GB2521875A

GB2521875A - Signs

Info

Publication number: GB2521875A
Application number: GB1400236.4A
Authority: GB
Inventors: Sean O'kell
Original assignee: Saf T Glo Ltd
Current assignee: Saf T Glo Ltd
Priority date: 2014-01-07
Filing date: 2014-01-07
Publication date: 2015-07-08
Also published as: GB201400236D0

Abstract

A sign 1 for use as an aircraft emergency exit sign is configured to be visible to aircrew using night vision goggles. The sign includes an indicia layer 3, a filter layer over the indicia layer and a substrate layer 7. The indicia layer comprises a photoluminescent material, in particular a phosphorescent material. The photoluminescent material may emit light over a range of wavelengths including visible and near infrared parts of the spectrum. The filter layer 5 is arranged to selectively filter electromagnetic radiation from the indicia layer, in particular to reduce emission in the near infra-red part of the spectrum and to block emission in the infrared part of the spectrum. The light from the sign is visible to the unaided eye and also to aircrew wearing night vision goggles without causing flaring or blooming.

Description

This invention relates to signs and markers for aircraft. In particular, this invention relates to night vision compatibk emergency exit signs and route markers for use in military airc raft.

S Conventionally, in commercial aircraft, the location of emergency exits and escape routes that lead to the emergency exits are indicated by photoluminescent signs and markers that emit visible radiation. However, in military aircraft, it is well known for airerew to use night vision systems for example night vision goggles, that arc sensitive to non-visibk parts of the electromagnetic spectrum. These systems improve the night vision of the air crew but photoluminescent signs and markers are either not visible through night vision systems or else are too bright when viewed through night vision systems and cause flaring. This can lead to a reduction in effectiveness of the night vision system, as tess bright objects are masked and the sensitivity of the system is reduced to counteract the flaring.

The present invention has been made from a consideration of the foregoing and seeks to provide signs and markers that are cornpatibk with night vision systems.

According to a first aspect of the invention there is provided a sign or marker for use in an aircraft emergency exit system, tile sign or marker comprising: an indicia layer; and a filter covering the indicia layer arranged to selectively fflter emission of electromagnetic radiation from thc indicia layer.

By the first aspect of the invention, signs and markers are provided that can be used in conjunction with off-the-shelf night vision systems.

The indicia layer may comprise a photoluminescent material.

The phot&uminescent material may emit radiation in the near infra-red part of the electromagnetic spectrum.

The photoluminescent material may emit radiation of wavelength up to 950nm.

The lifter may be arranged such that emission in the near infra-red part of the electromagnetic spectrum is controlled.

The filter may scale down near infra-red emission from the indicia layer and effectively block emission in the infra-red part of the electromagnetic spectrum.

The filter may reduce near infra-red emission from the indicia layer by an order of magnitude or more.

The fUter may reduce emission of wavelength greater than 600nm, The filter may block emission of wavclength greatcr than 950nm, The filter may block emission of wavelength greater than 800nm.

The near infra-red emission from the sign or marker may be at a level that is visible through night vision systems. Prefcrably, thc infra-red cmission will be visible without causing flaring or blooming.

The radiance of the photoluminescent material may, scaled to 15 fL, may be less than W/cm2 cm nm.

The radiance of the photoluminescent material may, scaled to 15 fL, may be greater than 47 W/cm2 cm nm.

The radiance of the photoluminescent material may be between 50 W/cm2 cm nm and 150 W/cm2 cm nm. Alternatively, the radiance may be between 47 W/em2 em nm and W/em2 em nm.

The photoluminescent material may emit radiation over a range of wavelengths.

The photoluminescent materia' may emit radiation in the visible part of the electromagnetic spectrum.

The maximum level of radiance from the photohiminescent material may be in the visible part of the dectromagnetic spectrum, The filter may be arranged to let at least some of the emission in the visible part of the spectrum pass.

The photouniinescent material may be a phosphorescent materiaL The photoluminescent material may comprise a dopant, The photolumineseent material may comprise Strontium Aluminate.

The sign or marker may be comprised in a frame substantially or wholly surrounding the edges of the filter and indicia layer.

The indicia layer may be arranged to provide markings, direction or indications of emergency exits or emergency routes.

IS

When the indicia layer comprises a photoluminescent material. the photohiminescent material may be arranged to provide the markings, directions or indications.

The indicia layer may be arranged to emit radiation in a first direction and a second direction.

Alternatively, the sign or marker may comprise a first indicia layer, arranged to emit radiation in a first direction and a second indicia layer arranged to emit radiation in a second direction.

The sign or marker may further comprise a first filter arranged to filter radiation emitted in the first direction and a second filter arranged to filter radiation emitted in the second direction.

The indicia ayer may be provided on a substrate.

The signs or markers may be for use in a night vision goggle compatible system.

According to a second aspect of the invention, there is provided a night vision system for an aircraft comprising at least one sign or marker according to a first aspect of the invention.

S By the second aspect of the invention, emergency exits signs and pathways may be visible to aircrew using night vision goggles.

The system may further comprise night vision goggles for use by aircrcw of the aircraft.

The goggles may include an objective filter.

The objective filter may effectively block radiation in the visible region of the electromagnetic spectrum and allow radiation in the near infra-red and infra-red part of the electromagnetic spectrum to pass.

The objective filter may block radiation of wavelength less than 600nm.

The objective filter may allow radiation of wavelength greater than 700nm to pass.

According to a third aspect of the invention, there is provided an aircraft comprising a night vision system according to the second aspect of the invention.

By the third aspect of the invention, an aircraft is provided with night vision compatible emergency exits signs and routes.

The signs and markers may be arranged in the aircraft to mark the emergency exits and direct the aircrew to said exits in an emergency.

According to a fourth aspect of the invention, there is provided a method of providing night vision system compatible emergency exit signs and/or markers, the method comprising: providing photoluminescent signs and/or markers that emit radiation in the near infra red part of the electromagnetic spectrum; and filtering the emission from the signs and/or markers such that emission in the near infra-red part of the electromagnetic spectrum is controlled.

By the fourth aspect of the invention. aircrew using night vision systems can see the emergency exits signs and/or markers.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows an exploded view of the layers of a sign or marker embodying the invention; Figure 2 shows the emission from a photoluminescent materiaU Figure 3 shows the wavelength sensitivity of the components of a night vision system; and Figure 4 shows a night vision system embodying the invention.

The human eye is sensitive to electromagnetic radiation of wavelengths between approximately 400nm and 7SOnm, Night vision systems, such as night vision goggles, are well known in the art and detect and display longer wavelengths, such as the near infra-red part of the spectrum (wavelengths longer than 75 Onm).

Night vision systems include detectors that are sensitive to a range of wavelengths of radiation, including the wavelengths that are of interest. If a high intensity of radiation is detected at a particular wavelength, the overall resolution of the system can be reduced. Therefore. night visions systems typically include filters to stop radiation that is not of interest reaching the detector.

In one example, a night vision system is sensitive to radiation with wavelength between approximately SOOnm and 950nm. In this system, the filter blocks radiation with wavelength shorter than GSOnm.

Figure 3 shows the sensitivity 304 of the human eye, the sensitivity 306 of an example night vision system and the sensitivity of the filter on the night vision system 308.

Referring to Figure 1, there is shown a sign or marker I The sign or marker I S comprises an indicia layer 3, a ffiter ayer 5, and a substrate ayer 7.

The indicia layer 3 has regions of a photoluminescent material 11 on one face, the photolumincsccnt material 11 providing markings 9 on thc sign or marker 1. Thc photouminescent material II appears a different co'our to the rest of the indicia layer 3, For example, the markings 9 may be letters or words, such as "EMERGENCY EXIT", arrows or other symbols, A photolumincsccnt matcrial 11 is a matcrial that cmits radiation in rcsponsc to an excitation, for example irradiation. In the current examp'e. the photoluniinescent material II is a phosphorescent material. This is a material that emits radiation for a sustaincd pcriod of time (over several years) in response to excitation.

Thc photolumincsccnt matcrial 11 cmits radiation ovcr a range of wavelcngths, including at least part of the near infra-red region of the spectrum (approximately 7SOnm to approximatcly l400nm) and at least part of thc visiblc region of the spectrum (approximately 400nm to approximately 7SOnm).

One example of a photoluminescent material 11 that can be used is doped strontium aluminate, such as SAFTGLO BGL 300 or SAFTGLO SG 110, both produced by STG Aerospace. Figure 2 shows an example of the emission from doped strontium aluminate.

The fUter layer 5 filters radiation emitted from the indicia ayer 3, The filter layer 5 allows radiation below a first wavelength to pass substantially unaffected and substantially blocks radiation above a second wavelength. Between the first and second wavelength, filter ayer 5 allows emitted radiation to pass, but reduces the intensity of the emitted radiation.

Generally, the filter layer 5 allows radiation of visible wavelengths to pass, attenuates near infra-red radiation and blocks infra-red radiation.

Figure 3 shows one example of the sensitivity 302 of the filter layer 5, The filter layer 5 and the filter in night vision systems co-operate so that there is a range of wavelengths where the sign may be effectively viewed throlLgh night vision systems. Above this range, the radiation is blocked by the filter layer 5. Below this range, radiation is b'ocked by the filter on the night vision system, so the sign or marker 1 is also visible with the naked eye, In the current example, the filter layer 5 allows radiation below 550nm to pass, blocks radiation above 800nm and attenuates radiation between SSOnm and 800nrn to reduce the intensity. The filter of the night vision system then blocks radiation below 650nm The substrate layer 7 provides strengths and rigidity to the sign or marker I. The layers may be secured together in any suitable fashion. For example, the layers may be secured by adhesive, by mechanical fixings (e.g. screws, bolts or rivets) passing through the layers or by external mechanical fixings (e.g. clamps).

The sign or marker 1 discussed above is used in military aircraft where airerew use night vision systems. Referring to Figure 4, a number of signs or markers 1 may be used in an emergency exit system 15. The signs or markers I may be used to identify the location of emergency exits 17 or the routes to such exits, It will be appreciated that the whole, or a substantial part of the indicia layer 3 may comprise photoluminescent material 11 and the signs or markers 1 may be arranged in such a way so as to provide information, rather than using the photouminescent material II on the indicia ayer 3.

The indieia layer 3, filter layer 5. and slLbstrate layer 7 may be received in a frame.

The frame may surround the edges of the layers 3. 5. 7. the frame may also partially overlap the front face of the indicia layer 3 to provide a border and may partiaHy or wholly overlap the rear face of the substrate layer 7.

The frame may act to hold the layers together.

It win be appreciated that the substrate layer 7 is optional and may be omitted. The S strength and rigidity may be provided by the frame or by the material of the filter layer 5 and/or indicia layer 3 In some embodiments, the frame may be integral with the substrate 7.

In the above example. the indicia layer 3 has been described as only emitting from one face, However, it will be appreciated that the indicia layer 3 may comprise photolumineseent material 11 on both faces and thus emit radiation and convey information in different directions. Alternatively the sign or marker 1 may comprise two indicia layers 3 and two associated filters 5 arranged to emit radiation in different directions.

It win also be appreciated that the indicia layer 3 may be transparent in the regions without photoluminescent material I I and thus the substrate 7 or surrounding environment may provide the background to the sign.

The above examples have been described with reference to a phosphorescent material.

However, it wifl be appreciated that the photoluminescent material I I could also be a fluorescent material, which emits radiation for a short period after excitation. In such examples, the sign or marker 1 will also include an excitation source.

The luminescent material may also be a electroluminescent material, which emits radiation in response to electrical stimulation. In such an example, the sign or marker 1 will also include a power supply.

Although the invention has been described in reference to emergency exit systems in aircraft, it will be appreciated that it is equally applicable to other uses where night vision system compatible signs are required.

In the above examples. specific wavelengths have been disclosed. It will be appreciated that the night vision system may be sensitive to any suitable range of wavelengths and, depending on the choice of photoluminescent material 11 and the choice of filter layer 5 and filters in the night vision system, the sign may be effective over any range of wavelengths.

Claims

Claims A sign or marker for use in an aircraft emergency exit system, the sign or marker comprising: an indicia layer; and a filter covering the indicia layer arranged to selectively filter emission of electromagnetic radiation from the indicia layer.D
2, The sign or marker of claim 1 wherein the indicia layer comprises a photoluminescent material.
3, The sign or marker of daim 2 wherein the photoluminescent material emits radiation in the near infra-red part of the electromagnetic spectrum.
4. The sign or marker of claim 3 wherein the photoluminescent material emits radiation of wavelength up to 950nm.
5. The sign or marker of any preceding claim wherein the filter is arranged such that emission in the near infra-red part of the electromagnetic spectrum is controfled,
6. The sign or marker of any preceding claim wherein the filter scales down near infra-red emission from the indicia layer and effectively blocks emission in the infra-red part of the electromagnetic spectrum.
7. The sign or marker of any preceding claim wherein the filter reduces near infra-red emission from the indicia layer by an order of magnitude or more.
8, The sign or marker of any preceding claim wherein the filter reduces emission of wavelength greater than 600nm,
9. The sign or marker of any preceding claim wherein the filter blocks emission of wavdength greater than 9SOnm,
10. The sign or marker of claim 9 wherein the filter blocks emission of wavelength greater than 800nm.
11, The sign or marker of any preceding c'aim wherein near infra-red emission from the sign or marker is at a level that is visible through night vision systems.
12, The sign or marker of caini I I wherein the infra-red emission is visibk without causing flaring or blooming.
13, The sign or marker of claim 11 or claim 12 wherein radiance of the photoluminescent material, scaled to 15 fL. is less than 150 W/cm2 cm nm.
14. The sign or marker of any of claims 11 to 13 wherein radiance of the photoluminescent material, scaled to 15 fL, is greater than 47 WIcm2 cm nm, 15, The sign or marker of any of claims 11 to 14 wherein radiance of the photoluminescent material is between 50 W/cm2 cm nm and 150 W/em2 em nm.16, The sign or marker of any of claims 11 to 14 wherein the radiance of the photoluminescent material is between 47 W/cm2 cm nm and 140 W/em2 em nm.17, The sign or marker of any preceding c'aim wherein the photoluminescent material emits radiation over a range of wavelengths.18. The sign or marker of any preceding claim wherein the photolumineseent materi& emits radiation in the visible part of the electromagnetic spectrum.19. The sign or marker of any preceding claim wherein a maximum level of radiance from the photokimineseent materia' is in the visible part of the electromagnetic spectrum.20. The sign or marker of any preceding claim wherein the filter is arranged to let at least some of the emission in the visible part of the spectrum pass.21. The sign or marker of any preceding c'aim wherein the photoluminescent material is a phosphorescent material, 22. The sign or marker of any preceding c'aim wherein the photolumineseent materi& comprises a dopant.23. The sign or marker of any preceding claim wherein the photoluminescent materi& comprises Strontium Ahiniinate, 24, The sign or marker of any preceding claim further comprising a frame S substantiafly or whoHy surrounding the edges of the filter and indicia layer.25. The sign or marker of any preceding claim wherein the indicia layer is arranged to provide markings, dircction or indications of emergency exits or emergency routes.26. The sign or marker of claim 25 wherein, when the indicia layer comprises a photoluminescent material, the photoluminescent material is arranged to provide the markings, directions or indications.27. The sign or marker of any preceding claim wherein tile indicia layer is arranged to emit radiation in a first direction and a second direction, 28, The sign or marker of any of claims 1 to 26 wherein the sign or marker comprises a first indicia layer, arranged to emit radiation in a first direction and a second indicia iayer arranged to emit radiation in a second direction.29. The sign or marker of claim 27 or claim 28 further comprising a first filter arranged to filter radiation emitted in the first direction and a second filter arranged to fUter radiation emitted in the second direction.30, The sign or marker of any preceding claim wherein the indicia layer is provided on a substrate.31, The sign or marker of any preceding daim for use in a night vision goggle compatibk system.32. A night vision system for an aircraft comprising at least one sign or marker according to any preceding claim.33. The night vision system of claim 32 wherein emergency exits signs and pathways are visib'e to aircrew using night vision goggles.34, The night vision system of daim 32 or claim 33 further comprising night vision goggles for use by atrcrew of the aircraft.35. The night vision system of claim 34 wherein the goggles include an objective filter.36, The night vision system of claim 35 wherein the objective filter effectively blocks radiation in the visible region of the electromagnetic spectrum and allows radiation in the near infra-red and infra-red part of the electromagnetic spectrum to pass.37. The night vision system of claim 35 or claim 36 wherein the objective filter blocks radiation of wavekngth tess than 600nm, 38, The night vision system of any of claims 35 to 37 wherein the objective filter allows radiation of wavelength greater than 700nm to pass.39, An aircraft comprising a night vision system according to any of claims 32 to 38.40, The aircraft of claim 39 wherein the aircraft is provided with night vision compatible emergency exits signs and markers, 41. The aircraft of claim 40 wherein the signs and markers are arranged in the aircraft to mark the emergency exits and direct the aircrew to said exits in an emergency.42, A method of providing night vision system compatible emergency exit signs and/or markers the method comprising: providing photohiminescent signs and/or markers that emit radiation in the near infra red part of the dectromagnetic spectrum; and filtering the emission from the signs and/or markers such that emission in the near infra-red part of the electromagnetic spectrum is controlled.