Staggered Backlight Driving for Viewfinder Flicker Reduction
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Solution Overview
Problem
Liquid crystal display devices with edge-light-type backlights experience flicker issues when reducing backlight luminance, particularly noticeable in dark environments like camera viewfinders, causing discomfort to users.
Innovation Solution
The implementation of a light source driving section that supplies driving pulses to sub-light source groups at different timings, using common lines connected through signal delay circuits, allows for controlled pulse width modulation to reduce flicker by adjusting light output in synchronization with luminance detection and video signal correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the pulse width of the PWM dimming signal is shortened to decrease backlight luminance, then power consumption is reduced, but flicker occurs in the displayed image
Solution Approach 1:
The light source group is divided into multiple sub-light source groups, each controlled by separate common lines. This segmentation allows different sub-groups to be driven at different timings, preventing simultaneous turn-off that causes flicker while still achieving overall luminance reduction and power savings.
Solution Approach 2:
The invention uses PWM (pulse width modulation) to periodically drive the light sources. By controlling the duty cycle of periodic driving pulses and implementing staggered timing across sub-groups, the system achieves average luminance control without continuous illumination, reducing power consumption while minimizing flicker through proper timing design.
2Illumination intensity
If all light sources are simultaneously turned on in a short time period to control luminance, then local dimming control is achieved, but flicker becomes more noticeable in dark environments
Solution Approach 1:
The backlight is divided into multiple light guides with separate light source groups, allowing independent control of different display regions. This enables local dimming where only specific areas are dimmed while others maintain normal brightness, improving contrast without making flicker universally visible across the entire display.
Solution Approach 2:
Different regions of the backlight are assigned different luminance levels and driving timings based on local image content requirements. By applying local dimming control to specific light guides and using staggered driving timing, the system optimizes luminance distribution while reducing flicker visibility in dark regions where it would be most noticeable.
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 approach effectively minimizes flicker in displayed images while maintaining constant luminance, reducing power consumption and improving user experience in low-light conditions.
Implementation Method 1
Light, which is emitted from the light sources, is incident into the light guide, and is emitted in a planar shape from the light guide toward the light crystal panel
Implementation Method 2
Each of the plural common lines except the common line connected to the light source driving section are connected through at least one signal delay circuit to the common line connected to the light source driving section
Data Source
AI summary
This finder display device is provided with a liquid crystal panel, a backlight, and a light source driving section. The backlight has a light guide having a side near which first to sixth light sources are disposed. The light source driving section sets the first and fifth light sources as a first sub-light source group, the second and sixth light sources as a second sub-light source group, and the third and fourth light sources as a third sub-light source group, and periodically supplies driving pulses to the first to third sub-light source groups at respectively different timings. The light source driving section controls the amounts of light of the light source groups by changing the pulse widths of the driving pulses.