Photoelectric position measuring device
AssigneeDr. Johannas Heidenhain GmbH
InventorsPeter Speckbacher, Michael Allgäuer, Georg Flatscher, Anton Sailer, Walburga Kern
Life of this patent
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Abstract
In a position measuring device, a scale is embodied as a phase grating on which several partial beams impinge and are diffracted and caused to interfere with each other in the scanning unit. The entry angle (α) of the partial beams corresponds to the Littrow angle, so that the diffracted partial beams of ±1st diffraction order are diffracted at the same angle β=α. The diffraction efficiency of the scale is particularly great if the flanks of the bars of the scales are at an angle of approximately 70° with respect to the measuring direction, i.e., if the bars and gaps are embodied to be trapezoidal in cross section.
Claims21
A position measuring device with a light source and a detector for measuring the position of two objects which are movable with respect to each other in a measuring direction, the device comprising:
- a diffraction grating coupled to one object and formed by a reflecting relief structure having bars and gaps alternatingly arranged in the measuring direction and structured to increase the diffraction efficiency of the diffraction grating, and having a graduation period equal to or less than the wavelength of impinging beams from the light source wherein the bars have a trapezoidal shape with flank angles (γ) ranging from about 60° to about 80° with respect to the measuring direction.
A position measuring device with a light source and a detector for measuring the position of two objects which are movable with respect to each other in a measuring direction, the device comprising:
- a diffraction grating coupled to one object and formed by a reflecting relief structure having bars and gaps alternatingly arranged in the measuring direction and structured to increase the diffraction efficiency of the diffraction grating, and having a graduation period equal to or less than the wavelength of impinging beams from the light source wherein the bars have a trapezoidal shape with flank angles (γ) ranging from about 60° to about 80° with respect to the measuring direction;
- and
- wherein the reflecting relief structure of the diffraction grating comprises a reflecting surface made of an electrically conductive material.
A position measuring device with a light source and a detector for measuring the position of two objects which are movable with respect to each other in a measuring direction, the device comprising:
- a diffraction grating coupled to one object and formed by a reflecting relief structure having bars and gaps alternatingly arranged in the measuring direction and structured to increase the diffraction efficiency of the diffraction grating, and having a graduation period equal to or less than the wavelength of impinging beams from the light source wherein the bars have a trapezoidal shape with flank angles (γ) ranging from about 60° to about 80° with respect to the measuring direction;
- wherein the bars of the diffraction grating are formed of silicon coated by a reflecting surface;
- and
- wherein the reflecting relief structure is made of chromium.
A position measuring device with a light source and a detector for measuring the position of two objects which are movable in relation to each other in a measuring direction, the device comprising:
- a diffraction grating in the form of a reflecting relief grating with bars and gaps alternatingly arranged in the measuring direction and structured to increase the diffraction efficiency of the diffraction grating, the diffraction grating having a graduation period approximately equal to or less than the wavelength of an impinging light beam wherein the bars are approximately trapezoidal in shape having a flank angle of 70°±10°.
Dependencies are inferred from the claim text.