Kinoform Diffractive Light Pipe Parasitic Image Reduction
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Solution Overview
Problem
Existing light pipes for electronic display arrangements suffer from parasitic images due to diffraction in higher orders of the kinoform surface, which are caused by fabrication defects during the engraving process, leading to visibility issues and discomfort for the user.
Innovation Solution
The light pipe incorporates a diffractive component with a power range defined by D(Thresh,X) = DOPTDIF(Thresh) INTERSECTION DXT(X), where DOPTDIF(Thresh) is determined by acceptable diffraction efficiency and transverse chromatic aberration thresholds, minimizing parasitic image visibility by optimizing the diffractive power and step height of the kinoform surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a kinoform diffractive component is used in the inlet surface, then chromatic aberration is minimized, but parasitic images appear due to diffraction in higher orders
Solution Approach 1:
The patent modifies the diffractive component parameters by optimizing the groove depth and pitch ratios to control diffraction efficiency. By adjusting these geometric parameters, the system maximizes light directed to the first diffraction order while minimizing higher-order diffraction that causes parasitic images, thus resolving the contradiction between optical quality and parasitic image generation
Solution Approach 2:
The patent applies anti-reflective coatings selectively at specific locations on the optical components rather than uniformly across all surfaces. This partial application targets the critical interfaces where reflections would most significantly contribute to parasitic images, reducing their intensity without requiring complete coverage that would increase manufacturing complexity
2Illumination intensity
If the diffractive power is increased to improve image brightness, then the main image becomes brighter, but parasitic images become more visible
Solution Approach 1:
The patent optimizes the groove depth-to-pitch ratio parameter of the diffractive component to achieve maximum diffraction efficiency into the first order. By carefully selecting this ratio, the system achieves high main image brightness while suppressing higher-order diffraction, thus preventing parasitic images from becoming visible even at high diffractive powers
Solution Approach 2:
The patent creates multiple diffractive components with varying groove depths and pitches, then selects or combines them to achieve optimal performance. This approach allows systematic exploration of parameter space to find configurations that maximize brightness while minimizing parasitic images
3Object-generated harmful factors
If fabrication precision is improved to reduce parasitic images, then manufacturing complexity increases
Solution Approach 1:
The patent identifies specific ranges for groove depth and pitch parameters that inherently suppress higher-order diffraction. By designing within these optimized parameter ranges, the system achieves low parasitic image intensity using conventional fabrication techniques, avoiding the need for ultra-precision manufacturing that would significantly increase complexity and cost
Solution Approach 2:
The patent performs preliminary optical design and parameter optimization before the fabrication process. By calculating and selecting optimal groove dimensions in advance, the design compensates for typical fabrication variations, ensuring that parasitic images remain suppressed even with standard manufacturing tolerances
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
This approach significantly reduces the visibility of parasitic images by accurately calculating and optimizing the diffractive power, minimizing transverse chromatic aberration, and controlling light distribution, resulting in improved optical performance and user comfort.
Implementation Method 1
a diffractive component formed directly in the inlet surface 1A... diffraction in higher orders of the kinoform surface... fraction of light diffracted in order 1 relative to the quantity of incident light
Implementation Method 2
This asphero-diffractive surface of 'kinoform' type has the function of minimizing astigmatism and field curvature, and also of minimizing chromatic aberration
Data Source
AI summary
A light pipe is provided for transmitting light signals from one of its ends to its other end facing toward the eye of a user for viewing a virtual image. The light pipe includes a diffractive component formed directly in the inlet surface. The diffractive component is an element satisfying the equation of an aspherical component of revolution of the “kinoform” type, where the diffractive component of the pipe has power situated in a range D (Thresh, X) defined by D(Thresh, X)=DOPTDIF(Thresh) INTERSECTION DXT(X).