REFLECTOR HAVING RADIAL FLUTES
United States Patent 3758770
A parabaloidal reflector adapted to receive an elongate light source along the axis of the reflector includes a number of fluted portions arranged in a repeated pattern over the surface of the reflector. The reflector achieves more uniform light reflection because adjacent fluted portions are concave or convex when viewed in cross-section and which merge in a geometrically discontinuous manner. The radius of curvature of the fluted portions in cross-section is the same from the widened open portion of the reflector to the narrowed tip.
US Patent References:
Reflector
Bean - March 1936 - 2035215
Headlight reflector
Schimpff - January 1932 - 1841917
Reflector for headlights
Matisse et al. - December 1925 - 1566906
Reflector for automobile lamps
Michel - November 1924 - 1513844
Reflector for use in light-projectors
Balsillie - September 1921 - 1390747
Reflector
Bean - March 1936 - 2035215
Headlight reflector
Schimpff - January 1932 - 1841917
Reflector for headlights
Matisse et al. - December 1925 - 1566906
Reflector for automobile lamps
Michel - November 1924 - 1513844
Reflector for use in light-projectors
Balsillie - September 1921 - 1390747
Application Number:
05/210408
Publication Date:
09/11/1973
Filing Date:
12/21/1971
Export Citation:
Assignee:
U.S. Philips Corporation (New York, NY)
Primary Class:
International Classes:
F21V7/09; F21V7/00; F21V7/09
Field of Search:
240/41.36,103,78LG 350/293
View Patent Images:
Primary Examiner:
Matthews, Samuel S.
Assistant Examiner:
Bero E. M.
Claims:
What is claimed is
1. A reflector for an elongate light source comprising:
2. A reflector as in claim 1 wherein each convex flute portion is cojoined with a concave flute portion on either side edge and each concave portion is cojoined with a convex portion at one side edge and a concave portion at the other edge.
3. A reflector as claimed in claim 1 wherein each flute portion has the same radius of curvature when viewed in cross-section to the parabaloidal radius dimension of the flute portion at any place along the flute portion.
1. A reflector for an elongate light source comprising:
2. A reflector as in claim 1 wherein each convex flute portion is cojoined with a concave flute portion on either side edge and each concave portion is cojoined with a convex portion at one side edge and a concave portion at the other edge.
3. A reflector as claimed in claim 1 wherein each flute portion has the same radius of curvature when viewed in cross-section to the parabaloidal radius dimension of the flute portion at any place along the flute portion.
Description:
The invention relates to a reflector for an elongate light source which is arranged therein axially with its longitudinal direction.
When such a reflector is provided with an elongate light source which is arranged therein axially, it provides a beam of light which has a large light intensity particularly in its central part.
In order to obtain a light beam having a uniform light distribution, the reflector could be provided with a number of radially extending flutes which contribute to a spreading of the reflected light beam. When, for reasons of manufacture, a constant radius of curvature is maintained in the cross-section of the flute, it is found that along a flute which, near the top of the reflector, is narrower than at the largest reflector circumference, the spreading is not constant which is also undesirable.
Instead of this, said flutes could be provided with a radius of curvature which is not constant so as to improve the constancy of the light spreading along the flute. However, this is particularly difficult to realize.
It is the object of the invention to provide a reflector which also comprises radial flutes and which on the one hand is simple to manufacture and on the other hand has good light spreading properties.
For that purpose, the reflector according to the invention is characterized in that the reflecting inner surface of the reflector comprises a number of light-spreading flutes which extend in the radial direction of the reflector, merge into each other discontinuously, and are concave and convex relative to said reflector, the spreading capacity of each convex flute, calculated in a direction at right angles to the optical axis of the reflector, decreasing from a maximum in the proximity of the side edges of the flute to a minimum at a location between the two edges, the spreading capacity of each concave flute increasing from a minimum in the proximity of the edges of the flute to a maximum at a location between the edges, the maximum spreading capacity of the convex flutes decreasing in a direction from the largest circumferential edge to the top of the reflector, and the minimum spreading capacity of the said concave flutes increasing in the direction of the reflector. In a reflector thus formed, each time a concave flute and an adjacent convex flute may be considered as a unit, the two longitudinal edges of one of the flutes constituting places for a maximum spreading capacity and the two remaining longitudinal edges of the other flute constituting places for a minimum spreading capacity. As a result of this combination it is obtained that the distribution of the reflected light is substantially uniform throughout the length of the unit constituted by two adjacent flutes.
According to a preferred embodiment of the reflector according to the invention, each flute has a cross-section which shows the same radius of curvature throughout the longitudinal dimension of the flute.
In order that the invention may be readily carried into effect, it will now be described briefly with reference to the drawing, in which
FIG. 1 is a longitudinal cross-sectional view of the reflector according to the invention
FIG. 2 is a sectional view taken on the line II--II of FIG. 1, and
FIG. 3 is a sectional view taken on the line III--III of FIG. 1.
The reflector shown in FIG. 1 is essentially formed as a paraboloid 1; axially arranged in said reflector is an elongate filament 2 which is arranged in the focus F.
Said reflector comprises a number of radially extending convex and concave flutes 4 and 6 which have a cross-section (FIGS. 2 and 3) which is formed from arcs of circles having radii R 1 and R 2 . The concave flute is formed from two parts 6a and 6b.
Each concave flute changes into a convex flute according to a discontinuous transition. Each flute forms part of a circular-cylindrical surface. This has for its result that the flute width decreases as the cross-section is nearer to the top 5 of the reflector.
The light rays reflected by the reflector are shown diagrammatically in FIG. 2.
The rays a incident on the convex flutes 4 are reflected in the opposite direction, while the rays b are reflected in a scattered manner according as the place of incidence approaches the point of intersection between a convex and a concave flute denoted by 7. The spreading capacity thus is maximum near said point of intersection 7.
The rays c incident on the concave flutes 6 are reflected in an analogous manner in an opposite direction, while the rays d are reflected in a more strongly spread manner between the center of the flute 6a, 6b. The spreading capacity thus is maximum near the edge 8.
At the area of the cross-section III--III, the convex flutes 4 are narrower and the cross-section comprises less strongly spreading parts, while in the concave flutes 6 the less strongly spreading parts are substantially lacking. As a result of this the spreading properties in two adjacent concave and convex flutes will become stronger or weaker towards the center calculated in the longitudinal direction of the flutes. This promotes a uniform reflection throughout the cross-section of the reflected light beam.
In the above example, each pair of adjacent flute is shown as a convex flute 4 and a concave flute consisting of two parts 6a and 6b. Of course, a convex flute consisting of a few parts and a single concave flute may be chosen for approximately the same uniform light reflection. Combination thereof may also be chosen.
When such a reflector is provided with an elongate light source which is arranged therein axially, it provides a beam of light which has a large light intensity particularly in its central part.
In order to obtain a light beam having a uniform light distribution, the reflector could be provided with a number of radially extending flutes which contribute to a spreading of the reflected light beam. When, for reasons of manufacture, a constant radius of curvature is maintained in the cross-section of the flute, it is found that along a flute which, near the top of the reflector, is narrower than at the largest reflector circumference, the spreading is not constant which is also undesirable.
Instead of this, said flutes could be provided with a radius of curvature which is not constant so as to improve the constancy of the light spreading along the flute. However, this is particularly difficult to realize.
It is the object of the invention to provide a reflector which also comprises radial flutes and which on the one hand is simple to manufacture and on the other hand has good light spreading properties.
For that purpose, the reflector according to the invention is characterized in that the reflecting inner surface of the reflector comprises a number of light-spreading flutes which extend in the radial direction of the reflector, merge into each other discontinuously, and are concave and convex relative to said reflector, the spreading capacity of each convex flute, calculated in a direction at right angles to the optical axis of the reflector, decreasing from a maximum in the proximity of the side edges of the flute to a minimum at a location between the two edges, the spreading capacity of each concave flute increasing from a minimum in the proximity of the edges of the flute to a maximum at a location between the edges, the maximum spreading capacity of the convex flutes decreasing in a direction from the largest circumferential edge to the top of the reflector, and the minimum spreading capacity of the said concave flutes increasing in the direction of the reflector. In a reflector thus formed, each time a concave flute and an adjacent convex flute may be considered as a unit, the two longitudinal edges of one of the flutes constituting places for a maximum spreading capacity and the two remaining longitudinal edges of the other flute constituting places for a minimum spreading capacity. As a result of this combination it is obtained that the distribution of the reflected light is substantially uniform throughout the length of the unit constituted by two adjacent flutes.
According to a preferred embodiment of the reflector according to the invention, each flute has a cross-section which shows the same radius of curvature throughout the longitudinal dimension of the flute.
In order that the invention may be readily carried into effect, it will now be described briefly with reference to the drawing, in which
FIG. 1 is a longitudinal cross-sectional view of the reflector according to the invention
FIG. 2 is a sectional view taken on the line II--II of FIG. 1, and
FIG. 3 is a sectional view taken on the line III--III of FIG. 1.
The reflector shown in FIG. 1 is essentially formed as a paraboloid 1; axially arranged in said reflector is an elongate filament 2 which is arranged in the focus F.
Said reflector comprises a number of radially extending convex and concave flutes 4 and 6 which have a cross-section (FIGS. 2 and 3) which is formed from arcs of circles having radii R 1 and R 2 . The concave flute is formed from two parts 6a and 6b.
Each concave flute changes into a convex flute according to a discontinuous transition. Each flute forms part of a circular-cylindrical surface. This has for its result that the flute width decreases as the cross-section is nearer to the top 5 of the reflector.
The light rays reflected by the reflector are shown diagrammatically in FIG. 2.
The rays a incident on the convex flutes 4 are reflected in the opposite direction, while the rays b are reflected in a scattered manner according as the place of incidence approaches the point of intersection between a convex and a concave flute denoted by 7. The spreading capacity thus is maximum near said point of intersection 7.
The rays c incident on the concave flutes 6 are reflected in an analogous manner in an opposite direction, while the rays d are reflected in a more strongly spread manner between the center of the flute 6a, 6b. The spreading capacity thus is maximum near the edge 8.
At the area of the cross-section III--III, the convex flutes 4 are narrower and the cross-section comprises less strongly spreading parts, while in the concave flutes 6 the less strongly spreading parts are substantially lacking. As a result of this the spreading properties in two adjacent concave and convex flutes will become stronger or weaker towards the center calculated in the longitudinal direction of the flutes. This promotes a uniform reflection throughout the cross-section of the reflected light beam.
In the above example, each pair of adjacent flute is shown as a convex flute 4 and a concave flute consisting of two parts 6a and 6b. Of course, a convex flute consisting of a few parts and a single concave flute may be chosen for approximately the same uniform light reflection. Combination thereof may also be chosen.