Image Capture Dynamic Range Control via Dual Exposure
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Solution Overview
Problem
Image capturing apparatuses with insufficient dynamic range struggle to capture scenes with strong contrast, leading to overexposure in bright areas and underexposure in dark areas, especially when exposure control is user-set and not adjusted for background luminance levels.
Innovation Solution
An image capturing apparatus generates both long-exposure and short-exposure image signals, combines them to create a wider dynamic range image signal, and uses a detection unit to analyze luminance information and adjust the short-exposure period to prevent overexposure, allowing for automatic exposure control in user-set modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exposure control is performed according to user setting for main subject, then main subject exposure is maintained, but background overexposure occurs due to saturation
Solution Approach 1:
The patent divides the image into multiple regions (main subject area and background area) and performs separate exposure control for each region. The control unit calculates exposure amounts for both regions and adjusts the exposure period to prevent overexposure in the background while maintaining proper exposure of the main subject.
Solution Approach 2:
The patent implements a feedback mechanism where the control unit continuously monitors the exposure amount in the background region and adjusts the exposure period accordingly. When the background exposure amount exceeds a predetermined threshold, the exposure period is reduced to prevent overexposure, while maintaining the main subject exposure through gain adjustment.
2Device complexity
If single exposure period is used, then device complexity is reduced, but dynamic range is insufficient for high contrast scenes
Solution Approach 1:
The patent dynamically adjusts the exposure period based on the luminance characteristics of different regions in the scene. The control unit calculates the exposure amount for both the main subject and background regions, and modifies the exposure period in real-time to optimize the dynamic range for high contrast scenes while preventing overexposure.
3Measurement precision
If long exposure period is used, then dark area detail is improved, but bright area overexposure occurs due to saturation
Solution Approach 1:
The patent applies different exposure strategies to different regions of the image. The long exposure period is used specifically for the main subject area to capture dark area details, while the background region exposure is controlled separately to prevent overexposure in bright areas.
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 image quality by preventing overexposure in non-main subject areas, ensuring a balanced exposure across varying luminance levels, even in scenes with significant contrast differences.
Implementation Method 1
an image pickup device unit (2) performs long exposure and short exposure in a unit period
Data Source
AI summary
An image capturing apparatus includes: an image capturing unit configured to generate a long-exposure image signal and a short-exposure image signal on the basis of light transmitted from a subject and output the long-exposure image signal and the short-exposure image signal as image capturing signals; a signal processing unit configured to generate a combined image signal by combining the long-exposure image signal and the short-exposure image signal, the combined image signal having a dynamic range that is relatively wider than that of at least any one of the long-exposure image signal and the short-exposure image signal; a detection unit configured to generate luminance information of the combined image signal; and a control unit configured to perform automatic exposure control for the short-exposure image signal using the luminance information in an exposure setting mode in which exposure control is performed in accordance with a user's setting.