Imaging Focus and Tilt Control via Phase Difference Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing focus control methods using contrast AF are slow and deteriorate image quality due to unnecessary operations, and phase difference AF with a tilted image sensor can cause hunting, making high-speed and accurate focus control difficult.
Innovation Solution
A control apparatus and method that utilize phase difference detection to calculate the tilt angle and focus position using an image sensor with a CMOS sensor, performing focus detection by imaging-plane phase difference detection without a dedicated AF sensor, and adjusting the tilt and focus positions based on calculated defocus amounts and conversion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference detection is used with a tilted image sensor, then focus detection speed is improved, but hunting occurs and measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating the tilt angle of the image sensor and using this information to correct the phase difference detection results before they are used for focus control. This prevents the hunting phenomenon from occurring in the first place, rather than trying to correct it after it occurs. The system proactively compensates for the tilt-induced errors in phase difference measurements.
Solution Approach 2:
The patent changes the parameters used in phase difference detection by introducing tilt angle compensation. Instead of using raw phase difference values directly, the system adjusts these values based on the calculated tilt angle, thereby maintaining measurement precision while preserving the speed advantages of phase difference detection with tilted sensors.
2Measurement precision
If contrast AF is used for focus control, then focus accuracy is improved, but processing time increases
Solution Approach 1:
The patent applies preliminary action by performing tilt angle calculation and compensation in advance, before the actual focus detection process. This pre-processing step ensures that subsequent phase difference detection operates with corrected parameters, achieving contrast-level accuracy without the time-consuming iterative adjustments that pure contrast AF requires.
Solution Approach 2:
The patent substitutes the mechanical iterative adjustment process of contrast AF with a calculated compensation approach. Instead of physically moving the lens and evaluating contrast at multiple positions, the system uses phase difference detection with tilt-based mathematical compensation, replacing the mechanical search process with a more efficient computational method.
3Adaptability or versatility
If the image sensor is tilted to extend depth of field, then imaging capability is improved, but phase difference detection accuracy deteriorates
Solution Approach 1:
The patent changes the detection parameters by introducing tilt angle as a correction factor. The system calculates the actual tilt angle of the image sensor and uses this parameter to adjust the phase difference measurements, thereby maintaining detection accuracy even when the sensor is tilted for extended depth of field imaging.
Solution Approach 2:
The patent introduces the tilt angle calculation as an intermediary step between the tilted sensor and phase difference detection. This intermediary computation bridges the gap between the tilted imaging configuration and the phase difference measurement system, translating the tilted geometry into corrected detection parameters.
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
Enables high-speed and highly accurate focus control even when the imaging plane is tilted, improving focus detection accuracy and image quality by directly calculating defocus amounts and adjusting the focus and tilt positions accordingly.
Implementation Method 1
a calculation unit configured to calculate an image shift amount by a phase difference detection method based on a signal from the image sensor and to calculate a defocus amount based on the image shift amount and a conversion coefficient
Data Source
Figure 1
Figure 2~3D
Figure 4
AI summary
A control apparatus (100) includes an acquisition unit (115) configured to acquire optical information, a tilt control unit (116) configured to tilt an image sensor relative to a plane orthogonal to an optical axis of an imaging optical system, and a calculation unit (112) configured to calculate an image shift amount by a phase difference detection method based on a signal from the image sensor and to calculate a defocus amount based on the image shift amount and a conversion coefficient. The calculation unit changes at least one of a correction amount of the signal and the conversion coefficient based on the optical information and a tilt angle that is an angle formed by the image sensor and the plane.