Autofocus Composite Image Signal Generation for Brightness Saturation
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Solution Overview
Problem
Existing autofocus methods, such as the contrast AF method, face focus point errors due to brightness saturation areas caused by light sources, which are not effectively addressed in digital photographing devices.
Innovation Solution
An autofocus adjusting method and apparatus that generates a first image signal during a first exposure time and a second image signal during a shorter exposure time, combining them to create a composite image signal, which calculates a focus detection evaluation value, and replaces brightness saturation areas in the first image signal with corresponding areas from the second image signal to improve focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a long exposure time is used to capture sufficient light, then image brightness is improved, but brightness saturation areas are caused by light sources leading to focus point errors
Solution Approach 1:
The patent divides the image signal processing into multiple segments by capturing images at different exposure times. The first image signal is captured at a longer exposure time for sufficient brightness, while the second image signal is captured at a shorter exposure time to avoid saturation. These segmented signals are then processed separately and combined, allowing the system to benefit from both long and short exposure times without the harmful effects of either extreme.
Solution Approach 2:
The patent changes the exposure time parameter by capturing multiple images at different exposure durations. The system uses at least two different exposure times (first exposure time and second exposure time) to capture the same scene, creating image signals with different brightness characteristics. This parameter change allows the system to overcome the limitation of single-exposure contrast AF methods by providing both saturated and non-saturated pixel data for accurate focus detection.
2Measurement precision
If multiple images with different exposure times are captured and processed, then focus detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple image signals captured at different exposure times into a single composite image signal. The first image signal (long exposure) and second image signal (short exposure) are combined through a merging process that weights their contributions, creating a unified signal that maintains both brightness information and non-saturated pixel data. This merging approach simplifies the overall process by consolidating multiple capture operations into a single integrated signal for focus detection.
Solution Approach 2:
The patent introduces a composite image signal as an intermediary that mediates between the first and second image signals. This intermediary signal serves as the basis for focus detection evaluation, combining the advantages of both original signals while filtering out their respective disadvantages. The composite signal acts as a mediator that translates the raw, potentially problematic data from single-exposure methods into a refined signal suitable for accurate autofocus processing.
Data Source
AI summary
Provided are an autofocus (AF) adjusting method and apparatus. The AF adjusting method for an AF adjusting apparatus includes: generating a first image signal by photographing an area (or object) during a first exposure time; generating a second image signal by photographing the area during a second exposure time shorter than the first exposure time; generating a composite image signal by combining the first and second image signals; and calculating a focus detection evaluation value from the composite image signal.