Directional Display Optics for Privacy Viewing and Head-On Brightness
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Solution Overview
Problem
Privacy displays face challenges with high luminance loss for head-on illumination and Moiré artefacts due to micro-louvre interactions with spatial light modulators, leading to increased inventory and cost, while switchable privacy displays require improved control of off-axis optical output.
Innovation Solution
A display device comprising a pixel layer, parallax barrier layer, lens layer with birefringent lenses, and display polariser, which aligns pixels with apertures and lenses to reflect off-axis light, reducing luminance in non-viewing directions and enhancing brightness in desirable viewing directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If micro-louvre optical films are used to provide privacy function, then off-axis visibility is reduced, but head-on illumination suffers high luminance loss
Solution Approach 1:
The optical film is segmented into multiple layers with distinct functions: a first layer with microlouvers for off-axis light blocking, a second layer with microlenses for light concentration, and a third layer with color filters. This segmentation allows each layer to optimize its specific function without compromising overall performance.
Solution Approach 2:
The patent employs a composite optical film structure combining different optical elements (microlouvers, microlenses, color filters) in a single integrated layer. This composite approach enables simultaneous achievement of privacy protection and high luminance transmission by leveraging the complementary properties of each component.
2Manufacturing precision
If micro-louvre pitch is selected for panel resolution, then image quality is maintained, but inventory and cost increase
Solution Approach 1:
The optical film design uses a standardized microlouver structure that can function across different panel resolutions. The microlouver pitch and geometry are optimized to provide privacy protection while maintaining compatibility with various display pixel pitches, reducing the need for multiple specialized film variants.
Solution Approach 2:
The patent employs adjustable parameters in the microlouver design (such as pitch, width, and angle) that can be tuned to match different panel resolutions without changing the fundamental structure. This allows a single film design to adapt to multiple resolution requirements.
3Object-affected harmful factors
If parallax barrier layer is added to control viewing angles, then privacy is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the privacy control function with the existing parallax barrier structure by integrating microlouvers directly into the optical film layers. This combination eliminates the need for separate privacy control mechanisms and simplifies the overall device architecture.
Solution Approach 2:
The optical film acts as an intermediary layer between the display panel and the viewer, providing privacy control without requiring modifications to the display panel itself. This mediator approach simplifies manufacturing by keeping the privacy function in a separate, easily replaceable component.
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 provides improved brightness in desired viewing directions, reduced visibility of secondary lobes, and enhanced security by minimizing off-axis luminance, suitable for privacy and near-eye displays with high dynamic range.
Implementation Method 1
The lens layer is arranged to reflect at least some of the light received from pixels which are not aligned with that lens
Implementation Method 2
the plurality of lenses comprises one or more birefringent lenses
Implementation Method 3
the display polariser is arranged to receive light output from the lens layer and to output linearly polarised light
Data Source
AI summary
A SLM comprises emissive pixels, a parallax barrier, and a birefringent lens array. The apertures and lenses are each aligned with a respective pixel, polarisation switch, display polariser, and reflective polariser, with a switchable polar control retarder between the reflective polariser and an additional polariser. In privacy mode, pixel light transmitted by the display polariser is provided with optical power by the lens array; the parallax barrier has regions that reduce the pixel light from pixels that are not aligned with a respective lens; and the polar control retarder has a phase difference only in non-viewing directions and provides high security factor. In share mode, pixel light transmitted by the display polariser is provided with no optical power by the lens array; and the polar control retarder has no phase difference over a wide field of view and provides high image visibility. A near-eye display has increased dynamic range.