Optical Encoder Lens Array Signal Overlap for Phase Error Reduction
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Solution Overview
Problem
Conventional optical encoders using lens arrays with small-diameter lenses face challenges in maintaining accurate phase analysis due to image isolation at lens boundaries and are prone to phase errors and high calculation complexity, especially when mounted in microcomputers.
Innovation Solution
An optical encoder design that includes a lens array with a first and second lens arrayed parallel to each other, where a signal generator creates overlapping sine wave signals from each lens, allowing for accurate displacement calculation without complex corrections, using a signal combiner and displacement amount calculator based on inter-regional distances, enabling high-accuracy phase analysis via Fourier transform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a lens array with multiple small-diameter lenses is used instead of a single lens, then the size of the optical encoder is reduced, but image isolation occurs at the boundaries between lenses and measurement precision deteriorates
Solution Approach 1:
The patent divides the optical system into multiple small-diameter lenses arranged in an array, where each lens captures light from a specific region of the scale. This segmentation allows the optical encoder to be compact while maintaining measurement capability through coordinated signal processing of all lens outputs.
Solution Approach 2:
The patent combines the signals from multiple isolated lens images through coordinate transformation and superposition. By merging the discrete signals into a unified measurement signal, the system achieves continuous measurement capability despite the segmented lens structure, resolving the image isolation problem.
2Device complexity
If conventional phase analysis methods are used with lens array signals, then calculation complexity increases due to isolated images, but reliability of phase analysis deteriorates due to boundary effects
Solution Approach 1:
The patent replaces complex mechanical signal processing with mathematical coordinate transformation. By substituting the physical arrangement problem with a mathematical transformation approach, the system achieves reliable phase analysis without the complexity of handling isolated images through traditional methods.
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 enables high-accuracy calculation of relative displacement between the scale and head in optical encoders using lens arrays, reducing phase errors and calculation complexity, and facilitating integration with microcomputers.
Implementation Method 1
a lens array including a first lens that forms an image that arrives via the scale pattern on the image capturer and a second lens arrayed parallel to the first lens along the measurement direction and that forms an image that arrives via the scale pattern on the image capturer
Implementation Method 2
the head includes a light source that emits light toward the scale, an image capturer that captures an image of the light from the light source that arrives via the scale
Data Source
AI summary
An optical encoder includes a scale, a calculator, and a head having a light source, an image capturer, and a lens array having first and second lenses. The calculator includes a signal generator, an extractor, a signal combiner, and a displacement calculator. The signal generator generates a sine wave signal. The extractor extracts first and second regions. The signal combiner, based on an inter-regional distance, uses a sine wave signal of the second region to generate a sine wave signal that extends to a first end of the first region such that the generated sine wave signal overlaps with a sine wave signal of the first region. The signal combiner also combines the sine wave signal of the first region with the generated sine wave signal. The displacement calculator calculates an amount of relative displacement based on the sine wave signal that is combined by the signal combiner.