Photoelectric encoder
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photoelectric encoders experience position detection errors due to stains on the scale and defects in the grating, which cause imbalances in output signals and direct current offsets in Lissajous signals.
Innovation Solution
The use of 'N' light-receiving elements arranged in an array to output bright and dark signals of multiple phases, with sinusoidal wave fitting to digitalize and process these signals, allowing for continuous position detection and error prevention through noise filtering and least-squares method fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If arctangent calculation is used for position detection, then position measurement is achieved, but position detection errors occur due to stains on the scale and defects in the grating
Solution Approach 1:
The patent changes the calculation method from arctangent to a least-squares fitting method that minimizes the sum of squared differences between measured and theoretical signal values. This parameter change in the computational approach makes the system robust against signal imbalances caused by stains and grating defects, thereby maintaining measurement precision while improving reliability under contamination conditions.
2Reliability
If light-receiving elements are arranged in an array to output N-phase signals, then position detection robustness is improved, but device complexity increases
Solution Approach 1:
The patent divides the light-receiving unit into multiple light-receiving elements arranged in an array, with each element contributing to N-phase signal generation. This segmentation allows the system to capture phase information from multiple spatial positions simultaneously, improving robustness against local contamination while distributing the functional load across multiple simpler components rather than requiring a single complex element.
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 approach prevents position detection errors by eliminating the need for arctangent calculations and reducing the impact of signal imbalances, enabling continuous detection even with stains or grating defects, and allows for optional light-receiving element pitch determination independent of the scale pitch.
Implementation Method 1
bright and dark signals of the 'N' phases can be output by sweeping the output of the respective light-receiving elements, in which incident measurement light is photoelectrically converted
Data Source
AI summary
The present invention relates to a photoelectric encoder including a scale having a grating (incremental pattern) of a predetermined pitch formed thereon and a light source (light-emitting element) and a light-receiving unit, which are relatively displaceable with respect to the scale, wherein light-receiving elements of the light-receiving unit output bright and dark signals of “N” phases, and the phases are detected by fitting a sinusoidal wave function having a fixed period to the bright and dark signals of “N” phases, thereby reducing a position detection error resulting from stains on the scale and/or defects of the grating.