Diffractive Optical Grating Layout for Brighter Multi-View Images
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Solution Overview
Problem
Diffractive devices designed to exhibit variable images face challenges in maintaining color saturation and brightness due to the reduction in grating elements when miniaturized for multiple views, making them susceptible to counterfeiting.
Innovation Solution
Employing elongate grating regions along a common direction to maximize the number of grating elements, ensuring improved color saturation and brightness by optimizing the number and orientation of grating elements within the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If diffraction gratings are miniaturized to provide multiple views, then device complexity is reduced and multiple images are achieved, but the number of grating elements decreases causing poor color saturation and brightness
Solution Approach 1:
The patent transitions from square grating regions to elongate grating regions, changing the dimensional characteristics from isotropic (equal dimensions) to anisotropic (different dimensions). This dimensional change allows the grating regions to maintain sufficient grating element counts along the elongation direction while reducing size in the perpendicular direction, thereby achieving multiple views without sacrificing color saturation and brightness.
2Device complexity
If grating regions are reduced in size for multiple views, then device complexity is improved, but resolving power and color quality deteriorate
Solution Approach 1:
By changing from square to elongate geometry, the patent optimizes the aspect ratio of grating regions. This dimensional transformation allows the regions to be smaller overall while maintaining sufficient length in the direction critical for resolving power, thus achieving multiple views without compromising the ability to resolve different wavelengths.
Solution Approach 2:
The patent applies different dimensional characteristics to different parts of the grating structure. The elongate grating regions have optimized dimensions where the length along the elongation direction provides sufficient resolving power, while the reduced perpendicular dimension enables multiple views. This local optimization of geometry resolves the contradiction between size reduction and maintaining measurement precision.
3Illumination intensity
If grating regions are made elongate, then color saturation and brightness are improved, but device complexity increases
Solution Approach 1:
The patent applies a specific geometric quality (elongate shape) to the grating regions where it is most needed - in the direction that determines color saturation and brightness. By localizing the elongation to the critical dimension for optical performance while reducing the non-critical dimension, the patent improves color quality without unnecessarily increasing overall device complexity.
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 use of elongate grating regions enhances color saturation and brightness, allowing for more distinctive and recognizable optical effects, particularly in security devices, by maximizing the number of grating elements while reducing the perceptibility of interlacing patterns.
Implementation Method 1
When white light is incident upon a diffraction grating, it is split into its constituent wavelengths (i.e. colours) according to the diffraction grating equation
Implementation Method 2
the number of grating elements illuminated by the incident light determines the closest resolvable wavelength, with the resolving power R of the grating given by R = λ/Δλ = mN
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~4
AI summary
An optical device is disclosed. Upon illumination, the optical device exhibits one or more diffractive images dependent upon viewing angle, said optical device having a diffractive structure comprising a plurality of grating regions, each grating region corresponding to a component of a respective diffractive image, wherein: each grating region of the diffractive structure comprises a plurality of grating elements arranged along a respective first direction, each grating element having a principal component of orientation within the plane of the device that is substantially orthogonal to said respective first direction; wherein, the grating elements within each grating region have a constant pitch and substantially the same orientation such that each grating region, upon illumination, exhibits a diffractive colour such that the corresponding diffractive image is exhibited; wherein, the diffractive structure comprises first and second grating regions that are both elongate along a common first direction, said first and second grating regions being adjacent along said common first direction, and wherein the pitch and/or orientation of the grating elements of the first and second grating regions are different. A method of forming the optical device is also disclosed.