Optical Encoder Signal Processing Circuit
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Solution Overview
Problem
Conventional optical encoders using EXCLUSIVE-OR circuits for signal processing experience gate delays, leading to impedance differences and fluctuations in duty ratio, which hinder the achievement of higher resolutions and precision in detecting mover position and movement.
Innovation Solution
An optical encoder design that balances gate delays by inputting light reception signals shifted in phases of 90°, 180°, and 270° to a signal processing section, eliminating the need for NOT circuits and utilizing AND, OR, and A/D converters to produce output signals with improved duty precision and periodic precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse signals with 90° phase difference are input to an EXCLUSIVE-OR circuit to achieve twice higher resolution, then measurement precision is improved, but gate delay causes impedance differences and duty ratio fluctuations that reduce reliability
Solution Approach 1:
The patent inverts the conventional approach by using AND circuits instead of EXCLUSIVE-OR circuits, and by using 180° phase-shifted signals instead of 90° phase-shifted signals. This inversion eliminates the gate delay problem while achieving the same frequency multiplication effect, thereby resolving the contradiction between measurement precision and signal stability.
Solution Approach 2:
The patent changes the phase difference parameter from 90° to 180° between paired signals, and changes the logic operation from EXCLUSIVE-OR to AND. This parameter change fundamentally alters the signal processing characteristics, eliminating impedance differences and duty ratio fluctuations while maintaining the frequency doubling capability.
2Adaptability or versatility
If additional logical operations are performed to combine signals for reading forward and reverse rotations, then functionality is improved, but further gate delays occur that increase device complexity and reduce reliability
Solution Approach 1:
The patent performs preliminary signal processing by using 180° phase-shifted signals directly from the photodetectors, eliminating the need for additional NOT circuits and logical operations. The direction detection is achieved through the inherent phase relationships of the pre-processed signals, reducing overall circuit complexity.
Solution Approach 2:
The patent extracts the direction detection capability directly from the phase relationships of the four signals without requiring additional logical combination circuits. By taking out the unnecessary logical operations, the circuit complexity is reduced while maintaining full functionality.
3Productivity
If signal processing circuits are added to achieve higher frequency output, then productivity is improved, but gate delays cause phase differences that reduce measurement precision
Solution Approach 1:
The patent inverts the conventional signal processing approach by using AND circuits with 180° phase-shifted signals instead of EXCLUSIVE-OR circuits with 90° phase-shifted signals. This inversion eliminates gate delay-induced phase differences while achieving frequency multiplication, thereby simultaneously improving productivity and maintaining measurement 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
The solution effectively avoids phase differences due to gate delays, enabling the detection of mover movement with signals of excellent duty precision and periodic precision, achieving a frequency twice higher than the input signals.
Implementation Method 1
a light emitting section; a light receiving section having a plurality of light receiving elements placed in array along one direction in a region that can be reached by light derived from the light emitting section
Implementation Method 2
a light receiving section having a plurality of light receiving elements placed in array along one direction in a region that can be reached by light derived from the light emitting section
Data Source
AI summary
An optical encoder of the invention has an OR circuit 21 to which light reception signals A+, B+ are inputted, an OR circuit 22 to which light reception signals A−, B− are inputted, and an AND circuit 23 to which an output signal C of the OR circuit 21 and an output signal D of the OR circuit 22 are inputted. In this optical encoder, a light reception signal A− shifted in phase by 180° from the light reception signal A+, and a light reception signal B− shifted in phase by 180° from the light reception signal B+, are inputted to the OR circuit 22 of the signal processing circuit 15. Thus, the signal processing circuit 15 does not need NOT circuits for inverting the light reception signal A+ and B+. This optical encoder can avoid occurrence of phase differences due to gate delay among signals and detect the mover with signals of excellent duty and periodic precisions.