Function-conversion device for ground monocular telescope
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a function-conversion device for the ground monocular telescope and more specifically to a convenient and easy-to-operate function-conversion device for a ground monocular telescope operating on the erecting-prism principle of wherein a reticle removal/mounting, a visibility diaphragm, magnification change or other functions are integrated. 
     2. Description of the Prior Art 
     Conventionally, the ground monocular telescopes operating on the erecting-prism principle have been in extensive use, due to their ease of handling, brightness sufficient for observation purposes, and other advantages. They have normally found their applications in the observation of wild birds, shooting matches and other purposes, because of their reduced weight and ease of operation. 
     Such ground monocular telescopes operating on the erecting-prism principle have had difficulties in adjusting visibility and field of view in multiple stages, despite their peerless capabilities. 
     For instance, as is well known, a reticle is mounted in order to determine the distance to a particular object. In the case of the telescope under consideration, it would be impossible to mount a reticle only when it was necessary, and thus it had to be in a mounted state at all times. This resulted in the obstruction by the scales of the reticle to the view of the observer except while a distance was being measured. 
     These are shortcomings of an erecting-prism type ground monocular telescope which can result inevitably from its advantages. For this reason, in the conventional system, there was nothing which could be done for it but to make the visibility and field-of-view adjustment function exceedingly simple, because a reticle was not free to be mounted or removed, as well as the magnification adjustment could be done only in a single stage. 
     Accordingly, an erecting-prism type ground telescope incorporating multiple visibility and field-of-view adjustment functions, has been strongly desired. 
     With the above taken into account, the object of the present invention is to provide a convenient, and easy-to-handle function-conversion device for an erecting-prism type ground monocular telescope, which is designed to overcome the defects from which the conventional equipment has suffered, and to select appropriate levels of visibility and field-of-view. 
     SUMMARY OF THE INVENTION 
     In an erecting-prism type ground monocular telescope, a function-conversion device according to the present invention has a rotational plate so mounted as to be horizontally movable in the vicinity of the focal plane of an objective lens, with a plurality of windows being equipped with said rotational plate and with a reticle and/or a visibility diaphragm or a second objective lens being mounted onto said windows. 
     This equipments makes it possible to use a reticle for the observation of a distance only when it is required, and also makes it easier to change magnifications. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a conceptual drawing of one embodiment of the present invention. 
     FIG. 2 is a plan view of the rotational plate shown in FIG. 1. 
     FIG. 3 shows a conceptual drawings of another embodiment of the present invention. 
     FIG. 4 is a cross-sectional view of an essential portion of the present invention illustrating an example of the construction hereof. 
     FIG. 5 is a plan view of the rotational plate as indicated in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the above drawings, 1 and 2 each represent a prism, 3 an objective lens, 4 an ocular lens, 5 a rotational plate, 6 the center of rotation (rotation axis), 7 and 8 each designate a window, 9 a reticle, 10 a visibility diaphragm, 11 a turning ring, 12 a pin, 13 a rotational plate, 14 and 15 each designate a window, 16 a second objective lens, 17 a cover, 18 a turning ring, 19 a notch and 20 a notch. 
     Referring now in detail to the drawings, FIG. 1 shows the principle of the function-conversion device according to the preset invention. As indicated in FIG. 1, in an optical system comprising prisms 1 and 2, an objective lens 3 and an ocular lens 4, a rotational plate 5 capable of moving horizontally towards and away from the objective lens 3 is provided in the vicinity of the focal point (F) of the objective lens 3. The rotation axis or central point 6 of said rotational plate 5 is located at approximately one-half of the displacement of the rays of light emitting from said optical system(A). 
     The rotational plate 5 has windows 7 and 8 as in the case of FIG. 1. Said rotational plate 5 exhibits the cross section along I--I in FIG. 2. The window 7 is equipped with a reticle 9, and the window 8 with a visibility diaphragm 10. 
     Rotation of the rotational plate 5 can be accomplished by, for instance, causing a rotary ring (turning ring) 11 equipped with a pin 12 to rotate. 
     FIG. 3 shows an embodiment wherein a second objective lens 16 is provided so as to be aligned with either of the windows 14 and 15 of a rotational plate 13. In this case, the adjustment for the focal point (F) can be readily accomplished by means of a sliding mechanism of the ocular lens 4 and/or objective lens 3 such as by moving the ocular lens 4 toward and away from the plate 13. When said second objective lens 16 is adopted, a difference in focal point occurs, and accordingly, the rectilinear movement of said ocular lens 4 in the direction toward the said rotational plate 13 may be adjusted with a sliding mechanism such that the second objective lens 16 comes close to said ocular lens 4. 
     This arrangement permits adjustment of the difference in focal point. 
     The construction of a means which enables the rotational plate 5 to rotate as show in FIG. 1 is illustrated in FIG. 3, which is only one example of such an arrangement. 
     The rotational plate 5 turns around the central point 6. An ocular lens system 4 has a turning ring 18 mounted rotatably on a cover 17 so as to rotate above a turning axis. Said turning ring 18 has a pin 12, said pin 12 being inserted into semi-annular notch 19 in said cover, and also into a radially extending notch 20 in said rotational plate 5. 
     FIG. 5 shows said rotational plate 5 in the present embodiment. 
     In this example, the window 8 equipped with a visibility diaphragm 10 is mounted in the light path opposed to the prism. A pin 12 is provided with a turning ring 18, and the pin 12 is caused to move along the notch 20 of the rotational plate 5 in synchronization with the rotation of said turning ring 18 around the turning axis which is coincident with a central point(B). 
     To locate a window 7 on which a reticle 9 is mounted at the central point, said turning ring 18 is caused to rotate such that the pin 12 is moved through an angular displacement of about 90° about the turning axis B (angle α) and the pin 20 is located the left side of FIG. 5. The window 7 is thus rotated about 150° about the rotation axis 6 (Angle β). 
     It is, of course to be understood that the form of my invention herein shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to. 
     The conversion equipment of the present invention makes it is possible to integrate a reticle, a visibility diaphragm, magnification change and other functions, serving to improve the utility of an erecting-prism system as a ground monocular telescoping and achieve a multi-function and easy to handle telescope.