WO2007055668A2

WO2007055668A2 - Portable slit lamp with built-in digital camera and illuminating diaphragm

Info

Publication number: WO2007055668A2
Application number: PCT/SI2006/000037
Authority: WO
Inventors: Grisa Mocnik; Boris Vedlin; Matjaz Zalar; Xavier Lescure
Original assignee: Optotek D.O.O.; Dioptrix, 13
Priority date: 2005-11-14
Filing date: 2006-11-14
Publication date: 2007-05-18
Also published as: WO2007055668A3; SI22179A

Abstract

A portable slit lamp with a built-in digital camera (2) and an illuminating diaphragm (11) enables a simultaneous visual observation and capturing of good quality photographs of the inspected eyes. In the course of eye examination the physician can take single images or sequences of images or moving pictures segments. A special illumination diaphragm (11) projects onto the eye an illumination slit of chosen form and in addition ensures an increased amount of light for photographing by comprising next to the slit two side openings having the form of a circle section. The constructional solution is such as to enable that the illumination diaphragm can be built into portable or stationary slit lamps designs. To enable the observation of the eye posterior a noncontact lens is attached onto the slit lamp in such a way that the focal point of the noncontact lens coincides with the focal point of the microscope objective and that the light beams passing from the noncontact lens onto the eye of the patient are parallel.

Description

PORTABLE SLIT LAMP WITH BUILT-IN DIGITAL CAMERA AND ILLUMINATING DIAPHRAGM

Field of the invention

This invention relates to instruments for ophthalmic diagnostics. More particularly, to relates to illuminating devices and camera means used in eye examination.

Summary of the invention

The object of the present invention is to offer a portable slit lamp with a built-in digital camera, which is equipped with a special illuminating diaphragm such as to ensure that a sufficient quantity of light is projected onto the inspected area in order to enable a satisfactory capture of images of the examined eye. With the aid of said illuminating diaphragm a clear picture shall be taken of the portion of the eye illuminated by a narrow light slit, which by itself usually does not offer enough light for clear and distinguishable photographs. A further object of the invention is to provide a suitable constructional solution so that it would be possible to build the illuminating diaphragm into portable or into stationary designs of the slit lamp regardless of the type of the light source.

Yet another object of the invention is to offer an arrangement disposed on the portable slit lamp and capable of receiving a noncontact lens, which is designed for observation of the eye fundus and is usually not integrated into the slit lamp. To this end, a holder is designed onto which the noncontact lens can be attached in such a way that the focus of the lens coincides with the focus of the slit lamp.

Background to the disclosure

The slit lamps are used in eye examination for illuminating the selected portions of the eye through an illumination slit. If the ophthalmologist can take the photographs of the observed portions of the eye at the same time as he/she carries out the inspection, such option represents a great help to him/her as the images can be inspected at a later time and in greater detail, moreover, he/she can form a data base containing a comprehensive information on the condition of the eyes of his/her patients.

The amount of light projected onto the inspected eye through the illumination slit of a slit lamp is too low to enable the digital cameras, except for very expensive ones, to produce good quality shots. The cause of this limitation lies in the fact, that the sensor of the digital camera is not able to adequately integrate the individual points into a whole picture under weak light conditions. In addition, the speed of integration is lowered considerably, so also the chance for shooting a sequence of clear pictures or a clear video clip is reduced. Consequently, the shots are of poor quality and unclear and often useless for the ophthalmologist as the pictures do not show an actual visual image of the illuminated portion of the eye.

Several solutions have been proposed for improving the illumination produced by the slit lamps or by other devices for eye inspection. In general, these solutions can be classified in three groups. The first group encompasses the devices with built-in additional illuminating source. Such solutions are described for example in the patents JP2004290461 , JP2003299619, JP2002102173, US6072623 and LJS5196874. The second group includes the designs containing a single light source and branched optical paths. An example of such solution is presented in the patent US4102565. The third group comprises the designs featuring a light amount change device designed to change the amount of illumination light on the side of the light source. Such solution is disclosed for example in the patent US6283596. The problems associated with the solutions of the first and second group are additional illuminating sources and special structures for light paths, respectively, which make the device structure cumbersome and represent a serious drawback especially in the case of portable slit lamps. Besides, the handling of such slit lamps is difficult and less reliable. The main difficulty arising with the third group of solutions is the fact that they do not enable simultaneous photographing of the eye structures lying beyond the range illuminated only by the narrow light beam.

In order to observe the posterior of the eye, the ophthalmologist places a high diopter noncontact lens between the eye of the patient and the output objective of the slit lamp microscope. The focus point of the noncontact lens shall coincide with the focus point of the slit lamp microscope. With known slit lamp designs the lens has to be held by hand which makes the examination of the eye difficult. It is also very hard to ensure a constant coincidence of both focuses, i.e. of the focus of the noncontact lens and the focus the slit lamp microscope.

Description of the invention

The essential features of the portable slit lamp with built-in digital camera and illuminating diaphragm according to the present invention consist in enabling a simultaneous visual inspection and photographing of a selected spot in the eye and in ensuring sufficient illumination of the eye, so that good and clear shots can be produced.

From a light source the beam of light travels firstly through condenser optics, passes then through one of the slits disposed on an illumination diaphragm, and finally progresses through a posterior objective and through a prism or a mirror onto the inspected eye. The illuminating slit projected onto the eye has a uniformly bright lighting across its entire surface, which can be provided for example by means of a Koehler illumination technique. The photograph taken by the digital camera captures the section of the eye which is illuminated by the light projection of a narrow illuminating slit, this section being the principal concern of the physician. A sufficient amount of light for the sensor of the digital camera is provided by means of two additional apertures disposed along each side of the illuminating slit. These additional apertures ensure that also the area in close proximity of the slit image is illuminated. At the same time, such added illumination can facilitate the direct inspection of the observed portion of the eye as well.

The portable slit lamp with built-in digital camera and illuminating diaphragm according to the present invention is presented in more detail in continuation of the description by reference to the drawings in which

Figure 1 is a schematic representation of the portable slit lamp with built-in digital camera and illuminating diaphragm;

Figure 2 is a schematic representation of the illuminating diaphragm, which includes next to conventional slits for eye inspection also a slit, as shown on figure 2a, or an aperture, as shown on figure 2b, designed for photographing the eye by a digital camera; Figure 3 is a schematic representation of the magnifying elements designed for inspection and photographing, shown in a view from above;

Figure 4 is a schematic representation of the magnifying elements designed for inspection and photographing, shown in a side view; Figure 5 is a schematic representation of a noncontact lens, designed for observation of the posterior of the eye, positioned on the slit lamp.

By means of a slit lamp the eye is illuminated by an illuminating slit produced as an image of a chosen slit aperture. As shown in figure 1 , in the optical assembly 35 the light beam originating from the light source 1 , which can be one or several white LEDs or light bulbs, is projected through the condenser optics 3 to the rear objective 12, which directs the light beam through a prism 13 onto the eye in order to produce a uniformly illuminated image of the selected slit. A turning plate 20 offers different light filters, for example an attenuation filter, a blue filter, a green filter, as well as a hole designed to pass the white light of the light source 1. The physician places a selected filter or a hole above the light beam originating from the light source 1 by turning the plate 20.

As shown in figure 2, the illumination diaphragm 11 comprises several openings of different forms and sizes to allow that various illuminating slits are produced. One of the openings is shaped in a special way to enable photographing by the digital camera 2. The said special opening consists of three apertures, of which the central aperture 22 has the same function as the common slits in the slit lamps, while the two side apertures 23 and 24 serve for additional lighting needed for clearer pictures. In the first embodiment of the invention, the aperture 22 has a shape of a common slit such as is utilized usually in the slit lamps, as shown in picture 2a. In the second embodiment of the invention, the aperture 22 has a shape of a square or a rectangle, as shown in figure 2b. A square or rectangular aperture allows the physician to illuminate smaller details in the eye. The side apertures 23 and 24 are shaped preferably as sections of a circle and are disposed symmetrically with respect to longitudinal axis of the aperture 22. The side apertures 23 and 24 ensure that enough light is irradiated from the eye onto the sensor 30 of the digital camera. Besides, they provide that the portions of the eye next to the projected narrow illumination slit are illuminated as well. The apertures 22, 23 and 24 are not interconnected. The illumination diaphragm 11 contains also the slits of other forms designed for eye inspection, for example the slits 21 , 36 and 37. By means of rectangular slits 21 and 36 narrow portions of the eye can be inspected. The round slit 37 allows that larger portions of the eye are illuminated and can illuminate the entire field of vision of the digital camera. In order to illuminate the areas of different sizes, the physician sets the apertures of different forms above the light source by simply turning the illumination diaphragm 11 around its central axis. The illumination diaphragm 11 can be build into portable as well as into stationary designs of the slit lamps. The intensity of the light source 1 and a correct ratio between the voltage and the current through the light source 1 are regulated by a control circuit 14. The intensity of illumination can be adjusted manually by means of adjusting means 18, which may be a turning knob or a sequence of pushbuttons. The optical assembly 35 and the handle 6 with associated optics can be turned around the vertical axis 31 running through the focus 25 of the slit lamp.

The digital camera 2 is built in the housing of the slit lamp, for example in the handle 6, and is supplied by main battery 10 or by an outside power supply. The image of the eye is projected onto the digital camera 2 through the assembly of lenses consisting of the following optical elements: a microscope objective 15, a magnifying lens 8 and a camera objective 19 as shown in figure 1. A mirror 7 positioned between the magnifying lens 8 and the camera objective 19 directs the light destined for the digital camera 2 from the horizontal plane into the vertical plane. If the longitudinal (vertical) axis of the digital camera 2 and the axis of the sensor 30 are not parallel, as in the case shown in figure 4, an additional mirror 38 is placed between the camera objective 19 and the sensor 30 to ensure that the light is deflected from the vertical plane to fall onto the sensor 30. The magnification of the camera objective 19 may be equal to magnification of the ocular 16 so that the photographing of the eye is performed with a magnification equal to magnification used by the physician for visual inspection of the patient's eye. Besides, the directions of visual observation and of photographing of the eye are equal, as the light from the eye passes onto the digital camera through the microscope objective 15, which serves at the same time also for visual observation of the eye through the ocular 16. For photographing the magnification can be altered by exchanging the camera objective 19. A somewhat greater magnification for photographing as compared to magnification for visual inspection is often requested to achieve better depth sharpness.

The medium magnification of the slit lamp is defined by the microscope objective

15 and the ocular 16 and by the microscope objective 15 and camera objective 19, respectively. By means of a magnifier 8 the magnification can be increased or decreased simultaneously for the inspection and for photographing. The magnifier

8 may function as a magnifying device or as a minifying device depending on its position. The magnifier can be realized as a Galilean afocal system, such as shown on figures 1 , 3, and 4 where pairs of lenses positioned in a turning drum are utilized, or as a zoom system where the position of magnifying lenses is changed.

For the control of the digital camera 2 and for the interaction between the digital camera 2 and the physician the following means are provided: a screen 9, pushbuttons 5 for controlling the digital camera 2, a standard output 4 that enables interconnection between the digital camera 2 and the computer, and an input 17 for connection of an optional foot switch 33 for triggering the digital camera 2. The digital camera 2 may operate in photo mode designed to capture single images or sequences of images, or in video mode intended for capturing moving pictures segments. The digital camera 2 may comprise a memory for storing captured images and video clips.

As shown in figure 5 the additional noncontact lens 26 for observing the eye posterior is fixed on a special rod 27 placed on the spot where usually a gauge rod for the slit lamp is inserted. The rod 27 ensures such positioning of the noncontact lens 26 between the microscope objective 15 and the eye 28 of the patient that the focal point of the noncontact lens 26 coincides exactly with the focal point 25 of the microscope objective 15. As a consequence, the light beams 29 passing from the noncontact lens 26 onto the eye 28 of the patient are parallel. Through the cornea and eye lens 32 the parallel light beams 29 converge toward a point on the retina 34 that can be inspected meticulously and photographed at the same time by the physician. Such solution for fixed positioning of a noncontact lens 26 facilitates the inspection since the physician does not have to hold the lens in his/her hand and since optimal distance between the lens 26 and the focal point 25 of the microscope objective 15 is ensured during the whole time period of inspection.

Claims

1. A portable slit lamp with built-in digital camera and illuminating diaphragm, characterized in that a light source (1) projects a light beam through a condenser optics (3), a turning plate (20) with light filters, an illumination diaphragm (11), a rear objective (12) and a prism (13) onto the eye, where an image of a slit is produced; that the illumination diaphragm (11 ) includes in addition to slits (21 ; 36; 37), which feature different forms and can be chosen in an easy way by the physician to produce a desired illumination slit on the observed eye, also a special set of openings designed for photographing, the said special openings set comprising a slit (22) having the form of a narrow rectangle and two side openings (23; 24) having the form of a circle section, wherein the said illumination diaphragm (11) ensures sufficient illumination for photographing in the course of eye inspection, the photographing being carried out with a digital camera (2) integrated in the handle (6) of the slit lamp.

2. An illumination diaphragm (11) according to claim 1 , wherein the slit (22) has the form of a square or a rectangle.

3. An illumination diaphragm (11 ) according to claim 1 , wherein the illumination diaphragm can be built into portable or stationary designs of the slit lamps.

4. Attachment of an additional noncontact lens onto the slit lamp, the said noncontact lens being designed for observation of the eye posterior, characterized in that a noncontact lens (26) is fixed onto a removable rod (27) disposed on the slit lamp in such a way that the focal point of the noncontact lens (26) coincides with the focal point (25) of the microscope objective (15) and that the light beams (29) passing from the noncontact lens (26) onto the eye (28) of the patient are parallel.