Optical Encoder Intermediate Pattern for Assembly Error Tolerance
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Solution Overview
Problem
Optical encoders face reduced position detection accuracy due to assembly errors affecting the distance between the scale and sensor, leading to fluctuations in signal amplitude and phase relations.
Innovation Solution
An optical encoder design featuring a light-receiving element array with multiple groups of light-receiving elements and an intermediate pattern with specific light intensity distributions, including a first pattern with a shorter spatial period and a second pattern with a longer spatial period, to stabilize signal amplitude and phase, thereby minimizing the impact of assembly errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mask with multiple slits is provided between the scale and sensor to produce sinusoidal signals with shorter periods, then position detection resolution is improved, but assembly errors cause fluctuations in signal amplitude and phase that deteriorate position detection accuracy
Solution Approach 1:
The patent changes the spatial period parameter of the intermediate pattern to be different from both the light-receiving element pitch and the sinusoidal signal period. This parameter modification makes the spatial image period insensitive to distance variations caused by assembly errors, thereby maintaining signal amplitude and phase stability while preserving high resolution capabilities
Solution Approach 2:
The patent introduces an intermediate pattern as a mediator component between the scale and the sensor. This intermediate pattern with its specific spatial period acts as a buffer that decouples the relationship between the scale-sensor distance and the spatial image period, preventing assembly errors from directly affecting signal quality
2Manufacturing precision
If the distance between the scale and sensor varies due to assembly errors, then the spatial image period fluctuates, but this causes amplitude reduction and phase relation changes in position detection signals
Solution Approach 1:
The patent modifies the spatial period parameter of the intermediate pattern to create a decoupled relationship where the spatial image period on the sensor does not directly depend on the scale-sensor distance. This parameter change ensures that assembly errors in positioning do not translate into signal amplitude or phase variations
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 design enhances position detection resolution and accuracy by suppressing amplitude and phase fluctuations, ensuring high-resolution position detection despite assembly errors.
Implementation Method 1
a scale provided with a scale pattern that reflects or transmits light from a light source
Implementation Method 2
a scale provided with a scale pattern that reflects or transmits light from a light source
Implementation Method 3
An intermediate pattern is provided between the scale and the sensor, the intermediate pattern including a first pattern to form a first light intensity distribution with a first spatial period
Implementation Method 4
An intermediate pattern is provided between the scale and the sensor, the intermediate pattern including a first pattern to form a first light intensity distribution with a first spatial period
Data Source
AI summary
The optical encoder includes a scale provided with a scale pattern reflecting or transmitting light from a light source, and a sensor receiving the light from the scale pattern. The sensor is provided with a light-receiving element array. The light-receiving element array includes multiple light-receiving element groups with a pitch P. Each group is constituted by two or more light-receiving elements whose outputs are added together. An intermediate pattern is provided between the scale and the sensor. The intermediate pattern includes a first pattern to form a first light intensity distribution with a first spatial period shorter than the pitch P on the light-receiving element array and a second pattern to form a second light intensity distribution with a second spatial period longer than the pitch P on the light-receiving element array.