Interferometer Measuring Reflector With Transmission Grating
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Solution Overview
Problem
Conventional interferometers with measuring reflectors composed of two perpendicular plane mirrors experience periodic signal errors and require larger construction volumes due to non-invariant spot patterns when the reflector is displaced orthogonally to the measuring direction, leading to errors in position measurement.
Innovation Solution
The interferometer employs a measuring reflector with at least one transmission grating and a reflector element, which imparts a perpendicular offset to the measurement beam, ensuring an invariant spot pattern even when displaced along non-coinciding axes, using transmission gratings and reflector elements to maintain beam alignment and polarization control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a measuring reflector with two perpendicular plane mirrors is used, then periodic signal errors are minimized, but the spot pattern becomes non-invariant when the reflector is displaced orthogonally to the measuring direction, leading to position measurement errors and requiring larger construction volumes
Solution Approach 1:
The patent changes the fundamental parameters of the measuring reflector by replacing two perpendicular plane mirrors with a single transmission grating and reflector element combination. This parameter change transforms the beam interaction mechanism from geometric reflection to diffraction-based beam deflection, which inherently provides invariant spot patterns under orthogonal displacement while maintaining minimization of periodic signal errors through the periodic structure of the transmission grating
2Measurement precision
If a measuring reflector with two perpendicular plane mirrors is used, then periodic signal errors are minimized, but the construction volume increases due to the need for larger beam diameters and more space to accommodate displacement variations
Solution Approach 1:
The patent changes the optical interaction parameters by using a transmission grating with specific groove spacing and a reflector element positioned at a defined distance, replacing the need for large beam diameters and extensive optical paths. This parameter transformation enables compact interferometer design while maintaining the ability to minimize periodic signal errors through the grating's periodic structure
Solution Approach 2:
The patent substitutes the mechanical alignment system of two perpendicular mirrors requiring precise orthogonal positioning with an optical diffraction system based on transmission grating. This substitution eliminates the need for large construction volumes to accommodate mechanical displacement variations, as the diffraction-based beam deflection is inherently invariant under orthogonal displacement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration minimizes periodic signal errors, reduces the interferometer's size, and prevents position measurement errors due to beam displacement, allowing for flexible spot pattern adjustment and reduced alignment complexity.
Implementation Method 1
The measuring reflector in each instance includes at least one transmission grating as well as a reflector element. The measurement beam incoming toward the measuring reflector along the first direction initially impinges on the transmission grating at a first point of impact and undergoes a first deflection in a first offset plane
Implementation Method 2
The measurement beam is then reflected back again at the reflector element in the direction of the transmission grating and impinges on the transmission grating at a second point of impact, where the measurement beam undergoes a second deflection in the first offset plane
Implementation Method 3
a detector system, which is able to be supplied with the superposed and recombined measurement beam and reference beam, is able to generate a distance-dependent interference signal with regard to the position of the measuring reflector
Data Source
AI summary
An interferometer includes a light source and a beam splitter, via which the beam of rays emitted by the light source is split into a measurement beam and a reference beam. The measurement beam propagates in a measuring arm extending in a first direction between the beam splitter and a measuring reflector. The measuring reflector brings about an offset perpendicular to the direction of incidence between the measurement beam falling on it and the measurement beam reflected back by it. In a reference arm extending in a second direction, the reference beam propagates between the beam splitter and a reference reflector. In addition, the interferometer has a detector system, to which the superposed and recombined measurement beam and reference beam are able to be supplied, and via which a distance-dependent interference signal with respect to the position of the measuring reflector is able to be generated. The measuring reflector in each case includes at least one transmission grating as well as a reflector element.