Polarized IR LCD Illumination Without Visible Dimming
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Solution Overview
Problem
Conventional liquid crystal displays (LCDs) are limited in their usable contrast range to the visible spectrum, making them unreadable with infrared light, which is a drawback for applications requiring visibility under non-visible illumination or with infrared-sensitive equipment.
Innovation Solution
Incorporating infrared-emitting LEDs and a polarized lightguide system that maintains polarization, allowing the LCD to be readable by infrared equipment without compromising visible light transmission or appearance, using a combination of visible and infrared LEDs and polarizers that are transparent to infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional infrared-absorbing dye molecules are added to the chromophore layer of a polarizer to extend the polarizer's usable contrast range to longer infrared wavelengths, then the polarizer's usable contrast range is extended to infrared wavelengths, but the transmission in the visible range is reduced, leading to darker displays
Solution Approach 1:
The patent divides the polarizer into two separate functional layers: a visible-range polarizing layer (with PVA-iodine complexes or visible dyes) and an infrared-range polarizing layer (with infrared-absorbing dye molecules). This segmentation allows each layer to specialize in its wavelength range without the infrared dyes compromising visible transmission, as the visible polarizer layer remains unaffected by the infrared-specific chromophores added in the second layer.
2Adaptability or versatility
If wire grid polarizers are used to extend infrared contrast without absorption-based dyes, then good infrared contrast is achieved, but a metallic, mirrorlike appearance is introduced due to specular reflection
Solution Approach 1:
The patent applies different polarizer types to different locations: wire grid or reflective polarizers are used on the rear side where they provide infrared contrast without affecting the front appearance, while the front polarizer layer is designed to be non-reflective and aesthetically pleasing. This spatial differentiation allows the system to achieve infrared readability without compromising visual appearance.
3Object-affected harmful factors
If absorptive polarizers are used on the front of a display to eliminate mirrorlike appearance, then aesthetic appearance is improved, but infrared light reflection interferes with reading the display with infrared equipment
Solution Approach 1:
The patent employs a composite polarizer structure combining multiple materials with different properties: a front absorptive polarizer layer for aesthetic appearance and infrared light management, and a rear reflective polarizer layer (wire grid or birefringent) that provides infrared contrast enhancement. The combination of these materials with complementary properties enables both aesthetic appearance and infrared readability to coexist.
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
Enables extended contrast range into the infrared spectrum without reducing visible light brightness or introducing a mirror-like appearance, allowing readability by infrared-sensitive devices while maintaining visibility in the visible spectrum.
Implementation Method 1
an electrically controllable liquid crystal layer between transparent substrates changes the polarization state of the light passing through it based on applied electrical signals
Implementation Method 2
one or more polarizers and optional additional optical films transform a difference of polarization states into visible bright and dark contrast regions
Implementation Method 3
Incorporating infrared-emitting LEDs and a polarized lightguide system
Implementation Method 4
a polarized lightguide system that maintains polarization, allowing the LCD to be readable by infrared equipment without compromising visible light transmission
Data Source
AI summary
Systems and methods for IR readable transmissive and reflective displays are disclosed that do not suffer from a mirror-like appearance or undesirable dimming of the display due to sequential stacks of polarizers. The disclosed systems and methods use available IR LEDs in addition to, or in place of, visible light LEDs. An illuminator or integrator, which is a lightguide, is designed to maintain the polarization state of the light. The display can use a regular visible light, front polarizer and hence does not suffer from brightness reduction caused by an IR capable polarizer.