Mark indicating device for optical apparatus

DETAILED DESCRIPTION What we claim is: 1.
In an optical apparatus having objective lens means for forming an image of an object, a device for indicating a mark and view-finder means for viewing said image of object and said mark, wherein said device comprises: a relief hologram comprising a plurality of semi-reflective oblique faces periodically arranged to form a diffraction lattice entirely embedded in a transparent body, said hologram being arranged in an optical path of said optical apparatus; and illuminating means arranged outside said optical path to illuminate said hologram for obtaining a reconstructed image of said mark in overlapping manner with said image of object.
2.
In an optical apparatus having objective lens means for forming an image of an object, a device for indicating a mark, and view-finder means for viewing said image of the object and said mark, wherein said device comprises: a first optical transparent member having a relief hologram of said mark thereon; a semi-reflective layer disposed on said relief hologram to define a semi-reflective relief structure; second optical transparent member connected to said semi-reflective layer to completely cover said semi-reflective relief structure; and illuminating means located outside said optical path to illuminate said semi-reflective relief structure so that a reconstructed image of said mark is obtained.
3.
A device according to the claim 2, wherein said illuminating means is positioned opposite to said view-finder means with respect to the face having said hologram.
4.
A device according to the claim 3, wherein said face having said hologram is provided with a relief diffraction lattice structure composed of periodically repeating triangle-sectioned unit structures each formed by two oblique faces, whereby diffracted light formed by one of said oblique faces having larger oblique angle to said face having said hologram is introduced into the optical path of said view-finder means.
5.
A device according to the claim 2, wherein said first optical transparent member and said second optical transparent member have substantially the same refractive indexes