Filter apparatus for retinoscope

Abstract: A retinoscope is provided with a hinged light filter carrier assembly (28) for slidably positioning first and second polarizing filters (60,62) in the light transmission and viewing paths (20,24). A single actuating lever (64) is provided to move the filter members into and to retract them out of the light paths. The carrier assembly is a unitary frame member (32) with a back portion (34,36,38) and a lower portion (52, 54) which slide in respective pairs of grooves (56-59) in the retinoscope housing (12) and are mechanically synchronized by a pair of struts (44,46) joined by living hinges (40,42,48,50) to the frame members.

Description: Background of the Invention This invention relates to medical diagnostic instruments and more particularly to a retinoscope having a linear light polarizer filter mechanism for eliminating glare when refracting a patient's eye. Prior art retinoscopes have heretofore not been equipped with filters for reducing glare. Retinoscopes are used in association with refractors or phoroptors in which a series of trial lenses are placed in the optical path of the instrument to determine a patient's refractive error. These trial lens devices contain a number of different specular lens surfaces as well as sealing windows, all of which can cause glare. Polarized light reflected from specular surfaces such as trial lenses, refractor windows and the cornea of the eye will remain polarized, while light reflected from a diffuse surface, such as the retina of the eye, will lose its polarization. By taking advantage of this phenomena, the glare reflected from specular surfaces in the optical path of a retinoscope can be virtually eliminated by placing a suitable polarization filter in the optical path of the instrument. The term optical path as herein used is broad enough to include both the viewing axis of the instrument and the light path of the instrument which typically are brought together by means of a beam splitter or the like. Various prior art devices have offered different polarizing filters for the transmitted light and for the viewing light and they have been positioned in place by various levers and knobs. In U.S. Patent 4,998,818 to Kugler et al., which has been assigned to a common assignee together with the present application, there is shown a device for positioning a pair of polarizing filters in the transmission and viewing pathways of an ophthalmoscope by actuation of a single control. This device has proven to be very effective and offers, in addition to the simplified insertion of the polarizing feature, other filter features all actuated by the same control. The present invention is directed primarily to a retinoscope and provides a simplified single control apparatus for inserting and removing a polarizing filter system into the optical path of the instrument to reduce glare from specular surfaces in the optical path. Objects and Summary of the Invention Accordingly, it is an object of the present invention to provide a retinoscope with a polarizer assembly that can be simply and easily positioned in and out of the optical path of the retinoscope. It is another object of the present invention to provide a polarizing assembly for a retinoscope that can be simply and easily and economically manufactured. It is another object of the present invention to provide a single function control polarizer assembly for a retinoscope having a minimum of individual parts and thus provide for ease of operation and long life. It is a still further object of the present invention to provide a polarizer assembly for a retinoscope that can be made from simple molded plastic parts while still providing high quality glare-free examination of the retina of the eye. These objects of the present invention are solved by a retinoscope as defined in claim 1. In one preferred embodiment there is provided a pair of filters slidably mounted in tracks so that one will be positioned in the light transmission path of an illumination source, and one in the light viewing path of the instrument. The filter members are joined together by a hinged member such that movement of the one filter into operating position will cause the other filter to also move into its operating position. Brief Description of the Drawings For a better understanding of these and other objects of the present invention, reference is made to the detailed description of the invention which is to be read in conjunction with the following drawings, wherein: Fig. 1 is a perspective view of a retinoscope in accordance with the present invention; Fig. 2 is an enlarged cross-sectional view of the optical head of the retinoscope of Fig. 1. Fig. 3 is a perspective view of the filter carrier of the present invention; Figs. 4 and 5 are reduced scale cross-sectional views showing the operating and storage positions, respectively of the filter carrier of Fig. 3; and Fig. 6 is a diagrammatic view showing a retinoscope used in conjunction with a refractor. Detailed Description of a Preferred Embodiment Referring now to Figs. 1 and 2, the retinoscope 10 according to the present invention has a main body portion 12 containing most of the elements of the optical system and a neck 14 that is adapted to be releasably connected to a conventional battery handle 16. As may be seen in Fig. 2, the source of illumination 18 is positioned in the neck 14 and oriented to project a beam of light upward along the dotted line 20 to the mirror or beam splitter 22 for reflection out a light path 23 through the front of the instrument into the patient's eye. A third path or viewing passage 24, again shown by dotted lines, extends from the front face of the instrument through the beam splitter to the physician's eye piece 26 at the back of the instrument. A polarizer/filter carrier assembly 28, shown in Fig. 2 in the inoperative position, will be explained in detail herein. The usual resilient browrest 30 for positioning the instrument on the physician's brow is also provided. Turning to Fig. 6, the retinoscope 10 embodying the present invention is shown being used in association with a refractor 90 to view the eye 91 of a patient. As is well known, the refractor is arranged to accept a plurality of different lenses to determine the patient's refractive error. In addition, the refractor typically contains windows, front and rear, situated along the optical axis 93 for protecting the lenses. As noted above, a number of specular surfaces are thus found along the optical axis which can produce unwanted glare. Referring now to Fig. 3, the polarizer/filter carrier assembly 28 is shown in detail and comprises a frame member 32 having a base portion 34 and two leg portions 36 and 38 which extend upwardly from the base 34 and which have hinge members 40 and 42 connecting the vertical leg members 36 and 38 to slanted linkage members 44 and 46, which extend downwardly at approximately a forty-five degree angle and are further connected by hinges 48 and 50 to horizontal leg members 52 and 54. The entire frame member 32 is made of a plastic material and the hinge members 40, 42, 48 and 50 are of the so-called "living hinge" type which allow the flexing of the frame members at the respective hinge points as the filter carrier is manipulated within the housing, as will be described in more detail herein, in connection with Figs. 4 and 5. Mounted in the base portion 34 of the frame member 32 is a polarizing filter element 60 which is adapted to be positioned in and out of the viewing passage of the light reflected from the retina of the patient's eye. A second light polarizing filter element 62 is adapted to be moved in and out of the light transmission path from the light source 18. Obviously, these elements 60 and 62 may be of any desired filter material. In the preferred embodiment, they are linear polarizing filters in which the polarization axis of the element 60 is oriented at ninety degrees to the axis of the element 62 so that polarized light reflected from the trial lens, windows, and the cornea of the patient's eye will be canceled out by the element 60, but light reflected from the retina of the patient's eye will pass through the element 60 since the polarization of the diffused light from element 62 is lost, as it is reflected from the retina. Referring now to Fig. 4, the frame member 32 is shown with the light polarizing elements in the operative position, i.e., the element 62 being positioned in the light transmission path and the element 60 being positioned in the viewing path. The frame member 32 has a cross-section generally of a right-triangle with the short horizontal leg being the element 62 and the long vertical leg being the vertical uprights 36 and 38 and the element 60. It can be seen that the actuating knob 64 is in the upper position in Fig. 4 indicating that the frame member 32 is in the operative position locating the polarizer elements in the transmission and viewing paths. Fig. 5 shows the same structure with the actuating knob 64 in the lower position. The frame member 32 forms a right triangle cross-section, but the horizontal leg is now the long leg and the vertical leg is the short leg with the element 62 being retracted to the left in Fig. 5 to a position outside of the light transmission path 20 from the light source 18 and with the element 60 being retracted below the viewing path 24 for the physician's viewing of the light reflected from the patient's retina. Leg members 36, 38 and 52, 54 have laterally extending flanges 37, 39 and 53, 55, respectively, which are positioned in cooperating grooves 56, 57, 58 and 59, within the housing of the retinoscope head 12 so that the respective legs can only move within the respective tracks, i.e., the legs 36 and 38 can only move vertically, in Figs. 4 and 5 and the legs 52 and 54 can only move horizontally. Thus, as the rod 61 is moved by knob 64 up and down, the base portion 34 and the element 62 are moved vertically from the operative to inoperative position and vice versa. The hypotenuse, linkage members 44 and 46, of the right triangle push and pull the respective legs 52 and 54 into proper position, since the legs can only move linearly within their slots. There is thus provided a very simple and economical to manufacture mechanism for carrying a pair of polarizing light filter elements into and out of proper alignment for viewing of a patient's eye with a retinoscope. It is apparent from the foregoing that this movement can be accomplished with one finger on the knob 64. The two filters will either both be in place, or they both will be removed. While this invention has been explained with reference to the structure disclosed herein, it is not confined to the details set forth and this application is intended to cover any modifications and changes as may come within the scope of the following claims:

Claims: A retinoscope comprising: a main housing (12); a source (18) of illumination to direct a beam of light along a first light path (20); a beam-splitting reflector (22) in the main housing (12) to direct the beam of light along a second light path out a front of the housing (12) into an eye (91) of a patient, and light reflected from the eye of the patient to pass through said beam-splitting reflector (22) along a third light path (24) and out a viewing opening (26) on a rear side of the housing (12); and first and second polarizing filters (60, 62) carried on a carrier assembly (28) in said housing, the carrier assembly being arranged to movably position said polarizing filters in said third light path (24) and said first light path (20), respectively; CHARACTERIZED IN THAT said carrier assembly is in the form of a hinged frame (32) wherein a sliding back frame portion (34, 36, 38) slidably mounted in said housing carries said first filter (60) across said third light path (24); and in that said carrier assembly comprises: a lower frame portion (52, 54) which is slidably mounted in said housing and carries said second filter (62) across said first light path (20); linking strut members (44, 46) connected by hinge members (40, 42 and 48, 50) to said back frame portion (34, 36, 38) and said lower frame portion (52, 54), respectively, to mechanically synchronize the sliding motion of said back frame portion and lower frame portion; and an actuator member (64) operatively connected to said hinged frame (32) to selectively move said first and second polarizing filters (60, 62) into and out of their associated light paths. The retinoscope of claim 1 further characterized in that said back frame portion (34, 36, 38) and said lower frame portion (52, 54) each have lateral flanges (35, 37, 53, 55) which travel in respective pairs of linear grooves (56, 57, 58, 59) in said housing (12). The retinoscope of claim 1 further characterized in that said back frame portion (34, 36, 38), said lower frame member (52, 54), said strut members (44, 46) and said hinge members (40, 42, 48, 50) are unitarily formed as a unit assembly. The retinoscope of claim 1 further characterized in that said back frame portion has a base portion (34) extending laterally and leg members (36, 38) which extend distally from ends of said base portion with said hinge members (40, 42) joining said strut members (44, 46) to the leg members (36, 38) at their distal ends. The retinoscope of claim 4 further characterized in that said first polarizing filter (60) is mounted in the base portion (34).

Inventors: PERKINS DAVID G, PERKINS, DAVID G.
Applicants: WELCH ALLYN INC, WELCH ALLYN, INC.
Application year: 1992
Main classification: A61B3
IPC codes: A61B3