Variable-Power Optical Lens Drive With Axial Play Compensation
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Solution Overview
Problem
Existing optical devices suffer from imprecise control of the motion of the control member due to axial play in the motor's output shaft, leading to inaccurate positioning and optical power control, especially when encoder-based motion control is used.
Innovation Solution
The optical device incorporates a driving member mounted rotatably in the framework with biasing means, such as rolling bearings and spring washers, to maintain the driving member in a predetermined axial position along the output shaft, ensuring precise control of the control member's motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If axial play is designed into the motor's output shaft to ensure proper functioning in a wide range of temperatures, then the motor can operate reliably across temperature variations, but the positioning of the driving member becomes inaccurate and control precision deteriorates
Solution Approach 1:
A biasing element (spring) is introduced as an intermediary component between the driving member and the motor's output shaft. This spring absorbs the axial play and positional variations, maintaining continuous contact and force transmission while compensating for temperature-induced dimensional changes in the motor components
Solution Approach 2:
The system changes the physical state of the connection from rigid to elastic by introducing a spring element. This allows the connection to adapt its stiffness and maintain optimal contact pressure across varying temperatures, transforming the rigid dimensional constraints into a flexible force-based connection
2Extent of automation
If encoder-based motion control is used to determine angular position of the output shaft, then automated control capability is improved, but the system cannot compensate for axial play and positioning accuracy deteriorates
Solution Approach 1:
The biasing element acts as a mechanical intermediary that ensures continuous, play-free contact between the driving member and control member. This mechanical compensation works in parallel with the encoder-based automated control, providing physical precision that complements the electronic position feedback system
3Manufacturing precision
If the driving member is rigidly fixed to the motor's output shaft, then positioning precision is improved, but the system cannot accommodate temperature variations and reliability deteriorates
Solution Approach 1:
The connection between the driving member and motor output shaft is changed from static and rigid to dynamic and flexible through the spring element. This allows the system to adapt its mechanical characteristics in real-time, maintaining optimal engagement while accommodating thermal expansion and contraction of motor components
Data Source
Figure 1~3
Figure 4~5
AI summary
An optical device (2) comprises a lens (52) and a control member (62) configured such that motion of the control member (62) produces a change in the optical power provided along an optical axis of the lens (52). The optical device (2) further comprises a framework (8), a motor (54) and a driving member (60). The motor (54) includes an output shaft (58) rotatively coupled to said driving member (60). The motor (54) and the control member (62) are mounted in the framework (8) such that the driving member (60) and the control member (62) mechanically cooperate. The driving member (60) is rotatably mounted in the framework (8). The optical device (2) comprises biasing means (83) for maintaining the driving member (60) in a predetermined axial position along the output shaft axis and relative to the framework (8). This optical device can be used in an optometric equipment.