Light Source Drive Device Gamma Correction
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Solution Overview
Problem
Conventional digital drive methods for liquid crystal display elements face issues with non-linear input-output characteristics, particularly in the lower gradation range, resulting in visually strange images due to deviations in illuminance and transmittance relationships.
Innovation Solution
A light source drive device that divides a frame period into subframes and controls the light source on a pixel-by-pixel basis, with a reduced light amount in subframes corresponding to lower gradations to align the input-output characteristic with a reference gamma curve, ensuring accurate brightness representation across all gradations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital drive methods are used with equal light amount in all subframes, then the drive method is simple and reliable, but the input-output characteristic deviates from reference gamma curve particularly in lower gradation range
Solution Approach 1:
The patent applies local quality by setting different light amounts for different subframes based on their position in the frame period. Specifically, subframes corresponding to lower gradations (earlier subframes) are assigned a first light amount, while other subframes are assigned a second light amount. This localized adjustment of light quantity according to specific subframe positions corrects the input-output characteristic deviation without requiring complete system redesign.
Solution Approach 2:
The patent changes the light amount parameter of the light source according to different subframes. By adjusting the light amount to be lower in subframes corresponding to lower gradations and higher in other subframes, the patent modifies the physical parameter of light emission to compensate for the non-linear response of liquid crystal transmittance, thereby bringing the overall input-output characteristic closer to the reference gamma curve.
2Manufacturing precision
If conventional subframe control is used, then the drive method is easy to implement, but visually strange images occur due to deviation in illuminance relationship
Solution Approach 1:
The patent applies local quality by differentiating light amount control for specific subframes versus others. The first light amount is applied to subframes corresponding to lower gradations while the second light amount is applied to other subframes. This localized differentiation corrects the illuminance relationship that causes visually strange images, improving brightness accuracy without requiring complete redesign of the drive system.
3Manufacturing precision
If equal light amount is used across all subframes, then energy consumption is uniform and simple, but lower gradation range shows significant deviation from reference
Solution Approach 1:
The patent changes the light amount parameter dynamically based on subframe position and corresponding gradation requirements. By setting a lower first light amount for subframes corresponding to lower gradations and a higher second light amount for other subframes, the patent optimizes energy consumption while improving gradation representation accuracy. This parameter adjustment compensates for the non-linear transmittance-voltage relationship in the lower gradation range.
Data Source
AI summary
Divided periods by dividing a frame of a video signal are produced. A display element is ON-OFF controlled on a pixel-by-pixel basis according to a video signal in accordance with the divided periods preassigned to each gradation. The light amount of a light source for emitting light to the display element is controlled so that a first light amount in a first divided period corresponding to the lowest gradation except black display becomes a light amount lower than a second light amount in a second divided period other than the first divided period.