Optical Structure Achromatic Compensation via Diffractive Alignment
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Solution Overview
Problem
The existing optical structures with submillimeter-order reflecting structures suffer from chromatic dispersion when illuminated, leading to unintended coloration and compromised image quality, particularly when combined with diffractive surface reliefs, as the chromatic dispersion is not adequately considered in their design.
Innovation Solution
An optical structure featuring an embossed layer with a recording area containing both refractive mirror and diffractive areas, where the local mirror and diffractive structures are aligned such that their normal and grating vectors are similar, allowing the diffracted light to mix with reflected light and cancel out chromatic dispersion, thereby maintaining achromatic color representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a submillimeter-order reflecting structure is used to form an embossed recording body, then the security device can produce optical effects through refraction and reflection, but chromatic dispersion occurs at the transparent protective layer boundary causing unintended coloration and deteriorated image quality
Solution Approach 1:
The patent converts the harmful chromatic dispersion effect into a beneficial compensation mechanism by introducing a diffractive structure that produces opposite chromatic dispersion. The diffractive structure's wavelength-dependent phase delay counteracts the refractive structure's chromatic dispersion, transforming the harmful coloration effect into a corrective mechanism that achieves achromatic optical output.
Solution Approach 2:
The patent employs a composite optical structure combining refractive and diffractive elements within the same embossed recording body. The refractive structure (inclined mirrors) and diffractive structure (periodic pattern) work together in a composite configuration, where each component addresses different aspects of the optical performance - the refractive structure provides the primary optical effect while the diffractive structure compensates for chromatic dispersion.
2Reliability
If a diffractive structure is combined with the embossed recording body to enhance security features, then counterfeiting prevention is improved, but the unintended coloration from chromatic dispersion is not addressed and image quality remains impaired
Solution Approach 1:
The patent merges the security function and the chromatic dispersion compensation function into a single integrated diffractive structure. Rather than adding separate components, the diffractive pattern is embedded within the embossed recording body itself, combining multiple functions - security verification, optical effect generation, and chromatic dispersion compensation - into one unified structure.
3Illumination intensity
If an inclined mirror is used in the refractive structure, then the desired optical reflection effect is achieved, but the angle of emission does not match the chromatic dispersion amount, preventing effective color neutralization
Solution Approach 1:
The patent adjusts the parameters of the diffractive structure (period, depth, orientation) to match and compensate for the specific chromatic dispersion characteristics produced by the inclined mirror configuration. By optimizing the diffractive structure's parameters, the system achieves effective chromatic dispersion compensation while maintaining the desired optical reflection intensity from the inclined mirrors.
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 configuration effectively compensates for chromatic dispersion, ensuring that the embossed recording body maintains its intended color and improves image quality by aligning the azimuth directions of the local mirror and diffractive structures, resulting in stable and accurate color representation.
Implementation Method 1
an optical structure comprising a hologram and a diffraction grating has been widely used for such security devices
Implementation Method 2
the incident light is refracted at the boundary between the transparent protective layer and the outside of the transparent protective layer
Implementation Method 3
a technique has been proposed in which a lens structure is formed with sub-millimeter order minute irregularities, and an embossed recording body is configured by refraction and reflection occurring at the surface of the lens structure
Data Source
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Figure 5~7(b)
AI summary
An optical structure comprises an embossed layer having an embossed face including a recording area, the recording area including an embossed recording body having an uneven structure; and a light reflecting layer covering a part or the entirety of the recording area. The recording area includes a refractive mirror area and a diffractive area in the vicinity of the refractive mirror area. The refractive mirror area includes a plurality of aligned inclined mirrors constituting the embossed recording body, and the diffractive area has a diffractive structure. The refractive mirror area has a plurality of local mirror structures, and the diffractive area has a plurality of local diffractive structures. Each pair of the local diffractive structure and the local mirror structure adjacent to the local diffractive structure forms one local structure.