraction order to form a collinear exit beam (10), and that the phase difference between the measuring and the reference beam occurring during the displacement of the measuring grating is determined by means (23; 29; 30) for electrooptical phase compensation.

Claim 14

Arrangement according to claim 12, characterized in that in front of the birefringent plate (52) a collector lens (51) is positioned.

Claim 15

Arrangement according to claim 12 or 13, characterized in that the polarization of the entry beam (4) corresponds to the polarization of the ordinary (o) beam in the birefringent plate (52).

Claim 16

Arrangement according to claim 12 or 13, characterized in that the polarization of the entry beam (4) is chosen such that an ordinary (o) and an extraordinary (eo) beam are produced in the birefringent plate (52).

Claim 17

Arrangement according to any one of the claims 7 to 15, characterized in that in the path of the exit beam the following means are arranged in tandem: a Babinet Soleil compensator (64), an electrooptical modulator (66), an analyzer (67), and a photodetector (68).

Claim 18

Arrangement according to any one of the claims 7, 8 or 15, characterized in that in the path of the entry beam a λ12 plate (22), an electrooptical modulator (23) and a Babinet Soleil compensator (64) are arranged in tandem, and that in the path of the exit beam an analyzer (67) and a photodetector (68) are positioned.

Claim 19

Arrangement according to claim 16, characterized in that the means for generating the entry beam comprise a laser (60) whose axis is arranged parallel to the optical axis of the exit beam (10), and that beam deflectors (61; 62) are provided for directing the entry beam onto the measuring grating positioned perpendicularly to the axis of the exit beam.