Light Guide Outcoupling Elements for Secure Viewing Mode Switching
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Solution Overview
Problem
Existing LCD screen technologies face challenges in providing secure, restricted viewing angles without significantly reducing brightness or increasing complexity, as they often require additional optical elements, result in light loss, and are costly to implement.
Innovation Solution
A screen with a transmissive image generator and a plate-shaped light guide having outcoupling elements on its surfaces or within its volume, which radiates light in a restricted angular range, maintaining high resolution and minimizing light loss by controlling the distribution and number of outcoupling elements to achieve low haze values, allowing for seamless switching between free and restricted viewing modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If accessory films based on micro-louvers are used to provide optical data protection, then restricted viewing angle is achieved, but light loss occurs and the films must be manually applied and removed
Solution Approach 1:
The patent replaces the mechanical system of manually applied micro-louver films with an integrated optical system using a light guide with controlled outcoupling elements. The light guide structure inherently provides viewing angle control through its optical design rather than requiring separate mechanical privacy filters.
Solution Approach 2:
The light guide serves multiple functions: it provides viewing angle control through its outcoupling element distribution, maintains high brightness by efficiently guiding light, and enables seamless switching between viewing modes through control of the light guide activation, eliminating the need for separate privacy filter components.
2Adaptability or versatility
If multiple backlights with complex optical elements are used to create wide and narrow illuminating angles, then viewing mode switching is achieved, but light intensity is greatly diminished and the configuration becomes complex
Solution Approach 1:
The patent extracts the viewing angle control function from complex multi-backlight systems and implements it within a single light guide structure through strategically placed outcoupling elements. This simplifies the system while maintaining the ability to provide both wide and narrow viewing angles.
Solution Approach 2:
The patent controls viewing modes by changing the activation state of the light guide, which alters the optical path and outcoupling characteristics. This parameter change (active/inactive state) enables seamless switching between viewing modes without requiring physically different optical configurations.
3Object-affected harmful factors
If scattering particles are provided in the volume of the light guide to achieve restricted viewing, then privacy protection is provided, but light is coupled out in wrong directions and brightness is reduced
Solution Approach 1:
The patent applies local quality by positioning specific outcoupling elements at predetermined locations within the light guide volume rather than using uniform scattering particles throughout. This localized approach ensures light is outcoupled only in desired directions, maintaining brightness while providing privacy protection.
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 secure, high-resolution display with minimal light loss, allowing for unrestricted viewing in one mode and restricted viewing in another, without the need for additional optical layers, thus addressing the limitations of existing technologies.
Implementation Method 1
a backlight of planar extension, which radiates light in a restricted angular range
Implementation Method 2
plate-shaped light guide... provided with outcoupling elements on at least one of its two large surfaces and/or within its volume
Implementation Method 3
The number of outcoupling elements per surface area and their extension are selected such that the light guide, on at least 50% but preferably 80% of its surface, has an average haze value of less than 7%, but preferably less than 2% or, with special preference, less than 1%
Data Source
AI summary
A screen with a transmissive image generator with pixels which is operable in at least two operating modes, B1 for a free viewing mode and B2 for a restricted viewing mode, and with an illuminating apparatus comprising a backlight that has a planar extension and radiates light in a restricted angular range, a plate-shaped light guide arranged in front of the backlight and provided with outcoupling elements on one of the large surfaces and/or within its volume, the light guide being transparent to at least 70% of the light emitted by the backlight; and light sources arranged laterally at edges of the light guide. In mode B2, the backlight is switched on and the light sources are switched off, and in mode B1 at least the light sources are switched on. In interaction with the transmissive image generator the illuminating apparatus constitutes an advantageous screen permitting the operating modes.