Note: Descriptions are shown in the official language in which they were submitted.
D-83-1-076
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PROJECTION LAMP UNIT
TECHNICAL FIELD
The invention relates to incandescent lamp and glas6
reflector combinations, particularly for use in projection
~y~tem6 such as 16 mm. movie and slide projectors. The
invention has particular applica~ion in an overhead projector
system.
BACKGROUND
- A p~ojection lamp unit which forms part of a projection
system such a~ mentioned above generally includes a preformed
gla~s reflector and projection lamp (e.g. tungsten halogen).
- The reflector generally has an elliptical surface of revolution
with the lamp filament at or near the focal point for
concentrating a beam of light through the sy6tem' 6 various
elëment~ (e.g., film gate and as60ciated lens). Examples of
6uch lamp units are found in U.S. Patents, 3,789,212 and
3,761,170. In some unit~, the reflector ~urEace is smooth and
highly polished (specular) 60 a6 to maximize the controlled
energy directed through the system. The aforementioned U.S.
Patents 3,761,170 and 4,392,189 illu6tra~e such a smooth
surfaced reflector.
Although the smooth and highly polished reflector provides
sub6tantially maximum optical output, the resulting beam
p~ttern often tend~ to be non-uniform, creating what are termed
"hot spots" and thus re~ulting in degraded re601ution of the
projected image. In view of such non-uniformity of the beam
pattern, many present designs utilize a reflector surface that
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is completely diffu~e (e.g., containing peens or facets). In
this regard, see U.S. patent~ 3,825,7~2, 4,035,631 and
4,021,659, as well a~ British patent application No.
2,085,745~. Uo5. Patent 4,021,659 in particular illu~tra~es an
all--aceted projection lamp uni~ reflec~or presently employed
in some commercial projecting units.
Although the totally faceted reflector improves the
uniformity of ~he beam pattern in comparifion to all-specular
surfaced reflectors, there tends to be a significant light lo~s
using such a ~urface.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention to
provide an i~proved p~ojection lamp unit including a reflector
in which optical energy output and beam pattern uniformity are
optimized. Ip particular, the reflector of this invention, in
comparison with an ~ faceted reflector, provides improved
total optical output and smaller corner-to-corner differential,
which in tuLn implie6 improved light distribution at the edge
of the beam pattern on the screen receiving the image.
In accordance with one aspect of the invention, there is
provided a reflector and lamp combination comprising a
reflector having a concave (e.g., ellipsoidal) reflecting
surface and a lamp (e.g., tungsten halogen) positioned within
the cavity of the reflector. The reflecting surface i8
demarcated into alternately disposed radially extending
region~. These surface regions include a plurality (e.g., four
or five) of ~pecular stripes in combination with spaced regions
of facet~. The combination of stripes and face~ed region~
provides for optimization of ~otal optical output and beam
pattern uniformity. With particular comparison to the output
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of an all-faceted re~lector~ there ha~ been ~ound to be both
enhanced total lig~it ou~put in ~dition to ~ller
corner-to-corner differential, thereby resulting in better
illumination of ~he 6ubject ~creen.
5BRIEF DESCRIPTION OF THE DRAWING5
FIG. 1 is a perspec~ive view of a projection lamp unit in
accordance with a p~efer~ed embodiment of the present invention:
FIG. 2 is a front view of the projection la~p unit of
FIG. 1: and
10FIG. 3 is a side view, in section, of the invention as
taken along line 3-3 of FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
For a bet~er understanding o the present invention
together with other and further object~, advantages and
capabilities thereof, reference is made to the following
disclosure and appended claims in connection with the above
described drawings.
With reference to the drawings, there i~ illustrated a
projection lamp unit 10 in accordance with a preferred
embodiment of the present invention. Uni~ 10 is particularly
adapted for use within a projection system such as a slide or
16 mm. movie projector. Accordingly, projec~ion lamp unit 10
would be located within a suitable socket/holder assembly (not
shown) such a~ described and shown in the aforementioned U.S.
2~ patents 3,789,21Z or 3,761,170. Unit 10 includes a pres~ed
tmolded~ glass reflector 11 and an incandescent projection lamp
13 (in phantom in FIGS. 1 and 2) adapted to be located within
reflector 11 such as is clearly illustrated in FIG. 3. The
projection lamp 13 is preferably of the tungsten/halogen type
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D-8~-1-076
(such as one listed under ANSI code ELH) and produced and sold
by the asLign e of the present invention. This particular lamp
produces 300 watt~, i6 operable at normal line voltages, and
possesses an average life of 35 }lours. The envelope portion 15
of lamp 13 preferably includes a CC8 (coiled coil) tungsten
filament 17 (FIG. 3) which is electrically connected within the
lamp's press sealed end 19 (adjacent to envelope 15) to a pair
of contact pins 21 which project from the lamp envelope.
Filament 17 also may include a parallel (to the coil) support
wire 2~ which assists in maintaining (supporting3 the coiled
portion of the filament in the pos;tion shown within the lamp's
envelope. FIG. 3 also illustrates the molybdenum foil strips
22 which conductively interconnect the filament 17 with the
contact pins 21. The lamp 13 i6 activated when pins 21 are
connected to a suitable socket component (not shown) and the
corresponding projection system placed in operation.
As indicated previously, the preferred filament used in the
projection unit 10 is filament type CC~. However, the
projection unit may also employ other types of lamps described
hereina~ter, some oE wh;ch may utilize the filament type CC6.
Basically, the coiled coil poLtion 24' of the CC8 filament
6tructure extend~ along the optical axis (O~-OA) oP the
reflector while the coiled coil portion of a type CC6 filament
structure extends perpendicular to the optical axi~ of the
reflector. Both coiled coil portions are preferably located
(centered) at the reflector's focal point to assure optimum
output.
Other lamps suitable for use in the projecting unit 10
include those listed under ANSI codes ENH and EH~, said lamps
also produced and sole by the assignee of the present
invention. ENH lamps operate at normal line voltages and are
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capable of producing 250 watt6 over an average life of 175
hour~. ENX lamps ~ypically produce 360 watts, operate at 82
volt6, and are rated as having an average life of 75 hours~
Both ENH and ENX type lamp6 utilize a CC8 filament structure.
Still other lamp6 for use in unit 10 include those producing
from about 80 to 150 watts and o~erable at the relatively low
voltage ranges of between about 10 and about 2~ vol~s
(sometimes even lower). Lamps of this type typically use C6 Dr
CC6 filaments and have an average operating life of between 25
and 1000 hour~. These latter defined lamps are listed under
such ANSI code designation~ a~ EJA, EMJ, EJN, EJL, DED and
ELC. The contact pin~ 21 typically employed in tung~ten
halogen lamps of the variety described above are of molybdenum
or similar conductive material. Lamp 13 is retained in
position in reflector 11 using a suitable cement 25 (e.g.
Sauereisan) known in the industry.
The reflector 11 i~ preferably made of hardglass (e.g.,
boro-silicate~, and includes a forward (or front) concave
reflecting portion 23 and a hollow rear neck po~tion Z6
adjacent thereto. The reflecting portion 23 i~ depicted in the
drawing as having a peripheral rim portion 27. Reflecting
portion 23 is pre~erably elliptical or parabolic in
configuration and has a concave reflecting surface 30 that is
formed with alternately di~posed radially extending regions
~5 including a plurality of spaced, specular stripes 3Z which are
disposed in the ~tarlike pattern illustrated clearly in FIG.
2. The smooth, mirrorlike specular stripes 32 have defined
therebetween spaced region~ 34 each containing several
diffusing facets 35. As stated, the specular ~tripes 32 are
smooth and highly polished. The facets 35 of each region may
be in the form illustrated in ~he aforementioned U.S. Patent
4,021,659. Accordingly, each facet 35 may be ~ubstantially
flat or be curved convexly.
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A~ indicated in FIG. 2, a total of five 6paced radial
stripes 32 i~ ~m~lo~ed, in combin~ion with a 6imilar number of
faceted region6 34. Preferably, the width of each specular
6~ripe 32 is similar to the width of each radial row 31 of
facets (a total of five such rows occupying each facet region
3~). The preferred number of facet6 in each region i6 between
about fifty and eighty, and, as illustrated, the facet size~ in
each radial row, being tapered, are progressively larger as
they approach the forwardmo6t edge (facing the viewer in
FIG. 2) of the glass reflectorn Widthwise in degrees, each
specular stripe 32 occupies abou~ twelve degree6, as does each
radial row 31 of facet6 35. The internal diameter of ~he
reflector's front opening, in one example o~ the invention, was
about 1.68 inch. ~ccoLdingly, the width of each row 31 and
stripe 32 a~ thi~ edge was about 0.176 inch. The concave
reflecting surface 30 of reflecting portion 23 may be provided
with a dichroic mirror coating (not shown) on its interior
- surface to permit much of the heat generated by lamp 13 to pa6s
therethrough while ~till reflecting the lamp'~ visible light
output in a forward direction A. Such coatings are known in
the art and typically can withstand temperatures of 500
Celsius with no resultant shit in characteristic~.
Comparative tests have also been conducted to compare the
projector lamp reflector o~ the present invention with an
all-faceted reflector such as depicted in U.S. Patent
4,021,659. Lamps subjected to such photometric testing were
those li6ted under ANSI code ENX. At leafit 20 lamp6 of each
type were tested, each having the described CC8 filament
structure. White 6creen appearance tests were also conducted.
The photometric te~t6 in particular measured the projected
percent of light reaching the corners of the ~creen ~urface and
al~o the total light illuminating the screen surface. The
following re~ults were attained:
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AVG. TOTAL AVERAGE PERCENTAGE
LI~HT OF LIGHT TO CORNERS AVERAGE
~LuL`~Ns~ UL l.L UR LR ~IFFr'RENTIAL
Invention 691 49 48 48 46 4.5
5 All-Faceted
Reflector 685 48 49 51 52 6.9
It i~ understood that by UL is meant the percentage of
light measured at the upper ~eft of the screen, LL means lower
left, etc. ~y the term average differential i~ meant the
average of the maximum difference in corner percentage (worst
case scenario) for each unit. For example, if the maximum
percentage difference between any two corner~ in one unit was
4.0, this unit would be assigned said value. A low value, a6
indicated hexe, i6 deemed extremely significant and highly
desired in the industry to assure output uniformity. All such
readings were performed using photometric test kits known in
the art. Surpri6ingly, the~e re~ults were possible without
specific placement of the CC8 filament structure relative to
the ~tripetfacet locations. That is, these positive results
were attained regardles6 of location of the filament's coil
(29') and support wire (2~) relative to the stripe~facet
orientation.
From the above readings, it is seen that the to~al light
output of the reflector of the present invention is greater
than that of an all-faceted reflector such as depicted in
4,021,659, the corner percentage averages for both groups are
substantially the same, despite use of the invention's unique
specular stripes, and the average corner differential of the
reflector of the present invention i5 substan~ially smaller
than that of the compared all-faceted re1ector. This value
implies sound, even light distribution at the edge portion of
the beam pattern on the distant screen.
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A 3M model 213 overhead projector was u~ed to perform the
white screer~ test. T~ est ~?S m~de on a comparison basi~
be~ween the reflec~or of the present invention and the above
referenced all-faceted reflector. There was no perceivably
observed difference in appearance of light pattern between ~he
different lamps. The photometric di~play indicated that the
lamps of both type~ clearly 6ati6fied industry ~pecifications.
However, the lamp of the present invention posse~6ed highly
desired greater brightne66, a~ indicated abo~e.
While there has been shown and descri~ed what are at
present considered the preferred embodiments of the invention,
it will be obvious to those skilled in the art that ~arious
changes and modiEications may be made therein without departing
from the scope of the invention as defined by the appended
claims. For example, although five specular stripes and
associated facet region~ have been illustrated, it is
understood that a fewer or greater number of stripes (and facet
regions) may pe employed. It i6 preferred, however to ha~e on
the order of four or five separate stripes and ~acet regions,
with the number of each (whether Eour or five) being the same.
In addition, it is also possible to utilize specular stripe6 of
proportionally greater width than depicted in the drawings.
For example, a to~al o five stripe~ could still be utilized,
but each stripe could occupy about 24 degrees (approximately
~wice the width de6cribed above). Understandably, the
corresponding number of radial rows of facet6 in each.region
would be reduced.
.
