Abstract:
A viewing optical instrument includes a main barrel which supports an objective optical system, a movable member for focus adjustment which is supported by the main barrel to be movable along an optical axis of the objective optical system relative to the main barrel, a focusing mechanism which drives the movable member along the optical axis, a focus knob which actuates the focusing mechanism, an auxiliary unit provided separately from the viewing optical instrument including an auxiliary mechanism which is associated with the focusing mechanism when the auxiliary unit is connected to the viewing optical instrument, and a connecting device for detachably attaching the auxiliary unit to the viewing optical instrument.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a focusing device of a viewing optical instrument such as an astronomical telescope. 
     2. Description of the Related Art 
     A rack-and-pinion type focusing device is generally used as a focusing device for conventional viewing optical instruments such as astronomical telescopes. In rack-and-pinion type focusing devices, a pinion is driven by rotating a focus knob to move a focus member (generally a movable tube which is movable relative to the telescope main tube) provided thereon with a rack meshing with the pinion in the optical axis direction so as to bring a distant object into focus. In this conventional type focusing device, since the focusing operation is carried out by manually rotating the focus knob, the astronomical telescope cannot stay still due to hand movement. This deteriorates the accuracy of focusing. 
     If the pinion is driven by a motor, the accuracy of focusing improves because the astronomical telescope is prevented from suffering from such hand movement. However, among conventional astronomical telescopes, no astronomical telescope is known to be provided with a rack-and-pinion type focusing device whose focusing operation mode can be easily switched between a manual operation mode, in which the pinion is driven manually, and a motor operation mode in which the pinion is driven by motor. Moreover, in conventional astronomical telescopes, the concept of utilizing the positional information of the aforementioned focus member via a feedback function is not known in the art. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a focusing device of a viewing optical instrument, wherein an auxiliary unit, provided independently from the body of the viewing optical instrument, can be connected to the body of the viewing optical instrument as needed. The auxiliary unit extends the capability of a manual focusing device of the viewing optical instrument, providing the viewing optical instrument with a motor-driven focusing function or a positional information feedback function. 
     To achieve the object mentioned above, according to an aspect of the present invention, a viewing optical instrument is provided, including a main barrel which supports an objective optical system; a movable member for focus adjustment which is supported by the main barrel to be movable along an optical axis of the objective optical system relative to the main barrel; a focusing mechanism which drives the movable member along the optical axis; a focus knob which actuates the focusing mechanism; an auxiliary unit provided separately from the viewing optical instrument including an auxiliary mechanism which is associated with the focusing mechanism when the auxiliary unit is connected to the viewing optical instrument; and a connecting device for detachably attaching the auxiliary unit to the viewing optical instrument. 
     When the auxiliary unit is connected to the viewing optical instrument, the auxiliary mechanism is coupled to the focusing mechanism via a route different from a route of which the focus knob is coupled to the focusing mechanism. 
     Preferably, the viewing optical instrument further includes a fixed housing fixed to the main barrel, and a first mount, formed on the fixed housing, on which the auxiliary unit is mounted, the first mount having a first through hole through which part of the focusing mechanism is exposed to the outside of the viewing optical instrument. 
     Preferably, a cover is further provided, which is connected to the first mount when the auxiliary unit is not connected to the first mount. 
     Preferably, the focusing mechanism includes a rack fixed to the movable member, the rack extending parallel to the optical axis, and a first pinion which is rotatably supported to mesh with the rack. The first pinion is driven when the focus knob is operated. 
     The viewing optical instrument can be an astronomical telescope. 
     Preferably, the movable member is a movable barrel fitted in the main barrel to be movable along the optical axis of the objective optical system relative to the main barrel. 
     In an embodiment, the driven device includes a counter which indicates the axial position of the movable member. 
     In an embodiment the auxiliary unit includes a second mount which is mounted onto the first mount when the auxiliary unit is connected to the viewing optical instrument. The second mount has a second through hole through which part of the auxiliary mechanism is exposed to the outside of the auxiliary unit, and the first through hole is aligned with and the second through hole when the auxiliary unit is mounted onto the first mount. 
     According to another aspect of the present invention, a viewing optical instrument includes a main tube and a drawtube which is drawn out of and inserted into the main tube to focus the telescope on an object which is to be viewed through the telescope; a focusing mechanism for driving the drawtube relative to the main tube; a focus knob which actuates the focusing mechanism; an auxiliary unit provided separately from the viewing optical instrument, the auxiliary unit including a auxiliary mechanism which is associated with the focusing mechanism when the auxiliary unit is connected to the telescope; and a connecting device for detachably attaching the auxiliary unit to the telescope. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No.11-247161 (filed on Sep. 1, 1999) which is expressly incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described below in detail with reference to the accompanying drawings in which: 
     FIG. 1 is a fragmentary perspective view of an embodiment of an astronomical telescope provided with a focusing device according to the present invention; 
     FIG. 2 is a fragmentary perspective view of the embodiment of the astronomical telescope shown in FIG. 1, showing a state where a mounting connector, a focus knob and a cover are removed; 
     FIG. 3 is a perspective view of an auxiliary unit which is connectable to the astronomical telescope shown in FIG. 1; 
     FIG. 4 is a cross sectional view, taken along a plane extending perpendicular to an optical axis of the astronomical telescope, of the auxiliary unit and part of a fixed housing of the astronomical telescope shown in FIG. 1, showing a state where the auxiliary unit is connected to the fixed housing; 
     FIG. 5 is a cross sectional view, taken along a plane including the optical axis of the astronomical telescope, of the auxiliary unit and part of the fixed housing shown in FIG. 4; 
     FIG. 6 is a view similar to that of FIG. 4 illustrating another embodiment of a focusing mechanism of the astronomical telescope; and 
     FIG. 7 is a view similar to that of FIG. 4 illustrating another embodiment of the auxiliary unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an embodiment of an astronomical telescope to which the present invention is applied. This astronomical telescope is provided with a telescope main barrel (fixed lens barrel/main tube)  10 , a fixed housing  20 , a movable barrel (drawtube/movable member)  30  and a focusing mechanism  40 . An objective lens group (not shown) is supported by the telescope main barrel  10  therein. The fixed housing  20  is fixed at the rear end of the telescope main barrel  10 . The movable barrel  30  is supported by the fixed housing  20  to be movable along an optical axis of the objective lens group (the horizontal direction as viewed in FIG.  1 ). The movable barrel  30  is driven along the optical axis by the focusing mechanism  40 . The focusing mechanism  40  is further provided with left and right focus knobs  60  which are manually operated by the user. 
     The movable barrel  30  is provided at the rear end thereof with a mounting connector  70  to which a viewing instrument (optical instrument) such as an eyepiece adapter or a camera (e.g., an SLR camera, a lens-shutter camera or a CCD camera) is connected. In the illustrated embodiment of the astronomical telescope, the focal point of the objective lens group supported by the telescope main barrel  10  varies depending on the object distance. Thus the movable barrel  30  is moved along the optical axis of the objective lens group relative to the telescope main barrel  10  to focus the telescope on a distant object so that an in-focus distant object can be viewed through a viewing instrument which is connected to the mounting connector  70 . Accordingly, the movable barrel  30  can be referred to as a movable member for focus adjustment which moves by an operation of bringing a distant object into focus. Although the illustrated embodiment of the astronomical telescope is a refracting telescope having the objective lens group (which includes an achromat) in the telescope main barrel  10 , the astronomical telescope can be a reflecting telescope having a combination of mirrors in the telescope main barrel  10 . 
     FIG. 1 is a fragmentary perspective view of the astronomical telescope with an auxiliary drive unit (auxiliary unit)  50  being connected to the fixed housing  20 . FIG. 2 shows a fragmentary perspective view, seen from below the fixed housing  20 , of the astronomical telescope shown in FIG.  1 . In FIG. 2, the auxiliary drive unit  50 , the mounting connector  70  and the left and right focus knobs  60  are removed and thus not illustrated. The astronomical telescope is provided at the bottom of the fixed housing  20  with a shaft  41  which is supported by the fixed housing  20  to be rotatable about an axis extending in a direction perpendicular to the optical axis of the objective lens group, but not intersecting the optical axis of the objective lens group. The shaft  41  is provided at an approximate center thereof with the pinion  42  fixed to the shaft  41 . The right and left focus knobs  60  are fixed at the opposite ends of the shaft  41 , respectively. The movable barrel  30  is provided on an outer peripheral surface thereof with the rack  43  fixed to the movable barrel  30  and extending parallel to the optical axis of the objective lens group. The pinion  42  stays in mesh with the rack  43 . The rack  43  and the pinion  42 , which forms a rack-and-pinion mechanism, are fundamental elements of the focusing mechanism  40 . 
     The fixed housing  20  is provided with a housing mount  21  on which the auxiliary drive unit  50  is mounted. A cover  22  is mounted on the housing mount  21  when the auxiliary drive unit  50  is not used. The housing mount  21  is provided with four threaded holes (auxiliary unit connecting device)  21   a  and a rectangular through hole  21   b . FIG. 2 shows the housing mount  21  with the cover  22  being removed therefrom. The pinion  42  is exposed to the outside of the housing mount  21  through the through hole  21   b . When the auxiliary drive unit  50  is not used, the cover  22  is fixed to the housing mount  21  by four set screws  44 , screwed into the four corresponding threaded holes  21   a.    
     The mounting connector  70 , which is connected to the rear end of the movable barrel  30 , includes an extension tube  71  whose front end is connected to the rear end of the movable barrel  30 , and an adapter ring  72  whose front end is inserted into the extension tube  71 . The adapter ring  72  is provided at the rear end thereof with an eyepiece socket  73  (viewing optical instrument insertion opening)  73 . A viewing optical instrument such as an eyepiece or a camera can be connected to the eyepiece socket  73 . 
     Rotation of either one of the left and right focus knobs  60  causes the pinion  42  to rotate via the shaft  41 , so that the rack  43 , which is in mesh with the pinion  42 , moves in the optical axis direction. Consequently, the movable barrel  30 , to which the rack  43  is fixed, moves in the optical axis direction relative to the fixed housing  20  therein. Due to this movement of the movable barrel  30  relative to the fixed housing  20 , the space between the objective lens group and the viewing instrument connected to the mounting connector  70  varies, which makes it possible to focus the astronomical telescope on a distant object so that an in-focus distant object can be viewed through the viewing instrument. Accordingly, in a state where the cover  22  is fixed to the housing mount  21 , i.e., where the auxiliary drive unit  50  is not mounted on the housing mount  21 , a manual focusing operation, in which either one of the left and right focus knobs  60  is operated to focus the astronomical telescope on a distant object, can be performed in a manner similar to a conventional type astronomical telescope. 
     FIGS. 3 through 5 shows an embodiment of the auxiliary drive unit  50 . The auxiliary drive unit  50  includes a housing  51  and a drive mechanism (auxiliary mechanism)  53  disposed in the housing  51 . The housing  51  is provided with a drive unit mount  52 . The drive unit mount  52  is provided with four through holes (auxiliary unit connecting device)  52   a  and a rectangular through hole  52   b  which are formed to correspond to the four threaded holes  21   a  and the rectangular through hole  21   b , respectively. The auxiliary drive unit  50  is mounted on the housing mount  21  by screwing the set screws  44  into the threaded holes  21   a  via the through holes  52   a.    
     The drive mechanism  53  is provided with a motor  53   a , a drive pinion  53   b  fixedly fitted on the drive shaft of the motor  53   a , and a reduction gear train including first through fourth gears  53   c ,  53   d ,  53   e  and  53   f . The drive pinion  53   b  is in mesh with the first gear  53   c . The first gear  53   c  and the second gear  53 d are fixedly fitted on a shaft  53   h . The second gear  53   d  is in mesh with the third gear  53   e . The third gear  53   e  and the fourth gear  53   f  are fixedly fitted on a shaft  53   i . The shafts  53   h  and  53   i  extend parallel to the drive shaft of the motor  53   a . As shown in FIG. 3, the outer edge of the final gear (fourth gear)  53   f  is exposed to the outside of the auxiliary drive unit  50  through the rectangular through hole  52   b  so that the final gear  53   f  is engaged with the pinion  42  of the focusing mechanism  40  when the auxiliary drive unit  50  is mounted on the housing mount  21 . 
     At the time of mounting the auxiliary drive unit  50  on the housing mount  21 , firstly, the drive unit mount  52  is brought into intimate contact with the housing mount  21  with the four through holes  52   a  being aligned with the corresponding four threaded holes  21   a . Thereafter, the four set screws  44  are screwed into the four threaded holes  21   a  via the four through holes  52   a , respectively, to fix the drive unit mount  52  to the housing mount  21 . This makes the final gear  53   f  mesh with the pinion  42  of the focusing mechanism  40  as shown in FIGS. 4 and 5. In this state, if the motor  53  is driven to rotate the drive pinion  53   b , the rotation of the motor  53  is transmitted to the rack  43  via the first through fourth gears  53   c ,  53   d ,  53   e  and  53   f  and the pinion  42  to thereby move the movable barrel  30  in the optical axis direction relative to the telescope main barrel  10 . Accordingly, the focusing mechanism  40  having the rack  43  and the pinion  42  can provide a motor-driven focusing function if the auxiliary drive unit  50  is connected to the housing mount  21 . Namely, the motor  53   a  is driven to move the movable barrel  30  in the optical axis direction to bring a distant object into focus by operating an operation switch (not shown) to turn ON and OFF the power of the motor  53   a.    
     In a state shown in FIGS. 4 and 5 where the auxiliary drive unit  50  is mounted on the housing mount  21 , the movable barrel  30  can be driven manually by operating either one of the left and right focus knobs  60 . Accordingly, in a state shown in FIGS. 4 and 5, the motor-driven focusing operation and the manual focusing operation can be selectively performed without removing the auxiliary drive unit  50  from the housing mount  21  since the auxiliary mechanism (drive mechanism  53 ) is coupled to the focusing mechanism via a route different from a route of which the focus knob is coupled to the focusing mechanism. 
     In the illustrated embodiment described above, although the final gear  53   f  of the auxiliary drive unit  50  meshes with the pinion  42  of the focusing mechanism  40 , the focusing mechanism  40  can be modified so that the final gear  53   f  of the auxiliary drive unit  50  directly meshes with the rack  43  without using any pinion disposed between the final gear  53   f  and the rack  43  as shown in FIG.  6 . 
     FIG. 7 shows another embodiment of the auxiliary unit which is mounted on the housing mount  21  of the astronomical telescope shown in FIG.  1 . This auxiliary unit  50 ′ is identical to the auxiliary drive unit  50  of the previous embodiment except that the motor  53   a  shown in FIG. 4 is replaced by a driven counter (driven device)  53   g  which is driven by drive force transmitted from the focusing mechanism  40 . In this embodiment the driven counter  53   g  and the reduction gear train ( 53   b  through  53   f ) constitute a counter mechanism (auxiliary mechanism)  53 ′. If one of the left and right focus knobs  60  is operated, namely, if the movable barrel  30  is driven in the optical axis direction via the shaft  41 , the pinion  42  and the rack  43 , the driven counter  53   g  is driven at the same time via the shaft  41 , the pinion  42 , the reduction gear train ( 53   b  through  53   f ) and the driven pinion  53   b . Therefore, since the movable barrel  30  and the driven counter  53   g  are synchronous, the axial position of the movable barrel  30  can be detected (recorded) by reading the number of the driven counter  53   g.    
     According to each of the previous embodiments to which the present invention is applied, in order to make it possible to connect the auxiliary unit  50  or  50 ′ to a conventional astronomical telescope, the astronomical telescope only needs a slight modification by forming a mount (which corresponds the housing mount  21 ) on a housing (which corresponds the fixed housing  20 ) of the astronomical telescope. This slight modification only requires a slight increase in the cost of production of the astronomical telescope. 
     According to each of the previous embodiments to which the present invention is applied, the astronomical telescope is designed so that only one auxiliary unit  50  or  50 ′ can be connected to the fixed housing  20 ; however, it is possible to design the astronomical telescope so that the two auxiliary unit  50  and  50 ′ can be connected to the fixed housing  20  at the same time. 
     In the illustrated embodiments, the auxiliary unit  50  or  50 ′ is fixed to the housing mount  21  by set screws  44 , so that the auxiliary unit  50  or  50 ′ can be easily mounted on and removed from the housing mount  21  with a simple tool such as a screwdriver. However, the means for fixing (connecting) the auxiliary unit  50  or  50 ′ to the housing mount  21  is not limited solely to such set screws. For instance, a bayonet coupling can be used as a connecting device, which makes the removability of the auxiliary unit easier. 
     In the illustrated embodiments, although the present invention is applied to astronomical telescope, the present invention can be applied to any other viewing optical instrument such as a spotting scope (monocular) or a microscope. 
     As can be understood from the foregoing, according to the present invention, in a viewing optical instrument such as an astronomical telescope which requires a manual focusing operation, a focusing device of the viewing optical instrument has been achieved wherein an auxiliary unit having, for example, a drive motor, can be connected to the astronomical telescope at a low cost of production, wherein the auxiliary unit can be easily removed. 
     Obvious changes may be made in the specific embodiments of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.