Abstract:
A microscope includes a lens holder for receiving a lens. A locking device is provided that affixes the received lens so that the lens cannot be removed without authorization.

Description:
The invention relates to a microscope having a lens holder into which lenses can be inserted. 
   The invention also relates to a locking device for a lens holder into which the lenses can be inserted. 
   BACKGROUND 
   Most commercially available microscopes are designed in such a way that, depending on the requirements of the preparation to be examined, different lenses can be inserted into the optical path. For this purpose, there is a thread into which different lenses can be screwed. Microscopes often comprise means in which several lenses are screwed in or stored and which allow a simple insertion of the lenses into the optical path of the microscope. Devices of this type are usually configured as lens turrets. 
   Microscopes with lenses that can be screwed out and that are fitted with a laser such as, for instance, laser scanning microscopes or microscopes with a laser device for specimen manipulation entail the disadvantage that hazardous laser radiation might escape in an undesired and uncontrolled manner if the lens is inadvertently removed. 
   Microscopes with interchangeable lenses also have the drawback that the relatively small, although usually expensive, lenses can be easily removed or can be easily lost. This aspect is of particular relevance in the case of microscopes employed in schools. 
   Japanese patent JP 2000221408 A2 discloses a lens turret with a cylindrical protective ring that is affixed with screws and that encompasses all lenses, thus making unauthorized removal more difficult. The protective ring, however, greatly limits the space around the lenses, which has a very detrimental impact when it comes to bringing laboratory devices such as, for example, manipulators or micropipettes, close to the specimen. Besides, authorized replacement of the lenses can only be carried out with considerable effort, namely, by dismantling the specimen stage or the microscope stand. 
   SUMMARY OF THE INVENTION 
   Therefore, it is an object of the present invention to provide a microscope which largely prevents loss of the lenses and, if a laser is an integral part of the microscope, also prevents the uncontrolled release of laser radiation while still allowing full utilization of the microscope. 
   The the present invention provides a microscope including a lens holder for receiving a lens, and a locking device. The locking device affixes the received lens so that the lens cannot be removed without authorization. 
   Another objective of the invention is to provide a locking device for a lens holder which largely prevents the loss of the lenses while still allowing full utilization of the microscope. 
   The present invention also provides a locking device for a lens holder in which a lens can be received. The locking device includes an affixing device for affixing a lens received by the lens holder so that the lens cannot be removed without authorization. 
   The invention entails the advantage that it prevents the loss or theft of the lenses. Moreover, the invention has the advantage that it prevents the release of hazardous laser radiation from microscopes that are fitted with lasers. 
   In a preferred embodiment, the locking device affixes the inserted lenses in such a way that they can only be removed using a tool, the latter preferably being a special tool. 
   In another embodiment, the lens holder has a thread into which the lenses can be screwed, whereby the locking device prevents the screwed-in lens from turning inside the thread. The locking device comprises at least one screw, preferably a stud, which blocks the thread by a locking action. 
   In another embodiment, the locking device comprises a lock. 
   Another embodiment is characterized in that the locking device only allows the lens to be removed after executing a certain clockwise or counterclockwise turning combination by a predefined angle. For this purpose, there is preferably a catch mechanism into which the lens latches after it has been rotated by a definable angle. 
   In a very particularly preferred embodiment relating to microscopes having a light source, especially lasers, said light source can be automatically switched off, shielded, or blocked by removing the lens. 
   In another embodiment, electronic circuitry is provided that releases the locking device only after a secret code has been entered, for instance, via a keypad present on the device, via a remove control or via computer input. With this embodiment, instead of studs, electromagnetically sliding blocking pins are provided as part of the locking device. 
   In a preferred embodiment, a coin receptacle is provided that only releases the locking device once a deposit coin has been inserted; there is preferably a separate coin receptacle for each lens. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawing schematically depicts the subject matter of the invention and will be described below with reference to the figures, whereby elements having the same function are designated with the same reference numerals. The following is shown: 
     FIG.  1 —a microscope according to the invention which is configured as a laser scanning microscope; 
     FIG.  2 —a section through the lens turret of a microscope according to the invention; 
       FIG. 3   a —a locking device according to the invention in the unlocked state; 
       FIG. 3   b —a locking device according to the invention in the locked state; and 
     FIG.  4 —a locking device according to the invention in a locked state. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a microscope according to the invention which is configured as a laser scanning microscope. The device is controlled by means of a PC  27 . A monitor  29  that serves to display the image of the specimen  11  and to show the selected microscope parameters is connected to the PC  27 . The system parameters are selected by means of the panel box  31  that has individually definable knobs  33  and by means of the keyboard  35 . For focusing purposes, the specimen stage  13  on which the specimen  11  is positioned can be moved vertically by turning the adjusting knob  10 . The specimen is essentially scanned with the scanner  2 . A laser serves as the light source  1 . The scanner  2  is flanged onto the microscope stand  25 . The illumination light beam  3  coming from the light source  1  is reflected by a beam splitter  7  towards the gimbal-mounted scanning mirror  9  that guides the illumination light beam  3  through the lens  23  over or through the specimen  11 . In the case of a non-transparent specimen  11 , the illumination light beam  3  is guided over the surface of the object. With biological specimens  11  or with transparent specimens  11 , the illumination light beam  3  can also be guided through the specimen  11 . This means that several focal planes of the specimen  11  can be consecutively illuminated by the illumination light beam  3  and thus scanned. The subsequent composition then yields a three-dimensional image of the specimen  11 . The illumination light beam  3  coming from the light source  1  is shown in the drawing as a dotted line. The detection light  15  emitted by the specimen  11  passes through the lens  23  and via the scanning mirror  9  to reach the beam splitter  7 , it then passes through the latter and strikes the detector  19 , which is configured as a multiband detector. The detection light  15  emitted by the specimen  11  is shown as a broken line. Electric detection signals that are proportional to the output of the illumination light  15  emitted by the specimen  11  are generated and further processed in the detector  19 . For the sake of completeness, the illumination pinhole  5  commonly found in a confocal scanning microscope as well as the detection pinhole  17  have also been drawn in schematically. On the other hand, a few optical elements that serve to guide and shape the light beams have been omitted for the sake of clarity. These elements are quite familiar to the person skilled in the art. The lens turret  21  is configured in such a way that several lenses  23  can be screwed in at different affixed positions. After being screwed in, the lenses can be affixed in their holder by means of moveable magnetic pins. Each individual lens holder is provided with a special secret code that should only be known to the user. After the special secret code has been entered, the locking device is released and the user can remove from the lens turret  21  the lens  23  that she/he has specified. The device offers several different possibilities for entering the secret code. When an attempt is made to unscrew a certain lens  23  from its holder, a signal is sent to the PC  27  via the control line  26 . Then, via the monitor  29 , the PC  27  generates a prompt for the user to enter the special secret code for this holder. Only once the code has been entered via the keyboard  35  is it possible to remove the lens  23  from its holder. The secret code can also be entered directly by the user by means of the remote control  37 . Another possibility consists of using the panel box  37  on which there is a knob  33  having a scale  34 . After the prompt to enter the code has been generated on the monitor  29  by the computer  27 , the user can release the locking device and subsequently remove the lens  23  after executing a certain clockwise and counterclockwise turning combination by predefined angular positions. 
     FIG. 2  shows a section through the lens turret  21  of a microscope according to the invention. A plurality of lens holders  39  can be seen in the lens turret  21 , whereby each lens holder  39  has a thread  40  into which a conventional lens  23  or a dummy can be screwed. Here, each lens holder  39  is additionally provided with a thread  41  for a locking screw. 
     FIG. 3  shows a locking device according to the invention.  FIG. 3   a  depicts a locking device according to the invention prior to the locking (unlocked state). An enlarged section of the lens turret  21  can be seen with a lens holder  39  and with the thread  40  into which the lens  23  can be screwed. Moreover, the thread  41  for placing a locking screw is shown. Matching the thread  41 , there is a screw  45  configured as a stud. This is a specially designed stud that can only be screwed into and out of the thread  41  with a special tool  47  that has a special screw head  49 . Furthermore, the lens holder  39  has a clamp  43  designed as a leaf spring. 
     FIG. 3   b  illustrates how the locking mechanism works (locked state). After the screw  45  has been inserted and carefully screwed into the thread  41  using the special tool  47 , the clamp is actuated. This causes a threaded leaf spring to be pressed against the outer thread of the lens. In this context, the screw  45  and the clamp  43  have to be actuated in such a way as not to cause any damage to the outer thread of the lens. The locking device can be subsequently released only by means of the special tool  47 . 
     FIG. 4  shows a locking device according to another embodiment of the invention in a locked state. In this embodiment a locking pin is provided in the form of moveable magnetic pin  51 . As discussed above, after being screwed in, the lenses can be affixed in their holder by means of a respective moveable magnetic pin  51 . After a special secret code has been entered, the locking device is released and the user can remove from the lens turret  21  the lens  23  that she/he has specified. 
   The invention was described with reference to an embodiment. Of course, changes and modifications can be made without departing from the scope of protection of the claims presented below. 
     1  light source
       2  scanner     3  illumination light beam     5  illumination pinhole     7  beam splitter     9  scanning mirror     10  adjusting knob     11  specimen     13  specimen stage     15  detection light     17  detection pinhole     19  detector     21  lens turret     23  lens     25  microscope stand     26  control line     27  PC     29  monitor     31  panel box     33  knob     34  scale     35  keyboard     37  remote control     39  lens holder     40  thread     41  thread     43  clamp     45  screw     47  special tool     40  screw head     51