Patent ID: 9213128
Filing Date: 2015-12-15
Classification: B42D,G02B

Abstract:
1. An isotropic optical filter comprising: high-index refraction material positioned between low-index-refraction matter, the isotropic filter defining a X-Y plane and a z-axis orthogonal to the x-y plane; wherein at least some of the high-index refraction material has a grated structure and lateral and vertical dimensions with respect to the low-index-refraction matter such that the high-index refraction material is operative to act as a zero-order diffractive filter for visible light incident on said isotropic optical filter; wherein the grated structure comprises at least two different grating patterns, said at least two different grating patterns differing from each other in that i) a planar grating orientation of a first of the two different grating patterns is different from a planar grating orientation of a second of the two different grating patterns, ii) a grating period of the first of the two different grating patterns is different from a grating period of the second of the two different grating patterns, or iii) a grating depth of the first of the two different grating patterns is different from a grating depth of the second of the two different grating patterns, wherein said at least two different grating patterns have grating periods smaller than 500 nm; wherein each of the at least two grating patterns defines a subpixel; and wherein a plurality of subpixels is operative to outcouple incident light to at least two zero-order wavelength spectra respective of the at least two grating patterns such to exhibit a characteristic color effect for each viewing angle, the viewing angle being defined as an angle relative to the Z-axis, the at least two grating patterns exhibiting a change of the characteristic color effect relative to a change of the viewing angle, the at least two grating patterns further exhibiting a substantial unchanged characteristic color effect for a fixed viewing angle and a rotation of the isotropic optical filter around any axis parallel to the Z-axis, said substantial unchanged characteristic color effect being defined as a weak color effect defined as hardly recognizable to the human eye.