Interferometric Sensor for Buried Optical Interface Measurement
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Solution Overview
Problem
Current methods for measuring the shape of optical elements, such as lenses, are limited to individual components before assembly and do not effectively allow for the measurement of interfaces within optical assemblies, which is crucial for ensuring precise manufacturing and positioning of optical components.
Innovation Solution
A device and method utilizing an interferometric sensor with a low coherence source to measure the shape of interfaces within optical assemblies by selectively detecting interference signals between a measurement beam and a reference beam, allowing for the determination of interface shapes and positions, even for buried interfaces, through the use of positioning means to align the coherence zone and digital processing to produce shape information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional interferometric measurement methods are used, then individual lens surfaces can be measured with high precision, but the measurement of interfaces within assembled optical elements is not possible
Solution Approach 1:
The patent uses a low-coherence light source as an intermediary to enable interferometric measurement through multiple interfaces. The low coherence length allows the measurement beam to selectively interfere only with reflections from the target interface, filtering out signals from other interfaces in the assembly. This mediator enables the system to measure buried interfaces within assembled optical elements without being affected by other optical components.
Solution Approach 2:
The patent applies local quality by making the coherence property spatially selective. The low-coherence source creates a localized coherence zone that can be positioned at specific depths within the optical assembly. This allows measurement of individual interfaces within the assembly by tuning the coherence length to match the depth of the target interface, effectively creating a localized measurement volume that excludes other interfaces.
2Adaptability or versatility
If the measurement beam passes through multiple interfaces to reach buried interfaces, then interfaces within assemblies can be measured, but interference signals from multiple interfaces complicate the measurement
Solution Approach 1:
The low-coherence light source acts as a mediator that filters out unwanted interference signals. By matching the coherence length to the depth of the target interface, the system selectively receives interference signals only from that specific interface, while signals from other interfaces fall outside the coherence window and are automatically rejected. This preserves signal clarity even when measuring through multiple interfaces.
Solution Approach 2:
The patent changes the coherence length parameter of the light source to match the depth of the target interface. By adjusting this parameter, the system can selectively measure different interfaces within the assembly. This parameter change transforms the measurement capability from being affected by all interfaces to being selective for a specific interface, thereby maintaining signal clarity.
3Measurement precision
If positioning means are added to align the coherence zone with the interface to be measured, then measurement of specific interfaces is enabled, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical positioning systems with optical path length control. Instead of physically moving the measurement beam or the optical element, the system adjusts the optical path length in the reference arm of the interferometer to position the coherence zone. This substitution of mechanical positioning with optical path control reduces device complexity while maintaining measurement precision.
Solution Approach 2:
The patent uses parameter changes in the optical path length to achieve positioning of the coherence zone. By varying the optical path length difference between the measurement and reference arms, the coherence zone can be positioned at different depths within the optical assembly. This parameter-based positioning is simpler than mechanical positioning systems while achieving the same functionality.
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
Enables precise measurement of interface shapes and positions within optical assemblies, improving manufacturing precision and allowing for the detection of decentering or inclination of lenses, thereby enhancing the optical performance of assembled optical elements.
Implementation Method 1
selectively detect an interference signal resulting from interference between the measurement beam reflected by said interface to be measured and a reference beam
Implementation Method 2
measurement means with at least one interferometric sensor illuminated by a low-coherence source
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
AI summary
The invention relates to a method and device (1) for measuring the shape of an interface (103) of an optical element (1000) comprising a plurality of interfaces, the device (1) comprising: measurement means (4000, 6000, 7000) with at least one interferometric sensor illuminated by a low-coherence source (402, 612, 712) configured to direct a measurement beam (106, 606) towards the optical element (1000) so as to pass through the plurality of interfaces, and in order to selectively detect an interference signal resulting from the interference between the measurement beam (106, 606) reflected by the interface (103) to be measured and a reference beam (616, 716); positioning means (608, 611, 708, 711) configured for relative positioning of a zone of coherence of the interferometric sensor at the interface to be measured; digital processing means configured to produce, from the interference signal, a piece of shape information of the interface (103) to be measured in a field of view (108).