Capacitive Angle Sensing for MEMS Mirrors
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Solution Overview
Problem
Existing position sensing devices (PSDs) for optical reflectors in laser scanning projectors are bulky and consume high power, making them unsuitable for applications requiring small size and low power consumption, such as wearable heads-up displays, and they are not necessary for determining the position attribute of optical reflectors like slow-axis mirrors in scanning laser projectors.
Innovation Solution
A system and method that determines the position attribute of an optical reflector, such as a slow-axis mirror, using a controller and a comb-shaped rotor with inner and outer stators, which changes capacitance based on its position, allowing for electrostatic actuation and eliminating the need for a separate optical PSD, thereby reducing size, weight, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate optical position sensing device (PSD) is used to determine the position attribute of the optical reflector, then the position measurement accuracy is improved, but the device size, weight, and power consumption increase
Solution Approach 1:
The patent combines the position sensing function with the electrostatic actuation structure by using the same comb-shaped rotor and stator assembly. The capacitance measurements between rotor teeth and stator teeth provide position information without requiring a separate optical PSD, thereby reducing power consumption and device complexity while maintaining measurement capability
Solution Approach 2:
The comb-shaped rotor-stator structure serves multiple functions: it provides electrostatic actuation to drive the optical reflector and simultaneously serves as a capacitive sensor to determine the position attribute. This multi-functionality eliminates the need for separate actuation and sensing components, reducing overall device size and power consumption
2Measurement precision
If a separate optical position sensing device (PSD) is used to determine the position attribute of the optical reflector, then the position measurement accuracy is improved, but the device size and weight increase
Solution Approach 1:
The patent combines the position sensing function with the electrostatic actuation structure by using the same comb-shaped rotor and stator assembly. The capacitance measurements between rotor teeth and stator teeth provide position information without requiring a separate optical PSD, thereby reducing power consumption and device complexity while maintaining measurement capability
Solution Approach 2:
The comb-shaped rotor-stator structure serves multiple functions: it provides electrostatic actuation to drive the optical reflector and simultaneously serves as a capacitive sensor to determine the position attribute. This multi-functionality eliminates the need for separate actuation and sensing components, reducing overall device size and power consumption
3Measurement precision
If a separate optical position sensing device (PSD) is used to determine the position attribute of the optical reflector, then the position measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent combines the position sensing function with the electrostatic actuation structure by using the same comb-shaped rotor and stator assembly. The capacitance measurements between rotor teeth and stator teeth provide position information without requiring a separate optical PSD, thereby reducing power consumption and device complexity while maintaining measurement capability
Solution Approach 2:
The comb-shaped rotor-stator structure serves multiple functions: it provides electrostatic actuation to drive the optical reflector and simultaneously serves as a capacitive sensor to determine the position attribute. This multi-functionality eliminates the need for separate actuation and sensing components, reducing overall device size and power consumption
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 determination of the position attribute of optical reflectors without the need for a separate PSD, leading to smaller, lighter, and more power-efficient devices, suitable for applications like wearable heads-up displays.
Implementation Method 1
determining a position attribute of the optical reflector based on the relationship between a first capacitance and a second capacitance, the first capacitance corresponding to a capacitance between the rotor and the first stator, and the second capacitance corresponding to a capacitance between the rotor and the second stator
Implementation Method 2
allowing for electrostatic actuation and eliminating the need for a separate optical PSD
Data Source
AI summary
A system includes an optical reflector to reflect the light, the optical reflector having a rotor, a first stator, and a second stator. The system further includes a controller in communication with the optical reflector. The controller is to drive the optical reflector by applying a first actuation voltage to the first stator, and a second actuation voltage to the second stator. Further, the controller is to apply an excitation voltage to the first stator. Furthermore, the controller is to determine a relationship between a first capacitance between the rotor and the first stator, and a second capacitance between the rotor and the second stator. Based on the relationship, the controller is to determine a position attribute of the optical reflector.