Optical Angular Position Detector with Segmented Light Emitter Array
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Solution Overview
Problem
Existing optical angular position detectors lack the high positional accuracy of capacitive detectors, with output linearity falling off significantly beyond ±10°, and are susceptible to interference and cost inefficiencies.
Innovation Solution
An optical angular position detector using a light emitter array centered on the axis to direct individual, overlapping light beams to light detectors, with calibration through linear regression to achieve 99.9% linearity up to ±10° and minimal loss in accuracy up to ±20°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical position detector uses a single light source or uniform circumferential illumination, then the device complexity is reduced and manufacturing is easier, but the measurement precision deteriorates with linearity falling off by 0.5-1.0% for angles greater than ±10°
Solution Approach 1:
The light source is segmented into multiple individual light emitters (typically 3-6 emitters) arranged in an array around the shaft axis. Each emitter illuminates a specific sector of the detector, creating distinct light patterns that improve angular position measurement precision across the full ±25° range while maintaining manageable device complexity through modular configuration.
Solution Approach 2:
Different light emitters are positioned at specific locations around the shaft to provide non-uniform, location-specific illumination patterns. This local quality approach ensures that each detector element receives optimized lighting for its specific angular position, maintaining 99.9% linearity across the entire operating range rather than uniform illumination that degrades at extreme angles.
2Measurement precision
If a capacitive position detector is used to achieve 99.9% linearity out to ±25°, then the measurement precision is improved, but the device complexity increases due to requiring an oscillator and the reliability deteriorates due to susceptibility to RF interference and environmental drift
Solution Approach 1:
The capacitive sensing system is replaced with an optical detection system. Instead of using capacitive sensors that require oscillators and are susceptible to RF interference, the invention uses light emitters and photodetectors that are immune to electromagnetic interference and environmental drift, achieving comparable 99.9% linearity without the reliability issues of capacitive detectors.
3Measurement precision
If a capacitive position detector is used to achieve high positional accuracy, then the measurement precision is improved, but the manufacturing cost increases due to requiring an oscillator and complex circuitry
Solution Approach 1:
The invention replaces expensive capacitive sensors and oscillators with inexpensive light-emitting diodes (LEDs) and simple photodetectors. These optical components are much cheaper to manufacture and do not require complex oscillating circuitry, reducing manufacturing costs while maintaining 99.9% positional accuracy through the segmented light emitter array configuration.
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
The solution provides improved positional accuracy and cost-effectiveness by ensuring a substantially linear output throughout the angular operating range, comparable to capacitive detectors, while minimizing interference and cost issues.
Implementation Method 1
An optical angular position detector uses a light emitter array centered on the axis to direct individual, overlapping light beams to light detectors
Implementation Method 2
a light blocker spaced in front of and parallel to the detectors and arranged to be rotated about said axis
Data Source
AI summary
An annular position detection method provides a plurality of light emitters on a first imaginary circle centered on an axis, the emitters directing individual, well-defined, overlapping light beams to a pair of light detectors positioned on a second imaginary circle centered on that axis. The detectors include pairs of diametrically opposite photosensors producing outputs depending upon the areas thereof exposed to light from the emitters. A light blocker is rotatably mounted on the axis so that the blocker blocks light to different extents of the photosensors depending upon its orientation about the axis. The outputs from all of the photosensors are processed to produce a position signal that varies with the angular position of the blocker and the relative intensities of the emitters are adjusted so that the position signal is substantially linear at all operative angles of the blocker. Apparatus for practicing the method is also disclosed.