LCD Confidential Viewing via Variable Polarizer Inversion
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Solution Overview
Problem
Existing technologies for confidential viewing of LCD displays are inadequate, as they either rely on physical barriers that are not secure, require specialized eyewear, or are not suitable for high-refresh-rate LCDs, and lack the ability to easily switch between standard and secure viewing modes.
Innovation Solution
An LCD display configuration with a variable polarizer that rapidly alternates between inverted states, combined with shutter glasses or synchronized eyewear, to render the image indecipherable to the naked eye while allowing intended viewers to decode the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a masking image is introduced to obscure the view from unintended viewers, then viewing security is improved, but the display cannot be readily switched between standard and confidential modes
Solution Approach 1:
The patent applies dynamics by making the polarizer state changeable through voltage control. The liquid crystal layer rotates the polarization plane dynamically based on applied voltage, allowing the display to switch between confidential mode (with masking image) and standard mode (without masking image). This dynamic control enables easy switching between viewing modes while maintaining security when needed.
Solution Approach 2:
The patent changes the polarization parameter of the light passing through the display. By controlling the liquid crystal layer to rotate the polarization plane by specific angles (e.g., 45 degrees), the system can selectively allow or block certain polarization states. This parameter change enables the display to transition between secure and insecure viewing modes without physical reconfiguration.
2Manufacturing precision
If the display refresh rate is increased to provide flicker-free performance, then image quality is improved, but the masking image cannot be effectively displayed
Solution Approach 1:
The patent uses periodic action by alternating the polarization state of the masking image at a frequency that is a multiple of the display refresh rate. The liquid crystal layer is switched between different polarization states in a periodic manner, creating a masking effect that works regardless of the high refresh rate. This periodic switching enables the masking image to be effectively displayed even at high refresh rates where conventional methods fail.
3Reliability
If physical barriers such as anti-glare privacy screens are used, then viewing security is partially improved, but the security is insufficient against shoulder peering
Solution Approach 1:
The patent introduces an intermediary mechanism - the liquid crystal layer that controls polarization - between the display and the viewer. This intermediary dynamically adjusts the polarization state of light based on voltage control, creating a masking image that blocks viewing angles from unauthorized viewers. The polarization-based masking is more effective than physical barriers because it can be controlled electronically and provides better security against various viewing angles including shoulder peering.
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
Provides secure and flicker-free confidential viewing by rendering the display as a 50% gray, featureless image to unauthorized viewers, with easy switching between modes without altering the original image data, and supports full color/full motion graphics.
Implementation Method 1
an optical rotator, such as a liquid crystal cell... rapidly rotates the polarized light passing therethrough between approximate orthogonal positions
Implementation Method 2
one of the polarizers of the image display device is configured as a variable polarizer which is capable of rapidly alternating between inverted states of polarization
Data Source
AI summary
A display apparatus having a pair of polarizers with an optical rotator therebetween, one of the polarizers being a variable polarizer which is independently operated to alternate between substantially orthogonal states of polarization and cause the display to rapidly alternate between a normal positive and inverted negative image, creating a combined neutral image that in indecipherable to the naked eye. Shutter eyewear synchronized with the variable polarizer is used to extract the positive image for viewing by an intended viewer. In another embodiment, both polarizers of the display apparatus are independently variable, which allows for viewing of the desired image using passive polarized eyewear or eyewear incorporating synchronized variable polarizing rotators. Faster independent operation of the variable polarizers provide for flicker-free viewing of the desired image and convenient switching between normal and secure modes of operation, without physical alteration of the display.