| 摘要 |
A method and apparatus for viewing or authenticating a diffractive device and a diffractive security device (1) are provided in which a first diffractive relief structure (200) is responsive to a first wavelength of visible monochromatic light, a second diffractive relief structure (200) is at least partially interlaced with the first diffractive relief structure (100) and responsive to a second wavelength of visible monochromatic light, and a third diffractive relief structure (400) is at least partially interlaced with the first and second diffractive relief structures (100, 200) and responsive to a third wavelength of visible monochromatic light. Under illumination by the first, second and third wavelengths of monochromatic light, the first diffractive relief structure (200) produces a first partial image of a first color in a reconstruction plane, the second diffractive relief structure (300) produces a second partial image of a second color in the reconstruction plane and the third diffractive relief structure (400) produces a third partial image of a third color in the reconstruction plane, and the first, second and third partial images at least partially overlap in the reconstruction plane to form a multicolored image. The diffractive security device may be used in a security document and the device may be authenticated by comparing the multicolored image to a reference image. |
| 主权项 |
1. A method of viewing or authenticating a diffractive device the method comprising the steps of:
providing a diffractive device having a first diffractive relief structure responsive to a first wavelength of visible monochromatic light, a second diffractive relief structure responsive to a second wavelength of visible monochromatic light, and a third diffractive relief structure responsive to a third wavelength of visible monochromatic light; illuminating the diffractive device with a first beam of visible monochromatic light of the first wavelength to produce a first partial image of a first color in a reconstruction plane, illuminating the diffractive device with a second beam of visible monochromatic light of the second wavelength to produce a second partial image of a second color in the reconstruction plane, and illuminating the diffractive device with a third beam of visible monochromatic light of the third wavelength to produce a third partial image of a third color in a reconstruction plane, wherein: the first, second and third diffractive relief structures are each numerical-type diffractive optical elements (DOEs) comprising first, second, and third groups of interlaced pixels, respectively, such that the first, second, and third diffractive relief structures are at least partially interlaced relative to one another,the first, second and third partial images at least partially overlap in the reconstruction plane to form a multicolored image, andthe first, second and third colors of the partial images correspond to three colors of a multicolored input image. |
