GB2343015A - Light transfer by total internal reflection for illuminating building interior - Google Patents

Abstract

A flexible transparent tube contains a transparent liquid or gel. The refractive index of the liquid must be near or to any degree above the refractive index of the transparent tube containing it. Tube bore sizes and lengths of run can be chosen to suit. The system can be filled with the liquid whilst in situ in the building. The tube may be polyvinyl chloride and the liquid may be glycerol.

Description

U5GE SCALE TOTAL INTERNA REFLECTION If one was seeking to employ total intemal reflection (as used in flexible glass fibre optics) on a much larger scale to provide daylight to inner areas of buildings, these constraints would arise.

It would be extremely difficult and prohibitively expensive to manufacture glass in the sizes required. It would also be very difficult to handte and install in a building. Such a system by virtue of its size would be inflexible.

This invention makes it possible and affordable to transfer large amounts of light through a large diameter transparent flexible tube.

The specification describes a liquid or semi-solid liquid gel in a transparent waterproof tube transferring light by total internal reflection.

Although the description describes the respective refractive indices of the liquid and the tube at near par to perform total internal reflection at the outer boundary of the tube wall and the surrounding air, should the liquid or semi-solid liquid be of higher refractive index than the tube, the light would then perform total internal reflection at either the inner boundary wall or outer boundary watt depending on its angle of incidence. If the liquid was of considerably higher refractive index than the tube then most of the light would totally internally reflect at the inner wall to some advantage as it does not incur part absorption by the tube wall.

No advantage would be gained from using a liquid of lower refractive index than the tube wall as the light would then bend towards the normal and exit the tube wall.

For ease of description the respective refractive indices are described at par.

This description uses a transparent flexible polymer (PVC) tube which has a refractive index of near 1.4725. The input and output ends of the tube are sealed with a transparent seal of similar refractive index. Through a filler hole is poured a liquid polymer (glycerol) with a refractive index of 1. 4725 to completely fill the tube. Light from a wide angle of incidence enters the input sea ! and refracts towards the normal and above the critical angle for the tube wall. The refractive index of the glycerol ensures the light remains above the crifical angle for the tube wall.

The closeness of the refractive index of the PVC tube and the liquid glycerol ensures that a beam incident in the glycerol above the critical angle for the tube watt side remains above the critical angle when it enters the PVC tube wall, it then performs total internal reflection at the outer boundary of the tube wall and the air. These total intemal reflections re-occur until the light is emitted 'from the output seal. The system can perform horizontally verffcally or angular.

Tube bore sizes and lengths of run can be chosen to suit. The system can be filled with its liquid refractive core whilst in situ in the building.

Claims (5)

1. CLAIMS 1. A light transference system that uses a transparent liquid or semi-solid liquid or gel contained within a transparent solid.
2. 2. A light transference system as in claim 1 that uses. a liquid thats refractive index is near or to any degree above par with its transparent sol. id containment.
3. 3. A light transference system as in claims 1 and 2 that has an outer transparent containment of the liquid which is flexible.
4. 4. A light transference system as in claims 1,2 and 3 in which its inner refractive core can be poured.
5. 5. A light transference system substantially as herein described.