Abstract:
The invention relates to a microscope comprising a microscope housing ( 18 ), an optics system ( 16 ) consisting of at least one lens system that contains at least one respective lens ( 48 ) and is positioned at one end of a passage ( 19 ) of the microscope housing ( 18 ), at least one observation device, in particular an ocular, located at the other end of the passage ( 19 ), an illumination device, whose light forms at least one illumination beam ( 44 ), originating from a plane of incidence ( 45 ) that vertically intersects the passage ( 19 ), said beam traversing the lens system and striking an object carrier ( 36 ) at a predetermined angle (β). According to the invention, the illumination beam or beams ( 44 ) originating from the plane of incidence ( 45 ) is/are provided by an optical device, whose cross-section lying in the vicinity of the passage ( 19 ) is substantially smaller than the cross-section of said passage ( 19 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a 35 USC § 371 National Phase Entry Application from PCT/EP02/09901, filed Sep. 4, 2002, and designating the U.S. 
   BACKGROUND OF THE INVENTION 
   This invention relates to a microscope. More particularly, this invention relates to a microscope which includes a housing, an optics system having at least one lens system which includes at least one lens, at least one observation device and an illumination device producing at least one illumination beam that strikes a microscope slide at a predetermined angle. 
   Such a microscope is known ( Biochemical and Biophysical Research Communications,  235, 47–53). It is used primarily for the microscopy technique known by the acronym TIRM (=total internal reflection microscopy). In this technique, the illumination beam is totally reflected at an interface formed between the microscope slide and the object (the refractive index of the microscope slide is greater than the refractive index of the object), wherein the illumination beam traverses the microscope slide, so that an evanescent light field originating from the point of reflection penetrates into the object, with the intensity declining exponentially. This light field is used for strictly locally delimited illumination of areas of the object near the microscope slide. These areas may then be examined in the usual way through the optics system and the observation device, e.g., an ocular or a camera. 
   In one of two possible TIRM configurations, the object is on the side of the microscope slide facing the microscope with a corresponding guide for the illumination beam in the manner of a back-lighting configuration (see, for example,  Nature , vol. 374, pp. 555–559 or  Topics in Fluorescence Spectroscopy , vol. 3, ed. by J. Lakowicz, Plenum Press, New York, 1992, p. 314 ff.). The alternative reflected light arrangement, in which the object is situated on the side of the microscope slide facing away from the microscope, is used in the related art cited in the preamble. The illumination light here emanates from a laser outside of the passage in the microscope and is directed via a mirror system at a dichroic beam splitter mirror in the passage and then follows the path of the observation beam in parallel with the optical axis through the optics system (objective) to the microscope slide and the object. The dichroic mirror interferes with microscopic observation of the object because it passes through the entire cross section of the passage and thus weakens the light beam observable through the ocular in a ratio that depends on the wavelength. 
   SUMMARY OF THE INVENTION 
   The object of this invention is to provide a microscope of the type defined in the preamble so that it causes the least possible impairment in microscopy possibilities, in particular with regard to the possible wavelengths of the illumination light and/or the observation light. 
   This object is achieved by the fact that said at least one illumination beam emanating from said plane of incidence is provided by an optical device whose cross section in the area of said passage is much smaller than the Gross section of said passage. 
   The position of the plane of incidence may be selected as desired in the passage between the front lens of the optics system (objective) and the observation device, with lateral coupling into the front lens also being possible. Due to the fact that the illumination light is concentrated on at least one illumination beam, locally limited beam guidance elements may be used accordingly, which cause only minor impairment in the observation beam path of the microscope (usually outside of the optical axis). This fine illumination beam may be passed through the lens system traversed by the beam (optionally the front lens) of the optics system without requiring any additional measures. In particular, for coupling of the illumination light it is possible to omit the use of any beam splitting equipment extending through the passage. 
   A light source for the illumination light might be, for example, a laser which emits an illumination beam bundle of parallel individual beams with an essentially spot-shaped beam cross section. However, it is preferred that in the focal plane facing the observation equipment hereinafter also referred to as the back focal plane, of the lens system traversed by the beam of the optics system said at least one illumination beam is virtually or actually focused at the point. This achieves the result that the illumination beam emitted from the point in the focal plane as a divergent beam bundle is formed by a beam bundle of individual beams running in parallel after passing through the lens system, all of the individual beams meeting the condition of total reflection equally. 
   The illumination beam could in principle also pass through the lens system of the optics system at an inclination to the optical axis. However, it is preferable for the at least one illumination beam to run essentially parallel to the optical axis through the lens system traversed by the beam of the optics system. The illumination beam here may fall outside of the optical axis as well as along the optical axis through the lens system traversed by the beam of the optics system. The greater the distance from the optical axis in the radial direction where the illumination beam strikes the lens system of the optics system, the greater is the angle of reflection of the illumination beam at the interface between the microscope slide and the object. To meet the condition of total reflection, one would therefore preferably select an arrangement in which the illumination beam runs near the edge of the aperture diaphragm of the optics system through the lens system traversed by the beam of the optics system. A special application is obtained when the illumination beam traverses through the lens system traversed by the beam of the optics system at the center of the passage along the optical axis. In this case, the illumination beam strikes the interface between the microscope slide and the object essentially at a right angle, so that it is reflected back into the microscope along the same path. In this way it is possible to implement a microscope having a reflected light configuration in which the light reflected back from the object can be observed without having to use beam splitter equipment which would interfere with the observation light, because only a small area at the center of the field of vision of the microscope is included with the device providing the illumination beam 
   In an especially preferred embodiment, the at least one illumination beam is displaceable in the radial direction with respect to the optical axis. The lateral displacement can be implemented through technically simple means, in particular through deflector mirrors, deflector prisms or the like, all of which are displaceable in the radial direction (with respect to the optical axis). A displacement in the radial direction leads directly to a corresponding change in the angle of reflection at the interface between the microscope slide and the object. The total reflection angle, which varies from one case to the next (depending on the refractive indices of the microscope slide and the object) can be adjusted in any desired manner. In addition, the depth of penetration of the light field into the object behind the interface on which the total reflection occurs depends on the angle of incidence of the light beam. The depth of the illuminated object volume can thus be altered by radial displacement of the illumination beam. In addition, the depth of the illuminated volume can also be varied by choosing illumination light of a different wavelength. Since the inventive microscope allows the use of illumination light of any wavelength, a continuous variation in the illuminated object volume is also possible in this way. A targeted change in the illuminated object volume and observation of the intensity of the light emitted by this volume can be utilized for example, to determine the size of an object in the area of this object volume, because the depth of penetration of the illumination light can be calculated from its wavelength and the total reflection angle set (see in this regard, for example,  Topics in Fluorescence Spectroscopy , vol. 3, Plenum Press, New York, 1992, pp. 289 ff.). 
   Furthermore, it is proposed that the angle of divergence of the at least one illumination beam emitted from the plane of incidence shall be variable. A change in the angle of divergence results in a corresponding change in the cross section of the illumination beam emitted from the lens system and thus also a change in the size of the illuminated area in the object. 
   The angle of divergence can be varied according to the invention by adjusting an aperture diaphragm in the beam path of the illumination beam or by varying the focal depth of the optical unit focusing the illumination beam in the back focal plane. 
   If an as uniform as possible illumination of the object is required, then preferably an incoherent illumination beam is used. However, if an increased positional resolution and/or structured illumination is desired, then preferably one or more essentially coherent illumination beams is used, with the possibility of interference in the area of the object. 
   If the object to be observed is in the area of the optical axis, as is generally the case, the totally reflected component of the illumination beam is then reflected back into the optics system, at least when the microscope slide is arranged perpendicular to the optical axis. Normally, with TIR microscopy, fluorescent light is observed emanating from the illuminated part of the object and containing information about the object. In order not to interfere with microscopic observation of the object, the portion of the illumination beam reflected back, i.e., the reflected beam, is absorbed according to this invention, preferably through an absorber or a filter directly downstream from the lens system traversed by the beam. Alternatively or additionally, the reflected beam may also be detected, whether for adjustment of the arrangement, in particular for adjusting the total reflection angle, and/or for absorption measurements on the object. A detection device may be provided in the area of the passage for this purpose. Through the observation of absorption processes at the interface between the microscope slide and the object as a function of the wavelength of the illumination beam used, additional information about the object can also be obtained from the reflected beam. It is important in particular here that light of any wavelength can be observed, as is the case according to this invention. 
   Greater freedom in the configuration and design of the detection device are obtained when the reflected beam is guided out of the microscope beam path by means of a deflecting unit in the area of the passage. A corresponding deflecting unit may also be provided for coupling of the illumination beam into the microscope. Here again, the advantage of a greater freedom in the arrangement and design of the light source and the beam guidance is achieved by means of corresponding optical systems of the illumination device. Nonetheless it may be advantageous in certain situations, e.g., when not enough room is available for external light sources, to place a light source with a spot-shaped cross section if possible, e.g., a laser diode, directly in the passage in the area of the plane of incidence. 
   In a first embodiment of this invention, the deflecting unit includes a prism. Deflection is then accomplished by total reflection on one of the prism faces. The prism causes very little interference with the observation field of the microscope. It can be held and mounted in a simple manner. A movable mount for adjusting the beam path, in particular for adaptation of the reflection angle by displacement in the radial direction, can be implemented with little structural complexity. Thus, for example, it is possible to use a rod prism having a deflection prism face in the passage with linear movement guidance and mounting outside of the passage. 
   Prisms are available in different shapes and designs, depending on the desired specifications. A 90° prism is used in the basic version. The prism may be rounded so as to interfere with the field of observation as little as possible. Instead of the 90° configuration, other angles may also be selected. Coupling an optical lightguide to a deflection prism offers special advantages with regard to flexibility in introducing the illumination beam. 
   In cases in which dispersion of the illumination beam is to be prevented or the wavelength of the illumination beam is varied, then instead of the prism, a deflecting mirror may also be used. In general, a planar deflecting mirror will be used. However, it is also conceivable to use a curved mirror, which can be useful in focusing the beam in the back focal plane, so that corresponding lens elements may be omitted. 
   In the inventive configuration, at least one illumination beam is used, and a plurality of illumination beams may also be used, depending on the particular requirements. In such a case, a deflecting unit in which a corresponding plurality of deflecting units is structurally integrated is also used to advantage. In this case, the deflecting unit is preferably designed to be approximately ring-shaped and is arranged so that it is concentric with the optical axis. Suitably inclined reflection surfaces (mirror surfaces and/or prism surfaces) are provided on this ring in addition, it is also possible to introduce the illumination beam into the beam path of the microscope by using a curved optical lightguide. In this case the deflecting unit is formed by the curved optical lightguide itself. 
   The configuration according to this invention, comprising individual illumination beams, in particular a single illumination beam, makes it possible to illuminate the object with an illumination beam coming from a single direction. In the case of designs having a complex three-dimensional structure, such as cells, different images of the object may be obtained, depending on the angle of incidence of the illumination beam. This provides additional information regarding the object. Therefore in such a case, it may be advantageous if, as proposed according to this invention, the at least one deflecting unit or the light source (if a light source is situated in the passage) is able to rotate about the optical axis. To detect or absorb the reflected beam, it is also expedient to rotate the detection device and/or the absorption device about the optical axis, if necessary. 
   Rotation of the deflecting unit and thus rotation of the illumination beam striking the specimen may be performed between measurements, as mentioned above, or even during a measurement in order to obtain uniform illumination of the object. 
   Since the illumination light is coupled into the microscope only in the area of the optics system via the at least one deflecting unit according to this invention and if necessary is also output again there, the light that serves to illuminate the object and is not part of the reflected beam and nevertheless is reflected and/or scattered back into the microscope can be removed easily from the observation beam path, namely by a filter arrangement on the side of the at least one deflecting unit that is remote from the object. 
   The restriction on the beam guidance of the illumination beam according to this invention as well as that of the reflected beam to the optics system area permits the use of an adapter, which is situated between the optics system and the observation device and has at least the one deflecting unit or the one light source, if necessary. With the help of the adapter, it is readily possible to couple the light source of the illumination device, wherein the light source (in the case when it is not situated in the passage) may be independent of the adapter or may also be integrated into the adapter. The adapter can optionally be removed again or replaced by other adapter devices, which allows versatile use of the microscope. Existing microscopes can be upgraded or modified by replacing adapter inserts that are traditionally present, in particular so-called DIC (differential interference contrast) sliders which have optical components that are used for DIC microscopy, with an adapter according to this invention. Another simple possibility of modifying existing microscopes is provided by an adapter situated between the optics system and the optics system connection of the microscope housing. Ideally such an adapter has a connection on its side facing the optics system similar to the optics system connection of the microscope housing into which the optics system normally fits. In addition, it is advantageous if the adapter has a similar connection on its side facing the microscope housing like the connection of the optics system facing the microscope housing. In this case, the adapter can easily be inserted into the passage between the optics system and the microscope housing without having to modify an existing microscope, because in a microscope, the length of the passage between the observation device and the connection of the microscope housing on the optics system end can usually be varied. 
   It is even possible to integrate the deflecting unit into a suitably adapted optics system. The optical components can thus be optimally coordinated. Furthermore, no other modification of the microscope is necessary, because one need only replace a traditional optics system with an optics system according to this invention. 
   In addition to the deflecting unit, the light source and/or the detector unit for the reflected beam may also be integrated into the adapter box and/or the optics system according to this invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This invention is explained below on the basis of several exemplary embodiments with reference to the drawing, showing: 
       FIG. 1  a roughly schematic sectional diagram of a microscope having a reflected light configuration and an adapter, the adapter being indicated with dotted lines; 
       FIG. 2  a detailed view (arrow A) of the configuration in  FIG. 1  with an embodiment of an adapter designed according to this invention and an external light source (not shown); 
       FIG. 3  a view according to  FIG. 2  of a modified adapter with an internal light source; 
       FIG. 4  a sectional view like those in  FIGS. 2 and 3  of another embodiment of the adapter together with the optics system, omitting the other microscope components and including a prism as the deflecting unit; 
       FIG. 5  a section of the configuration according to  FIG. 4  according to line V—V in  FIG. 4 ; 
       FIG. 6  a section like that in  FIG. 4  through another embodiment of the adapter, omitting a part of the adapter that is remote from the object and having a mirror as the deflecting unit; 
       FIG. 7  a view like that in  FIG. 6  shows another embodiment of the adapter with a curved mirror as the deflecting unit; 
       FIG. 8  a greatly simplified perspective schematic view of a deflecting unit of concentrically arranged deflecting elements arranged in a ring together with the lens system, represented by a single lens, and the microscope slide with the object and the beam path indicated; 
       FIG. 9  a view like that in  FIG. 6  with a prismatic deflecting element and an optical lightguide connected; 
       FIG. 10  a view like that in  FIG. 9  with a deflecting element formed by a curved section of an optical lightguide, 
       FIG. 11  a sectional view with a deflecting unit in the form of a rod prism integrated into the optics system; 
       FIG. 12  a configuration like that in  FIG. 11  with a deflecting unit in the form of a double prism integrated into the optics system; 
       FIG. 13  a view like that in  FIG. 11  with an optical lightguide connected to the rod prism, and 
       FIG. 14  a configuration like that in  FIG. 13  with a curved section of optical lightguide as the deflecting unit. 
   

   DETAILED DESCRIPTION 
   The schematic sectional drawing according to  FIG. 1  shows a traditional microscope in an inverted configuration (Carl Zeiss Axiovert 100, 135, 135M, Carl Zeiss Jena). The main parts of the microscope, which is labeled as  10  in general can be seen here, namely a visual observation part  12  with an ocular  14  at one end of the beam path and an optics system (objective)  16  on the other end and a plurality of optical components inserted in between within a passage  19  of a microscope housing  18 . The beam path of a photographic observation part with a camera  22 , the outline of which is shown here, can be coupled into the beam path. 
   Furthermore, the beam path of an illumination part  24  can be coupled into the visual beam path (via a partially transparent mirror  26  beneath an optics system revolver head  28  which carries the optics system  16  with the axis of rotation  30  of the revolver). 
   With the traditional microscope  10 , an adapter receptacle  32  (indicated with dotted lines in  FIG. 1 ) is provided, serving to accommodate adapters (DIC sliders), in particular a Wollaston prism for observation of objects in differential interference contrast. 
   In  FIG. 1 , a microscope slide (omitted in  FIG. 1 ) for the object to be observed with the microscope is connected to the optics system  16  at the top. In the arrangement shown here, the object is illuminated by the illumination part from the observer&#39;s side. If transillumination of the object is desired, then an illumination part (not shown in  FIG. 1 ) for a corresponding illumination of the sample (from above in  FIG. 1 ) may be arranged on a mount  34  which protrudes upward from the microscope  10  and is shown in a cutaway view in  FIG. 1 . 
   The area of the revolver head  28  indicated by the circular area A in  FIG. 1  is shown in  FIG. 2  together with the microscope slide  36  and the object  38  on its top side (side of the microscope slide  36  formed by a glass slide facing away from the optics system  16 ). 
   An adapter  40  according to this invention is inserted instead of a traditional adapter into the receptacle  32 . This adapter  40  can thus be used without further modification of the known microscope  10 . It is used to illuminate the object  38  according to the essentially known principle of TIR (total internal reflection) microscopy. 
   In this microscopy technique light, coming from the microscope slide side is totally reflected at an interface  42  formed between the microscope slide  36  and the object  38  (refractive index of the object lower than the refractive index of the microscope slide). A so-called evanescent illumination field extends from the total reflection point into the object, declining exponentially with the distance from the interface. This yields a type of illumination which is very sharply delimited locally in the axial direction. To obtain the total reflection angle, an optics system having a sufficiently high numeric aperture NA is used. For example, in the case of a glass-water interface, an optics system with a high numeric aperture (NA&gt;1.33) must be used to obtain the total reflection angle. 
   The depth of penetration of this field depends on the particular reflection angle β (which continues to obey the total reflection condition). Accordingly, by varying the reflection angle β the depth of illumination can also be varied. 
   According to this invention, an illumination beam  44  having a greatly limited cross section is used. The limitation is such that it essentially forms a spot in the back focal plane  46  of the optics system  16 . This refers to the focal plane which corresponds to the lens system of the optics system  16  through which the illumination beam  44  passes (indicated by a single front lens  48  in  FIG. 2 ). Therefore, depending on the design of the optics system  16 , other lenses or lens systems of the optics system  16  may also be situated downstream from the coupling point (prism  50 ) of the illumination beam  44  (in the direction of the ocular). 
   When using a precision laser beam as the illumination beam  44 , it can be passed through the lens system on the front (represented by the front lens  48 ) without using focusing lenses, although a weak divergence of the beam emitted from the front lens is unavoidable, because the partial beams which are still parallel in front of the front lens then converge in the form of rays toward the focal point F. Accordingly, the reflection angles of these partial beams differ slightly from one another. In many cases, this may be acceptable. 
   Theoretically absolute parallelism of the partial beams after passing through the front lens  48  of the optics system is obtained when the illumination beam is focused into the back focal plane  46  (on the ocular end) with the help of corresponding optical elements (indicated by a lens  52  in  FIG. 2 ). Then after the beam passes through the front lens  48 , this necessarily results in parallel partial beams of the illumination beam  44  with a joint reflection angle β corresponding to the distance A of the partial beam  44  from the optical axis  54  of the optics system  6 . The degree of divergence of the illumination beam  44  after passing through the front lens  48  is determined by the divergence angle α of the illumination beam  44 , which is focused in the back focal plane  46 . 
   With the help of the prism  50  mentioned above, the illumination beam coming from an illumination source (not shown; left of the revolver head  28  in  FIG. 2 ) is deflected at a right angle so that it runs parallel to the optical axis  54  and at a distance a from it. The cross section of the prism  50  in the passage  19  is significantly smaller than the total cross section of the passage  19 . For this reason, it is not necessary to use a beam splitter such as a dichroic mirror which allows transmission of the observation light coming from the object for coupling of the illumination beam because only a small portion of the observation field of the microscope is covered by the prism  50 . The distance a may be varied according to this invention in an especially simple manner by shifting the prism  50  either in the direction parallel to the optical axis  54  or, as depicted here, in the radial direction (double arrow B). The reflection angle β of the illumination beam  44  changes with the distance a, and thus after exceeding the total reflection angle, the depth of penetration into the object also changes. In order for the focus of the illumination beam  44  to still be in the focal plane  46  after displacement of the prism  50 , the position of the optical components provided in the beam path (represented by the lens  52 ) must accordingly be adjusted. If, as shown in  FIG. 2  the illumination beam is deflected at a right angle, it is particularly advantageous to mount the deflecting unit and the optical elements which permit focusing on a shared mount because only this mount need be displaceable in the radial direction. 
   In the arrangement shown in  FIG. 2  with the interface  42  at a right angle to the optical axis  54  between the microscope slide  36  and the object  38 , the illumination beam again passes through the front lens  48  into the optics system  16  (symmetrical with the illumination beam  44 ) after being reflected on the interface  42  (now called the reflected beam  56 ). In order for the reflected beam  56  not to interfere with microscopic observation of the object  38 , it is absorbed by an absorber  58  in the embodiment according to  FIG. 2 , said absorber being situated here on the other side of the optical axis  54  at a location corresponding to the location of the prism  50 . To interfere with microscopic observation as little as possible, the absorber  58  may be moved radially outward as much as possible; as indicated by the double arrow B′. 
   The aperture diaphragm  60  in front of the lens  52  should also be mentioned, because the aperture diaphragm limits the beam cross section of the illumination beam  44  and thus via the divergence angle α determines the degree of divergence of the illumination beam  44  after the beam passage through the front lens  48 . Another possibility of varying the divergence angle α consists of varying the focal depth of the lens  52 , in which case then the position of the lens  52  (see double arrow D) and optionally the joint position of lens  52  and prism  50  must then be readjusted in the axial direction (see double arrow E) so that the illumination beam is still focused in the back focal plane  46 . 
   In case of need, the adapter  40  can be removed from the receptacle  32  again and optionally replaced by a conventional adapter. Furthermore, the adapter may also easily be used in combination with any other optics systems of the revolver head  28 , because a receptacle  32  is usually assigned to each optics system. 
   With regard to the optical structure, it should also be added that an additional aperture diaphragm  62  (indicated beneath the prism  50  in  FIG. 2 ) may also be used in the passage  19  between the coupling point of the illumination beam (prism  50 ) and the observation device. This aperture diaphragm removes the prism  50  from the observation beam path and thereby prevents any interfering asymmetrical diffraction images (image distortion) of the object due to the prism  50  introduced into the illumination beam path. The slightly reduced numeric aperture and resolution are then acceptable. 
   Another variation in the type of illumination of the object  38  can be achieved if the prism  50  together with the optical components (lens  52 ) connected in front is shifted in parallel with the optical axis  54 . If the focus then moves out of the back focal plane  46 , the result is a certain divergence of the beam striking the interface  42  and a change in the degree of divergence. 
     FIG. 3  shows another embodiment (labeled as  140 ) of the adapter  40  according to  FIG. 2 . Accordingly, the other components, inasmuch as they correspond to components of the adapter  40 , are provided with the same reference numbers, but each has the number  100  added to it. 
   In contrast with the adapter  40  having the external light source, the light source  164  with the adapter  140  is integrated into the adapter  140 . The lens  152  and the prism  150  are connected thereto. After passing through the front lens  148  of the optics system  116  and after total reflection at the interface  142 , the illumination beam  144  and/or the reflected beam  156  is deflected by 90° through another prism  166  (diametrically opposite the prism  150  together with the light source  164 ) and is captured in a detector  170  after passing through a lens  168 . With the detector  170 , the optical arrangement can now be adjusted in a targeted manner; in particular, the total reflection angle can be adjusted as a function of the position of the prism  150  and a desired range after exceeding the total reflection angle can be set. On the other hand, under some circumstances local changes in refractive index, absorption processes or the like can be detected in the area of the interface  142 . Variation of the wavelength of the light of the light source  164  is also conceivable here. 
   The radial adjustability of the prisms  150 ,  166  is indicated by the double arrows B and B′; the mobility of the prisms  150  and  166  together with the light source  164  and the lens  152  and/or the detector  170  and the front Jens  168  in parallel with the optical axis  154  is indicated by the double arrows E and E′; the adjustment mobility of the lenses  152 ,  168  is indicated by the double arrows D, D′. 
   In principle, it is also conceivable to design the adapter  140  so that it can optionally be rotated about the optical axis  154 . This offers the advantage that in the case of objects having anisotropic optical properties, the incident beam direction of the observation beam  144  may optionally be varied. Uniform illumination of the object can also be achieved optionally by rotation during the measurement. 
     FIGS. 4 and 5  show another embodiment of the inventive adapter, now labeled as  240 , shown here in a side view and a sectional view. Its components, which correspond in function to those in  FIG. 3 , are labeled with the same reference numbers, each increased by  100 . 
   Here again, the prisms  250 ,  266  with the lenses  252 ,  268  connected in front are provided for coupling of the illumination beam  244  and/or for output of the reflected beam  256 . In contrast with the embodiment according to  FIG. 3 , the reflected beam  256  is guided out of the adapter  240  and sent to a detection device (not shown here). The light source (also not shown here) is outside of the adapter  240  (in accordance with  FIG. 2 ). The adjustment options are the same here as those in the embodiment according to  FIG. 3 , which is indicated by the corresponding double arrows D,D′, B, B′ and E, E′. 
   The adapter  240  is situated between the optics system  216  and the revolver head  228 . On its side facing the optics system, it has a connection  290 , which corresponds to the optics system connection  292  of the revolver head  228  into which the optics system  216  is normally inserted. On its side facing the revolver head  228 , the adapter  240  has a connection  286 , which corresponds to the connection  288  on the ocular end of the optics system  216 , which is normally fitted into the optics system connection  292  of the revolver head  228 . In this way, the adapter  240  can easily be integrated into an existing microscope without having to modify the microscope. 
   The two prisms  250 ,  266  have rounded reflective surfaces so as to interfere with microscopic observation as little as possible (see  FIG. 5 ). In addition, a filter wheel  272  with an axis of rotation  274  in the observation beam path is situated in the adapter  240  on the side of the prisms  250 ,  266  facing away from the object  238 . Thus, for example, the portions of the illumination beam  244  which are not output as reflected beam  256  out of the adapter  240  (in particular diffusely scattered fractions), can be filtered out of the observation beam path. This is advantageous in fluorescence measurements in particular. 
   The embodiment of the inventive adapter shown in  FIG. 6  is labeled as  340 . It differs from the embodiment according to  FIGS. 4 and 5  only in that the prisms  250 ,  266  have been replaced by planar mirrors  350 ,  366 . The total reflection angle can be varied in the same way when using a prism due to the displacement of the mirror  350  in a direction perpendicular to the optical axis  354  (while retaining the three-dimensional orientation). 
   In the embodiment labeled as  440  of the adapter according to  FIG. 7 , the two planar mirrors  350 ,  366  according to  FIG. 6  have been replaced by curved mirrors, in particular concave mirrors, also called concentrating reflectors  450 ,  466 . Under some circumstances, coupling and focusing of the illumination beam  440  can be accomplished according to the exemplary embodiments described above without requiring other optical elements such as a front lens. Beam guidance of the reflected beam  456  through the mirror  466  is accomplished symmetrically here. 
   In a highly simplified, perspective, schematic view,  FIG. 8  shows a deflecting unit  576  which is used for coupling of a plurality of illumination beams  544 ,  544 ′,  544 ″,  544 ′″ and for output of the corresponding reflected beams  556 ,  556 ′,  556 ″,  556 ′″. 
   The deflecting unit  576  consists of a concentric arrangement of deflecting elements held together in the shape of a ring, depicted in  FIG. 8  as trapezoidal mirrors  550 ,  550 ′,  550 ′,  550 ″,  566 ,  566 ′,  566 ″,  566 ′″. An illuminating beam, e.g., labeled with the reference number  544 , is reflected here on the particular deflecting element, e.g.,  550 , so that it runs parallel to the optical axis  554  after reflection and is imaged by the optics system  548  on the microscope slide  536  with the object  538 . The illumination beam, e.g.,  544  totally reflected at the interface between the microscope slide  536  and the object  538  strikes the deflecting element, e.g.,  566  as a reflected beam, e.g.,  556  after passing through the optics system  548  again in parallel with the optical axis  554 , and is reflected again at the deflecting element, so that it is output out of the beam path of the microscope. With the arrangement depicted in  FIG. 8 , the object  538  can be illuminated simultaneously from several directions, with each of the illumination beams  544 — 544 ′″ satisfying the total reflection condition in the same way. 
     FIGS. 9 and 10  show additional embodiments of the adapter, which was already shown in  FIGS. 2–7  and is depicted here in a side view. The components of this adapter, labeled with reference numbers  640  and  740 , the function of which corresponds to that of the adapter shown in  FIG. 4 , are labeled with the same reference numbers but in this case they are increased by the number  400  or  500  in each case. 
   In the embodiments of the adapter  640  and  740  shown in  FIGS. 9 and 10 , the illumination light is introduced into the adapters  640  and/or  740  via a lightguide  678  or  778 , e.g., a glass fiber. An adapter optics  680  or  780 , e.g., composed of microlenses, is connected to the lightguide  678  or  778  to focus the illumination beam  644  or  744  coming from the lightguide  678  or  778  in the back focal plane  646  or  746 . 
   In the embodiment depicted in  FIG. 9 , the lightguide  678  is introduced into the adapter  640  at a right angle to the optical axis  654 , so that it must be deflected in a direction parallel to the optical axis  654  by a deflecting unit, which is shown in  FIG. 9  as a prism  650 . On the other hand, the lightguide  778  in the exemplary embodiment depicted in  FIG. 10  is curved, so that the focused illumination beam  744  leaving the adapter optics  780  is already parallel to the optical axis  754 . 
   In both exemplary embodiments, the reflected beam  656  or  756  can be output with the help of the optical elements which correspond to those used for coupling. This is implemented in  FIG. 9  by the prism  666  and the lightguide  682 , which is connected by the adapter optics  684  to the prism  666 . In  FIG. 10  this is done through the lightguide  782  and the adapter optics  784  attached to the end thereof, and with respect to the optical axis  754 , said optics are also mounted symmetrically with the adapter optics  780  used for coupling the illumination beam  744 . 
     FIGS. 11–14  show embodiments of the present invention in which the deflecting units, which are used for coupling of the illumination beam and/or for output of the reflected beam are integrated into a special optics system (objective)  816 ,  916 ,  1016 ,  1116 . Components whose functions correspond to those in the preceding figures are labeled with the same reference numbers in  FIGS. 11–14 , but each of the numbers has been increased by 100. In comparison with the embodiments in which the deflecting units are integrated into an adapter, the embodiments depicted in  FIGS. 11–14  offer the advantage that the optical components required for the deflecting units can be adapted to the lens system of the optics system  816 ,  916 ,  1016 ,  1116 , so that the quality of the optical imaging can be optimized on the whole. In addition, such special optics systems can also be used for microscopes which do not have an adapter receptacle, as depicted in  FIG. 2 . 
     FIG. 11  shows the illumination beam  844  coupled via a rod prism  850  into the beam path of the microscope. Likewise, the reflected beam  856  is guided out of the optics system  816  via another rod prism  866 . Both of the prisms  850 ,  866  are situated here in the area of the optics system so that they are displaceable in the radial direction for adjusting the reflection angle in the beam path of the microscope (represented by the double arrows B, B′ in  FIG. 11 ). An alternative arrangement of the rod prism  850  is shown with dotted lines in  FIG. 11 . In this arrangement, the rod prism  850 ′ for coupling of the illumination beam  844  is situated between the illuminated front lens of the optics system and its focal plane  846  on the ocular end. The illumination beam  844  in this case is focused virtually on the focal plane  846  on the ocular end of the lens system through which the beam passes. This arrangement allows a particularly space-saving design of a special optics system with an integrated deflecting unit. 
   In the exemplary embodiment illustrated in  FIG. 12 , in contrast with  FIG. 11 , a double prism  950  is used for coupling of the illumination beam  944 , so that the illumination beam  940  can be deflected by 180°. 
   In the exemplary embodiments illustrated in  FIGS. 13 and 14 , lightguides  1078 ,  1082 .  1178  are used to couple and/or output the illumination light coming from a light source (not shown) in the area of the optics system into the beam path of the microscope. In the arrangement depicted in  FIG. 13 , which is similar to that in  FIG. 9 , an adapter optics  1080  mounted on the lightguide  1078  and a prism  1050  which is connected to the adapter optics  1080  are used for coupling of the illumination beam  1040 . The reflected beam  1056  is output through a prism  1066 , which is situated symmetrically with respect to the optical axis  1054 , and an adapter optics  1084  which is connected thereto and has a lightguide  1082  connected to it. In contrast with this,  FIG. 14  shows an embodiment in which a curved lightguide  1178  is connected to the adapter optics  1180  aligned in parallel with the optical axis  1154  to couple the illumination beam  1144  into the beam path of the microscope in parallel with the optical axis. 
     FIGS. 1–14  illustrate various embodiments of a microscope which can be used in particular for TIR microscopy. The microscope is operated in a reflected light arrangement in which the light which is used to illuminate the object passes through at least a portion of the optics system before striking the object to be observed. The illumination beam is coupled through an optical device into the passage between the ocular and the optics system of the microscope here, the cross section of this optical device in the passage being small in comparison with the cross section of the passage. This achieves the result that it is possible to eliminate the use of beam splitter elements such as dichroic mirrors for coupling of the illumination light. A special optics system having integrated optical elements to provide the illumination beam and/or to capture or output the reflected beam may be used. As an alternative, said optical elements may also be integrated into an adapter, which can be inserted into the beam path of an existing microscope. 
   LIST OF REFERENCE NOTATION 
   
       
       A: circle (enlarged detail for  FIG. 2 ) 
       F: focal point of the optics system 
       α: angle of divergence of the illumination beam 
       β: angle of reflection of the illumination beam at the interface between the microscope slide and the object 
       a: distance between the optical axis and the illumination beam 
       B, B′: displacement of the deflecting unit in the radial direction 
       D, D′: displacement of the focusing lenses in the radial direction 
       E, E′: displacement of the deflecting unit in the axial direction 
         10 : microscope 
         12 : visual observation part 
         14 : eyepiece 
         16 : optics system 
         18 : microscope housing 
         19 : passage 
         20 : photographic observation part 
         22 : camera 
         24 : illumination part 
         26 : partially transparent mirror 
         28 : revolver head of the optics system 
         30 : revolver axis of rotation 
         32 : adapter receptacle 
         34 : mount (for transmitted light illumination) 
         36 : microscope slide 
         38 : object 
         40 : adapter 
         42 : interface between microscope slide and object 
         44 : illumination beam 
         45 : plane of incidence of the illumination beam 
         46 : back focal plane of the optics system 
         48 : front lens of the optics system 
         50 : deflector unit for coupling of the illumination beam 
         52 : lens for focusing the illumination beam 
         54 : optical axis 
         56 : reflected beam 
         58 : absorber 
         60 : aperture diaphragm in the illumination beam 
         62 : additional aperture diaphragm on the optics system 
         164 : light source 
         166 : deflecting unit for output of the reflected beam 
         168 : lens for focusing the reflected beam 
         170 : detector 
         272 : filter wheel 
         274 : axis of rotation of the filter wheel 
         286 : connection of the adapter on the ocular end 
         288 : connection of the optics system on the ocular end 
         290 : connection of the adapter on the optics system end 
         292 : connection of the microscope housing on the optics system end 
         350 : planar mirror for coupling of the illumination beam 
         366 : planar mirror for output of the reflected beam 
         450 : curved mirror for coupling and focusing of the illumination beam 
         466 : curved mirror for output and focusing of the reflected beam 
         576 : deflecting unit comprising a plurality of deflecting units 
         678 : lightguide for coupling of the illumination beam 
         680 : adapter optics for focusing the illumination beam 
         682 : lightguide for output of the reflected beam 
         684 : adapter optics for output of the reflected beam