Lens Drive Current Limiting for Speed and Heat Management
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Solution Overview
Problem
Existing lens drive systems in digital cameras with interchangeable lenses face inefficiencies due to restricted drive speed caused by maximum rated current limitations, leading to prolonged drive times and potential heat generation and malfunction.
Innovation Solution
A lens device and drive method that control optical member drives by setting current limit values within rated and supply current constraints, allowing alternating high and low current drives to complete operations quickly while preventing overheating, and enabling simultaneous drive of multiple optical members without relying on drive commands for power source operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive current is limited to the maximum rated current to prevent heat generation and malfunction, then the reliability is improved, but the drive speed decreases and the drive time becomes long
Solution Approach 1:
The patent applies periodic action by alternating between high-current drive mode and low-current drive mode in repeated cycles. The control part switches between setting the current limit value to the first current (equal to or more than rated current) and the second current (less than rated current), creating a periodic drive pattern that achieves both fast positioning and heat management
Solution Approach 2:
The patent implements dynamics by making the current limit value changeable during operation. Instead of using a fixed current limit, the control part dynamically adjusts the current limit value between two levels (first current and second current) based on the drive phase, allowing the system to adapt between speed-critical and heat-critical periods
2Loss of time
If the maximum rated current is used for drive operations, then the drive time is reduced, but heat generation and circuit malfunction risk increase
Solution Approach 1:
The patent uses periodic action to alternate between high-power operation (first current) that reduces drive time and low-power operation (second current) that reduces heat generation. This periodic switching allows the system to achieve fast positioning while managing thermal load through repeated cycles of high and low current application
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the optical member drive operation continues without interruption through the alternating current modes. The repeated first drive and second drive operations ensure the positioning task is completed continuously while managing heat, rather than stopping and restarting
3Measurement precision
If drive commands are transmitted and received between camera body and lens for each operation, then the drive precision is improved, but the processing time increases
Solution Approach 1:
The patent applies preliminary action by establishing the current limit value settings and drive mode switching logic in advance within the lens device control part. The system pre-configures the alternating current drive pattern and current limit values, so that during actual operation, the drive can proceed without real-time communication delays for each command execution
4Productivity
If multiple optical members are driven simultaneously with high current, then the productivity is improved, but the total current consumption exceeds the maximum supply current
Solution Approach 1:
The patent applies local quality by allocating different current limit values to different optical members based on their individual drive requirements and the overall current budget. The control part selectively applies the first current or second current to each optical member, ensuring that the sum of currents to all simultaneously driven members does not exceed the maximum supply current while optimizing each member's drive performance
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 approach enables rapid completion of optical member drives, such as zoom, focus, and diaphragm operations, reducing heat generation and circuit malfunctions, and allows for simultaneous driving of multiple optical members without increased processing time or communication requirements.
Implementation Method 1
If a current supplied to a motor driver (driving circuit) exceeds a rated current at the time of the drive, there is a possibility of heat generation and malfunction
Data Source
AI summary
According to an aspect of the present invention, when driving one optical member at a time, the control part sets a first current equal to or more than a rated current of the driving part and equal to or less than a maximum supply current from the image-capturing device body, or a second current less than the rated current of the driving part, for the one optical member as the current limit value, and controls the driving part so that first drive for driving the optical member for a first time by allowing the first current to serve as the current limit value, and second drive for driving the optical member for a second time by allowing the second current to serve as the current limit value after the first drive being performed, are repeated until drive of the optical member to the drive target is completed.