VCSEL Self-Mixing Touch Sensing for Accurate Drag Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing touch input systems on electronic devices struggle to accurately distinguish user inputs from false detections, particularly in cases of continuous drag motions, due to limitations in current sensing technologies.
Innovation Solution
The use of vertical-cavity surface-emitting lasers (VCSELs) to detect user inputs by analyzing self-mixing interference of coherent light reflected from the touch input surface, combined with photodetectors to measure interferometric parameters, allowing for precise detection of lateral and vertical motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch sensing technologies are used, then the device can detect basic touch inputs, but it cannot accurately distinguish genuine user inputs from false detections during continuous drag motions
Solution Approach 1:
The patent replaces conventional mechanical or capacitive touch sensing systems with an optical sensing system using VCSELs and interferometric measurement. The VCSEL emits coherent light that reflects off the touch input surface, and self-mixing interference within the laser cavity detects surface deflections with high precision, enabling accurate distinction between genuine touches and false detections during drag motions.
Solution Approach 2:
The patent introduces coherent light as an intermediary between the touch input surface and the detection system. The light acts as a mediator that interacts with the surface deflections caused by user input, carrying information about the touch characteristics back to the VCSEL for interferometric analysis, thereby enabling precise measurement of lateral and vertical motions.
2Measurement precision
If VCSELs with self-mixing interference are used to detect lateral and vertical motions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the light source (VCSEL) and the detector into a single integrated component. The VCSEL serves dual functions: emitting coherent light and detecting the reflected light through self-mixing interference within its cavity. This integration eliminates the need for separate lasers and photodetectors, reducing overall system complexity while maintaining high measurement precision for lateral and vertical motions.
Solution Approach 2:
The VCSEL is designed to perform multiple functions: it acts as both the coherent light source and the interferometric sensor. The same laser component that generates the light beam also detects the reflected light through self-mixing interference, enabling the system to measure both lateral and vertical deflections of the touch input surface using a single versatile component.
3Measurement precision
If spectrum or time domain analysis is applied to interferometric parameters, then the ability to differentiate genuine inputs from false detections is enhanced, but processing complexity increases
Solution Approach 1:
The patent employs periodic analysis methods (spectrum analysis and time domain analysis) to process the interferometric parameters. By analyzing the periodic characteristics of the interference signals at different frequencies, the system can distinguish between genuine user inputs and false detections during drag motions, enhancing input characterization accuracy through systematic signal processing approaches.
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 detection of user inputs, including drag motions, by analyzing interferometric parameters through spectrum or time domain analysis, enhancing the device's ability to differentiate between genuine inputs and false detections.
Implementation Method 1
analyzing an interference signal produced when coherent light generated and emitted by a laser reflects from the user input surface, is received back into the laser, and is coherently mixed with the light generated within the laser cavity
Implementation Method 2
Each VCSEL's beam of coherent light can include a first amount of coherent light generated by the VCSEL and a second amount of coherent light reflected from the user input surface or target into the VCSEL and mixed with the first amount of coherent light inside the laser cavity
Implementation Method 3
The electronic device also has a set of sensors configured to measure interferometric parameters associated with the beams of coherent light
Data Source
AI summary
Disclosed herein are electronic devices having touch input surfaces. A user's touch input or press on the touch input surface is detected using a set of lasers, such as vertical-cavity surface-emitting lasers (VCSELs) that emit beams of light toward the touch input surface. The user's touch causes changes in the self-mixing interference within the VCSEL of the emitted light with reflected light, such as from the touch input surface. Deflection and movement (e.g., drag motion) of the user's touch is determined from detected changes in the VCSELs' operation due to the self-mixing interference.