Diffractive Optical Element for TN LCD Viewing Angle
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Solution Overview
Problem
Liquid crystal display devices, particularly twisted nematic (TN) types, suffer from poor viewing angle performance, resulting in decreased contrast and gray level inversion, limiting their image quality when viewed from oblique angles.
Innovation Solution
Incorporation of a diffractive optical element with specific grating regions and orientations on the display device, which diffract light to enhance contrast and brightness uniformity across various viewing angles by adjusting the diffraction grating directions and densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a TN liquid crystal display device is used, then the price is reduced, but the viewing angle is smaller and image quality deteriorates at oblique angles
Solution Approach 1:
A diffractive optical element is introduced as an intermediary component between the backlight source and the liquid crystal display panel. This element mediates the optical path by diffracting light to extend the viewing angle, allowing the TN display to achieve wide viewing angle performance without changing the liquid crystal mode or increasing cost significantly
Solution Approach 2:
The diffractive optical element changes the directional parameters of light propagation through diffraction. By adjusting the grating structure parameters (period, depth, orientation), the optical path is modified to redirect light towards oblique viewing angles, thereby expanding the effective viewing cone without altering the liquid crystal display's fundamental operating parameters
2Adaptability or versatility
If the viewing angle is increased, then the image quality at oblique angles improves, but contrast decreases and gray level reversion occurs
Solution Approach 1:
The diffractive optical element is designed with spatially varying grating structures that provide different diffraction characteristics for different regions of the display. This local optimization ensures that light is redirected appropriately for each viewing zone, maintaining contrast and gray level accuracy across the expanded viewing angle range
Solution Approach 2:
The diffractive optical element dynamically adapts the light distribution based on viewing angle. The diffraction pattern naturally adjusts the optical path length and direction for different observation angles, compensating for the liquid crystal display's inherent viewing angle limitations and maintaining image quality consistency
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 diffractive optical element significantly improves contrast and brightness uniformity, especially at side viewing angles, reducing gray level reversion and maintaining high image quality across a wider viewing range.
Implementation Method 1
a diffractive optical element which diffract light to enhance contrast and brightness uniformity across various viewing angles
Data Source
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AI summary
A display apparatus is provided. The display apparatus comprises a display device for displaying an image and a diffractive optical element (32). The diffractive optical element is disposed on a light emitting side of the display device. The diffractive optical element comprises first grating regions (43). Each of the first grating regions (43) has first diffraction gratings (44) having a constant period (D1) and the same azimuth angle (τ1). An area of the first grating regions occupies 17.5% to 94% of an area of the diffractive optical element (32).