Optical Encoder Foreign Object Robustness via Intermediary Cover
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Solution Overview
Problem
Miniaturized code patterns in optical encoders become susceptible to foreign objects, leading to reduced robustness and accuracy in detecting rotational displacement, as error correction fails with larger foreign objects and waveform accuracy decreases on incremental patterns.
Innovation Solution
An optical encoder design with a rotary plate featuring absolute and incremental patterns, where an opposing component is disposed between the rotary plate and the fixed body to reduce the gap and prevent foreign objects from entering, combined with an enclosed light-receiving part to enhance robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If code patterns are miniaturized to achieve high resolution, then measurement precision is improved, but reliability deteriorates due to susceptibility to foreign objects
Solution Approach 1:
A cover plate is introduced as an intermediary component between the code pattern and the external environment. The cover plate has a through-hole that allows light to pass through while physically blocking foreign objects from contacting the code pattern. This mediator protects the miniaturized code pattern from contamination while maintaining the high resolution capability.
Solution Approach 2:
The cover plate functions as a thin protective film or shell that covers the code pattern. This thin protective layer prevents foreign objects from reaching the code pattern while being transparent to light, thus protecting the miniaturized features without interfering with the optical measurement function.
2Measurement precision
If code patterns are miniaturized to achieve high resolution, then measurement precision is improved, but object-affected harmful factors increase due to foreign object deposition
Solution Approach 1:
The cover plate serves as a protective intermediary that physically separates foreign objects in the environment from the code pattern. The through-hole in the cover plate is sized to allow light transmission while blocking foreign objects, thus eliminating the harmful effect of foreign object deposition on miniaturized code patterns.
Solution Approach 2:
The cover plate with its through-hole creates a controlled optical pathway that is immune to environmental contamination. By using this pneumatic/optical isolation approach, foreign objects cannot reach the code pattern while light can freely pass through the designated aperture for measurement.
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 encoder achieves high robustness against foreign objects, maintaining accuracy even with miniaturized code patterns, allowing for high-resolution rotational displacement detection.
Implementation Method 1
an angle of rotation is detected by emitting light toward a code pattern of a rotary plate, and receiving the light that passes through light-transmissive portions at a light-receiving part
Implementation Method 2
an angle of rotation is detected by emitting light toward a code pattern of a rotary plate, and receiving the light reflected by light-reflective portions at a light-receiving part
Data Source
AI summary
An encoder includes: a rotary plate including a pattern for detecting rotational displacement; a light source that emits light onto the pattern; a light-receiving part including a light-receiving region that receives the light that is emitted from the light source and travels via the rotary plate; a fixed body in which the light-receiving part is provided; and an opposing component that opposes the pattern. The opposing component is disposed between the rotary plate and the fixed body.