Switchable Privacy Screen with Light Guide
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Solution Overview
Problem
Existing display technologies face challenges in providing secure, restricted viewing angles without significantly reducing brightness or increasing complexity, as they often require mechanical attachments, complex optical elements, and suffer from light loss or residual visibility issues.
Innovation Solution
A screen with a planar backlight and a transmissive imager, optionally using a plate-shaped light guide with scattering particles, allows for operation in two modes: a free viewing mode with unrestricted angular range and a restricted viewing mode, achieved by adjusting light sources and light guides to minimize residual visibility and maintain high resolution with minimal light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If accessory films with microlouvers are used to achieve restricted viewing angle, then privacy protection is improved, but light loss increases and the films must be manually attached and removed
Solution Approach 1:
The patent implements a switchable privacy filter that can dynamically change between transparent and opaque states using an electric field (ITO electrode layers), allowing the viewing angle restriction to be activated or deactivated as needed. This dynamic control eliminates the need for manual attachment and removal of fixed privacy films, and allows users to choose when privacy protection is required, thereby managing light loss only when necessary.
Solution Approach 2:
The privacy filter's optical properties are changed by applying an electric field between ITO electrode layers, which alters the alignment of liquid crystal molecules or chromonic particles. This parameter change (from aligned to random orientation) switches the filter between transparent and opaque states, enabling controlled privacy protection without permanent light loss.
2Object-affected harmful factors
If microlouver films are applied for privacy mode, then viewing angle restriction is achieved, but the films must be carried separately and cannot be switched between modes
Solution Approach 1:
The privacy filter is integrated into the display assembly with switchable control, allowing seamless transition between transparent and opaque states through electrical actuation. This eliminates the need to manually attach and detach separate films, and the filter remains in position while changing optical properties on demand.
Solution Approach 2:
The privacy filter is merged with the display structure itself, with the ITO electrode layers and switching mechanism integrated into the existing display assembly. This combination eliminates the need for separate carryable films and creates a unified system where privacy protection is an inherent, switchable feature of the display.
3Object-affected harmful factors
If liquid crystals between chromonic layers are used for switching, then privacy mode is achieved, but light loss occurs and implementation becomes complicated
Solution Approach 1:
The ITO electrode layers serve multiple functions: they provide the switching mechanism for the privacy filter, maintain the structural integrity of the display assembly, and can potentially serve as transparent conductors for other display functions. This multi-functionality reduces the need for additional specialized components, simplifying implementation.
Solution Approach 2:
The system uses electric field-induced parameter changes in liquid crystals or chromonic particles to achieve privacy mode switching. By controlling the orientation state through voltage application to ITO electrodes, the system achieves mode switching through a well-established, relatively simple mechanism rather than complex mechanical or optical arrangements.
4Object-affected harmful factors
If two backlights with wedge-shaped light guides are used to create wide and narrow illuminating angles, then viewing angle control is achieved, but light intensity is reduced by a factor of 5 or higher
Solution Approach 1:
The invention extracts the viewing angle control function from the backlight system itself and places it in a separate privacy filter layer. The single backlight provides full brightness without angular restriction, while the privacy filter selectively controls the viewing angle of the emitted light. This separation allows the backlight to operate at full intensity while the filter provides the necessary viewing angle control.
Solution Approach 2:
The privacy filter acts as an intermediary between the backlight and the viewer, controlling the viewing angle without requiring modification of the backlight's light emission characteristics. This intermediary approach allows the backlight to maintain full brightness while the filter provides selective viewing angle control, avoiding the light loss associated with attempting to control viewing angle directly at the backlight level.
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 information presentation with optional restricted viewing angles, maintaining high resolution and minimal light loss across both modes, suitable for confidential data entry or display on devices like ATMs and mobile devices, without the need for complex optical elements or high-power UV sources.
Implementation Method 1
a plate-shaped light guide 3, which is also arranged in front of the backlight 2 (seen in the viewing direction) and consists of a thermoplastic or thermoelastic material with scattering particles being homogeneously distributed therein
Data Source
AI summary
A screen having a free-viewing mode and a restricted-viewing mode, comprising a backlight emitting light into an unrestricted angular range in the free-viewing mode, and into a restricted angular range in the restricted-viewing mode. A transmissive imager is in front of the backlight. Light sources are outside the display area of the imager, and a transparent plate-shaped light guide scattering particles distributed therein is in front of the imager. In the free-viewing mode, the light sources are off, so that light from the backlight passing the imager passes the light guide unaffected. In the restricted-viewing mode, the lights are on, so that light radiating into a restricted angular range and passing the imager is superimposed by light that is scattered into the viewing space due to irradiation of light from the light guide. Thereby, the visibility of an image on the imager is reduced outside the restricted angular range.