Binocular telescope with internal focusing

Disclosed is a binocular telescope with internal focusing, comprising two telescope tubes, each having an ocular end and an objective end; a double joint bridge connecting the two telescope tubes; a central focusing element rotatably connected to the bridge; an internal focusing mechanism located in at least a first of the telescope tubes and including a first focusing lens axially movable within the first tube; a mechanism for transforming rotational movement of the central focusing element into axial adjustment of the focusing lens; and a mechanism including an annular bushing rotatably mounted near the objective end of the first telescope tube for independently varying the axial position of the first focusing lens, in order to make diopter focusing adjustments.

BACKGROUND OF THE INVENTION 
The present invention relates to a binocular telescope with internal 
focusing, which is equipped with a hollow, double joint bridge which 
connects the two tubes. The bridge includes a spindle of a focusing 
element and control elements between the focusing element and the focusing 
means of the telescope, with the latter being housed in sleeves within the 
tubes. 
Binocular telescopes with internal focusing of this type are generally 
known. Thus, German DE-OS No. 24 24 792 describes a binocular telescope 
having a central focusing element which, upon actuation for the purpose of 
focusing, rotates a spindle provided with threads. The spindle in turn 
moves a stirrup resting under tension against it, and the ends of the 
stirrup are coupled with transmission rods. These rods cooperate with the 
focusing elements, with which they are drivingly interconnected. The 
adjustment of only one optical system to equalize visual differences 
between the eyes of a user, the so-called diopter focusing adjustment, is 
not described in this prior art arrangement. It obviously takes place in 
the conventional manner, by rotation of a ring located in the ocular, 
which for the purpose of this adjustment requires special adjusting means, 
such as worm drives or the like. Because the actual sharp focusing of the 
binocular telescope is effected by means of an adjusting knob located 
centrally between the two tubes, whereas the diopter focusing adjustment 
to equalize differences in visual resolution is accomplished by an ocular 
ring, actual handling of the binoculars becomes cumbersome. In particular, 
in the case of persons wearing eyeglasses, touching and thus soiling of 
the glasses by the fingers due to ocular adjustments frequently cannot be 
prevented. Furthermore, under certain conditions the presence of a drive 
on the side of the eyepiece may have detrimental effects on the size and 
configuration of the binoculars. 
A binocular telescope is known from German Pat. No. 22 33 055, in which 
focusing is accomplished by a focusing lens arranged between the ocular 
and the objective, which is held in an axially displaceable mounting. No 
diopter focusing adjustment is possible with this telescope. 
Another double telescope with internal focusing is described in German 
DE-OS No. 23 65 652, in which an ocular lens system is axially 
displaceable forward and backward for the equalization of visual 
resolution. During rotation of an external tube of the ocular system of 
lenses, the distance between the external ocular lens and the inner lens 
system, and thus the magnification of the image, is not altered and the 
quality of the image not affected. 
Aside from the fact that there is no longer any genuine internal focusing 
present in this arrangement, the danger of soiling a user's eyeglasses is 
again present as the result of the diopter focusing adjustment on the 
ocular side. Furthermore, with the larger eyepiece lenses of telescopes 
designed for the wearers of eyeglasses, there is frequently not enough 
space left for the installation of a worm drive on the ocular side. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
binocular telescope of the above-described type. 
It is a particular object of the invention to provide an improved binocular 
telescope having improved handling capabilities in regard to diopter 
focusing adjustments, especially in the case of observation through 
eyeglasses, and also one which is equipped with genuine internal focusing. 
In accomplishing the foregoing objects, there has been provided according 
to the present invention a binocular telescope with internal focusing 
comprising two telescope tubes, each having an ocular end and an objective 
end; a double joint bridge connecting the two telescope tubes; a central 
focusing element rotatably connected to the bridge; means, located in at 
least a first of the telescope tubes and including a first focusing lens 
axially movable within the first tube, for internally focusing the 
telescope; means for transforming rotational movement of the central 
focusing element into axial adjustment of the focusing lens; and means, 
including an annular bushing rotatably mounted near the objective end of 
the first telescope tube, for independently varying the axial position of 
the first lens, in order to make diopter focusing adjustments. 
Preferably, the internal focusing means includes a first sleeve axially 
movable inside of the first telescope tube for holding the first focusing 
lens, and the movement transforming means comprises a threaded spindle 
rotatable with the central focusing element, a stirrup member having a 
threaded portion resiliently biased against the threaded spindle and at 
least a first arm, and a first axially movable control element engaged by 
the first stirrup arm and operatively engaging the first sleeve. In a 
preferred form of the diopter focusing means, the first sleeve includes a 
helical groove in the outer surface thereof and the control element 
engages the first sleeve in this groove, and the first sleeve further 
includes a recess extending in a direction parallel to the axis of the 
first telescope tube and the annular bushing includes a pin member on its 
inner surface engaging in the recess. Thus, rotation of the bushing causes 
rotation of the first sleeve to independently vary the axial position of 
the first focusing lens. 
Further objects, features and advantages of the present invention will 
become apparent from the detailed description of preferred embodiments 
which follows when considered together with the attached figure of drawing 
.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
According to the invention, means are provided for changing the spatial 
position of the focusing means in at least one of the tubes. These 
changing means are actuated by the rotation of an annular bushing mounted 
on the objective side on this tube. A particularly simple and cost 
effective solution is obtained by equipping one of the internal sleeves 
holding the focusing lens with a helical groove to be engaged by one of 
the control elements actuated by the central focusing element and by 
providing the sleeve with a limited recess defined in the direction 
parallel to the axis. The annular bushing is rotatably mounted on the 
objective side of the tube housing of said internal sleeve and is provided 
with a driving pin cooperating at least approximately without clearance 
with said recess. 
It may be of advantage from a manufacturing standpoint to provide both 
internal sleeves with a helical groove, to be engaged by each of the 
control elements of the central focusing element and to provide two 
annular bushings, one on each tube. This will facilitate the setting of 
the focusing lenses in a mutually aligned initial position. By final 
mounting, therefore, only one of the annular sleeves needs to be 
positioned. 
Further details may be found in the following description of a preferred 
embodiment of a binocular telescope schematically represented in the 
drawing. 
The binocular telescope 10 consists essentially of two tubes 11, 12, 
hingedly interconnected by means of a hollow, double joint bridge 13. The 
bridge 13 is closed with a cover 14, so that only a knurled knob 16 of a 
central focusing element 17 protrudes outwardly for focusing, while a 
spindle 18 is located inside the bridge 13. The spindle is mounted 
rotatably on the end surfaces 19, 20. The knurled knob 16 is located in a 
center recess 21 of the double joint bridge 13, whereby a straight line is 
created between its upper end surface and the upper edge of the upwardly 
drawn parts 22, 23 of the front surface. The cover 14 is also recessed, so 
that the knurled knob 16 protrudes slightly beyond the external surface of 
the cover 14 and is readily manipulated. 
A cross stirrup 24 resiliently, i.e., tensionally engages with the spindle 
18, wherein a threaded segment 25, interrupted in its center, serves as 
the means to engage the spindle 18. This insures a tilt-free construction. 
The rotation of the spindle 18 displaces the cross stirrup 24 upwardly or 
downwardly (in the plane of the drawing). Its ends engage two control 
elements 26, 27, which are equipped with annular recesses 28, 29 for 
driving purposes. The cross stirrup 24 is resiliently formed and is 
pretensioned, in order to insure the transfer of motion without play. By 
means of the contact of the cross stirrup 24 and its spring action, 
potential manufacturing tolerances of the double joint bridge 13 and of 
the transfer elements may be absorbed. 
The rod shaped control elements 26, 27 are mounted respectively in the 
bores 30, 31, with axes 32, 33, of the double joint bridge 13 in an 
axially displaceable manner. It should be understood that the mounting 
arrangements to be described hereinbelow for the control elements are 
identical in the two tubes 11, 12. The axes 32, 33 of the bores 30, 31 are 
coincidental with those of the double joint bridge 13, which have 
mountings formed again identically for the left and the right tube, on the 
ocular side by a ball 34 with bearing sockets 35, 36 and on the objective 
side by ring 37 with bearing shoulders 38, 39. 
The control element penetrates the ring 37. It is bent at a right angle in 
its lower part and continues through an orifice 40 into a protruding, 
lower joint support 41. The orifice 40 is designed--at least in the 
vicinity of the tube--as a guide 49 for the control element 26, so that, 
while the latter remains axially displaceable, it cannot, however, be 
rotated. The bearing socket 35 and the bearing shoulder 38 are located 
within the double joint bridge 13, while the bearing socket 36 and the 
bearing shoulder 37 are arranged in the lower joint support 41 and in an 
upper joint support 42. 
With its bent, horizontal end, the control element 26 engages a helical 
groove 43 of a sleeve 44 axially displaceable in the tube 11 and carrying 
a focusing lens 45. The sleeve 44 has a limited recess 46 extending in a 
direction parallel to the axis. A driving pin 47 engages approximately 
without play the recess 46, and the driving pin is provided on the inner 
side of an annular bushing 48 rotatably mounted on the tube 11. 
The mode of functioning of the focusing device is as follows: for the 
central focusing adjustment, the knurled knob 16 of the central focusing 
element 17 is actuated, which thereby rotates the spindle 18. By means of 
the threading of the spindle, movement is transferred to the cross stirrup 
24 which abuts with its threaded segment 25 under tension against the 
spindle 18. Because the ends of the cross stirrup 24 engage the annular 
recesses 28, 29 of the control elements 26, 27, the latter are moved along 
within the bores 30, 31. This movement is transferred to the sleeves 44 
and hence to the focusing lenses 45. 
For diopter focusing for the equalization of visual resolutions of the 
user, the annular bushing 48 surrounding the objective system is rotated. 
It is conventionally provided with fluting 50 or knurling. In the process, 
the driving pin 47 engaging the recess 46 of the sleeve 44 rotates the 
latter. Because this sleeve has a curved groove 43, cooperating with the 
horizontal end of the control element 26, during the rotation of the 
annular sleeve 48 an axial displacement of the sleeve 44, and thus of the 
focusing lens 45, simultaneously takes place.