Lens Driving Apparatus Position Compensation via Feedback Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lens driving apparatuses face challenges in maintaining accurate positional relationships between magnification-varying and focus lenses due to backlash, manufacturing errors, and individual variability of the stepping motor, leading to image plane variation and defocusing during zoom operations.
Innovation Solution
A lens driving apparatus and control method that includes a zoom operating member, stepping motor, zoom controller, focus actuator, focus controller, memory for cam data, and a zoom position detector to perform open-loop control of the stepping motor and focus actuator based on actual lens positions and cam data, ensuring accurate compensation for image plane variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the output torque of the stepping motor is lowered to reduce power consumption, then power consumption decreases, but step-out occurs more easily when lens driving load increases, causing loss of lens position control accuracy
Solution Approach 1:
The patent applies feedback control by detecting the actual lens position with a position sensor and comparing it with the target position. When step-out or tooth skip occurs, the system detects the position deviation and corrects the stepping motor control based on the detected position, enabling accurate lens position control to be maintained even with lower motor torque
Solution Approach 2:
The patent replaces pure mechanical positioning (based on counting driving pulses) with a detection-and-correction system. Instead of relying solely on the mechanical relationship between motor pulses and lens position, the system uses position sensors to detect actual positions and corrects control commands accordingly, substituting mechanical precision requirements with sensor-based feedback
2Force
If the engagement pressure of the rack with respect to the lead screw is lowered to reduce the lens driving load, then lens driving load decreases, but tooth skip occurs more easily due to impact, causing loss of lens position control accuracy
Solution Approach 1:
The position sensor provides continuous feedback on the actual lens position. When tooth skip occurs due to lowered engagement pressure, the feedback system detects the position deviation and corrects the control, maintaining accurate lens positioning despite the reduced mechanical engagement pressure
Solution Approach 2:
The system prepares correction mechanisms in advance by continuously monitoring lens position. When impact causes tooth skip, the pre-established feedback system immediately detects and corrects the position error, cushioning against the harmful effects of reduced engagement pressure
3Ease of manufacture
If backlash and manufacturing errors are present in the driving mechanism, then the device complexity and manufacturing ease are improved, but mismatch between driving pulse number and actual lens position occurs, causing defocusing during zoom operations
Solution Approach 1:
The position sensor detects the actual lens position regardless of backlash or manufacturing errors in the driving mechanism. The feedback system uses this detected position to correct control commands, compensating for the cumulative effects of backlash and manufacturing tolerances to maintain accurate lens positioning
Solution Approach 2:
The system creates a digital copy of the actual lens position through sensor detection and uses this information to generate corrected control commands. This informational copy allows the system to compensate for physical imperfections in the mechanical driving mechanism
Data Source
AI summary
The lens driving apparatus moves a magnification-varying lens and moves a focus lens to compensate for image plane variation caused by movement of the magnification-varying lens. The apparatus includes a zoom operating member, a stepping motor, a zoom controller controlling drive of the stepping motor, a focus actuator moving the focus lens, a focus controller controlling drive of the focus actuator, a memory storing cam data to compensate for the image plane variation, and a zoom position detector. During a magnification variation operation, the zoom controller performs open-loop control of the drive of the stepping motor based on an operation amount of the zoom operating member, and the focus controller controls the drive of the focus actuator based on the actual position of the magnification-varying lens detected by the zoom position detector, and the cam data.