BACKGROUND OF THE INVENTION Optical instruments often make use of opaque lens covers to protect against scratches and foreign matter, such as dust, liquids, body oils or cosmetics. However, inasmuch as such lens covers do not permit viewing, neutral density filters custom fitted to engage the lens must therefore be used as protective covers for when the instrument is in use. Such filters are made of high quality optical glass so as to not degrade the optical qualities of the instrument.

Disadvantageously, these neutral density filters also become exposed to foreign matter, therefore themselves requiring periodical cleaning, which is both labor intensive and costly. While discarding the filters is an option, it is also prohibitively expensive for most users.

To reduce cost, it is possible to fabricate the filters from molded plastic. However, this is not preferable because of the optical distortion typically caused by the induced stress imparted from the molding process itself.

Also, many optical instruments, such as those used in the medical field, including microscopes and ophthalmic instruments, do not have provisions to be fitted with neutral density filters or hoods. When the lens becomes dirty, it will often take skilled technicians more than

thirty (30) minutes to clean the lens in these latter instruments, adding to the maintenance expense. In addition, there are serious concerns regarding the spread of contagious disease. Since the lens comes into close contact with patients, the possible risk of infection from instrument to patient, or cross-contamination from patient to patient is of major concern.

Accordingly, it is desirable in the art to provide for a lens cover without the associated problems of the prior art.

SUMMARY OF THE INVENTION The present invention is a disposable, transparent lens cover for protecting the lens of an optical instrument from scratches and foreign matter, such as dust, liquids, body oils, or cosmetics. Advantageously, this permits optimum viewing through the lens cover while the instrument is in use, and without the associated problems of the prior art discussed herein above.

In one preferred embodiment, the lens cover comprises a thin, transparent membrane bonded taut to a carrier frame made preferably of plastic or metal. The membrane is made of a relatively high grade, optically transparent material, such as MylarX, having a thickness of approximately 0.0001 to 0.020 inches. The spectral transmissivity of the membrane is judiciously tailored to the specific application. That is, the membrane is substantially transparent to the radiation spectrum or wavelength (s) of interest.

Since the membrane is thin, there is a minimal amount

of refraction. Hence, little, if any, degradation in the imaging quality exists even if there are imperfections in the membrane. In some applications, it will also be desirable to coat the membrane with an anti-static coating to prevent dust from being attracted to the membrane.

The carrier frame-made of plastic, metal and the like-may have an annular disc shape or may be made in a variety of shapes and sizes to meet the specific geometry of the application. Of course, the shape and size of the carrier frame is judiciously chosen to permit unobscured viewing.

Adhesives, solvent bonding or ultrasonic welding, among others, may be used to attach the membrane to the carrier frame which may be formed into any desired shape through stamping, injection molding, machining or any other suitable technique known to one skilled in the art.

Preferably, a pressure sensitive adhesive is used to attach the lens cover to the lens housing of the optical instrument. Alternatively, the carrier frame may be constructed to have an outside diameter sized to achieve a detachable friction fit with the lens housing. In this latter instance, the carrier frame may be optionally provided with a pull tab such that it can be easily grasped to remove the lens cover from the lens housing. Or, the lens cover may be provided with suitable threads around the periphery of the carrier frame. Corresponding mating threads within the lens housing allows the lens cover to be attached to the instrument.

Furthermore, the carrier frame may be adapted with

side walls so that the lens cover constitutes a lens cap.

A variety of other means of removably mounting the lens cover to the lens housing may be used to accommodate many different optical instruments and thus allow those instruments to be readily retrofitted with the lens cover of the present invention. For example, the lens cover may be removably mounted through the use of hook and loop fasteners, such as Velcro@, mechanical fasteners, or any other friction fit or coupling means known in the art.

In another alternative embodiment, the lens cover may be adapted for use with an instrument cover, such as a surgical drape and the like. The lens cover may be either permanently or removably attached to the instrument cover.

In order to affix the lens cover permanently to the instrument cover, pressure sensitive adhesive or other suitable bonding methods may be used. Alternatively, hook and loop fasteners, such as Velcro@ strips, may be applied to the area adjacent to the viewing aperture. In this latter case, a second set of Velcro@ strips may be affixed to the carrier frame of the lens cover and positioned to mate with the first set of Velcro@ strips. In this manner, the lens cover may be readily removed and replaced should it become obscured by foreign matter. A draw string, hook and loop fastener, or pressure sensitive adhesive can be used as a closure means for the instrument cover. Also, other enclosed apertures may be provided to allow access to the controls of the optical instrument.

BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the present invention will become more readily apparent from the following detailed description of the invention in which like

elements are labeled similarly and in which: Fig. 1 is a perspective view of a camera utilizing the lens cover of the present invention; Fig. 2 is a cross sectional view taken along line 2-2 of Fig. 1; Fig. 3 is a front view of the lens cover of the present invention; Fig. 4 depicts illustrative plots of the transmissivity of MylarO; Fig. 5 is perspective view of another embodiment of the lens cover of the present invention; Figs. 6-7 are perspective views of still other embodiments of the lens cover of the present invention adapted to enclose an optical instrument; and Fig. 8 is a partial bottom or side view of the instrument cover of Figs. 6 and 7, respectively.

DETAILED DESCRIPTION The present invention is a disposable lens cover for protecting the lens of an optical instrument from foreign matter, which lens cover is made from a thin, transparent membrane mounted on a carrier frame Importantly, this permits viewing through the lens cover while the instrument is in use, without the associated problems of the prior art.

Without any loss of generality or applicability for the principles of the invention, the embodiments below are directed to a camera or a microscope. It should, however, be clearly understood that the present invention is equally applicable to telescopes, binoculars, ophthalmic instruments, and in general, optical instruments having a viewing or objective lens.

Referring to Figs. 1 and 2, there is shown an exemplary embodiment of a camera 100 comprising a camera body 110, and a lens housing 120 having at the front end therein a lens 130. Lens 130 is protected by a removable lens cover 140 of the present invention which covers the front surface of the lens. A front view of lens cover 140 is shown in Fig. 3. It should be clearly understood that lens cover 140 protects lens 130 from dust, water, scratches, and fingerprints, among other things, while permitting viewing through the lens. Lens 130 is of the conventional type and may further be operatively coupled to a shutter and/or focusing mechanism in a manner well known in the art. For the sake of clarity, neither the shutter nor the focusing mechanism is depicted.

Lens cover 140 comprises a thin, transparent membrane 150 bonded taut over a carrier frame 160, made preferably of plastic or metal. Membrane 150 is preferably made of a high grade, optically transparent material, such as plastic and, more preferably, type D Mylar@ sold by Dupont, which has light transmission properties very similar to window glass. A thickness of approximately 0.0001 to 0.020 inches is well suited for most applications. Although of relatively high optical quality, MylarO is inexpensive compared to standard optical quality materials, such as

glass. Alternatively, the thin membrane may be made of any other suitable high grade, optical quality, polymer material. Shown in Fig. 4 are illustrative plots of the spectral transmissivity of various types of MylarO sheets.

It should be clearly understood that the spectral transmissivity of the thin membrane may be judiciously tailored to the specific application. That is, thin membrane 150 is substantially transparent to the radiation spectrum or wavelength (s) of interest. It is contemplated that coatings may be deposited on the membrane to tailor the transmissivity of the lens cover. For example, a suitable coating can be applied to membrane 150 to effect visible or infrared imaging. However, it is contemplated that for most applications, thin membrane 150 should be transparent to visible radiation in the range of about 400 -760 nm. Infrared radiation, however, is particularly well suited for use in ophthalmology and certain other types of imaging and photography.

As shown, carrier frame 160 has an annular disc shape, but may be made in a variety of shapes and sizes to match the specific geometry of the optical instrument. Of course, the shape and size of carrier frame 160 is judiciously chosen to permit unobscured viewing through lens 130 and membrane 150.

Depending upon the type of lens used, lens cover 140 can have a diameter of over 200 mm, such as for a telescope, with membrane 150 sized suitably to cover lens 130. However, thin membrane 150 may be made in any desired diameter. Since the membrane is thin, there is a minimal amount of refraction. Hence, little, if any, degradation

in the imaging quality exists, including those due to aberrations or"ghost images,"even if there are imperfections in the membrane. Preferably, membrane 150 should be of sufficient thickness to be suitable for use under conditions of inclement weather. In some applications, it will be desirable to optically coat membrane 150 with an anti-reflection coating. Moreover, it may also be desirable to coat the membrane with an anti- static coating to prevent dust from being attracted to the membrane.

Adhesives, solvent bonding, ultrasonic welding or mechanical fasteners, for example, may be used to attach membrane 150 to carrier frame 160. It is contemplated that carrier frame 160 may be fabricated in any desired shape through stamping, injection molding, machining or any other suitable technique known to one skilled in the art. As shown in Fig. 3, lens cover 140 is preferably provided with pressure sensitive adhesive 165 disposed around the periphery of carrier frame 160 to attach the lens cover to a portion 170 of lens housing 120.

Alternatively, carrier frame 160 may be constructed to have a detachable friction fit inside lens housing 120.

Optionally, carrier frame 160 may be provided with a pull tab 175 which extends outwardly from the edge of the carrier frame such that it can be easily grasped to remove the lens cover. Also, a retaining ring 155 of suitable size may be used to firmly hold lens cover 140 in position.

In this latter instance, retaining ring 155 may be provided with threads so as to mate with a corresponding portion of lens housing 120.

In another alternative embodiment, lens cover 140 may be provided with suitable threads around the periphery of the carrier frame. Corresponding threads within, for example, the front end of lens housing 120 allows lens cover 140 to be screwed thereto in a manner similar to conventional neutral density filters found in 35 mm cameras.

In still yet another alternative embodiment, carrier frame 160 may be adapted with side walls 180 such that the lens cover constitutes a lens cap 140', as illustrated in Fig. 5. In this latter embodiment, lens cap 140'is fitted over lens housing 120 to cover the front surface of the lens. In this manner, lens cap 140'may be readily removed and replaced in the event that the lens cover becomes clouded or obscured by foreign matter. Of course, it is contemplated that the circular region defined by side walls 180 may be adjustable, either manually or automatically, to fit different size optical instruments.

It is contemplated that a variety of other means of removably mounting lens cover 140 to the lens housing may be used to accommodate many different optical instruments and thus allow those instruments to be readily retrofitted with the lens cover of the present invention. For example, lens cover 140 may be removably mounted through the use of hook and loop fasteners, such as Velcro@, mechanical fasteners, or any other friction fit or coupling means known in the art. As indicated, Velcro@ strips may be appropriately applied to the optical instrument itself near or adjacent to the viewing lens, such as area 170.

Similarly, Velcro@ strips may be affixed to the periphery of carrier frame 160 and adapted to mate with Velcro

strips on the optical instrument. Likewise, carrier frame 160 may be provided with pull tab 175 to facilitate removal.

Those skilled in the art will readily note that the lens cover of the present invention further offers several advantages over prior art. Inasmuch as the lens cover of the present invention is relatively inexpensive, it may be readily discarded and replaced when dirty or contaminated.

This eliminates costly cleaning or, in certain applications, the spread of infectious diseases from patient to patient. Also, the present lens cover even if damaged does not pose a safety hazard since it is not made of glass and cannot shatter the way a standard neutral density glass filter can.

In another alternative preferred embodiment, the present invention is likewise a disposable lens cover used to protect the lens from foreign matter. The lens cover, however, is principally adapted for use with an instrument cover, such as a surgical drape or camera"bag."Fig. 6 illustrates an instrument cover 200 mounted on an operating room microscope 210 having a lens housing 220 containing a lens 230. Alternatively, shown in Fig. 7 is instrument cover 200 adapted to enclose a camera 100'having a lens housing 120'containing a lens 130'. Instrument cover 200 is made of a flexible, resilient material, such as plastic, and in the form of a specially configured shape so as to substantially enclose the optical instrument. A closure area 260, consisting of a draw string, pressure sensitive adhesive, hook and loop fastener, or other suitable means may be used to close the instrument cover, with the controls operated through the plastic, through openings in

the plastic or through openings fitted with smaller appended"bags." As shown in Fig. 8, a bottom or side portion 240 of instrument cover 200 is provided with an aperture having bonded thereto lens cover 140 so as to permit viewing through lens 130'or 230. Lens cover 140 may be attached to bottom or side portion 240 of instrument cover 200 with adhesive, solvent bonding, ultrasonic welding or some other method known in the art. Furthermore, pressure sensitive adhesive may, for example, be used to attach lens cover 140 to lens housing 120'or 220, with the carrier frame thereof made in different shapes and sizes to facilitate attachment to different types of optical instruments.

In certain medical applications, lens cover 140 and/or instrument cover 200 is provided sterilized in a sealed package. When used, the lens cover and/or instrument cover is removed from the sterile package and attached in the manner described herein above. After use, the lens cover and/or instrument cover is removed or discarded, preventing the spread of contagious disease.

It should be understood that the embodiments herein are merely illustrative of the principles of the invention.

Various modifications may be made by those skilled in the art which will embody the principles of the invention and fall within the spirit and the scope thereof. Accordingly, it should be clearly understood that the present invention is equally applicable to video cameras, telescopes, binoculars, ophthalmic instruments and, in general, optical instruments.