Dynamic Cut-off Frequency Adjustment for Image Shake Correction
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Solution Overview
Problem
Existing image shake correction technologies face challenges during panning operations, leading to incomplete correction and discomfort due to swing-back, especially when using angular velocity sensors, as they struggle to differentiate between intentional camera movements and hand shake, resulting in inadequate low-frequency correction and increased costs with high-precision sensors.
Innovation Solution
An image shake correcting device that divides the detection signal into frequency components and adjusts filter cut-off frequencies based on panning or tilting speed, generating a control signal to effectively correct large shakes by combining signals from high and low-frequency components, preventing the correcting lens from exceeding its movable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the correcting lens is driven based on only the shake detection signal, then the image shake correction is performed on large shake during panning operation, but the target position of the correcting lens may exceed the movable range and cause swing-back
Solution Approach 1:
The patent changes the parameter of cut-off frequency dynamically based on detection results. When panning operation is detected, the cut-off frequency is increased to exclude low-frequency components from the correcting lens drive, preventing the lens from moving beyond its movable range and causing swing-back, while still maintaining correction effectiveness for the detected shake.
Solution Approach 2:
The patent introduces an intermediary processing stage between the shake detection signal and the correcting lens drive. A signal processing based filter with adjustable cut-off frequency acts as an intermediary to selectively remove problematic low-frequency components while preserving the corrective signal for the correcting lens.
2Reliability
If the image shake correction is resumed after panning operation, then the correcting lens is moved by the shake detection signal, but the residue signal from HPF or integrator causes swing-back
Solution Approach 1:
The patent dynamically changes the cut-off frequency parameter of the filter based on the detected operation state. After panning operation, by adjusting the cut-off frequency, the system prevents residue signals from HPF or integrators from causing swing-back, ensuring smooth resumption of image shake correction without harmful oscillations.
3Measurement precision
If a crystal gyro sensor is used to reduce offset and temperature fluctuation, then the position accuracy is improved, but the cost increases
Solution Approach 1:
The patent changes the operational parameters (cut-off frequency) to compensate for sensor imperfections. By dynamically adjusting the filter characteristics based on detected operation states, the system achieves accurate image shake correction using conventional angular velocity sensors, eliminating the need for expensive crystal gyro sensors while maintaining measurement precision.
Solution Approach 2:
The patent substitutes a mechanical solution (high-precision crystal gyro sensor) with a signal processing solution (dynamic filter parameter adjustment). By using signal processing to compensate for sensor limitations, the system achieves the same level of performance at lower cost.
4Reliability
If the electronic image shake correction is not performed, then the correcting lens drive range is sufficient, but the low-frequency correction performance deteriorates
Solution Approach 1:
The patent dynamically changes the cut-off frequency parameter based on the detected operation state. During panning operation, the cut-off frequency is increased to prioritize correcting lens drive range, while in normal operation, the cut-off frequency is lowered to maintain effective low-frequency correction performance, achieving both goals under different conditions.
Data Source
AI summary
This image pickup apparatus performs feedback control so that a position of a shake correcting lens converges to a target position. A LPF and a subtracting unit divide a shake signal into low-frequency and high-frequency components. An adding unit combines each output of a high-frequency LPF and a low-frequency LPF and output the target position. A pan/tilt determination unit determines a panning speed from the shake signal. If the panning is fast, the target positions of the low-frequency and the high-frequency are controlled to converge to 0, and calculation for the target position of the high-frequency starts before that of the low-frequency at the end determination. If the panning is slow, only the target position of the low-frequency is controlled to converge to 0. The pan/tilt determination unit changes a determination condition for the detection depending on whether it is at the handheld photographing or the static state.