Low Light Image Capture Using Multi-Frame Alignment and Brightness Adjustment
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Solution Overview
Problem
Image capture devices, such as cell phone cameras, face challenges in capturing high-quality images in low-light conditions due to difficulties in balancing exposure time, which can result in blurred or noisy images, and existing de-blurring methods are computationally expensive and may introduce artifacts.
Innovation Solution
A method involving capturing multiple short-exposure images, aligning them using affine fit processing, converting to YUV format, denoising the luma channel with L1-norm Total Variation, and using a long-exposure image to adjust brightness through histogram matching, eliminating the need for camera motion estimation and deconvolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a long exposure time is used to capture images in low-light conditions, then the brightness of the image is improved, but the image becomes blurred due to camera motion
Solution Approach 1:
The patent segments the long exposure capture into multiple short exposure frames captured in rapid succession. Each frame is processed separately to remove motion blur, then the frames are combined through alignment and averaging to produce a final image that is both bright and sharp, resolving the contradiction between long exposure brightness and short exposure sharpness
Solution Approach 2:
The patent performs preliminary alignment and combination of multiple short-exposure frames before final processing. By pre-aligning the frames based on detected features and combining them to reduce noise, the system prepares the image data in advance, allowing the final long-exposure-equivalent image to achieve both brightness and sharpness without motion blur
2Manufacturing precision
If a short exposure time is used to reduce blurriness, then the image sharpness is improved, but the image becomes dark and noisy
Solution Approach 1:
The patent merges multiple short-exposure frames by aligning them and averaging their pixel values. This combination process effectively increases the signal-to-noise ratio and total light capture, producing an image that maintains the sharpness of individual short-exposure frames while achieving the brightness equivalent of a long exposure
Solution Approach 2:
The patent captures multiple copies of the scene in rapid succession with short exposure times. These copies are then processed and combined to create a final image that inherits the sharpness of the individual copies while accumulating enough light signal to achieve proper brightness, avoiding the noise and darkness of single short-exposure images
3Illumination intensity
If ISO is increased to brighten a short-exposure image, then the image brightness is improved, but the image becomes noisy
Solution Approach 1:
Instead of using a single short exposure with high ISO amplification (excessive action on one frame), the patent uses multiple short exposures with normal or low ISO settings. The combination of these multiple frames provides sufficient brightness through accumulated signal while maintaining image quality, avoiding the noise introduced by high ISO amplification
4Illumination intensity
If flash is used to brighten a short-exposure image, then the image brightness is improved, but the color accuracy decreases due to artificial color offsets
Solution Approach 1:
The patent uses multiple short-exposure frames as an intermediary approach between natural low-light capture and artificial flash illumination. By combining multiple frames captured with ambient light only, the system achieves sufficient brightness without introducing the color casts and artifacts associated with flash, maintaining both brightness and color accuracy
Data Source
AI summary
Methods, devices, and computer program products for capturing images with reduced blurriness in low light conditions are contained herein. In one aspect, a method of capturing an image is disclosed. The method includes capturing a plurality of first images with a first exposure length. The method further includes aligning each of the plurality of first images with each other and combining the aligned plurality of first images into a combined first image. The method further includes capturing a second image with a second exposure length, wherein the second exposure length is longer than the first exposure length and using the second image to adjust the brightness of the combined first image.