Year: 1888

page_text: Date of Application, 11th Jan., 1888
Complete Specification Left, 11th Oct., 1888
Complete Specification Accepted, 11th Jan., 1889
I, WOLF DEFRIES of No. 4 Cleveland Gardens in the County of Middlesex
Gentleman do hereby declare the nature of this invention to be as follows:-
My Invention relates to a method of distributing by reflection light from any
source in such a manner that the total amount of light which falls on a given area
directly and by reflection is distributed approximately in any desired proportion over
the area, and where desirable the whole of the available light is utilized for the
illumination of the area.
To accomplish the approximately uniform distribution of the light I divide the area
to be illuminated into a number of portions of suitable shape and of equal area and
measure the angles which they subtend at the source of light considered as a point.
I then divide the total beam capable of being utilized either as direct or as reflected
light into the same number of equal angles as that of the parts into which I divided
the area to be illuminated.
In the event of the angle subtended at the source of light by any division
of the area to be illuminated being not less than any one of the parts into which I
bave divided the beam, I arrange for that division to be illuminated solely by direct
rays. I then construct my reflector in such a manner that successive divisions of it
reflect beams of light equal to the difference between one of the parts into which the
total beam was divided and the beams which fall directly on the other different
divisions of the area to be illuminated; and by means of the method hereinafter
described I shape these divisions of the reflector so that they direct the beams which
they reflect in suchwise that they are distributed uniformly over the divisions of the
area to be illuminated to which they respectively refer.
By preference I arrange for successive divisions of the reflector to direct light on
to successive divisions of the area to be illuminated; but this is not invariably
advisable. Should one reflector become inconveniently large or should the rays
reflected by one part be intercepted by another I substitute for the portions of the

page_text: reflector to which the objection applies one or more supplementary reflectors
constructed in the same manner as the first reflector which serve to reflect the beam
or beams not used for direct illumination or reflected by the first reflector, and to
direct them in the desired proportions on to those divisions of the area not sufficiently
lighted by the direct light and that of the first reflector. It is obvious that the
edges of these supplementary reflectors may be at any distance from the source of
light along the extreme rays of the beams which they reflect without affecting the
result.
I may divide the total area to be illuminated into divisions of unequal area. In
such case the angles into which I divide the total light will have to be proportionate
to the divisions of the area. Each such angle will then correspond to one division
of the area; and the difference between such angle and the angle subtended at the
source of light by the area in question will be the amount of light to be reflected on
to that division of the area.
The method to be followed in distributing light otherwise than uniformly is
precisely similar to that above described.
It is obvious that the areas to be illuminated may be of any shape and in a vertical
or any other position.
For the purpose of greater case in drawing I may consider the reflected rays as
emanating from the source of light itself in cases where the angle which the reflector
subtends at a point on the area is relatively small as for instance in the application
next described. A special case of this invention is that in which the area to be
illuminated is a portion of a sphere of large radius which has the source of light as
centre. In that case the amounts of light falling directly on equal areas are them-
selves equal; and the reflector is employed to distribute the light falling on it
uniformly over the area to be illuminated. Such a case is that of a ship's masthead
lamp, which requires for convenience of size the use of several reflectors each
constructed on the method herein described. In order that in the case where direct
rays are uniformly distributed over an area the application to a single source of light
of several reflectors constructed according to my invention may be more clearly
understood, I will now proceed to describe an application of my invention to the
construction of a ship's mast head lamp, of which the object is to diffuse a uniform
and unbroken light over a horizontal angle of say, 225° through a given vertical
angle.
To do this I propose to make the reflector in five distinct parts which may be
respectively referred to as the back, two sides, top and bottom of the reflector. The
top and bottom receive that portion of the light which falls directly within the
horizontal angle of 225° and without the vertical angle to be illuminated.
The top
and bottom are so constructed that each ray remains after reflection in its original
vertical plane, and the sections of top and bottom will then each be 225° of circles
with the source of light as centre. The direct rays nearest the vertical are reflected in
a horizontal direction and the extreme rays falling upon the top and bottom furthest
from the vertical are reflected along the extreme downward and upward directions
respectively of the angle to be illuminated. The intermediate rays are uniformly
distributed over the intermediate directions of the angle to be illuminated, successive
rays reflected into a number of equal parts being reflected along the directions of
successive lines dividing the angle to be illuminated into the same number of equal
parts. The back and sides receive the remainder of the light which does not directly
fall within the angle to be illuminated. This light will be divided according to the
method previously explained into a number of equal parts, each of which will be
thrown by the reflector in the direction of a corresponding division of the angle to be
illuminated. The back will receive so much of the light as may be desirable and the
sides will start from such positions along the extreine beam falling on the back as
will allow the rays reflected by the back to pass out behind the sides.
The horizontal section of the back will be such that all rays in the central vertical
beam of the light to be reflected will be reflected along the directions which bound the
horizontal angle to be illuminated.

page_text: The beams furthest from the central plane of the light will be sent by the sides in
the direction of the central beam; and the intermediate beams of the light to be
reflected will be uniformly distributed according to the method previously explained
over the intermediate directions of the angle to be illuminated. Each vertical
section will be similarly arranged to uniformly distribute the light falling on it over
some vertical section of the angle to be illuminated, of which the direction will be
obviously determined by the direction of the tangents to the horizontal sections of the
reflector at the points of incidence in the vertical section.
I may make my reflectors of any suitable reflecting substance.

page_text: 1, WOLF DEFRIES of No. 4 Cleveland Gardens in the County of Middlesex, Gentleman
do hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement :-
:-
My Invention relates to a method of distributing by reflection light from any
source in such a manner that the total amount of light which falls on a given area
directly and by reflection is distributed approximately in any desired proportion over
the area, and where desirable the whole of the available light is utilized for the
illumination of the area.
In order that my invention may be more clearly understood reference is had to the
accompanying three sheets of drawings.
In these Fig. 1. represents a vertical section through the source of light of an
arrangement of reflectors constructed according to my invention for the purpose of
effecting a uniform distribution of the whole of the light over a plane area to he
illuminated; Fig. 2. is a sectional elevation through an arrangement of reflectors
suitable for a ship's mast-head lamp, of which Fig. 3. is a plan.
To accomplish the approximately uniform distribution of the light over a plane area
I divide the area into a number of parts 1, 2, 3, . . . . of suitable shape and equal
area, and measure the angles which they subtend at the source of light B considered
as a point. These will be measured by the angle subtended by perspective projections
of these parts from the source of light on to a nearer plane parallel to the area.
A (Fig. 1) is a vertical section of these projections and it will accordingly be divided
into the same number of equal parts as that into which the area is divided. In the
event of any of these areas 1. 2. &c. subtending at the source of light B an angle
equal to or greater than one th of the total beam (in this instance 360°) capable of
being either used as direct or reflected light; I arrange for such area or areas to be
illuminated solely by direct rays. I then divide the total beam capable of being used either
as direct or reflected light into the same number m of equal angles as the number of
the areas on to which light is to be reflected. I then construct my reflectors E. F. G. H.
.in such a manner that successive divisions of them reflect beams of light equal to the
difference between one of the parts into which the total beam was divided and the
beams which fall directly on those divisions of the area A on to which light is to be
reflected.
By suitably increasing the number of such divisions the direct rays falling on each
division of the area may be considered to be uniformly distributed over such division,
and by means of the method hereinafter described 1 shape each division of the reflector
so that it directs the beams which it reflects in suchwise that they are distributed
uniformly over the division of the area to which it refers. By preference I arrange
for successive divisions of the reflector to direct light on to successive divisions of the
area to be illuminated, but this is not invariably advisable. Should one reflector
become inconveniently large or should the rays reflected by one part be intercepted by

page_text: another, 1. substitute for the portions of the reflector to which the objection applies,
one or more supplementary reflectors E. F. constructed in the same manner as the
first reflector G. H. which serve to reflect the beam or beams not used for direct
illumination or reflected by the first reflector, and to direct them in the desired
proportions on to those divisions of the area not sufficiently lighted by the direct light
and that of the first reflector. It is obvious that the edges of these supplementary
reflectors may be at any distance from the source of light along the extreme rays of
the beams which they reflect, without affecting the result. I may divide the total area
to be illuminated into divisions of unequal area; in such case the angles into which I
divide the total light will have to be proportional to the divisions of the area. Each
such angle will then correspond to one division of the area, and the difference
between such angle and the angle subtended at the source of light by the area in
question will be the amount of light to be reflected on to that division of the area. The
method to be followed in distributing light otherwise than uniformly or over curved
areas is precisely similar to that above described.
It is obvious that the areas to be illuminated may be of any shape and in a vertical
or any other position.
For the purpose of greater ease in drawing I may (as in Figs. 1, 2 and 3) consider
the reflected rays as emanating from the source of light itself. In Fig. 1 for instance
the ray reflected at H arrives on the actual area to be illuminated at practically the
same point as the last direct ray bounding division 8, which is parallel to the reflected
ray in question and the ray reflected at E arrives at the area at practically the same
point as the direct ray parallel to it that namely which divides sections 56. in cases
where the angle which the reflector subtends at a point on the area is relatively small
as for instance in the application next described.
A special case of this invention is that in which the area to be illuminated is a
portion of a sphere of large radius which has the source of light as centre. In that
case the amounts of light falling directly on equal areas are themselves equal; and the
reflector is employed to distribute the light falling on it uniformly over the area to be
illuminated. Such a case is that of a ship's mast-head lamp, which requires for
convenience of size the use of several reflectors each constructed on the method herein
described. In order that in the case where direct rays are uniformly distributed over
an area the application to a single source of light of several reflectors constructed
according to my invention may be more clearly understood I will now proceed to
describe an application of my invention to the construction of a ship's mast-head lamp,
of which the object is to diffuse a uniform and unbroken light over a horizontal
angle R. B. S. (Fig. 3.) of say 225° through a given vertical angle O. B. P. (Fig. 2.).
To do this I propose to make the reflector in five distinct parts (Figs. 2 & 3.) which
may be respectively referred to as the back K, two sides L. L. top M. and bottom N of
the reflector. The top M and bottom N receive that portion of the light which falls
directly within the horizontal angle of 225° and without the vertical angle to be
illuminated. The top and bottom are so constructed that each ray remains after
reflection in its original vertical plane, and the sections of top and bottom will then
each be 225° of circles with the source of light B as centre. The direct rays nearest
the vertical are reflected in a horizontal direction and the extreme rays falling upon the
top and bottom furthest from the vertical are reflected along the extreme downward
and upward directions respectively of the angle to be illuminated. The intermediate
rays are uniformly distributed over the intermediate directions of the angle to be
illuminated, successive rays dividing the light to be reflected into a number of equal
parts being reflected along the directions of successive lines dividing the angle to be
illuminated into the same number of equal parts. The light falling on the back and
sides of the reflector will be divided according to the method previously explained,
into a number of equal parts, each of which will be thrown by the reflector in the
direction of a corresponding division of the angle to be illuminated.
The back will receive so much of the light as may be desirable and the sides will
start from such positions along the extreme beam falling on the back as will allow the
rays reflected by the back to pass out behind the sides.

page_text: The horizontal sections of the back will be such that all rays in the central vertical
heam of the light to be reflected will be reflected along the directions B. R, B. S. which
bound the horizontal angle to be illuminated. The beams B. R, B. S. furthest from the
central plane of the light will be sent by the sides in the direction of B U of the
central beam; and the intermediate beams of the light to be reflected will be uniformly
distributed according to the method previously explained, over the intermediato
directions of the angle to be illuminated. Each vertical section will be similarly
arranged to uniformly distribute the light falling on it over some vertical section of
the angle to be illuminated, of which the direction will be obviously determined by
the direction of the tangents to the horizontal section of the reflector at the points of
incidence in the vertical section. I may make my reflectors of any suitable reflecting
substance.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. Reflectors constructed combined and arranged substantially as described, and for
the purpose set forth in the accompanying Specification and illustrated Fig. 1. (sheet 1.)
of the accompanying drawings.
2. Reflectors constructed combined and arranged, substantially as described and for
the purpose set forth in the accompanying Specification and illustrated Figs. 2 and 3.
(Sheets 2 and 3) of the accompanying drawings.
3. Distributing light by the aid of reflectors so that the total direct and reflected
light is uniformly or in any desired proportion distributed over a given area by
dividing, intercepting, and directing the whole or part of the rays of light in the
manner described and illustrated in the accompanying Specification and Drawings.
Dated this Eleventh day of October 1888.