Optical Encoder Reflectance Target Single-Side Sensor
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Solution Overview
Problem
Existing optical encoders require multiple LEDs and photodetectors, leading to a large form factor, high cost, and vulnerability to vibrations, which cause errors in signal generation.
Innovation Solution
An optical encoder system that measures reflectance from a moving target using a single emitter and sensor on the same side, reducing the number of components and increasing alignment tolerance, thus minimizing the impact of vibrations and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple LEDs and photodetectors are used to encode position, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple encoding functions into a single target structure with varying reflectance properties. Instead of using multiple separate LEDs and photodetectors, a single light source and single sensor detect reflectance variations from different zones of the target, achieving the same position encoding with fewer components.
Solution Approach 2:
The patent changes the encoding parameter from light transmission (binary presence/absence) to light reflectance (continuous variation). The target uses zones with different reflectance values to encode position information, allowing a single sensor to detect multiple position states through reflectance intensity variations rather than requiring multiple sensors.
2Measurement precision
If multiple LEDs and photodetectors are arranged on opposite sides of the target, then measurement precision is improved, but the form factor and bill of materials increase
Solution Approach 1:
The patent merges the light source and sensor arrangement from opposite sides of the target to the same side. The single light source illuminates the target and the single sensor detects reflected light, eliminating the need for separate transmitter and receiver housings on opposite sides of the target.
Solution Approach 2:
The patent inverts the optical path from transmission-based (light passing through target) to reflection-based (light bouncing off target). This allows the light source and sensor to be positioned on the same side, viewing the target from one direction rather than requiring opposing positions.
3Measurement precision
If multiple components are used for position encoding, then measurement precision is improved, but vulnerability to vibrations increases
Solution Approach 1:
The patent reduces the number of separate components that can become misaligned due to vibration. By using a single light source and single sensor instead of multiple LEDs and photodetectors, there are fewer components that can shift relative to each other, reducing vibration-induced measurement errors.
Solution Approach 2:
The patent switches from transmission optics to reflection optics, which inherently reduces sensitivity to alignment errors. In reflection mode, the light path is shorter and involves fewer critical alignment points between components and the target, making the system more robust to vibrations and mechanical tolerances.
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 system achieves a compact design with reduced costs, improved accuracy, and enhanced resistance to vibrations, allowing precise position determination through varying reflectance patterns.
Implementation Method 1
an emitter positioned on a first side of the target to illuminate the target
Implementation Method 2
a sensor positioned on the first side of the target to sense a reflectance from the target
Implementation Method 3
a movable target arranged to provide a varying reflectance dependent on a position of the target within the system
Data Source
AI summary
An optical encoder system is disclosed comprising a movable target arranged to provide a varying reflectance dependent on a position of the target within the system. An emitter is positioned on a first side of the target to illuminate the target and a sensor is positioned on the first side of the target to sense a reflectance from the target, wherein the sensed reflectance is dependent on the position of the target within the system. Also disclosed are a target and a sensor module for use in such a system, a device comprising such a system and a method of determining the position of a moving target using such a system.