NZ270115A - Submarine lighting notch filtered from 400 to 550 nanometres to avoid phototaxis - Google Patents

Description

27 0 1 1 5 NEW ZEALAND PATENTS ACT, 1953 No: Date: 270115 09/12/94 PATENT OFFICE \ \ DEC 1995 RECEIVED COMPLETE SPECIFICATION "Sub Sea Lighting" I, PETER JOHN McCOMB. a New Zealand citizen of 4 Wallace Place, New Plymouth, New Zealand in trust for SUB SEA INTERNATIONAL NEW ZEALAND, INC., an incorporated company registered under the laws of New Zealand of 146 Devon Street East, New Plymouth, New Zealand, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: 27 0 1 1 5 The present invention relates to improvements in sub sea lighting.

Phototaxis by underwater lighting creates difficulties in underwater vision whether directly by or to a human being as a diver or in a submersible or by a remote vision system to enable a human being to control a remotely controlled submersible from above surface.

The phototaxis is primarily of krill species which, in New Zealand waters, is primarily Nyctiphanes Australis.

The present invention is applicable to sub sea lighting and related methods which has the effect of minimising phototaxis likely to affect direct or remote vision through the seawater or which will at least provide the public with a useful choice.

In a first aspect the present invention consists in a sub sea lighting system that is substantially devoid of light within the wavelength range of from 400 to 550 nm.

Preferably said light source is a filtered light source, the filter removing light within the aforementioned range.

In other forms of the present invention the light source itself will generate a wavelength or range of wavelengths outside of the aforementioned range.

In yet a further aspect the present invention consists in a sub sea lighting system which employs a filtering system to substantially remove wavelengths of the light being emitted into the seawater in the range of from 400 to 550 nm.

In still a further aspect the present invention consists in a vision system for a remote controlled submersible vehicle having or to have a lighting system to emit light into the seawater, characterised in that such light, by filtering or otherwise, is or is to be substantially devoid of light of wavelength of from 400 to 550 nm range and wherein there is or is to be a video camera system able to detect at least some of the reflected light outside of the wavelength of from 400 to 550 nm which is being or is to be emitted into the seawater by the light source and to relay remotely the view to an operator of the vehicle.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the 27 0 1 1 5 appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

The invention consists in the foregoing and also envisages constructions of which the following gives examples.

One preferred form of the present invention will now be described with reference to the accompanying drawings in which; Figure 1 is a graph of wavelength in nanometers against characteristic absorption length (in metres) of seawater showing the selective transmission of light by oceanic seawater, Figure 2 is a graph showing wavelength again in nanometers against transmission percentages for an acrylic optical filter which incorporates a dichromate filtrate, and Figure 3 is an exploded view of a preferred form of a non phototaxic lens and associated components.

The present invention recognises die problem caused in New Zealand waters by Nyctiphanes Australis as a result of phototaxis from the usual light sources used under water.

With offshore oil and gas production (as at the Maui field offshore of Taranaki, New Zealand) difficulties are frequently encountered as a result of the phototaxis of the krill species Nyctiphanes Australis, Similar difficulties are encountered with other krill species in other waters. All such krill scatter and reflected light.

The water type at the Maui field described is oceanic and has a minimum attenuation of light at about 400 nm. In this respect refer to Figure 1 which plots characteristic absorption length (in metres) against wavelength in nanometers.

With remote controlled sub sea vehicles being used to investigate structures etc. under the sea in the Maui field, difficulty arises if the vision system for such a vehicle (hereinafter "ROV") is affected by the phototaxis of Nyctiphanes Australis since the remote operator of the ROV is dependant upon the vision of the scene being relayed to him/her by the video camera carried by the ROV and transmitted to the surface where it is displayed. The vision system of course is dependent on reflected light and the primary source of such light that is reflected are the ROV lights themselves. 270115 It is usual to use quartz halogen lights for an ROV. The emission peak thereof corresponds approximately to that of maximum transmission in oceanic seawater.

With a view to determine whether or not krill species in general (and Nyctiphanes Australis in particular) are phototaxicly sensitive only to certain wavelengths and that wavelengths outside of any sensitive wavelengths are available for a satisfactory vision system for an ROV sensitivity tests have been conducted.

For the species Nyctiphanes Australis spectral sensitivity has been determined by analysis of both eye pigments and experiments in phototactic response. Sensitivity has been discovered at the range of420 to 480 nm (a primaiy response - peak sensitivity 462 nm). A secondary response was also noted at the wavelength of 530 nm (this is a smaller sensitivity peak than that encountered at 462 nm).

The bioluminescence emission peak of Nyctiphanes Australis is over die range of primary spectral photosensitivity. Such bioluminescence is emitted radiation that is emitted in short bursts. It has been found therefore that by eliminating all die identified frequencies/wavelengths for which Nyctiphanes Australis has primary and secondary photosensitivity from the ROV light source, the phototaxis will be avoided almost completely, if not completely.

The present invention therefore has resulted in a lighting system being created suitable for a ROV which is substantially devoid of light in the wavelength range of from 400 to 550 nm which ensures coverage of both the primaiy and secondary spectral sensitivity peaks/ranges for the species. Such a range also covers other krill species. Therefore while such a light source will have a minimal phototaxic affect on the species, Nyctiphanes Australis in the ocean (assuming that species is present), pach a light source emitting wavelengths only outside of that range will also have a reduced effect on other krill species.

The preferred approach to the provision of a light source devoid of light in the wavelength range is to provide an appropriate optical filter to reduce the unwanted frequencies from the ROV light source thus making standard lighting sources usable w>th the present invention.

The preferred filter medium is an acrylic base incorporating a dichromate filtrate. In this respect, see Figure 2. 27 0 1 1 5 In other forms of the present invention a light source for an ROV or other sub sea lighting system can be provided which generates wavelengths or a wavelength only outside of the excluded range of from 400 to 550 nm. That too is within the scope of the present invention.

Illustrated in Figure 3 is a non phototaxic lens and associated base, lamp and cover.

Claims (9)

-6- 27 0 1 1 5 WHAT I CLAIM IS:

1. A sub sea lighting system having a light source that is substantially devoid of light within the wavelength range of from 400 to 550 nm.

2. A sub sea light system as claimed in claim 1 wherein said light source is a filtered light source, the filter removing light within the aforementioned range.

3. A sub sea light system as claimed in claim 1 wherein said light source will generate a wavelength or range of wavelengths outside the range of from 400 to 550 nm.

4. A sub sea lighting system which employs a filtering system to substantially remove wavelengths of the light being emitted into the seawater in the range of from 400 to 550 nm.

5. A vision system for a remote controlled submersible vehicle having or to have a lighting system to emit light into the seawater, characterised in that such light, by filtering or otherwise, is or is to be substantially devoid of light of wavelength of from 400 to 550 nm range and wherein there is or is to be a video camera system able to detect at least some of the reflected light outside of the wavelength of from 400 to 550 nm which is being or is to be emitted into the seawater by the light source and to relay remotely the view to an operator of the vehicle.

6. A remote controlled submersible vehicle having or to have a lighting system to emit light into the seawater, characterised in that such light, by filtering or otherwise, is or is to be substantially devoid of light of wavelength of from 400 to 550 nm range and wherein there is or is to be a video camera system able to detect some of the reflected light outside of the wavelength of from 400 to 550 nm which is being or is to be emitted into the seawater by the light source and to relay remotely the view to an operator of the vehicle.

7. A sub sea lighting system as claimed in any one of claims 1 to 4 substantially as hereinbefore described with reference to any one, some or all of the accompanying drawings.

8. A vision system as claimed in claim 5 substantially as hereinbefore described with reference to any one, some or all of the accompanying drawings. 27 0 1 1 5 -7-

9. A remote controlled submersible vehicle as claimed in claim 6 substantially as hereinbefore described with reference to any one, some or all of the accompanying drawings. DATED THIS DAY OF AGENTS FOR THE APPLICANT