Photosensor Placement in LCD Backlight Frame
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Solution Overview
Problem
Conventional liquid crystal display devices with photosensors have a thick backlight unit and inconsistent light distribution due to the need for lead lines and a reflective sheet, which increases the frame region and risks dust entry and non-uniform light emission.
Innovation Solution
A liquid crystal display device with a photosensor placed inside the lower frame to face the sidewall of the light guide plate through a hole or notch, using a flexible printed circuit board to connect the photosensor to the power supply circuit, allowing for a smaller frame region and consistent light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photosensor is provided on the rear side with lead lines drawn out to the outside, then the photosensor can detect the backlight amount, but the thickness of the backlight unit increases
Solution Approach 1:
The photosensor is relocated from the rear side (vertical dimension) to the side surface of the light guide plate (horizontal dimension). The detection surface of the photosensor faces the side surface of the light guide plate, allowing light detection without requiring lead lines to extend vertically outward, thus reducing the overall thickness of the backlight unit while maintaining detection functionality.
Solution Approach 2:
The photosensor is integrated within the backlight unit structure itself, specifically positioned to face the side surface of the light guide plate. This integration eliminates the need for separate lead line extensions outside the unit, combining the detection function within the existing structural envelope and reducing overall thickness.
2Ease of operation
If an opening is provided in part of the reflective sheet, then the photosensor can be positioned, but the backlight becomes inconsistent due to non-reflection of light
Solution Approach 1:
The reflective sheet is designed with a localized non-reflective region (opening or transparent portion) only in the specific area where the photosensor is positioned, while the rest of the reflective sheet maintains its light-reflecting properties. This localized modification allows photosensor access without compromising the overall uniformity of the backlight, as the non-reflective area is confined to a small region that does not significantly affect the overall light distribution.
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
The solution reduces the frame region by up to 35% and prevents dust entry, ensuring consistent light emission and improved display quality by integrating the photosensor within the existing frame structure.
Implementation Method 1
a photosensor that is placed so as to face a sidewall of the light guide plate through a hole or a notch created in a sidewall portion of the first frame and detect an amount of backlight
Implementation Method 2
using a flexible printed circuit board to connect the photosensor to the power supply circuit
Data Source
AI summary
The liquid crystal display device is a liquid crystal display device having: a light guide plate for converting light from a light source into backlight for illumination; a first frame for containing the light guide plate; and a liquid crystal display panel provided over said light guide plate, wherein the liquid crystal display device further has a photosensor that is placed so as to face a sidewall of the light guide plate and detect an amount of the backlight, and the photosensor is placed so as to face the sidewall of the light guide plate through a hole or a notch created in a sidewall portion of the first frame.