Optical: systems and elements – Absorption filter – Neutral or graded density
Reexamination Certificate
2001-03-30
2004-01-06
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Absorption filter
Neutral or graded density
C359S885000, C359S361000, C359S601000, C359S603000, C359S614000, C427S166000, C296S097600, C296S097700
Reexamination Certificate
active
06674587
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of deposition of an absorbing material upon a plastic/glass substrate by vacuum coating at an angle of inclination between 5° to 30° and using a mask on the evaporation source to produce a graded film material. More particularly, the present invention relates to a method for the preparation of graded density absorbing film useful as an antiglare optical device for protecting the eyes by reducing the glare by absorbing the light intensity falling upon it in a non-uniform fashion.
BACKGROUND AND PRIOR ART TO THE INVENTION
The necessity of Night driving filter was felt as in the night time It becomes very difficult to drive on the high ways due to the radiations falling on the eye of incoming vehicles on the driver's eye. The excessive radiations falling on the eye makes the eye pupil to close resulting in the darkness of the view in front of the driver and accidents occur. Also the UV and IR content of the radiations make the eyes prone to cataract and other diseases. This made it essential to have device which removes this excessive radiations.
During night driving, the headlights of the vehicles approaching in the opposite direction emit radiations in the wavelength of 320-400 nm and 750-1400 nm. These radiations blind the driver due to which a number of accidents occur in the night. The frequent blinding glare not only makes the driving difficult, but also impairs the vision. The impairment of the vision occurs due to development of cataract in the crystalline lens by the UV radiation and also retinal deterioration caused due to the thermal effects of IR radiation in the long run.
To reduce the blinding effect produced by an approaching vehicle, many plastic goggles have been manufactured. A reference may be made to the night driving plastic goggles manufactured by M/s Proview Optical Corporation, Taiwan wherein yellow colored plastic is used whose spectral profile is shown in FIG.
1
. The transmission table is given as Table 2. The drawbacks with these goggles as inferred from the spectral profile are as follows:
1. It reduces the transmission in the wavelength region 300-540 nm over the entire surface area thereby it also suppresses visualisation of the road on the left side.
2. It does not completely block the blinding glare entering the eyes fro the right had side of the windshield as it is transmitting more than 70% of the radiation in the wavelength region 550-750 nm.
3. Due to selective transmission in the visible region, i.e., having absorption in the blue region, it distorts the color of the objects which might effect the recognition of the person wearing blue color clothes.
Another reference may be made to St. Martin sunglasses manufactured and distributed by M/s Thukral Optics, New Delhi wherein spectacle glasses are claimed to be used as anti-radiation for filtering out UV and IR radiation from computer monitors and TV screen as well as for night driving to prevent blind spot. However, the literature of the product does not give any spectral curve or technical clarifications justifying the use of spectacle glasses for night driving.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a method for preparing a graded density absorbing film useful as an antiglare optical device.
Another object of the present invention is to provide a method for the deposition of absorbing film material upon plastic/glass substrate by vacuum coating on a inclined substrate with angel of inclination between 5° to 30° and using a mask on the evaporation source.
Still another object of the present invention is to provide a method for the preparation of an antiglare optical device for protecting the eyes of the automobile driver during night driving.
Yet another object of the present invention is to provide a method for the preparation of an antiglare device to protect the automobile drivers eye from radiation in the wavelength range 320-400 nm and 750-1400 nm.
One more object of the present invention is to prevent impairment of vision due to development of cataract in the crystalline lens by the UV radiation and also retinal deterioration caused due to the thermal effects of IR radiation in the long run.
SUMMARY OF THE INVENTION
The present invention relates to a method of deposition of an absorbing material upon a plastic/glass substrate by vacuum coating at an angle of inclination between 5° to 30° and using a mask on the evaporation source to produce a graded film material. More particularly, the present invention relates to a method for the preparation of graded density absorbing film useful as an antiglare optical device for protecting the eyes by reducing the glare by absorbing the light intensity falling upon it on a non-uniform fashion.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention provides a method of manufacturing a coated substrate to be used as but not limited to automobile anti-glare filter, said method comprising providing a transparent substrate made of glass or synthetic material, coating a gradient density absorbing film on one side of the substrate kept at an inclined position with an angle of inclination varying between 5° to 30° with respect to a evaporation source, masking the evaporation source during the deposition of the absorbing material and coating the substrate with an Anti Reflection (AR) material on both surfaces thereby obtaining the anti glare optical device.
In an embodiment of the present invention, the thickness of the first coating is determined in terms of transmission of the gradient density absorbing film.
In another embodiment of the present invention, the deposition of the first coating is done so as to obtain the following transmission data on the substrate:
Distance from RHS
% Transmission at 550 nm
50 mm
45 to 50
100 mm
30 to 35
200 mm
50 to 60
300 mm
75 to 80
In another embodiment of the present invention, the evaporation source is a tungsten spiral filament.
In still another embodiment of the present invention, the evaporation is done in a vacuum coating plant maintained at 2×10
−5
mb to 1×10
−6
mb.
In yet another embodiment of the present invention, the absorbing material is selected from the group comprising of Inconel, Rhodium, Palladium, Nichrome, chromium and mixtures mixtures thereof.
In one more embodiment of the present invention, the AR material is selected from the group comprising of Magnesium fluoride, Silicon dioxide and mixtures thereof.
In one another embodiment of the present invention, the synthetic material is polycarbonate plastic.
In an embodiment of the present invention, after the absorbing material is coated, the chamber is brought to normal atmospheric pressure and the coated substrate is placed horizontal w.r.t. evaporating source, the chamber is evacuated to get the same vacuum and the AR material is evaporated on both sides.
The present invention further provides a method of manufacturing an improved anti glare optical device for automobiles, said method comprising: providing a transparent substrate made of glass or synthetic material, coating a gradient density absorbing film on one side of the substrate kept at an inclined position with an angle of inclination varying between 5° to 30° with respect to a evaporation source, masking the evaporation source during the deposition of the absorbing material and coating the substrate with Anti Reflection material on both surfaces thereby obtaining the anti glare optical device.
In an embodiment of the present invention, the thickness of the first coating is determined in terms of transmission of the gradient density absorbing film.
In another embodiment of the present invention, the deposition of the first coating is done so as to obtain the following transmission data on the substrate:
Distance from RHS
% Transmission at 550 nm
50 mm
45 to 50
100 mm
30 to 35
200 mm
50 to 60
300 mm
75 to 80
In still another embodiment of the present invention, the evaporation source is a tungsten spiral filament.
In yet anothe
Chhabra Deep Singh
Dodd Dharambir Singh
Rao Parinam Krisna
Sharma Bipin Dev
Sharma Sanjay
Boutsikaris Leo
Council of Scientific Research
Harness & Dickey & Pierce P.L.C.
Nguyen Thong
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