Non-repeating Optical Element for Wavelength-Independent Scattering
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Solution Overview
Problem
Existing optical diffusers face challenges in achieving uniform luminance and controlled scattering behavior over a surface, with limitations in wavelength independence and the presence of unwanted direct imaging of the radiation source due to the 0th diffraction order, particularly in diffractive and microlens array technologies.
Innovation Solution
An optical element with a non-repeating surface structure featuring continuous, individually designed elevations that provide a phase shift greater than two and a half times the largest wavelength used, calculated using a modified iterative Fourier Transform Algorithm to avoid phase dislocations and ensure wavelength independence, allowing for precise control of scattering distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If diffractive optical elements are used to precisely define scattering characteristics, then the scattering distribution can be specified arbitrarily with respect to intensity and angular distribution, but the elements exhibit strong wavelength dependence and only a limited fraction of light passes through the diffuser after scattering
Solution Approach 1:
The surface is divided into multiple individually designed elevations rather than using a periodic grating structure. Each elevation is independently optimized to contribute to the overall scattering distribution, allowing the system to achieve wavelength-independent scattering by summing the effects of many non-periodic elements
Solution Approach 2:
Each elevation on the surface has locally optimized properties (height, lateral extent, shape) that are specifically designed to achieve the desired scattering characteristics. The elevations are continuously varying rather than uniform, allowing precise local control of the scattering function while maintaining broadband performance
2Manufacturing precision
If diffractive optical elements are used to control scattering, then arbitrary intensity distribution can be generated, but a significant portion of light passes through unimpeded resulting in disruptive zeroth order diffraction
Solution Approach 1:
The harmful zeroth order diffraction component is extracted and eliminated by using a non-periodic elevation structure. The continuous, individually designed elevations ensure that all incident light is scattered into higher diffraction orders, completely removing the undiffracted zeroth order beam that causes direct visibility of the light source
Solution Approach 2:
The periodic symmetry of conventional diffraction gratings is replaced with asymmetric, continuously varying elevation positions and shapes. This asymmetry breaks the conditions that produce strong zeroth order diffraction, directing all light into scattered higher orders while maintaining precise control over the scattering distribution
3Ease of operation
If lens arrays are used to realize diffusion disks and diffusers, then diffusion can be achieved under incoherent illumination, but periodic structures cause undesirable diffraction patterns under collimated or spectrally narrowband illumination
Solution Approach 1:
The periodic array structure of conventional lens arrays is replaced with a non-periodic distribution of elevations. This eliminates the regular spacing that causes diffraction patterns under collimated illumination, while the elevations still provide the necessary light scattering and diffusion functions for both coherent and incoherent sources
4Ease of operation
If lens arrays are used for diffusion, then diffusion can be achieved, but dead zones between lenses cause light to pass through without being scattered
Solution Approach 1:
The discrete lens elements of traditional arrays are merged into a continuous surface profile composed of individually designed elevations. This eliminates the dead zones between lenses by ensuring continuous coverage of the surface, so that all incident light interacts with the scattering structure rather than passing through unscattered regions
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 enables efficient scattering of collimated radiation over a larger area, suppresses the 0th diffraction order, and allows for achromatic scatter distributions, reducing visibility of the radiation source and enabling precise angular and intensity control across the visible spectrum.
Implementation Method 1
elevations which have a height at which a phase shift Δφ, which is greater than two and a half times the largest wavelength used, is achieved
Data Source
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AI summary
The invention relates to an electromagnetic optical element which scatters radiation in a diffuse manner. Such optical elements can be used in nearly all projection applications including front and rear projection, display applications, (cinema) screens and similar. On the surface of a claimed optical element, a surface profile is provided, the surface structure of which is non-repeating and irregular. Elevations are formed that have a height by means of which a phase shift Δφ may be achieved that is greater than two and a half times the longest wavelength used, and the elevations have a lateral extension in one plane respectively, in all axial directions, that is greater than five times the longest wavelength used. The individual elevations have a continuous form in the three spatial axial directions and said elevations are devoid of edges, ledges and fissures.