Abstract:
A fundus camera comprising TV relay lens unit ( 27 ) and a body unit ( 1 ) which is capable of mounting plurality of TV cameras ( 30, 31 ) and ( 32 ) is provided. The body unit ( 1 ) includes photographing optical system ( 3 ) for photographing a fundus Fu to be observed. The TV relay lens unit ( 27 ) is detachably mountable on the body unit ( 1 ) and has a function to direct a fundus image forming luminous flux divided by the photographing optical system ( 3 ) to respective TV camera according to light. The TV relay lens unit ( 27 ) comprises a switching mirror ( 37 ) and a reflecting optical element ( 38 ) so as to adapt to TV cameras of a visible-fluorescent photographing/infrared-fluorescent photographing TV camera ( 30 ) which has sensitivity for both visible light and infrared light, a color photographing TV camera ( 31 ), which has sensitivity for visible light and a fundus observing TV camera ( 32 ) which has sensitivity for infrared light. The switching mirror ( 37 ) and the reflecting optical element ( 38 ) selectively switches the optical path of fundus image forming luminous flux so as to direct it to respective TV camera according to light by instantaneous insertion or retraction operation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of PCT Application No. PCT/JP00/02767, filed Apr. 27, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to an improvement of fundus camera which photographs an image of fundus and more particularly relates to an improvement of fundus camera through which colored fundus images, visible-fluorescent fundus images and infrared-fluorescent fundus images are photographed by Television (hereinafter referred to as “TV”) camera. 
     2. Description of the Related Art 
     In fundus photographing, because infrared-fluorescent image cannot be photographed by conventional 35 mm film camera or instant camera, TV camera which converts infrared-fluorescent light into TV signal has been generally used for this purpose. Also a 35 mm film camera has been usually employed for photographing colored fundus images and visible-fluorescent images due to its higher resolution. Recently, instead of 35 mm film camera, TV camera is getting popular for photographing visible-fluorescent images and colored images as resolution of CCD for TV camera has been improved. 
     Meanwhile, with regard to infrared-fluorescent photographing, visible-fluorescent photographing and colored photographing, plurality of TV cameras must be selectively exchanged in accordance with a selection a photographing made, as the wavelength, amount of light or necessary resolution differs according to a selected photographing. Further, because several types of specific designed relay lens units are individually required to adapt respective TV cameras to the fundus camera body, each relay lens unit for respective TV cameras must be exchanged at the same time. To exchange TV camera and its relay lens unit according to the light of photograph is troublesome but inevitable work. 
     For this problem, the Japanese Patent Application Laid Open Hei 8-256988 proposed a fundus camera in which an optical path length adjusting member is arranged within a TV relay lens unit in order to adjust change of light path length depending on the type of photographing. By this arrangement, the relay lens unit need not be exchanged. However, as TV cameras themselves must be exchanged, it is still inconvenient for users. 
     The present invention is proposed to solve the above problem and an object of the present invention is to provide a fundus camera having improved operationality which makes it unnecessary to exchange TV camera for fundus photographing. 
     SUMMARY OF THE INVENTION 
     In accordance with the first aspect of present invention, a fundus camera comprising a body unit having photographing optical system to photograph a fundus to be observed, and TV relay lens unit which is detachably mounted on said body unit and having a function to direct a fundus image forming luminous flux from said photographing optical system to plurality of TV cameras, wherein said TV relay lens unit is arranged to be mountable simultaneously a visible-fluorescent photographing/infrared-fluorescent photographing TV camera having sensitivity for both of visible light and infrared light, a fundus observing TV camera having sensitivity for infrared light to observe a fundus when infrared-fluorescent photographing mode is selected, and a color photographing TV camera having sensitivity for visible light, wherein said TV relay lens unit is equipped with a switching mirror which is retractably and insertably arranged in an optical path of said fundus image forming luminous flux for switching said color photographing TV camera and said visible-fluorescent photographing/infrared-fluorescent photographing TV camera in accordance with the photographing mode, and a reflecting optical element which is arranged between said switching mirror and said color photographing TV camera to direct said fundus image forming luminous flux to said fundus observing TV camera, and said switching mirror is retracted from the optical path of said fundus image forming luminous flux to direct said flux to said fundus observing TV camera for observing a fundus in said infrared-fluorescent photographing mode, and said switching mirror is instantaneously inserted into said optical path to direct said fundus image forming luminous flux to said visible-fluorescent photographing/infrared-fluorescent photographing TV camera for photographing the fundus in said infrared-fluorescent photographing mode, is provided. 
     According to the second aspect of the invention, a fundus camera of the above described first aspect further characterized in that said reflecting optical element is a dichroic mirror which is selectively passing visible light and reflecting infrared light, is provided. 
     According to the third aspect of the invention, a fundus camera of the above described first aspect further characterized in that said reflecting optical element is a half mirror, is provided. 
     According to the fourth aspect of the invention, a fundus camera of the above described first aspect further characterized in that said reflecting optical element is a switching mirror which is insertably or retractably arranged in said optical path to direct said fundus image forming luminous flux to said fundus observing TV camera when it is inserted in said optical path, is provided. 
     According to the fifth aspect of the invention, a fundus camera comprising a body unit having photographing optical system to photograph a fundus to be observed, and TV relay lens unit which is detachably mounted on said body unit and having a function to direct a fundus image forming luminous flux from said photographing optical system to plurality of TV cameras, wherein said TV relay lens unit is arranged to be mountable simultaneously a visible-fluorescent photographing/infrared-fluorescent photographing TV camera having sensitivity for both of visible light and infrared light, a fundus observing TV camera having sensitivity for infrared light to observe a fundus when infrared-fluorescent photographing mode is selected, and a color photographing TV camera having sensitivity for visible light, and wherein said TV relay lens unit is equipped with first switching mirror which is retracted from the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said the observing TV camera when infrared-fluorescent photographing mode is selected and the observation thereof is conducted and is instantaneously inserted into the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said visible-fluorescent photographing/infrared-fluorescent photographing TV camera for infrared-fluorescent photographing mode when photographing the fundus, and second switching mirror which is inserted into the optical path of said fundus image forming luminous flux when color photographing mode is selected, and is retracted from the optical path of said fundus image forming luminous flux when visible-fluorescent photographing mode is selected, is provided. 
     According to the sixth aspect of the invention, a fundus camera comprising a body unit having photographing optical system to photograph a fundus to be observed, and TV relay lens unit which is detachably mounted on said body unit and having a function to direct a fundus image forming luminous flux from said photographing optical system to plurality of TV cameras, wherein said TV relay lens unit is arranged to be mountable simultaneously a visible-fluorescent photographing/infrared-fluorescent photographing TV camera having sensitivity for both of visible light and infrared light, a fundus observing TV camera having sensitivity for infrared light to observe a fundus when infrared-fluorescent photographing mode is selected and a color photographing TV camera having sensitivity for visible light, and wherein said TV relay lens unit is equipped with first switching mirror which is inserted into the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said the observing TV camera when infrared-fluorescent photographing mode is selected and the observation thereof is conducted, and is instantaneously retracted from the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said visible-fluorescent photographing/infrared-fluorescent photographing TV camera for infrared-fluorescent photographing mode when photographing the fundus, and second switching mirror which is inserted into the optical path of said fundus image forming luminous flux when color photographing mode is selected and is retracted from the optical path of said fundus image forming luminous flux when visible-fluorescent photographing mode is selected, is provided. 
     According to the seventh aspect of the invention, a fundus camera comprising a body unit having photographing optical system to photograph a fundus to be observed, and TV relay lens unit which is detachably mounted on said body unit and having a function to direct a fundus image forming luminous flux from said photographing optical system to plurality of TV cameras, wherein said TV relay lens unit is arranged to be mountable simultaneously a visible-fluorescent photographing/infrared-fluorescent photographing TV camera having sensitivity for both of visible light and infrared light, a fundus observing TV camera having sensitivity for infrared light to observe a fundus when infrared-fluorescent photographing mode is selected and a color photographing TV camera having sensitivity for visible light, and wherein said TV relay lens unit is equipped with first switching mirror which is inserted into the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said the observing TV camera when infrared-fluorescent photographing mode is selected and observation thereof is conducted, and is instantaneously retracted from the optical path of said fundus image forming luminous flux to direct said fundus image forming luminous flux to said visible-fluorescent photographing/infrared-fluorescent photographing TV camera for infrared-fluorescent photographing mode when photographing the fundus, and second switching mirror which is retracted from the optical path of said fundus image forming luminous flux when color photographing mode is selected and is inserted into the optical path of said fundus image forming luminous flux when visible-fluorescent photographing mode is selected, is provided. 
     In a fundus camera according to the present invention, as the switching mirror is retracted from the optical path of said fundus image forming luminous flux when color photographing mode is performed by the color photographing TV camera, the visible light component of fundus image forming luminous flux is directed to the reflecting optical element and passed through it to the color photographing TV camera. 
     And when visible-fluorescent photographing mode is performed by visible-fluorescent photographing/infrared-fluorescent photographing TV camera, as the switching mirror is inserted into the optical path of fundus image forming luminous flux, the visible-fluorescent component of fundus image forming luminous flux is reflected by the switching mirror and directed to the visible-fluorescent photographing/infrared-fluorescent photographing TV camera. 
     Further, when infrared-fluorescent photographing mode is performed by the visible-fluorescent photographing/infrared-fluorescent photographing TV camera, as the switching mirror is retracted from the optical path of fundus image forming luminous flux when observing a fundus, the infrared-fluorescent component of fundus image forming luminous flux is directed to the reflecting optical element and reflected by it to the fundus observing TV camera, and when photographing the fundus as the switching mirror is instantaneously inserted into the optical path of fundus image forming luminous flux, the infrared-fluorescent component of fundus image forming luminous flux is reflected by the switching mirror and directed to the visible-fluorescent photographing/infrared-fluorescent photographing TV camera. 
     As described above, because the switching mirror moves according to respective photographing mode and directs the fundus image forming luminous flux to respective TV cameras which are used when each photographing mode is selected, the fundus camera provided in accordance with the present invention has higher operationality which makes it unnecessary to detach one and to mount another for exchange of TV camera for fundus photographing according to light. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description of the invention presented below, reference made to the accompanying drawing, in which: 
     FIG. 1 is a side view with cross-section in part of an Embodiment and its Modifications No. 1 and No. 1′ of fundus cameras in accordance with the present invention showing elementary disposition; 
     FIG. 2 is a side view with cross-section in part of a Modification No. 2 of fundus camera in accordance with the present invention showing elementary disposition; 
     FIG. 3 is a side view with cross-section in part of a Modification No. 3 of fundus camera in accordance with the present invention showing elementary disposition; 
     FIG. 4 is a side view with cross-section in part of a Modification No. 4 of fundus camera in accordance with the present invention showing elementary disposition; 
     FIG. 5 is a side view with cross-section in part of a Modification No. 5 of fundus camera in accordance with the present invention showing elementary disposition; 
     FIG. 6 is a side view with cross-section in part of a Modification No. 6 of fundus camera in accordance with the present invention showing elementary disposition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiment of the fundus camera in accordance with the present invention is hereinafter described in detail with reference to the accompanying drawings. 
     In FIG. 1, a body of fundus camera is shown with reference number  1 . The fundus camera body  1  is mainly constituted by an illuminating optical system  2  for illuminating a fundus Fu to be observed and photographing optical system  3  which photographs the fundus Fu. 
     As shown in FIG. 1, the illuminating optical system  2  comprises concave reflecting mirror  4 , a halogen lamp  5  for illuminating the fundus of eye E when it is observed, relay lens  6 , a xenon tube  7  for illuminating the fundus when it is photographed, a condenser lens  8 , a reflecting mirror  9 , a ring-slit  10 , a relay lens  11 , a perforated mirror  13  and an objective lens  12 , and they are arranged in this order. Further, in the light path of the illuminating system  2 , an exciter filter  14  for visible-fluorescent photographing and an exciter filter  15  for infrared-fluorescent photographing are insertably and retractably arranged between a condenser lens  8  and a reflecting mirror  9 . Herein, the perforated mirror  13  and the objective lens  12  are shared by a photographing optical system which will be described later. 
     Illuminating light from the halogen lamp  5  is directed through the relay lens  6 , the condenser lens  8 , the reflecting mirror  9 , the ring-slit  10  and the relay lens  11  to the perforated mirror  13 . After reflected by the perforated mirror  13 , the light goes through the objective lens  12  and arrives at a fundus Fu of the eye E to be observed. The exciter filter  14  for visible-fluorescent photographing is inserted into this illuminating light path when photographing utilizing visible-fluorescent light is conducted (hereinafter referred to as “visible-fluorescent photographing mode”) and the exciter filter  15  for infrared-fluorescent photographing is inserted when photographing utilizing infrared-fluorescent light is conducted (hereinafter referred to as “infrared-fluorescent photographing mode”). Both exciter filters  14  and  15  are retracted from the light path when photographing utilizing usual visible light is conducted (hereinafter referred to as “color photographing mode”). 
     The photographing optical system  3  comprises the objective lens  12 , the perforated mirror  13 , a focusing lens  16 , an image-forming lens  17  and a quick return mirror  19 , and they are arranged in this order. Further in the photographing optical path of this optical system  3 , optical path length adjusting filters  20  and  21 , a barrier filter  22  for visible-fluorescent photographing mode and a barrier filter  23  for infrared-fluorescent photographing mode are insertably and retractably arranged between the perforated mirror  13  and the focusing lens  16 . In addition, a variable power lens  18  is insertably and retractably arranged between the image-forming lens  17  and the quick return mirror  19 . The perforated mirror  13  and the objective lens  12  are shared by the illuminating optical system  2  as explained above. 
     A luminous flux from the fundus Fu (hereinafter referred to as “fundus image forming luminous flux”) is directed through the objective lens  12  and a hole  13   a  of perforated mirror  13 , to focusing lens  16  and image-forming lens  17 . Optical path length adjusting filter  20  and  21  are inserted into and/or retracted from the photographing optical path to correct an optical path length caused by a difference of wavelength between respective photographing modes. The visible-fluorescent barrier filter  22  is inserted into the optical path to use when visible-fluorescent photographing mode is selected, and the infrared-fluorescent barrier filter  23  is inserted to use when infrared-fluorescent photographing mode is selected. Both of them are retracted when color photographing mode is performed. The variable power lens  18  is inserted into the optical path of the photographing optical system  3  when a magnified image of the fundus Fu is observed or photographed. 
     In the fundus camera body  1 , an eyepiece  24  and a 35 mm film camera  25  are arranged and especially the latter is detachable. The 35 mm film camera  26  is arranged on an extending line of the photographing optical path, and at the opposite side from the image-forming lens  17  with respect to the quick return mirror  19 , and is arranged so that the luminous flux from the fundus Fu is directed thereto, when the quick return mirror  19  is retracted from the photographing optical path as shown in FIG. 1 by double dotted broken line. Therefore, the quick return mirror  19  is instantaneously retracted from the photographing optical path when the 35 mm film camera  25  is used but it is usually remained in the optical path other than the 35 mm camera is used. 
     A quick return mirror  26  is inserted into the optical path when the quick return mirror  19  is inserted into the optical path. The eyepiece  24  is arranged in a reflection optical path of the quick return mirror  26 . Therefore, the quick return mirror  26  is inserted in the reflecting optical path of the quick return mirror  19  when the eyepiece  24  is used to observe the fundus Fu, but it remains out of the optical path as shown in FIG. 1 by double dotted broken line when the eyepiece  24  is not used to observe the fundus Fu, or, TV camera  32  is used to observe the fundus Fu. The eyepiece  24  is used when color photographing mode is selected and when the visible-fluorescent photographing mode is selected. 
     A unit mounting portion  28  is arranged with a field lens  29  at upper portion of the fundus camera body  1 . A TV relay lens unit  27  is detachably mounted on the fundus camera body  1  through the unit mounting portion  28 . A fundus image forming luminous flux which is reflected by the quick return mirror  19  is temporarily focused near by the field lens  29  and then directed into the TV relay lens unit  27  when the quick return mirror  26  is retracted from the optical path. 
     In the TV relay lens unit  27 , a still image recording TV camera  30  for still image recording of the visible-fluorescent fundus image and the infrared-fluorescent fundus image (hereinafter referred to as “visible-fluorescent photographing/infrared-fluorescent photographing TV camera”), a color photographing TV camera  31  for still image recording of the visible light fundus image and an observing TV camera  32  to observe infrared-fluorescent fundus image (hereinafter referred to as “fundus observing TV camera”) are arranged. And each TV camera has respective TV relay lens  33 ,  34  and  35 . The fundus image forming luminous flux is divided by a dichroic mirror  38  as a reflecting optical element (described later in detail) and directed to the observing TV camera  32 . As the divided fundus image forming luminous flux lessens its quantity of luminous flux, sensitivity of observing TV camera  32  is greater than that of the still image recording TV camera  30 . 
     On the optical path of the fundus image forming luminous flux (hereinafter referred to as “optical path O 2 ”) within the TV relay lens unit  27 , a switching mirror  37  having a function as quick return mirror, the dichroic mirror  38  and a reflecting mirror  39  are arranged in this order from the field lens  29 . The dichroic mirror  38  is an optical element for selectively reflecting infrared light and passing visible light and the reflecting mirror  39  is for reflecting all kind of lights as described in detail later. The switching mirror  37  is arranged in order to direct the fundus image forming luminous flux to the still image recording TV camera  30  when it is inserted into the optical path O 2  as shown in FIG. 1 by double dotted broken line. The dichroic mirror  38  divides the fundus image forming luminous flux into visible light and infrared light. That is, it passes selectively the visible light component, directing it to the reflecting mirror  39 , and reflects selectively the infrared light component, directing it to the observing TV camera  32 . 
     The switching mirror  37  is retracted from the optical path O 2  when color photographing mode by color photographing TV camera  31  is selected. When observing a fundus Fu, the quick return mirror  19  and  26  are inserted into the optical path O 2 . Thus, a fundus image forming luminous flux from Fundus Fu is directed to the eyepiece  24 , the fundus Fu can be observed at the eyepiece  24 . For photographing the fundus Fu, the quick return mirror  26  is instantaneously retracted from the reflecting optical path when a shutter releasing button (not shown) is operated. As the switching mirror  37  is also already retracted, the fundus image forming luminous flux is directed to the dichroic mirror  38 . The visible light component of fundus image forming luminous flux passes through the dichroic mirror  38  and is reflected by the reflecting mirror  39  and directed into the color photographing TV camera  31 . An optical path length adjusting filter  42  is arranged on the light path before the TV relay lens  34  of color photographing TV camera  31 . The optical path length adjusting filter  42  has a function to correct a difference of optical path according to respective photographing mode. Just as the optical path length adjusting filter  20  and  21 , the filter  42  is inserted automatically into the optical path when color photographing mode is selected. In this way photographing of the visible light fundus image by the color photographing TV camera  31  is accomplished. 
     The switching mirror  37  is inserted into the optical path O 2  when visible-fluorescent photographing mode, in which the still image recording TV camera  30  is used and the exciter filter  14  and barrier filter  22  are inserted into the optical path, is performed. When observing the fundus Fu, the quick return mirror  19  and  26  are inserted into the optical path O 2 . In this way, a fundus image forming luminous flux from Fundus Fu is directed to the eyepiece  24  and can be observed at the eyepiece  24 . For photographing the fundus Fu, the quick return mirror  26  is instantaneously retracted from the reflecting optical path when the shutter releasing button (not shown) is operated. As the switching mirror  37  is also inserted in advance, the fundus image forming luminous flux is reflected and directed to the still image recording TV camera  30 . Optical path length adjusting filter  40  and  41  are arranged on the light path before the TV relay lens  33  of color photographing TV camera  30 . The respective optical path length adjusting filter  40  and  41  have the function to correct the difference of optical path length caused by the difference of wavelength of utilized light according to respective photographing mode just as the optical path length adjusting filter  20  and  21 , the optical path length adjusting filter  40  is inserted automatically into the optical path when visible-fluorescent photographing mode is selected. In this way, photographing of the visible-fluorescent fundus image by the still image recording TV camera  30  is accomplished. 
     The switching mirror  37  is retracted from the optical path O 2  when infrared-fluorescent photographing mode, in which the still image recording TV camera  30  is used and the exciter filter  15  and barrier filter  23  are inserted into the optical path, is performed. When observing the fundus Fu, the quick return mirror  19  is inserted into the optical path O 2  while the quick return mirror  26  and the switching mirror  37  are retracted from the optical path. Thus, a fundus image forming luminous flux from Fundus Fu is reflected by the quick return mirror  19  and directed to the dichroic mirror  38 . The infrared component of fundus image forming luminous flux is reflected by the dichroic mirror  38  and directed into the observing TV camera  31 , then, the fundus Fu can be observed at the observing TV camera  31 . For photographing the fundus Fu, the switching mirror  37  which has also the function of quick return mirror is instantaneously inserted into the optical path O 2  when the shutter releasing button (not shown) is operated. Thus, the fundus image forming luminous flux is reflected and directed to the still image recording TV camera  30 . Optical path length adjusting filters  40  and  41  are arranged on the light path before the TV relay lens  33  of color photographing TV camera  30 . The optical path length adjusting filter  41  is inserted automatically into the optical path when infrared-fluorescent photographing mode is selected. In this way, photographing of the infrared-fluorescent fundus image by the still image recording TV camera  30  is accomplished. 
     Modification 1 
     In the above described embodiment of the present invention, the dichroic mirror  38  is employed as the reflecting optical element between the switching mirror  37  and the reflecting mirror  39 , however, a half mirror can be applicable instead of the dichroic mirror  38 . 
     In this case, when color photographing mode is selected, the switching mirror  37  is retracted from the optical path O 2  and the fundus image forming luminous flux is directed to the color photographing TV camera  31 . 
     When visible-fluorescent photographing mode is selected, the switching mirror  37  is inserted into the optical path O 2  and the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirror  37  is retracted from the optical path O 2  and the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared-fluorescent photographing mode, the switching mirror  37  as the quick return mirror is instantaneously inserted into the optical path O 2  in response to the operation of the shutter releasing button (not shown), and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     Modification 1′ 
     In the above described embodiment, the dichroic mirror  38  is arranged as the reflecting optical element between the switching mirror  37  and reflecting mirror  39 . Instead of the dichroic mirror  38 , another switching mirror can be utilized as a reflecting optical element  38  in the optical path O 2 . 
     In this case, when color photographing mode is selected, the switching mirror  37  and the switching mirror  38  are retracted from the optical path O 2  and the fundus image forming luminous flux is directed to the color photographing TV camera  31 . 
     When visible-fluorescent photographing mode is selected, the switching mirror  37  is inserted into the optical path O 2  and the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirror  37  is retracted from the optical path O 2  while the switching mirror  38  is inserted into the optical path O 2  and the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared-fluorescent photographing mode, the switching mirror  37  which has also the function of quick return mirror is instantaneously inserted into the optical path O 2  in response to the operation of the shutter releasing button (not shown), and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     The eyepiece  24  can be omitted by means of changing the observing TV camera  32  into a TV camera which has sensitivity for both of visible light and infrared light and giving the switching mirror  38  the function of quick return mirror. 
     Modification 2 
     In the above described embodiment of the present invention, the dichroic mirror  38  is employed as the optical element in order to reflect infrared light component and to transmit the visible light component, and the observing TV camera  32  is arranged on the direction of reflection, while the color photographing TV camera  31  is arranged on the direction of transmittance. However, the dichroic mirror  38  can be selected from another optical element that has a function of reflecting visible light component and transmitting infrared light component. 
     In this case, within the TV relay lens unit  27 , a switching mirror  37 , dichroic mirror  38 ′, and the reflecting mirror  39  are arranged in this order from the field lens  29  as shown in FIG.  2 . The still image recording TV camera  30 , the color photographing TV camera  31  and the observing TV camera  32  are attached to the body of TV relay lens unit  27  in this order from bottom to top. In the fundus camera in accordance with this Modification 2 the switching mirror  37  is retracted from the optical path and the visible light component of the fundus image forming luminous flux is directed to the color photographing TV camera  31  when color photographing mode is selected. 
     When visible-fluorescent photographing mode is selected, the switching mirror  37  is inserted into the optical path O 2  and the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirror  37  is retracted from the optical path O 2  and the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared fluorescent mode, the switching mirror  37  as the quick return mirror is instantaneously inserted into the optical path O 2  in response to the operation of the shutter releasing button (not shown) and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     Modification 3 
     In the above described embodiments, the dichroic mirror  38  as the reflecting optical element is arranged between the switching mirror  37  and the reflecting mirror  39 . However, another arrangement can be employed as described below. 
     In this case within the TV relay lens unit  27 , switching mirror  38 S, the switching mirror  37  and the reflecting mirror  39  are arranged in this order from bottom to top as shown in FIG.  3 . The color photographing TV camera  31 , the still image recording TV camera  30  and the observing TV camera  32  are attached to the body of TV relay lens unit  27  in this order from bottom to top. 
     In the fundus camera in accordance with this Modification 3 the switching mirror  38 S is inserted into the optical path O 2  and the fundus image forming luminous flux is directed to the color photographing TV camera  31  when color photographing mode is selected. 
     When visible-fluorescent photographing mode is selected, the switching mirror  37  is inserted into the optical path O 2  and at the same time the switching mirror  38 S is retracted from the optical path O 2 , then the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirrors  37  and  38 S are retracted from the optical path O 2  and the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared fluorescent photographing mode, the switching mirror  37  as the quick return mirror is instantaneously inserted into the optical path O 2  in response to the operation of the shutter releasing button (not shown), and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     Modification 4 
     The arrangement of still image recording TV camera  30  and observing TV camera  32  can be exchanged in the above described Modification 3. 
     In this case within the TV relay lens unit  27 , the switching mirrors  38 S and  37 , and the reflecting mirror  39  are arranged in the optical path O 2  in this order from bottom to top as shown in FIG.  4 . The color photographing TV camera  31 , the observing TV camera  32  and the still image recording TV camera  30  are attached to the body of TV relay lens unit  27  in this order from bottom to top. 
     In the fundus camera in accordance with this Modification 4 the switching mirror  38 S is inserted into the optical path O 2  and the fundus image forming luminous flux is directed to the color photographing TV camera  31  when color photographing mode is selected. 
     When visible-fluorescent photographing mode is selected, the switching mirrors  37  and  38 S are retracted from the optical path O 2  and then the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirror  37  is inserted into the optical path O 2  and at the same time the switching mirror  38 S is retracted from the optical path O 2 , then the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under infrared fluorescent photographing mode, the switching mirror  37  as the quick return mirror is instantaneously retracted from the optical path O 2  in response to the operation of the shutter releasing button (not shown), and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     Modification 5 
     Another disposition described below can be employed for the fundus camera in accordance with the present invention. 
     In this case within the TV relay lens unit  27 , the switching mirror  37 , the switching mirror  38 S, the reflecting mirror  39  are arranged in this order from bottom to top as shown in FIG.  5 . The observing TV camera  32 , the color photographing TV camera  31  and the still image recording TV camera  30  are attached to the body of TV relay lens unit  27  in this order from bottom to top. In the fundus camera in accordance with this Modification 5 the switching mirror  37  is retracted from the optical path and the switching mirror  38 S is inserted into the optical path O 2 , then the fundus image forming luminous flux is directed to the color photographing TV camera  31  in color photographing mode. 
     When visible-fluorescent photographing mode is selected, the switching mirrors  37  and  38 S are retracted from the optical path O 2  and the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed, the switching mirrors  37  is inserted into the optical path O 2  and the switching mirror  38 S is retracted from the optical path O 2 , then the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared fluorescent mode, the switching mirror  37  as the quick return mirror is instantaneously retracted from the optical path O 2  in response to the operation of the shutter releasing button (not shown) and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     Modification 6 
     Other disposition described below can be employed further. 
     In this case within the TV relay lens unit  27 , the switching mirrors  37  and  38 S, and the reflecting mirror  39  are arranged in this order from bottom to top as shown in FIG.  6 . The observing TV camera  32 , the still image recording TV camera  30  and the color photographing TV camera  31  are attached to the body of TV relay lens unit  27  in this order from bottom to top. 
     In the fundus camera in accordance with this Modification 6 the switching mirrors  37  and  38 S are retracted from the optical path O 2  and the fundus image forming luminous flux is directed to the color photographing TV camera  31  when color photographing mode is selected. 
     When visible-fluorescent photographing mode is selected, the switching mirror  37  is retracted from the optical path O 2  and the switching mirror  38 S is inserted into the optical path O 2 , then the fundus image forming luminous flux is directed to the still image recording TV camera  30 . 
     When infrared-fluorescent photographing mode is selected and the fundus Fu is observed the switching mirrors  37  and  38 S are inserted into the optical path O 2  and the infrared-fluorescent fundus image is directed to the observing TV camera  32 . When photographing the fundus Fu under the infrared fluorescent mode, the switching mirror  37  as the quick return mirror is instantaneously retracted from the optical path O 2  in response to the operation of the shutter releasing button (not shown), and the infrared-fluorescent fundus image is directed to the still image recording TV camera  30 . 
     The respective movement of switching mirrors  37  and  38 S for above described embodiment and Modifications 1 to 6 is summed up in the following Table 1. 
     Table 1 
     In the fundus camera in accordance with the present invention it is not necessary to exchange respective TV cameras according to the photographing mode selected and the operationality has been much improved by means of above described arrangement and disposition. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Position of Switching Mirror 37 and Optical Element 38 at Optical path O2 
               
             
          
           
               
                   
                   
                   
                 visible/ 
                   
                 infrared fluorescence 
                   
                 infrared fluorescence 
                   
                   
               
               
                   
                 color 
                   
                 fluorescence 
                   
                 (observation) 
                   
                 (photograph) 
               
               
                 Mode 
                 37 
                 38 
                 37 
                 38 
                 37 
                 38 
                 37 
                 38 
                 FIG. 
               
               
                   
               
               
                 Embodiment 
                 retracted 
                   
                 inserted 
                   
                 retracted 
                   
                 instantaneously inserted 
                   
                 1 
               
               
                 Modification 1 
                 retracted 
                   
                 inserted 
                   
                 retracted 
                   
                 instantaneously inserted 
                   
                 1 
               
               
                 Modification 1′ 
                 retracted 
                 retracted 
                 inserted 
                 any 
                 retracted 
                 inserted 
                 instantaneously inserted 
                 any 
                 1 
               
               
                 Modification 2 
                 retracted 
                   
                 inserted 
                   
                 retracted 
                   
                 instantaneously inserted 
                   
                 2 
               
               
                 Modification 3 
                 any 
                 inserted 
                 inserted 
                 retracted 
                 retracted 
                 retracted 
                 instantaneously inserted 
                 retracted 
                 3 
               
               
                 Modification 4 
                 any 
                 inserted 
                 retracted 
                 retracted 
                 inserted 
                 retracted 
                 instantaneously retracted 
                 retracted 
                 4 
               
               
                 Modification 5 
                 retracted 
                 inserted 
                 retracted 
                 retracted 
                 inserted 
                 any 
                 instantaneously retracted 
                 retracted 
                 5 
               
               
                 Modification 6 
                 retracted 
                 retracted 
                 retracted 
                 inserted 
                 inserted 
                 any 
                 instantaneously retracted 
                 inserted 
                 6