Optical Rotary Encoder Using Self-Mixing Interference for Miniaturization
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Solution Overview
Problem
Existing rotary encoders for smartwatches are complex and costly due to the need for precise alignment of multiple components, such as light sources and light receiving elements, making miniaturization and cost reduction challenging.
Innovation Solution
The use of a rotary encoder with an eccentrically mounted component that measures angular position and axial movement by varying the distance between a light source and detector, utilizing self-mixing interference and VCSELs for compact and cost-effective detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional rotary encoders use multiple light sources and light receiving elements with precise alignment, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple light sources into a single light source and merges the light receiving elements into one detector. This consolidation eliminates the need for precise alignment between multiple components while maintaining the capability to detect both angular position and axial movement through the integrated detector's analysis of reflected light patterns
Solution Approach 2:
The single light source and single light receiving element perform multiple functions: detecting angular position, detecting axial movement, and determining rotation direction. The integrated detector analyzes various characteristics of the reflected light to extract multiple measurement parameters, making the system multi-functional without requiring multiple specialized components
2Volume of moving object
If rotary encoders are miniaturized for smartwatch applications, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
By merging multiple components into a single integrated detector and single light source, the patent reduces the number of parts that need to be precisely positioned. This consolidation significantly reduces manufacturing precision requirements while enabling miniaturization suitable for smartwatch applications
Solution Approach 2:
The system uses the reflected light from the rotating component itself as the measurement target, eliminating the need for separate markings or features on the rotating part. The integrated detector processes the light pattern to automatically determine both angular and axial positions, reducing the need for precision manufacturing of external features
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 approach allows for miniaturized and cost-effective detection of angular and axial movements, enabling reliable operation in smartwatches and other devices with reduced component count and complexity.
Implementation Method 1
a light receiving element positioned to receive light reflected from the reflecting surface
Implementation Method 2
utilizing self-mixing interference and VCSELs for compact and cost-effective detection
Data Source
AI summary
A rotary encoder for providing a control signal in dependence upon an angular position of a controller rotatable about an axis of rotation. The rotary encoder includes a component for rotation with said controller about said axis of rotation. The rotary encoder also includes a radiation source and detector arrangement configured to direct radiation towards a target region and generate a detector signal dependent upon radiation reflected from within that target region. The rotary encoder further includes a computer processor configured to process said detector signal to determine a measure of distance or change of distance to a reflecting surface region within said target region, and to use said measure to provide said control signal. The component defines a reflecting surface that passes through said target region such that a reflecting surface region is present within said target region with a distance that varies with the angular position.