Stock material or miscellaneous articles – Hollow or container type article – Glass – ceramic – or sintered – fused – fired – or calcined metal...
Patent
1998-12-11
2000-12-05
Loney, Donald
Stock material or miscellaneous articles
Hollow or container type article
Glass, ceramic, or sintered, fused, fired, or calcined metal...
4283044, 4289133, 359485, 359493, 527861, 5278613, E06B 324, G02B 2728
Patent
active
061563978
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a light polarising panel and a method of making a polarisation layer for inclusion therein.
The phenomena of light polarisation is well known. Christian Huygens successfully experimented with calcite crystals in the early 18th century and found that they absorbed most of the horizontally polarised light particles.
Whilst it is the basis of linear polarisation for sunglasses and camera lenses calcite crystals are of little practical value in lighting fixtures as 50% of the light is lost by this absorption as horizontally polarised particles are approximately 50% of radiated light
An object of the present invention is to prevent the highest possible proportion of horizontally polarised particles leaving a lighting fixture by placing into the fixture aperture a multi-layer lens panel which, by a combination of reflection and refraction will induce reflux polarisation and preferactically vertically polarise the light.
In the middle of the 18th century Dominique Arago envisaged passing light through a stacked array of glass sheets. The refractive indices of the sheets allowed the partially vertically polarised light passing through the first sheet to be directed at a different critical angle to the second to secure more reflection of horizontally polarised particles. Provided that the light reflected from each surface was collected within the structure; depolarised by a reflective back surface and retrieved for a re-pass, the light emitted through the final glass plate was highly vertically plane polarised.
U.S. Pat. No. 2,402,176 discloses a polariser composed of 15-30 thin plastic sheets in permanent interfacial contact with each other with several advantages over the Arago method notably the lower absorption of light compared to thick glass plates.
U.S. Pat. No. 2,983,178 discloses a panel of 2-20 layers of glass flakes together with a low melting point glass. the panel then being heated, the low melting point of the glass in this compound was envisaged as creating air spaces with a marked difference in the refractive index of the glass flakes and the retained air.
U.S. Pat. No. 3,124,639 discloses the substitution of this glass compound by an extruded, translucent foam of polystyrene as he had observed that in such a thin is extruded sheet the action of the extruder flattened the cylindrical air cells in the plastic foam compound at the top and bottom surfaces of the sheet. It is to be noted that when the flattened cells were roughly in alignment they acted as an excellent polariser and the walls caused little light loss. Protective layers would be needed to maintain the flat plane of the base carrier sheet and a top layer of facing plastic shed to protect the fragile foam from damage and contaminants.
A method is known for continuously producing panels based on the above principle. A modified carrier sheet is also known which does not add to polarisation but is alleged to distribute the light more effectively.
The last mentioned panel has some disadvantages:
1. The degree of polarisation achieved with the foam material although significant and commercially successful is however limited to the efficiency of the creation of the flattened layered elliptical foam cells as described in U.S. Pat. No. 3,124,639 in the normal process of foam manufacture.
2. Any further changes that occur (if any) are limited to the bonding process described in U.S. Pat. No. 3,772,128. There are the additional material changes and the sole purpose of the invention is to bond three materials together by heat and thus save the cost of adhesives. By bonding the three into a composite component panels do not have the advantages of an interstitial component within which the additional air gaps between one or more succeeding layers improve the refractive performance.
3. The process specification to heat bond the facing film from the residual heat of the extruded base is layer, limits the protective efficiency of that film as it has to have a low melt point and be very thin. In consequence the panels are ver
REFERENCES:
patent: 3124639 (1964-03-01), Kahn
Clearvision, Inc.
Loney Donald
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