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US 2004/0169929 A1Published application
Diffraction element
AssigneeAsahi Glass Company, Limited
InventorsHiromasa Sato, Yoshiharu Ooi
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AssigneeAsahi Glass Company, Limited
InventorsHiromasa Sato, Yoshiharu Ooi
Estimating the term…
A diffraction element having concave/convex-like diffraction gratings in its two surfaces from which at least two separated light beams can be taken in the same direction without changing largely the propagating direction of diffracted light even if the temperature of the operating environment changes. A diffraction grating having a concave/convex shape in cross-section is formed in the incoming-side surface of the transparent substrate and two diffraction gratings of concave/convex shape in cross-section are formed in the outgoing-side surface wherein the grating pitch of the first one is made equal to the grating pitch of one of the second ones. In addition, a reflection type diffraction element exhibiting a good wavelength dependence of diffraction efficiency without being dependent largely on the direction of polarization of an incoming light is provided. A pseudo sawtooth-like diffraction grating is formed in either surface of the transparent substrate, a reflective film is formed on a diffraction grating portion, and an antireflective film is formed on the opposite surface.
A diffraction element comprising a diffraction grating having a concave/convex shape in cross-section formed in a surface or both surfaces of a transparent substrate, wherein the diffraction element is adapted to receive light through the surface of the transparent substrate, which is opposite to the surface in which the diffraction grating is formed, in a case that the diffraction grating is formed in either one surface, and is adapted to receive light through the surface, in which the diffraction grating is formed in its central region, of the transparent substrate, in a case that diffraction gratings are formed in the both surfaces wherein a diffraction grating is formed in the central region of at least one of the surfaces.
Dependencies are inferred from the claim text.