Rotary Optical Encoder Using Smooth Light Patterns for Clean Sensing
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Solution Overview
Problem
Existing rotary optical encoders face challenges in achieving high accuracy and robustness against contamination and manufacturing complexity, particularly in applications requiring small size and precise angular position feedback.
Innovation Solution
A rotary optical encoder with a rotating optical element that generates a smoothly varying illumination pattern, such as a sinusoidal pattern, using reflective or diffractive optics, which is immune to contamination and reduces manufacturing complexity by employing quadrature detectors for common-mode noise rejection, enabling high-resolution angular position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional rotary optical encoders are used, then angular position detection is achieved, but accuracy is limited and susceptibility to contamination increases
Solution Approach 1:
The patent replaces traditional mechanical grating structures with an optical field-based encoding system. A light beam passes through a stationary optical element with an angularly varying transmissive pattern, creating a position-dependent light pattern that is detected by a detector. This substitution of mechanical moving gratings with a stationary optical element and modulated light field reduces susceptibility to contamination while maintaining high measurement precision for angular position detection.
Solution Approach 2:
The patent introduces a stationary optical element with an angularly varying transmissive pattern as an intermediary between the light source and detector. This optical element modulates the light beam to create position-dependent patterns that encode angular information, serving as a mediator that enables high-accuracy position detection without requiring mechanical movement of gratings, thereby improving reliability against contamination.
2Measurement precision
If high accuracy angular position detection is achieved, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent extracts the angular encoding function from a complex mechanical grating structure and concentrates it into a stationary optical element with a specific transmissive pattern. By removing the need for multiple moving mechanical components and reducing the system to a stationary optical element modulating a light beam, the device complexity is reduced while maintaining high measurement precision for angular position detection.
Solution Approach 2:
The patent replaces complex mechanical grating systems with a stationary optical element that uses optical modulation to achieve angular position encoding. This substitution eliminates the need for precise mechanical alignment and movement of multiple gratings, simplifying the overall device structure while preserving high measurement accuracy through optical field manipulation.
3Volume of moving object
If compact encoder design is implemented, then device size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses a stationary optical element with a pre-defined angularly varying transmissive pattern that acts as a template for angular encoding. This pattern can be manufactured with high precision using standard photolithography or other precision fabrication techniques, and once manufactured, it provides consistent encoding without requiring high-precision mechanical assembly, thus enabling compact design while managing manufacturing precision requirements.
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 encoder provides high accuracy and robustness against contamination, reduces manufacturing complexity, and enables compact designs suitable for applications like surgical robot end effectors, with absolute position detection without the need for additional index indicators.
Implementation Method 1
the optically responsive pattern is a gradient pattern as may be created using a patterned array of pixels, i.e., small areas of reflective material on a substrate
Implementation Method 2
using reflective or diffractive optics, which is immune to contamination
Data Source
AI summary
A rotary optical position encoder includes a source/detector assembly having a source and a detector, the source producing a light beam, the detector receiving the beam with a position-dependent pattern therein and producing position-indicating detector output signals. An optical element is configured for rotation relative to the source and detector, the optical element including an angularly varying optically responsive pattern operative in response to the light beam from the source to produce the position-dependent pattern in the light beam for detection by the detector. The position-dependent pattern has a smoothly varying characteristic as a function of angle, corresponding to the angularly varying optically responsive pattern of the optical element, to emphasize a fundamental component of rotational position in the position-indicating detector output signals.