Collimated LED Backlight for Wide-Field Multiscopic Displays
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Solution Overview
Problem
Conventional liquid crystal display (LCD) based head-up displays (HUDs) struggle to achieve sufficient brightness levels for legible images in high ambient light conditions, especially when a large field of view is required, exacerbated by multiscopic optical elements that further reduce brightness, leading to eyestrain and reduced usability.
Innovation Solution
A backlight unit with an array of light-emitting elements surrounded by cavity reflectors and a collimator, combined with a collimator and additional components like a transparent diffuser, brightness enhancement film, and reflecting polarizers, to minimize light wastage and enhance brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional edge-lit backlight unit is used, then the device complexity is low, but the brightness level is insufficient for legible images in high ambient light conditions
Solution Approach 1:
The backlight unit is segmented into multiple independent light-emitting elements (LEDs) arranged in an array, with each element individually controllable. This segmentation allows precise control of light output to achieve high brightness levels while managing complexity through modular design
Solution Approach 2:
Cavity reflectors are nested around each light-emitting element, creating a hierarchical structure where reflective surfaces are integrated within the backlight unit architecture. This nesting maximizes light extraction and directionality without proportionally increasing overall device complexity
2Area of stationary object
If the field of view is increased to cover a larger area, then the display coverage is improved, but the brightness per pixel area is reduced
Solution Approach 1:
The system changes the operational parameters of individual light-emitting elements based on their spatial position and the required field of view. By dynamically adjusting the intensity and activation of specific LEDs, the system maintains high brightness across the entire display area while accommodating wide field of view requirements
3Adaptability or versatility
If multiscopic optical elements are added for autostereoscopic effect, then the 3D display capability is improved, but the overall brightness is further reduced
Solution Approach 1:
The backlight unit maintains continuous high brightness output through coordinated operation of multiple light-emitting elements, ensuring that the addition of multiscopic optical elements does not result in brightness loss. The system continuously adjusts light emission to compensate for any light attenuation introduced by optical components
4Device complexity
If the number of photo-emitting cells is limited, then the device complexity is reduced, but the brightness distribution over a large area becomes non-uniform
Solution Approach 1:
Each light-emitting element is designed with local quality optimization, including individual cavity reflectors and control circuits tailored to its specific position in the array. This allows non-uniform brightness distribution to be compensated by adjusting individual element output, achieving overall uniformity without requiring an excessive number of photo-emitting cells
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 enables high brightness suitable for autostereoscopic and multiscopic displays, allowing legible images in various lighting conditions, including bright daylight, with a wide field of view, and reducing eyestrain.
Implementation Method 1
A backlight unit with an array of light-emitting elements surrounded by cavity reflectors and a collimator, combined with a collimator and additional components like a transparent diffuser, brightness enhancement film, and reflecting polarizers, to minimize light wastage and enhance brightness.
Implementation Method 2
A backlight unit with an array of light-emitting elements surrounded by cavity reflectors and a collimator
Implementation Method 3
additional components like a transparent diffuser, brightness enhancement film, and reflecting polarizers
Implementation Method 4
additional components like a transparent diffuser, brightness enhancement film, and reflecting polarizers
Implementation Method 5
additional components like a transparent diffuser, brightness enhancement film, and reflecting polarizers
Data Source
Figure 1~2A
Figure 2B
Figure 2C
AI summary
A backlight unit (100, 202, 404) for a liquid crystal display device (200, 302, 402) is disclosed. The backlight unit comprises an array of light-emitting elements (102a-c) and a plurality of cavity reflectors (104a-c), wherein a given cavity reflector partially surrounds a corresponding light-emitting element of said array. The backlight unit further comprises a collimator (106) arranged on an optical path of the array of light-emitting elements, a first drive circuit that is employed to individually control the light-emitting elements of said array, and a controller. The controller is configured to generate or receive drive signals for controlling the light-emitting elements of said array, and send the drive signals to the first drive circuit.