Abstract:
A laryngoscope includes a handle, a spatula arranged substantially transverse to the handle, and a coupling detachably fixing the spatula to the handle. An illumination light waveguide guides an illumination light signal and an image waveguide guides an image signal, both waveguides being attached to the spatula. The illumination light waveguide includes a proximal end having an illumination light entry opening, and the image waveguide includes a proximal end having an image exit opening, wherein the illumination light entry opening and the image exit opening are arranged in the area of the coupling. The handle includes, in the area of the coupling, an illumination light exit opening and an image entry opening which allow for the illumination light signal to couple into the illumination light waveguide from the handle, and for the image signal to couple out of the image waveguide. A centering element automatically aligns the image entry opening and the image exit opening precisely to each other.

Description:
CROSSREFERENCE TO RELATED APPLICATION 
     This application is a continuation of pending international application PCT/EP00/04514 filed on May 18, 2000, and designating the U.S. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a laryngoscope comprising a handle, a spatula arranged substantially transverse to said handle, and a coupling, wherein said spatula is detachably fixed to said handle by means of said coupling. 
     The invention relates specifically to such a laryngoscope further comprising an illumination light waveguide and an image waveguide, both of which being attached to said spatula, wherein said illumination light waveguide comprises a proximal end having an illumination light entry opening, and wherein said image waveguide comprises a proximal end having an image exit opening, wherein said illumination light entry opening and said image exit opening are arranged in the area of said coupling, and wherein said handle comprises, in the area of said coupling, an illumination light exit opening and an image entry opening which allow for an illumination light signal to couple from said handle into said illumination light waveguide, and for an image signal to couple out of said image waveguide. 
     A laryngoscope of that kind is generally known from EP 0 901 772 A1. 
     The image waveguide of the known laryngoscope, which might be designated as video-laryngoscope, serves for grabbing an image in the area of the distal end of said spatula, i.e. from a throat area of a patient, and for transmitting said image to an image displaying unit. The image displaying unit might be attached to the handle, but this is not necessary. In any case, however, the grabbed image signal has to be transferred over the separable coupling. This is achieved by coupling the image signal from the image waveguide arranged on the spatula into the image entry opening of an image grabbing system that is located in the handle. 
     Coupling an image signal from one image waveguide into another always causes losses in quality. As it has turned out, these losses are the less, the more exact the corresponding openings are aligned with respect to each other. 
     The laryngoscope known from EP 0 901 772 A1 comprises a catching fastener located in the region of the coupling, and ensuring that the laryngoscope spatula is connectable to an image grabbing unit, which is located in the handle, such that the region of the throat area, which is important for the operating physician, can always be imaged. However, any reduction of losses in quality as mentioned above is not guaranteed by this configuration, since the region which is important for the physician to be observed allows positional displacements in the range of several millimeters, whereas the image transmitting quality is already impaired at relative positional displacements of the two coupling openings in the range of several micrometers. Thus, a reduction of losses in quality requires a substantially higher positional accuracy. 
     From U.S. Pat. Nos. 5,846,186 and 5,800,344, video-laryngoscopes are known wherein the image waveguide is not led across the coupling, just in contrast to the laryngoscope mentioned at the outset. That is how losses in quality are avoided, since the image waveguide can be made in one piece. These laryngoscopes, however, complicate the handling for the physician due to the cables in the proximal region of the spatula. 
     It is therefore an object of the present invention to provide a laryngoscope of the type mentioned at the outset which provides for reduced losses in quality during image transfer, and which provides a simple handling at the same time. 
     SUMMARY OF THE INVENTION 
     This object is achieved with a laryngoscope as mentioned at the outset that comprises a centering element which automatically aligns the image entry opening and the image exit opening precisely to each other. 
     By means of such a centering element, a given adjustment of the coupling openings is not only fixed, but beyond that the absolute position of the coupling openings with respect to each other is guaranteed, in contrast to a catching fastener. From the technical point of view, displacement of the positions of the coupling openings is not only prevented after putting together the spatula and the handle, but, what is more, in putting together the handle and the spatula, an optimum alignment of the coupling openings is already attained. Thereby, the light entry opening and the light exit opening are always optimally arranged with respect to each other, and losses in quality are minimum when the image signal is coupled over. 
     Moreover, the laryngoscope according to this invention provides for the same easy handling as the laryngoscope mentioned at the outset. The object is therefore completely achieved. 
     In an embodiment of the invention, the centering element mechanically aligns said image entry opening and said image exit opening with respect to each other. 
     This feature provides for a simple and robust handling, in particular when connecting the spatula to the handle. 
     In a further embodiment, the centering element aligns the image entry opening and the image exit opening both in radial and in axial direction with respect to each other. 
     This feature is particularly advantageous with respect to the fact that not only a radial displacement of the openings allocated to each other, but also an axial displacement may cause deterioration in image quality. For attaining an optimum image quality, it is therefore advantageous to center the openings allocated to each other in every direction. 
     In a further embodiment, the centering element fixes said entry and exit openings with a variation in fitting of less than 0.5 mm, preferably less than 0.1 mm. 
     These dimensions have turned out to be advantageous in practical experiments in order to guarantee a constant image quality even during a rough handling of the laryngoscope, and during force impact, in particular in emergency situations. 
     In a further embodiment, the centering element comprises at least one cone and a corresponding counter cone, one of which being disposed at said handle and the other one at said spatula. 
     Such an embodiment has turned out to be particularly advantageous for the centering element, as it is simple and robust on the one hand, and it combines the advantageous features mentioned before on the other. 
     In a further embodiment, the centering element comprises an electronic image alignment unit. 
     In particular, an electronic image alignment unit can be realized by arranging an electronic image or frame grabber, e.g. a CCD-chip, in the handle of the laryngoscope, the light-sensitive, active area of which being larger than the area really required. In such a case, the electronic image or frame grabber is capable to catch the image signal transmitted by the image waveguide even, if the adjustment of the image entry and exit openings is not exactly maintained any more. By measures known per se from electronic image processing, the “true” image sector can be extracted then. The feature has the advantage, both if taken alone or in combination with a mechanical alignment element, that the image quality of the laryngoscope according to the invention can be constantly maintained, even if loads and forces are acting. 
     In a further preferred embodiment of the invention, the image entry opening and the illumination light exit opening are located in different coupling planes that are axially displaced with respect to each other. 
     This feature has the advantage that scattering of the illumination light signal into the image waveguide is prevented in a simple manner, whereby the image quality of the inventive laryngoscope is further improved. 
     In a further preferred embodiment, the coupling is a standard coupling for connecting laryngoscope-spatulas to handles. 
     In this connection, every coupling is considered as a standard coupling which has become so widespread among laryngoscopes that a considerable number of laryngoscopes operate with this coupling. The feature has the advantage that the spatulas and handles of the laryngoscopes being already in use can alternatively be combined with the spatula and the handle of the inventive laryngoscope, although the image displaying unit might not be used in this case. In an emergency situation, however, there is the possibility to combine any spatula more suitable with respect to its size with the handle of the inventive laryngoscope due to this feature. All in all, the application variety is enlarged due to the features mentioned. 
     In a further embodiment of the feature mentioned before, the coupling complies with the requirements of International Standard ISO 7376-3. 
     This standard defines a standard coupling for connecting spatulas and handles of laryngoscopes. Accordingly, numerous laryngoscopes operate with this standard coupling, and they benefit from the combination possibilities discussed before. 
     In a further embodiment of the features mentioned before, the coupling comprises, at the proximal end of the image waveguide, a coupling area which is located outside of the coupling area defined by International Standard ISO 7376-3. 
     Alternatively, it is basically feasible to integrate the proximal end of the image waveguide in the coupling within the dimensions determined by standard ISO 7376-3. In contrast thereto, the feature has the advantage that the region defined by the standard need not be modified, which considerably facilitates compliance with this standard. In addition, due to this feature, a second coupling region is provided which improves the stability and the support of the coupling. This is particularly advantageous with respect to the accuracy in fitting which has to be observed in positioning the entry and exit openings allocated to each other. 
     In a further embodiment of the invention, the laryngoscope comprises an image displaying unit located at the handle in order to display a grabbed image. 
     This feature makes the inventive laryngoscope autonomous, i.e. it may be used independently of an external monitor or any other external devices. In that way, handling and expenditure, in particular with respect to emergency situations, is considerably facilitated. 
     In a further embodiment of the feature mentioned before, the image displaying unit is located on a side of the handle facing away from the distal end of the spatula. 
     This feature has the advantage that the operating physician can observe the image supplied by the image displaying unit virtually from behind, i.e. from the reverse side of the laryngoscope. This is particularly favorable, since the operating physician thus can quickly switch between the image supplied by the image displaying unit and a direct glance into the throat area of the patient, without having to turn his head a lot. 
     In a further embodiment, the image displaying unit is rotatable around a longitudinal axis of the handle. 
     This feature has the advantage that the operating physician can easily adjust the alignment of the image displaying unit to his needs. Moreover, a rotation of the image displaying unit about the longitudinal axis of the handle can be realized in a more robust way than a rotation about an axis that is orthogonal to the longitudinal axis of the handle. The laryngoscope of this embodiment is therefore very robust, in spite of the additional possibility of adjusting. 
     In a further embodiment, the image displaying unit can be tilted with respect to the longitudinal axis of the handle. 
     This feature also has the advantage that the operating physician can adjust the alignment of the image displaying unit to his needs while using the laryngoscope. 
     In a further embodiment, the image displaying unit can be separated from the handle. 
     This feature has the advantage that the image displaying unit can easily be exchanged in case of damage. Another advantage is that the operating physician may remove the image displaying unit from the handle, if he does not need it any longer for the treatment of a patient. In this case, the inventive laryngoscope corresponds to any common laryngoscope without an image displaying unit with respect to its dimensions and its handling. 
     In a further embodiment, at least a part of the spatula is made of a light guiding material which forms the illumination light waveguide. 
     This feature has the advantage that additional optical fibers for the illumination light waveguides might be omitted. In that way, robustness of the laryngoscope can be further improved, while production costs can be saved at the same time. In addition, a light exit for illuminating the throat area can be arranged in a simple way at the distal end of the spatula, without the need to change the function-dependent shape of the spatula. 
     In a further embodiment, the laryngoscope comprises at least two image waveguides and two image grabbing units. 
     This feature has the advantage that a stereoscopic and, thus, a spatial image can be achieved which further facilitates the orientation for the operating physician when intubating a patient. 
     In a further embodiment, a gas sensor for measuring parameters of a gas mixture is arranged at the distal end of the spatula. 
     The gas sensor preferably serves for determining the oxygen content and/or the CO 2  content. The measure is particularly advantageous when the laryngoscope is used in emergency situations for intubating an asphyxiating patient. In such a situation, the amount of oxygen can be determined in the region of the trachea entrance in a simple manner. 
     In a further embodiment of the feature mentioned before, the gas sensor is connected to an evaluation unit arranged in the handle. 
     This feature has the advantage that the relatively delicate evaluation unit is protected in the laryngoscope. Furthermore, the laryngoscope provides for the possibility to use the signals of the gas sensor without external devices. 
     It is to be understood that the features mentioned above and those to be explained below are not only applicable in the given combinations, but may also be used in different combinations or taken alone without departing from the scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in more detail below in conjunction with selected embodiments and the drawings referred to in the following: 
     FIG. 1 shows a first embodiment of a laryngoscope according to the invention in a side view; 
     FIG. 2 shows the laryngoscope of FIG. 1 in a perspective view, wherein the spatula is separated from the handle; 
     FIG. 3 shows the laryngoscope of FIG. 1 along line III—III; 
     FIG. 4 shows the coupling of the laryngoscope of FIG. 3 in a detailed view; 
     FIG. 5 shows the coupling of FIG. 4, wherein the spatula and the handle are separated from each other; 
     FIG. 6 shows a second embodiment of a laryngoscope according to the invention in a side view; 
     FIG. 7 shows a third embodiment of a laryngoscope according to the invention; 
     FIG. 8 shows an embodiment of an autonomous video-laryngoscopes; and 
     FIG. 9 shows a second embodiment of an autonomous video-laryngoscopes. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In FIGS. 1 to  3  a laryngoscope according to the invention is designated in its entirety with reference numeral  10 . 
     Laryngoscope  10  comprises a handle  12  and a spatula  14  which are connected to each other by means of a coupling  16 . The spatula-sided part of coupling  16  is designated with reference numeral  18  and the handle-sided part with reference numeral  20 . 
     In a way known per se, spatula  14  comprises a spatula blade  22 , a lateral wall  24  of which projects substantially vertically upwards. At its distal end  26 , spatula blade  22  comprises a bead  28 . On that side of lateral wall  24  that faces away from spatula blade  22 , a tube  30  is laid which accommodates both an illumination light waveguide  32  and an image waveguide  34 . In the present embodiment, illumination light waveguide  32  comprises three individual illumination light waveguide strings  32   a,    32   b,    32   c  which are radially arranged around image waveguide  34 , as can be seen in opened coupling  16  in FIG.  2 . 
     Tube  30  extends on the reverse side of lateral wall  24  to an oblong hole  36  and emerges through lateral wall  24  onto spatula blade  22 . At the distal end of tube  30 , illumination light waveguide  32  comprises a light exit opening  38 . Image waveguide  34  comprises an image entry opening  40  there. The combined arrangement of illumination light waveguide  32  and image waveguide  34  in a tube  30  is known per se in the prior art and, thus, needs not to be explained in more detail. 
     Coupling  16  of laryngoscope  10  is a bayonet-like coupling with parts  18 ,  20  to be connected being fixed by a retaining nut  42 . Further details of the coupling are described in the following with respect to FIGS. 4 and 5. 
     Handle  12  of laryngoscope  10  comprises in a manner known per se a tube-shaped shaft  44  which accommodates further components of laryngoscope  10 . In this specific embodiment, two external cable connections  46 ,  48  belong to these components, as can be seen in FIG.  3 . At the upper end in FIGS. 4 and 5 cable connection  48  comprises an image grabbing module  49  that transforms a received image signal into an electric image signal. 
     A light signal can be supplied to laryngoscope  10  via cable connection  46 , which comprises a plug contact  52  at the bottom end  50  of handle  12 . On the other hand, cable connection  48  serves for transmitting the optical image signal of an image taken at image entry opening  40  in the form of an electric image signal to an image displaying unit that is not shown herein. 
     In the cross sectional view of FIG. 3, it is further to be seen that cable connection  46  splits, in the inner part of handle  12 , into three individual strings  46   a,    46   b  and  46   c  which adjoin to the individual strings of illumination light waveguide  32  in the region of coupling  16  (cf. FIG.  2 ). 
     In the enlarged cross sectional view of FIGS. 4 and 5, only strings  32   a  and  32   b  of illumination light waveguide  32  as well as string  46   a  of cable connection  46  can be seen. Just like remaining strings  32   b,    32   c,  string  32   a  of illumination light waveguide  32  comprises a light entry opening  64  at its bottom end  62 , which is also referred to as proximal end in the following. In the handle-sided part  20  of laryngoscope  10  and opposite from light entry opening  64 , light exit opening  66  of string  46   a  of cable connection  46  is located. When spatula  14  is connected to handle  12 , as shown in FIG. 4, light entry opening  64  and light exit opening  66  are directly opposite to each other. 
     In a same way, image waveguide  34  comprises an image exit opening  68  at its proximal end  62 , which is opposite from image entry opening  70  of image grabbing module  49 . Entry and exit openings  64  to  70  are sealed by a cover glas in order to prevent dirt or dust from entering. 
     As particularly can be seen in the illustration of FIG. 5, light exit opening  66  and image entry opening  70  are arranged in two different coupling planes  72 ,  74  which are axially displaced with respect to each other along longitudinal center axis  76  of handle  12 , this prevents scattering light created in the region of light exit opening  66  to enter through image entry opening  70  into the image section. In a same way, light entry opening  64  and image exit opening  68  are arranged in different planes that are axially displaced with respect to each other. 
     Illumination light waveguide  32  and image waveguide  34  solely consist of optical fiber bundles in the present embodiment of laryngoscope  10 . In particular image waveguide  34 , however, may also comprise a lens system, alternatively hereto. 
     Beside retaining nut  42  the mechanical part of coupling  16  particularly comprises a cone  82  at proximal end  62  of spatula  14 , and a corresponding counter cone  84  at the upper end of handle  12 . Furthermore, an orientation pin  86  is provided which has to be introduced into a suitable bore  88  when spatula  14  is connected to handle  12 . Orientation pin  86  ensures that spatula  14  can be put onto handle  12  only in a way such that entry and exit openings  64  to  70  are facing each other in a precisely fitting manner. In combination with retaining nut  42 , these elements form a centering element  90  which ensures that corresponding entry and exit openings  64  to  70  are rigidly fixed to each other with an inaccuracy in fitting of less than 0.1 mm, both in radial direction (arrow  92 ) and in axial direction (arrow  94 ). 
     Image grabbing module  49  includes a magnification optic  96  that enlarges the optical image signal entering through image entry opening  70  by the factor 1:5 approximately and, subsequently, supplies the optical image signal to an electronic image or frame grabber that is not shown herein. In the present case the electronic image or frame grabber is a CCD-chip which transforms the optical image signal into an electrical image signal. However, any other electronic image grabber may be used herein. The CCD-chip further comprises means to carry out an electronic image centering in addition to mechanical centering element  90 , according to a specifically preferred embodiment of the invention. This is particularly achieved by the CCD-chip comprising a larger active area than required, thereby the relevant image portion can be extracted by means of known image processing methods, if image exit opening  68  and image entry opening  70  are not optimally positioned with respect to each other due to forces acting onto laryngoscope  10 . 
     In the following description of the further embodiments of the invention, same reference numerals designate same elements as in FIGS. 1 to  5 . 
     In FIG. 6, a second embodiment of a laryngoscope according to the invention is designated in its entirety with reference numeral  100 . 
     Laryngoscope  100  differs from laryngoscope  10  in particular with respect to coupling  16  which is here a standard coupling complying with International Standard ISO 7376-3. This type of coupling has a transverse pin  102  which is located at the handle-sided part  20  of coupling  16 . Spatula-sided part  18  comprises an U-shaped recess not recognizable in this view, by means of which spatula  14  can be put onto transverse pin  102 . Spatula  14  can be pivoted about transverse pin  102  into the direction of arrow  104 , thus facilitating assembling and disassembling of laryngoscope  100 . 
     In order to prevent an unintended pivoting movement along the direction of arrow  104  during use of laryngoscope  100 , locking elements (not to be seen in this view) are provided in the inner part of coupling  16 . 
     Standard ISO 7376-3 defines only the part of coupling  16  that is located left from line  106  in FIG.  6 . This coupling area is designated with the reference numeral  108  in the following. In this embodiment, at the right from line  106 , an additional coupling area  110  is located, and the contact region of coupling  16  is enlarged by this area with respect to standard ISO 7376-3. According to a preferred embodiment, additional coupling area  110  is here arranged diametrically opposed from the distal end  26  of spatula  14 . 
     In this embodiment, additional coupling area  110  accommodates the coupling for image waveguide  34 . As a result, handle  12  of laryngoscope  100  can also be connected to any standard spatula not including an image waveguide, since such a standard spatula reaches only until line  106 . In the same way, spatula  14  can be connected to any handle of a standard laryngoscope, the handle-sided part  20  of which not including coupling area  110 . 
     In the present embodiment, coupling area  110  comprises a flange  112  at the handle-sided part  20  which has an inner cone  114  at its upper end. Spatula-sided part  18  has a suitable outer cone  116 . Like in the previous embodiment, inner cone  114  and outer cone  116  are components of a centering element  90  that fixes the entry and exit openings  64  to  70  in their predetermined positions with respect to each other, in addition to suitable locking means not shown herein. For ease of illustration, reference numerals mentioned at last are not drawn in FIG.  6 . 
     In case the locking means provided for standard coupling  16  should not be sufficient to rigidly ensure the required accuracy in fitting, further locking means may be added, which are also arranged in coupling area  110  preferably. Preferably, a retaining nut is used similar to that shown in FIG. 1, or any another locking mechanism that can be released only by hand. 
     In the partly sectioned view of coupling area  110 , an electronic image grabber in form of a CCD-chip is to be seen. Its signals are supplied to an evaluation and control unit which is also arranged in handle  12  of laryngoscope  100 . In the handle-sided part  20 , laryngoscope  100  additionally accommodates a light source  122 , the light of which is directly coupled into illumination light waveguide  32 . 
     Beside that, laryngoscope  100  operates the same way as laryngoscope  10 . 
     In the embodiment according to FIG. 7, a laryngoscope according to the invention is designated in its entirety with reference numeral  130 . 
     Laryngoscope  130  substantially differs from laryngoscope  100  of FIG. 6 by a different kind of extension of standard coupling  16 . However, the differences are limited to additional coupling area  110 . The part of coupling  16  being left from line  106  in FIG. 7 completely complies with standard ISO 7363-3. 
     In laryngoscope  130 , the electronic image grabber is arranged in a flange  112  that extends to the upper proximal end of spatula  14  in axial direction of handle  12 . Spatula  14  is centered onto flange  112  by conic alignment pins  132  which engage in suitable conical shaped recesses at lateral wall  24  of spatula  14 . Alignment pins  132  are mounted on springs  134 , such that a spatula without recesses can push back alignment pins  132 . Therefore, it is possible to use any standard spatula in connection with laryngoscope  130 . 
     Since image waveguide  34  of laryngoscope  130  extends in a far less curved manner, it is possible here to use an image waveguide  34  that includes a lens system  136 . Besides that, the function mode of laryngoscope  130  corresponds to that of laryngoscope  100 . 
     Further embodiments of the invention are attained if features of the embodiments shown before by way of example are combined with each other. For instance, it is feasible to implement an internal light source  122  into laryngoscope  10 . On the other side, laryngoscopes  100 ,  130  may be provided with a cable connection  46  for supplying illumination light from an outside light source. Likewise, laryngoscopes  100 ,  130  may be provided with an electronic image alignment unit. 
     In further embodiments, laryngoscopes comprise an image displaying unit directly fixed to or even integrated into handle  12  of the laryngoscope rather than a cable connection  48 . In such a case, a completely autonomous video-laryngoscope is attained without external cable connections. 
     In FIG. 8, such an autonomous video-laryngoscope is designated in its entirety with reference numeral  140 . 
     For electrical power supply of image grabbing unit  118 , light source  122 , evaluation and control unit  120 , and image displaying unit  142  explained in the following, two batteries  144  are accommodated in handle  12 . Batteries  144  are electrically connected to the components mentioned above, which is indicated by arrow  146 . Batteries  144  can be charged inductively here, i.e. remotely from outside. 
     At proximal end  148  of handle  12 , an image displaying unit  142  is integrated comprising essentially a screen  150  that is visible for the operating physician. Screen  150  is made in LCD-technology in a sandwich arrangement, and colored. The whole image displaying unit  142  is rotatable around longitudinal axis  152  of handle  12 , such that the operating physician can adapt the position of screen  150  according to his needs. 
     For illustration purposes, an image of the larynx area of a patient with epiglottis  154  and vocal cords  156  taken via image waveguide  34  and image grabbing unit  118 , and reproduced via image displaying unit, is schematically shown on screen  150 . Likewise, an image  158  of bead  28  at the distal end  26  of spatula  14  is to be seen in the display here. 
     In the embodiment shown here, image displaying unit  142  is detachable from proximal end  148  of handle  12 . This is necessary in the present embodiment to change batteries  144 , and, apart from that, might be favorable when image displaying unit  142  is not required. In a normal application, however, image displaying unit  142  will be fixed to handle  12 . 
     Furthermore, the laryngoscope of this embodiment comprises a gas sensor  160  known per se which is arranged at distal end  26  of spatula  14 . Due to gas sensor  160 , it is possible to determine the oxygen content and/or the CO 2 -content in the throat area of the patient. Gas sensor  160  is connected to an evaluation unit  162  that is arranged in handle  12 . 
     In addition, laryngoscope  140  may be provided with an irrigation system not shown herein, by means of which a liquid, e.g. a NaCl-solution, may be led to distal end  26  of spatula  14  via handle  12  in order to clean the ends of illumination light waveguide  32  and image waveguide  34  during application. 
     In FIG. 9, a further embodiment of an autonomous video-laryngoscope is designated in its entirety with reference numeral  170 . 
     Laryngoscope particularly differs from the previous embodiment with respect to image displaying unit  142  which is rigidly fixed at distal end  172  of handle  12  here. In order to provide the operating physician with a good view onto screen  150 , image displaying unit  142  is arranged on the side of handle  12  that faces away from distal end  26  of spatula  14 . In an alternative embodiment not shown herein, screen  150  can be tilted with respect to longitudinal axis  152  of handle  12 . 
     A further characteristic of laryngoscope  170  is spatula  14  consisting of a transparent, light-conducting material, e.g. plexiglass in the present case. The material is selected such that spatula blade  22  of spatula  14  replaces the illumination light waveguide. Accordingly, laryngoscope  170  operates with a single optical fiber for image waveguide  34  only. As indicated by arrows  174  in FIG. 9, light is conducted to distal end  26  of spatula  14 , and it emerges there from bead  28 . 
     As a further difference with respect to the previous embodiments, laryngoscope  170  here includes three different-colored light sources in form of three LEDs which are designated by reference numerals  176 ,  178 ,  180 , and which cover the colors red, green, and blue. 
     Furthermore, at its handle  12  laryngoscope  170  comprises a jack  182  with electric connections for additional electric supply from outside, and for tapping signals supplied from image grabber  118  to image displaying unit  142 . Thus, it is possible to telemetrically display the image from image grabber  118  on an external monitor. This might be carried out both in addition and alternatively to displaying the image on screen  150  of image displaying unit  142 . In addition, jack  182  includes contacts for an external light source and, if applicable, for a telemetric evaluation of signals of a gas sensor  160 . 
     In a special mode of operation of laryngoscope  170 , light sources  176  to  180  are pulsed synchronically with an image frequency of image grabber  118 , or image displaying unit  142 , respectively, in order to reduce average power consumption.