Local Tone Mapping Mask for Video Intensity Variation Reduction
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Solution Overview
Problem
Video monitoring systems face challenges in maintaining optimal exposure levels in scenes with large brightness variations, leading to underexposed or overexposed areas, especially when bright objects enter the scene.
Innovation Solution
A method and digital video camera system that captures frames with adjustable sensor settings and applies a local tone mapping mask to compensate for intensity changes, creating a gradient transition between affected and unaffected areas, thereby reducing intensity variations in the video stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the exposure time of the video camera is increased to collect more light in low light scenes, then the light levels in the video are improved, but when a bright object enters the scene, the camera must decrease exposure time to avoid overexposure, causing darker parts to become underexposed again
Solution Approach 1:
The patent divides the image into multiple regions and applies different exposure settings to each region. The image sensor is divided into a first region (where bright objects appear) and a second region (darker areas), with independent exposure time control for each region, allowing simultaneous optimization of both bright and dark areas
Solution Approach 2:
The patent implements local quality by applying different exposure parameters to different spatial regions of the image. The first region receives a first exposure time while the second region receives a second exposure time, ensuring each region has optimal exposure quality for its specific lighting conditions
2Illumination intensity
If an external light source is introduced to illuminate the scene, then the light levels are increased, but the power consumption increases and the camera location is disclosed
Solution Approach 1:
The patent replaces the mechanical/optical solution of external illumination with an electronic/image processing solution. Instead of adding physical light sources, the system uses digital image processing techniques including region-based exposure adjustment and tone mapping to achieve the desired illumination effect without additional power consumption or revealing camera position
3Manufacturing precision
If the exposure time is decreased to avoid overexposure of bright objects, then overexposure is reduced, but darker parts of the scene become underexposed
Solution Approach 1:
The patent segments the image sensor into multiple regions with independent exposure control. The first region (bright areas) uses a shorter exposure time to prevent overexposure, while the second region (dark areas) uses a longer exposure time to ensure adequate brightness, with the sensor reading values combined from both regions
Solution Approach 2:
The patent adds a spatial dimension to exposure control by implementing region-based differential exposure. Instead of a single global exposure time, the system introduces spatial variability in exposure parameters across different regions of the image, allowing simultaneous optimization of exposure for both bright and dark areas
Data Source
AI summary
A method and a digital video camera for reducing intensity variations in a video stream depicting a scene comprising capturing, using a first sensor setting, a first frame; detecting a change in intensity in a portion of the first frame, the portion represents a first area of the scene; determining a second sensor setting based on the first frame; capturing, using the second sensor setting, a second frame; creating a local tone mapping mask, wherein a local tone mapping in the first area of the scene is different from a local tone mapping in an area outside the first area, and wherein the local tone mapping in the area outside the first area is based on a relation between the first sensor setting and the second sensor setting; and applying the local tone mapping mask to the second frame.