Focus detecting device

A focus detecting device comprising:

• (a) an objective lens;
• (b) first light splitting means for splitting a light flux from said objective lens symmetrically relative to the optical axis of the objective lens;
• (c) second light splitting means for splitting the light flux from said objective lens into a light flux portion from the neighbourhood of the optical axis of the objective lens and a light flux portion from outer parts of the objective lens;
• (d) an imaging lens which re-images an object's image formed on a prescribed image plane of said objective lens into a plurality of secondary images of the object on the basis of said plurality of light fluxes split through said first and second light splitting means;
• and
• (e) light receiving means for detecting relative positional relation of siad plurality of secondary images of the object re-imaged by said imaging lens.

A focus detecting device comprising:

• (a) an objective lens;
• (b) light splitting means for splitting a light flux from said objective lens into a light flux portion from the neighbourhood of the optical axis of the objective lens and a light flux portion from outer parts of the objective lens;
• (c) imaging means for re-imaging an object's image formed on a prescribed image plane of said objective lens into a plurality of secondary images of the object on the basis of light fluxes guided from said objective lens via said light splitting means, said imaging means being composed of a plurality of imaging lenses the optical axes of which differ from the optical axis of said objective lens;
• and
• (d) light receiving means for detecting relative positional relation of said plurality of secondary images of the object re-imaged by said imaging means.

A focus detecting device comprising:

• (a) an objective lens;
• (b) imaging means which re-images an object's image formed on a prescribed image plane of the objective lens into a plurality of secondary images of the object by splitting a light flux from the objective lens symmetrically relative to the optical axis of the objective lens;
• (c) light splitting means for splitting the light flux guided from said objective lens to said imaging means into a light flux portion from the neighbourhood of the optical axis of the objective lens and a light flux portion from outer parts of the objective lens;
• (d) optical path length differentiating means consisting of a first region for passing the light flux from the neighbourhood of the optical axis of the objective lens and a second region for passing the light flux from outer parts of the objective lens, said first and second regions differing in optical thickness, and said second region being arranged to have varied optical thickness when divided symmetrically relative to the optical axis of said objective lens;
• and
• (e) light receiving means consisting of a first light sensitive element which is arranged to detect a secondary image of the object re-imaged on the basis of the light flux passed through the first region of said optical path length differentiating means and a second light sensitive element which is arranged to detect a secondary image of the object re-imaged on the basis of the light flux passed through the second region of said optical path length differentiating means.