SMA Lens Drive Control via Hysteresis Dead Zone
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Solution Overview
Problem
Existing endoscope systems face challenges in maintaining precise control over lens movement due to temperature-induced disturbances, which can cause unintended lens position changes during tele-photographing and wide-photographing operations.
Innovation Solution
A lens drive control apparatus utilizing a shape memory alloy (SMA) member with a hysteresis characteristic, where a transmitting member with a clearance along the optical axis direction transmits driving force to a lens frame, and a control section adjusts the SMA's temperature to a dead zone upon instruction cessation, ensuring stable lens positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shape memory alloy member is used to drive the lens frame, then the lens can be moved along the optical axis direction to achieve tele-photographing and wide photographing, but temperature changes cause unintended lens position changes due to hysteresis characteristics
Solution Approach 1:
A transmitting member with clearance is introduced as an intermediary between the shape memory alloy member and the lens frame. This transmitting member decouples the direct thermal-mechanical coupling, allowing the lens frame to be driven by the SMA's deformation while isolating it from temperature-induced hysteresis effects that would otherwise cause unintended position changes
Solution Approach 2:
The system exploits the hysteresis characteristic of the shape memory alloy by controlling the temperature parameters to maintain the lens frame at desired positions. By understanding and managing the temperature-deformation relationship within the hysteresis loop, the system can predict and compensate for position changes, transforming the hysteresis from a source of error into a controllable parameter
2Power
If the transmitting member is in direct contact with the lens frame, then driving force is efficiently transmitted, but temperature changes directly affect lens frame position through the shape memory alloy member
Solution Approach 1:
The transmitting member serves as a mechanical intermediary that transmits the driving force from the shape memory alloy member to the lens frame while providing thermal isolation. The clearance in the transmitting member allows it to engage only when driving force is needed, while disengaging to isolate the lens frame from temperature changes that would otherwise be transmitted through direct contact
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 solution effectively prevents lens position fluctuations due to ambient temperature changes, maintaining intended positions during both tele-photographing and wide-photographing modes, enhancing operational stability and image clarity.
Implementation Method 1
a transmitting member that transmits to the lens frame a driving force generated by a strain deformation of a shape memory alloy member
Implementation Method 2
a shape memory alloy member that exhibits a predetermined hysteresis characteristic between a temperature and an amount of deformation
Data Source
AI summary
A lens drive control apparatus of the present invention controls a lens drive system that has a lens frame that holds a lens so as to be movable forward and backward in an optical axis direction of an optical lens, and a transmitting member that transmits to the lens frame a driving force generated by a strain deformation of a shape memory alloy member that exhibits a predetermined hysteresis characteristic between a temperature and an amount of deformation. The lens drive control apparatus includes a control section that, at a timing at which an instruction that causes the lens frame to move forward or backward stops, performs control that changes a temperature of the shape memory alloy member to a temperature belonging to a dead zone of the predetermined hysteresis characteristic.