Abstract:
An optical adapter comprises an adapter body and a lens member. The lens member is a cylindrical lens having one or more curved surfaces, and has a function to extend an optical image in a horizontal direction. A taking lens and a viewfinder are arranged vertically, and the optical axes of the taking lens and the viewfinder coincide with each other in the horizontal direction. When the adapter body is attached to the front side of the lens-fitted photo film unit, the front surfaces of the taking lens and the viewfinder are covered with the lens member. The center of the lens member in the horizontal direction coincides with centers of the taking lens and the viewfinder in the horizontal direction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an optical adapter, and more particularly to an optical adapter for a camera having a cylindrical lens to form an image in which vertical and horizontal magnifications are different, and a lens-fitted photo film unit to which the optical adapter is attached.  
           [0003]    2. DESCRIPTION OF THE PRIOR ARTS  
           [0004]    In order to apply a visual effect in a photographed picture, it is known to attach an optical adapter to a front surface of a taking lens in photographing a human subject. For example, there is an optical adapter which makes the human subject look thinner or fatter than actual. Such optical adapter is disclosed in U.S. Pat. No. 6,072,636 and Japanese Patent Laid-Open Publication No. H11-64962, and so on. The optical adapter disclosed in these publications forms an image so as to differentiate vertical and horizontal magnifications of the human subject by using a cylindrical lens.  
           [0005]    In Japanese Patent Laid-Open Publication No. 2000-122233, the cylindrical lens as the optical adapter is provided in a lens-fitted photo film unit into which an unexposed photo film is pre-loaded. The optical adapter can differentiate the vertical and horizontal magnifications of the subject image in the photo film.  
           [0006]    In the optical adapter described in the above-mentioned publications, however, the taking lens is covered by the cylindrical lens, while a viewfinder is not. Accordingly, in the event of using a normal camera or a lens-fitted photo film unit except for a single-lens reflex camera, a photographer cannot confirm the change in the vertical and horizontal magnifications through the viewfinder. If the photographer takes a photograph without being aware that the optical adapter is attached to the camera, it is caused to make a printed photograph which is not intended by the photographer.  
           [0007]    In Japanese Patent Laid-Open Publication No. 2000-122233, the viewfinder is covered by the cylindrical lens. However, since the taking lens and the viewfinder are respectively covered by different cylindrical lenses. It is necessary to cover the taking lens and the viewfinder separately. Such operation is troublesome, and may cause a mistake.  
         SUMMARY OF THE INVENTION  
         [0008]    An object of the present invention is to provide an optical adapter capable of confirming by a simple operation, that photographing is performed in a state that the vertical and horizontal magnifications are different.  
           [0009]    In order to achieve the above object, an optical adapter of the present invention is attached to a camera having a taking lens and a viewfinder, and provided with a lens member constituted of a cylindrical lens, which covers the taking lens and the view finder.  
           [0010]    In the optical adapter, the lens member has a single curved surface. Optical axes of the taking lens and the viewfinder lens respectively pass through a center of the curved surface.  
           [0011]    In addition, the lens member has first and second curved surfaces which are curved in the same direction. The optical axis of the taking lens passes through a center of the first curved surface, while the optical axis of the viewfinder passes through a center of the second surface.  
           [0012]    According to the present invention, both the taking lens and the viewfinder are covered with the lens member from each front surface side, so that a photographer can take a photograph with confirming the respective changes of the vertical and horizontal magnifications of the photographed image through the viewfinder. Additionally, since the taking lens and the viewfinder are covered with only one lens member, the switching operation for the normal photographing is easy to perform so that an operation mistake can be prevented. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The above and other subjects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when read in association with the accompanying drawings, which are given by way of illustration only and thus are not limiting the present invention. In the drawings, like reference numerals designate like or corresponding parts throughout the several views, and wherein:  
         [0014]    [0014]FIG. 1 is an outline perspective view of an optical adapter of the present invention;  
         [0015]    [0015]FIGS. 2A and 2B are perspective views of a lens-fitted photo film unit to which the optical adapter is attached;  
         [0016]    [0016]FIG. 3 is a front view of the lens-fitted photo film unit;  
         [0017]    [0017]FIG. 4 is a sectional view of the optical adapter and a taking lens;  
         [0018]    [0018]FIG. 5 is a perspective view of a photographic optical system; and  
         [0019]    [0019]FIGS. 6A and 6B are explanatory views of an actual human subject and a photographed image; and  
         [0020]    [0020]FIGS. 7A, 7B, and  7 C are perspective views of other examples of a lens member of the optical adapter. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    In FIG. 1, an optical adapter  10  is constituted of an adapter body  11  and a lens member  12 . The lens member  12  is a cylindrical lens having a single convex surface (cylindrical surface) in a subject side. The combination of the cylindrical lens and a taking lens causes astigmatism, so that an optical subject image is extended in a certain direction.  
         [0022]    The adapter body  11  is provided with a pair of shafts  13   a  and  13   b , and engaging claws  14   a  and  14   b . A lens holding frame  15  is provided in a center of the adapter body  11 . The lens member  12  is attached to the lens holding frame  15 .  
         [0023]    In FIG. 2A, the optical adapter  10  is attached to a lens-fitted photo film unit  20  in a detachable manner. The lens-fitted photo film unit  20  has a unit body  21  and an outer label  22  for covering a center portion of the unit body  21 . A photo film  52  and a cartridge  53  (see FIG. 3) are pre-loaded in the unit body  21 , and a photographing mechanism including a shutter device is contained therein. A shutter button  23 , engaged holes  24   a  and  24   b , and so forth are provided in the top surface of the unit body  21 . The engaged holes  24   a  and  24   b  are respectively engaged with engaging claws  14   a  and  14   b  of the optical adapter  10 . A part of a winding dial  25  for winding the exposed photo film  52  is exposed from a rear surface of the unit body  21 .  
         [0024]    A taking lens  26 , a viewfinder  27 , and so forth are provided in a front surface of the unit body  21 . Further, there are adapter holding portions  29   a  and  29   b  for holding the shafts  13   a  and  13   b  in the lower part of the front surface of the unit body  21 . Thereby, the optical adapter  10  is attached to the lens-fitted photo film unit  20  in a rotatable manner around the shafts  13   a  and  13   b  between an open position shown in FIG. 2A and a locked position shown in FIG. 2B. In the locked position, the engaging claws  14  and  14   b  are engaged with the engaged holes  24   a  and  24   b  to hold the adapter  10  in front of the unit body  21 .  
         [0025]    As shown in FIGS. 3 and 4, when the optical adapter  10  is in the locked position, the taking lens  26  and the viewfinder  27 , which are arranged in a vertical direction, are covered with the lens member  12 . The position of an optical axis  50  of the taking lens  26  and the position of an optical axis  51  of the viewfinder  27  are designed so as to coincide with each other in a horizontal direction, which is the same as a film feeding direction to feed the photo film  52  in FIG. 3. The optical axis  50  of the taking lens  26  passes through the center of the lens member  12  in the horizontal direction, which means the center of the cylindrical surface with respect to the light refractive direction of the lens member  12  (the horizontal direction in this embodiment). Likewise, the optical axis  51  of the viewfinder  27  passes through the center of the cylindrical surface of the lens member  12  in the horizontal direction. Next, the operation of the above embodiment is explained. The optical adapter  10  attached to the lens-fitted photo film unit  20 , is movable between the open position and the locked position. A photographer rotates the optical adapter  10  to the open position to carry out normal photography without using the lens member  12 . In the normal photography, the optical adapter  10  may be detached from the lens-fitted photo film unit  20 .  
         [0026]    In photographing a subject with different vertical and horizontal magnifications, the photographer moves the optical adapter  10  to the locked position. The front side of the taking lens  26  and the viewfinder  27  are covered by single lens member  12 .  
         [0027]    The photographer brings the eye close to the viewfinder, and then observes a subject image through the viewfinder  27  for framing. Thereafter, if the photographer pushes down the shutter button  23 , the shutter release is performed to expose the subject image to the photo film  52 .  
         [0028]    As shown in FIG. 5, subject light is incident on the taking lens  26  and the viewfinder  27  through the lens member  12 . In the photography optical system composed of the lens member  12  and the taking lens  26 , the focal length in the horizontal direction shown in a dashed line A is longer than the focal length in the vertical direction shown in a dashed line B. Thus, as shown in FIG. 6A, the optical image of the actual subject  31  becomes enlarged in the horizontal direction to form a photographic image  32  in a photographic area  30 . Accordingly, the photographed image becomes fatter than the actual subject  31 . In the viewfinder optical system composed of the lens member  12  and the viewfinder  27 , the optical image of the subject is also enlarged in the horizontal direction as shown in FIG. 6A. Thereby, when the lens-fitted photo film unit  20  is held in a horizontal position shown in FIG. 3 in photographing, the photographer can take a photograph after confirming the photographic image  32  through the viewfinder  27 .  
         [0029]    In a vertical position where the lens-fitted photo film unit  20  is turned by almost 90 degree from the position in FIG. 3, the optical image of the subject  31  is enlarged in the vertical direction to form a photographic image  34 . Consequently, the subject  31  is photographed so as to look thinner than actual.  
         [0030]    If the photographer wants to take a photograph so as to make the subject  31  look fatter than actual, the lens-fitted photo film unit  20  is held in the horizontal position in photography. Meanwhile, if the photographer wants to take a photograph so as to make the subject  31  look thinner than actual, photography is carried out in the vertical position.  
         [0031]    Next, the variations of the lens member  12  of the optical adapter  10  are explained. In FIG. 7A, a lens member  40  is a cylindrical lens which has a single concave surface in the horizontal direction C in the Figure. On the contrary to the lens member  12  in the above embodiment, in the photography optical system composed of the lens member  40  and the taking lens  26 , since the focal length in the horizontal direction shown by a dashed line C is shorter than the focal length in the vertical direction shown in a dashed line D, the optical subject image is compressed in the horizontal direction. Consequently, the subject  31  is photographed so as to look thinner than actual.  
         [0032]    If the photographer wants to take a photograph so as to make the subject  31  look thinner than actual with the lens member  40 , the lens-fitted photo film unit is held in the horizontal position. On the other hand, if the photographer wants to take a photograph so as to make the subject  31  look fatter than actual, photography is carried out in the vertical position.  
         [0033]    The lens members  12  and  40  are respectively constituted of a cylindrical lens having a single cylindrical surface. Instead, as a lens member  41  shown in FIG. 7B, two cylindrical lenses  42  and  43  having cylindrical surfaces in the horizontal direction in the Figure may be connected to a connection part  44 . Two lenses  42  and  43  are molded integrally so as to coincide the optical axis in the horizontal direction with each other, and therefore, the positional accuracy is extremely high. The optical function of the lens member  41  is the same as that of the lens member  12 .  
         [0034]    In the example shown in FIG. 7C, a lens member  45  has two cylindrical lenses  46  and  47  that are integrally molded with a connection part  48 . In this case, the focal length in the vertical direction shown by a dashed line F is longer than the focal length in the horizontal direction shown by a dashed line E, so that the optical subject image is vertically enlarged. Accordingly, the subject  31  is photographed so as to look thinner than actual when the lens-fitted photo film unit  20  with the lens member  45  is held in the horizontal position. On the other hand, when the lens-fitted photo film unit  20  is held in the vertical position, it is possible to photograph so as to make the subject  31  look fatter than actual.  
         [0035]    In the above embodiments, the optical adapter is applied to the lens-fitted photo film unit. The optical adapter of the present invention is also applicable to a camera.  
         [0036]    Although the present invention has been fully described by the way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein.