Optical Encoder With Dynamic Steering Actuators
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Solution Overview
Problem
Conventional rotary and linear encoders are sensitive to eccentricities and variations in the distance between the optical reading head and the encoder disc or scale, leading to accuracy issues and increased costs due to stringent assembly and maintenance requirements.
Innovation Solution
An optical encoder system with a self-aligning optical reading head that includes dynamic steering actuators for focus and tracking adjustments, allowing it to accommodate disc warping and external vibrations, and utilizing a spiral data pattern track on the encoder disc for improved resolution and tolerance to contamination and physical abuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed read stations are used in conventional rotary encoders, then the device structure is simple, but the encoder becomes sensitive to eccentricities and distance variations, reducing measurement accuracy
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed read station into a dynamic system with voice coil actuators that enable real-time positioning adjustments. The read station can now move radially and axially to compensate for disc eccentricity and maintain optimal reading position, resolving the contradiction between measurement precision and device complexity by introducing controlled mobility rather than static rigidity
Solution Approach 2:
The patent implements feedback through sensors that detect the actual reading position and disc eccentricity, feeding this information back to the voice coil actuators. This closed-loop control system continuously adjusts the read station position to maintain accurate measurement despite disc variations, achieving high measurement precision while managing device complexity through intelligent control
2Measurement precision
If multiple heads are used to minimize sensitivity to eccentricity, then measurement accuracy improves, but the device complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling a single read station to compensate for its own positioning errors through voice coil actuators. The system self-adjusts to maintain optimal reading position without requiring multiple redundant heads, achieving high measurement accuracy while reducing device complexity through self-correcting capability
Solution Approach 2:
The patent changes the operational parameters of the read station by introducing controlled positional variations through voice coil actuators. Instead of using multiple heads at fixed positions, the system varies the reading position dynamically to compensate for eccentricity, achieving the same measurement accuracy with fewer components
3Measurement precision
If stringent surface flatness requirements are imposed on the encoder disc, then distance variation sensitivity is reduced, but manufacturing cost and assembly difficulty increase
Solution Approach 1:
The patent applies dynamics by introducing axial movement capability to the read station through voice coil actuators. This allows the read station to dynamically adjust its distance from the disc surface, compensating for disc flatness variations without requiring stringent manufacturing tolerances, thereby improving ease of manufacture while maintaining measurement precision
Solution Approach 2:
The system employs self-service through automatic distance compensation using voice coil actuators that adjust the read station position based on detected disc surface variations. This self-adjusting mechanism eliminates the need for precise manual assembly and stringent disc flatness requirements, reducing manufacturing complexity while maintaining measurement accuracy
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 system achieves higher resolution and reduced sensitivity to misalignment and contamination, with modular construction and reduced maintenance needs, while reusing optical storage manufacturing tools to lower production costs.
Implementation Method 1
A second arrangement is to place the detectors and the light source on the same side of the disc. In this reflective scheme, the disc is constructed in a way that the disc reflects varying amounts of light back to the optical detectors.
Implementation Method 2
an optics assembly for interrogating the optical disc and providing an output signal indicative of data received from the interrogation of the optical disc
Data Source
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AI summary
An improved optical decoder uses an optical pick-up unit that provides for degrees of freedom in the tracking and focus axes that are unavailable in conventional optical encoders thereby improving the encoders' performance. In an embodiment the encoder employs an optical disc marked with pits and lands which may be arranged in a spiral pattern. The optical disc is mounted on the shaft whose motion is to be monitored by the optical encoder. The encoder may be arranged to read the markings on the optical disc using the three-beam pickup method.