Reflective Encoder Scale with Overlapping INC and ABS Patterns
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Solution Overview
Problem
Existing photoelectric encoders face issues with large size due to separate tracks for incremental (INC) and absolute (ABS) patterns, leading to detection accuracy problems and temperature-induced detector misalignment, and multi-color minute structures do not apply to photoelectric encoders effectively.
Innovation Solution
A reflection type encoder with overlapping INC and ABS patterns on a single track using dielectric substances of different thicknesses, where light reflection is optimized at specific wavelengths to minimize interference and improve detection accuracy, utilizing silicon oxide with thicknesses of 430nm and 330nm for 880nm and 660nm wavelengths respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If INC pattern and ABS pattern are disposed on separate tracks, then both patterns can be detected, but the encoder scale becomes large-sized
Solution Approach 1:
The patent merges INC pattern and ABS pattern onto a single track by forming patterns with different dielectric substance thicknesses (first thickness for INC, second thickness for ABS) on the same scale surface. This allows both patterns to be detected simultaneously using a single light source and detector, eliminating the need for separate tracks and reducing the overall encoder scale size.
Solution Approach 2:
The patent applies local quality by varying the dielectric substance thickness at different locations on the scale. The first pattern has a first dielectric thickness optimized for INC detection, while the second pattern has a second dielectric thickness optimized for ABS detection. This local variation enables wavelength-dependent reflection characteristics that allow single-track multi-pattern detection.
2Adaptability or versatility
If part of INC pattern is fractured to create ABS data, then ABS pattern can be formed, but detection accuracy of INC displacement deteriorates
Solution Approach 1:
Instead of fracturing the INC pattern, the patent segments the dielectric substance thickness into distinct regions: a first thickness region for INC pattern and a second thickness region for ABS pattern. This segmentation allows both patterns to maintain their full functional integrity without相互 interference, as each pattern type responds optimally to its designated wavelength.
3Adaptability or versatility
If detectors are disposed apart in axial direction, then both INC and ABS detection is possible, but detection values disagree due to temperature-induced interval changes
Solution Approach 1:
The patent combines both INC and ABS detection functions into a single detector by using wavelength-multiplexed reflection patterns. Since both patterns are on the same track and detected by the same detector, temperature-induced interval changes affect both measurements equally, eliminating the disagreement problem that occurs with separated detectors.
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 enables downsizing of the encoder scale while maintaining or improving detection accuracy by ensuring the detection center axes align, reducing pattern interference, and allowing for reliable position detection without deviation between ABS and INC patterns.
Implementation Method 1
the reflected light of each wavelength has a different brightness in accordance with the differences in the thickness of the dielectric substance
Implementation Method 2
the thickness of each of the plurality of patterns is set such that the reflected light of each wavelength has a different brightness in accordance with the differences in the thickness of the dielectric substance
Data Source
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AI summary
A reflection type encoder, which receives a plurality of light-receiving signals from a single scale, includes a light source, a scale having a plurality of patterns formed thereon to which light is irradiated from the light source, and a light-receiving element for receiving light reflected from each of the plurality of patterns, wherein a plurality of patterns each having different thicknesses are formed on a single track of the scale by using a dielectric substance, light of a plurality of wavelengths each having different brightnesses in accordance with differences in the thickness of the dielectric substance is irradiated from the light source, and a light-receiving signal is obtained for the respective thicknesses of the dielectric substance. Therefore, the scale can be downsized by overlapping a plurality of patterns on the same track.