Digital Clamp Controller for RAW Image Black Level Stability
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Solution Overview
Problem
Brightness-based image synthesis of RAW images in digital cameras often results in variations and misadjustments in black level due to shot noises and random noises, leading to defective images such as over-exposure or magenta-like images, which existing techniques cannot effectively address.
Innovation Solution
An imaging device with an image sensor, image processor, image synthesizer, digital clamp processor, and digital clamp controller that performs digital clamping to remove offset components from synthesized images based on the number of images synthesized, ambient conditions, and photographic settings, thereby correcting black level variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If brightness-based image synthesis is performed on RAW images, then image quality is improved by capturing minute stars and averaging random noises, but black level variation and unevenness occur leading to defective images
Solution Approach 1:
The patent applies preliminary action by performing digital clamp processing before brightness-based image synthesis. The clamp processor removes offset components from individual RAW images prior to synthesis, preventing black level variation from accumulating during the synthesis process. This preliminary correction ensures that the synthesis operation can proceed without generating defective images with black level unevenness.
Solution Approach 2:
The patent introduces an intermediary element - the clamp processor - that acts as a mediator between the RAW images and the brightness-based synthesis process. This intermediary component removes offset components and stabilizes black levels, allowing the synthesis process to achieve high image quality without suffering from black level variation. The clamp processor serves as a buffer that isolates the synthesis process from the harmful offset variations.
2Loss of information
If continuous images are synthesized using RAW data, then minute stars can be captured in colors, but shot noises and random noises cause output values to approach maximal distribution value, resulting in over-exposure or magenta-like images
Solution Approach 1:
The patent converts the harmful effect of noise into a beneficial outcome by using the clamp processor to identify and remove offset components caused by shot noise and random noise. Instead of allowing these noise-induced offset variations to corrupt the synthesized image, the clamp processor extracts and eliminates them, thereby converting the harmful noise effect into an opportunity to produce cleaner, more accurate star color information in the synthesized image.
3Reliability
If digital clamp is applied to RAW images, then black level variation can be reduced, but existing clamp techniques cannot address black level misadjustment caused by brightness-based image synthesis
Solution Approach 1:
The patent applies dynamics by making the clamp processing adaptive to brightness-based image synthesis conditions. The clamp processor dynamically adjusts its operation based on the specific characteristics of the RAW images and the synthesis process, rather than applying a fixed clamp value. This dynamic adaptation allows the clamp processor to effectively address black level misadjustment that occurs specifically during brightness-based synthesis, while maintaining black level stability across different imaging conditions.
Data Source
AI summary
An imaging device includes an image sensor to convert an optical image of a subject into an electric signal, an image processor to generate an image according to the electric signal, an image synthesizer to synthesize, pixel-by-pixel, images generated by the image processor in a same composition under a same condition, a digital clamp processor to perform a digital clamp to remove an offset component from a synthesized image obtained by the image synthesizer, and a digital clamp controller to control a digital clamp amount of the digital clamp processor on the basis of a number of images synthesized by the image synthesizer.