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US08743459B2 Optical security device offering 2D image 失效
提供2D图像的光学安全设备

Optical security device offering 2D image
摘要:
The present invention provides for a diffractive element comprising a diffractive optical microstructure consisting of a modulated structure of a diffractive type which upon illumination by diffused ambient light creates a two-dimensional image to be viewed by an observer upon tilting or rotating the device or by varying lighting direction, wherein the diffractive modulated structure of the device consists of various generally parameterised special optical elements with specifically prescribed groove shapes, wherein each groove shape, position, center(s), and line thickness, are described by functions describing those dependencies which are variables of the positional coordinate of the optical element.
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