Patent Publication Number: US-11036039-B2

Title: Microscopy system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German patent application DE 10 2017 208 019.1, filed on May 11, 2017, and to German patent application DE 10 2018 204 426.0, filed Mar. 22, 2018, both of which are hereby incorporated by reference in their entireties. 
     TECHNICAL FIELD 
     The present disclosure relates to a microscopy system for simultaneously recording an overview image and for determining an approximation value for a spatial distribution of the concentration of a fluorescent dye. 
     BACKGROUND 
     Fluorescent dyes are used in the area of tumour resection to differentiate between diseased tissue and healthy tissue. To this end, a fluorescent dye is accumulated in the region of the diseased tissue, which, upon exposure to light of its excitation spectrum, emits fluorescent light of its emission spectrum. Since the fluorescent light comes only from the tissue in which the fluorescent dye has accumulated, additionally an overview image is helpful to be able to view the diseased image among the healthy tissue. 
     However, the fluorescent light emitted by the tissue is not a measure of the concentration of the fluorescent dye and consequently not a measure of the quantity/concentration of the diseased tissue, since the strength of the fluorescence also depends on other properties of the tissue. Tissue regions in which the same concentration of a fluorescent dye is present therefore appear with different intensities in fluorescence images, even though the concentration of the fluorescent dye is the same in these regions. The following properties of the tissue are responsible for the difference between the intensity that is emitted by the fluorescent dye and the intensity therefrom that arrives at a detector. First, the tissue absorbs light in the range of the excitation spectrum, and as a result not all the light provided for exciting the fluorescent dye actually reaches the fluorescent dye. In the emission wavelength range, light scattering of the fluorescent light has the effect that not all the light that is emitted by the fluorescent dye reaches the detector, but is scattered by the surrounding tissue. 
     It has been shown that a semi-empirical approximation for the light intensity that is actually emitted by a fluorescent dye exists which is dependent on the measured fluorescent light intensity and on the intensity of reflected light in the wavelength ranges of the absorption spectrum and the emission spectrum (P. A. Valdes et al., “A spectrally constrained dual-band normalization technique for protoporphyrin IX quantification in fluorescence-guided surgery,” Optical Society of America, Optics Letter, Vol. 37, No. 11, Jun. 1, 2012, pp. 1817-1819). 
     A generalized approximation can be expressed as follows: 
                 I   FL   total     =     A   ⁢       I   FL   det           (     I     Ko   ⁢           ⁢   1       )     α     ·       (     I     Ko   ⁢           ⁢   2       )     β             ,         
wherein
         I FL   tot  designates the spatial distribution of the intensity of fluorescent light which is emitted by the fluorescent dye without the disturbing influence of the surrounding tissue in the object region,   I FL   det  designates the spatial distribution of the intensity of fluorescent light which can be detected using a microscope and consequently contains the misrepresentations caused by the surrounding tissue,   I Ko1  designates the spatial distribution of the intensity of light of a wavelength range near the emission spectrum of the fluorescent dye that is reflected at the tissue,   I Ko2  designates the spatial distribution of the intensity of light of a wavelength range near the excitation spectrum of the fluorescent dye that is reflected at the tissue,   A designates an empirical parameter,   α designates a further empirical parameter, and   β designates yet a further empirical parameter.       

     The parameters A, α, and β can be empirically determined, for example, using comparative methods. The spatial distributions of light intensities I FL   det , I Ko1 , and I Ko2  are therefore intensities of light of generally different wavelength ranges which are detected using a microscope. By contrast, I FL   tot  designates the intensity distribution of light, which is actually produced by the fluorescent dye in the object region. In other words, the disturbing influence of the tissue surrounding the fluorescent dye is not reflected in I FL   tot , but is reflected in I FL   tot . Since I FL   tot  represents the intensity distribution of fluorescent light without the disturbing influence of the tissue, I FL   tot  is a measure of the spatial distribution of the concentration of the fluorescent dye in the object region and consequently also of the spatial distribution of the quantity/concentration of diseased tissue in the object region. 
     Conventional microscopy systems that are configured to detect I FL   det , I Ko1  and I Ko2 , have the disadvantage that these intensity distributions are detected sequentially one after the other, with the result that recording the intensity distributions I FL   det , I Ko1 , and I Ko2  is a lengthy process. This is a significant disadvantage especially in the field of surgery, because the tissue in the object region can change during the recording of said intensity distributions, which negatively influences the accuracy of the resulting intensity distribution I FL   tot . 
     SUMMARY 
     It is therefore an objective of the present disclosure to provide a microscopy system that overcomes the above disadvantage. In particular, it is an object of the present disclosure to provide a microscopy system which repeatedly and quickly detects the spatial distribution of the concentration of a fluorescent dye. 
     The above objective is achieved by way of a microscopy system in accordance with the disclosure, which is configured to simultaneously record the intensity distributions I FL   det , I Ko1 , and I Ko2 . 
     A microscopy system according to the disclosure for simultaneously recording an overview image and determining the concentration of a fluorescent dye in tissue in an object region comprises: a detection system which is configured to detect light of a first channel in a first detection region and convert it to a first fluorescent light signal, to detect light of a second channel in a second detection region and convert it to a first correction signal, and to detect light of a third channel in a third detection region and convert it to a second correction signal, wherein a first part of the emission spectrum of the fluorescent dye, i.e., a first emission wavelength range, is detected (substantially only) in the first detection region (first channel), wherein a wavelength range near the first part of the fluorescence spectrum, i.e., a first correction wavelength range, is detected (substantially only) in the second detection region (second channel), and wherein part of the excitation spectrum of the fluorescent dye, i.e., a second correction wavelength range, is detected (substantially only) in the third detection region (third channel). 
     “Substantially only” means that an optical unit of the microscopy system, which images onto the detection regions an object region in which tissue in which the fluorescent dye has accumulated can be situated, is configured such that at least 75%, typically at least 90%, more typically at least 99%, of light of the first emission wavelength range emanating from the object region is directed onto the first detection region, at least 75%, typically at least 90%, more typically at least 99%, of light of the first correction wavelength range emanating from the object region is directed onto the second detection region, and at least 75%, typically at least 90%, more typically at least 99%, of light of the second correction wavelength range emanating from the object region is directed onto the third detection region. 
     Alternatively, “substantially only” can be defined such that the ratio of the intensity of light of a specific wavelength at a detection region to the intensity of light of the same wavelength at a different detection region has a value of at least 10:1, typically at least 100:1, more typically at least 1000:1. 
     Hereby, the detection system provides three (image) signals which represent the spatial intensity distributions I FL   det , I Ko1 , and I Ko2 . The microscopy system furthermore comprises a controller, which can determine the spatial distribution of the intensity of fluorescent light emitted in the object region and can determine therefrom an approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region. For example, the approximation value is a value which is proportional to the concentration of the fluorescent dye in the object region. 
     Consequently, the controller is configured to eliminate the influence of the tissue that is arranged around the fluorescent dye from the signal I FL   det . The resulting signal I FL   tot  can be used by the controller to determine the spatial distribution of the concentration of the fluorescent dye in the object region. 
     In order to be able to separately detect the wavelength ranges on which the intensity distributions I FL   det , I Ko1  and I Ko2  are based, the optical unit and/or the detection system can comprise different wavelength-dependent optical elements. These optical elements can comprise, for example, (dichroic) beam splitters, optical filters or filter matrices in the manner of a Bayer pattern. 
     The previously described microscopy system makes use of the fact that a relatively large wavelength range is situated between the (peak in the) absorption spectrum of a fluorescent dye and a (main) peak of the emission spectrum of the fluorescent dye, with the result that the first correction wavelength range and the second correction wavelength range do not, or substantially do not, overlap. The first correction wavelength range and the second correction wavelength range are therefore detected by different detection regions in different channels. 
     However, a fluorescent dye can have a plurality of local absorption maxima and a plurality of local emission maxima, or the wavelength range between the main absorption peak and the main emission peak can be small. In these cases, it may be advantageous to use the same detection region both for the first correction wavelength range and for the second correction wavelength range. In this case, the first correction wavelength range and the second correction wavelength range, spectrally speaking, are close together or overlap at least partially or significantly. Consequently, a single detection region can be used for detecting both the first correction wavelength range and the second correction wavelength range. Consequently, only one (single) correction signal is available for the determination of the approximation value for the spatial distribution of the concentration of the fluorescent dye. The other channels of a multichannel image detector, which also comprises the detection region in which the first and second correction wavelength ranges are detected, can therefore be used for recording an overview image. The microscopy system just described therefore takes advantage of a special case of the above-described expression for the approximation, for which is true that I Ko1  can be considered an approximation for I Ko2 . 
     As a result, for this special case, a different function for determining the approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region is obtained, wherein this function comprises as arguments the first fluorescent light signal and the first correction signal which represents light both of the first correction wavelength range and of the second correction wavelength range. In particular, this function can comprise as a term: 
     
       
         
           
             
               I 
               FL 
               tot 
             
             = 
             
               B 
               ⁢ 
               
                 
                   I 
                   FL 
                   det 
                 
                 
                   
                     ( 
                     
                       I 
                       Ko 
                     
                     ) 
                   
                   γ 
                 
               
             
           
         
       
         
         
           
             wherein
           I FL   tot  designates the spatial distribution of the intensity of fluorescent light emitted in the object region,   I FL   det  designates the first fluorescent light signal,   I Ko  designates the first correction signal,   B designates a parameter, and   γ designates a further parameter.   
         
           
         
       
    
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will now be described with reference to the drawings wherein: 
         FIG. 1  shows a schematic illustration of a stereo microscope in accordance with an exemplary embodiment. 
         FIG. 2  shows an exemplary embodiment of a spectral configuration of elements of the stereo microscope of  FIG. 1 . 
         FIG. 3A  shows an exemplary embodiment of a spectral configuration for illumination light for an optical filter of the stereo microscope of  FIG. 1 . 
         FIG. 3B  shows another exemplary embodiment of a spectral configuration for illumination light for another optical filter of the stereo microscope of  FIG. 1 . 
         FIG. 3C  shows another exemplary embodiment of a spectral configuration for illumination light for another optical filter of the stereo microscope of  FIG. 1 . 
         FIG. 3D  shows another exemplary embodiment of a spectral configuration for illumination light for another optical filter of the stereo microscope of  FIG. 1 . 
         FIG. 4  shows an exemplary embodiment of a spectral configuration for illumination light and further elements of the stereo microscope of  FIG. 1 . 
         FIG. 5  shows a schematic illustration of a stereo microscope in accordance with a further exemplary embodiment. 
         FIG. 6  shows a spatial configuration of detection regions of a multichannel image detector. 
         FIG. 7  shows an exemplary embodiment of a spectral configuration of detection regions of the stereo microscope of  FIG. 5 . 
         FIG. 8  shows a further exemplary embodiment of a spectral configuration for illumination light and elements of the stereo microscope of  FIG. 1 . 
         FIG. 9  shows a further exemplary embodiment of a spectral configuration of an optical filter of the stereo microscope of  FIG. 1 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a schematic illustration of a microscopy system  1  in accordance with an exemplary embodiment. 
     The microscopy system  1  comprises an illumination apparatus  3 , which is configured to produce illumination light  5  and to direct it onto an object region  7 . The illumination apparatus  3  can comprise one or more narrowband and/or broadband light sources and one or more illumination filters for producing the illumination light  5 . 
     Arranged in the object region  7  can be for example tissue with a fluorescent dye. The fluorescent dye can be for example protoporphyrin IX (PPIX), which has an absorption spectrum ( 33 ) between approximately 350 nm and 650 nm, with the dominant absorption peak being at 405 nm, and having an emission spectrum ( 35 ) between 600 nm and 750 nm, with the dominant absorption peaks being at 635 nm and 705 nm (cf. diagram  31  in  FIG. 2 ). 
     The microscopy system  1  furthermore comprises a first detection system  9  and a first optical unit  11 . 
     The first detection system  9  comprises a first fluorescent light image detector  17  and a first multichannel image detector  19 . The first fluorescent light image detector  17  is an image detector, i.e., the fluorescent light image detector  17  outputs a signal that represents an image, wherein the image represents the intensity of light that is incident on a detection region of the fluorescent light image detector  17  within a determined time period. Depending on the application, the first fluorescent light image detector  17  can be configured as a monochromatic sensor or as a multichannel image detector, wherein a multichannel image detector is suitable for detecting a plurality of different channels. 
     The first multichannel image detector  19  is likewise an image detector. A multichannel image detector has a plurality of different detection regions which can detect in each case light of one channel and output a signal for each channel. Here, “channel” designates a wavelength range. The channels at most partially spectrally overlap. For example, the channels of the first multichannel image detector overlap in pairs at most by 100 nm, typically at most by 50 nm. One example of a multichannel image detector is a conventional RGB color camera. 
     A conventional RGB color camera has the channels red (R), green (G), and blue (B). Here, the blue channel can comprise the wavelength range from 400 nm to 530 nm, the green channel can comprise the wavelength range from 460 nm to 600 nm, and the red channel can comprise the wavelength range from 570 nm to 750 nm. 
     The first optical unit  11  comprises an objective  21  and a first beam splitter  23 . The first optical unit  11  can comprise further optical elements, for example the first image-forming lens  25  or a first zoom element (not illustrated in  FIG. 1 ), which can be arranged between the first image-forming lens  25  and the objective  21 . 
     The first optical unit  11  is configured to image the object region  7  onto detection regions of the first fluorescent light image detector  17  and the multichannel image detector  19 , as is illustrated by way of a first beam path  27 . The first optical unit  11  can comprise filters and filter matrices in the manner of a Bayer pattern, which are arranged directly in front of the detection regions. In other words, the optical unit here also comprises filters which are fixedly connected to the detectors. 
     The optical unit is configured to direct light of specific wavelengths substantially only onto a single one of the detection regions (depending on the stereo beam path). 
       FIG. 2  shows a spectral configuration of the illumination light  5 , of the first fluorescent light image detector  17 , of the first multichannel image detector  19  and of the first beam splitter  23  for an exemplary fluorescent dye that is arranged in the object region  7 . 
     Diagram  31  shows a normalized absorption spectrum  33  (normalized to its maximum value) and a normalized emission spectrum  35  (normalized to its maximum value). The absorption spectrum  33  and the emission spectrum  35  correspond to those of the fluorescent dye PPIX. 
     Diagram  41  shows the intensity of the illumination light  5  in dependence on the wavelength. In a first emission wavelength range Em 1 , which extends from λEm 1 L to λEm 1 H, the illumination light  5  has at most one first intensity W 1 . That is to say, within the entire wavelength range from λEm 1 L to λEm 1 H, the illumination light  5  does not at any wavelength have an intensity that is greater than the first intensity W 1 . The first emission wavelength range Em 1  comprises at least a first part of the emission spectrum  35 . In the first part of the emission spectrum, the normalized emission (normalized to the maximum value of the emission spectrum  35 ) has for example a value of at least 1%, typically at least 5%, more typically at least 10%. 
     A first correction wavelength range Ko 1  is situated spectrally near the first emission wavelength range Em 1 . For example, the first correction wavelength range Ko 1  is situated in the range between λEm 1 L−150 nm and λEm 1 H+150 nm. The first correction wavelength range Ko 1  does not overlap the first emission wavelength range Em 1 . Within the first correction wavelength range Ko 1 , the illumination light  5  has at least a second intensity W 2 . That is to say within the entire correction wavelength range Ko 1 , the illumination light  5  does not at any wavelength have an intensity that is lower than the second intensity. The first intensity W 1  is lower than the second intensity W 2  for example by at least a factor of 2, 5, 10, 20, 50, 100, 1,000 or 10,000, as a result of which the object region  7  is exposed with light of the first correction wavelength range Ko 1 , while the first emission wavelength range Em 1  is substantially not exposed. 
     A second correction wavelength range Ko 2  comprises a first part of the excitation spectrum  33  of the fluorescent dye. The first part of the excitation spectrum  33  has for example a normalized absorption (normalized to the maximum value of the absorption spectrum  33 ) of at least 1%, typically at least 5%, more typically at least 10%. Within the second correction wavelength range Ko 2 , the illumination light  5  has at least the second intensity W 2 . That is to say within the entire correction wavelength range Ko 2 , the illumination light  5  does not at any wavelength have an intensity that is lower than the second intensity. The fluorescent dye is excited hereby, as a result of which the fluorescent dye emits light in the emission spectrum  35 . 
     In the example shown in  FIG. 2 , the first emission wavelength range Em 1  extends from 610 nm to 655 nm; the first correction wavelength range Ko 1  extends from 560 nm to 595 nm; and the second correction wavelength range Ko 2  extends from 390 nm to 420 nm. Alternatively, the first emission wavelength range Em 1  can extend from 640 nm to 710 nm; the second correction wavelength range Ko 2  can extend from 430 nm to 450 nm. 
     The first beam splitter  23  of the first optical unit  11  can be a dichroic beam splitter, for example. That means that the first beam splitter  23  can be configured to output light of a wavelength that is greater than a first limit wavelength λ 1  substantially only to the first fluorescent light image detector  17 , and to output light of a wavelength that is smaller than the first limit wavelength λ 1  substantially only to the first multichannel image detector  19 . “Substantially only” means, for example, that the ratio of the average transmittance in a first output (to the first fluorescent light image detector  17 ) in the wavelength range above the first limit wavelength λ 1  to the average transmittance in a second output (to the first multichannel image detector  19 ) in the same wavelength range is at least 100, typically at least 1000, more typically at least 10 000. 
     As in the example shown in  FIG. 2 , the first limit wavelength λ 1  can be situated between the first emission wavelength range Em 1  and the first correction wavelength range Ko 1 . In the example shown in  FIG. 2 , the first limit wavelength is 600 nm. Light of the first emission wavelength range Em 1  emanating from the object region  7  is hereby output (substantially only) to the first fluorescent light image detector  17 . Light of the first correction wavelength range Ko 1  emanating from the object region  7  is output (substantially only) to the first multichannel image detector  19 ; and light of the second correction wavelength range Ko 2  emanating from the object region  7  is output (substantially only) to the first multichannel image detector  19 . 
     It is also possible to use, instead of a dichroic beam splitter, a conventional beam splitter together with corresponding filters to achieve the same effect. A filter arranged between the conventional beam splitter and the first fluorescent light image detector  17  to this end has a high transmittance for example only in the first emission wavelength range Em 1 . A filter arranged between the conventional beam splitter and the first multichannel image detector  19  to this end has in each case a high transmittance for example in the first and second correction wavelength ranges and a low transmittance in the first emission wavelength range Em 1 . A ratio between a high and a low transmittance can be, for example, at least 100, typically at least 1,000, even more typically at least 10,000. 
     With the beam splitter  23  and further filters that spectrally separate the second and third channels from one another, the first optical unit  11  is configured to simultaneously image light of the first emission wavelength range Em 1  emanating from the object region  7  onto a first detection region of the first fluorescent light image detector  17 , light of the first correction wavelength range Ko 1  emanating from the object region  7  onto a second detection region of the first multichannel image detector  19 , and light of the second correction wavelength range Ko 2  emanating from the object region  7  onto a third detection region of the first multichannel image detector  19 . The further filters are for example those that have a conventional RGB color camera. 
     The first fluorescent light image detector  17  is configured to detect light of a first channel in the first detection region. Light of the first channel is detected in the first detection region and converted to a first fluorescent light signal. In other words, “channel” designates the wavelength range for which the first detection region of the first fluorescent light image detector  17  has a non-negligible sensitivity for light. The fluorescent light signal output by the first fluorescent light image detector  17  therefore represents the intensity of light of the first channel that is incident on the first detection region within a predetermined time period. 
     Diagram  51  illustrates the first channel Ch 1 . The first channel Ch 1  comprises the first emission wavelength range Em 1 . The first detection region is therefore used to detect light of the first emission wavelength range Em 1  and to output a corresponding signal, the fluorescent light signal. In the present example, the first channel Ch 1  extends from approximately 600 nm to 670 nm. 
     The first multichannel image detector  19  is configured to detect light of a second channel Ch 2  in a second detection region and to convert it to a first correction signal. Diagram  52  illustrates the second channel Ch 2  of the first multichannel image detector  19 . The second channel Ch 2  comprises the first correction wavelength range Ko 1 . In the present exemplary embodiment, the second channel Ch 2  extends from approximately 550 nm to over 700 nm. This approximately corresponds to the red channel of a conventional RGB color camera. 
     The first multichannel image detector  19  is furthermore configured to detect light of a third channel Ch 3  in a third detection region and to convert it to a second correction signal. Diagram  53  illustrates the third channel Ch 3  of the first multichannel image detector  19 . The third channel Ch 3  comprises the second correction wavelength range Ko 2 . In the present exemplary embodiment, the third channel Ch 3  extends from approximately 350 nm to 540 nm. This approximately corresponds to the blue channel of a conventional RGB color camera. 
     Once again with reference to  FIG. 1 , the microscopy system  1  furthermore comprises a controller  29 , which receives the first fluorescent light signal, the first correction signal and the second correction signal from the first fluorescent light image detector  17  and from the first multichannel image detector  19 . The controller is configured to process the first fluorescent light signal, the first correction signal and the second correction signal and to determine therefrom an approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region  7 . 
     Due to the simultaneous and substantially exclusive imaging of the first emission wavelength range Em 1  onto the first detection region, of the first correction wavelength range Ko 1  onto the second detection region, and of the second correction wavelength range Ko 2  onto the third detection region, it is possible to obtain signals for these three wavelength ranges at the same time. It is hereby possible to repeatedly quickly calculate the approximation value for the concentration of the fluorescent dye in the object region  7 . 
     Further exemplary embodiments, which are based on the exemplary embodiments described in connection with  FIGS. 1 and 2 , will be described below. 
     According to a further exemplary embodiment, the optical unit  11  furthermore comprises a first optical filter  61  (cf.  FIG. 1 ), which is arranged between the first beam splitter  23  and the first multichannel image detector  19 . An average transmittance of the first optical filter  61  in the first correction wavelength range Ko 1  can be at least 50%, typically at least 80%, more typically at least 90%. Furthermore, an average transmittance of the first optical filter  61  in the second correction wavelength range Ko 2  can be at least 50%, typically at least 80%, more typically at least 90%. Furthermore, an average transmittance of the first optical filter  61  between the first correction wavelength range Ko 1  and the second correction wavelength range Ko 2  can be at most 30%, typically at most 10%, more typically at most 1%. 
       FIGS. 3A to 3D  illustrate various exemplary embodiments for the illumination and for the first optical filter  61 . 
     In the exemplary embodiment in accordance with  FIG. 3A , the illumination light  5  has at least the second intensity W 2  in the wavelength range of approximately 400 nm to approximately 600 nm, wherein the first limit wavelength λ 1  of the dichroic beam splitter  23  is at approximately 600 nm. Outside this wavelength range, the illumination light  5  has at most the first intensity W 1 , i.e., from 600 nm to at least 720 nm. The wavelength range from 400 nm to 600 nm here comprises the first and second correction wavelength ranges. 
     The first optical filter  61  has a high average transmittance T in a wavelength range from approximately 400 nm to approximately 600 nm and has a low transmittance outside said wavelength range. For example, an average transmittance of the first optical filter ( 61 ) between 400 nm and 600 nm is at least 50%, typically at least 80%, more typically at least 90%. Hereby, the object region  7  is exposed in the first and second correction wavelength ranges, and the light of the first and second correction wavelength ranges that is reflected at the object region  7  is imaged onto the first multichannel image detector  19  by way of the first filter  61 . Here, the reflected light is detected by the second detection region and the third detection region in different channels, to be precise in the second and in the third channel. 
     The first emission wavelength range Em 1  can in this exemplary embodiment comprise for example a region around 635 nm, a region around 705 nm or a range from 635 nm to 705 nm. An average transmittance of the first optical filter ( 61 ) can have, in the first emission wavelength range (Em 1 ), at most a value (W 3 ) that is smaller than the average transmittance of the first optical filter ( 61 ) in the first correction wavelength range (Ko 1 ) and/or second correction wavelength range (Ko 2 ) by at least a factor of 10, typically 100, more typically 1,000. 
     As a result, for example if the first multichannel image detector  19  is a conventional RGB color camera, an overview image with high color fidelity can be recorded with the RGB camera, and in addition, the signal of the red channel, which comprises the first correction wavelength range Ko 1 , and the signal of the blue channel, which comprises the second correction wavelength range Ko 2 , can be used to determine the spatial distribution of the concentration of the fluorescent dye. While it is possible hereby to produce an overview image of particularly high color fidelity, the signal of the red channel represents not only the intensity of light of the first correction wavelength range Ko 1 , but also light of other wavelengths within the red channel. The same is correspondingly true for the blue channel. This can have a negative influence on the accuracy of the determination of the spatial distribution of the concentration of the fluorescent dye. 
     As illustrated in  FIG. 3B , the illumination light  5  in accordance with a further exemplary embodiment corresponds to the illumination light  5 , as is used in the exemplary embodiment shown in  FIG. 3A . The first filter  61  in accordance with  FIG. 3B  has a high transmittance only in the first correction wavelength range Ko 1  and in the second correction wavelength range Ko 2  and, for the rest, has a low transmittance. For example, an average transmittance of the first optical filter ( 61 ) has, between the first correction wavelength range (Ko 1 ) and the second correction wavelength range (Ko 2 ), at most a value (W 3 ) that is smaller than the average transmittance of the first optical filter ( 61 ) in the first correction wavelength range (Ko 1 ) and/or second correction wavelength range (Ko 2 ) by at least a factor of 10, 100, or 1,000. The ranges having high transmittances in the first filter  61  in accordance with  FIG. 3B  can also be wider in every direction than the first or second correction wavelength range by approximately 5 nm to 25 nm. 
     The overview image which is obtained in this exemplary embodiment using a conventional RGB camera (for the first multichannel image detector  19 ) does not exhibit color fidelity due to the suppression of a portion of the visible spectrum. However, the accuracy for the determination of the spatial distribution of the concentration of the fluorescent dye is improved because only light of the first correction wavelength range Ko 1  is fed to the second detection region (red channel) and because only light of the second correction wavelength range Ko 2  is fed to the third detection region (blue channel). 
     The same effect is also achieved by way of the exemplary embodiment illustrated in  FIG. 3C . Here, the illumination light  5  has at least the second intensity W 2  only in the first correction wavelength range Ko 1  and in the second correction wavelength range Ko 2 , and for the rest has only at most the first intensity W 1 . The first filter  61  in accordance with  FIG. 2C  corresponds to the first filter  61  in accordance with  FIG. 3A . 
     Improved color fidelity and at the same time a high degree of accuracy in the determination of the spatial distribution of the concentration of the fluorescent dye can be achieved with the configuration in accordance with  FIG. 3D . To this end, the first multichannel image detector  19  furthermore has a fourth detection region, with which light of a fourth channel Ch 4  can be detected and converted into a signal of the fourth channel. The fourth channel Ch 4  at most partially overlaps the second and third channel, respectively. In a conventional RGB color camera, the fourth channel for example corresponds to the green channel, which is illustrated by way of example in  FIG. 2  in diagram  54 . 
     The illumination light  5  has, in a supplementary wavelength range G 1 , which is contained in the fourth channel Ch 4  (green channel), an average fourth intensity W 4 . The average fourth intensity can be 0.01% to 50% of the second intensity (W 2 ), typically 0.05% to 10% of the second intensity (W 2 ), more typically 0.1% to 1% of the second intensity (W 2 ). Here, the first intensity (W 1 ) can be lower than the average fourth intensity (W 4 ) by at least the factor of 10, typically by at least a factor of 100, more typically by at least a factor of 1,000. 
     The illumination light  5  can have for example at most the first intensity W 1  between the first correction wavelength range Ko 1  and the supplementary wavelength range G 1  and between the supplementary wavelength range G 1  and the second correction wavelength range Ko 2 . The supplementary wavelength range G 1  can comprise, for example, a wavelength range of 520 nm to 570 nm. 
     An average transmittance of the first optical filter ( 61 ) is, in the first correction wavelength range (Ko 1 ) and the second correction wavelength range (Ko 2 ), for example in each case 0.01% to 50% of an average transmittance of the first optical filter ( 61 ) in the supplementary wavelength range (G 1 ), typically 0.05% to 10% of the average transmittance of the first optical filter ( 61 ) in the supplementary wavelength range (G 1 ), more typically 0.1% to 1% of the average transmittance of the first optical filter ( 61 ) in the supplementary wavelength range (G 1 ). 
     An average transmittance of the first optical filter ( 61 ) can be, between the first correction wavelength range (Ko 1 ) and the supplementary wavelength range (G 1 ) and between the supplementary wavelength range (G 1 ) and the second correction wavelength range (Ko 2 ), lower than the average transmittance of the first optical filter ( 61 ) in the first correction wavelength range (Ko 1 ) and/or second correction wavelength range (Ko 2 ) by at least a factor of 10, typically 100, more typically 1,000. 
     In accordance with a further exemplary embodiment, the microscopy system  1  is a stereo microscopy system, as illustrated in  FIG. 1 . As such, the microscopy system  1  illustrated in  FIG. 1  furthermore comprises a second detection system  109  and a second optical unit  111 . The second detection system  109  can be configured to be similar or identical to the first detection system  9 . The second optical unit  111  can be configured to be similar or identical to the first optical unit  11 . 
     The second detection system  109  comprises a second fluorescent light image detector  117  and a second multichannel image detector  119 . The second fluorescent light image detector  117  can be configured to be similar or identical to the first fluorescent light image detector  17 . The second multichannel image detector  119  can be configured to be similar or identical to the first multichannel image detector  19 . 
     If the second detection system  109  and the first detection system  9  have identical configuration, they each have the same spectral configuration. 
     Alternatively, the second fluorescent light image detector  117  and the second multichannel image detector  119  can have a different spectral configuration, with the result that a further emission wavelength range can be detected. 
     Here, the second fluorescent light image detector  117  is configured to detect a second emission wavelength range Em 2 , which differs from the first emission wavelength range Em 1 . The second emission wavelength range Em 2  extends from λEm 2 L to λEm 2 H and is a second part of the emission spectrum  35  of the fluorescent dye. The first emission wavelength range Em 1  and the second emission wavelength range Em 2  can, for example, partially overlap or not overlap. For example, the first emission wavelength range Em 1  and the second emission wavelength range Em 2  can overlap by at most 50 nm, in particular, at most 20 nm or at most 10 nm. 
     The second fluorescent light image detector  117  is configured to detect light of a fifth channel in a fifth detection region and to convert it to a second fluorescent light signal. The second multichannel image detector  119  is furthermore configured to detect light of a sixth channel in a sixth detection region and to convert it to a third correction signal. The multichannel image detector  119  is furthermore configured to detect light of a seventh channel in a seventh detection region and to convert it to a fourth correction signal. 
     An exemplary embodiment of such an exemplary spectral configuration is represented in  FIG. 4 . 
     Diagram  31  shows the normalized absorption spectrum  33  and the normalized emission spectrum  35 . Diagram  41  shows the intensity of the illumination light  5  in dependence on the wavelength. 
     Diagram  151  illustrates the fifth channel Ch 5 . The fifth channel Ch 5  comprises the second emission wavelength range Em 2 . The fifth detection region is therefore used to detect light of the second emission wavelength range Em 2  and to output a corresponding signal. In the present exemplary embodiment, the second emission wavelength range Em 2  comprises a wavelength from 680 nm to 720 nm. In particular, the second emission wavelength range Em 2  comprises the wavelength 705 nm. 
     Diagram  152  illustrates the sixth channel Ch 6  of the second multichannel image detector  119 . The sixth channel Ch 6  comprises a third correction wavelength range Ko 3 . The third correction wavelength range Ko 3  is situated between λEm 2 L−150 nm and λEm 2 H+150 nm and does not overlap the second emission wavelength range Em 2 . In the present exemplary embodiment, the sixth channel Ch 6  extends from approximately 550 nm to over 700 nm. This approximately corresponds to the red channel of a conventional RGB color camera. 
     Diagram  153  illustrates the seventh channel Ch 7  of the second multichannel image detector  119 . The seventh channel Ch 7  comprises a fourth correction wavelength range Ko 4 . The fourth correction wavelength range Ko 4  comprises a second part of the excitation spectrum  33  of the fluorescent dye. In the present exemplary embodiment, the seventh channel Ch 7  extends from approximately 350 nm to 540 nm. This approximately corresponds to the blue channel of a conventional RGB color camera. 
     Consequently, different parts of the emission spectrum can be detected separately from one another by different detectors, specifically the first and second fluorescent light image detectors. 
     The illumination light  5  has at most the first intensity W 1  in the second emission wavelength range Em 2 . Furthermore, the illumination light  5  has at least the second intensity in the third correction wavelength range Ko 3  and in the fourth correction wavelength range Ko 4 . 
     The second optical unit  111 , which comprises the objective  21  and a second beam splitter  123 , is configured to image light of the second emission wavelength range Em 2  emanating from the object region (substantially only) onto the fifth detection region, to image light of the third correction wavelength range Ko 3  emanating from the object region (substantially only) onto the sixth detection region, and to image light of the fourth correction wavelength range Ko 4  emanating from the object region (substantially only) onto the seventh detection region. In particular, the second beam splitter  123  can be a dichroic beam splitter having a second limit wavelength λ 2  or be configured like the first beam splitter  23 . 
     The controller  29  is furthermore configured to determine the approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region  7  using furthermore the second fluorescent light signal, the third correction signal and the fourth correction signal. 
       FIG. 5  shows a further exemplary embodiment of a microscopy system  200  for simultaneously recording an overview image and determining the concentration of a fluorescent dye in tissue in an object region. 
     Components of the microscopy system  200 , which are identical to those of the microscopy system  1  shown in  FIG. 1 , have been denoted with the same reference signs, and reference is made to their description. 
     The microscopy system  200  comprises the illumination apparatus  3 , which is configured to produce illumination light  5  and to direct it onto the object region  7 . 
     The microscopy system  200  comprises a first optical unit  211 , which comprises an objective  21  and is configured to image light emanating from the object region  7  onto a first multichannel image detector  203 . The first optical unit  211  can comprise an image-forming lens  25 , as is shown in  FIG. 5 . The first optical unit  211  can furthermore comprise a zoom system (not illustrated). 
     The first multichannel image detector  203  is configured to detect light of a first channel Ch 1  in a first detection region D 1  and to convert it to a first fluorescent light signal, to detect light of a second channel Ch 2  in a second detection region D 2  and to convert it to a first correction signal, and to detect light of a third channel Ch 3  in a third detection region D 3  and to convert it to a second correction signal. The channels of the first multichannel image detector  203  substantially do not spectrally overlap, with the result that each of the detection regions substantially exclusively detects the channel it is assigned. In this way, different spectral ranges can be detected at the same time. 
     For two adjoining or partially overlapping channels M and N, for example the following condition may apply: 
     
       
         
           
             
               
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                       S 
                       M 
                     
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                       ( 
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                       S 
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             wherein
           S M  represents the sensitivity of the detection region for the channel M which has been normalized to the maximum sensitivity,   S N  represents the sensitivity of the detection region for the channel N which has been normalized to the maximum sensitivity,   λ represents the wavelength, and   W is 20%, typically 10%, more typically 1%.   
         
           
         
       
    
     An exemplary embodiment of the configuration of the first multichannel image detector  203  is illustrated in  FIGS. 6 and 7 .  FIG. 6  shows an exemplary embodiment of a spatial arrangement of the detection regions D 1 , D 2 , D 3 , and D 4  of the first multichannel image detector  203 . In this exemplary embodiment, the first multichannel image detector  203  has a further, fourth detection region D 4  with which the first multichannel image detector  203  is configured to detect light of a fourth channel Ch 4  and to output a corresponding signal. The first detection region D 1  consists of a multiplicity of regularly arranged pixels. The second detection region D 2 , the third detection region D 3  and the fourth detection region D 4  likewise each consist of regularly arranged pixels, wherein the different detection regions do not spatially overlay one another. 
       FIG. 7  shows the channels of the first multichannel image detector  203 . In other words,  FIG. 7  shows as channels those wavelength ranges in which the respective detection regions have a significant sensitivity for light. A sensitivity can, for example, be considered to be significant for a specific wavelength if the sensitivity at this wavelength is at least 10%, typically at least 30% of the maximum sensitivity of the detection region. 
     In the present exemplary embodiment, the first detection region D 1  is configured to detect light in a wavelength region around 635 nm (first channel Ch 1 ). In particular, the first channel Ch 1  comprises a wavelength range from 610 nm to 650 nm. 
     The fourth detection region D 4  is configured to detect light of a wavelength region around 705 nm (fourth channel Ch 4 ). In particular, the fourth channel comprises a wavelength range from 650 nm to 720 nm. 
     The second detection region D 2  is configured to detect light of a wavelength region around 600 nm (second channel Ch 2 ). In particular, the second channel Ch 2  comprises a wavelength range from 560 nm to 610 nm. 
     The third detection region D 3  is configured to detect light of a wavelength region around 405 nm (third channel Ch 3 ). In particular, the third channel Ch 3  comprises a wavelength range from 390 nm to 450 nm. 
     The spectral configuration of the individual detection regions can be achieved, for example, by bandpass filters, the production of which is known to a person skilled in the art. 
     Again with reference to  FIG. 5 , the illumination apparatus  3  is configured to produce the illumination light  5  such that it has at most a first intensity W 1  in a first emission wavelength range Em 1 , which is part of the emission spectrum  35  of the fluorescent dye (cf.  FIG. 2 ) and is contained in the first channel Ch 1 . The first emission wavelength range Em 1  extends from λEm 1 L to λEm 1 H. 
     Furthermore, the illumination light  5  has at least a second intensity W 2  in a first correction wavelength range Ko 1  and in a second correction wavelength range Ko 2 . The first correction wavelength range Ko 1  is contained in the second channel Ch 2 ; and the second correction wavelength range Ko 2  is contained in the third channel Ch 3 . The first correction wavelength range Ko 1  is situated near the first emission wavelength range Em 1 , for example between λEm 1 L−150 nm and λEm 1 +150 nm and does not overlap the first emission wavelength range Em 1 . The second correction wavelength range Ko 2  comprises a part of the excitation spectrum of the fluorescent dye. The first intensity W 1  is lower than the second intensity W 2  by at least a factor of 2. This is illustrated by way of example in diagram  41  of  FIG. 2 . 
     The microscopy system  200  furthermore comprises a controller  29 , which is configured to determine an approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region  7  using the first fluorescent light signal, the first correction signal and the second correction signal. 
     As illustrated in  FIGS. 6 and 7 , the first multichannel image detector  203  has the fourth detection region D 4 , which is configured to detect light of the fourth channel Ch 4 . The fourth channel can be selected for example such that it comprises a second emission wavelength range Em 2 , which is a second part of the emission spectrum of the fluorescent dye and does not overlap the first emission wavelength range. In this way it is possible to sample the emission spectrum in a plurality of different wavelength ranges, and a plurality of fluorescent light signals are then available for determining the approximation value for the spatial distribution of the concentration of the fluorescent dye. For example, the second emission wavelength range Em 2  can comprise a wavelength range from 670 nm to 710 nm and can comprise in particular the wavelength 705 nm. 
     Alternatively, the fourth channel Ch 4  can be configured to detect a wavelength range situated in the visible spectral range outside the emission spectrum ( 35 ) of the fluorescent dye, outside the second channel Ch 2  and outside the third channel Ch 3  in order to improve hereby the color fidelity of the overview image. For example, the fourth channel Ch 4  can comprise a wavelength region around 500 nm to detect a wavelength range of green light. 
     As a further alternative, the multichannel image detector  203  can be configured such that the first channel Ch 1  and the fourth channel Ch 4  spectrally partially overlap. In this way it is also possible for the first emission wavelength range Em 1  and the second emission wavelength range Em 2  to spectrally partially overlap. The overlap between the first emission wavelength range Em 1  and the second emission wavelength range Em 2  can be, for example, at most 50 nm, in particular at most 20 nm or at most 10 nm. The overlap between the first channel Ch 1  and the fourth channel can be, for example, at most 100 nm, in particular at most 50 nm or at most 20 nm. 
     As illustrated in  FIG. 5 , the microscopy system  200  can be in the form of a stereo microscopy system. Here, the microscopy system  200  furthermore has a second optical unit  311 , which is configured to image the object region  7  onto a second multichannel image detector  303 . The second multichannel image detector  303  can be configured to be similar or identical to the first multichannel image detector  203 . 
     A further exemplary embodiment will be described below with reference to  FIGS. 1, 8 and 9 . The microscopy system in accordance with this exemplary embodiment substantially corresponds to the microscopy system  1  shown in  FIG. 1 , wherein the illumination light  5 , the first optical unit  11 , the second optical unit  111  and the first detection system  9  and the second detection system  109  have a different spectral configuration, which is illustrated in  FIGS. 8 and 9 . 
     The microscopy system  1  comprises a first detection system  9 , which comprises a first fluorescent light image detector  17  and a first multichannel image detector  19 . The first fluorescent light image detector  17  is configured to detect light of a first channel Ch 1  in a first detection region and to convert it to a first fluorescent light signal. The first multichannel image detector  19  is configured to detect light of a second channel Ch 2  in a second detection region and to convert it to a first correction signal. 
     The illumination apparatus  3  is configured to produce illumination light  5  and to direct it onto the object region  7 . 
       FIG. 8  shows an exemplary embodiment of a spectral configuration of the microscopy system. Diagram  31  shows the spectral configuration of the fluorescent dye. Diagram  41  shows the spectral intensity distribution of the illumination light  5 . 
     Diagram  51  shows the spectral configuration of the first detection region of the first fluorescent light image detector  17 . Diagram  52  shows the spectral configuration of the second detection region of the first multichannel image detector  19 . Diagram  53  shows the spectral configuration of a third detection region of the first multichannel image detector  19 . 
     As illustrated in diagram  41 , the illumination light  5  has at least a second intensity W 2  in a correction wavelength range Ko and has at most a first intensity W 1  in a first emission wavelength range Em 1 . With this configuration of the illumination light  5 , the fluorescent dye is substantially excited in the wavelength range Ko. That means that the correction wavelength range Ko comprises at least a part of the excitation spectrum  33  of the fluorescent dye. In addition, the correction wavelength range Ko is situated between λEm 1 L−15 nm and λEm 1 H+150 nm, wherein the first emission wavelength range Em 1  extends from λEm 1 L to λEm 1 H and is a first part of the emission spectrum  35  of the fluorescent dye. The first emission wavelength range Em 1  and the correction wavelength range Ko do not spectrally overlap. 
     Again with reference to  FIG. 1 , the first optical unit  11  is configured to simultaneously image light of the first emission wavelength range Em 1  emanating from the object region  7  onto the first detection region of the first fluorescent light image detector  17  and image light of the correction wavelength range Ko emanating from the object region  7  onto the second detection region of the multichannel image detector  19 . 
     As is illustrated in  FIG. 8 , the first channel Ch 1  of the first fluorescent light image detector  17  comprises the first emission wavelength range Em 1 . Furthermore, the second channel Ch 2  of the first multichannel image detector  19  comprises the correction wavelength range Ko. 
     In accordance with this configuration, the fluorescent dye is excited in the wavelength range Ko. For example, the correction wavelength range Ko comprises the wavelength 630 nm, at which the fluorescent dye PPIX has a local absorption maximum. The correction wavelength range Ko typically comprises a wavelength range from 620 nm to 650 nm, more typically a wavelength range from 610 nm to 660 nm. 
     The fluorescent dye excited in this manner emits fluorescent light in a secondary maximum around 705 nm. Consequently, the first emission wavelength range Em 1  comprises the wavelength 705 nm. The first emission wavelength range typically comprises a wavelength range from 680 nm to 710 nm, more typically from 670 nm to 720 nm. 
     The microscopy system  1  furthermore comprises the beam splitter  23 , which can, for example, be configured as a dichroic beam splitter having a limit wavelength λ 1  of, for example, 660 nm. Alternatively, the first beam splitter  23  can be a conventional beam splitter, and the microscopy system  1  can furthermore comprise filters, such that the beam splitter  23 , in connection with the filters, images light of the emission wavelength range Em 1  substantially only onto the first fluorescent light image detector  17  and images light of the correction wavelength range Ko substantially only onto the multichannel image detector  19 . The limit wavelength of the first beam splitter  23  is correspondingly situated between the first emission wavelength range Em 1  and the correction wavelength range Ko, typically between 600 nm and 700 nm, more typically between 655 nm and 675 nm, even more typically at 660 nm. 
     Due to this spectral configuration, light of the first emission wavelength range Em 1  emanating from the object region  7  is imaged substantially only onto the first detection region and thus detected in the first channel Ch 1 . The light of the correction wavelength range Ko emanating from the object region  7  is consequently imaged substantially only onto the second detection region and detected in the second channel Ch 2 . 
     To produce an overview image with high color fidelity, the illumination light  5  has, in a supplementary wavelength range G 2 , an average fifth intensity W 5  which is lower than the second intensity W 2  but higher than the first intensity W 1 . The average fifth intensity can be, for example, 0.01% to 50% of the second intensity W 2 , typically 0.05% to 10% of the second intensity W 2 , more typically 0.1% to 1% of the second intensity W 2 . 
     The first optical unit  11  furthermore comprises a first optical filter  61 , which is arranged between the first beam splitter  23  and the first multichannel image detector  19 .  FIG. 9  shows the spectral configuration of the first optical filter  61 . An average transmittance of the first optical filter  61  in the correction wavelength range Ko is 0.01% to 50% of an average transmittance of the first optical filter  61  in the supplementary wavelength range G 2 . An average transmittance of the first optical filter in the first emission wavelength range Em 1  can be lower than the average transmittance of the first optical filter  61  in the correction wavelength range Ko by a factor of at least 10. An average transmittance of the first optical filter  61  in the correction wavelength range typically has 0.05% to 10% of the average transmittance of the first optical filter  61  in the supplementary wavelength range G 2 , more typically 0.1% to 1% of the average transmittance of the first optical filter  61  in the supplementary wavelength range G 2 . An average transmittance of the first optical filter  61  in the first emission wavelength range Em 1  is typically lower than the average transmittance of the first optical filter  61  in the correction wavelength range Ko by at least a factor of 100, more typically 1,000. 
     The first multichannel image detector  19  can furthermore be configured to detect light of at least one third channel Ch 3  in at least one third detection region and convert it into at least one color signal, wherein the at least one third channel Ch 3  at most partially overlaps the second channel Ch 2  and wherein the at least one third channel Ch 3  at least partially comprises the supplementary wavelength range G 2 . In the exemplary embodiment illustrated in  FIG. 8 , diagram  53  shows the spectral configuration of the third detection region of the first multichannel image detector  19 . The third channel Ch 3  at least partially comprises the supplementary wavelength range G 2 . As in the preceding exemplary embodiments, the first multichannel image detector  19  can be a conventional RGB color camera. 
     In a development of the microscopy system  1  illustrated in  FIG. 1 , provided instead of the fluorescent light image detector  17  or  117  is a further multichannel image detector, which is configured to detect at least two different emission wavelength ranges in at least two different channels and to output a separate fluorescent light signal for each channel. For example, this multichannel image detector is configured to detect in one channel a wavelength region around the wavelength 635 nm and to detect in a further channel the wavelength around 705 nm. The fluorescent light signals thus provided can then be used, as described above, to determine the approximation value for the spatial distribution of the concentration of the fluorescent dye in the object region. 
     In the exemplary embodiments explained above, the first emission wavelength range Em 1  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. The first correction wavelength range Ko 1  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. The second correction wavelength range Ko 2  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. 
     Furthermore, the second emission wavelength range Em 2  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. The third correction wavelength range Ko 3  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. The fourth correction wavelength range Ko 4  can have a width of at least 10 nm, at least 20 nm, at least 50 nm or at least 100 nm. 
     In accordance with a further exemplary embodiment, the first limit wavelength λ 1  of the first beam splitter  23  and/or the second limit wavelength λ 2  of the second beam splitter  123  can be located in a wavelength range from 600 nm to 700 nm, in particular at 660 nm. 
     Arranged between the first beam splitter ( 23 ) and the first fluorescent light image detector ( 17 ) in accordance with a further exemplary embodiment is a second optical filter having a transmission behaviour which simulates that of the first beam splitter ( 23 ). Alternatively, the second optical filter can be configured to transmit substantially only light of the emission wavelength ranges and to suppress light outside the emission wavelength ranges. A further second optical filter can be arranged between the second beam splitter ( 123 ) and the second fluorescent light image detector ( 117 ). 
     The foregoing description of the exemplary embodiments of the disclosure illustrates and describes the present invention. Additionally, the disclosure shows and describes only the exemplary embodiments but, as mentioned above, it is to be understood that the disclosure is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art. 
     The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of.” The terms “a” and “the” as used herein are understood to encompass the plural as well as the singular. 
     All publications, patents and patent applications cited in this specification are herein incorporated by reference, and for any and all purposes, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.