Abstract:
An ophthalmoscope for viewing a fundus of an eye includes an optical lens, a ring light source configured to project light along an illumination path through the optical lens into the eye, a viewing optical system configured to view the fundus through the optical lens along a viewing optical path, wherein a portion of the viewing optical path and a portion of the illuminating optical path share a same optical axis. In addition, a fundus camera includes a viewing optical path, an imaging device, and an illuminating optical path including at least one LED and a pinhole mirror reflecting the at least one LED into the imaging device, wherein at least a portion of the illuminating optical path shares an optical axis with at least a portion of the viewing optical path.

Description:
[0001]     Priority is claimed to U.S. provisional Patent Application No. 60/702,038, filed on Jul. 22, 2005, the entire disclosure of which is incorporated by reference herein. 
     
    
       [0002]     The present invention relates to an ophthalmological examination instrument for photographing the fundus of the eye of humans and animals. Furthermore, front sections of the eye can be captured.  
       BACKGROUND  
       [0003]     This ophthalmological examination instrument is also called a fundus camera. The classic structure of a fundus camera consists of a viewing optical path and an illuminating optical path. In the simplest case, the viewing optical path has two lenses. The image scale is essentially determined by the factor of the two focal lengths of the lenses. On the imaging side of the optical system, the fundus of the eye can be photographed or viewed through imaging devices such as solid state cameras or through light-sensitive films or through an eyepiece. The illuminating optical path of a classical fundus camera is complex. It has the objective of allowing light beams to enter the eye to be viewed without interfering with the viewing optical path in this process. It has to be taken into account that only a fraction of the introduced light is reflected for viewing while the rest is completely absorbed. Light from a source is collimated by means of a condenser outside of the axis of the viewing optical path, it traverses several apertures (iris aperture, cornea aperture and lens apertures) until the light from the source is conducted via a pinhole mirror in the direction of the sagittal axis of the patient&#39;s eye and it is projected sharply onto the cornea through the ophthalmoscope lens. A drawback is the complicated structure of the entire optical system with its two separate optical paths. Its production is demanding and it is complicated and difficult to align.  
       SUMMARY OF THE INVENTION  
       [0004]     An object of the present invention is to provide a simple fundus camera that has a special and simple optical path. All reflections such as the cornea reflection and the ophthalmoscope lens reflection are deflected in such directions that they do not interfere with the viewing optical path.  
         [0005]     The present invention relates to an ophthalmological examination instrument for photographing the fundus of the eye of humans and animals. Furthermore, front sections of the eye can be captured. The principle for achieving this is based on the fact that the viewing optical path and the illuminating optical path are mainly on the same optical axis and that the illumination is provided through a ring light arrangement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The present invention is described in more detail below with reference to the accompanying drawings, in which:  
         [0007]      FIG. 1  shows a first exemplary embodiment of an ophthalmoscope according to the present invention;  
         [0008]      FIG. 2  shows a second exemplary embodiment of an ophthalmoscope according to the present invention;  
         [0009]      FIG. 3  shows a third exemplary embodiment of an ophthalmoscope according to the present invention;  
         [0010]      FIG. 4   a  shows a first exemplary embodiment of a ring light according to the present invention;  
         [0011]      FIG. 4   b  shows a second exemplary embodiment of a ring light;  
         [0012]      FIG. 4   c  shows a third exemplary embodiment of a ring light  
         [0013]      FIG. 4   d  shows a fourth exemplary embodiment of a ring light  
         [0014]      FIG. 4   e  shows a fifth exemplary embodiment of a ring light  
         [0015]      FIG. 5  shows fourth exemplary embodiment of an ophthalmoscope;  
         [0016]      FIG. 6  shows a fifth exemplary embodiment of an ophthalmoscope;  
         [0017]      FIG. 7  shows a sixth exemplary embodiment of an ophthalmoscope according to the present invention; and  
         [0018]      FIG. 8  shows a seventh exemplary embodiment of an ophthalmoscope according to the present invention; 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  shows a ophthalmoscope with a solid state camera. The illumination system is the ring light source  7 . The viewing optical path includes a solid state surface sensor  9  located in the imaging plane and having a viewing optical system  6  positioned in front of it. The viewing optical path and the illuminating optical path are on one optical axis, the ophthalmoscope lens  5  being shared. The light emitted by the ring light source  7  is assumed to be approximately parallel. The ring light is projected through the ophthalmoscope lens  5  onto the cornea  4  of the patient&#39;s eye  1 . The ring light projected on the cornea  4  scatters light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system  6 , which in the simplest case comprises an imaging device including an objective with a solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it. Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system  6 .  
         [0020]      FIG. 2  shows a ophthalmoscope having an eyepiece. The illumination system is the ring light source  7 . The viewing optical path includes an eyepiece  10  located in the imaging plane. The viewing optical path and the illuminating optical path are identical, the ophthalmoscope lens  5  being shared. The light emitted by the ring light source  7  is assumed to be approximately parallel. The ring light is projected through the ophthalmoscope lens  5  onto the cornea  4  of the patient&#39;s eye  1 . The ring light projected on the cornea  4  scatters light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . The intermediate image becomes visible to the observer through the viewing optical system  6  and through an eyepiece  10 . Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system  6 .  
         [0021]      FIG. 3  shows an ophthalmoscope having a variable ring light. The illumination system is the ring light source  7 . The viewing optical path includes a solid state surface sensor  9  located in the imaging plane. The viewing optical path and the illuminating optical path are identical, the ophthalmoscope lens  5  being shared. The light emitted by the ring light source  7  is assumed to be approximately parallel. The ring light is projected through the ophthalmoscope lens  5  onto the cornea  4  of the patient&#39;s eye  1 . The diameter of the ring light  7  is variably adjustable, as a result of which one can set it to the width of the iris. The diameter  13  is set in such a way that, on the one hand, no interfering reflections of the cornea detrimentally affect the image being formed and, on the other hand, the brightness or the contrast of the image being formed are optimal. The ring light projected on the cornea  4  scatters light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system, which in the simplest case comprises an objective with a solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it.  
         [0022]      FIGS. 4   a  through  4   e  show several exemplary alternative configurations of the ring light  1 .  FIG. 4   a  shows a ring light including a plurality of LEDs  30 , each having a constant wavelength and small radiation angle. For example, the LEDs may be white for color fundus images, green, 550 nm for high-contrast black-and-white fundus images (as used herein 550 nm means approximately 550 nm), blue, 490-500 nm as excitation light for fluorescence angiography (as used herein 490-500 nm means approximately 490-500 nm, or IR, 880-920 nm as excitation light for ICG angiography (as used herein 880-920 nm means approximately 880 920). The approximate values extend to values above and below the stated values that differ insubstantially in effect.  
         [0023]      FIG. 4   b  shows a ring light having LEDs  30 ,  31  having with different wavelengths. The LEDs of different wavelengths can always be arranged alternatingly, or else multi-colored LEDs are used, different examination methods being possible with one arrangement.  
         [0024]      FIG. 4  shows optical fibers  32  arranged as a ring. In order to be able to carry out several examination methods, an arrangement is proposed in which the light of a halogen lamp  33  is conducted through appropriate filters and condensers into the optical fiber bundle  34 .  
         [0025]      FIG. 4   d  shows a ring light source  35  including a taper made either of glass or of PMMA. The source can be a halogen lamp or several LEDs of different wavelengths.  
         [0026]      FIG. 4   e  shows an LED matrix  36 . Due to the matrix arrangement of the illuminating LEDs, it is possible to set different ring diameters. Moreover, elliptical illumination can be generated. Through an evaluation of the fundus image being formed, the ring light can be actuated dynamically in the x and y directions and the ring diameter can be varied.  
         [0027]      FIG. 5  shows an ophthalmoscope with a solid state camera and ring light via a pinhole mirror. The illumination system is a ring light source  7 . The viewing optical path includes a solid state surface sensor  9  located in the imaging plane. The light emitted by the ring light source  7  is assumed to be approximately parallel. The light of the ring light source is reflected in the direction of the ophthalmoscope lens of the main optical axis of the system via a pinhole mirror  14  arranged at 45°. This arrangement has the advantage that it allows greater freedom in terms of the ring light diameter. Moreover, it is conceivable that several ring lights of different diameters and wavelengths can be provided. An LED matrix having very fine structures can also fulfill a ring light function. The ring light is projected via the pinhole mirror  14  and the ophthalmoscope lens  5  onto the cornea  4  of the patient&#39;s eye  1 . The ring light projected on the cornea  4  scatters light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system  6 , which in the simplest case comprises an imaging device having an objective with a solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it. Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system, or imaging device  6 .  
         [0028]      FIG. 6  shows an ophthalmoscope with solid state camera ring light via a pinhole mirror, in a non-mydriatic arrangement. The illumination system is a split ring light source  7 . Either every other LED radiates at the same wavelength or else two light rings (as in  FIG. 4   b ) are provided. The light emitted by the ring light source  15  or  16  is assumed to be approximately parallel. The ring light source is reflected into the imaging optical system via a pinhole mirror  14  arranged at 45°. Two ring light arrangements are proposed, IR-LEDs  15  and white LEDs  16 . The non-dilated eye of the patient fundamentally reacts to visible light. Illuminating the fundus of the eye with infrared light allows a preliminary examination of the retina. Unfortunately, the images formed do not have a high contrast and are only possible in black-and-white; color images can be taken with a flash in the visible spectrum since the iris only contracts after the flash is over. This method is generally known. According to the invention, the ring light arrangement is divided, with the white LEDs  16  only functioning in flash operation and the IR-LEDs  15  serving for a preliminary examination of the fundus of the eye. The ring light is projected onto the cornea  4  of the patient&#39;s eye  1  via the pinhole mirror  14  arranged at 45° and through the ophthalmoscope lens  5 . The ring light projected on the cornea  4  scatters light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system  6 , which in the simplest case comprises an imaging device with an objective with a solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it. Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system or imaging device  6 . Two solid state cameras are provided, an IR-sensitive camera  17  serving for the preliminary examination, and a color camera  9  (e.g. re-start camera synchronous to the flash) serving to photograph the fundus of the eye. Here, the cameras can be coupled into the viewing optical path either via a partially transparent mirror  18  or via a hinged mirror  18  that briefly swings out when the snapshot is made.  
         [0029]      FIG. 7  shows an IR ophthalmoscope with an optical path angled relative to the eye and solid state camera. The illumination system is a ring light source  7 . The viewing optical path consists of an IR-sensitive solid state surface sensor  9  located in the imaging plane and having a viewing optical system or imaging device  6 . The two optical paths are identical, the ophthalmoscope lens  5  being shared. The light emitted by the IR ring light source  7  is assumed to be approximately parallel. The ring light is projected onto the cornea  4  of the patient&#39;s eye  1  through the ophthalmoscope lens  5  of the IR-blocking filter  19  which, at the same time, reflects the infrared light almost completely. The ring light projected on the cornea  4  scatters the IR light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system  6 , which in the simplest case comprises an imaging device with an objective with an IR-sensitive solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it. Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system or imaging device  6 . The eye of the patient looks through an IR-blocking filter  19  arranged at an angle of 45° with respect to the viewing axis, said IR-blocking filter  19  serving, at the same time, as an IR mirror, that is to say, the IR ophthalmoscope can be used to view the retina without disrupting the view of the patient. This technique can be used in electro-physiological examinations (e.g. ElectroRetinoGram). The patient looks at stimulating patterns, either on a monitor  20  or a light matrix  20 , the observer views the retina of the patient and can evaluate its position. Since it is known that low-contrast images are obtained when IR-illumination of the fundus of the eye is used, an on-line reworking of the camera signal is proposed and it is also possible to use false-color technology.  
         [0030]      FIG. 8  shows an IR ophthalmoscope with an optical path angled relative to the eye and solid state camera for viewing one&#39;s own retina. The illumination system is a ring light source  7 . The viewing optical path consists of an IR-sensitive solid state surface sensor  9  located in the imaging plane and having a viewing optical system or imaging device  6 . The two optical paths are identical, the ophthalmoscope lens  5  being shared. The light emitted by the IR ring light source  7  is assumed to be approximately parallel. The ring light is projected onto the cornea  4  of the patient&#39;s eye  1  through the ophthalmoscope lens  5  of the IR-blocking filter  19  which, at the same time, reflects the infrared light almost completely. The ring light projected on the cornea  4  scatters the IR light into the inside of the eye  1 . The retina  2  constitutes an illuminated object. The eye lens  3  images the retina  2  into infinity and the ophthalmoscope lens  5  focuses it in an intermediate image plane  8 . A viewing optical system  6 , which in the simplest case comprises an imaging device with an objective with an IR-sensitive solid state surface sensor  9 , is needed in order to be able to make the intermediate image visible or to capture it. Any unsharpness in the image is compensated for in the direction of the main optical axis by a fine focusing drive  11  of the viewing optical system or imaging device  6 . The observer  22  looks at a video monitor  21  through an IR-blocking filter  19  arranged at an angle of 45° with respect to the viewing axis, said IR-blocking filter  19  serving, at the same time, as an IR mirror. The signal  23  of the solid state surface sensor  9  is reproduced in the monitor  21 . The observer  22  sees his own retina. Since it is known that low-contrast images are obtained when IR-illumination of the fundus of the eye is used, an on-line reworking of the camera signal is proposed and it is also possible to use false-color technology.