Method of forming volume phase reflection holograms
First Claim
Patent Images
1. A method for forming a volume phase reflection hologram comprising the steps of:
- exposing a holographic phase medium by projecting onto one of its surfaces two beams disposed at an angle to one another to form in said medium interference fringes that are substantially perpendicular to said surface and have a predetermined periodicity; and
further exposing said medium with from opposite sides with two more beams to form therein interference fringes that are parallel to said medium surfaces and of finer periodically than that of said predetermined periodicity of said perpendicular fringes so that both said parallel and perpendicular interference fringes combine to provide as exposure pattern in said medium that varies in exposure level both over the surface and depth of said medium in the form of fine generally varying multiple steps distributed depthwise in the medium within a coarser surface pattern.
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Abstract
A hologram is fabricated by opening a volume phase reflection hologram formed in a recording medium such as a positive photoresist. The opening occurs by forming a second hologram, such as an off-axis hologram, in the same recording medium. The opening hologram can be replicated in metal and the metal can be used to emboss the fringe pattern of the opened hologram into plastic. A full range of colors in the visible spectrum may be obtained by metallizing the embossed plastic structure and then by overcoating it with appropriate clear dielectric layers.
40 Citations
12 Claims
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1. A method for forming a volume phase reflection hologram comprising the steps of:
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exposing a holographic phase medium by projecting onto one of its surfaces two beams disposed at an angle to one another to form in said medium interference fringes that are substantially perpendicular to said surface and have a predetermined periodicity; and further exposing said medium with from opposite sides with two more beams to form therein interference fringes that are parallel to said medium surfaces and of finer periodically than that of said predetermined periodicity of said perpendicular fringes so that both said parallel and perpendicular interference fringes combine to provide as exposure pattern in said medium that varies in exposure level both over the surface and depth of said medium in the form of fine generally varying multiple steps distributed depthwise in the medium within a coarser surface pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for forming a volume a volume phase reflection hologram comprising the steps of:
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exposing a holographic phase medium to form in said medium interference fringes that are substantially perpendicular to said surface and have a predetermined periodicity; and further exposing said medium from opposite sides with two more beams to form therein interference fringes that are parallel to said medium surfaces and of finer periodicity than that of said predetermined periodicity of said perpendicular fringes so that both said parallel and perpendicular interference fringes combine to provide an exposure pattern in said medium that varies in exposure level both over the surface and depth of said medium in the form of fine generally varying multiple steps distributed depthwise in the medium within a coarser surface pattern.
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Specification