Grazing Incidence Illumination Device for Holographic Displays
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Solution Overview
Problem
Current illumination devices for autostereoscopic and holographic displays face challenges in achieving a thin, homogeneous, and cost-efficient design that provides a defined angular spectrum of plane waves for optimal image reconstruction, with existing solutions like wedge-type devices being inefficient due to their thickness and complexity.
Innovation Solution
A grazing incidence illumination device with a planar light guiding element and a light decoupling element having a higher refractive index than the guiding element, optimized for a refractive index difference to achieve a narrow angular spectrum of plane waves, using volume gratings for diffraction efficiency and a collimation device to tailor the wave field for homogeneous illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If wedge-type illumination devices are used, then light coupling out is achieved, but the device becomes thick and complex
Solution Approach 1:
The illumination device is segmented into functionally independent layers: a light source layer, a light guiding element, and a light decoupling element. This segmentation allows each layer to be optimized independently, achieving thin overall thickness without compromising functionality.
Solution Approach 2:
The patent transitions from wedge-type geometric thickness control to planar layering with optical path control. By using a planar light guiding element with controlled light propagation paths and decoupling elements positioned at specific locations, the device achieves thinness in the thickness dimension while managing optical complexity through spatial arrangement.
2Illumination intensity
If conventional light decoupling methods are used, then light is coupled out, but homogeneous intensity distribution is not achieved
Solution Approach 1:
The light decoupling element is designed with spatially varying properties - different regions have different decoupling characteristics to compensate for the non-uniform light intensity distribution that naturally occurs in planar light guiding elements. This local optimization achieves homogeneous overall illumination.
Solution Approach 2:
The patent controls the angular spectrum of decoupled light by adjusting parameters such as the refractive index difference between the light guiding element and decoupling element, the positioning of decoupling elements, and the optical path length. These parameter changes enable precise control over the angular distribution to achieve homogeneous intensity.
3Manufacturing precision
If refractive index difference is increased, then angular spectrum is narrowed, but manufacturing complexity increases
Solution Approach 1:
The patent introduces a refractive index matching layer or transition region between the light guiding element and the light decoupling element. This intermediary layer with intermediate refractive index facilitates the transition and simplifies manufacturing by reducing the abruptness of the refractive index change, while still achieving the desired angular spectrum control.
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 results in a thin, cost-effective illumination device that achieves a homogeneous intensity distribution and a narrow angular spectrum of plane waves, enhancing image quality and reducing manufacturing complexity, suitable for both autostereoscopic and holographic displays.
Implementation Method 1
The light guiding element has a refractive index which is significant lower than the refractive index of the at least one light decoupling element, where the entrance angle of the wave field entering the at least one light decoupling element is determined by the difference between the said refractive indices
Implementation Method 2
The injected light propagates through the planar optical light guiding element in the form of light beams or wave fields under the conditions of total internal reflection (TIR)
Implementation Method 3
using volume gratings for diffraction efficiency and a collimation device to tailor the wave field for homogeneous illumination
Data Source
AI summary
An illumination device for illuminating at least one spatial light modulator device. At least one light source device with at least one light source illuminates the at least one spatial light modulator device; a light guiding element through which light emanating from the light source propagates; and at least one light decoupling element arranged on top or inside of the light guiding element. The at least one light decoupling element decouples of a wave field of the light which propagating in the light guiding element into the direction of the spatial light modulator device. The light guiding element has a refractive index which is lower than or at least equal to the refractive index of the at least one light decoupling element. The entrance angle of the wave field entering the light decoupling element is determined by the difference between the refractive indices according to a particular equation.