Digital Camera Auto-Focusing in Low Light
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Solution Overview
Problem
Conventional imaging devices, such as digital cameras, face challenges in accurately detecting object distance in low-light environments using phase difference detection methods, leading to incorrect focusing.
Innovation Solution
The implementation of a digital camera system that includes a portrait photography mode setting, display of an object display frame, acquisition of focusing position information, and adjustment of the focus lens based on this information, allowing for accurate focusing even in low-light conditions by correcting distance information according to zoom magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If phase difference detection method is used for auto-focusing, then focusing speed and automation are improved, but accuracy deteriorates in low-light conditions
Solution Approach 1:
The patent changes the detection parameter from phase difference (which requires sufficient light) to face detection based on facial recognition technology. By detecting the position and size of faces in the image and using pre-stored correspondence tables between face characteristics and distance information, the system achieves accurate distance measurement in low-light conditions where phase difference detection fails.
2Productivity
If conventional face detection method is used, then processing speed is improved, but accuracy deteriorates due to lack of distance information correction
Solution Approach 1:
The patent introduces feedback by using pre-stored correspondence tables that map face detection results (position, size) to accurate distance information. The system continuously refines distance measurement by comparing detected face characteristics with stored reference data, correcting for zoom magnification effects and achieving high-precision distance measurement while maintaining fast processing speeds.
Data Source
AI summary
FIGS. 2A˜2D are object display frames corresponding to respective portrait photography modes and distance information corresponding to respective portrait photography modes is stored in a distance information table of memory (Refer to FIG. 2E). When the user selects a portrait photography mode, an object display frame corresponding to the portrait photography mode is displayed on an image display section. The user can adjust the object to be photographed in this object display frame while observing the object display frame (Refer to FIG. 2F). Then, when the shutter button is depressed, the distance information corresponding to this selected portrait photography mode is read from the distance information table and the focus lens is driven based on the readout distance information.