Camera Autofocus Calibration via Automatic Conversion Coefficient Adjustment
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Solution Overview
Problem
Existing camera systems face challenges in accurately estimating the defocus amount due to vignetting caused by manufacturing errors or play in the optical system, leading to incorrect autofocus operations, especially when calibration is not properly performed by the operator before photographing.
Innovation Solution
The camera automatically calibrates the conversion coefficient that converts a blur amount to a defocus amount during normal operation, without requiring the operator to be aware of the calibration process, by compensating for vignetting effects and updating the conversion coefficient based on focal point position movements during focusing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration operation is performed before photographing to correct conversion coefficient, then defocus amount estimation accuracy is improved, but operational burden on user increases and calibration may not be performed correctly
Solution Approach 1:
The camera system performs automatic calibration of the conversion coefficient without requiring user intervention. The calibration is executed automatically during normal operation by capturing images at different focus positions and computing the conversion coefficient from the relationship between blur amount and actual focus position, thereby eliminating the need for manual calibration operations while maintaining measurement precision.
Solution Approach 2:
The calibration process is performed automatically in advance during normal camera operation before actual photographing. The system captures calibration images, computes the conversion coefficient, and stores it for subsequent use, ensuring accurate defocus amount estimation is prepared beforehand without requiring the user to perform manual calibration steps.
2Measurement precision
If calibration operation is required before photographing, then conversion coefficient accuracy is improved, but time consumption increases
Solution Approach 1:
The camera system performs calibration automatically without requiring the user to allocate time for manual calibration operations. The system self-manages the calibration process by capturing images, computing the conversion coefficient, and storing it automatically, thereby eliminating time loss while maintaining coefficient accuracy.
Solution Approach 2:
The calibration process is integrated into normal camera operation and can be performed continuously or periodically without interrupting the workflow. The system maintains the conversion coefficient through continuous calibration during use, ensuring accuracy is updated without requiring separate calibration sessions that would consume additional time.
3Ease of operation
If automatic calibration is performed during normal operation, then user convenience is improved, but system complexity increases
Solution Approach 1:
The camera system performs calibration automatically during normal operation without requiring user intervention, thereby improving convenience. The system self-manages the entire calibration process including image capture, coordinate extraction, blur amount calculation, and conversion coefficient computation, hiding the complexity from the user while maintaining simplicity of operation.
Solution Approach 2:
The image capturing unit serves multiple functions: it captures both calibration images and normal photographing images using the same hardware and processing pipeline. The focus detecting unit also performs dual functions by detecting focus position during both calibration and normal operation, thereby reducing overall system complexity by reusing existing components for multiple purposes.
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
This approach improves autofocus speed and precision by ensuring accurate defocus amount estimation and reduces the operational burden on the user, enhancing the overall usability and convenience of the camera system.
Implementation Method 1
phase difference detection unit that detects a focusing state of the image-taking lens by phase difference detection using a pair of image signals obtained by a pupil division unit
Implementation Method 2
pupil division unit that divides a pupil area of the image-taking lens into a plurality of areas, and obtains a pair of image signals from the divided pupil areas
Implementation Method 3
image sensor that includes imaging pixels for capturing an image formed via an imaging optical system
Data Source
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AI summary
A focal point adjusting apparatus comprises: a photoelectric converting unit that photoelectrically converts at least a pair of optical images and outputs at least a pair of image signals; a phase difference detecting unit that detects the phase difference between the pair of image signals that is output by the photoelectric conversion unit; a conversion unit that carries out the conversion of a phase difference that is detected by the phase difference detecting unit into a defocus amount by using a conversion coefficient; a focal point moving unit that moves the focal point position based on the defocus amount resulting of the conversion by the conversion unit; and a calibrating unit that calibrates the conversion coefficient depending on the result of the focal point moving unit moving the focal point position when the operator photographs a subject.