Photoelectric Encoder Aperture Spatial Frequency Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photoelectric encoders suffer from reduced measurement accuracy due to the detection of unwanted harmonic components from optical gratings, which lowers the contrast and increases distortion in image formation, affecting the precision of position measurement.
Innovation Solution
The design of a photoelectric encoder that filters out unwanted harmonic components by using a specific aperture size and configuration in the imaging optical system, ensuring only the fundamental spatial frequency is detected, thereby stabilizing position measurement and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a telecentric optical system is used to form an image of the optical grating, then the relative position change can be detected, but high frequency components are generated that lower image contrast and increase distortion
Solution Approach 1:
The patent extracts and removes the harmful high frequency components (harmonics) from the optical signal by using an aperture to block these components while allowing the fundamental spatial frequency to pass through, thereby eliminating the source of measurement error
Solution Approach 2:
The patent changes the spatial frequency parameters by filtering out frequencies above the fundamental spatial frequency of the optical grating, transforming the signal to contain only the desired frequency component for accurate measurement
2Use of energy by moving object
If the aperture size is increased to allow more light through, then the signal intensity increases, but high frequency components are not filtered and measurement accuracy decreases
Solution Approach 1:
The patent optimizes the aperture size parameter to a specific value that simultaneously achieves two goals: allowing sufficient light intensity to pass through for good signal strength, and blocking high frequency components to ensure measurement accuracy
3Measurement precision
If the aperture size is decreased to filter high frequency components, then measurement accuracy improves, but the light signal intensity decreases
Solution Approach 1:
The patent determines the optimal aperture size parameter that balances signal intensity and filtering effectiveness, ensuring sufficient light passes through while blocking harmful high frequency components
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 approach enhances measurement position accuracy by eliminating high-frequency components, resulting in a more stable and precise position measurement while maintaining high contrast for the fundamental spatial frequency, thus improving the overall performance of the encoder.
Implementation Method 1
light emitted from a light source is modulated by an optical grating that is disposed on a scale at constant intervals
Implementation Method 2
the imaging optical system has a first aperture through which part of the light modulated by the optical grating is allowed to transmit, the first aperture having a size which is required when a cutoff spatial frequency
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A photoelectric encoder in which light emitted from a light source is modulated by an optical grating and the modulated light is detected by a light receiving element, includes a one-side telecentric optical system which forms an image of the light modulated by the optical grating. The imaging optical system has an aperture through which part of the light modulated by the optical grating is allowed to transmit, the aperture having a size which is required when a cutoff spatial frequency that is a spatial frequency indicating a resolution limit of the imaging optical system due to the light emitted from the light source has a value between a fundamental spatial frequency of the optical grating obtained by a Fourier transformation and a second harmonic of the fundamental spatial frequency.