Camera Lens Focus Control via Coordinate Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional auto-focus methods in camera modules, such as contrast AF, phase difference AF, and DFD, face challenges with focusing speed and accuracy due to viewing angle variations caused by lens movement, leading to coordinate deviations and errors in focus position calculation.
Innovation Solution
The solution involves correcting coordinate deviations by determining a second partial area based on a first partial area and adjusting the focus position using specified point spread functions, while also accounting for viewing angle variations and brightness differences between images, to improve the accuracy of depth from defocus calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the DFD AF method is used to calculate focus position, then the focusing speed is improved, but coordinate deviations occur due to viewing angle variations caused by lens movement
Solution Approach 1:
The patent changes the parameter of image coordinate systems by introducing a corrected coordinate system that compensates for lens movement-induced viewing angle variations. The processor transforms coordinates from the original image coordinate system to a corrected coordinate system that accounts for the lens position, thereby eliminating measurement errors while maintaining the speed benefits of the DFD method.
2Speed
If the phase difference AF method is used to detect focus position, then the focusing speed is improved, but the camera module size increases due to requiring a mirror
Solution Approach 1:
The patent replaces the mechanical mirror-based phase difference detection system with a computational approach using the existing image sensor. Instead of using a physical mirror to create phase differences, the system uses software-based DFD calculation on images from the single image sensor, thereby achieving fast focusing without increasing camera module size.
3Volume of moving object
If the phase difference AF method of mirrorless camera is used, then the camera module size is reduced, but image quality deteriorates or cost increases
Solution Approach 1:
The patent makes the image sensor serve multiple functions: it acts as both the primary imaging sensor for capturing high-quality images and as the detection sensor for phase difference-based focus detection. By using the same image sensor for both purposes and applying coordinate correction algorithms, the system achieves both compact size and maintained image quality without requiring specialized phase difference pixels or additional sensors.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An electronic device includes a camera and a processor. The processor is configured to: obtain a first image from the camera with respect to an external object, move a lens device depending on a specified amount of movement using a lens driver, obtain a second image corresponding to a position to which the lens device moves with respect to the external object, determine a first partial area of the first image corresponding to a specified portion of the external object, determine a second partial area of the second image corresponding to the first partial area based on the first partial area and the specified movement amount, determine a focus position with respect to the lens device based on a defocus difference between the first partial area and the second partial area and the specified movement amount, and move the lens device to the focus position using the lens driver.