Voice Coil Screen Motion Sensing via Back-EMF
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Solution Overview
Problem
Existing motion-sensing technologies for display devices, such as optical position sensors and accelerometers, face issues with alignment problems, mechanical wear, high cost, and accuracy issues due to integration errors, which affect the quality of image despeckling and screen motion control.
Innovation Solution
A system utilizing a voice coil mechanically coupled to a diffuser screen, where a signal-processing device, such as a microprocessor, senses the voltage across the voice coil to produce a current that imparts a controlled force and motion to the screen, using a closed-loop feedback arrangement to maintain minimal rotational motion and avoid mechanical resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical position sensors or accelerometers are used to sense screen motion, then motion sensing capability is provided, but alignment problems, mechanical wear, high cost, and accuracy issues occur
Solution Approach 1:
The patent combines the motion sensing function with the existing voice coil assembly by utilizing the back-EMF voltage generated during screen motion. This merging eliminates the need for separate optical position sensors or accelerometers, thereby reducing device complexity while maintaining motion sensing capability. The voice coil serves dual purposes: actuating the screen and sensing its motion through the generated voltage signal.
Solution Approach 2:
The voice coil assembly performs self-sensing by generating a voltage signal (back-EMF) during screen motion that can be used to detect the screen's velocity. This self-service approach eliminates the need for external sensing components, reducing both device complexity and potential alignment issues while providing accurate motion feedback for despeckling control.
2Measurement precision
If separate motion-sensing components are used, then screen motion can be detected, but cost and device complexity increase
Solution Approach 1:
The patent merges the motion sensing function into the existing voice coil assembly, eliminating the need for separate motion-sensing components. This integration reduces manufacturing cost and assembly complexity while maintaining the capability to detect screen motion for despeckling control.
Solution Approach 2:
The voice coil assembly is designed to perform multiple functions: actuating the diffuser screen and sensing its motion simultaneously. This multi-functionality reduces the total component count, simplifies manufacturing, and lowers cost while providing the necessary motion detection capability for effective despeckling.
3Measurement precision
If optical sensors are used for motion sensing, then screen position can be measured, but alignment problems and mechanical abrasion occur
Solution Approach 1:
The patent replaces mechanical/optical sensing systems with an electromagnetic sensing approach. By measuring the back-EMF voltage generated in the voice coil during screen motion, the system eliminates mechanical contact and optical alignment requirements, thereby improving reliability by removing sources of mechanical wear and alignment drift.
Solution Approach 2:
The voice coil assembly performs self-sensing by generating a voltage signal during screen motion that can be used to detect the screen's velocity. This self-service approach eliminates the need for external sensing components, reducing both device complexity and potential alignment issues while providing accurate motion feedback for despeckling control.
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 solution provides a cost-effective and accurate method for imparting controlled motion to the diffuser screen, reducing speckle effects and mechanical wear, while eliminating the need for separate motion-sensing components, thereby enhancing image quality and system reliability.
Implementation Method 1
a conductive coil in a magnetic field to impart a force to a mechanical object
Implementation Method 2
sense a motion of the object
Data Source
AI summary
In one embodiment, a display device includes a movably suspended diffuser screen, and a voice-coil mechanism coupled to the diffuser screen. A signal-processing device, such as a microprocessor, is coupled to a driver circuit to produce a drive signal at an output terminal for the voice coil in response to a voltage sensed across the voice coil. The driver circuit includes shutdown control to drive its output terminal to a high-impedance state to accommodate sensing voltage across the voice coil. Thus, the signal for the voice coil is produced by the signal-processing device in a closed-loop feedback arrangement without the need for separate position-sensing elements. In a preferred arrangement, a second voice coil is coupled to the diffuser screen and to the signal-processing circuitry to produce a second signal for the second voice coil to accommodate generating a circular motion for the diffuser screen without stationary points.