Interferential position measuring device

Abstract

Interference position measurement device comprises a light source (1), beam shaping optical element (2), measurement scale grating (3) and two scanning gratings (4.1, 4.2) so that an initial beam is split into two and then into third and fourth and possibly fifth and sixth beams of which at least two recombine in a detector plane (D). If there is a relative movement between the light source, measurement grating and scanning gratings a periodic interference band pattern is generated in the detection plane. Phase shifts are then measured with one of a number of methods. An interferential position measuring arrangement including a light source connected to a first object, which emits a beam of rays in a direction of an optical axis and an optical element arranged downstream of the light source, which converts the beam of rays emitted by the light source into an incoming beam of rays. A scale grating connected to a second object that moves relative to the first object, which splits the incoming beam of rays into a first partial beam of rays, which is propagated into a first spatial direction and a second partial beam of rays, which is propagated into a second spatial direction. A first scanning grating that causes splitting of the first partial beam of rays into third and fourth partial beams of rays and a second scanning grating that causes splitting of the second partial beam of rays into fifth and sixth partial beams of rays, wherein at least two of the third, fourth, fifth and sixth partial beams of rays meet again, and a periodically modulated interferential fringe pattern with a definite spatial interferential fringe pattern period results in a detection plane. A detection arrangement arranged in the detection plane.

Description

technical field [0001] The present invention relates to interferometers. Background technique [0002] Interferometers are well known for the precise measurement of position, which utilize the phenomenon of grating diffraction to generate high-resolution and position-dependent scanning signals. When the scale grating is moved relative to a scanning unit, phase shifts are produced in the sub-beams with deflected diffractive orders, which are proportional to the change in the optical path. In order to calculate or grasp the phase shift at that time, the different resolved sub-beams or diffraction orders are superimposed and interfered. In the case of movement, a periodic modulation of the interference fringe pattern is obtained, which modulation can be grasped using a suitable optoelectronic detector. Regarding the situation of this interferometer, it is recommended to refer to Chapter 4 of J. Willhelm's doctoral dissertation "Dreigitterschrittgeber" published in 1978, pages...

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Problems solved by technology

However, none of the interferometers disclosed in the aforementioned documents meets all the proposed requirements in a satisfactory manner.

[0006] Thus, the system disclosed by US 6,005,667, although less sensitive to misalignment of the scale grating and scanning unit, is as prone to scale grating contamination as before

[0007] It turns out that the disadvantage of the device described in US 5,574,558 is that it is sensitive to fluctuations in the distance between the two relative movable gratings, that is to say, especially in this direction, there are only small assembly tolerances

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