Dual-Camera Mobile Imaging with Flash Segmentation
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Solution Overview
Problem
Handheld mobile devices struggle to capture clear images of low-light scenes with moving objects, as long exposure times required for low-light conditions often result in image blur, especially for foreground objects.
Innovation Solution
A dual-camera method where a first camera captures a short-exposure foreground image using a flash to illuminate near-field objects, while a second camera captures a long-exposure background image, and the two images are combined to produce a final composite image with reduced motion blur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a long exposure time is used to capture low-light scenes, then the background illumination is improved, but motion blur increases for moving objects
Solution Approach 1:
The patent divides the scene into near-field and far-field regions, and divides the imaging process into two separate captures: one with short exposure for near-field objects and one with long exposure for far-field background. This segmentation allows each region to be captured with optimal exposure settings, resolving the contradiction between background illumination and motion blur.
Solution Approach 2:
The patent adds a temporal dimension to the imaging process by capturing two images at different exposure times and combining them. This multi-temporal approach allows the system to overcome the limitation of single-exposure imaging, where improving one region's illumination inevitably degrades another region's sharpness.
2Manufacturing precision
If a short exposure time is used to freeze motion, then motion blur is reduced, but the background remains under-illuminated in low-light conditions
Solution Approach 1:
The patent segments the imaging task into two separate captures with different exposure settings. The first capture uses short exposure to freeze motion of near-field objects, while the second capture uses long exposure to illuminate the far-field background. This segmentation resolves the contradiction by allowing each region to be captured with its optimal exposure setting.
Solution Approach 2:
The patent introduces a temporal dimension by performing multiple captures with different exposure times and combining them. This multi-temporal imaging approach allows the system to simultaneously achieve motion freezing and background illumination, which cannot be accomplished with a single exposure setting.
3Manufacturing precision
If optical image stabilization is used to correct hand tremble, then stationary scene quality is improved, but moving objects still appear blurred due to long exposure time
Solution Approach 1:
The patent segments the scene into near-field and far-field regions and applies different exposure strategies to each. By capturing near-field objects with short exposure time, the system freezes motion effectively without relying on optical image stabilization, while far-field background is captured with long exposure where stabilization is more effective.
Solution Approach 2:
The patent dynamically adjusts exposure time based on the spatial position and motion characteristics of different scene regions. Near-field moving objects are captured with short exposure to freeze motion, while far-field stationary background is captured with long exposure to maximize illumination, creating a dynamic, adaptive imaging approach.
4Manufacturing precision
If slow sync flash technique is used to reduce motion blur, then moving object sharpness is improved, but synchronization with camera blanking time becomes difficult
Solution Approach 1:
The patent segments the imaging process into two independent captures with different flash synchronization strategies. The first capture uses flash synchronized with the first camera's blanking time for near-field objects, while the second capture may use different synchronization for far-field background, simplifying the overall synchronization problem by dividing it into manageable segments.
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 enables precise imaging of low-light scenes with optimally illuminated and focused foreground and background elements, effectively reducing motion blur and improving image quality.
Implementation Method 1
actuating a flash unit of the camera arrangement to obtain a first image
Data Source
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AI summary
The invention describes a method of operating a camera arrangement (1) of a mobile device (2), comprising the steps of operating a first camera (C1) of the camera arrangement (1) using a short exposure duration (Dshort) and simultaneously actuating a flash unit (12) of the camera arrangement (1) to obtain a first image (11); operating a second camera (C2) of the camera arrangement (1) using a long exposure duration (Dlong) to obtain a second image (12); processing the first image (11) to extract foreground image data (5); processing the second image (12) to obtain background image data (4); and overlaying the foreground image data (4) onto the background image data (5) to obtain a final image (6). The invention further describes a camera control arrangement (1) configured to perform the steps of the inventive method, and a camera arrangement (1) comprising such a camera control arrangement (1).