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Image display apparatus
| Details |
Inventors: Endo, Takeshi; Kasai, Ichiro; Morimoto, Takashi; Noda, Tetsuya;
Assignee: Minolta Co., Ltd. (Osaka, JP)
Primary Examiner: Juba, Jr.; John
Assistant Examiner:
Attorney, Agent or Firm: Sidley Austin Brown & Wood LLP
A holographic element is a reflective holographic element formed on a substrate and constituted by a composite hologram having a plurality of patterns of interference fringes composed of interference fringes nonparallel to the substrate. The holographic element forms, out of image light having a predetermined wavelength width emanating from an image display element, a plurality of observation pupils at spatially different locations, and acts in such a way as to fulfill prescribed conditions for an identical incident ray over the entire area in which the image light is incident on the holographic element. |
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DETAILED DESCRIPTION An object of the present invention is to provide an inexpensive image display apparatus that forms an observation pupil that permits easy observation of the displayed image.
To achieve the above object, according to one aspect of the present invention, a holographic element is a reflective holographic element formed on a substrate and composed of a composite hologram having a plurality of patterns of interference fringes composed of interference fringes nonparallel to the substrate.
This holographic element forms, out of image light having a predetermined wavelength width emanating from an image display element, a plurality of observation pupils at spatially different locations, and acts sin such a way as to fulfill conditional formulae (I) and (II) below for an identical incident ray over the entire area in which the image light is incident on the holographic element: .
DELTA.
.
theta.
<2 (I) .
DELTA.
.
eta.
>50 (II) where .
DELTA.
.
theta.
represents the difference (.
degree.
) in angle of diffraction among the different patterns of interference fringes; and .
DELTA.
.
eta.
represents the difference (%) in diffraction efficiency among the different patterns of interference fringes.
According to another aspect of the present invention, an image display apparatus is provided with an image display element for displaying a two-dimensional image, an enlargement optical system for projecting, with enlargement, the image displayed on the image display element, and a holographic element as described above included in the enlargement optical system.
According to still another aspect of the present invention, an image display apparatus is provided with an image display element for displaying a two-dimensional image, an enlargement optical system for reflecting, as a first image, the image displayed on the image display element so as to project, with enlargement, the first image onto an observer's pupil while transmitting, as a second image, an image from an outside world so as to direct the second image to the observer's pupil, and a holographic element as described above included in the enlargement optical system
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Optical Systems 
