Endoscopic System to Capture Images of a Medical Site in White Light and Fluorescent Light

Abstract

A device for capturing an image of an object of medical interest in remitted or reflected illumination light and for capturing an image of the object in fluorescent light generated by Cy5.5 and/or SGM-101 and for capturing an image in fluorescent light generated OTL38 and/or indocyanine green (ICG). The device includes an image sensor for detecting blue, green and red light, another image sensor for detecting fluorescent light of Cy5.5 and/or SGM-101 and OTL38 and/or ICG, a beam splitter guiding light having a wavelength smaller than a predetermined cutoff wavelength to the first sensor and guiding light having a wavelength greater than the predetermined cutoff wavelength to the second sensor, and filters upstream of the second sensor for partially, substantially or completely suppressing light having a wavelength exciting Cy5.5 and/or SGM-101 and for partially, substantially or completely suppressing light having a wavelength suitable for exciting fluorescence of OTL38 and/or ICG.

Claims

1. An endoscopic system for capturing an image of an object of medical interest in remitted or reflected illumination light and for capturing an image of the object in fluorescent light generated by at least one of Cy5.5 and SGM-101 and for capturing an image of the object in fluorescent light generated by at least one of OTL38 and indocyanine green, comprising: an endoscope comprising an objective lens to collect an image light from the object of medical interest; and an image capturing system comprising a first image sensor configured to detect light in the blue, green, and red spectra light, and a second image sensor configured to detect a first fluorescent light with a wavelength longer than a predetermined cutoff wavelength .sub.0, a beam splitter configured to direct light collected from the object of medical interest a wavelength that is shorter than the cutoff wavelength .sub.0 to the first image sensor and to direct light with a wavelength longer than the predetermined cutoff wavelength to the second image sensor, wherein the cutoff wavelength is within a red spectral band and having a wavelength between 640-690 nm, and one or more filters arranged upstream of the second image sensor and downstream of the objective lens configured to suppress a first excitation wavelength range between 660-700 nm, and configured to suppress a second excitation a wavelength range between 760 and 850 nm.

2. The endoscopic system of claim 1, wherein the first excitation range is between 660-690 nm, and the second excitation range is between 760-790 nm.

3. The endoscopic system of claim 1, wherein the first excitation range is between 660-690 nm, and the second excitation range is between 700-850 nm.

4. The endoscopic system of claim 1, wherein the first excitation range is between 660-700 nm, and the second excitation range is between 760-790 nm.

5. The endoscopic system of claim 1, wherein the first excitation range is between 660-700, and the second excitation range is between 700-850 nm.

6. The endoscopic system of claim 1, wherein the endoscope is a video endoscope whereby the image capturing system is an element of the endoscope.

7. The endoscopic system of claim 1, wherein the image capturing system is an element of a camera that is detachably connectable to an eyepiece of the endoscope.

8. The image capturing device of claim 1, wherein the cutoff wavelength .sub.0 is shorter than 690 nm.

9. The image capturing device of claim 1, wherein the cutoff wavelength .sub.0 is shorter than 705 nm.

10. The image capturing device of to claim 1, wherein the cutoff wavelength 20 is not shorter 630 nm and not longer than 690 nm.

11. The image capturing device of claim 1, wherein the filters complete block the suppressed light.

12. The endoscopic system of claim 1, further comprising a light source for generating illumination light in the blue, green and red wavelength ranges, a first excitation light and second excitation light

13. The endoscopic system of claim 12, wherein the first excitation light is of a first excitation wavelength of between 660-690 nm and does not include illumination outside of first excitation wavelength range.

14. The endoscopic system of claim 12, wherein the first excitation light is of a first excitation wavelength of between 660-700 nm and does not include illumination outside of first excitation wavelength range.

15. The endoscopic system of claim 12, wherein the second excitation light is of a second excitation wavelength of between 760-790 nm and does not include illumination outside of second excitation wavelength range.

16. The endoscopic system of claim 12, wherein the second excitation light is of a second excitation wavelength of between 700-850 nm and does not include illumination outside of second excitation wavelength range.

17. The endoscopic system of claim 13, wherein the second excitation light is of a second excitation wavelength of between 760-790 nm and does not include illumination outside of second excitation wavelength range.

18. The endoscopic system of claim 13, wherein the second excitation light is of a second excitation wavelength of between 700-850 nm and does not include illumination outside of second excitation wavelength range.

19. The endoscopic system of claim 14, wherein the second excitation light is of a second excitation wavelength of between 760-790 nm and does not include illumination outside of second excitation wavelength range.

20. The endoscopic system of claim 14, wherein the second excitation light is of a second excitation wavelength of between 700-850 nm and does not include illumination outside of second excitation wavelength range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 is a schematic representation of an image capturing system.

[0059] FIG. 2 is a schematic representation of spectra generated by a light source device of the imaging system shown in FIG. 1.

[0060] FIG. 3 is a schematic representation of spectral characteristics of a beam splitter and filters of the imaging system shown in FIG. 1.

[0061] FIG. 4 is a schematic flowchart of a method of capturing images.

[0062] FIG. 5 is a schematic flowchart of another method of capturing images.

[0063] FIG. 6 is a schematic flowchart of another method of capturing images.

[0064] FIG. 7 is a schematic flowchart of another method of capturing images.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

[0065] FIG. 1 shows a schematic representation of an image capturing system 10 for capturing an image of an object of medical interest 12 in remitted or reflected illumination light, for capturing an image of the object in fluorescent light emanating from Cy5.5 or SGM-101, and for capturing an image in fluorescent light emanating from OTL38 or indocyanine green. The object 12 may be placed inside a cavity or at a surface of a body of a human or animal patient. Accordingly, the imaging system 10 may be located entirely or partially inside or entirely outside a body of a human or animal patient.

[0066] The image capturing system 10 may, for example, be an endoscope, exoscope or surgical microscope or may include an endoscope, exoscope or surgical microscope.

[0067] The observation of fluorescent light, in particular the observation of images in fluorescent light, can enable or simplify a diagnosis. Some fluorophores, when administered to a patient have a higher concentration in tumors than in healthy tissue, so that the fluorescence of one of these fluorophores can be used to differentiate between healthy tissue and neoplasia. Some fluorophores, for example indocyanine green, have a higher concentration in vessels, so that in the fluorescent light of one of these fluorophores, the vascular system can be particularly well distinguished from surrounding tissue. Some fluorophores facilitate the detection or differentiation of other tissue types, functions or dysfunctions.

[0068] The image capturing system 10 comprises a light source device 20 having a first light source 21, a second light source 22, a third light source 23, a first dichroic reflecting surface 24 and a second dichroic reflecting surface 25. In FIG. 1, it is suggested that each of the light sources 21, 22, 23 comprises a light emitting diode for generating light. Each light source 21, 22, 23 may alternatively or additionally comprise one or more semiconductor lasers or other lasers, further light-emitting diodes or other light sources.

[0069] The first light source 21 is for the generation of broadband illumination light, the spectrum of which has components in the wavelength range perceived as blue by the healthy human eye, in the wavelength range perceived as green by the healthy human eye and in the wavelength range perceived as orange to red by the healthy human eye. For this purpose, the first light source 21 comprises, for example, one or more light-emitting diodes originally emitting in the wavelength range perceived by the healthy human eye as blue or violet, and a luminescence layer which absorbs part of the blue or violet light and emits light in the wavelength ranges perceived by the healthy human eye as red and green. As an alternative, the first light source 21 has, for example, several light-emitting diodes, each emitting approximately monochromatic, i.e. narrow-band light at different wavelengths, which together cover the widest possible range of wavelengths between a lower limit at about 380 nm to 400 nm and an upper limit at about 700 nm to 750 nm.

[0070] The second light source 22 is provided and configured to emit narrow-band first excitation light for excitation of fluorescence of at least one of Cy5.5 and SGM-101. For this purpose, the second light source 22 emits light that is as narrow-banded as possible and as intense as possible within the wavelength range from approximately 660 nm to approximately 700 nm, for example at approximately 675 nm, the absorption maximum of Cy5.5, or at approximately 680 nm, the absorption maximum of SGM-101. The second light source 22 can be configured to emit excitation light exciting both fluorescence of Cy5.5 and the fluorescence of SGM-101.

[0071] The third light source 23 is provided and configured to emit narrow-band second excitation light for excitation of fluorescence of at least one of OTL38 and indocyanine green. For this purpose, the third light source 23 in particular emits light that is as narrow-band as possible and as intense as possible within the wavelength range between 700 nm and 850 nm, for example at approximately 774 nm or 776 nm, the absorption maximum of OTL38, or at approximately. 800 nm, the absorption maximum of indocyanine green. The third light source 23 can be configured to emit excitation light exciting both fluorescence of OTL38 and the fluorescence of indocyanine green.

[0072] The first dichroic reflecting surface 24 reflects illumination light emitted by the first light source 21 completely or as much as possible and transmits first excitation light emitted by the second light source 22 completely or as much as possible, so that the illumination light produced by the first light source 21 and the first excitation light produced by the second light source 22 are superimposed as completely as possible. The second dichroic reflecting surface 25 reflects second excitation light emitted by the third light source 23 completely or as much as possible and transmits illumination light generated by the first light source 21 and first excitation light generated by the second light source 22 completely or as much as possible, so that the illumination light generated by the first light source 21, the first excitation light generated by the second light source 22 and the second excitation light generated by the third light source 23 are superimposed as completely as possible. The light of the light sources 21, 22, 23 which is superimposed as completely as possible, i.e. combined, is coupled into a fiber optic cable 26 and directed onto the object 12.

[0073] The dichroic reflecting surfaces 24, 25 of light source device 20 are examples of devices for superimposing or combining the light produced by light sources 21, 22, 23. Alternatively, polarization-dependent reflecting surfaces or other devices may be used, especially when the light sources 21, 22, 23 produce polarized light.

[0074] The image capturing system 10 further comprises an image capturing device 30. The image capturing device 30 can be a camera or part of a camera. As an alternative, the image capturing device 30 can be an endoscope or an exoscope or a surgical microscope or part of an endoscope or an exoscope or a surgical microscope.

[0075] The image capturing device 30 comprises an objective 40 for imaging the object 12, i.e. for generating a real image of the object 12, and a beam splitter 50 with a dichroic reflecting surface 51 in a prism which is otherwise optically transparent. Downstream of the beam splitter 50, an optional first filter 56 is arranged in front of a first image sensor 60 and a second filter 57 is arranged in front of a second image sensor 70. The objective 40 generates real images of the object 12 in light-sensitive layers 62, 72 of the image sensors 60, 70. As an example, the light-sensitive layers 62, 72 of the image sensors 60, 70 are shown as surfaces of the image sensors 60, 70 facing the beam splitter 50.

[0076] The dichroically reflecting surface 51 of the beam splitter 50 causes an image of the object 12 in remitted or reflected illumination light from the first light source 21, hereinafter referred to as the color image, to be formed in the light-sensitive layer 62 of the first image sensor 60, and an image of the object 12 in fluorescent light emitted by the object 12, hereinafter referred to as the fluorescence image, to be formed in the light-sensitive layer 72 of the second image sensor 70. For this purpose, the dichroic reflecting surface 51 of the beam splitter 50 reflects substantially completely and substantially exclusively light with wavelengths smaller than a cutoff wavelength .sub.0 and transmits substantially completely and substantially exclusively light with wavelengths larger than the cutoff wavelength . The cutoff wavelength .sub.0 is in the range from 630 nm to 700 nm, in particular at 670 nm to 690 nm. As a result, part of the light remitted or reflected by the object 12 within the light perceived by the healthy human eye as orange or red falls on the first image sensor 60 and is detected in its red color channel. Therefore, the color image captured by the first image sensor 60 alone can produce an essentially normal or natural color impression.

[0077] Both fluorescent light generated by Cy5.5 or SGM-101 in the object 12 and fluorescent light generated by OTL38 or indocyanine green in the object 12 is detected by the second image sensor 70. The second image sensor 70 can be a monochromatic image sensor, i.e. it can have only one color channel. Alternatively, the second image sensor 70 can have several color channels, one of which exclusively or substantially exclusively detects the fluorescence of at least one of Cy5.5 and SGM-101 and another exclusively or substantially exclusively detects the fluorescence of at least one of OTL38 and indocyanine green.

[0078] The second filter 57 in front of the second image sensor 70 is provided and configured to suppress both first excitation light generated by the second light source 22 and remitted by the object 12. For this purpose, the second filter 57 suppresses in particular light in a wavelength range whose lower limit is at 650 nm to 670 nm and whose upper limit is at 690 nm to 710 nm, which is as narrow as possible and comprises the spectrum of the first excitation light generated by the second light source 22 as completely as possible.

[0079] Furthermore, the second filter 57 is provided and configured to suppress second excitation light generated by the third light source 23 and remitted by the object 12. For this purpose, the second filter 57 suppresses in particular light in a wavelength range whose lower limit is at 750 nm to 770 nm and whose upper limit is at 800 nm to 820 nm, which is as narrow as possible and comprises the spectrum of the second excitation light generated by the third light source 23 as completely as possible.

[0080] The second filter 57 may be designed to suppress only a large part, but not all, of the light produced by the second light source 22 and reflected or remitted by the object 12. Furthermore, the second filter 57 may be designed to suppress only a large part, but not all, of the light produced by the third light source 23 and reflected or remitted by the object 12. In this way, the remission or reflection characteristics of the object 12 at the wavelengths suppressed by the second filter 57 can also contribute to the formation of the color image in the light-sensitive layer 72 of the second image sensor 70.

[0081] The first image sensor 60 provides, at an image signal output 68, a first image signal representing the color image captured by the first image sensor 60. The second image sensor 70 provides, at an image signal output 78, a second image signal representing the fluorescence image captured by the second image sensor 70.

[0082] The image capturing system 10 further comprises a Camera Control Unit (CCU) 80 having a first control output 81 coupled to the first light source 21, a second control output 82 coupled to the second light source 22, a third control output 82 coupled to the third light source 23, a first image signal input 86 coupled to the image signal output 68 of the first image sensor 60, a second image signal input 87 coupled to the image signal output 78 of the second image sensor 70, and an image signal output 88. The camera control unit 80 controls the light sources 21, 22, 23 of the light source device 20 and the image sensors 60, 70, receives and processes the image signals provided by the image sensors 60, 70 and provides, at an image signal output 88, an image signal containing information from both image signals provided by the image sensors 60, 70.

[0083] In particular, the image signal provided by the camera control unit 80 at image signal output 88 represents a color image of the object in which tissue recognizable by the fluorescence of Cy5.5 or SGM-101 and/or vessels or other structures or tissue characteristics recognizable by the fluorescence of OTL38 or indocyanine green are highlighted. The highlighting can be done by color, intensity or a time-dependent modulation for example.

[0084] In particular, the camera control unit 80 controls one of the processes illustrated in FIGS. 4, 5 and 6.

[0085] FIG. 2 shows a schematic representation of the emission spectra of the light sources 21, 22, 23. The wavelength in nm is assigned to the abscissa, the intensity I in arbitrary or relative units is assigned to the ordinate.

[0086] The spectrum 91 of the first light source 21 (cf. FIG. 1) or of the illumination light provided by the first light source 21, shown in a solid line, essentially comprises wavelengths between 350 nm and 750 nm and is essentially constant, i.e. wavelength-independent, between these limits in the example shown.

[0087] The spectrum 92 of the second light source 22 or of the first excitation light provided by the second light source 22, shown in a short dashed line, is narrowband. In the example shown, the spectrum 92 of the second light source 22 has a maximum at 675 nm or 680 nm.

[0088] The spectrum 93 of the third light source 23, i.e. of the second excitation light produced by the third light source 23, is shown in a longer dashed line and is narrowband. In the example shown, the spectrum 93 of the third light source has a maximum at about 770 nm to 800 nm.

[0089] FIG. 3 shows a schematic representation of the transmission characteristics of the dichroic surface 51 of the beam splitter 50 and the filters 56, 57 (cf. FIG. 1). The wavelength in nm is assigned to the abscissa, the transmission T is assigned to the ordinate.

[0090] The transmission 95 of the dichroic reflecting surface 51 of the beam splitter 50, shown in a solid line, is low, i.e. essentially 0, at wavelengths less than a cutoff wavelength .sub.0 of about 650 nm, and high, i.e. essentially 1=100%, at wavelengths greater than the cutoff wavelength .sub.0 of 650 nm. The reflection R not shown is complementary to the transmission 95, i.e. it is approximately R=1T.

[0091] The transmission 97 of the second filter 57, shown in a longer dashed line, in front of the second image sensor 70 is low, in particular substantially 0, in a wavelength range between about 670 nm and about 690 nm in order to completely or substantially completely suppress first excitation light generated by the second light source 22 and reflected or remitted by the object 12. Furthermore, the transmission 97 is low, in particular substantially 0, in a wavelength range between about 760 nm and about 800 nm or 810 nm in order to completely or substantially completely suppress second excitation light generated by the third light source 23 and reflected or remitted by the object 12. At wavelengths greater than about 800 nm or 810 nm and at wavelengths between about 690 nm and about 760 nm, the transmission 97 of the second filter 57 is high, in particular substantially 1=100%. In the example shown, the transmission 97 of the second filter 57 is also high at wavelengths below about 670 nm, in particular essentially 1.

[0092] Both the spectra 91, 92, 93 of the light sources 21, 22, 23 and the transmission spectra 95, 97 may be slightly shifted with respect to the wavelengths shown in FIGS. 2 and 3. However, the spectra 92, 93 of the second light source 22 and the third light source 23 should be selected in such a way that the fluorescence of Cy5.5 and/or SGM-101 and the fluorescence of OTL38 and/or indocyanine green are excited as efficiently and as narrowly as possible. Furthermore, the transmission spectrum 95 and the complementary reflection spectrum of the beam splitter 50 are to be selected in such a way that as much as possible of the illumination light generated by the first light source 21, but as little as possible, in particular no, fluorescence light generated by Cy5.5 or SGM-101 or OTL38 or indocyanine green falls on the first image sensor 60. Furthermore, the transmission spectrum 97 of the second filter 57 is to be selected in such a way that both first excitation light generated by the second light source 22 and reflected or remitted by the object 12 and second excitation light generated by the third light source 23 and reflected or remitted by the object 12 falls on the second image sensor 70 to the smallest possible extent.

[0093] As an alternative to the spectra represented in FIG. 2, the spectrum 91 of the illumination light provided by the first light source 21 can provide a lower or much lower or even vanishing intensity at wavelengths greater than the cutoff wavelength .sub.0. In this case, the second image sensor 70 receives little or no remitted or reflected illumination light, but mainly or exclusively fluorescent light.

[0094] As a further alternative, the cutoff wavelength .sub.0 can be higher. In particular, the cutoff wavelength .sub.0 can be set to about 690 nm which is between the maximum of the spectrum 92 of the second light source 22 and the maximum of the intensity of the fluorescent light emitted by Cy5.5 and/or SGM-101. In this case, the second filter 57 is not required to suppress the first excitation light. If the first filter 56 suppresses the first excitation light, a color image can be captured simultaneously with the first fluorescence image.

[0095] The second filter 57 can comprise a plurality of filters, wherein each filter of the plurality of filters can be embodied by one or more layers or films on the very same transparent substrate or on different substrates. For instance, one filter of the plurality of filters suppresses the first excitation light, and one filter of the plurality of filters suppresses the second excitation light.

[0096] Each of the first filter 56 and the second filter 57 can be located upstream the lens 40 or between the lens 40 and the beam splitter 50. If the second filter 57 comprises a plurality of filters, one or more of the plurality of filters can be located upstream the lens 40 or between the lens 40 and the beam splitter 50 and one or more of the plurality of filters can be located between the beam splitter 50 and the second image sensor 70.

[0097] FIG. 4 shows a schematic flowchart of a method of capturing an image of an object of medical interest 12 in remitted or reflected illumination light, of capturing an image of the object 12 in fluorescent light generated by at least one of Cy5.5 and SGM-101, and of capturing an image of the object in fluorescent light generated by at least one of OTL38 and indocyanine green. In particular, the method can be carried out with the image capturing system 10 shown in FIGS. 1 to 3 and controlled by the camera control unit 80 of the image capturing system 10, but alternatively also with a system having features, properties and functions differing from the image capturing system shown in FIGS. 1 to 3. Reference signs from FIGS. 1 to 3 are used as examples.

[0098] In a method step 101, the object 12 is irradiated with illumination light with a broad spectrum 91, which comprises components in the wavelength ranges perceived by the healthy human eye as blue, green and orange to red. In a further method step 102 carried out at the same time, the object 12 is irradiated with the first excitation light to excite the fluorescence of at least one of Cy5.5 and SGM-101. In a further method step 103 carried out simultaneously, the object 12 is irradiated with second excitation light for exciting the fluorescence of at least one of OTL38 and indocyanine green. In a further method step 106 carried out at the same time, a color image in remitted and reflected illumination light in the spectral ranges perceived by the healthy human eye as blue, green and orange to red is captured by a first image sensor 60. In a further method step 107 carried out simultaneously, an image of the object 12, referred to as a fluorescence image, in fluorescent light generated by at least one of Cy5.5 and SGM-101 and/or in fluorescent light generated by at least one of OTL38 and indocyanine green is captured by a second image sensor 70. The fluorescence of at least one of Cy5.5 and SGM-101 and the fluorescence of at least one of OTL38 and indocyanine green can be detected together in a monochrome fluorescence image or in two different color channels of a fluorescence image.

[0099] In a further method step 111, an image signal is generated which contains both information from the color image and information from the fluorescence image.

[0100] In a further method step 112, an image is displayed, controlled by the image signal generated in the method step 111, for example by one or more screens, a projector and/or VR (virtual reality) glasses.

[0101] Deviating from the illustration in FIG. 4, it is not necessary to generate the broadband illumination light and the first excitation light and the second excitation light simultaneously and to capture the color image and the fluorescence image simultaneously. Especially when the fluorescence image is captured by a monochrome image sensor 70 having only one color channel in which both the fluorescence of at least one of Cy5.5 and SGM-101 and the fluorescence of at least one of OTL38 and indocyanine green is detected, only partial simultaneity may be advantageous to distinguish the fluorescence of at least one of Cy5.5 and SGM-101 and the fluorescence of at least one of OTL38 and indocyanine green. Furthermore, only partial simultaneity, deviating from the representation in FIG. 4, can allow correction of the image signal in the red color channel and thus allow better color rendering. Examples of such modified methods are shown in FIGS. 5 and 6.

[0102] FIG. 5 shows a schematic diagram of a flow chart of a further method of capturing an image of an object of medical interest 12 in remitted or reflected broadband illumination light, of capturing an image of the object in fluorescent light generated by at least one of Cy5.5 and SGM-101 and of capturing an image of the object in fluorescent light generated by at least one of OTL38 and indocyanine green.

[0103] The method shown in FIG. 5 differs from the method shown in FIG. 4 in that initially, in a first time interval, only the irradiation 101 with illumination light, the irradiation 102 with first excitation light, the capture 106 of a color image and the capture 107 of a first fluorescence image (namely in fluorescence light generated by at least one of Cy5.5 and SGM-101) are performed simultaneously, but not the irradiation with the second excitation light. Only in a subsequent, non-overlapping second time interval does simultaneous irradiation 101 with broadband illumination light, irradiation 103 with second excitation light, capture 106 of a color image and capture 108 of a second fluorescence image (namely in fluorescence light produced by at least one of OTL38 and indocyanine green) take place, but not irradiation with first excitation light. In this way it is possible to distinguish between the fluorescence of Cy5.5 and/or SGM-101 and the fluorescence of OTL38 and/or indocyanine green, and in the image signal generated in subsequent step 111 and the image displayed under control thereby in subsequent step 112, the fluorescence of Cy5.5 and/or SGM-101 and the fluorescence of OTL38 and/or indocyanine green can be identified or marked or highlighted differently.

[0104] As an alternative deviating from FIG. 5, only the steps 101, 102, 106, 107 and thereafter the steps 111, 112 are conducted in order to capture an image of the object 12 in remitted or reflected illumination light and an image of the object 12 in fluorescent light generated by at least one of Cy5.5 and SGM-101, but no image of the object 12 in fluorescent light generated by OTL38 and/or OTL38. As a further alternative deviating from FIG. 5, only the steps 101, 103, 106, 108 and thereafter the steps 111, 112 are conducted in order to capture an image of the object 12 in remitted or reflected illumination light and an image of the object 12 in fluorescent light generated by at least one of OTL38 and indocyanine green, but no image of the object 12 in fluorescent light generated by Cy5.5 or SGM-101.

[0105] FIG. 6 shows a schematic flowchart of a further method of capturing an image of an object of medical interest in remitted or reflected broadband illumination light, of capturing an image of the object in fluorescent light generated by at least one of Cy5.5 and SGM-101, and of capturing an image of the object in fluorescent light generated by at least one of OTL38 and indocyanine green.

[0106] The method shown in FIG. 6 differs from the method shown in FIG. 5 in particular in that in a third time interval the object 12 is simultaneously irradiated with red light, i.e. light in the wavelength range perceived as red by the healthy human eye, and a red light image in remitted or reflected red light is captured by the second image sensor without simultaneously irradiating the object 12 with first excitation light or with second excitation light. Thereby, in one method step 109 only the red light remitted or reflected by the object 12 is detectedin the image capturing system shown in FIGS. 1 to 3: by the second image sensor 70but not fluorescence. The red light image can be used in a subsequent step 110 to correct the red color channel of the color image and thus improve color reproduction. Instead of irradiation with red light, i.e. light that only has spectral components in the wavelength range perceived as red by the healthy human eye, light can be used that covers other wavelength ranges, for example broadband illumination light as used in step 101. In this case, the object 12 can be continuously exposed to the broadband illumination light having portions in the wavelength ranges perceived by the healthy human eye as blue, green, and red.

[0107] The method shown in FIG. 6 involves capturing a first fluorescence image and capturing a second fluorescence image at two different and non-overlapping time intervals, similar to the method shown in FIG. 5. Alternatively, similar to the method shown in FIG. 4, the fluorescence of at least one of Cy5.5 and SGM-101 and the fluorescence of at least one of OTL38 and indocyanine green can be detected simultaneously.

[0108] In each of the methods described with reference to the FIGS. 4 through 6, in the steps 107, 108, the second image sensor 70 can receive and detect both remitted and reflected illumination light and fluorescent light generated by at least one of Cy5.5 and SGM-101 and/or by at least one of OTL38 and indocyanine green. If the object 12 is continuously irradiated by illumination light generated by the first light source 21, a pure fluorescence image can be obtained as a difference between an image captured by the second image sensor during irradiation with both illumination light and excitation light and an image captured by the second image sensor during illumination with illumination light only.

[0109] If the object 12 is not continuously irradiated by illumination light generated by the first light source 21, a pure fluorescence image can be captured while the object 12 is illuminated with excitation light only.

[0110] As outlined above, the intensity of the illumination light generated by the first light source 21 can-different from the spectrum shown in FIG. 2be small or can even vanish at wavelengths greater than the cutoff wavelength .sub.0. In this case, the second image sensor 70 receives little or no illumination light generated by the first light source 21 and remitted or reflected by the object, even if the first light source 21 continuously generates illumination light. Rather, most or all of the light received by the second image sensor 70 is fluorescent light, and the image captured by the second image sensor 70 is a pure or almost pure fluorescence image.

[0111] If the illumination light generated by the first light source 21 provides only a low or a vanishing intensity at wavelengths above the cutoff wavelength , the methods described above with reference to the FIGS. 4 through 6 can be particularly advantageous. In this case, in the method described with reference to FIG. 6, in particular a fourth light source is provided for the generation of light in the wavelength range above the cutoff wavelength .sub.0 in order to illuminate the object 12 in this wavelength range in the method step 104.

[0112] FIG. 7 shows a schematic flowchart of a further method of capturing an image of an object of medical interest in remitted or reflected broadband illumination light, of capturing an image of the object in fluorescent light generated by at least one of Cy5.5 and SGM-101, and of capturing an image of the object in fluorescent light generated by at least one of OTL38 and indocyanine green.

[0113] In particular, the method shown in FIG. 7 differs from the methods described with reference to the FIGS. 4 through 6 in that capturing 106 the color image, capturing 107 the first fluorescence image and capturing 108 the second fluorescence image are conducted in three different and non-overlapping time intervals.

[0114] In a first time interval, the object 12 is irradiated with illumination light, and simultaneously a color image is captured by the first image sensor 60. If the illumination light provides a relevant intensity in the wavelength range detected by the second image sensor 70, a red light image can be captured by the second image sensor 70 in an optional method step 109. In a later method step 110, this red light image can be used to correct the red color channel of the color image captured by the first image sensor 60.

[0115] In a second time interval, the object 12 is irradiated with first excitation light, and simultaneously a first fluorescence image in fluorescent light generated by at least one of Cy5.5 and SGM-101 is captured by the second image sensor 70.

[0116] In a third time interval, the object 12 is irradiated 103 with second excitation light, and simultaneously a second fluorescence image in fluorescent light generated by at least one of OTL38 and Indocyanine green is captured 108 by the second image sensor 70.

[0117] In particular, an image capturing system 10 as described with reference to the FIGS. 1 through 3 can provide several different modes of operation in which the methods described with reference to the FIGS. 4 through 7 or parts of these methods and/or further methods are conducted. In particular, each of the methods described with reference to FIGS. 5 and 6 can be modified either by omitting the method steps 101, 102, 106, 107 conducted in the first time interval or by omitting the method steps 101, 103, 106, 108 conducted in the second time interval. Furthermore, the image capturing system 10 can provide one or more modes of operation in which only a white light image is captured and/or only a white light image is displayed without any fluorescence information. Furthermore, the image capturing system 10 can provide one or more modes of operation in which only a fluorescence image is captured and/or only a fluorescence image is displayed without any white light image information.