Infrared beam projector

An infrared beam shaper able to emit a beam of infrared light having a specified shape within a predetermined distance is disclosed. It is comprised of a cluster of hollow cylindrical tubes, a source positioned at a first end of each tube and an aperture located at a second end of each tube. Each tube is positioned in the cluster arrangement with their apertures located adjacent each other and each tube has a light absorbing liner extending along each tube from the first end to the second end. Most light emitted by the source which diverges away from the central horizontal axis defined by the tube before the second end will be absorbed by the liner and any remaining light will be emitted through the aperture.

FIELD OF THE INVENTION 
This invention relates to an infrared emittors and receivers and more 
particularly to an infrared beam shaper. 
DESCRIPTION OF THE PRIOR ART 
Emittors of infrared light along with infrared receivers have long been 
used in a number of applications. For example, various audio and video 
remote controls use infrared light as a means for controlling a main unit. 
These remote controls are found and used for operating and controlling 
televisions, video records, garage door openers, toy games, etc. 
However, the overall aiming capability of the emittors in most of these 
applications is fairly limited, since the density and accuracy of the beam 
deteriorates with the distance. In most applications, a photo diode 
detector receiver circuit will only turn on when it receives a certain 
minimum intensity of infrared radiation. Accordingly, most remote control 
emittors are usable for only a short range from the detector since the 
energy emitted from the source will diverge and the useful power output 
will decrease substantially as the distance increases. 
This is due to the fact that energy from a point source of sound or light 
emitting harmonic waves in three dimensions will spread out equally in all 
directions. At a distance R from the source, the energy is uniformly 
distributed on a sphere of area 4.pi.R.sup.2. The intensity (average 
energy per unit area per unit time) thus decreases as 1/R.sup.2. That is, 
the intensity of say a infrared light beam, decreases in intensity by one 
over the square of the distance from the source. 
There is therefore a requirement for an infrared beam projector or shaper 
which is able to project a beam over a defined range, which the projected 
beam of infrared light has a constant minimum intensity over a defined 
range. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an infrared 
beam shaper which is able to project over a defined range, a shaped beam 
(e.g. cylindrical) of infrared light having a constant minimum intensity 
over the pre-defined range (intensity within the beam varies from minimum 
to greater than minimum). 
Yet another object of the present invention is to provide an infrared beam 
shaper in which most diverging light emitted from a source in the shaper 
will be absorbed and a smaller beam angle of diverging light will be 
emitted from the beam shaper. 
Accordingly, it is an aspect of the present invention to provide a light 
beam projector, comprising: 
a hollow cylindrical tube; 
a light source positioned one end of said tube; and 
an aperture located at the opposite end of said tube, said tube having a 
light absorbing liner extending along said tube from said light source to 
said aperture, such that most light emitted by said light source which 
generally diverges away from a central horizontal axis defined by said 
tube, before said aperture, will be absorbed by said liner and any 
remaining light will be emitted through said aperture. 
According to a second aspect of the present invention, there is provided a 
light beam shaper able to project a beam of light having a specified shape 
as desired within a predetermined distance, comprising: 
a cluster of hollow cylindrical tubes; 
a light source positioned at a first end of each tube; and 
an aperture located at a second end of each tube, opposite said first end, 
each tube being positioned in said cluster with their apertures located 
adjacent each other and each tube having a light absorbing liner extending 
along each tube from first end to said second end, such that most light 
emitted by said source which diverges away from a central horizontal axis 
defined by said tube, before said second end, will be absorbed by said 
liner and any remaining [non-diverging]light will be emitted through said 
apertures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, we have shown generally at reference numeral 10, 
the basic configuration of the infrared beam projector of the present 
invention. The projector is comprised of three pairs of cylindrical 
acrylic plastic tubes fastened to a frame tube 11 in a circular cluster. 
This cluster is comprised of a series of pairs of tubes having varying 
lengths adapted to emit short, medium and long range light beams. Short 
tubes 12 will emit a light beam having a relatively short range, medium 
length tubes 13 will emit a light beam having a medium range and long 
tubes 14 will emit a beam having a longest range. Each type of tube is 
arranged in pairs around frame tube 11, to form a cluster arrangement. 
Tubes 12, 13 and 14 are provided with a light source 12A, 13A and 14A 
located at one end of the tubes. Similarly, tubes 12, 13 and 14 are 
provided with apertures 12B, 13B and 14B respectively. These tubes are 
positioned in a circular cluster arrangement with their apertures located 
adjacent to each other. 
Referring now to FIG. 2, we have shown a cross-sectional view of a tube 
used in the cluster arrangement of FIG. 1. Each tube is comprised of a 
hollow cylindrical body 20. This body can consist of an acrylic plastic 
tube or other similar material. A light source 21 is located at a first 
end of body 20 and includes a light emitting diode 22 having connecting 
leads 23. Light emitting diode 22 is attached to body 20 by means of a 
cylindrical shaped insert 24 having a cavity 25 adapted to receive the 
light emitting diode 22. Located at its second end, opposite the first 
end, is an aperture 26. Aperture 26 is comprised of a hollow cylindrical 
insert 27 having a predetermined interior diameter 28 forming a light 
aperture. Cylindrical insert 27 is adapted to be fixedly mounted in tube 
20. A light absorbing liner 29 is positioned on the interior surface of 
tube 20. Liner 29 extends entirely within the interior surface of tube 20 
from light source 21 to aperture 26. This light absorbing liner can be 
comprised of a rolled piece of black flock paper. Liner 29 is adapted to 
absorb most light emitted from light emitting diode 22 which diverges away 
from a central longitudinal axis defined by tube 20. Therefore, most light 
which diverges between source 21 and aperture 26 will be absorbed by liner 
29. Light emitting from aperture 28 will diverge but in a very narrow 
beam. 
The light beam pattern emitted from each tube is dependent upon a number of 
variables. These are: 
the type of infrared light emitting diodes; 
the amount of current passing through the light emitting diodes which 
affect the infrared radiation intensity; 
the length of each tube; and 
the aperture diameter. 
Any change in one or more of these variables will affect the pattern or 
shape of the output beam. 
It was found through experimentation, that a beam pattern such as shown in 
FIG. 3 could be produced. This beam pattern has a constant minimum 
intensity with a generally constant diameter at any point within a 
predefined range. 
With each pair of tubes, the light emitting diodes are connected in series. 
It was found that the use of three tube pairs in a cluster arrangement such 
as shown in FIG. 1, in which a first pair of tubes with a length of 2", a 
second pair of tubes with a length of 53/8" and a third pair of tubes with 
a length of 161/2" can provide a beam pattern such as shown in FIG. 3. 
Each tube has an aperture formed by aluminum insert with a 3/8" outer 
diameter and 1/4" long. Each aluminum insert is provided with a center 
hole having a diameter of 13/64" which forms the light aperture. Each tube 
has an outer diameter of 1/2" and an interior diameter 3/8". Such a 
cluster arrangement will create and emit, for a range of between 3' and 
45', a beam having a constant diameter of about 51/2" plus or -0.5". 
The long tubes were provided with infrared LED's with 15% 1/2 intensity 
beam angle whereas the remaining tubes were provided with infrared LED's 
with 50% 1/2 intensity beam angle. The LED's in the long tubes were fed 
with 750 milliamps of DC current, the medium size tubes were fed with 374 
milliamps of DC current and the short tubes were fed with 208 milliamps of 
DC current. 
The infrared receiver used in testing beam shaper had a receiver gain of 
35,000. 
It was found that an increase in a number of tubes provides a higher 
quality of the shape of the beam emitted from the beam shaper. It was 
found that other structural embodiments of the cluster arrangement of FIG. 
1 can also be provided. For example, three long tubes can be used along 
with two medium size tubes and one short tube. Also, three long tubes with 
two medium range tubes and two short range tubes can be used wherein one 
long tube is used to replace the center frame tube 11. In addition, 
although the preferred embodiment consists of a circular cluster of tubes, 
a rectangular arrangement would also be possible to use. 
The light absorbing liner could also comprise a rough surface cloth or a 
roughened card surface painted with flat black paint. 
Although the current beam shaper and projector are adapted for use with an 
infrared light emitting diode, other types of light emitting diodes such 
as those operating in the visible and invisible light spectrum can be used 
as well. 
As will be apparent to those skilled in the art in light of the foregoing 
disclosure, many alterations and modifications are possible in the 
practice of this invention without departing from the spirit or scope 
thereof. Accordingly, the scope of the invention is to be construed in 
accordance with the substance defined by the following claims.