Gamma-Correction Circuit Noise Suppression via Threshold Handling
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Solution Overview
Problem
Existing gamma-correction methods in graphic display devices increase noise in darker portions of graphic signals, leading to poor signal-to-noise ratio, as they restrict gamma-correction to prevent excessive noise, which is not an effective solution.
Innovation Solution
A gamma-correction circuit comprising a high-pass filter, multiplier, subtractor, gamma-correction section, threshold handling section, and adder, where the multiplication coefficient K is adjusted based on brightness and gamma characteristic curve slope to suppress noise, with K approaching 1 for lower brightness and 0 for higher brightness, and set to 1 for slopes greater than 1 to minimize noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If gamma-correction is applied to increase contrast in darker portions, then the contrast of darker portion is improved, but noise in darker portion increases significantly
Solution Approach 1:
The patent applies different K values (K1 for darker portions, K2 for brighter portions) to different brightness regions of the graphic signal. This local differentiation allows the system to enhance contrast in darker areas while suppressing noise amplification, as the thresholding operation selectively processes only significant signal components above a certain amplitude threshold.
Solution Approach 2:
The patent changes the parameter K (multiplication factor) based on the brightness level of the signal. By setting K=1 for signal levels in range A (darker portions) and K=0 for signal levels outside this range, the system dynamically adjusts the gamma-correction strength to prevent noise amplification while maintaining contrast enhancement where needed.
2Illumination intensity
If the slope of gamma-correction characteristic curve is increased for darker portions, then contrast is improved, but noise component increases causing greater noise
Solution Approach 1:
The patent performs preliminary thresholding on the high-pass filtered signal before applying gamma-correction. By removing small-amplitude noise components beforehand (keeping only signals exceeding the threshold), the subsequent gamma-correction with increased slope does not amplify these noise components, thus preventing noise generation while maintaining contrast enhancement capability.
Solution Approach 2:
The patent converts the potentially harmful effect of high-pass filtering (which amplifies noise) into a benefit by combining it with thresholding. The high-pass filter extracts detail information, and the threshold selectively preserves only significant components, transforming noise amplification into selective detail enhancement.
3Object-affected harmful factors
If gamma-correction is restricted to prevent excessive noise, then noise is reduced, but the effectiveness of gamma-correction is compromised
Solution Approach 1:
The patent makes the gamma-correction parameter K dynamic rather than fixed. By adjusting K based on signal level (K1 for darker portions, K2 for brighter portions) and applying threshold-based selective processing, the system adapts the correction strength to local signal characteristics, maintaining effectiveness in enhancing contrast where needed while suppressing noise where appropriate.
Data Source
AI summary
The present invention provides a gamma-correction circuit, which is capable to decrease the noise in graphic signal or make the noise not clearly sensible while carrying out gamma-correction on the graphic signals. In the circuit, a high-pass filter is used to decrease the noise in a graphic signal, a gamma-correction section is used for carrying out gamma-correction on the noise suppressed graphic signal, meanwhile a threshold handling section is used for threshold treatment on the high frequency component of the graphic signal to decrease noise, and then the output of the threshold handling section is combined with the gamma-corrected graphic signal through an adder.