Light emitting diode lamp having a spherical radiating pattern

An improved LED lamp having a uniquely shaped envelope to distribute the radiated light energy into a uniformly distributed spherical pattern. This novel lamp allows a 360 degree viewing angle in a horizontal plane about its central vertical axis, as well as, a 360 viewing angle about the vertical circle. The present invention utilizes a uniquely designed concave lens to establish a focal point within the envelope to re-radiate the radiant energy in a more efficient manner thereby creating a higher intensity without increasing the input power. Conventional LED's have a directional conical shaped pattern of concentrated light energy that provides suitable use in panel indicator lamp applications.

FIELD OF INVENTION 
The present invention relates to an improved light emitting diode lamp 
(LED) having a uniquely shaped envelope to distribute the radiated light 
energy into a uniform spherical pattern, and more particularly, to an 
improved light emitting diode lamp having a concave conical lens for the 
uniform distribution of light in all directions. 
BACKGROUND OF THE INVENTION 
Heretofore display signs, such as exit signs, used incandescent lamps and 
fluorescent lamps as sources of illumination. While these lamps provide 
relatively uniform sources of a broad visible spectrum of light, there are 
several problems that exist when using these lamps in exit sign 
applications. 
Incandescent lamps are relatively inefficient which results in large 
amounts of entrapped heat energy, shortened life of the bulbs and 
increased operating costs. The use of incandescent bulbs in exit sign 
applications requires that suitable ventilation be finished in the design 
of these signs to remove the entrapped heat. Also, an added undesirable 
attribute is the frequent maintenance that is required, such as, periodic 
bulb replacement when lamp failure occurs. Because these lamps are 
inefficient in operation, there are increased operating costs. 
While the use of fluorescent lamps circumvents the problems that are 
associated with entrapped heat, frequent lamp replacement, and inefficient 
operation; the size of the fluorescent lamp together with its required 
ballast, the necessity of higher voltage operation using alternating 
currents and the higher cost of replacement lamps, offset the advantages 
for its long term use. 
Most recently, semiconductor LED lamps have been used in display and exit 
sign applications. The use of conventional semiconductor light emitting 
diodes solves the problems of entrapped heat, lamp longevity, frequent 
lamp replacement and of higher voltage operation. 
However, one problem that exists when using conventional light emitting 
diodes is that of an non-uniform distribution of emitted light energy. The 
first attempt in using these diodes as sources of illumination was to 
provide a diffusion plate to minimize the uneven illumination. While many 
conventional LED lamps use water clear lenses, still another solution to 
this problem was to design a conventional LED lamp that included a 
diffused lens and envelope, such as the Panasonic LN21XP. 
Shown in FIG. 1 is a sectional view of a conventional LED lamp having one 
or more semiconductor chips 150. The transparent envelope 10 has a convex 
hemispherical shaped lens 12, located at the end of a cylindrically shaped 
rod 14. A semiconductor chip 150 is mounted to the conductive surface of 
the first electrode, LED anode 110, which is recessed within the convex 
reflector 140. A fine wire 130 connects the opposite end of the 
semiconductor chip 150 to the second electrode 120. 
Turning now to FIG. 2, shown is the cone shaped light pattern 16 that is 
emitted from this LED device. A beam of visible light projects in a cone 
that ranges in angularity from 12 to 36 degrees dependent upon the 
intended design usage. This designed lamp finds particular use in 
instrument panel lamp applications. 
Referring now to FIG. 3, illustrated is a sectional view of another 
conventional LED lamp having one or more semiconductor chips 150. The 
transparent envelope 20 of the cylindrical shaped rod 14 has a flat 
top-hat shaped lens 22. The semiconductor chip 150 is mounted to the 
conductive surface of the first electrode, the LED anode 110, which is 
recessed within the convex reflector 140. A fine wire 130 connects the 
opposite end of the semiconductor chip 150 to the second electrode 120. 
As shown in FIG. 4, the light that emanates from the semiconductor chips is 
projected on the flat surface lens 22, thereby giving a uniform surface of 
illumination that is suitable for use in instrument panel lamp 
applications. 
Examples of the prior art conventional light emitting diode structures will 
now be discussed in some detail. 
U.S. Pat. No. 5,289,082, granted Feb. 22, 1994, S. Komoto, discloses an LED 
lamp having a lead portion upon which are mounted a plurality of 
semiconductor chips placed on the tip portion of the lead, all surrounded 
by a translucent envelope. The envelope is characterized as being formed 
from a solid body containing parts of a plurality of ellipsoids whose axes 
extend through the semiconductor chips. 
U.S. Pat. No. 5,083,192, granted Jan. 21, 1992, to J. Rzeznik, et al, 
discloses light concentrating cluster mount for super bright high 
intensity light emitting diodes. 
U.S. Pat. No. 4,849,803, granted Jul. 18, 1989, to T. Yamamoto, et al, 
discloses a molded resin semiconductor device having a plurality of 
semiconductor chips surrounded by a low thermal expansion, high thermal 
conductivity thermosetting resin. This in turn is encapsulated in a 
flexible resin having high expansion and low conductivity coefficients. A 
final thermosetting resin coating completes the assembly. 
U.S. Pat. No. 4,041,516, granted Aug. 9, 1977, to R. W. Murray, discloses a 
high intensity light emitting diode having improved radiation intensity 
and distribution characteristics. 
U.S. Pat. No. 4,032,963, granted Jun. 28, 1977, to G. P. Thome, teaches a 
method and structure for encapsulating a light emitting device. A package 
is provided to prevent failure due to chemical contaminants. 
Many of the above referenced prior art disclose methods and apparatus for 
concentrating the radiant light energy into a narrow conical beam to 
optimize the viewing angle so that the light emitting diode is suitable 
for use in panel lamp applications. Also, some of the above referenced 
prior art disclose the use of reflective surfaces mounted beneath the 
array of semiconductor devices to further concentrate the beam emanating 
from these diodes. 
Therefore, there is a particular need for a light emitting diode lamp that 
provides a source of radiant energy that is uniformly distributed 
spherically, encompassing all directions so that it can be viewed in any 
direction, from any circumferential angle, at any angle of elevation. 
In this regard, this invention fulfills this need. 
SUMMARY OF THE INVENTION 
In the past, previously designed LED lamps were designed for directional 
lamp usage. The directional lamps found particular application as 
indicator panel lamps that have a primary concentration of visible light. 
A specialized need was then encountered for a light emitting diode that is 
nondirectional and that can be viewed 360 degrees in all three orthogonal 
planes. The demand was initiated by the requirement for replacement lamps 
in exit signs. 
The first attempt used by the designers were to use a diffusion glass to 
eliminate the illumination hot spots, when conventional directional LED 
lamps were used in exit sign applications. At that time no attempt was 
made to improve or change the LED lamp, the only change was to add a 
diffuser. 
The present invention details the manner in which these semiconductor chips 
are mounted within the encapsulated transparent envelope. Instead of the 
lamp projecting light into a narrow angled beam, this novel light emitting 
diode provides a uniformly distributed light that radiates spherically 360 
degrees in all directions, both radially and axially. This newly designed 
lamp is ideally suited as a source of illumination for exit sign 
applications. When used in this manner, the need for a diffusion surface 
is obviated. 
To accomplish the primary objective of having a LED lamp that radiates 
light uniformly in a 360 degree spherical pattern, the conventional 
hemispherical lens or the conventional flat surface lens is removed from 
the body of the cylindrically rod shaped envelope. These lens arrangements 
are then replaced with a newly designed lens that is concave to allow a 
focal point within the body of the cylinder. When used in conjunction with 
a reflector behind the semiconductor chips, the emitted light pattern is 
restricted to a hemispherical shaped pattern, having 360 degrees about the 
central axis of the cylindrically shaped rod and 180 degrees extending 
forward from the semiconductor chips. 
To complete the design of an LED lamp that radiates light uniformly in a 
360 degree spherical pattern, the reflector is removed and the 
semiconductor chips are secured to the anode first electrode. It was found 
that the optimal angle of depression is in the range from greater than 90 
degrees to less than 135 degrees, as measured from a cylinder side wall, 
to allow a focal point within the transparent encapsulating envelope. With 
the focus being at this point the light energy that emanates is increased, 
thereby improving the efficiency of operation with a greater lamp 
intensity. 
In the preferred embodiment, the concave lens is ideally a conical shaped 
depression, having an angle of 105 degrees as measured from the cylinder 
side wall. Using this type of lens structure gives a well focused 
pin-point of light that re-radiates the optical light energy. As such, the 
preferred angle circumscribed from the focal point to the envelope side 
wall is 45 degrees. 
In an alternate embodiment, a dished concave or concave hemispherical lens 
can be used. However, when using this arrangement, it does not provide the 
sharply defined focal point. 
In another aspect of the present invention, conventional LEDs are available 
in a variety of colors, such as, red, green, amber, orange and blue. By 
specifically selecting the red coloration in the manufacture and assembly 
of the present invention, it can find suitable application in use in exit 
signs, which are notably red in color. By using the present invention in 
this application, the need for a red filter and a diffuser that are 
conventionally used in exit signs is eliminated. 
Accordingly, it is a principal object of the present invention to provide a 
light emitting diode that has a uniform distribution of radiant light 
energy that is nondirectional and can be viewed 360 degrees in all three 
orthogonal planes. 
It is another object of the present invention to provide a light emitting 
diode that has a uniform distribution of radiant light energy that 
emanates from its focal point that is established by its newly designed 
concave lens structure. 
It is still another object of the present invention to provide a light 
emitting diode that has a uniform distribution of radiant light energy by 
having reflectorless operation. 
It is a further object of the present invention to provide a light emitting 
diode that has a uniform distribution of radiant light energy so that it 
can be viewed from any direction, both from the radial and axial 
directions. 
It is still another object of the present invention to provide a light 
emitting diode that has a concave lens to focus the radiated light energy 
into a secondary point source to re-radiate the visible light energy It is 
yet another object of the present invention to provide a light emitting 
diode that has a concave lens that has a conical shape to focus the 
radiated light energy into a secondary point source to re-radiate the 
visible light energy. 
It is still yet another object of the present invention to provide a light 
emitting diode that has the LED semiconductor chip mounted directly to the 
electrode without the further use of a reflective means of concentrating 
the emission into a directional beam of light energy. 
An additional object of the present invention to provide a light emitting 
diode that eliminates the need for a reflective means to concentrate the 
emitted light energy for the purpose of directing the beam forward in a 
cone shaped beam. 
It is a final object of the present invention to provide a light emitting 
diode that supplies diffused lighting emission for use in exit signs and 
display panel applications. 
These and other advantages of the present invention will become more 
apparent upon further reading of the detailed specification. It should be 
understood that deviations or modifications can be made without deviating 
or departing from the spirit of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An interim embodiment is shown in FIGS. 5 and 6, where the viewing angle is 
180 degrees. With reference to FIG. 5, illustrated is a sectional view of 
a LED lamp having one or more semiconductor chips 150. The transparent 
envelope 20 of the cylindrical shaped rod 14 has a concave conical shaped 
lens 32. The semiconductor chip 150 is mounted to the conductive surface 
of the first electrode, the LED anode 110, which is recessed within the 
convex reflector 140. A fine wire 130 connects the opposite end of the 
semiconductor chip 150 to the second electrode 120. As shown in FIG. 6, 
the light that emanates from the semiconductor chips is projected on the 
concave conical shaped lens 22, that is integral to the end of a 
cylindrically shaped rod envelope 14. It uses one or more semiconductor 
chips 150 mounted within a reflective surface 140 giving 180 degrees of 
viewing visibility. Alternatively, the lens 32 may be a separate piece 
that is fixed to the envelope 14. 
Reference is directed to FIGS. 7 and 8 for disclosure of the preferred 
embodiment of the present invention. FIG. 7 is a sectional view of a 
semiconductor light emitting device of the preferred embodiment of the 
present invention. 
With reference to the sectional view of FIGS. 7 and 8, the entire light 
emitting diode is referenced as numeral 40. The body of the light emitting 
device 14 fully encapsulates all the components contained within the LED. 
The concave lens 32 is a newly designed configuration comprised of a 
conical shaped concave lens that focuses the emitted light from the 
semiconductor device 150 onto the focal point 230. 
I have found that the optimal angle of depression is in the range from 
greater than 90 degrees to 135 degrees, as measured from a cylinder side 
wall 44. Such angle of depression positions a focal point 230 within the 
transparent encapsulating envelope 40. The focal point thus formed 
provides increased light energy that emanates from within the LED body 14, 
thereby improving the efficiency of operation with a greater lamp 
intensity. 
In the preferred embodiment, the concave lens is ideally a conical shaped 
depression, having an angle of 105 degrees as measured from the cylinder 
side wall 44, whereby the angle circumscribed at the focal point or vertex 
of the conical lens to the side wall is 45 degrees. Using this type of 
lens structure gives a well focused pin-point of light at the that 
re-radiates the optical light energy. The conical shape of lens 32 further 
provides a curved surface or nappe 34 of the cone which serves as a 
reflector and refractor and as such, light is propagated from the focal 
point 230 and also from the surface or nappe 34 of lens 32. 
The semiconductor chip(s) 140 are mounted to the second electrode, the 
cathode, 110. A fine wire 130 connects the semiconductor chip 140 to the 
first electrode, the anode 120. 
In typical operation, the highly visible region 200 broadly encompasses the 
entire volume circumscribing the light emitting diode. Only the small 
region 210 has a cone of light of diminished intensity. The region 220 is 
of greater intensity than region 210 and is slightly less intense than the 
region 200. 
In an alternate embodiment, as shown in FIG. 9, the LED body 14 has a 
concave lens 52 that is hemispherically shaped. It is asymptotic at a 
preferred angle of 105 degrees. 
Still, in another aspect of the present invention, by using a red color 
chip in the manufacture and assembly of the present invention, it can find 
application in use in exit signs, which are notably red in color. By using 
the present invention in this application, the need for a red filter and a 
diffuser that are conventionally used in exit signs is eliminated. 
While specific embodiments of the present invention have been shown and 
described in detail to illustrate the principles of the invention, it 
should be understood by those skilled in the art, that other modifications 
or embellishments can be made without departing from the true spirit of 
the invention and equivalents of the following claims.