Spatio-Temporal Differential Synthesis for High Dynamic Range Imaging
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Solution Overview
Problem
Capturing images through semi-transparent, semi-reflective, semi-absorptive materials like tinted windows poses a challenge due to the intermixing of light from the subject with reflected light and glare, making it difficult to discern the subject of interest, especially when it contributes only a small portion of the light at each pixel.
Innovation Solution
A novel approach combining image subtraction, spatio-temporal filtering, high-dynamic-range tonal mapping, and image compositing to selectively enhance subject light relative to background light, using asymmetric temporal differencing and illumination modulation to distinguish reflection background from true background and subject light, and adjusting image acquisition parameters based on enhanced subject images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional tone-mapping techniques are applied to enhance subject visibility, then brightness and contrast are improved, but reflected light and glare are also amplified making the subject unrecognizable
Solution Approach 1:
The patent segments the complex light mixture into distinct components: subject light, reflected light, and glare. By separating these components through spatio-temporal filtering and frequency analysis, the system can selectively enhance subject light while suppressing reflected light and glare, resolving the contradiction between brightness enhancement and reflected light interference.
Solution Approach 2:
The patent applies different processing qualities to different spatial and temporal regions of the image. Subject regions receive enhancement processing while reflected light regions receive suppression processing. This local differentiation allows brightness improvement in subject areas without amplifying harmful reflections elsewhere in the image.
2Measurement precision
If multiple exposures are combined using traditional HDR techniques, then tonal detail in low-lit areas is improved, but detail in brightly-lit areas becomes saturated
Solution Approach 1:
The patent employs dynamic processing that adapts to local lighting conditions. The spatio-temporal filtering system dynamically adjusts gain and suppression parameters based on real-time analysis of subject versus reflected light characteristics, enabling simultaneous preservation of detail in both low-lit and brightly-lit areas without saturation.
Solution Approach 2:
The patent changes processing parameters selectively across different regions and time points. By varying the enhancement and suppression parameters based on spatio-temporal analysis, the system maintains optimal tonal detail across the full dynamic range while preventing saturation in brightly-lit regions.
3Loss of information
If image subtraction and spatio-temporal filtering are applied to isolate subject light, then subject visibility is enhanced, but processing complexity increases
Solution Approach 1:
The patent utilizes periodic sampling of multiple frames at different time points to capture subject light characteristics. By performing image subtraction across these periodically captured frames, the system isolates subject light while suppressing stationary reflected light, achieving enhanced visibility through a structured periodic process rather than continuous complex processing.
Solution Approach 2:
The patent creates synthetic copies of the image at different time points and uses these copies for subtraction operations. By working with copied frames rather than directly processing the original continuous stream, the system simplifies the isolation of subject light while maintaining processing efficiency.
4Ease of operation
If automatic camera parameter selection algorithms are used, then exposure and focus are optimized for visible features, but hidden subjects are ignored
Solution Approach 1:
The patent implements feedback by analyzing temporal changes in image sequences to identify subjects that are initially hidden. The system uses this feedback to adjust camera parameters such as exposure and focus to optimize capture of the previously hidden subject, thereby improving subject detection while maintaining ease of automatic operation.
Solution Approach 2:
The patent performs preliminary analysis of image sequences to detect hidden subjects before final parameter selection. By identifying subjects that contribute minimal light in initial frames, the system can pre-adjust camera parameters to ensure these subjects are properly captured in subsequent frames, preventing information loss before the main capture occurs.
Data Source
AI summary
An image acquisition apparatus configured to receive an adjustable image acquisition parameter, wherein said parameter is adjusted based on an image that has had its subject selectively enhanced via comparison with at least one background reference image.