Abstract:
The invention is directed to an afocal zoom system, particularly for use in microscopes, comprising at least four optical assemblies, two of which assemblies are movable relative to one another and to the rest of the assemblies for the purpose of changing the magnification. It is the object of the invention to develop an afocal zoom system which enables a relatively small structural size for a microscope also in combination with a suitable drive mechanism. This object is met by an afocal zoom system of the type described above in which every adjustable magnification can be achieved by a displacing movement of the two movable optical assemblies in the same direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority of German Application No. 103 59 733.6, filed Dec. 19, 2003, the complete disclosure of which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     a) Field of the Invention  
         [0003]     The invention is directed to an afocal zoom system, particularly for use in microscopes, comprising at least four optical component groups or assemblies, two of which are movable relative to one another and relative to the rest of the assemblies for purposes of changing magnification.  
         [0004]     b) Description of the Related Art  
         [0005]     Afocal zoom systems are known per se. They are used for the purposes changing magnification in conventional microscopes as one-channel systems or in stereo microscopes and surgical microscopes in two-channel construction according to the type of telescope. In contrast to Greenough type stereo microscopes using two objectives and two separate microscope beam paths which are inclined relative to one another at an angle of 12° to 14°, the telescope type is an embodiment form that is outfitted with a main objective common to both beam paths, the object lying in the object-side focal plane of the main objective. In this case, two partial bundles which are parallel to one another are cut out of the parallel light bundles offered by the objective in such a way that their axes which converge in front of the objective form the required angle of 12° to 14° and generate two real intermediate images considered at this angle.  
         [0006]     Because of their limiting structural constraints, afocal zoom systems differ from photographic, video and telescopic systems and must therefore be classed in a special field of technology. In particular, the limited permissible lens diameter in two-channel constructions does not allow existing zoom systems already used in the fields and product groups mentioned above to be transferred to microscopy.  
         [0007]     Afocal zoom systems with four optical assemblies and a zoom factor greater than 8 are often used in microscopes. Systems such as these are described, for example, in DE 202 07 780 U1, U.S. Pat. No. 6,320,702 B1, U.S. Pat. No. 6,157,495 and U.S. Pat. No. 6,335,833 B1.  
         [0008]     Considered from the object, the systems indicated in these references are similarly formed of a stationary first group with positive refractive power, a movable second group with negative refractive power, a movable third group with positive refractive power, and a stationary fourth group with negative refractive power. The two middle groups are moved in opposite directions relative to one another in order to change the magnification. The magnification decreases when the distance between the two movable groups is increased.  
         [0009]     All of the prior art publications cited above relate to this basic construction and this movement characteristic of the two movable assemblies.  
         [0010]     Most of the space available for the entire zoom system is claimed by the movement areas of the movable assemblies. For example, the movement range in the zoom system according to U.S. Pat. No. 6,335,833 B1 is about 102 mm, while the overall length of the system and, therefore, the installed dimension, is about 150 mm.  
         [0011]     This has the disadvantage that a space-saving construction of the components required for guiding the movable optical assemblies is not possible, which prevents a reduction of the structural dimensions of the microscopes. This applies particularly to microscopes in which the zoom system and the associated drive unit may not exceed predetermined dimensions.  
       OBJECT AND SUMMARY OF THE INVENTION  
       [0012]     On this basis, it is the primary object of the invention to develop an afocal zoom system which enables a relatively small structural size for a microscope also in combination with a suitable drive mechanism.  
         [0013]     This object is met by an afocal zoom system of the type mentioned above in which every adjustable magnification can be achieved by means of a displacing movement of the two movable optical assemblies in the same direction.  
         [0014]     In this way, in connection with a drive arrangement, a smaller constructional space than was previously possible in the art can be realized. This is because the moving optical assemblies are usually spatially oriented on two rods. In this case, a carrier with a receptacle for an optical assembly is designed in such a way that it encloses one of the rods as a sleeve and touches the second rod as a means for preventing rotation. As a result, the free length of the rods is greater than the movement length of the optical assembly and the length of the sleeve.  
         [0015]     When the carriers move in opposite directions, the guide lengths are summed and are accordingly greater than the space required for the optical assemblies. This prevents a reduction in the structural dimensions of the microscopes. However, when the two carriers move in the same direction, it is possible to guide them on two parallel rods without these rods needing to be longer than the optical installation space.  
         [0016]     In a first embodiment, the afocal zoom system according to the invention comprises four optical assemblies, of which, beginning on the object side or infinity space from the objective, a first assembly is stationary with positive refractive power, a second assembly is movable with negative refractive power, a third assembly is stationary with positive refractive power, and a fourth assembly is movable with negative refractive power.  
         [0017]     It is advantageously provided that the two movable assemblies are movable at different displacement speeds and the lowest possible magnification is adjusted when the two movable assemblies are displaced farthest in the direction of the first assembly.  
         [0018]     In a second embodiment, the afocal zoom system according to the invention comprises five optical assemblies, of which, beginning on the object side, a first assembly is stationary with positive refractive power, a second assembly is movable with negative refractive power, a third assembly is stationary with positive refractive power, a fourth assembly is movable with negative refractive power, and a fifth assembly is stationary with positive refractive power.  
         [0019]     It is also provided in this case that the two movable assemblies are movable at different displacement speeds and, again, the magnification is lowest when both movable assemblies are displaced farthest in the direction of the first assembly.  
         [0020]     It should be mentioned that, in principle, the zoom system can also be arranged in the reverse sequence of optical assemblies in the microscope beam path, in which case, beginning on the image side or in infinity space from the tube lens, the first assembly is arranged first.  
         [0021]     The movable assemblies can optionally be connected to drive devices in any of the zoom systems described according to the invention. These drive devices are constructed in the form of drum cams, as a rack and pinion with positive control by means of a cam disk, as a positive control by means of a plurality of cam disks, as a direct motor drive, preferably in the form of a stepper motor, or as a lever system with differential movement and positive control by means of a cam disk.  
         [0022]     The afocal zoom system according to the invention will be described more precisely in the following with reference to a number of examples in the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     In the drawings:  
         [0024]      FIG. 1  shows a first constructional variant with four optical assemblies and a structural length of 130 mm;  
         [0025]      FIG. 2  shows the movement characteristic of the zoom system from  FIG. 1 ;  
         [0026]      FIG. 3  shows a second constructional variant with four optical assemblies and a structural length of 160 mm;  
         [0027]      FIG. 4  shows the movement characteristic of the zoom system from  FIG. 3 ;  
         [0028]      FIG. 5  shows a third constructional variant with four optical assemblies and a structural length of 197 mm;  
         [0029]      FIG. 6  shows the movement characteristic of the zoom system from  FIG. 5 ;  
         [0030]      FIG. 7  shows a first constructional variant with five optical assemblies and a structural length of 130 mm;  
         [0031]      FIG. 8  shows the movement characteristic of the zoom system from  FIG. 7 ;  
         [0032]      FIG. 9  shows a second constructional variant with five optical assemblies and a structural length of 140 mm;  
         [0033]      FIG. 10  shows the movement characteristic of the zoom system from  FIG. 9 ;  
         [0034]      FIG. 11  shows a third constructional variant with five optical assemblies and a structural length of 160 mm;  
         [0035]      FIG. 12  shows the movement characteristic of the zoom system from  FIG. 11 ;  
         [0036]      FIG. 13  shows a fourth constructional variant with five optical assemblies and a structural length of 180 mm; and  
         [0037]      FIG. 14  shows the movement characteristics of the zoom system from  FIG. 13 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     The zoom system according to the invention shown in  FIG. 1  comprises four optical assemblies with a structural length of 130 mm and has the following system specifications:  
                                                                                             Index of   Abbe       Plane or   Radius   Thickness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity space                           from objective       LG1   55.83000               4.50000       1.530190   76.58           −55.83000               2.30000       1.584820   40.57           infinity                   a1       LG2   −35.22750               1.40000       1.747910   44.57           9.17300               2.50000       1.812659   25.16           25.12050                   a2       LG3   30.06750               1.50000       1.812659   25.16           15.07000               1.80000       1.489140   70.23           18.96900               2.90000       1.716160   53.61           −44.98960       Aperture       1.00000           infinity                   a3       LG4   −47.65660               1.30000       1.620680   49.54           7.94400               2.90000       1.624080   36.11           41.86920                   a4       Infinity space       from tube lens                  
 
         [0039]     In  FIG. 1  and in all of the following illustrations, the optical assemblies, beginning from the object side in each instance, are designated by LG 1  to LG 4  or LG 5 . Assemblies LG 2  and LG 4  are always movable in the direction of the optical axis of the zoom system in relation to the rest of the assemblies and, to this end, are coupled with drives, preferably stepper motors.  
         [0040]     The movement characteristic of the zoom system from  FIG. 1  is shown in  FIG. 2 . It can be seen from this that the initial magnification value is 0.32 and the final value is 4.0 and the magnification range is accordingly 12.5×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                4.0×   1.0×   0.32×                            a1   68.657   39.472   2.098           a2   11.189   40.373   77.747           a3   28.039   12.818   3.104           a4   0.016   15.237   24.951                      
 
         [0041]     The zoom system according to the invention shown in  FIG. 3  comprises four optical assemblies at a structural length of 160 mm and has the following system specifications:  
                                                                                             Index of   Abbe       Plane or   Radius   Thickness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity space                           from objective       LG1   56.75149               1.80000       1.584820   40.57           34.34561               3.23632       1.487940   84.07           399.82663                   a1       LG2   −42.51193               1.20000       1.747910   44.44           12.24683               2.43354       1.812639   25.16           35.41005                   a2       LG3   27.81808               1.50000       1.616640   44.27           11.53722               3.35345       1.530190   76.58           −38.54358       Aperture       2.00000           infinity                   a3       LG4   −35.44956               2.96303       1.652220   33.60           −11.34526               1.30000       1.620680   49.54           82.22593                   a4       Infinity space       from tube lens                  
 
         [0042]     The movement characteristic of the zoom system from  FIG. 3  is shown in  FIG. 4 . It can be seen that the initial magnification value is 0.32 and the final value is 4.75 and the magnification range is accordingly 14.8×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                4.75×   1.25×   0.32×                            a1   90.889   57.703   2.392           a2   5.936   39.122   94.433           a3   44.126   17.262   2.244           a4   0.000   26.864   41.882                      
 
         [0043]     The zoom system according to the invention shown in  FIG. 5  comprises four optical assemblies at a structural length of 197 mm and has the following system specifications:  
                                                                                             Index of   Abbe       Plane or   Radius   Thickness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity space                           from objective       LG1   59.45081               1.80000       1.584820   40.57           36.56531               3.09611       1.487940   84.07           323.75358                   a1       LG2   −47.70503               1.20000       1.747910   44.44           13.26264               2.44516       1.812639   25.16           37.95059                   a2       LG3   31.52821               1.50000       1.616640   44.27           13.05517               3.14976       1.530190   76.58           −46.21433       Aperture       2.00000           infinity                   a3       LG4   −46.50621               3.63255       1.652220   33.60           −13.80465               1.30000       1.620680   49.54           86.38284                   a4       Infinity space       from tube lens                  
 
         [0044]     The movement characteristic of the zoom system from  FIG. 5  is shown in  FIG. 6 . It can be seen that the initial magnification value is 0.32 and the final value is 5.43 and the magnification range is accordingly 17.0×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                5.43×   1.27×   0.32×                            a1   90.390   61.772   2.409           a2   5.284   40.902   100.265           a3   73.960   23.866   2.328           a4   0.000   50.094   71.632                      
 
         [0045]     The zoom system according to the invention shown in  FIG. 7  comprises five optical assemblies at a structural length of 130 mm and has the following system specifications:  
                                                                                             Index of   Abbe       Plane or   Radius   Variable   Thickness   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity space                           from objective       LG1   55.83000               4.50000       1.530190   76.58           −55.83000               2.30000       1.584820   40.57           infinity                   a1       LG2   −29.63900               1.40000       1.747910   44.57           9.57600               2.50000       1.812659   25.16           28.59370                   a2       LG3   17.66550               1.40000       1.708240   39.12           9.44240               3.15000       1.530190   76.58           −30.94640       Aperture       1.00000           infinity                   a3       LG4   −27.97950               2.10000       1.812659   25.16           −10.59190               1.30000       1.747910   44.57           38.12900                   a4       LG5   54.24520               2.05000       1.708240   39.12           33.25480               2.28000       1.489140   70.23           infinity       Infinity space       from tube lens                  
 
         [0046]     The movement characteristic of the zoom system from  FIG. 7  is shown in  FIG. 8 . It can be seen that the initial magnification value is 0.3 and the final value is 6.0 and the magnification range is accordingly 20.0×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                6.00×   2.00×   0.30×                            a1   69.713   51.441   2.608           a2   2.034   20.306   69.139           a3   32.226   20.448   4.346           a4   2.047   13.824   29.927                      
 
         [0047]     The zoom system according to the invention shown in  FIG. 9  comprises five optical assemblies at a structural length of 140 mm and has the following system specifications:  
                                                                                             Index of   Abbe       Plane or   Radius   Thickness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity                           space from       objective       LG1   54.46484               4.50000       1.530190   76.58           −54.53767               2.30000       1.584820   40.57           95114.5695                   a1       LG2   −28.70630               1.40000       1.747910   44.57           8.84044               2.50000       1.812659   25.16           26.08074                   a2       LG3   17.64930               1.55000       1.708240   39.12           9.44423               3.00000       1.530190   76.58           −33.13612       Aperture       1.00000           infinity                   a3       LG4   −26.24859               2.10000       1.812659   25.16           −10.15678               1.30000       1.747910   44.57           39.51109                   a4       LG5   73.94310               1.50000       1.708240   39.12           42.44389               2.00000       1.489140   70.23           −320.03785       Infinity       space from       tube lens                  
 
         [0048]     The movement characteristic of the zoom system from  FIG. 9  is shown in  FIG. 10 . It can be seen that the initial magnification value is 0.30 and the final value is 7.50 and the magnification range is accordingly 25.0×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                7.50×   3.08×   0.30×                            a1   69.688   56.394   3.216           a2   2.138   15.432   68.609           a3   43.154   31.715   7.118           a4   1.920   13.358   37.955                      
 
         [0049]     The zoom system according to the invention shown in  FIG. 11  comprises five optical assemblies at a structural length of 160 mm and has the following system specifications:  
                                                                                     Thick-       Index of   Abbe       Plane or   Radius   ness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity                           space from       objective       LG1   54.41669               4.50000       1.530190   76.58           −53.24124               2.30000       1.584820   40.57           −23179.171                   a1       LG2   −29.65255               1.40000       1.747910   44.57           8.37016               2.50000       1.812659   25.16           23.91363                   a2       LG3   18.62642               1.55000       1.708240   39.12           9.95934               3.00000       1.530190   76.58           −35.01484       Aperture       1.00000           infinity                   a3       LG4   −28.91998               2.10000       1.812659   25.16           −11.51291               1.30000       1.747910   44.57           46.94391                   a4       LG5   159.19894               1.50000       1.708240   39.12           81.58989               2.00000       1.489140   70.99           −229.49361       Infinity       space from       tube lens                  
 
         [0050]     The movement characteristic of the zoom system from  FIG. 11  is shown in  FIG. 12 . It can be seen that the initial magnification value is 0.30 and the final value is 9.00 and the magnification range is accordingly 30.0×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                9.00×   3.31×   0.30×                            a1   69.688   56.490   3.698           a2   2.138   15.336   68.128           a3   63.059   23.234   8.411           a4   1.967   33.862   56.615                      
 
         [0051]     The zoom system according to the invention shown in  FIG. 13  comprises five optical assemblies at a structural length of 180 mm and has the following system specifications:  
                                                                                     Thick-       Index of   Abbe       Plane or   Radius   ness   Variable   refraction   number       lens group   r   d   distance   n e     ν e                                  Infinity                           space from       objective       LG1   54.18919               4.50000       1.530190   76.58           −52.34592               2.30000       1.584820   40.57           −16391.102                   a1       LG2   −29.79285               1.40000       1.747910   44.57           8.12478               2.50000       1.812659   25.16           22.97472                   a2       LG3   19.38349               1.55000       1.708240   39.12           10.35778               3.00000       1.530190   76.58           −36.27659       Aperture       1.00000           infinity                   a3       LG4   −29.29687               2.10000       1.812659   25.16           −12.25144               1.30000       1.747910   44.57           56.73263                   a4       LG5   402.00502               1.50000       1.708240   39.12           147.33917               2.00000       1.489140   70.99           −182.38036       Infinity       space from       tube lens                  
 
         [0052]     The movement characteristic of the zoom system from  FIG. 13  is shown in  FIG. 14 . It can be seen that the initial magnification value is 0.30 and the final value is 10.50 and the magnification range is accordingly 35.0×. Selected magnifications result with the following distance settings:  
                                                                                       Magnification                10.50×   3.54×   0.30×                            a1   69.688   56.613   4.310           a2   2.138   15.213   67.516           a3   83.008   51.170   9.573           a4   2.025   33.862   75.459                      
 
         [0053]     While the foregoing description and drawings represent the present invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the true spirit of the present invention.