Fabry-Pérot Optical Measurement for Shadow-Resistant 3D Sensing
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Solution Overview
Problem
Existing displacement and 3D profile sensors face issues with light incidence angles that degrade image sensor performance and limit triangulation angles, leading to shadowing and reduced accuracy due to magnification effects.
Innovation Solution
The use of Fabry-Pérot filters to filter measurement light before and after reflection from the measurement object, ensuring unique wavelengths or wavelength combinations for in-focus light, and employing optical configurations like diffraction gratings and beam splitters to direct and focus light onto a light sensor, allowing accurate displacement and shape measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the triangulation angle is increased to reduce the angle of incidence on the image sensor, then the image sensor performance is improved, but the shadowing of reflected light increases due to height changes of the measurement object
Solution Approach 1:
A Fabry-Pérot filter is introduced as an intermediary optical element between the measurement object and the image sensor. This filter selectively transmits light reflected from the measurement plane while blocking light reflected from other surfaces, thereby eliminating shadowing effects without requiring increased triangulation angle
Solution Approach 2:
The patent changes the optical parameter of wavelength selectivity by using a Fabry-Pérot filter with specific free spectral range and finesse characteristics. This allows the system to distinguish between light from different heights based on wavelength, enabling accurate measurements without increasing triangulation angle
2Measurement precision
If magnification is applied to enlarge the image for improved accuracy, then the measurement accuracy is improved, but the angle of incidence of light on the image sensor increases, preventing effective use of magnification
Solution Approach 1:
The Fabry-Pérot filter acts as an intermediary that separates light paths based on wavelength, allowing the system to use magnification for improved accuracy while maintaining acceptable angle of incidence on the image sensor by blocking stray light that would cause shadowing
Solution Approach 2:
The optical system is segmented into distinct functional elements: light source, Fabry-Pérot filter, measurement object, and image sensor. This segmentation allows independent optimization of each component, enabling magnification to be applied without compromising image sensor performance
3Ease of operation
If the angle of incidence of light on the image sensor is offset from zero to enable measurement, then the measurement function is achieved, but the image sensor performance deteriorates
Solution Approach 1:
The Fabry-Pérot filter serves as a mediator that enables the measurement function to operate at non-zero angles of incidence while protecting the image sensor performance by blocking light that would create shadowing and measurement errors
Solution Approach 2:
The patent introduces a new dimension of wavelength selectivity to the optical measurement system. By using the Fabry-Pérot filter to separate wavelengths, the system can operate at non-zero angles without the performance deterioration that would normally occur, as the wavelength dimension provides additional separation capability
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 approach enhances measurement accuracy by filtering out light not reflected from the measurement plane, reducing shadowing, and enabling precise determination of object displacement and 3D shape with improved sensitivity to height changes.
Implementation Method 1
at least one Fabry-Pérot filter; Measurement light emitted from the light source and incident in the measurement plane and reflected measurement light from the measurement plane are filtered by the at least one Fabry-Pérot filter
Implementation Method 2
The first optics may comprise a first optical subset, a diffraction grating, and a second optical subset. The diffraction grating may be positioned in the focal plane of the first optical subset, and measurement light diffracted from the diffraction grating may be focused in the measurement plane by the second optical subset.
Implementation Method 3
first optics configured to focus measurement light in a measurement plane, and to focus measurement light reflected from the measurement plane at infinity
Data Source
AI summary
The invention relates to the field of optical measurement devices, in particular to displacement sensors, 3D sensors for measuring the position and/or shape or thickness of a measurement object. Measurement light is projected onto a measurement object after 5 filtering by a Fabry-Pérot filter such that at each point in a measurement plane, the filtered measurement light has a locally unique wavelength or combination of wavelengths in at least one direction in the measurement plane. Measurement light reflected from the surface of the measurement object is also filtered by a Fabry-Pérot filter in order to filter out measurement light not reflected from the intersection of the measurement object with 0 the measurement plane. To be published with