Absolute Position Encoder Using Separated Wavelengths
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Solution Overview
Problem
Existing absolute position encoders face limitations in achieving a long measuring range while maintaining high resolution and robustness, especially in compact low-power devices, due to cross-talk errors and signal isolation difficulties caused by using spatial wavelengths that are too similar.
Innovation Solution
The proposed solution involves a signal modulating scale pattern with a coarse and fine periodic pattern component, where the spatial wavelengths are not as close to each other as in prior art, allowing for a longer absolute measuring range without compromising resolution, achieved by setting an integer m greater than 1, which alleviates signal separation and cross-talk issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If two spatial wavelengths λ1 and λ2 that are very similar are used to achieve a long absolute measuring range, then the measuring range is extended, but cross-talk errors increase and signal isolation becomes difficult
Solution Approach 1:
The patent changes the fundamental parameter of wavelength separation by introducing a large integer m (≥2) to create a synthetic wavelength relationship λ2 ≈ λ1/m. This parameter change transforms the wavelength relationship from near-equality (λ1≈λ2) to significant separation (λ2≈λ1/m), thereby reducing cross-talk errors and improving signal isolation while maintaining long measuring range capability
Solution Approach 2:
The patent segments the measurement function into two distinct wavelength components with deliberately separated wavelengths. By using λ1 and λ2 that are not similar (with λ2≈λ1/m), the system can independently resolve signals from each wavelength component, effectively segmenting the signal processing task and reducing interference between components
2Length of stationary object
If two spatial wavelengths that are very similar are used, then the synthetic beat wavelength is maximized, but resolution and accuracy are limited due to cross-talk error
Solution Approach 1:
The patent fundamentally changes the wavelength parameter relationship by introducing a large integer m (≥2), transforming the synthetic wavelength from λABS = λ1·λ2/(λ2-λ1) (which requires λ1≈λ2 for long range) to a system where λ2≈λ1/m. This parameter change enables both long measuring range and high resolution by eliminating the cross-talk errors that limit precision when wavelengths are similar
3Length of stationary object
If wavelengths are chosen to be very similar to maximize measuring range, then the beat wavelength is extended, but signal discrimination becomes difficult
Solution Approach 1:
The patent applies parameter change by introducing a large integer m (≥2) to create significant wavelength separation (λ2≈λ1/m). This transformation makes signal discrimination straightforward since the wavelengths are no longer similar, allowing easy differentiation between the two wavelength components in the detected signal while maintaining extended measuring range capability
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 configuration enhances the range-to-resolution ratio and improves signal discrimination and signal-to-noise ratio, enabling a longer measuring range with improved accuracy and robustness in compact encoders.
Implementation Method 1
a detector configured to provide detector signals in response to the signal modulating scale pattern
Data Source
AI summary
An electronic absolute position encoder includes a scale extending along a measuring axis direction (MA) and including a signal modulating scale pattern defining a corresponding absolute range R along MA, a detector including sensing elements arranged along MA and configured to provide detector signals which respond to the signal modulating scale pattern, and a signal processing configuration that determines an absolute position of the detector along the scale based on the detector signals. The signal modulating scale pattern includes a coarse periodic pattern component as a function of position along the scale having a spatial wavelength λC, wherein n*λC=R and n is an integer, and a fine periodic pattern component as a function of position along the scale having a spatial wavelength λF, wherein (mn+1)*λF=R and m is an integer that is at least two. The wavelengths λC and λC may be widely separated.