Variable PWM Light Source Control for Display Scroll Noise Reduction
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Solution Overview
Problem
PWM control of light sources in display devices leads to scroll noise, causing band-shaped bright and dark portions to move slowly, degrading display quality.
Innovation Solution
An image display device with a light source control unit that varies the light emission time proportion within a predetermined range, combined with a panel driving circuit and analyzing circuit to adjust transmittance or reflectance for each pixel, reducing the conspicuousness of band-shaped movements and increasing the apparent dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM control is applied to light sources, then luminance adjustment is achieved and display dynamic range is increased, but scroll noise occurs causing band-shaped bright and dark portions to move on the screen
Solution Approach 1:
The invention applies dynamics by making the light emission period variable rather than fixed. The light source control unit varies the light emission period within a predetermined range, transforming the static PWM control into a dynamic system that adapts to prevent scroll noise while maintaining luminance control capabilities
Solution Approach 2:
The invention changes the temporal parameter of light emission by varying the light emission period within a predetermined range. This parameter change disrupts the synchronization that causes scroll noise while preserving the ability to control luminance through PWM, thereby resolving the contradiction between luminance control and scroll noise elimination
2Stability of the object's composition
If the driving period of light source is fixed near integer multiple of display area driving period, then synchronization is achieved, but band-shaped bright and dark portions move conspicuously on the screen
Solution Approach 1:
The invention transforms the fixed driving period into a variable one by introducing dynamics. The light emission period is varied within a predetermined range, breaking the rigid synchronization that causes conspicuous band-shaped movements while maintaining adequate coordination between light source and display area driving
Solution Approach 2:
The invention introduces asymmetry by varying the light emission period rather than maintaining a fixed symmetric relationship with the display area driving period. This asymmetry in timing prevents the formation of regular band-shaped patterns that move conspicuously on the screen
Data Source
AI summary
An image display device includes at least one light source that emits light; at least one display area that changes, for each pixel, a transmittance or a reflectance of the light emitted from the light source; a panel driving circuit that drives the display area on the basis of an image signal indicating the transmittance or the reflectance for each pixel; and a light source control unit that controls a proportion of a light emission time of the light source in a period that varies within a predetermined range.