Projector Gradation Correction for Outside Light Adaptation
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Solution Overview
Problem
Conventional image display devices, such as projectors, face challenges in maintaining optimal viewability due to external light influences like room lighting and sunlight, as they primarily focus on video luminance signal characteristics without considering environmental changes.
Innovation Solution
An image display device equipped with an outside light detector and a luminance level adjusting circuit that performs gradation correction by distributing luminance values in a smaller range according to outside light intensity, while avoiding excessive contrast changes and preserving skin color tones, using correction coefficients calculated based on luminance distributions and average luminance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gradation correction is performed based only on video luminance signal characteristics, then image contrast is improved, but viewability deteriorates under outside light conditions
Solution Approach 1:
The system uses an outside light detector to measure the actual outside light intensity and feeds this information back to the luminance level adjusting circuit. This feedback mechanism allows the gradation correction to adapt dynamically to changing outside light conditions, resolving the contradiction between maintaining image contrast and ensuring viewability under various lighting environments.
Solution Approach 2:
The patent transforms the static gradation correction approach into a dynamic one by continuously adjusting the luminance values based on real-time outside light intensity measurements. The luminance level adjusting circuit dynamically modifies the correction coefficients according to the detected outside light conditions, enabling the system to adapt to varying environmental lighting rather than using fixed correction parameters.
2Illumination intensity
If luminance values are distributed in a smaller luminance value range to increase luminance, then visibility under outside light is improved, but contrast deteriorates
Solution Approach 1:
The system changes the luminance distribution parameters dynamically based on outside light intensity. When outside light is strong, the luminance values are compressed into a smaller range to increase overall brightness and visibility. When outside light is weak, the luminance range is expanded to preserve contrast. This parameter adjustment resolves the contradiction between visibility and contrast by adapting to different lighting conditions.
3Illumination intensity
If gradation correction is applied uniformly to all pixels, then overall visibility is improved, but skin color tones become unnatural
Solution Approach 1:
The patent applies different gradation correction strategies to different regions of the image based on local characteristics. Skin color pixels are identified and subjected to different correction parameters compared to non-skin pixels. This local differentiation allows the system to improve overall visibility through gradation correction while preserving the natural appearance of skin tones, resolving the contradiction between visibility enhancement and color accuracy.
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
This solution enhances visibility by adjusting luminance levels in response to external light conditions, reducing contrast deterioration and ensuring a natural image display with improved viewability across varying environments.
Implementation Method 1
an outside light detector 304 operable to measure an outside light intensity
Data Source
AI summary
A projector 1 detects a luminance distribution in an effective video period of an inputted video luminance signal, and a coefficient calculating circuit 302 calculates a correction coefficient Ci to correct a gradation (FIG. 6A). Then, surrounding brightness is detected, and the correction coefficient Ci is adjusted based on the surrounding brightness to obtain an adjusted correction coefficient Ci′ (FIG. 6B). As shown in FIG. 6C, a luminance can be raised to Q according to a brightness signal even for a pixel of a lowest input luminance by adjusting the correction coefficient. Other correction coefficients in a range of 0 to 255 before adjustment are proportionally distributed to a range of 0 to 255-Q, and added with a correction coefficient Q. A luminance of each pixel which belongs to the effective video period of the video luminance signal is adjusted using the adjusted correction coefficient.