Lens Control Device Reducing Motor Current via Balance Position Calibration
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Solution Overview
Problem
Conventional image sensing devices with camera shake correction functions require high motor current to maintain lens position and shift movement, leading to increased power consumption, especially in mobile devices where power supply is limited, and fail to adapt to changes in device orientation affecting the balance position.
Innovation Solution
A lens control device that calculates and adjusts a motor current setting value using a servo computation portion and calibration computation portion to minimize the deviation of the lens position from a target position, integrating PID processing to adjust the correction offset and reduce the average motor current to zero, allowing the lens to be held and shifted near the balance position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lens is held in the reference position using a VCM, then the lens position can be maintained, but a large motor current is required leading to high power consumption
Solution Approach 1:
The patent implements periodic calibration actions at specific timing points (when camera shake correction is not performed) to adjust the correction offset. This periodic adjustment ensures the lens is held near the balance position without requiring continuous high motor current, thus reducing power consumption while maintaining position stability.
Solution Approach 2:
The patent dynamically adjusts the correction offset parameter based on calibration results to change the target position of the lens. By modifying this parameter, the system adapts to changes in device orientation and keeps the lens near the balance position, minimizing the motor current required for position maintenance.
2Adaptability or versatility
If the lens is shifted with the reference position as the center, then camera shake correction can be performed, but the balance position changes with device orientation requiring continuous current compensation
Solution Approach 1:
The system performs self-calibration by detecting the balance position through calibration routines and automatically adjusting the correction offset accordingly. This self-service mechanism allows the system to adapt to orientation changes without requiring continuous external intervention or high current compensation, reducing power consumption while maintaining correction capability.
Solution Approach 2:
The patent performs calibration actions in advance at timing points when camera shake correction is not active. This preliminary adjustment of the correction offset prepares the system for subsequent operation, ensuring the lens starts near the balance position and reducing the current required during actual camera shake correction operations.
3Reliability
If a constant drive force is applied to hold the lens in the reference position, then the lens position is stable, but the motor current increases significantly
Solution Approach 1:
The system uses feedback from calibration results to adjust the correction offset, creating a closed-loop control mechanism. By continuously monitoring and adjusting the target position based on calibration data, the system maintains lens stability near the balance position without requiring constant high drive force, thus reducing motor current while preserving position holding stability.
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
Significantly reduces power consumption for lens control by maintaining the lens position and shift movement near the balance position, adapting to changes in device orientation without the need for additional gravity sensors, and minimizing motor current usage.
Implementation Method 1
the lens is shifted by a voice coil motor (VCM) to the target position. The VCM is designed to drive (shift) the lens according to a motor current that has been fed.
Implementation Method 2
the lens 51 is present in a position (hereinafter also referred to as a balance position) where the weight of the lens 51 balances the elastic force of springs 52 and 53
Implementation Method 3
the position of the lens 51 is a position that is obtained by displacing the reference position by I=mg sin θ/2k, where m represents the weight of the lens, g represents the gravitational acceleration
Data Source
AI summary
There is provided a lens control device that feeds a motor current to a lens drive motor which drives lens according to the motor current, the lens control device including: a servo computation portion that calculates a motor current setting value such that a deviation of the position of the lens from a target position to which a correction offset has been added is reduced; a motor driver that generates the motor current according to the motor current setting value; and a calibration computation portion that adjusts the correction offset such that an average value of the motor current approaches zero.