Patent Publication Number: US-2020278486-A1

Title: Illumination system

Description:
FIELD OF THE INVENTION 
     The present invention relates to an ophthalmic illumination system. More particularly, the present invention relates to a stand-alone, wide angle, diffuse ophthalmic illumination system for illuminating the interior of the eye during examinations, treatments and surgeries. 
     BACKGROUND OF THE INVENTION 
     There is an increasing need in accordance with a preferred embodiment of the present invention, and specifically in ophthalmic applications for compact, efficient, modular and broad band high brightness illumination systems. While various illumination systems and methods have been proposed in the past, they all use a lamp as a light. Relevant prior-art references using filament based or short arc lamps such as halogen, metal halide, high pressure mercury and xenon are disclosed below: 
     U.S. Pat. No. 3,954,329 describes apparatus for viewing an eye fundus through a contact lens. The apparatus has a lamp element that illuminates the fundus through the sclera. 
     U.S. Pat. No. 4,023,189 discloses a wide angle instrument for illuminating, observing and photographing the fundus of the eye. The instrument utilizes an arc-lamp and has a focus tube containing spaced decollimating and objective lenses with an adjustable aperture diaphragm positioned therebetween. 
     U.S. Pat. No. 5,822,036 describes an eye imaging system having a portable image capture unit having a circular light guide positioned adjacent to and behind a corneal contact lens for controlling directing lamp light over a wide field to the retina of an eye and provide more light towards the center of the eye. 
     US20070030448 is directed to an optical device for the observation and documentation of the ocular fundus and is preferably provided for fundus cameras. In order to generate a uniform illumination of the fundus by trans illumination of the sclera in the illumination unit, for fundus cameras and/or ophthalmoscopes, the light emitted by the illumination source, such as a lamp, is coupled into individual light-conducting fibers or bundles of light-conducting fibers which extend into the area of the front lens of the fundus camera and ophthalmoscope and whose fiber ends are formed in such a way that the exiting light is projected on and trans illuminates the sclera. 
     U.S. Pat. No. 6,309,070 of Eduardo Svetliza, the inventor of the present invention discloses an integrated ophthalmic illumination method and system having two integrated light sources, a lamp and an infra-red (IR) diode laser. The lamp light source may be used to produce either monochromatic or color images, as necessary, at high resolution. 
     The problems involved with usage of lamps include poor luminous efficacy, high power and cooling requirements, environmental and user hazards and short lifetimes. A typical multi-color system using such lamps requires a set of filters and optics to separate the spectrum of the light produced by such lamps to the desired spectral components. In addition, the system will usually require a fast shutter due to the slow activation and slow deactivation of such lamps. 
     The above drawbacks are overcome when replacing the lamp with Light Emitting Diodes (LEDs). The technology of LEDs is rapidly growing and gradually replacing all current forms of ambient illumination specifically incandescent and fluorescent based light bulbs. With daily improvements in efficiency and power output, LEDs have the potential to replace all traditional light sources with the added benefits of very long lifetimes, low cost, lower power consumption, low voltage operation, simple cooling requirements and very rapid power output modulation (typically microseconds on-off times). LEDs are available as monochromatic sources (from the UV to the NIR spectrum) or as a more broadband source when combined with phosphors deposited on the LED emitter. 
     Thus, LEDs are an ideal light source for ophthalmic applications, enabling simple power and spectral output control in a compact package with a very long lifetime. The following prior-art references describe LED-based illumination systems: 
     U.S. Pat. No. 5,695,492 discloses apparatus for illuminating a central area of an eye by generally lamellar lighting during eye surgery. Basically, a support fixture carrying a light emitter such as a LED is adapted to be placed adjacent to the surgical field. The support fixture, when in place on an eye, directs light from the light emitter toward the surgical field tangentially to the cornea, at an angle of from about 0 degrees to 90 degrees to the plane of the eye iris. The light entering the eye travels along the lamellae of the cornea in the manner of a light pipe. Very little, if any light reaches the back of the eye, avoiding patient discomfort, or is directed toward the surgical microscope as glare. 
     US 20100318074 discloses an ophthalmic surgical system which includes a laser light source having a laser treatment mode and an illumination mode. The illumination system comprises a handpiece which is inserted into the eye through an incision in the pars plana region to illuminate the inside or vitreous region of the eye. Handpiece is connected to a laser light source by a light guide which is typically an optical fiber. 
     U.S. Pat. No. 5,966,196 of Eduardo Svetliza, the inventor of the present invention discloses apparatus for wide angle examination of the eye fundus. The apparatus includes an optical module providing a wide angle view image of the eye fundus and an image capturing unit connected to the optical module for capturing the wide angle view image. The apparatus also includes an illumination system comprising LEDs connected to a plurality of light guiding elements which are capable of transferring light from the LEDs to the eye. 
     It is an aim of the present invention to provide an integrated illumination system of low cost that is safe, easy to operate, and precise in any ophthalmic eye retina applications. 
     It is another aim of the present invention to provide an illumination system that is significantly small and compact, portable, and cordless to allow easy access to treated or monitored locations. 
     It is yet another aim of the present invention to provide an illumination system for controlling restricted light penetration and for superb manipulation of light and the resulting image. 
     SUMMARY OF THE INVENTION 
     A solid state based illumination system, in accordance with the present invention, illuminates the fundus through the sclera via direct contact or in very close proximity of the illumination system to the sclera. 
     The illumination system in accordance with the present invention provides a complete control of the light sources, i.e., control over parameters such as the light wavelengths and illuminating angle of projection light into the cavity of the eye as desired by the ophthalmologist. 
     The illumination system of the present invention comprises lighting elements required for retinal diagnosis such as perfect balanced color imaging, monochromatic restricted light imaging, and fluorescein angiography (FA) and Indocyanine green (ICG) in a single light source. 
     The illumination system of the present invention is based on a portable, cordless, small, compact and efficient LED ring with no fiber mediation for guiding light from one point to another and with minimal voltage/current requirements. Due to such characteristics, the LED ring of the present invention is a stand-alone ring that may be operated by a battery. Moreover, the LED ring is relatively small and compact to allow easy access to treated or monitored locations. This saves space and minimizes losses. 
     Additional advantages of the LED ring of the present invention are listed as follows: 
     1. The LED ring is designed to provide several modes of illumination. According to one mode of illumination, all of the LEDs are turned on as to provide an even illumination of the examined eye fundus. According to another mode of illumination, a selected group of LEDs is turned on while the rest of the LEDs are turned off, thereby illuminating the eye from a selected angle. For instance, an illumination angle of up to 270 degrees may be used in retina lighting surgery such as vitrectomy. Since such illumination angle may provide the required illumination for the surgery, insertion of a light probe thru the sclera may be avoided. 
     2. The LED ring may be used for angiography (fluorescein angiography-FA or indocyanine angiography-ICG) by using LEDs at the appropriate excitation wavelengths. 
     3. The LED ring may be used as a retractor of eyelids via direct scleral contact. 
     In accordance with some embodiments of the present invention, there is provided an integrated ophthalmic illumination system comprising: 
     a circumferential ring, having a tangential cross-section, 
     at least one miniature light source, said at least one miniature light source being mounted on the periphery of said circumferential ring, the light output of said at least one miniature light source is aimed at and illuminates the eye directly through the eye globe, and 
     a controller connected to said at least one miniature light source for controlling light intensity, light distribution, and restricted light of predetermined wavelengths. 
     wherein said circumferential ring is placed in the vicinity of the eye as a result of which said at least one miniature light source is either in close proximity to the eye or in contact with the eye during operation, 
     thereby said illumination system undergoing minimal light losses and having minimal voltage/current requirements. 
     In accordance with some embodiments of the present invention, there is also provided 
     An integrated ophthalmic illumination system comprising: 
     a circumferential ring, having a tangential cross-section, 
     at least one light source comprised of a light beam of multiple wavelengths, 
     a mediating mixing element, said mediating mixing element placed in proximity to said at least one light source to receive and to transform said light beam into a mixed beam, 
     a plurality of light guiding elements, said plurality of light guiding elements placed in close proximity to the output of said mediating mixing element to receive and to convey said mixed beam to said circumferential ring, and 
     a controller connected to said at least one light source for controlling light intensity, light distribution, and restricted light of predetermined wavelengths. 
     Furthermore, in accordance with the present invention, the light source is a solid state light source (SSLS) selected from LEDs, diode lasers, or diode pumped solid state lasers. 
     Furthermore, in accordance with the present invention, each one of said at least one miniature light source comprising a micro lens to collimate and direct the light into the eye. 
     Furthermore, in accordance with the present invention, each one of said at least one miniature light source comprising an annular window contacting the eye. 
     Furthermore, in accordance with the present invention, each one of said at least one miniature light source comprised of a micro lens collimating and directing the light into the eye. 
     Furthermore, in accordance with the present invention, said circumferential ring connected to a temperature detection element. 
     Furthermore, in accordance with the present invention, a band pass filter is placed against said at least one miniature light source. 
     Furthermore, in accordance with the present invention, said circumferential ring comprising between 1 to 18 light sources. 
     Furthermore, in accordance with the present invention, said controller operating said at least one light source either in parallel or in series. 
     Furthermore, in accordance with the present invention, said controller enabling separate control of each one of the at least one light source. 
     Furthermore, in accordance with the present invention, said controller monitoring the electrical power injected to each one of said at least one light source. 
     Furthermore, in accordance with the present invention, said controller monitoring the optical output each one of said at least one light source. 
     Furthermore, in accordance with the present invention, said illumination system is activated either via voice, pedals or manually. 
     Furthermore, in accordance with the present invention, said mediating mixing element comprised of a compound concentrator. 
     Furthermore, in accordance with the present invention, said mediating mixing element comprised of at least one mixing rod. 
     Furthermore, in accordance with the present invention, said mediating mixing element comprised of two mixing rods forming a Y shaped configuration. 
     Furthermore, in accordance with the present invention, said mediating mixing element comprised of a compound concentrator and at least one mixing rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention with regard to the embodiments thereof, reference is made to the accompanying drawings in which like numerals designate corresponding elements or sections throughout and in which: 
         FIGS. 1A-C  illustrate illumination systems in accordance with some embodiments of the present invention; 
         FIGS. 2A-C  illustrate additional illumination systems in accordance with some embodiments of the present invention; 
         FIG. 3A-C  illustrate further illumination systems in accordance with some embodiments of the present invention; 
         FIG. 4  illustrates control means for controlling any one of the illumination systems described above; 
         FIG. 5  illustrates fiber optic cables distributed around the sclera; 
         FIG. 6  shows mixing rod in accordance with some embodiments of the present invention; 
         FIG. 7  illustrates a compound parabolic concentrator (CPC) in accordance with some embodiments of the present invention; 
         FIG. 8  illustrates mixing device in accordance with some embodiments of the present invention. 
         FIG. 9  illustrates another mixing device in accordance with some embodiments of the present invention. 
         FIG. 10A  shows a cross sectional view of a LED ring in accordance with some embodiments of the present invention. 
         FIG. 10B  shows the LED ring of  FIG. 10A  in contact with a sclera 
         FIG. 11  illustrates top view of a LED ring with 12 LEDs in accordance with some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A-C , illustrate illumination systems  100 ,  200 , and  300  in accordance with some embodiments of the present invention. 
     Referring now to  FIG. 1A , illumination system  100  includes the following: a light source  102 , cooling device  104 , optical system  106 , light guiding element (fiber optic cable)  108 , and band pass filter  110 . 
     In accordance with some embodiments of the present invention, light source  102 , is selected from solid state light source (SSLS) such as LEDs, diode lasers, diode pumped solid state lasers or a combination of such. Light source  102  provides a set of illumination colors required for diagnosis, treatment, or surgery in certain medical applications and specifically in ophthalmic applications. 
     Optical system  106  is positioned against light source  102  to receive the light source respective output, collimate the light and couple it to a fiber optic cable  108 . 
     Optical system  106  may comprise multiple lenses that may be spherical, aspheric, cylindrical or of any other shape made of glass, plastic or optical ceramic. Optical system  106  may also comprise a parabolic concentrator. 
     In accordance with some embodiments of the present invention, optical system  106  is able to extract high intensity light from light source  102  and collimate it to the level required by the dichroic beam combiner (shown and described in  FIG. 2A ) for best reflectance, transmittance and minimum losses. 
     Cooling device  104 , in accordance with some embodiments of the present invention, may be a simple heat conducting plate, a finned heat sink, a heat sink integrated with a fan, a heat sink integrated with thermoelectric cooling device, a heat sink integrated with heat pipes, a water cooled heat sink or any other suitable cooling system. 
     Band pass filter  110  defines spectral band/s received from light source  102 . Band pass filter  110  may define spectral band/s received from multiple light sources. 
     Fiber optic cable  108  may be selected from fiber optic cables, liquid light guide cables, and the like. 
     Referring now to  FIG. 1B , illumination system  200  includes the following: 
     a light source  102 , cooling device  104 , and optical system  202  which is a collimating optical system required for operation with a dichroic beam combiner. 
     Referring now to  FIG. 1C , illumination system  300  includes the following: light source  102 , cooling device  104 , and fiber optic cable  302 . In this case, the output from light source  102  is extracted directly to fiber optic cable  302  with no mediating optics. 
     The desired shape of the light output from fiber optic cable  302  is achieved by transforming the geometry of fiber optic cable  302  and by adding optional optical components which alter the shape of the light output from fiber optic cable  302 . 
     Illumination systems  100 ,  200  and  300  further include a power monitoring system (not shown in the figures) controlling and providing indication of input power to each light source or to a combination of multiple light sources. 
     Referring now to  FIGS. 2A-C , there are shown illumination systems  400 ,  500 , and  600  in accordance with some embodiments of the present invention. 
     In  FIG. 2A  illumination system  400  comprising 4 light sources  102 A,  102 B,  102 C and  102 D each of which is positioned on cooling platforms  104 A,  1046 ,  104 C and  104 D respectively. As seen in the figure, the output from four light sources  102 A,  1026 ,  102 C and  102 D are combined to a single output which passes through fiber optic cable  402 . Light sources  102 A,  1026 ,  102 C and  102 D initially radiate on separate optical axes and are then combined via dichroic beam combiners  404   406  and  408  to a single multi-colored optical beam. 
     Dichroic beam combiner  406  combines the output of light sources  102 C and  102 D, dichroic beam combiner  404  combines the output of light sources  102 A and  1026 , and dichroic beam combiner  408  combines the output of combined light sources  102 A and  1026  with the output of combined light sources  102 C and  102 D. The combined output exiting from beam combiner  408  is fed to fiber optic cable  402  from which the various colored light beams are emitted homogeneously. 
     In  FIG. 2B  illumination system  500  includes 2 dichloric combiners to combine the light output from 3 light sources into a single beam. Illumination system  500  comprises 3 light sources  102 A,  102 B and  102 C each of which is positioned on cooling platforms  104 A,  104 B and  104 C respectively. Dichloric beam combiner  502  combines the output from light sources  102 A, and  102 B into a single beam which then combines with the output from light source  102 C via dichloric beam combiner  504 . The combined light beam exiting dichloric beam combiner  504  is fed to fiber optic cable  506 . In  FIG. 2C  illumination system  600  comprises light sources  102 A,  102 B,  102 C and  102 D each of which is coupled to fiber optic cables  602 ,  604 ,  606  and  608  respectively. 
     Fiber optic cables  602 ,  604 ,  606  and  608  are all joined mechanically to a bundle or fused to a single fiber optic cable up to terminal piece  610 . At some point near terminal piece  610  each one of fiber optic cables  602 ,  604 ,  606  and  608  is split into two fiber optic cables  602 A&amp;B,  604  A &amp;B,  606 A&amp;B and  608 A&amp;B and arranged around the sclera  612  as seen in the figure. 
     Fiber optic cables  602  A&amp;B,  604  A&amp;B,  606  A&amp;B and  608  A&amp;B contact sclera  612  at two opposing points.  4  fiber optic cables contact sclera  612  at each one of the two opposing points with red, green, blue (RGB) and NIR bands. It should be noted that other arrangements with more fiber optic cables per each color are possible as described below in  FIG. 3B . 
     As the output from fiber optic cables  602 ,  604 ,  606  and  608  may naturally diverge, it may be necessary to add an optical system to focus, de-focus or collimate the beams as required by the application. Such an optical system may be a single or multi element system. It may be an optical element shaped to adapt the final output shape. For example, in the case of an annular fiber, the optical system may comprise a Fresnel lens with its center cut out to provide an annular lens. A flat lens, made of plastic or glass, may focus the light output to a common point as required by the application. Thus, an optical system (not shown in the figure) may be connected to fiber optic cables  602 ,  604 ,  606  and  608 , to terminal piece  610 , or to both. 
     It should be noted that fiber optic cables  602 ,  604 ,  606  and  608  are mechanically positioned in a stable manner and at the correct distance from the optical systems so that any handling of fiber optic cables  602 ,  604 ,  606  and  608  may not affect power input and output to and from the cables. Fiber optic cables  602 ,  604 ,  606  may be joined mechanically to a single bundle up to terminal piece  610  which is designed to interface with the human or animal body to provide the required diagnostic, treatment, or surgery capabilities. 
     It should be noted that fiber optic cables  602 ,  604 ,  606  may have various geometries other then multi strand bundles depending on the application. 
     It should be noted that since terminal piece  610  is in close proximity to the sclera during operation, a good coupling of the illumination light into the eye is facilitated, and due to the geometry of the terminal piece  610 , illuminating all around the iris and/or between the Ora Serrata and the Equator of the eye is facilitated. Furthermore, due to the efficient coupling and scattering characteristics of the sclera, the fundus can be illuminated evenly over its entire area. 
     The above is true for each of the light spectral components used for such applications, i.e., blue, green, and red lights and/or near IR. 
     Referring now to  FIG. 3A , there is shown illumination system  700  comprising light sources  102 A,  102 B and  102 C, cooling systems  104 A,  104 B and  104 C, optical systems  708 ,  710 , and  712  and fiber optic cables  714 ,  716  and  718 . 
     Each one of light sources  102 A,  102 B and  102 C is coupled to each one of fiber optic cables  714 ,  716  and  718  via optical systems  708 ,  710  and  712  respectively. 
     Referring now to  FIG. 3B , there is shown illumination system  800  comprising light sources  102 A,  102 B and  102 C, cooling systems  104 A,  104 B and  104 C, optical systems  808 ,  810 , and  812  and fiber optical cables  816 ,  818  and  820 . 
     Each one of light sources  102 A,  102 B and  102 C is coupled to each one of fiber optical cables  816 ,  818 , and  820  via optical systems  808 ,  810 , and  812  respectively, and in this case, the various colors, red, green, and blue (RGB) are distributed in a discrete manner around the annular output  822 . The color distribution as illustrated is symmetrical, however, other color arrangements are possible. 
     Each one of optical systems  808 ,  810 , and  812  is positioned against each one of light sources  102 A,  102 B, and  102 C to extract the respective output of light, to collimate the light and focus it into each one of fibers  816 ,  818 , and  820 . 
     Such optical systems  808 ,  810 , and  812  may comprise multiple lenses made of glass, plastic or ceramic and having spherical, aspheric, cylindrical or any other shape. Furthermore, the optical systems  808 ,  810  and  812  may also include a parabolic concentrator. 
     Optical systems  808 ,  810  and  812  may be able to extract maximum power from light sources  102 A-C, collimate and focus the beams to the level required by the fiber optic cables  816 ,  818 , and  820  for best transmission/reflectance and minimum losses in the overall system. 
     Referring now to  FIG. 3C , illumination system  900  comprising 3 light sources  102 A,  1028 , and  102 C, cooling systems  104 A,  1048  and  104 C, and fiber optic cables  908 ,  910 , and  912 . 
     Each one of light sources  102 A,  1028 , and  102 C is coupled to each one of fiber optic cables  908 ,  910  and  912  without mediating optics. Fibers  908 ,  910  and  912  are bundled together until reaching a terminal piece (not shown in the figure). 
     Illumination system  900  may be structured as follows: 
     Each one of light sources  102 A-C is positioned on corresponding cooling systems  104 A,  104 B and  104 C. Fiber optic cables  908 ,  910 , and  912  are positioned close to or in contact with the emitting apertures of light source  102 A-C. In this case, band pass filters and photodiodes are not needed between light sources  102 A-C and fiber optic cables  908 ,  910 , and  912  since the light sources (LEDs) emit monochromatic light. Optical systems are not needed as well in this case. Such an arrangement, called “butt coupling”, has the advantage of simple and efficient coupling. 
     Referring now to  FIG. 4 , there is shown control means  1000  to control any one of the illumination systems described above. Control means  1000  comprising any one of the described light sources  1002 , controller/driver  1004 , and fiber optic cable  1006 . 
     Controller/driver  1004  comprising power input  1004 A, connection to central control (USB, Ethernet)  1004 B, and External control lines (TTL, 24 VDC)  1004 C. 
     Fiber optic cable  1006  is connected to annulus  1008 . Annular light output  1010  is expanded from annulus  1008 . 
     Referring now to  FIG. 5 , there is shown fiber optic cables distribution  1100  around the sclera. As seen in the Figure, fiber optic cables  1102 , distributed around imaging lens barrel  1104 , extend beyond the barrel to come in contact with the sclera  1106 . 
     Referring now to  FIG. 6 , there is shown mixing rod  1200  in accordance with some embodiments of the present invention. Mixing rod  1200  having input and output cross sectional areas of 1.times.1 mm.sup.2. 
     Mixing rod  1200  may have square, circular, hexagonal or any other input and output cross sectional areas. 
     As seen in the figure, printed circuit board (PCB) with multiple-source butt  1202  enters mixing rod  1200 , and mixed light  1206  is emitted in a 160-degree cone. 
     The light entering mixing rod  1200  travels along mixing rod  1200  in total internal reflection mode and exits mixing rod  1200  with the multiple wavelengths mixed. The degree of mixing depends on the source numerical aperture (NA), the length of mixing rod  1200  and on the geometry of the input and output surfaces of mixing rod  1200 . 
     The output surface of mixing rod  1200  may be butt coupled to the fiber bundle input surface. The light may exit the fiber bundle homogenously, but there may still be significant losses due to NA mismatch between the output surface of mixing rod  1200  and the input surface of the fiber bundle. Light losses may be overcome by increasing system sensitivity and/or increasing light intensity. 
     In order to reduce light losses, a NA reducing element may be inserted between the output plane of the light source and either the fiber bundle input plane or the mixing rod  1200 . 
     A NA reducing element may be a compound parabolic concentrator (CPC) as shown in  FIG. 7  which is widely used to collimate LED strongly diverging sources. 
     Referring now to  FIG. 7 , there is shown CPC  1300  in accordance with some embodiments of the present invention. CPC  1300  having input and output cross sectional areas of 1.times.1 mm.sup.2. CPC  1300  may have parabolic, hyperbolic, conical, freeform or other cross sectional area. 
     Multiple-source butt  1202  enters CPC  1300 , and mixed light  1302  is emitted from CPC  1300  in a 160-degree cone. 
     CPC  1300  may either reflect or refract the rays at high NA at an angle more compatible with fiber NA and may hardly affect the rays propagating at low NA. 
     Losses at CPC  1300  itself are low and mainly due to absorption or scattering. 
     Referring now to  FIG. 8 , there is shown mixing device  1400  in accordance with some embodiments of the present invention. Mixing device  1400  comprising CPC  1300  connected to mixing rod  1200 . Multiple-source butt  1202  enters CPC  1300 , and mixed output light  1402  is emitted from mixing rod  1200  in a 160-degree cone. 
     In this case the output NA is significantly small, and mixed light with reduced NA is easily coupled to fiber bundle by butt coupling. 
     Referring now to  FIG. 9 , there is shown mixing device  1500  in accordance with some embodiments of the present invention. Mixing apparatus  1500  comprising mixing rod  1904 A and mixing rod  1904 B which are connected in a way to form a Y shaped configuration. Light sources  1902 A and  1902 B are fed into mixing rods  1904 A and  1904 B respectively. Mixed output light  1906  is emitted from mixing rod  1904 B in a 160-degree cone. 
     It should be noted that the configuration of mixing apparatus  1500  may be expanded to include more sources in more complex geometries. 
     In  FIGS. 6-9  multiple-source butt  1202  is mixed and coupled to a fiber optic bundle either directly or by using either mediating mixing element as mixing rod  1200  of  FIG. 6 , or mediating optical element as CPC  1300  of  FIG. 7 , or combination of both elements as mixing device  1400  of  FIG. 8 . In all cases the output light from the fiber bundle is characterized by a homogeneous color mixture. Thus, according to some embodiments of the present invention, an illumination system may be comprised of: 
     a. Light source or sources comprised of multiple wavelengths mounted close to each other either in a planar configuration or in a spherical or other configurations. 
     b. A compound concentrator, providing collimation capabilities, placed in close proximity to the light source/s so that the emitted light impinges on the compound concentrator. 
     c. A mixing rod placed in close proximity to the concentrator output enabling a homogeneous color output from the mixing rod. 
     d. Light guiding elements, a fiber bundle, placed in close proximity to the mixing rod output—conveying the light mixture to the useful end of the fiber bundle. 
     e. The end of the fiber bundle is split into individual fibers and each fiber is attached to a ring shaped structure to form a fiber annulus. The fibers are placed at an angle corresponding to sclera curvature so that when the fibers contact the sclera, they exert minimum pressure on sclera. 
     Referring now to  FIGS. 10A and 10B ,  FIG. 10A  shows a cross sectional view of LED ring  1600 , and  FIG. 10B  shows an integrated unit  1700  comprised of LED ring  1600  of  FIG. 10A  and eyelid retractor  1622 . 
     LED ring  1600  is a circumferential ring, having a tangential cross-section. 
     LED ring  1600  comprising disposable annular lens array  1602 , fixed annular window  1604 , filter per LED  1606 , LED  1608 , single LED PCB  1610 , annular PCB  1612 , wires  1614  soldered to LED PCB  1610  and to annular PCB  1612 , LED PCB base  1616 , ring housing  1618 , and connector or cable input to annular PCB  1620 . 
     The schematic position of LED ring  1600  on sclera is shown in  FIG. 10B . As noted above, LED ring  1600  may be a stand-alone ring operated by a battery. Integrated unit  1700 , in accordance with some embodiments of the present invention, may enable the use of such a battery operated LED ring as the battery may be situated in eyelid retractor  1622 . 
     Referring now to  FIG. 11 , there is shown top view of LED ring  1600  with 12 LEDs-4 LEDs emitting red light, 4 LEDs emitting green light and 4 LEDs emitting blue light. Each LED  1622  comprising micro lens  1624 , solder pad on PCB  1626 , Be—Cu spring strip  1628 , and cable or connector pads  1630 . 
     In accordance with some embodiments of the present invention, LED ring  1600  may be placed in close proximity to the sclera with no fiber mediation. This is possible due to the miniature LEDs. For instance, the dimensions of Luxeon Z LED series from Lumiled Corporation are 1.7 mm.times.1.3 mm.times.0.7 mm with a 1 mm.times.1 mm emitter. Such dimensions enable placing up to about 18 LEDs in LED ring  1600  and around the eye globe with the LEDs pointing at the ora serrata for best transmission through the sclera and through the pars plana zone up to the eye equator. 
     In accordance with some embodiments of the present invention, LEDs of various wavelengths may be placed around ring  1600 , and there may be an equal number of LEDs emitting light of same color around ring  1600 . For instance, a 4 color ring may be assembled with 16 LEDs where 4 LEDs emitting same color are placed in a cross configuration. Such an arrangement ensures equal illumination of the whole fundus with each color. 
     In other configurations RGB LEDs may be placed around ring  1600  in asymmetrical geometries. For example, two sets of RGB LEDs may be placed around ring  1600  with 180 degrees with respect to each other or any other geometric arrangement required for efficient illumination of the retina. 
     In other configurations, the ring may comprise light sources of a single wavelength for providing greater illumination at that wavelength. For example, when performing angiography, the ring may consist a single or multiple LEDs operating only at the required excitation wavelength. 
     In accordance with some embodiments of the present invention, each one of the LEDs is soldered to an individual PCB  1632  and placed on ring  1600 . In this case, ring  1600  is designed to hold the LEDs in place where the light outputs are aimed in a direction perpendicular to the sclera. 
     Ring  1600  is placed on annular PCB  1632  where each LED is connected with two wires to the annular PCB  1632 . The annular PCB  1632  may operate the LEDs in series or in parallel and may enable separate control of each LED or group of LEDs. The annular PCB  1632  has a connector or solder pads for cable connection. 
     In another configuration, LED PCBs are wired together since there is no annular PCB  1632 . However, this configuration is less convenient due to wiring complexities and wires volume. 
     In yet another configuration each LED  1622  is connected to the annular PCB  1632  by two Be—Cu leaf spring  1628  with no LED PCB mediation. The two springs act as current conductors and heat conductors. 
     The supporting area of ring  1600  in contact with the LED PCB and the overall supporting structure may warm up, and ring  1600  may be cooled down by conduction to the surrounding air. 
     If filtering is needed, a band pass filter  1606  may be placed after each LED  1608 . 
     The fixed annular window  1604  is the part of ring  1600  that contacting the sclera. Fixed annular window  1604  may include a micro lens  1602  per LED for collimating the LED&#39;s light. Such micro lens  1602  directing a greater amount of the LED light into the eye instead of losing the light to ring light interior or in other directions. 
     Window  1604  is designed to adapt to the curvature of the sclera, and the design may be adapted to eye dimensions of neonatal, adults and animals. 
     Ring  1600  and annular PCB  1632  structure are enclosed by a plastic and/or metal structure. 
     All parts of ring  1600  may be either printed (including plastic optics) or manufactured by conventional machining processes. 
     In a different configuration, the fixed annular window  1604  may be made from 2 parts: a fixed part and a disposable part. The fixed part is a window, the disposable part may be either a window, a micro lens, a silicon cover or any other material conforming with medical regulatory acceptance. The disposable part is the only part that comes in actual contact with the eye. 
     After each examination the disposable part is easily removed and disposed. A new disposable part is easily inserted making the unit ready for another test. Thus, sterilization of the fixed part is not required. 
     It should be noted that the structure of ring  1600  may warm up only slightly and may not reach a temperature that may be hazardous for the following reasons: 
     a. Light source/s of each color is/are operated separately and for a short duration. 
     b. Light source is in close proximity to the eye, thus transmission losses are minimal—the operation current may be low and consequently heat generation may be low as well. 
     c. Fixed annular window is in touch with the sclera and is thermally isolated from the support structure. 
     d. Temperature detection element, such as a thermocouple, may be connected to the ring and if the temperature reaches the safety limit, the control system may disconnect the current. 
     It should be noted that in accordance with some embodiments of the present invention, each LED may be controlled by a central control system or a system computer. Optionally a common controller may control all LEDS and may be connected to a central control system or system computer. 
     In accordance with the present invention, the controller monitors electrical power injected to each LED and may monitor the optical output of each LED. The controller incorporates all necessary safety features to ensure correct and safe operation of the illumination system. 
     In accordance with some embodiments of the present invention, the illumination system may be either manually controlled (using keyboard or switches on unit), voice activated or even activated via pedals. 
     In accordance with the present invention, packaging the illumination system enables safe and secure positioning of the light sources, optics, filters and cables. The packaging contains a cover to protect users from possible scattered light and to enable cable connection. 
     EXAMPLES 
     Example I—Fundus Imaging 
     The illumination system, in accordance with the present invention, enables efficient, homogeneous and safe illumination of the fundus at one or more colors typically ranging from 440 nm to about 800 nm. The fundus can be photographed using one color providing an image of features illuminated at that color. In accordance with the present invention, images can be acquired at three colors such as blue, green and red and the images computer combined to provide a full true color image. Any combination of colors can be used to provide specific details to a required diagnosis. Illumination using the disclosed invention requires no moving parts and images can be taken at different colors very rapidly using the fast modulation characteristics of the SSLS. 
     Example II—Fluorescein Angiography 
     Fluorescein angiography is a technique for examining the circulation of the retina and choroid using a fluorescent dye and a specialized camera. It involves injection of sodium fluorescein into the systemic circulation, and then an angiogram is obtained by photographing the fluorescence emitted after illumination of the retina with blue light at a wavelength range of 490-520 nanometers. The disclosed invention enables homogeneous illumination at the required wavelength. 
     A separate imaging system monitors the emission from the fluorescein. 
     Example III—ICG Angiography 
     Indocyanine Green angiography (ICG) is a procedure which images the choroid. This layer, the choroid, is deeper than the retina and normally obscured by pigmentation. In contrast with sodium fluorescein, ICG fluoresces in the infrared after excitation at around 800 nm. The disclosed invention enables homogeneous illumination at the required wavelength using an IR LED or an IR diode laser. A separate imaging system monitors the emission from the ICG.