Abstract:
An objective lens unit for endoscopes, with an objective lens having at least one lens and with an objective lens frame that is mounted in an endoscope housing in such a way that the insertion depth in the distal direction is restricted by a covering glass established in the endoscope housing and the objective lens frame that can be fastened in the endoscope housing forms the proximal end. In order to provide an objective lens unit for endoscopes that is simple to assemble and can be positioned in stationary manner in the endoscope housing, it is proposed according to the invention that the objective lens frame should be capable of being removably fastened in the endoscope housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority of German patent application No. 10 2010 050 932.9 filed on Nov. 11, 2010, the content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to an objective lens unit for endoscopes, with an objective lens comprising at least one lens as well as with an objective lens frame that is thus mounted in an endoscope housing. 
     BACKGROUND OF THE INVENTION 
     Objective lens units of this type are known in the art in various embodiments. In order to adjust the objective lens in the longitudinal direction of the optical system on the one hand, and on the other hand to fasten the objective lens frame equipped with the objective lens in the endoscope housing in stationary manner, it is a familiar practice in the art to position the objective lens frame in the endoscope housing by means of a press-on element that, in turn, in the assembled state is non-separably cemented with the endoscope housing. 
     These known objective lens units have thoroughly proven themselves in the art; however, on the one hand, there is a risk of impurities from cementing the components and, on the other hand, there is no possibility of correcting after the fact a possible wrong positioning of the objective lens with respect to the optical axis, because the objective lens unit can no longer be dismantled. 
     SUMMARY OF THE INVENTION 
     It is consequently the object of the invention to provide an objective lens unit for endoscopes that is simple to assemble and can be positioned in the endoscope housing in stationary manner. 
     This object is fulfilled according to the invention in such a way that the objective lens frame can be separably fastened in the endoscope housing by at least one catch-lock connection. 
     As a result of the inventive separable arrangement of the objective lens frame in the endoscope housing, it becomes possible for the first time to dismantle the objective lens unit after the fact and to position the objective lens in the event of a possible erroneous position and to realign it in the correct position. 
     Inventive catch-lock connections are characterized in that they are simple to handle and guarantee a secure bonding of the components that are catch-locked to one another, while being simple and quick to separate again. 
     In order to prevent or to limit the pressure of the objective lens unit in the axial direction, that is, in particular in the direction toward the covering glass, so that the pressure is transmitted by the objective lens frame onto the objective lens that is connected with the objective lens frame, it is proposed according to a first embodiment of the invention that the insertion depth of the objective lens unit into the endoscope housing can be restricted in the distal direction by a stop for the objective lens frame. 
     According to an inventive embodiment, the stop is configured as an overhang in the endoscope housing, which the objective lens frame runs up against in the distal end position. 
     With an alternative embodiment of the invention, it is proposed that the stop should be configured as a catch-lock connection by which the objective lens frame can be separably secured in the endoscope housing. In this practical embodiment, two advantages are immediately provided by means of the catch-lock connection, namely the separable mounting of the objective lens frame in the endoscope housing and the restriction of the insertion depth of the objective lens unit into the endoscope housing. 
     With a first embodiment for configuring the inventive separable catch-lock connection, it is proposed that the catch-lock connection should consist of at least one catch-lock element positioned on the objective lens frame and at least of one catch-lock recess configured in the endoscope housing for receiving a catch-lock element each time. 
     Here, the catch-lock element is advantageously positioned on the spring-elastically-configured proximal end of the objective lens frame. The spring-elasticity of the proximal end of the objective lens frame ensures that the catch-lock element engages automatically into the corresponding catch-lock recess as soon as the two components are brought into congruence with one another. 
     Alternatively, the at least one catch-lock element, configured for example as a rod or sphere, can also be positioned in the endoscope housing and the catch-lock recess can be positioned on the objective lens frame. 
     In addition, for the first embodiment of the invention, it is proposed that the catch-lock connection should be capable of being fastened in the catch-locked position by a holding element that can be inserted into the objective lens frame from the proximal side, so that the at least one catch-lock element is pressed radially outward by the holding element into the corresponding catch-lock recess. The catch-lock element is fastened in stationary manner in the catch-lock recess by means of the radial press-on force of the holding element. 
     To release the catch-lock connection for the first embodiment of the invention, it is proposed that the spring-elastic proximal end of the objective lens frame should be capable of bending radially inward by means of a dismantling tool that can be inserted from the proximal side into the endoscope housing. In using the holding element to fasten the catch-lock connection, said holding element of course must first be removed from the objective lens frame. 
     To release the catch-lock connection, in which the catch-lock element is positioned in the endoscope housing and the catch-lock recess is positioned on the objective lens frame, it is proposed that the catch-lock element should be capable of being pressed radially outward into the endoscope housing by means of a dismantling tool that can be applied from the proximal side onto the objective lens frame. 
     Finally, with a third embodiment for configuring the inventive separable catch-lock connection, it is proposed that the objective lens frame should be capable of being separably fastened by means of a press-on unit, which pressures the objective lens frame in the distal direction; here the press-on unit advantageously consists of a spring element configured as a pressure spring and of an abutment for the pressure spring, and the abutment can be separably fastened on the endoscope housing by means of at least one catch-lock connection. Use of the pressure spring in the press-on unit serves to press the objective lens frame in the distal direction against the overhang in the endoscope housing and thus to position the objective lens, which is connected with the objective lens frame, in the axial direction in a stationary manner in the endoscope housing. 
     To configure the abutment, it is proposed with the invention that said abutment should be configured as a slotted spring-elastic sheath, such that the distal border of the sheath comprises a surrounding catch-lock protrusion, which in assembled condition engages into a surrounding catch groove in the endoscope housing to configure the separable catch-lock connection. The abutment section, with which the spring element is directly contiguous, is the proximal section of the sheath, which is configured as a portion of a ring. 
     Finally, it is proposed with the invention that the sheath should be configured to taper conically in the proximal direction, so that a dismantling tube can be slid onto the conical outer wall of the sheath to release the catch-lock connection between the sheath and the endoscope housing, so that the spring-elastic sheath is compressed radially inward by its proximal ring portion until the surrounding catch-lock protrusion goes out of engagement with the catch groove configured in the endoscope housing. 
     Further properties and advantages of the invention can be seen from the appended drawings, in which five embodiments of an inventive objective lens unit for endoscopes are illustrated merely as examples, without restricting the invention to these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a longitudinal section through a first embodiment of an inventive objective lens unit. 
         FIG. 2  shows a longitudinal section through a second and third embodiment of an inventive objective lens unit. 
         FIG. 3  shows a longitudinal section through a fourth embodiment of an inventive objective lens unit. 
         FIG. 4  shows a longitudinal section through a fifth embodiment of an inventive objective lens unit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The objective lens units  1  for endoscopes, illustrated in  FIGS. 1 through 4 , consist essentially of an objective lens  3  comprising at least one lens  2 , as well as of an inventive lens frame  4 , whereby the objective lens unit  1  is mounted in an endoscope housing  5  in such a way that the objective lens unit  1  is positioned on the distal end leaving an aerial space from a covering glass  6  fastened in the endoscope housing  5  and so that the objective lens frame  4  that can be fastened in the endoscope housing  5  forms the proximal end of the objective lens unit  1 . 
     To restrict the insertion depth of the objective lens unit  1  into the endoscope housing  5  in the distal direction, in the embodiments illustrated in  FIGS. 1 through 3  a stop in the form of an overhang  7  is configured in the endoscope housing  5 , and the objective lens frame  4  connected with the objective lens  3 , for example by cementing, is contiguous with said stop upon insertion into the endoscope housing  5  and thus, on the one hand, further insertion in the distal direction is prevented, so that pressure on the optical components of the objective lens unit  1  is avoided, and, on the other hand, precisely located installation of the object lens  3  is ensured. 
     Alternatively and/or in addition, the insertion depth of the objective lens unit  1  in the distal direction into the endoscope housing  5  in the embodiments illustrated in  FIGS. 2 through 4  is restricted by a catch-lock connection  8 , by means of which the objective lens frame  4  that guides the objective lens  3  on the proximal end can be separably fastened in the endoscope housing  5 . As soon as the catch-lock connection  8  is locked while inserting the objective lens frame  4  into the endoscope housing  5  and thus the objective lens frame  4  and the endoscope housing  5  are fixed with respect to one another, the objective lens  3  connected with the objective lens frame  4  cannot be inserted any further in the distal direction into the endoscope housing  5 . 
     Use of the catch-lock connection  8  for fastening the objective lens frame  4  in the endoscope housing  5  has in addition the advantage that the objective lens unit  1  is easy to install and to dismantle again. The successive capacity to dismantle the objective lens unit  1 , in fact, constitutes an essential advantage over the state of the art, because for example faulty alignments of the objective lens  3  with respect to the optical axis  9  are correctible and impurities that can collect upon cementing the conventional objective lens units  1  are completely excluded. 
     The embodiments illustrated in  FIGS. 1 through 4  are distinguished from one another by the configuration of the objective lens frame  4  as well as of the catch-lock connections  8  for separable mounting of the objective lens frames  4  in the endoscope housings  5 . 
     In the first embodiment, illustrated in  FIG. 1 , the objective lens frame  4  can be separably fastened in the endoscope housing  5  by a press-on unit  10 , which presses the objective lens frame  4  and thus also the objective lens  3  connected with the objective lens frame  4  in the distal direction, and the press-on unit  10  consists of a spring element configured as a pressure spring  11  as well as an abutment  12  for the pressure spring  11  that can be fastened on the endoscope housing  5  by means of the catch-lock connection  8 . 
     Use of the pressure spring  11  in the press-on unit  10  serves to press the objective lens frame  4  in the distal direction against the overhang  7  in the endoscope housing  5  and thus to position the objective lens  3  connected with the objective lens frame  4  in the axial direction in a stationary manner in the endoscope housing  5 . 
     As can be further seen in  FIG. 1 , the abutment  12  is configured as a slotted spring-elastic sheath  13 , such that the distal edge of the sheath  13  comprises a surrounding catch-lock protrusion  14  that, in installed condition, engages in a surrounding catch groove  15  in the endoscope housing  5  in order to form the separable catch-lock connection  8 . On the proximal end, the sheath  13  is configured to taper conically. The spring elasticity of the sheath  13  is achieved by means of slits that are configured from the distal end of the sheath  13  heading in the axial direction of the sheath  13 . 
     The spring elasticity of the sheath  13  serves to allow the sheath  13  to be pressed together radially toward the inside upon insertion in the endoscope housing  5  and serves to allow the surrounding catch-lock protrusion  14  to engage automatically in the catch-lock groove  15  configured in the endoscope housing  5  upon reaching the corresponding position because of the expansion of the sheath  13  in the radial direction, in order to fix the abutment  12  and thus the objective lens frame  4  or the entire objective frame unit  1  as well, in the axial direction in the endoscope housing  5 . 
     As shown in  FIG. 1 , to insert the objective lens unit  1  into the endoscope housing  5 , an installation pin  17  can be used that can be applied to the sheath  13  from the proximal end. 
     To release the catch-lock connection  8  and thus to dismantle the objective lens unit  1 , a dismantling tool  18 , which is configured as a tube for instance, can be slid on the conical outer wall of the sheath  13  between the sheath  13  and the endoscope housing  5 , so that the spring-elastically configured sheath  13  is pressed together radially inward until the surrounding catch-lock protrusion  14  goes out of engagement with the catch-locking groove  15  configured in the endoscope housing  5 . 
     In the embodiments illustrated in  FIGS. 2 and 3 , the catch-lock connection  8  consists of at least one catch-lock element  19  positioned on the objective lens frame  4  and at least one catch recess  20  configured in the endoscope housing  5  to receive in each case one catch-lock element  19 , such that the at least one catch-lock element  19  is positioned on the spring-elastically configured proximal end of the objective lens frame  4 . Here the catch-lock recess  20  is configured in the form of a borehole. 
     The spring-elastic configuration of the proximal end of the objective lens frame  4  serves to allow the objective lens frame  4  to be pressed together radially inward upon insertion into the endoscope housing  5  and, upon reaching the corresponding position, allows the at least one catch-lock element  19  to engage automatically in the catch-lock recess  20  configured in the endoscope housing  5  because of the expansion of the objective lens frame  4  in the radial direction, in order to fix the objective lens frame  4  or the entire objective lens unit  1  without free play in the axial direction in the endoscope housing  5 . Rotational fixing is likewise ensured, because the catch-lock recess  20  or recesses  20  are configured on concrete peripheral positions of the endoscope housing  5 . 
     As can be seen from  FIG. 2 , to release the catch-lock connection  8  and thereby to dismantle the objective lens unit  1 , a dismantling tool  18 , configured for instance as a tube, can be slid onto the spring-elastic proximal end of the objective lens frame  4 , so that the spring-elastically configured proximal end of the objective lens frame  4  is pressed together radially inward until the at least one catch-lock element  19  goes out of engagement with the catch-lock recess  20  configured in the endoscope housing  5 . 
     To configure the at least one catch-lock element  19  that is positioned on the spring-elastic proximal end of the objective lens frame  4 , two embodiments are illustrated in  FIG. 2 , namely the configuration of the catch-lock element  19  as a pin  21 —in the upper part of  FIG. 2 —or as a sphere  22 —in the lower part of  FIG. 2 . 
     In the fourth embodiment, illustrated in  FIG. 3 , the at least one catch-lock element  19  of the catch-lock connection  8  is configured as a latch  23  that is formed on the spring-elastic end of the objective lens frame  4  and engages by catching in the corresponding catch-lock recess  20  in the endoscope housing  5 . In this embodiment the catch-lock recess  20  is preferably configured as a ring-shaped catch-lock recess, for example as a ring groove  20 . 
     In addition,  FIG. 3  shows that the catch-lock connection  8  can be rotationally fixed, particularly in the catch position, by means of a holding element  24  that can be inserted from the proximal end into the objective lens frame  4 . In the illustrated embodiment, the holding element  24  can be fastened to the objective lens frame  4  by a threaded connection  25 . 
     The holding element  24  is essentially tubular in shape and widens conically in the proximal direction. Alternatively or in addition, the side of the objective lens frame  4  that faces the holding element can be configured conically in the area of the latch  23 . 
     Owing to the radial pressure force of the holding element  24 , the catch-lock element  19  is fixed in stationary manner and friction-locked in the catch-lock recess  20 . As a result, a rotational fixing can thus be established, in this case a friction-locked connection—instead of a form-fitting connection as in the preceding embodiment. 
     In the fifth embodiment, illustrated in  FIG. 4 , the catch-lock connection  8  consists of at least one catch-lock element  26  positioned in the objective lens frame  4  and at least one catch-lock recess  27  configured in the endoscope housing  5  to receive in each case one catch-lock element  26 ; here the catch-lock element  26  is configured by way of example in the illustrated embodiment as a sphere  28 , although other configurations are also possible. The catch-lock recess  27 , as in the preceding embodiments, can be configured as a ring groove or else as a borehole or boreholes on one or more concrete peripheral positions on the endoscope housing  5 . 
     In addition,  FIG. 4  shows that the catch-lock connection  8  can be moved into the catch-lock position and can be fixed in said position by means of a holding element that can be inserted from the proximal end into the objective lens frame  4 , and that the sphere  28  is pressed radially outward into the corresponding catch-lock recess  27  by the holding element  29 . In the illustrated embodiment, the holding element  29  can be fastened to the objective lens frame  4  by a threaded connection  30 . Owing to the radial press-on force of the holding element  29 , the sphere  28  is fixed in stationary manner and friction-locked in the catch-lock recess  27 . As a result, in addition to the axial securing of the objective lens frame  4  in the endoscope housing  5 , rotational fixing is also ensured. This occurs, first of all, because the catch-lock recess  27  is configured in the shape of the ring groove and the connection between the catch-lock element  26  and the catch-lock recess  27  is sufficiently friction-locked in the holding element  29  that is screwed in for the catching position. It occurs, secondly, because the catch-lock recess  27  is configured in the form of the concrete peripheral position or positions of the endoscope housing  5 . 
     In the illustrated embodiment of the holding element  29 , the sphere  28  is pressed into the catch-lock recess  27  in the endoscope housing by a spring-elastic press-on arm  31 . The spring force of the press-on arm  31  acting on the sphere  28  is increased or reduced depending on the screw-in depth of the holding element  29  into the objective lens frame  4 . This occurs because the press-on arm  31  is configured as a segment of a sheath that widens in the proximal direction. 
     To release the catch-lock connection  8  and thus to dismantle the objective lens unit  1 , the holding element  29  is screwed out of the objective lens frame  4 , so that the sphere  28  falls radially inward out of the catch-lock recess  27  and the catch-lock connection  8  is cancelled. The objective lens unit  1  can be drawn thereafter in the proximal direction out of the endoscope housing  5 . 
     The objective lens units  1  configured as described in the foregoing are characterized in that they can be fastened in the endoscope housing  5  so that they are removable and thus capable of dismantling.