Autofocus Lens Backlash Detection and Compensation
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Solution Overview
Problem
Existing lens drive systems in autofocus operations face inaccuracies due to unknown backlash, leading to unnecessary extra movements and energy consumption when adjusting the lens to an in-focus position, as backlash varies among lenses and cameras and degrades over time.
Innovation Solution
A system comprising a lens drive system, an imager, contrast detectors, and a backlash detector that detects backlash by capturing images during both forward and backward lens translations, allowing precise calculation and storage of backlash data for accurate lens positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed backlash value is stored in memory for lens drive calibration, then the device complexity is reduced, but the measurement precision of lens position deteriorates due to backlash variation among lenses, cameras, and over time
Solution Approach 1:
The lens drive system performs self-calibration by automatically detecting its own backlash through bidirectional lens translation and contrast peak detection. The system uses its imaging capability to measure the actual backlash and store this self-determined value, eliminating the need for external calibration equipment or pre-stored fixed values, thereby achieving both low device complexity and high measurement precision.
2Reliability
If the lens is moved back a distance greater than sufficient to counterbalance backlash, then the lens can be repositioned, but the time and energy consumption increase due to unnecessary extra movements
Solution Approach 1:
The system implements feedback control by detecting the actual backlash value through bidirectional lens translation and contrast peak detection. This measured backlash information is fed back to the control system, which then calculates the precise compensation distance needed. The lens is moved back only by this calculated precise distance rather than a fixed excessive distance, thereby reducing time and energy consumption while maintaining positioning reliability.
3Ease of operation
If a fixed backlash compensation distance is used in contrast-detection autofocus, then the operation is simplified, but the manufacturing precision of lens positioning deteriorates due to unknown and varying backlash
Solution Approach 1:
The lens drive system performs self-calibration by automatically detecting its own backlash through bidirectional lens translation and contrast peak detection. The system uses its imaging capability to measure the actual backlash and store this self-determined value, eliminating the need for external calibration equipment or pre-stored fixed values, thereby achieving both low device complexity and high measurement precision.
4Device complexity
If backlash data is stored in lens barrel or camera body memory, then the device complexity is reduced, but the adaptability deteriorates because backlash varies with lens type, camera body, and usage conditions
Solution Approach 1:
The lens drive system performs self-calibration by automatically detecting its own backlash through bidirectional lens translation and contrast peak detection. The system uses its imaging capability to measure the actual backlash and store this self-determined value, eliminating the need for external calibration equipment or pre-stored fixed values, thereby achieving both low device complexity and high measurement precision.
Solution Approach 2:
The system performs preliminary backlash detection during an initialization or calibration phase before actual autofocus operations. By conducting this detection in advance and storing the measured backlash value, the system prepares accurate compensation data ahead of time. This preliminary action ensures that subsequent autofocus operations can use the adapted backlash value without requiring real-time recalibration, maintaining both simplicity and adaptability.
Data Source
AI summary
An autofocus device comprising includes a lens drive system for translating a lens, a first in-focus position detector for detecting a first in-focus position while translating the lens in a first direction by the lens drive system and a second in-focus position detector for detecting a second in-focus position while translating the lens in a direction opposite with respect to the first direction by the lens drive system, the second in-focus position detector operating after the first in-focus position is detected. A backlash detector detects a backlash in the lens drive system according to the first and the second in-focus positions.