Heterodyne Interferometer with Non-Polarizing Beam Splitter
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Solution Overview
Problem
Existing optical interferometers face challenges in reproducibility and reliability due to high demands on the production of coordinated optically polarizing components, leading to low reproducibility and high manufacturing costs, as well as interference from stray light components that negatively affect signal quality.
Innovation Solution
The design of a heterodyne interferometer with a beam splitter device placed before the optical frequency shifter, using non-polarizing waveguide elements and a birefringent frequency shifter to minimize stray light components and reduce intensity losses, allowing for a more robust and compact structure with improved reproducibility and reduced interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coordinated optically polarizing components are used in the interferometer, then the interferometric measurement function is achieved, but the manufacturing complexity and costs increase while reproducibility decreases
Solution Approach 1:
The patent extracts the polarizing function from the beam splitter device by using a non-polarizing beam splitter in combination with a polarization filter in one of the optical paths. This separation allows the beam splitter to be manufactured with standard tolerances while the polarization function is handled by a dedicated filter component, improving overall reproducibility and easing manufacturing.
Solution Approach 2:
Instead of using a polarizing beam splitter that combines beam splitting and polarization functions, the patent inverts the approach by using a non-polarizing beam splitter and adding polarization control through a filter in one path. This inversion simplifies the beam splitter manufacturing while achieving the same functional result.
2Measurement precision
If stray light components are present in the optical paths, then the interferometer can be simpler to manufacture, but the signal quality and measurement precision deteriorate
Solution Approach 1:
The patent introduces a polarization filter as an intermediary component in one of the optical paths. This filter mediates between the non-polarizing beam splitter and the detector, blocking stray light components while allowing the desired polarized light to pass through, thereby improving signal quality without requiring complete redesign of the optical system.
3Loss of energy
If a polarizing beam splitter is used to divide the beam, then the interferometric function is achieved, but intensity losses occur and the system becomes more sensitive to polarization mismatches
Solution Approach 1:
The patent segments the beam splitting function from the polarization function. The non-polarizing beam splitter handles only the beam division with minimal intensity loss, while the polarization control is separately handled by a polarization filter in one optical path. This segmentation eliminates the sensitivity to polarization mismatches that plagues polarizing beam splitters.
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 enhances the reproducibility and reliability of the interferometer, reduces manufacturing costs, and minimizes stray light interference, resulting in low-noise and high-quality interferometric measurements.
Implementation Method 1
a beam splitter device for splitting the output beam into at least a first partial beam and a second partial beam
Implementation Method 2
By means of the frequency shifter, the frequency of the first partial beam can thus be shifted at least relative to the frequency of the second partial beam, so that the interference signal has a carrier frequency
Implementation Method 3
The interferometer comprises one or more optical waveguide elements, by means of which optical waveguides are formed at least between the output beam, beam input, beam splitter device and frequency shifter
Implementation Method 4
the two partial beams are guided, at least partially, through separate optical paths, and finally the two partial beams are recombined to produce interference
Data Source
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AI summary
The invention relates to a device for the interferometric measurement of an object (MO), comprising a radiation source (7), an interferometer, and at least one first detector (12a), wherein the interferometer is configured with an output beam input (1) for coupling an output beam and a beam splitter (3) for splitting the output beam into at least a first partial beam (4) and a second partial beam (5), wherein the interferometer is configured as a heterodyne interferometer in that at least one optical frequency shifter (6) is arranged in the beam path of the interferometer, and wherein the interferometer has one or more optical waveguide elements (2, F2, F3, F4) by means of which optical waveguides are formed at least between the output beam input (1), the beam splitter (3), and the frequency shifter (6), wherein the frequency shifter (6) is arranged in the beam path of one of the partial beams.wherein the radiation source and the interferometer are configured to interact in such a way that a light beam generated by the radiation source (7) can be coupled as an output beam into the output beam input, wherein the interferometer is configured to image the first partial beam as a measuring beam onto the object (MO), and wherein the interferometer and the first detector are configured to interact in such a way that the measuring beam at least partially reflected by the object (MO) is the receiving beam and the reference beam is at least partially superimposed on at least one detector surface of the first detector (12a). The invention is characterized in that the beam splitter device is configured to divide the output beam into a measuring beam, a first reference partial beam and at least one second reference partial beam, and to divide the receiving beam into a first receiving partial beam and at least one second receiving partial beam.that the device has at least one second detector (12b) and is configured such that the first received beam is superimposed with the first reference partial beam on a detection surface of the first detector (12a) and the second received partial beam is superimposed with the second reference partial beam on a detection surface of the second detector (12b), each forming optical interference, and that the device has an evaluation unit for evaluating the measurement signals of the first and the second detector (12a, 12b), which is configured to evaluate the measurement signals of the two detectors according to the principle of receive diversity.