Encoder Using Opposite-Direction Interference Fringes to Cancel Wavelength Drift
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Solution Overview
Problem
Scan-type encoders experience significant errors in position detection due to wavelength drifts caused by heat or mechanical variations, leading to reduced precision, especially in high-resolution applications.
Innovation Solution
The encoder design incorporates a light modulation section and a moving member with multiple light receiving sections, where interference fringes generated in different regions move in opposite directions, allowing for improved position detection precision by canceling out modulation-related errors through interference intensity signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light beam is used for position detection, then the system is simple, but wavelength drift causes large position detection errors
Solution Approach 1:
The patent divides the position detection function into multiple independent channels by using multiple light beams (first light beam and second light beam) that are deflected into different regions. Each light beam creates its own interference fringe pattern, allowing independent analysis of wavelength drift effects in each channel and enabling compensation through comparative measurement.
Solution Approach 2:
The patent introduces a light deflection member as an intermediary component that directs different light beams into different regions of the moving member. This intermediary structure enables the creation of multiple interference fringes with opposite movement directions, which are then used to cancel out wavelength drift errors through mathematical processing of the interference signals.
2Measurement precision
If light modulation is applied to improve detection capability, then detection sensitivity increases, but modulation-related errors are introduced
Solution Approach 1:
The patent converts the harmful modulation-related errors into a beneficial feature by using the modulation signal not just for detection, but also for error compensation. The interference fringes generated by multiple light beams move in opposite directions, creating interference patterns that contain information about both position and modulation effects. By analyzing these patterns, the system can separate and compensate for wavelength drift and modulation-related errors.
Solution Approach 2:
The patent implements feedback by using the modulation signal itself to compensate for its own harmful effects. The interference fringe patterns generated by the modulated light beams contain information about the modulation characteristics, which are then fed back into the detection system to correct for wavelength drift and other modulation-related errors, thereby improving overall measurement precision.
3Measurement precision
If multiple light beams are used to reduce wavelength drift errors, then position detection precision improves, but the number of light receiving sections increases
Solution Approach 1:
The patent merges the detection function of multiple light beams into a unified processing system. Instead of requiring separate processing circuits for each light beam, the interference fringes from multiple beams are combined and processed together through a single evaluation mechanism that analyzes the relative movements and phase differences, thereby reducing the overall complexity while maintaining high precision.
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 effectively reduces errors in position detection, enhancing the precision of the encoder's results by eliminating modulation-related errors, even when the wavelength center drifts, and simplifies the system by eliminating the need for compensation mechanisms.
Implementation Method 1
a light modulation section which modulates at least a portion of light that is emitted from a light source section
Implementation Method 2
at least two light receiving sections which respectively receive interference fringes that are generated in at least two regions on the moving member
Implementation Method 3
comparing the reflected light or the transmitted light with the modulation signal
Implementation Method 4
interference fringes that are generated in at least two regions on the moving member
Implementation Method 5
at least two light receiving sections which respectively receive interference fringes
Data Source
AI summary
An encoder includes: a light modulation section which modulates at least a portion of light that is emitted from a light source; a moving member which has an incidence plane, on which a plurality of light beams of the light incident, and is relatively movable in at least one direction; and at least two light receiving sections which respectively receive interference fringes that are generated in at least two regions on the moving member, wherein the light enters into the moving member such that at least two interference fringes move in opposite directions on the moving member in accordance with a modulation by the light modulation section.