AU615782B2

AU615782B2 - Solar protective filter

Info

Publication number: AU615782B2
Application number: AU40050/89A
Authority: AU
Inventors: Wolfgang Grimm; Karl-Heinz Winter
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1988-08-20
Filing date: 1989-08-18
Publication date: 1991-10-10
Anticipated expiration: 2009-08-18
Also published as: CA1328181C; DK407589D0; DK407589A; EP0355672B1; DE3828382A1; JPH02103504A; DK171088B1; ATE105946T1; AU4005089A; EP0355672A2; DE58907680D1; EP0355672A3

Abstract

A filter, for protection against the sun, of improved contrast sensitivity has a spectral transmission (T lambda ) which for wavelengths ( lambda ) of the incident radiation in the range lambda < 350 nm </=1% and in the range 350< lambda <400 nm is less than 20%, and which in the range 400< lambda <500 nm reaches a value of 5-30% and thereafter, proceeding from the value for T500, increases linearly with the wavelength to its maximum value. This progression is achieved by coating or colouring the filter material. In this case, it is advantageous to provide a component of the coating or colouring so that the spectral transmission (T lambda ) outside the visible spectral range, i.e. for values lambda >780 nm, quickly reaches a value <1% again. <IMAGE>

Description

i i Our Ref: 289072

AUSTRALIA

Patents Act FORM COMPLETE SPECIFICATIO 1 5 8

(ORIGINAL)

Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: S Related Art: Applicant(s): Carl-Zeiss-Stiftung 7920 Heidenheim (Brenz) FEDERAL REPUBLIC OF GERMANY ARTHUR S. CAVE CO.

Patent Trade Mark Attornerys Level 10, 10 Barrack Street SYDNEY NSW 2000

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Address for Service: a Complete specification for the invention entitled "Solar protective filter".

The following statement is a full description of this invention, including the best method of performing it known to me:- 1 5020 Solar Protective Filter Field of the Invention The invention relates to a solar protective filter for protecting the eye against damaging and disturbing radiation.

Background of the Invention Such solar protective filters are utilized in solar Sprotective spectacles and serve to absorb as completely as possible radiation from the ultraviolet spectral range and to e limit to a minimum amount the danger of glare from rays from the visible spectral range. However, the filter characteristic must be so designed that the so-called r signal-light recognition is assured. According to the VI requirements of the ISO "Specification for afocal filters for daylight" this means that light from the green-yellow-red spectral range may be attenuated to at most 80%. Pursuant to a standardization (different in various parts of the world), the recognition of blue light (for example, of police vehicles and of rescue vehicles) must be 9 *possible.

20 Solar protective filters are made of glass or of a transparent plastic, for example, the plastic available under the trade designation CR 39. This material can be dyed as a mass, however, a coating determining the spectral transmission is for the most part applied to the base material. This coating can comprise thin vapor-deposited interference films.

The coating can however be produced for filters made of plastic also by dipping in a dye bath. Dye molecules then lodge in the layers of the plastic near the surface. The spectral transmission of such protective filters made of plastic is then determined solely by the spectral absorption la i Il~"-C of the applied dye coating.

The coefficient of absorption or transmission for solar protective filters is determined by means of convolution with the photopic solar response curve (Vx curve) which is determined by standardization. As a practical matter, such filters having an absorption of 85%, 65% to approximately are available.

The solar protective filters known up to now essentially have a transmission TX of 0 for radiation of the wavelength A 350 nm. Thereafter, the transmission increases quasi linearly with increasing wavelength and remains approximately constant at a maximum value in the range 450 A 780 nm. In general, the transmission also still remains constant for A 780 nm up to more than 800 nm 15 and only again becomes less thereafter, mostly caused by the absorption of the filter material in the IR-range.

It has been shown that these known solar protective spectacles negatively influence the contrast sensitivity especially at low luminance and that under specific light 20 conditions, for example for hazy weather or for indirect illumination, a disturbing blurred luminance occurs. This disadvantage has a negative effect on the acceptance of such protective spectacles.

Summary of the Invention It is an object of the invention to provide a solar protective filter to protect the eye against damaging and disturbing radiation which is characterized by a greatly improved contrast sensitivity. This increase of the contrast sensitivity should, above all, have an effect for average luminance and for unfavorable lighting conditions.

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According to a feature of the invention, this object is achieved by means of a solar protective filter whose spectral distribution of the transmission (TA) is configured in dependence upon the wavelength of the incident radiation according to the following: T 5 1% in the range A 350 nm; TA 20% in the range 350 A 400 nm; 5 TA 30% in the range 400 A 500 nm; and, T increasing approximately linearly with A in the range 10 of 500 A 780 nm starting from the value for T500.

As can be recognized from these features, the transmission for the shortwave component of the radiation is significantly reduced in the solar protective filter according to the invention. In this way, and in a surprising manner, a 15 significant increase of the contrast sensitivity is obtained and an improved acceptance and compatibility of the solar protective filters result. The increase of the contrast sensitivity (as investigations in connection with the invention have shown) can be accounted for by the fact that 20 the ocular media scatter in the shortwave range of the light and that this scatter leads to glare phenomenon and disturbances. An especially significant attenuation of this solar range has a positive effect on the contrast sensitivity.

For shortwave light, an interaction furthermore occurs between the photopic system and the scotopic system of the eye which especially for medium and low luminance leads to a deterioration of the contrast sensitivity.

With the solar protective filter according to the invention, the contrast sensitivity with respect to known filters and especially also the contrast sensitivity with 3 medium luminance is improved.

A solar protective filter configured according to the invention has a red-brown tint according to a preferred embodiment. Even when such a filter is configured with an absorption of 80 to 85% determined in the usual manner by convolution with the V curve, it has nonetheless the subjective effect for the user as does a neutral grey filter having an absorption of 50%. From this it is apparent that a solar protective filter configured pursuant to the invention is very comfortable to wear for the user. The solar protective filter according to the invention falsifies the colors for the user by only a small amount and fulfills all requirements with reference to the signal-light recognition *according to ISO "Specification for afocal filters for o o 15 daylight", test pursuant to method B.

In a solar protective filter configured according to another feature of the invention, the shortwave component of the light is still further reduced in that the transmission for wavelengths up to 380 nm is reduced to values 1%.

20 Another advantageous embodiment of the solar protective filter according to the invention provides that the transmission ior wavelengths above the visible range, that is for A 780 nm, is reduced to values In this way, the eye is protected also against radiation from the shortwave infrared range. In addition, materials are disclosed for the solar protective filter as is the nature of the configuration of the spectral transmission.

Brief Description of the Drawings The invention will now be described with reference to the drawings wherein: 4 1i' FIG. 1 shows the spectral transmission of a solar protective filter according to the invention and configured pursuant to a first embodiment; FIG. 2 shows the spectral transmission for a second embodiment; and, I FIG. 3 shows the international spectral brightness curve curve).

Description of the Preferred Embodiments of the Invention In the embodiment of FIG. 1, the solar protective filter has a transmission 1% for wavelengths A 380 nm, that is it se absorbs the UV-radiation lying in this range almost completely.

Ki Above A 380 nm and up to approximately A 400 nm, the Sii* spectral transmission (TA) increases rapidly to a value of i 000 approximately 15%. This value remains approximately constant 15 up to A 500 nm so that the recognition for signal lights according to ISO "Specification for afocal filters for daylight", test according to method B, is guaranteed.

i Above A 500 nm, the transmission increases to its highest value starting from the value for T preferably linearly S0500 S with the wavelength The linear increase shown is idealized and an actual linear increase can hardly be 0 00 achieved. The increase should however be as linear as "i possible in order to prevent color falsifications by means of the solar protective filter.

The maximum value of the transmission TX is attained at, for example, A 700 nm. This value remains approximately constant up to the end of the visible range at A 780 nm and then drops to values 1% up to approximately A 820 nm.

Such a course of the spectral transmission can be obtained for solar protective filters of glass by coating with p;u 00*0 0000 oooo oooo 00 0 oO o 0 0000 0000 0o 0000 0000 o o oooo 0- *o00 00oo 0 0 0 0 00 thin interference coatings. In this connection, it is possible to apply the coatings which fulfill different tasks to both sides of the solar protective filter. Such coatings can today be calculable with respect to their composition so that a predetermined course of the T curve is obtained and the production of such coatings is possible in computer-controlled vaporization units.

Protective filters of plastic can also be coated in this manner. However, for filters made of plastic, it is more economical to obtain the spectral transmission by dipping into an appropriate dye bath. The dye molecules become lodged in the layers of the filter close to the surface. It is also possible to control the dye process so that the filter is dyed throughout. In this way, the UV-stability of the filter is 15 improved.

The suitable composition of the dye bath can be determined by means of computation or experimentation with so-called dispersion dye materials being used.

A solar protective filter of FIG. 1 has an absorption of 20 approximately 65 to 85%. This absorption is in a known manner determined through convolution with the V curve shown in FIG. 3. Nonetheless, this protective filter acts subjectively as a neutral grey filter with 50% absorption for the wearer thereof. The wearer enjoys a very good contrast sensitivity even for mid and low luminance without the occurrence of a disturbing color falsification of the observed scene.

In the embodiment of FIG. 2, the transmission is reduced to values 1% for wavelengths X 400 nm and then increases and reaches a value of approximately 12% in the range 410 A 500 nm. Thereafter, the spectral transmission 6 0 0 increases with the wavelength substantially linearly and reaches its maximum value at approximately A 780 nm which it maintains also for A 780 nm. Above A 800 nm, that is in the IR-range, the transmission drops again because of reduced IR-transmission of the filter material.

The spectral transmission curve shown in FIGS. 1 and 2 are only examples which serve to show the principle course of j this curve.

It is understood that the foregoing description is that S 10 of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as i defined in the appended claims.

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Claims

1. A solar protective filter for protecting the eye against damaging and disturbing radiation, the solar protective filter comprising: a spectral distribution of the transmission T in dependence upon the wavelength A of the incident radiation as follows: T 6 1% in the range A 350 nm; T 20% in the range 350 X 400 nm; 5 TX 30% in the range 400 X 500 nm; and, T increasing approximately linearly with A in the range 10 of 500 X 780 nm starting from the value for T 5 00 500 .I

2. The solar protective filter of claim 1, comprising a change of range in the component in and as follows: T X 1% in the range A 380 nm; and, S(b) TA 20% in the range 380 X 400 nm. 0 a a

3. The solar protective filter of claims 1, wherein: the transmission T drops to the value 1% in the range 780 A 850 nm. h*

4. The solar protective filter of claim 1, wherein the filter is made of transparent material which is dyed as a mass.

The solar protective filter of claim 1, wherein the filter comprises transparent material having a spectral transmission determined by coatings applied thereto.

6. The solar protective filter of claim 4, said material 8 8Imml mi m i e ll am i 0131h:DW 4- 9 being glass.

7. The solar protective filter of claim 4, said material being transparent plastic.

8. The solar protective filter oi claim 1, said filter comprising transparent plastic having a spectral transmission T, which is determined by introducing dye molecules into the layers near the surface.

9. The solar protective filter of claim 1, wherein the transmission T 3% is determined through convolution with the spectral brightness response characteristic (V-curve). 0000 0 0 S. S *SSS 0 0000 DATED this 26th day of June, 1991. CARL-ZEISS-STIFTUNG By Its Patent Attorneys ARTHUR S. CAVE CO. 5 S L -Q al~~T/