Head-Up Display Optical Stack for Brightness and Uniformity
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Solution Overview
Problem
Head-up display devices using liquid crystal displays face issues with display characteristics degradation due to outside light interference and low light intensity, leading to unwanted images and reduced visibility, especially in bright environments.
Innovation Solution
A head-up display device configuration that includes a light source unit with a multilayer structure comprising a diffusion member, reflective polarizer, and retardation plate, which enhances light intensity and uniformity by optimizing the optical path and polarization state of illumination light, thereby improving the display characteristics of the liquid crystal display element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional liquid crystal display device is used in a head-up display, then the device structure is simple, but outside light reflects on the display surface causing unnecessary images and deteriorating display characteristics
Solution Approach 1:
A circular polarizing plate is introduced as an intermediary component between the liquid crystal display and the external environment. This polarizing plate selectively interacts with polarized light from the display while allowing non-polarized outside light to pass through without reflection, thereby mediating between the display output and external light interference
Solution Approach 2:
The invention changes the optical parameters of the display system by implementing a circular polarization configuration. By converting linear polarization to circular polarization and back, the system creates an optical signature that distinguishes display light from outside light, enabling selective enhancement of display visibility without amplifying external interference
2Use of energy by stationary object
If the light intensity passing through the liquid crystal display is reduced, then power consumption decreases, but the virtual image becomes dark and display characteristics deteriorate
Solution Approach 1:
The circular polarizing plate configuration creates a feedback mechanism where light that passes through the liquid crystal display and the polarizing plate is reflected back through the same components. This feedback loop allows the system to recycle and reuse display light, maintaining bright virtual images while using lower backlight intensity
Solution Approach 2:
The invention ensures continuous useful action by implementing an optical path where display light is reflected back through the liquid crystal display and polarizing plate multiple times. This continuous circulation of useful light maximizes the utilization of each photon, maintaining image brightness while reducing the required input light intensity
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 significantly increases the luminance of the liquid crystal display element, suppresses degradation in display characteristics even at lower light intensities, and reduces power consumption, while enhancing the uniformity and visibility of the displayed images.
Implementation Method 1
a diffusion member, which diffuses the illumination light
Implementation Method 2
a reflective polarizer, which reflects the illumination light that has passed through the liquid crystal display element
Implementation Method 3
a reflective polarizer, which reflects the illumination light
Implementation Method 4
a retardation plate, which is a wavelength plate having a slow axis
Data Source
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AI summary
A liquid crystal display device (10) for a head-up display device includes: a light source unit (12) including a reflection film (42) provided on a substrate, and a light-emitting element (41); a liquid crystal display element (11) including a polarizer (30) provided on the light source unit (12) side, and a polarizer (31) disposed to be opposed to the polarizer (30) via a liquid crystal layer (22); a retardation plate (34) provided between the reflection film (42) and the polarizer (30), and imparting a retardation of λ/4 to light; a reflective polarizer (33) provided between the retardation plate (34) and the polarizer (30), and reflecting a light component which is parallel to a reflection axis; and a diffusion member (32) provided between the reflective polarizer (33) and the polarizer (30).