Optical element and compound display apparatus using the same

Abstract

The present invention has as its object to provide a thin type optical system which enables both of image information displayed on display means such as a liquid crystal display to be observed and image information of which image is substantially equal to the image observed via therethrough and which is taken by image pickup means and a compound display apparatus using such optical system. For this object, the optical element according to the present invention is an optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, and is characterized in that the meridional section composite power of the optical element is negative.

What is claimed is:  
     
         1 . An optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of said plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, characterized in that the meridional section composite power of said optical element is negative.  
     
     
         2 . An optical element according to  claim 1 , characterized in that at least one of said plurality of eccentric reflecting surfaces is a rotation-asymmetrical surface.  
     
     
         3 . An optical element according to  claim 2 , characterized in that said emergence surface is a rotation asymmetrical surface.  
     
     
         4 . An optical element according to  claim 1 , characterized in that all of said incidence surface, said emergence surface and said plurality of eccentric reflecting surfaces are rotation-asymmetrical surfaces.  
     
     
         5 . An optical element according to  claim 3  or  4 , characterized in that design is made such that the local meridional section focal length f ypout  and local sagittal section focal length f xpout  of said emergence surface and the meridional section composite focal length f yp  and sagittal section composite focal length f xp  of said optical element satisfy  
       |f yp /f ypout |<2  (1) |f xp /f xpout   |< 2     (2)  
     
     
         6 . An optical element according to any one of  claims 1  to  4 , characterized in that said emergence surface has negative power.  
     
     
         7 . An optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of said plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, characterized in that at least one of said plurality of eccentric reflecting surfaces is a rotation-asymmetrical surface, and design is made such that the local meridional section focal length f ypout  and local sagittal section focal length f xpout  of said emergence surface and the meridional section composite focal length f yp  and sagittal section composite focal length f xp  of said optical element satisfy  
       |f yp /f ypout |<2  (1′) |f xp /f xpout |<2  (2′)  
     
     
         8 . A compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, characterized in that all of the optical axis of the rotation-symmetrical surface of said rotation-asymmetrical lens and the optical axes of said rotation-symmetrical lenses are substantially coincident with one another.  
     
     
         9 . A compound lens unit according to  claim 8 , characterized in that design is made such that the local meridional section focal length f yl  and local sagittal section focal length f xl  of said rotation-asymmetrical surface and the meridional section composite focal length f yg  and sagittal section composite focal length f xg  of said compound lens unit satisfy  
       |f yg /f yl |<1  (3) |f xg /f xl |<1.  (4)  
     
     
         10 . An image pickup optical system having a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of said plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, and the meridional section composite power is negative, a stop, and a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, all of the optical axis of the rotation-symmetrical surface of said rotation-asymmetrical lens and the optical axes of said rotation-symmetrical lenses being substantially coincident with one another, characterized in that design is made such that light from the external world is caused to be incident from the incidence surface of said first optical element, is reflected by said plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from said emergence surface, and is passed through said stop, and thereafter is refracted by said compound lens unit and is imaged on an image pickup element.  
     
     
         11 . An image pickup optical system according to  claim 10 , characterized in that design is made such that when the meridional section composite focal length of the entire image pickup optical system is defined as fy and the sagittal section composite focal length thereof is defined as f x  and the meridional section composite focal length of said first optical element is defined as f yp  and the sagittal section composite focal length thereof is defined as f xp ,  
       −1<f y /f yp <0  (5) −1<f x /f xp <0  (6)  
       are satisfied.  
     
     
         12 . An image pickup optical system according to  claim 10 , characterized in that deflecting means for bending the optical path in a direction differing from the direction in which the optical path of said first optical element is folded is provided between said first optical element and said stop or between said stop and said compound lens unit.  
     
     
         13 . An image pickup optical system having a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of said plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, and at least one of said plurality of eccentric reflecting surfaces is a rotation-asymmetrical surface, and design is made such that the local meridional section focal length f ypout  and local sagittal section focal length f xpout  of said emergence surface and meridional section composite focal length f yp  and sagittal section composite focal length f xp  of said first optical element satisfy the following conditional expressions:  
       |f yp /f ypout |<2  (1″) |f xp /f xpout |<2,  (2″)  a stop, and a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, all of the optical axis of the rotation-symmetrical surface of said rotation-asymmetrical lens and the optical axes of said rotation-symmetrical lenses being substantially coincident with one another, characterized in that design is made such that light from the external world is caused to be incident from the incidence surface of said first optical element and is reflected by said plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from said emergence surface, and is passed through said stop, and thereafter is refracted by said compound lens unit and is imaged on an image pickup element.    
     
     
         14 . A compound display apparatus having an image pickup optical system according to  claim 10 , an image pickup element, display means and a second optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a display reference ray Rd and having power, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, and has said display optical system being designed to direct the light from the display means to an observer by the use of said second optical element and presenting the enlarged image of an image on said display means, one of the eccentric reflecting surfaces of said first optical element and one of the eccentric reflecting surfaces of said second optical element using the front and back surfaces of the same shape of an optical path separating surface, said optical path separating surface being a half-transmitting reflecting surface, and being caused to function as a see-through optical system for causing light from the external world to be incident from the incidence surface of said first optical element, be transmitted through said optical path separating surface, to be emerged from the emergence surface of said second optical element and to be directed the light to an observer, characterized in that when a see-through reference ray passing through the center of the external world and the center of the exit pupil of said see-through optical system is defined as Rs, said display reference ray Rd and said see-through reference ray Rs substantially coincide with the optical axis of the eyeball, and each of said see-through reference ray and the reference ray Ri of said image pickup optical system is substantially coincident with the optical axis of the external world.  
     
     
         15 . A compound display apparatus having an image pickup optical system according to  claim 13 , an image pickup element, display means and a second optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a display reference ray Rd and having power, wherein a beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from said emergence surface, and has said display optical system being designed to direct the light from the display means to an observer by the use of said second optical element and present the enlarged image of an image on said display means, one of the eccentric reflecting surfaces of said first optical element and one of the eccentric reflecting surfaces of said second optical element using the front and back surfaces of the same shape of an optical path separating surface, said optical path separating surface being a half-transmitting reflecting surface, and being caused to function as a see-through optical system for causing light from the external world to be incident from the incidence surface of said first optical element, be transmitted through said optical path separating surface, to be emerged from the emergence surface of said second optical element to be directed to an observer, characterized in that when a see-through reference ray passing through the center of the external world and the center of the exit pupil of said see-through optical system is defined as Rs, said display reference ray Rd and said see-through reference ray Rs substantially coincide with the optical axis of the eyeball, and each of said see-through reference ray and the reference ray Ri of said image pickup optical system is substantially coincident with the optical axis of the external world.  
     
     
         16 . A compound display apparatus according to  claim 14  or  15 , characterized in that design is made such that when the distance from the position of the evolved entrance pupil when the entrance pupil of said image pickup optical system is evolved on the visual axis to the position of the exit pupil of said display optical system is defined as D pp  and the distance from the emergence surface of said display optical system to the exit pupil of said display optical system is defined as er,  
       0.25<D pp /er<8.0  (7)  
       is satisfied.  
     
     
         17 . A compound display apparatus having a display optical system for directing a beam from display means displaying image information thereon to an observer's eyeball, and an image pickup optical system for imaging a beam from the external world on an image pickup element, wherein the eyeball optical axis of the beam incident on the observer's eyeball of said display optical system or a virtual eyeball optical axis extended from the eyeball optical axis and the external world optical axis of a beam incident from the external world of said image pickup optical system are made substantially coincident with each other by optical path separating means provided in said optical path, characterized in that said image pickup optical system has a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of said plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein the beam incident from said incidence surface is reflected by said plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from the emergence surface, and meridional section composite power is negative.  
     
     
         18 . A compound display apparatus according to  claim 17 , characterized in that said image pickup optical system has a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, wherein all of the optical axis of the rotation-symmetrical surface of said rotation-asymmetrical lens and the optical axes of said rotation-symmetrical lenses are substantially coincident with one another, and the beam from the external world is passed through said first optical element, and thereafter is directed onto said image pickup element by said compound lens unit.  
     
     
         19 . A compound display apparatus according to  claim 18 , characterized in that design is made such that the local meridional section focal length f ypout  and local sagittal section focal length f xpout  of the emergence surface of said first optical element and the meridional section composite focal length f yp  and sagittal section composite focal length f xp  of said first optical element satisfy  
       |f yp /f ypout <2  (1) |f xp /f xpout |<2.  (2)  
     
     
         20 . A compound display apparatus according to  claim 19 , characterized in that design is made such that the local meridional section focal length f yl  and local sagittal section focal length f xl  of the rotation-asymmetrical surface of said compound lens unit and the meridional section composite focal length f yg  and sagittal section composite focal length f xg  of said compound lens unit satisfy  
       |f yg /f yl |<1  (3) |f xy /f xl |<1.  
     
     
         21 . A compound display apparatus according to  claim 20 , characterized in that design is made such that when the meridional section composite focal length of the entire image pickup optical system is defined as f y  and the sagittal section composite focal length thereof is defined as f x  and the meridional section composite focal length of said first optical element is defined as f yp  and the sagittal section composite focal length thereof is defined as f xp ,  
       −1<f y /f yp <0  (5) −1<f x /f xp <0  (6)  
       are satisfied.  
     
     
         22 . A compound display apparatus according to  claim 21 , characterized in that design is made such that when the distance from the position of the evolved entrance pupil when the entrance pupil of said image pickup optical system is evolved on the visual axis to the position of the exit pupil of said display optical system is defined as D pp  and the distance from the emergence surface of said display optical system to the exit pupil of said display optical system is defined as er,  
       0.25<D pp /er<8.0  (7)  
       is satisfied.