Image Frame Gain Control via Front Row Luminance Averaging
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Solution Overview
Problem
Existing methods for determining the gain of an image frame in optical devices, such as cameras and LCD TVs, are inefficient and not real-time, as they require a test image frame or light-metering area and do not consider the luminance sensitivity of human eyes, leading to inappropriate gain settings in bright or dark environments, and are affected by fixed pattern noise (FPN).
Innovation Solution
A method using dummy rows of an image frame to scan and average image data, generating a corresponding gain based on the luminance sensitivity of human eyes through a look-up table, which adjusts the main image frame's information to optimize image quality by controlling the Programmable Gain Amplifier (PGA), thereby reducing FPN and enhancing color contrast and luminance sensitivity according to environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a test image frame or light-metering area is used to determine gain, then the gain can be determined, but the method is not real-time and requires additional areas or frames
Solution Approach 1:
The patent makes the entire image frame serve dual purposes: both as the main image content and as the light-metering area for gain determination. By scanning multiple front rows of the image frame to calculate average luminance, the system eliminates the need for dedicated test frames or light-metering areas, achieving real-time gain adjustment without sacrificing image processing efficiency
Solution Approach 2:
The image frame itself provides the information needed for gain determination through its own pixel data. The system scans the front rows of the image frame to compute average luminance, allowing the image to self-determine its own display parameters without requiring external reference signals or additional measurement infrastructure
2Productivity
If conventional look up table is used for gain, then the gain can be determined quickly, but it doesn't consider human luminance sensitivity and provides inappropriate gain in extreme environments
Solution Approach 1:
The patent transforms the conventional linear look up table into a non-linear one that incorporates human luminance sensitivity characteristics. By weighting different luminance ranges according to human visual sensitivity (higher weight for low luminance regions where human eyes are more sensitive), the system maintains fast gain determination through table lookup while achieving accurate, vision-optimized gain values for extreme bright and dark environments
3Ease of manufacture
If FPN is present in CMOS sensors, then the sensor can capture images, but fixed pattern noise degrades image quality with column and row brightness differences
Solution Approach 1:
The patent applies different gain values to different regions of the image frame based on local luminance characteristics and human visual sensitivity. By scanning front rows and calculating average luminance, then applying weighted gain adjustment, the system compensates for FPN-induced brightness variations in columns and rows, improving local image uniformity while preserving overall image quality
Data Source
AI summary
A method of generating a gain of an image frame according to a look up table of gain which is set up based on luminance sensitivity of human eyes is proposed. The method includes setting a gain of an image frame to 1, scanning images of a plurality of front rows of the image frame, averaging the images of the plurality of the front rows of the image frame to generate an average value of the images of the plurality of the front rows of the image frame, finding a gain from the look up table of gain according to the average value of the images of the plurality of the front rows of the image frame, and adjusting remaining rows of the image frame according to the gain to generate images of the remaining rows of the image frame.