Note: Descriptions are shown in the official language in which they were submitted.
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REFLECTOR'LAMP'WITH SHAPED REFLECTOR AND LENS
~ _ _ _ _ _
Refe'rence''to'Rela'ted _pp'l'ica'tion
Serial No. 381,080, filed July 3, 1981, Reiling,
Putz, and VanHorn, "Reflector Lamp", assigned the same
as this invention.
~'ackground o-f the Invention
The invention is in the field of reflector
lamps, such as flood lights and spot lights, having
reflectors and lenses. In such lamps, the light source
is deeply recessed in a concave reflector which reflects
frontwardly in a desired beam pattern substantially more
than half of the total light output of the lamp.
The above-referenced patent application discloses
a reflector lamp having a concave reflector comprising
parabolical and spherical sections, for pro~ecting a
pattern of parallel light rays in a frontward direction.
In the use of a concave reflector lamp, there is an
undesirably wasted amount of light which emanates from
the light source and is not reflected but radiates in a
divergent cone pattern through the front of the
reflector.
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Summary of the Invention
Objects of the invention are to provide a
reflector lamp, combined with a lens, having improved
optical efficiency which permits a design having lower
power consumption~ and to achieve this with a reasonably
compact lamp.
The invention comprises, briefly and in a
preferred embodiment, a reflector lamp having a concave
reflector, which may have one or more parabolic
sections, for reflecting light Erontwardly from a light
source located at the focal point. The light source is
deeply recessed in the reflector so as to be at least
three time~ as far from the Eront opening Oe the
reflector as from the reflector's vertex or virtual
vertex, so that substantially more than half of the
total light is re~lected by the reflector. A lens i~
positioned over the front of the reflector and is
contoured at least near the outer edge thereof to
refract frontwardly at leas~ some o~ the non-reflected
divergent light emanating directly from the light
source. ~or a flood light, substantially the entire
lens is contoured to refract and converge light rays
including the reflected light rays, so that the
reflected light rays converge into a cross-over pattern
to prov ide a flood beam pattern.
Brief Description_of the Drawing
.
Figure l is a front view of a re~le~tor lamp in
accordance with a preferred embodiment of the invention.
~ iyure 2 is a cross section side view taken on
the line 2-2 of Figure l.
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Figure 3 is a side view of the lamp and a flood
1 ight beam pattern.
Description of the Preferred Embodiment
A preferred embodiment of the inventic)n, as shown
in the drawing, comprises a ref.lector lamp having a
S concave reflector 11 shaped to have a front reflector
section 12 which has a parabolic contour w.ith respect to
a focal point 13, an intermediate reflector section 14
which has a spherical contour with respect to the focal
point 13, and a rear reflector sectioll 15 which has a
parabolic contour with respect to the focal point 13.
The cross-section of the reflector 11 perpendicular to
its principal optical axis is circular, as shown in
Figure 1. Thus, each of the three reflector sections is
defined by a surface of revolution of a parabolic or a
circular curveO A ~ilament 16 is centered at the focal
point 13 and pre~errably is located in or near the plane
17 of~mutual truncation at th~ joinder o~ the front
section 12 and inte-mediate section 14, as shown in the
drawing.
To achieve the maximum practical optical
; efficiency, reflector lamps are designed to have the
reflector 11 as deep as is feasible, to provide a large
area of the primary re1ecting surface 1~ for refleeting
substantially more than half of the total light into the
desired beam pattern and so that substantially less than
half of the total amount of light emanates directly and
~reflected from the light source 16 through the fron~
of the reflector in a divergent pattern whereby s~me of
the light is wasted because it falls outside of the
desired beam pattern. Thus, the light source 16 is
deeply recessed in the reflector and is typically at
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least three times the distance from the front plane or
rim 31 of the reflector than from the vertex, or virtual
vertex 12l in the embodiment shown, of the primary
relecting surface 12. The desired long depth of the
reflector is limited by practical considerations such as
not wanting unduly great size, weight, bulk, and cost of
the reflector. Alternative light sources may be
employed in place of the filament 16, such as a halogen
regenerative-cycle incandescent lamp or an arc discharge
lamp. A shaped lens 20 is placed or sealed over the
front opening of the reflector 11, primarily to modify
the light pattern, will be described, and also to
protect the reflecting surface and keep it clean, and a
c~ver or lens is required if the light source is a bare
filament 16 in the reflector. The reflector 11 may be
made of molded glass, its inner surface being coated
with aluminum or silver to provide a reflective surface,
and the filament 16 preferrably is made of tungsten and
is mounted on a pair of lead-in support wires 18, 19 of
suitable material such as molybdenum.
Light rays which emanate from the light source
16 at the focal point 13 and which strike the parabolic
front reflector section 12, will be reflected in a
generally frontward direction, as indicated by the light
ray paths 21. Similarly, light rays 22 emanating from
the filament 16 and which strike the parabolic rear
reflector section 15, will be reflected generally
frontwardly.
As is disclosed and claimed in the
above-referenced patent application, the spherical
intermediate section 14 is dimensioned with respect to
the parabolic front reflector section 12 so that all, or
substantially all, of the light emanating from the light
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source 16 and which strikes the spherical intermediate
section 14 r will be reElected thereby in a direction so
as to strike the parabolic Eront sect.ion 12 and be
re-reflected thereby in a generally frontward direct1on.
For example, a light ray 26 emanating from the light
source 16 at the ~ocal point 13 of the reflector,
strikes the intermediate spherical seotion 14 and is
reflected back along its path and through the focal
point 13, and strikes the parabolic front reflector
section 12 and is directed frontwardly as indicated by
previously mentioned the light ray path 21.
A preferred method of designing the reflector, i5
to first design the front section 12 and then design the
contour of the spherical section 14. Next, a line is
drawn from the rim 31, and through the focal point 13~
to the contour line of the intermediate section 14; this
point of intersection establ.ishes the joinder pl~ne 28
at the rear of the section 14 where it joins the rear
section 15. Thus the light ray 32 emanating from the
fooal point 13 and which strikes the spherical
intermediate section 14 at or adjacent to its rear plane
28, will be reflected back along its path and through .
the focal point 13, and strikes the parabolic front
section 12 at or near its front rim 31 and i5 directed
: 25 frontwardly as indicated at-32'. Another such light ray
32, 32' is show~ at the opposite side o~ the reflector.
In scientific optical terminology, the breadth of
the parabolic reflector curve at the focal point 13 is
the latus rectum and is represented in the drawin~ by
the line 17 in Fig. 2, ana ~he vertex is ~he poîn~ on
the rear surface directly behind the focal point 13.
The vertex of the front parabolic section 12 is the
point thereon that would be directly behind the fo~al
point 13 if the parabolic curvature were to be continued
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behind the focal point 13. Thus the focal point 13 is
relatively close to the vertex of the front parabolic
curve 12 and is substantially farther from the vertex of
the rear parabolic curve 15~ The diameter of the
S spherical intermediate section 14 is essentially equal
to the length of the latus rectum 17 of the front
parabolic curve 12.
Due to the elongated shape of the filament 16,
not all the light from different parts of the filament
is emitted at the focal point 13, and therefore, will be
reflected at slightly different anyles at any specific
point of the reflector. As a sonsequence not all of the
reflected light from the intermediate section 14 will
pass through the focal point 13. Therefore the optical
performance of the reflector will be somewhat degraded
from that which would be obtained ~rom a hypothetical
point source at the focal point 13.
The space defined and surrounded by the spherical
intermediate section 14 provides a recess for accommoda-
ting the light source 16, and spaces the reflectingsurface at the back part of the reflector suf~iciently
far way from the filament 16 to minimize bIackening
thereof by evaporated filament material, and
accomplishes this while retaining an optical efficiency
substantially as good as if the entire reflector had a
: single parabolic curvature.
Some of the light emanating from the souxce 16 is
not reflected by the reflector 11, and emerges from the
source 16 in a diverging cone-shaped beam, illustrated
by the cone edge pairs of light rays 33. Another
illustrative pair of diverying light rays 34 within the
aforesaid cone-shaped beam~ are also shown. This
con~-shaped heam, including the cone edge-defining rays
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33 and all other rays such as rays 34 contained therein
would, but for the lens 20, emerge through the front of
the reflector 11 in straight continuation rays 33', 34'.
All of the light rays of the cone-shaped beam, except
for those on the optical axis, are divergent and
inconsistent with the desired frontward parallel ray
pattern provided by the reflec:tor 11, and (but for the
lens 20) will fall outside the desired beam pattern and
will be wasted light in most applicationsO The closer
the cone rays are to the edge defining rays 33, the more
divergent they will be, these edge rays 33 being the
most divergent and other cone rays such as rays 34 which
are slightly within t~e cone edge rays 33 being only
sligh~ly less divergent.
The light rays 21, 32, 33, and 34 are shown as
pairs thereof symmetrically arranged about the optical
axis of the reflector llr to better illustrate the light
distribution patterns in the cross-sectional view of
Fig. 2 and to facilitate illustration in Fig. 3 of a
projected flood l;ight beam pattern.
In accordance with the present invention, the
lens 20 is contoured, at least near its outer rim, to
refract in a more frontward direction at least some of
the divergent "stray" light rays from the light source,
and the lens may be further contourèd to provide a flood
light beam pattern. The preferred contouring o~ the
lens is in the form of concentric prisms 36; preferably
on its inner surface, of the Fresnel lens type.
In ~ig. 2, the dashed-line light ray
representations 21, 32, 33, etc. represent light rays
from the source 16, both reflected and non-reflected
within the reflector 11, and the dashed-line
representations indicated by primed numbers 21', 32~,
33', etc. of these light rays in front of the light unit
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indicate what the ray patterns and directions would be
without the presence of the lens 20. The solid-line
representations, indicated by double-prirned numbers 21",
32", 33", etc. of these light rays in front of the lens
20 indicate their patterns and d:irections as modified by
the functioning of the lens in accordance with the
invention.
In accordance with the frist-men-tioned embodiment
of the invention, the concentric prisms 36 are provided
on the inner surEace of the lens 20 and only near the
outer periphery thereof, for exarnple in an outer region
of the lens so as to intercept all of the divergent light
rays between and including the rays 33 and 3a~. These
prisms 36 are shaped to be optically convergent, so as to
refract the divergent light rays 33, 34 and the divergent
rays therebetween, in a more frontward direction as
indicated by the solid-line rays 33" and 34", and thus
more nearly into the desired useful overall beam pattern.
At the same time, the reflected and frontwardly directed
light rays between and including the rays 21, 32 will be
converged inwardly by the lens prisms, as indicated by
the solid-line rays 21" and 32", and will cross over at
a region 38 (Fig. 3) in front of the lens 20 and
thereafter be divergent and directed somewhat out of the
desired beam pattern. A compromise can be found in the
lens design and its degree of optical convergence, so
that more useful light is gained in the desired overall
beam pattern by the frontward refraction of the
otherwise divergent rays 32', 33' than may be lost due
to the convergent refraction of the otherwise parallel
rays 21', 32'. This increases the useful light output
and/or permits the use of a lower wattage filament 16
thus conserving electrical energy. In this embodiment
of providing a lens 20 with concentric prisms 36 only
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near the periphery of the lens, the reflected and
non-reflected light rays from filament 16 which pass
through the lens cen~ral region, such as defined by a
circumference bounded by the light rays 21, are
substantially unaffected by the lens.
In another embodiment of the invention, a flood
lamp having improved electrical and optical efficiency
is achieved by providing the light-reEracting concentric
prisms 36 over substantially the entire inner surface of
the lens 20, as shown in Fig. 2. These prisms need not
be provided at the reflector's center area 41 where they
would be relatively ineffective. Referring again to
Fig. 3, in accordance with the flood light of the
invention, the lens 20 refracts the non-reflected
divergent light rays in a more frontwardly divergent
pattern, exemplified by the light rays 33" and 34",
which is in the desired divergent floodlight beam
pattern. Also, the lens 20 refracts the reflected
parallel light beams in a con~ergent manner to produce a
cross-over pattern of rays which thereafter are
divergent in the desired flood light pattern. For
example, the above-described light rays 21" and 32"
cross over at region 38 in front of the lens 20 and
thereafter diverge generally in the desired flood
light beam pattern. For more completeness, Fig. 3 shows
an additional pair of projected light rays 42" and 43"
which have been reflected by the reflector 11 toward the
lens 20 at an intermediate diameter region 44 thereof
and refracted by the lens to converge and cross over at
a region 46 in front of the lens and thereafter diverge
generally in the desired beam pattern. Unreflected
light rays passing through the lens at its intermediate
diameter region 44 will be refracted and projected
approximately frontwardly, thus contributing to the
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overall flood beam illumination. In lamps built
according to the invention, the crossover regions 38~ 46
lay in the range of about 5 to 20 inches in front of the
lens 20.
A unique feature of the invention is the
di~ergent projection of some light rays 33" and 34" and
the convergent projection of ot:her light rays 21", 32",
42", and 43" which light rays cross over and become
divergent in a manner compatible with the divergent rays
33" and 34" to provide a desired flood light beam
pattern. The concentric prisms 36 need not have
identical refra~tion angles; the refraction angles of
~ome or all of the various prisms can be different fron
one another to tailor the light distribution for uniform
intensity or other desired characteristics in the
projcted light beam. By thus providing the lens 20, in
cooperation with the reflector 11, most of the projected
light rays are in the desired beam pattern and
relatively little light is wasted, thus improving
efficiency and conserving electrical energy.
While preferred embodiments o~ the invention have
been shown and described, various other embodiments and
: modifications thereof will be come apparent to persons
skilled in the art, and will fall within the scope of
the invention as defined in the followiny claims.
