Optical Encoder Yaw Misalignment Detection via Signal Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical encoders with small detection heads face challenges in misalignment adjustment, especially in constrained spaces like three-dimensional measuring apparatus stages, where mechanical references are hard to set, and existing methods do not effectively detect Yaw direction misalignment without moving the detection head.
Innovation Solution
An optical encoder system with a scale having diffraction gratings and a detection head equipped with four receiver portions at different spatial phases, along with a signal processing device that generates three-phase differential signals and performs vector synthesis to detect Yaw misalignment by calculating the Lissajous radius or its squaring value, allowing for adjustment without moving the detection head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small detection head is used, then the optical encoder can be integrated into compact systems, but misalignment adjustment becomes difficult because mechanical references are hard to set
Solution Approach 1:
The patent replaces mechanical reference-based alignment methods with an optical signal processing approach. By using four receiver portions arranged in a specific pattern and processing their output signals through differential amplification and vector synthesis, the system can detect Yaw misalignment electronically without requiring mechanical references or moving the detection head during adjustment.
Solution Approach 2:
The patent introduces an intermediary signal processing mechanism that mediates between the optical signals from the four receiver portions and the final alignment detection. The signal processing device performs differential amplification to generate three-phase signals, then uses vector synthesis to calculate the Lissajous radius, which serves as an intermediary metric to quantify Yaw misalignment and guide adjustment.
2Measurement precision
If misalignment adjustment is performed by moving the detection head along the scale, then alignment can be visualized through Lissajous signals, but this method cannot be performed in constrained spaces
Solution Approach 1:
The patent performs preliminary signal processing and analysis in a resting state without moving the detection head. The four receiver portions simultaneously capture optical signals, and the signal processing device pre-processes these signals through differential amplification and vector synthesis to generate the Lissajous radius metric, enabling alignment detection to be performed before any physical adjustment occurs.
Solution Approach 2:
The patent transitions from spatial movement (moving the detection head along the scale) to signal space analysis (processing electrical signals from the receiver portions). By transforming the physical alignment problem into an electrical signal analysis problem through the four-receiver configuration and vector synthesis, the system enables alignment detection in the signal domain rather than requiring physical movement in spatial domain.
3Device complexity
If conventional signal processing is used without Yaw detection, then the system is simpler, but Yaw misalignment cannot be detected or corrected
Solution Approach 1:
The patent segments the optical signal reception function into four separate receiver portions arranged in a specific geometric pattern. This segmentation allows each receiver to capture signals with different spatial phases, and when these segmented signals are processed through differential amplification and vector synthesis, they collectively provide information about Yaw misalignment that a single receiver or simpler configuration could not detect.
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
Enables easy adjustment of detection head misalignment in the Yaw direction, improving alignment accuracy and facilitating integration into compact systems by detecting Yaw rotation without moving the detection head relative to the scale.
Implementation Method 1
coherent light emitted from the light source is diffracted by the linear scale, and an interference fringe having position information is generated
Implementation Method 2
an interference fringe having position information is generated
Implementation Method 3
a plurality of receiver portions configured to receive light reflected by or transmitted through the diffraction gratings of the scale, at different phases
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An optical encoder includes a scale (1) having diffraction gratings formed at predetermined pitches in a measurement axis direction, a detection head (2) relatively movable with respect to the scale, the detection head including a light source portion (211) configured to irradiate the scale with light, and a plurality of receiver portions (221) configured to receive light reflected by or transmitted through the diffraction gratings of the scale, at different phases, and a signal processing device (4) configured to perform signal processing to light reception signals output from the receiver portions of the detection head, to produce quadrature differential signals. The signal processing device (4) is configured to calculate alignment adjustment monitor signals corresponding to a Lissajous radius of the quadrature differential signals in order to detect misalignment of the detection head with respect to the scale.