NVIS-Compatible Backlight Light Guide Using Segmented Prisms
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Solution Overview
Problem
Existing lighting devices for liquid crystal matrix displays face challenges in achieving homogeneous backlighting for both daytime and nighttime modes, particularly in aircraft cockpits, due to the need for high brightness during the day and infrared compatibility at night, which complicates the arrangement and efficiency of light-emitting diodes and prismatic light guides.
Innovation Solution
A lighting device with a light guide composed of two right prisms, one straight and one auxiliary with an isosceles triangular base, allows for efficient diffusion and transmission of light from both daytime and nighttime sources, using semi-reflective and NVIS-filtered input faces to ensure homogeneous illumination with minimal luminance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If physical interlacing of day and night diodes is used at the rear of the guide, then both modes can be supported, but the day diode density is reduced due to larger spacings imposed by night diodes
Solution Approach 1:
The patent divides the backlighting system into two separate lighting devices: one dedicated to daytime mode and another dedicated to nighttime NVIS mode. Each device operates independently with its own optimized diode arrangement, eliminating the conflict between day and night diode spacing requirements while maintaining dual-mode functionality
2Manufacturing precision
If electronic card supporting diodes is placed far back from the guide to ensure homogeneous diffusion, then light uniformity is improved, but the overall device size increases
Solution Approach 1:
The patent transitions from a conventional planar arrangement to a three-dimensional configuration by folding the electronic card at a 90-degree angle relative to the light guide. This vertical stacking allows the card to be positioned close to the guide while maintaining sufficient distance for homogeneous light diffusion, thereby reducing the device's footprint
3Volume of moving object
If edge lighting is used for night vision, then space is saved and daytime diode density can be increased, but the setback distance remains around 10 times the thickness of the light guide
Solution Approach 1:
The patent employs a folded electronic card configuration positioned at a 90-degree angle to the light guide, enabling compact integration in the vertical dimension. This approach achieves both space efficiency and adequate setback distance for homogeneous light diffusion without requiring the excessive horizontal spacing of traditional edge lighting
4Manufacturing precision
If local dimming is implemented to compensate extraction gradient, then homogeneous diffusion is maintained, but the cost increases due to integrated adjustment electronics and calibration
Solution Approach 1:
The patent removes the complex local dimming electronics and calibration requirements by using a simplified uniform lighting approach. The design accepts a standard extraction gradient without active compensation, thereby eliminating the need for expensive individual diode control electronics while maintaining adequate performance
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 highly homogeneous and efficient backlighting for both modes with reduced complexity and cost, maintaining high power levels during the day while ensuring compatibility with Night Vision Imaging Systems, and achieving compactness and ease of integration.
Implementation Method 1
transmit the light provided by each of the two backlight sources from the lower face of the guide, to diffuse it by the upper face of the guide
Implementation Method 2
a specific filter called an 'NVIS' filter which makes it possible to filter infrared and near infrared radiation
Implementation Method 3
using semi-reflective and NVIS-filtered input faces
Data Source
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AI summary
A device for backlighting a liquid crystal matrix of a flat panel display in daytime vision mode, or nighttime with NVIS compatibility includes a light guide GL whose shape is decomposed into two right prisms end to end in a longitudinal direction: a main right prism PP which is a rectangular block whose upper face, disposed below and in a plane parallel to the rear face of the matrix, forms the output face fsp of the light guide and a lateral face is a main input face feP for a daytime illumination source SD and for a nighttime illumination source SN;and an auxiliary right prism PA in the extension of this main entrance lateral face, which is a right prism whose base has the shape of a right isosceles triangle, and whose rectangular lateral faces are used, one as the light exit face of the entrance stage and which is of the same rectangular dimensions and placed against, or coinciding with, the main entrance lateral face feP; and the other two faces as light entrance faces fe1A, fe2A, each associated with a respective light source and at least one entrance face fe1A is semi-reflective.;