Optical Image Stabilizer Switching Filter Transient Response
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Solution Overview
Problem
Camera modules in mobile devices face challenges with image stabilization due to bias offsets in angular velocity signals, leading to amplified errors over time, which result in image distortion and require long transient response times for correction.
Innovation Solution
An optical image stabilizer system that includes an offset remover to correct angular velocity signals, an idle state determiner to assess movement states, a switching filter to switch between high pass filters with different cut-off frequencies, and an integrator to calculate angular position signals, thereby shortening transient response times and improving stabilization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high pass filter is used to remove bias offset from angular velocity signal, then bias offset is removed, but transient response time is prolonged
Solution Approach 1:
The patent applies dynamics by switching between two different high pass filters (first and second HPF) with different cut-off frequencies based on the operating state. During stabilization time, the first HPF with higher cut-off frequency is used for faster bias offset removal, while during normal operation, the second HPF with lower cut-off frequency is used for continuous filtering. This dynamic switching resolves the contradiction between fast transient response and continuous bias offset removal.
Solution Approach 2:
The patent changes the parameter of cut-off frequency of the high pass filter based on the operating state. By adjusting the cut-off frequency parameter (higher during stabilization, lower during normal operation), the system achieves both fast transient response during initialization and effective continuous bias offset removal during operation, resolving the time-performance tradeoff.
2Measurement precision
If angular velocity signal is integrated to calculate angular position, then angular position is obtained, but errors are amplified over time
Solution Approach 1:
The patent applies preliminary action by removing the bias offset from the angular velocity signal through high pass filtering before integration. By preprocessing the signal to eliminate the DC component that would cause error accumulation during integration, the system ensures more accurate and reliable angular position calculation over time.
3Illumination intensity
If shutter speed is slowed to compensate for insufficient light, then light sensitivity is improved, but image distortion increases due to hand-shake
Solution Approach 1:
The patent applies feedback by using an angular velocity sensor to detect hand-shake vibrations and feeding this information back to the lens controller. The lens controller then adjusts the lens position in real-time to compensate for the detected vibrations, allowing the use of slower shutter speeds for better light sensitivity while maintaining image clarity through active stabilization feedback.
Data Source
AI summary
An optical image stabilizer including an offset remover configured to remove a direct current offset of an angular velocity signal and output a corrected angular velocity signal; an idle state determiner configured to determine a moving-state or an idle state of the optical image stabilizer based on the corrected angular velocity signal; a switching filter configured to filter the corrected angular velocity signal using a second filter during a stabilization time and subsequently filter the corrected angular velocity signal using a first filter switched from the second filter when the optical image stabilizer is in the moving-state; and an integrator configured to integrate the filtered corrected angular velocity signal from the switching filter to output an angular position signal.