Abstract:
An improved photographic still pocket camera, where the film is inserted in a cassette provided with a feed part or spool and a take-up part or spool, these parts or spools connected by a film guide ledge. A zoom lens is mounted inside the camera, with the picture-taking beam path of the zoom lens located essentially parallel to the film plane and hence transverse to the direction of picture taking. The movable lens elements of the zoom lens are also movable parallel to the film plane.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     Applicants claim priority under 35 U.S.C. 119 for application P 24 45 289.9, filed Sept. 21, 1974, in the Federal Republic of Germany. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a still pocket camera with cassette film insertion, comprising a feed and a take-up spool or part, both connected by a film guide step. 
     The cameras under consideration in the present application make use of films of lesser width than for the conventional 35 mm cinematographic or ordinary film, and generally are termed &#34;pocket cameras&#34; in the trade. They are of relatively small dimensions and of flat design so as to conveniently fit into the pockets of clothing apparel. 
     Such cameras are known as direct viewing types and also as mirror reflex cameras. It is further known to provide them with interchangeable objectives in the sense that several attachment objectives may be placed in front of a basic one, pictures therefore being taken if desired with lenses of varying focal lengths. One encounters, however, the drawback of having to connect the attachment objectives to the camera in such a manner that they protrude from the housing. Therefore, the camera loses that compactness and handling facility which do characterize it with respect to others. Hence one may no longer speak of a pocket camera. 
     SUMMARY OF THE INVENTION 
     Having in mind the limitations of the prior art, it is an object of the present invention to endow a pocket camera with the capability of taking pictures of various fields of view without thereby enlarging the external camera dimensions. 
     This object is achieved in that a zoom lens is mounted in the camera, the picture light beam being essentially parallel to the film plane and hence transverse to the direction the camera is pointing at, and wherein the movable lens elements may also be moved parallel to the film plane. 
     In this manner it becomes feasible within certain limits to take pictures at varying field-of-view angles without thereby having to enlarge the camera on account of interchangeable lenses or attachment lenses. Furthermore, the use of zoom lenses brings with it the inherent advantage of the angle of view being continuously variable, in contrast to the step-wise variation of interchangeable lenses. 
     Though basically it is possible to design a camera with a zoom lens according to the present invention as a direct viewing camera, the viewer then requiring the same or a similar zoom lens, such a design of the objective however primarily is suited for a mirror reflex camera in which the picture beam and the viewer beam coincide at least partly. Accordingly to the present invention it is proposed to so mount the zoom lens of such a camera that at least part of the viewer beam also is parallel to the film plane. 
     The imaging or focusing optics of the zoom lens may be designed as pure lens element optics, or the optics may also comprise one or more mirror systems. Especially a splitting hexahedron or prism with a polarizing interference layer is recommended as a mirror system, two adjacent hexahedron surfaces each being occupied by one mirror lens, there being insertion of one λ/4 foil or plate in each case. 
     One of the splitting prisms is mounted on a straight line in front of the film window and may be rotated by 90° between two end positions. In one position the prism reflects the rays from the objective to the film (picture taking position), and in the other, it reflects these rays into the ocular (viewer position). In order to indicate focus of the objective for the given object, an indicator such as ground glass, a prismatic grating and the like is mounted in one intermediate focal plane. This indicator must be removed from the path of the rays when the picture is being taken. It is proposed therefore to so connect it with the splitter prism that simultaneously with the rotation of that prism into the picture taking position, the indicator is automatically removed from the beam path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics of the present invention are made obvious by the drawings, which represent several embodiments, wherein: 
     FIG. 1 is a schematic view of a mirror-reflex pocket camera with zoom lens for narrow film, as a first embodiment with a direct viewer beam parallel to the beam path for taking pictures; 
     FIG. 2 is a schematic view of a mirror reflex pocket camera for narrow film, with zoom lens, as a second embodiment, the zoom lens optics consisting solely of lens elements; 
     FIG. 3 is a mirror reflex pocket camera for narrow film, with zoom lens, as a third embodiment, wherein the zoom optics comprises two mirror lenses; and 
     FIG. 4 shows the zoom inverting optics in the form of distance systems. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The schematically shown camera housing 1 of FIG. 1 receives film loaded cassette 2. The front element of the objective is designated by 3. The picture taking beam passes along optical axis 18 through element 3, through a 90° deflecting prism 5 of the zoom part of the objective, through an element 5a and a further 90° deflecting prism 5b to a splitting prism 6 in front of cassette 2. Splitting prism 6 splits viewer beam 7 passing through several lens elements 8 - 11 and through a further reflex mirror 12 to ocular 13. 
     Again the zoom part of the objective is indicated merely in schematic form; it consists of two lens element groups 14 and 15 which may be shifted along the optic axis. Examples of the lens element groups 14 and 15 and the means for shifting are disclosed in U.S. Pat. No 3,876,290. 
     A ground glass grating 16 is provided to assess focus. Focusing itself is implemented by shifting lens element 5a parallel to the film plane. 
     The camera shutter is designated by 17 and is located in front of cassette 2. 
     Even though the components are shown only in schematic manner for the sake of simplification, the concept of the invention is clearly recognizable; the zoom objective is mounted inside the camera housing at such a location that both the picture taking beam and the viewer beam essentially are parallel to the plane of the film and furthermore, the movable members of the zoom optics may also be displaced parallel to that film plane. 
     This concept of the present invention is also realized in the embodiment of FIG. 2. Again the camera housing and the film cassette are respectively designated by 1 and 2. The imaging part of the objective consists solely of lens element optics, group 21, namely elements 21a, 21b and 21c, forming the group of front elements. The beam for picture taking and viewing, 22, passes through a reflex prism 23 and the zoom part of optics 24 and 25 to a reflex mirror 26. Reflex mirror 26 is fully reflecting and is pivotable by 90° into two end positions. For the position shown in the figure, the rays from the object are guided through a set of lens elements 27, namely elements 27a, 27b and 27c, on either side of shutter 28 to film cassette 2. This is the picture taking position of the mirror. On the other hand, the position shown by dashed lines is that of observation, in which the rays are reflected to ocular 28a. 
     Objective focusing may be performed, for instance by adjusting the group 21 of front lens elements, as disclosed in U.S. Pat. No. 3,850,507. A diffraction grating 29 is mounted in an intermediate focus plane of the zoom part for focusing, which may be used for that purpose. This grating is mechanically connected with reflex mirror 26 so that it is removed every time from the path of rays when mirror 26 is pivoted from observation position into picture taking position. 
     Because of the extensive combination of the beams for viewing and picture taking, the required size of the camera is significantly less than in the embodiment of FIG. 1. 
     FIG. 3 shows an embodiment with essentially the same component arrangement. Here again the viewing and picture taking beams are extensively combined. However, the imaging optics no longer consist solely of refracting lens elements, rather mirror lenses also are employed. 
     Again the camera housing and film cassette are respectively designated by 1 and 2. The rays from the object first are incident through the front lens element 31 of the objective on a double splitting prism 32 where they are fully reflected and then through the zoom part 33, 34 of the objective they reach a second splitting mirror 35, and finally through further sets of lens elements 36, namely elements 36a, 36b and 36c, and 37, namely 37a and 37b, and shutter 38 they arrive at the film. 
     The design of splitting prisms 32 and 35 is known from German PS No. 1,961,128. They are provided with a polarizing splitting layer 32a and with one mirror lens 39 at each of two adjacent prism surfaces. One quarter wave plate 40 each is mounted between both prism surfaces and mirror lenses. Depending on the polarization, the polarizing splitting layer will reflect or transmit one part of the light, which then is reflected in the mirror lenses and rotated by 90° in their polarization plane by the quarter wave plates, so that upon the new incidence of the rays on splitting layer 32a, the originally reflected part of the rays now is transmitted whereas the originally transmitted part now is reflected. 
     The second splitting prism 35 also may rotate and may be switched from one to another of two end positions. In the position shown in the figure, the rays are reflected to the film (picture taking position), while they are deflected to ocular 42 in the other. 
     Again a grating 41 is provided for properly focusing the objective. As in the embodiment of FIG. 2, this grating also must be removed from the path of the beam when a picture is being taken. In this case, too, it is mechanically connected with rotating splitting prism 35 so that it is always removed from the beam path when splitting prism 35 is rotated into the picture taking position. 
     Using splitting prism 35 together with the mirror lens provides a relatively large space in front of lens element 31. This space is designed as a backlight stop in conformity with the invention and may be covered by means of flap 44 pivotably linked to the camera housing. 
     FIG. 4 illustrates the design of the zoom inverting optics as telephoto lens systems, comprising elements 45a- 45 e, where elements 45e and 45a are adjustable and coupled to each other.