Optical Accelerometer Using Diffraction Grating for 3D Measurement
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Solution Overview
Problem
Conventional accelerometers face challenges in accurately measuring three-dimensional acceleration, with capacitive accelerometers experiencing small capacitance variations and difficulty in measuring beyond two dimensions, and optical accelerometers struggling with fiber alignment.
Innovation Solution
An optical accelerometer utilizing a diffraction pattern generated by a movable member with periodic slots or fingers acting as a diffraction grating, allowing for the detection of three-dimensional acceleration through zero-order and first-order diffraction patterns, with a processing unit calculating in-plane and out-of-plane accelerations based on these patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive accelerometer uses comb-like electrode plates to detect acceleration, then the acceleration can be measured, but the capacitance variation is very small and difficult to measure
Solution Approach 1:
The patent replaces the capacitive sensing mechanism with an optical sensing mechanism. Instead of measuring small capacitance variations through mechanical electrode plate displacement, the system uses a diffraction grating on the proof mass that modulates light intensity when illuminated by a light source. The optical detector measures light intensity changes, which are much easier to detect than small capacitance variations, thereby resolving the measurement difficulty while maintaining acceleration detection capability.
2Measurement precision
If a conventional optical accelerometer uses transmitting and detecting fibers to monitor light coupling efficiency, then acceleration can be detected, but the alignment between fibers is not easy to implement
Solution Approach 1:
The patent extracts the fiber alignment requirement from the system by eliminating the transmitting fiber component. Instead of using two fibers (one transmitting, one detecting) that require precise alignment, the system uses a single optical detector that directly measures light intensity changes through the diffraction grating. This removes the complex alignment requirement while maintaining the optical detection function for acceleration measurement.
Solution Approach 2:
The patent introduces a light source as an intermediary element that illuminates the diffraction grating on the proof mass. The light source serves as a mediator between the mechanical proof mass and the optical detector, enabling the system to measure acceleration through light intensity modulation without requiring direct fiber-to-fiber alignment. The light source provides a stable illumination that simplifies the optical path configuration.
3Adaptability or versatility
If conventional accelerometers measure acceleration in multiple dimensions, then comprehensive acceleration data is obtained, but the device complexity increases
Solution Approach 1:
The patent achieves multi-dimensional acceleration measurement capability through a single diffraction grating structure on the proof mass. The grating can be configured with different orientations and the optical detector can measure light intensity changes that correspond to acceleration in multiple directions. This universal approach allows the system to detect 3D acceleration without requiring separate sensing elements for each dimension, thereby reducing device complexity while maintaining comprehensive measurement 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
Enables accurate simultaneous detection of three-dimensional acceleration, overcoming the limitations of conventional accelerometers by generating and analyzing diffraction patterns to determine both in-plane and out-of-plane movements.
Implementation Method 1
Periodic slots are formed along at least one direction on the movable member to be served as a diffraction grating... configured to detect a zero-order diffraction pattern and a first-order diffraction pattern generated by the diffraction grating
Data Source
AI summary
There is provided an optical accelerometer including a first substrate, a second substrate, a spacer and a processing unit. The first substrate includes a frame, a movable member and at least one elastic member. Periodic slots are formed on the movable member along at least one direction to be served as a diffraction grating. The elastic member is connected between the frame and the movable member. The second substrate includes at least one sensing unit configured to detect a diffraction pattern formed by the diffraction grating. The spacer is disposed between the first substrate and the second substrate to define a predetermined height. The processing unit is coupled to the sensing unit and configured to calculate a 3D acceleration according to the diffraction pattern.