Abstract:
The invention concerns a fluorescence (stereo)microscope having a filter carrier that can be loaded with manually exchangeable filter inserts, and having a reliable eye protection system against the energy-rich light radiation in the context of a carrier position without a filter insert.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims priority of the German patent application 102 49 526.2 which is incorporated by reference herein.  
         FIELD OF THE INVENTION  
         [0002]    The invention concerns an eye protection system on an electronically controlled fluorescence microscope.  
         BACKGROUND OF THE INVENTION  
         [0003]    Fluorescence (stereo)microscopes that are equipped with high-output illumination devices which also emit in the ultraviolet spectral region are known. In addition to exclusively UV-protective filters in the observation beam path, further filter combinations are used as excitation filters in the illumination beam path in order to isolate the wavelength(s) necessary for the particular fluorochrome, and as barrier filters in the observation beam path in order to block that same excitation light. These matched filter combinations are preferably incorporated into changeable modules, so that a rapid changeover between different fluorescent excitation illuminations is possible.  
           [0004]    An even faster changeover is made possible by the fact that filter inserts freely selectable by the user are introduced into a magazine switchable in manual or motorized fashion, or into a turret. Positions not loaded with filter combinations must be equipped by the user with so-called “dummies” that interrupt or attenuate the illuminating beam path, in order to prevent damage to the eyes or to an image recording device due to the unfiltered high light intensity.  
           [0005]    Also belonging to the existing art is a mechanical device (blocking slider), described in EP-B1-1 010 030, for interrupting the illumination beam path during breaks in observation. This prevents bleaching of the observed specimens with no need to switch off the illumination device. A shutter, motion-coupled in accordance with EP-B1-1 010 030 to the changeable filter carrier, interrupts the beam path during the switchover, and clears it again in the individual working positions.  
           [0006]    With the apparatuses described above, the microscope user is still not dependably protected from a situation in which a position of the changeable filter carrier not loaded with a filter insert is engaged, and a very high light intensity can travel onto the specimen and into the observer&#39;s eye and an image recording device.  
         SUMMARY OF THE INVENTION  
         [0007]    It is thus the object of the invention to describe an eye protection apparatus that always and reliably protects observers&#39; eyes or an imaging camera or the like. The intention is that upon exchange of the filter inserts, no eye-damaging light is perceptible in and outside the microscope.  
           [0008]    The object is achieved by way of the features of Claim 1, specifically in that as a result of an embodiment according to the present invention, no excitation light emerges from the illumination device if a filter insert is not inserted in the fluorescence microscope.  
           [0009]    In order to improve ergonomics and productivity, a further development provides for electronically controlling, by means of a control unit, the switchover of a filter turret and the illumination duration. Control can be accomplished by means of a special operating unit or via a computer, thereby making possible e.g. automated acquisition of image series with varying fluorescent light excitations. Because of the electrical switchover and the consequent absence of manual contact with the filter turret, however, there is an increased risk that a position of the filter turret loaded neither with a filter insert nor with a dummy will be brought unnoticed into the beam path, and the path then cleared.  
           [0010]    A concrete embodiment of the invention provides that a fluorescence (stereo)microscope having an electronically controlled changeover system between several positions, respectively loaded with excitation and barrier filters, of a magazine (filter turret, changeable filter carrier) for manually insertable filter inserts, is equipped with a shutter, closed in the idle state by a force, in the illumination beam path that can be opened electrically (e.g. by means of a motor or electromagnet) by overcoming the force. Upon interruption of the current flow, this shutter is automatically closed again by the force. In the exemplary embodiment shown, a closing force F is generated by a spring. Mechanical closing of the shutter can, however, also be achieved by the action of gravity, the magnetic force of permanent magnets, or the recovery force of elastic materials.  
           [0011]    For the situation in which, for example owing to operator error, a position without a filter insert is switched into the beam path, danger to the eye (dazzling) as a result of electrical opening of the shutter is prevented, regardless of any electronic functions or malfunctions, by the fact that if no filter insert is present in the beam path, the necessary electrical circuit is automatically interrupted in mechanical or electrical fashion.  
           [0012]    According to the present invention, this is achieved in a particular embodiment by fact that the electrical circuit for electrically opening the shutter and holding it open is closed only by a filter insert present in the beam path, an additional switching device connected in series with this safety device permitting arbitrary closing of the shutter.  
           [0013]    In an exemplary embodiment, a cam on the filter insert actuates a sensitive microswitch with a closing function when the filter insert is present in the beam path.  
           [0014]    Similarly, a permanent magnet on the filter insert can close a magnetic switch (reed contact).  
           [0015]    Further variants are obtained when electrically conductive contact surfaces on the filter holder or on the filters directly close the electrical circuit in the working position.  
           [0016]    Above and beyond its application in fluorescence microscopes and in particular stereomicroscopes, this functional principle can be used wherever a danger to an observer&#39;s eye may exist as result of the absence of components in the optical beam path.  
           [0017]    Further embodiments of the invention are described in the Figures and the Claims. The Parts List, the Figures, and the Claims are thus a constituent of the disclosure. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The invention will be explained in more detail, symbolically and by way of example, with reference to Figures.  
         [0019]    The Figures are described in interconnected and overlapping fashion. Identical reference characters denote identical components; reference characters having different indices indicate functionally identical components.  
         [0020]    In the drawings:  
         [0021]    [0021]FIG. 1 is a schematic plan view of an illumination device according to the present invention of a fluorescence stereomicroscope, having the shutter described;  
         [0022]    [0022]FIG. 2 is a schematic section along A-A in FIG. 1;  
         [0023]    [0023]FIG. 3 is a plan view of a completely loaded filter turret;  
         [0024]    [0024]FIG. 4 shows the coaction between a cam on the filter insert present in the beam path and a sensitive microswitch (closed switch position), viewed in direction B as shown in FIG. 3; and  
         [0025]    [0025]FIG. 5 schematically shows the electrical operating mode. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    [0026]FIG. 1 schematically depicts the construction of an illumination device  1 , illustrating how an illumination beam path with its optical axis  2   a , which proceeds from a light source  22 , would be closed in shutter position  6   a  that is depicted, but open in shutter position  6   b  that is drawn with dashed lines. In the open position, the illumination beam path with its optical axis  2   a  is guided through an aperture  3  and deflected by a deflection prism  4  into an excitation filter  13  (not depicted here) of a filter insert  12  (FIG. 2). A motor with pinion  9  engages into a drive gear  10  on shutter  6  and moves it between stop points  8   b  and  8   c . Shutter  6  is moved in spring-reinforced fashion by means of spring  7 , which is attached to spring suspension  8   a . The spring pulls shutter  6  into closed position  6   a  with a force F.  
         [0027]    Also depicted are UV filters  5   a, b  through which observation beam paths pass, and section lines A-A which indicate the lateral sectioned depiction of FIG. 2.  
         [0028]    [0028]FIG. 2 schematically depicts the construction of a filter turret  11  into which a filter insert  12  is slid. The manner in which illumination beam path  2   b  and one of the observation beam paths  15  (the second is concealed) pass through filter insert  12  is depicted here. Illumination beam path  2   b  is directed by a deflection prism  4  onto an excitation filter  13 . The function of this filter is to block that light wave range in which the fluorescent light perceptible by the observer lies.  
         [0029]    Observation beam path  15  passes through barrier filters  14  (only one of which is depicted; the other is concealed) which limit the incident light wave range only to the desired fluorescent light coming from the specimen, and then, for additional safety, through a respective UV filter  5 , before traveling into the observer&#39;s eyes.  
         [0030]    [0030]FIG. 3 shows a filter turret  11  having filter inserts  12  according to the present invention which are equipped with excitation filters  13  and barrier filters  14  and with cams  19  according to the present invention. The filter inserts are slid in insertion direction  18  onto filter turret  11 , and the latter can be rotated in rotation direction  17  about rotation axis  16 . Directional arrow B indicates the direction from which FIG. 4 must be viewed.  
         [0031]    [0031]FIG. 4 schematically depicts a filter insert  12   a  in the working position, closing sensitive microswitch  20  with a cam  19 .  
         [0032]    [0032]FIG. 5 illustrates the general principle of operation of the electrical circuit. Control device  21  supplies motor  9  with current, to open shutter  6  and hold it open, only when sensitive microswitch  20  is closed by cam  19  of a filter insert  12   a  that is in the working position. When the circuit is closed, motor  9  overcomes force F that closes shutter  6 , and thus holds it open. If the circuit is interrupted by the opening of switch  20 , force F causes shutter  6  to close immediately irrespective of control device  21 ; motor  9 , which is currentless and coupled to the shutter, is also rotated.  
                                         PARTS LIST                                1   Illumination device       2   Optical axis of illumination beam path       3   Aperture       4   Deflection prism       5   UV filter       6a   Shutter (closed)       6b   Shutter (open)       7   Spring       8   Spring suspension and stop points       9   Motor or electromagnet with pinion       10   Drive gear on shutter       11   Filter turret       12   Filter insert       12a   Filter insert in beam path       12b   Filter insert in exchange position       13   Excitation filter       14   Barrier filter       15   Optical axis of an observation beam path       16   Rotation axis of filter turret       17   Motion of filter turret upon switchover between different positions       18   Insertion direction upon exchange of a filter insert       19   Cam on filter insert       20   Sensitive microswitch with closing function       21   Control unit       22   Light source       F   Force       B   Viewing direction for FIG. 4