Absolute Position Encoder Signal Separation via Optical MTF
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Solution Overview
Problem
Conventional absolute position measuring encoders with integrated absolute and incremental patterns require high-performance processing circuits or long operation times due to the complexity of separating these signals.
Innovation Solution
An absolute position measuring encoder with an imaging optical system generating amplitude differences between absolute and incremental pattern signals, using a signal processing system to separate these signals quickly without a high-performance circuit, by converting received light signals into multivalued digital signals and determining thresholds for binarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter is used to separate the absolute pattern signal from the received light signal, then the absolute pattern signal can be extracted, but the signal processing time increases and high-speed processing cannot be achieved
Solution Approach 1:
The patent changes the parameter of the optical system (MTF characteristics) to create amplitude differences between absolute and incremental pattern signals. By adjusting the lens MTF curve to have a cutoff frequency between the spatial frequencies of absolute and incremental patterns, the system transforms the signal separation problem from a time-consuming filtering operation to a spatial frequency-based amplitude differentiation that can be processed rapidly
Solution Approach 2:
The patent replaces the conventional low-pass filter (electronic/mechanical signal processing component) with an optical system approach. Instead of using a filter to separate signals in the time domain, the system uses the imaging optical system's MTF characteristics to separate signals in the spatial frequency domain, substituting electronic filtering with optical frequency selectivity
2Productivity
If a high-performance processing circuit is used to separate the absolute and incremental pattern signals, then the separation can be achieved, but the device complexity increases
Solution Approach 1:
The patent introduces an intermediary element - the imaging optical system with specific MTF characteristics - that mediates between the scale pattern and the light receiving element. This optical intermediary performs the signal separation function passively through its frequency-selective transmission characteristics, eliminating the need for complex active processing circuits
Solution Approach 2:
The system enables self-service signal separation where the optical system automatically differentiates between absolute and incremental pattern signals based on their spatial frequency characteristics. The light receiving element directly captures the amplitude-differentiated signals without requiring external processing intervention, making the separation process self-executing
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 fast and efficient separation of absolute and incremental pattern signals, reducing the need for high-performance processing and operation time, while maintaining accuracy.
Implementation Method 1
an imaging optical system designed to generate an amplitude difference between a light and dark signal derived from the absolute pattern and a light and dark signal derived from the incremental pattern
Data Source
Figure 1(A)~1(D)
Figure 2
Figure 3(A)~3(C)
AI summary
An absolute position measuring encoder having an ABS/INC integrated pattern obtained by integrating an absolute pattern and an incremental pattern together is provided. The absolute position measuring encoder includes an imaging optical system (lens) designed to generate an amplitude difference between a light and dark signal derived from the absolute pattern and a light and dark signal derived from the incremental pattern, and a signal processing system (comparator) for separating a received light signal from the ABS/INC integrated pattern into an absolute pattern signal and an incremental pattern signal by utilizing the amplitude difference. Accordingly, an absolute pattern signal and an incremental pattern signal can be separated off from the ABS/INC integrated pattern at a high speed with a simple processing circuit.