Optical Filter Equalizes Red Green Signals for Noise Reduction
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Solution Overview
Problem
Conventional color photographing devices experience increased noise and discontinuity of gradation, particularly at dark image portions, due to high white balance gains applied during photography, which affects the reproduction of white highlights and overall image quality.
Innovation Solution
A color photographing device equipped with an optical filter and a light-receiving section that equalizes signal levels of red, green, and blue pixel signals, and includes a white balance adjusting section that estimates color temperature and adjusts exposure to maintain white balance gains equal to or greater than 1, while reducing exposure to compensate for signal level discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high white balance gains are applied to equalize signal levels of R, G, and B, then white balance accuracy is improved, but noise increases and gradation continuity deteriorates
Solution Approach 1:
The patent applies preliminary action by adjusting the spectral sensitivity of the image sensor before photography through an optical filter. The filter modifies the sensitivity characteristics so that red and blue pixels have higher sensitivity, reducing the need for high white balance gains during actual photography. This pre-adjustment prevents noise amplification while maintaining accurate white balance.
Solution Approach 2:
The patent changes the physical parameters of the image sensor system by introducing an optical filter that modifies the spectral sensitivity characteristics. Specifically, it adjusts the sensitivity ratios of red, green, and blue pixels to achieve a more balanced signal distribution, thereby reducing the white balance gains needed and consequently reducing noise in the captured image.
2Measurement precision
If high white balance gains are applied, then white balance accuracy is improved, but image quality deteriorates due to discontinuity of gradation
Solution Approach 1:
The optical filter performs preliminary adjustment of the spectral sensitivity before light reaches the sensor, ensuring that the raw signals from red and blue pixels are already closer to the green pixel signals. This pre-balancing prevents the need for aggressive digital gain application that would otherwise cause gradation discontinuity and loss of image quality.
Solution Approach 2:
By changing the spectral sensitivity parameters through the optical filter, the patent achieves a more uniform signal distribution across color channels. This parameter adjustment ensures smooth gradation transitions in the final image while maintaining accurate white balance, avoiding the banding and discontinuity that occur with high digital gains.
3Object-generated harmful factors
If spectral sensitivity is adjusted to equalize signal levels, then white balance gains are reduced, but device complexity increases
Solution Approach 1:
The patent introduces an optical filter as an intermediary component between the light source and the image sensor. This mediator adjusts the spectral composition of light before it reaches the sensor, equalizing the signal levels across color channels and reducing the need for post-processing gain adjustment, thereby reducing noise without requiring complex digital processing.
Solution Approach 2:
The patent replaces complex digital signal processing mechanisms with a simpler optical mechanism. Instead of relying on sophisticated algorithms and high computational power to correct white balance and reduce noise, the solution uses a passive optical filter to pre-adjust the light spectrum, achieving the same effect with minimal added complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces noise and enhances gradation by maintaining white balance gains equal to or greater than 1 across a broader range of color temperatures, preventing highlight coloration and ensuring proper exposure, thereby improving image quality and noise reduction.
Implementation Method 1
an optical filter disposed on the side with a light-receiving surface of the light-receiving section
Data Source
AI summary
A color photographing device is equipped with a light-receiving section having a red pixel selectively receiving red light and outputting a red pixel signal and a green pixel selectively receiving green light and outputting a green pixel signal. The color photographing device is further equipped with an optical filter disposed on the side with a light-receiving surface of the light-receiving section. The optical filter substantially equalizes the signal level of the red pixel signal and the signal level of the green pixel signal when achromatic color illuminated by a solar light source in the daytime is photographed. Therefore, a white balance gain Wr at about 5000K can be lowered as compared with a conventional color photographing device. Accordingly, reduction of color noises and enhancement of gradation can be expected.