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Head-mounted type image display system

  • US 5,917,460 A
  • Filed: 07/05/1995
  • Issued: 06/29/1999
  • Est. Priority Date: 07/06/1994
  • Status: Expired due to Fees
First Claim
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1. A head-mounted type image display system comprising:

  • a head-mounted type image display apparatus and a mounting means for mounting said head-mounted type image display apparatus on a head of a user, said head-mounted type image display apparatus having first and second image display devices displaying first and second images, respectively, and first and second projection optical systems projecting said first and second images displayed on said first and second image display devices onto right and left retinas of a user as virtual images, respectively;

    a back and forth movement detecting means for producing a displacement signal representing a direction and an amount of back and forth movement of a user'"'"'s head; and

    a virtual image moving means for responding to said displacement signal to move the virtual images in an opposite direction to the direction of said movement of the user'"'"'s head;

    wherein said first and second projection optical systems are fixed to said head-mounted type image display apparatus such that positions of exit pupils of the projection optical systems are not changed, said virtual image moving means comprises an image display device moving means for moving the first and second image display devices toward the projection optical systems when the user'"'"'s head is moved forwardly and for moving the first and second image display devices away from the projection optical systems when the user'"'"'s head is moved backwardly, and an image enlarging and reducing means for enlarging the first and second images displayed on the first and second image display devices, respectively, when the user'"'"'s head is moved forwardly and reducing the images displayed on the first and second image display devices, respectively, when the user'"'"'s head is moved backwardly, when a distance between a display plane of said first and second image display devices and a principal point of the projection optical systems on the side of the image display devices in a standard condition is L, a distance between the virtual images and the principal point of the projection optical systems on the side of the user is L'"'"', a focal length of the projection optical systems is f and an amount of the forward movement of the user'"'"'s head is Δ

    x, said first and second image display devices are moved by an amount Δ

    X which satisfies the following condition;

    L-f(L'"'"'-0.8Δ

    x)/(f+L'"'"'-0.8Δ

    x)<

    Δ

    X<

    L-f(L'"'"'-1.2Δ

    x)/(f+L'"'"'-1.2Δ

    x) and the images displayed on the first and second image display devices are enlarged or reduced by a value within a range from 0.8(L'"'"'(L-Δ

    X)/L(L'"'"'-Δ

    x)) to 1.2(L'"'"'(L-Δ

    X)/(L(L'"'"'-Δ

    x)) so as to compensate for a variation in a projecting magnification due to the movement of the displayed images.

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