Low-Power HDR Image Processing with Multi-Exposure Blending
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Solution Overview
Problem
Existing low power High Dynamic Range (HDR) image processing techniques in digital cameras compromise image quality by reducing resolution, leading to loss of detail in bright areas and increased power consumption.
Innovation Solution
Implement a multi-context processing approach in the Image Signal Processor (ISP) that combines information from multiple exposures per image line, using masks and exposure range correction to selectively process and reduce data based on image content, preserving important details while minimizing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the resolution of the captured image is reduced to save processing power or memory, then power consumption is reduced, but image quality deteriorates with loss of detail in bright areas
Solution Approach 1:
The image is divided into multiple exposure images (first exposure image and second exposure image), and different regions are selectively processed based on their brightness characteristics. The processing pipeline is segmented into multiple stages (inline ISP, offline ISP) with different processing intensities applied to different regions.
Solution Approach 2:
Different processing strategies are applied to different regions of the image based on local characteristics. Bright regions (highlights) are processed using the short exposure image to preserve detail, while dark regions are processed using the long exposure image to capture sufficient signal. This local quality approach ensures optimal image quality in each region while reducing overall processing requirements.
2Loss of information
If multiple entire images from short and long exposures are processed separately, then complete image data is processed, but processing time and computational resources increase
Solution Approach 1:
The patent extracts only the necessary image data for HDR processing by generating a delta image that contains only the difference information between short and long exposure images. This extraction approach eliminates redundant data processing while preserving the essential information needed for high-quality HDR reconstruction.
Solution Approach 2:
Instead of processing complete high-resolution images, the patent processes a downsampled version of the short exposure image to generate the delta image. This partial processing approach reduces computational load significantly while still capturing the essential highlight information needed for HDR synthesis.
3Quantity of substance
If the resolution of the short exposure image is reduced, then data rate is reduced, but detail in bright areas is lost
Solution Approach 1:
The patent combines information from multiple sources (long exposure image, downsampled short exposure image, and delta image) to create a composite HDR image. This composite approach allows the system to use lower data rates for processing while reconstructing high-quality detail in the final image by synthesizing information from all input sources.
Data Source
AI summary
A computing device for image processing includes: a memory; and one or more processors implemented in circuitry, coupled to the memory, and configured to: while operating in a low power high dynamic range (HDR) mode: receive a first image having a first exposure time and a second image having a second exposure time; generate at least one reduced image from the first image or the second image; and generate an HDR image by selectively combining information from at least two of the first image, the second image, and the reduced image.