Diffraction-Grating Displacement Sensor for Zero-Incidence 3D Measurement
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Solution Overview
Problem
Existing displacement and 3D profile sensors face performance issues due to the angle of incidence of light on image sensors being offset from zero, leading to deteriorated performance and limitations in triangulation angles that affect shadowing and magnification, preventing accurate measurement.
Innovation Solution
The sensor employs a configuration with first and second intermediate optics and a diffraction grating to focus measurement light onto a diffraction grating, allowing for angles of incidence and diffraction that are essentially zero, enabling improved performance of image sensors by using a single light sensor to measure diffracted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If triangulation angle is increased to reduce angle of incidence on image sensor, then image sensor performance is improved, but shadowing of reflected light increases
Solution Approach 1:
A beam splitter is introduced as an intermediary optical element to separate the measurement light path from the reference light path. The beam splitter directs reflected measurement light to the image sensor while allowing reference light to pass through, enabling independent optimization of the triangulation angle for shadowing reduction while maintaining zero angle of incidence on the sensor through the beam splitting mechanism
Solution Approach 2:
The system transitions from a single-plane optical arrangement to a multi-dimensional optical path configuration using the beam splitter. This allows the measurement light to traverse a different spatial dimension (through the beam splitter) compared to reference light, enabling the triangulation angle to be increased for shadowing reduction while the image sensor remains perpendicular to the reference light path
2Measurement precision
If magnification is increased to improve measurement accuracy, then measurement precision is improved, but angle of incidence on image sensor increases
Solution Approach 1:
The beam splitter acts as an intermediary that decouples the magnification function from the image sensor orientation. Magnification optics can be placed in the reference light path without affecting the angle of incidence on the image sensor, as the beam splitter separates the magnified image formation from the sensor placement geometry
Solution Approach 2:
The optical system is segmented into separate functional paths: the reference light path contains magnification optics for improving measurement accuracy, while the measurement light path is directed to the image sensor at zero angle of incidence through the beam splitter, allowing independent optimization of each function
3Adaptability or versatility
If angle of incidence on image sensor is offset from zero to enable triangulation measurement, then displacement measurement capability is enabled, but image sensor performance deteriorates
Solution Approach 1:
The beam splitter serves as a mediator that separates the triangulation measurement function from the image sensor operation. The reference light provides the zero-angle reference for triangulation calculations, while the measurement light is directed to the sensor perpendicular to its surface, maintaining optimal sensor performance while enabling displacement measurement capability
Solution Approach 2:
The system uses dimensional separation by introducing a beam splitter that creates distinct optical paths in different spatial dimensions. The reference light defines the triangulation geometry in one dimension while the measurement light is redirected in another dimension to strike the sensor at zero angle, resolving the contradiction between measurement capability and sensor performance
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 performance of image sensors by allowing them to operate at near-zero angles, reducing shadowing and enabling accurate measurement of surface displacements and 3D profiles without the limitations of traditional triangulation-based systems.
Implementation Method 1
at least one diffraction grating aligned with the intermediate image plane such that reflected measurement light is in focus on and incident upon the surface of the diffraction grating, and such that measurement light is diffracted along a third measurement axis
Implementation Method 2
first intermediate optics positioned along a first measurement axis and configured to focus measurement light reflected on a first side of the measurement plane in an intermediate image plane; second intermediate optics positioned along a second measurement axis and configured to focus measurement light reflected on a second side of the measurement plane in the intermediate image plane
Data Source
AI summary
The invention relates to a displacement sensor, for example as used in 3D sensors for measuring the three-dimensional shape of an object. A diffraction grating is used to reduce the angle of incidence of measurement light on a light sensor, such as an image sensor, thereby improving the performance of the light sensor. The displacement sensors of the present invention include sensors based on triangulation and coaxial sensors.