CA1245201A

CA1245201A - Projection lamp unit

Info

Publication number: CA1245201A
Application number: CA000464357A
Authority: CA
Inventors: Arnold E. Westlund, Jr.; Lawrence R. Fraley
Original assignee: GTE Products Corp
Current assignee: Osram Sylvania Inc
Priority date: 1983-10-03
Filing date: 1984-09-28
Publication date: 1988-11-22
Also published as: EP0136684A2; JPS6097543A; DE3465509D1; EP0136684B1; EP0136684A3

Abstract

PROJECTION LAMP UNIT

ABSTRACT

An improved projection lamp unit including a glass reflector having a concave reflecting surface and a tungsten halogen lamp positioned within the concavity of the reflector.
The concave reflecting surface of the reflector is provided with alternately disposed radially extending regions including a series of specular stripes in combination with alternately spaced regions of facets. Preferably four or five stripes and an associated four or five facet regions are provided.

Description

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

2~5~

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 L5%~

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.

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 ~Z~52~
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 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.

~Z~2~.

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:

2~

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.

r~

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.
.

Claims

WHAT IS CLAIMED IS:

1. A reflector and lamp combination comprising a reflector having a concave reflecting surface and an incandescent lamp positioned within the concavity of said reflector, said concave reflecting surface including therein a plurality of alternately disposed radially extending surface regions each including a plurality of individual facets, said regions alternating respectively with a plurality of specular stripes, the combination of said specular stripes and said facet regions providing optimization of total optical output and beam pattern uniformity.

2. The combination according to Claim 1 wherein the number of said regions of facets and said specular stripes is the same.

3. The combination according to Claim 2 wherein said number is on the order of four or five.

4. The combination according to Claim 1 wherein each of said facets is curved convexly.

5. The combination according to Claim 1 wherein each of said facets is substantially flat.

6. The combination according to Claim 1 wherein said lamp is a tungsten halogen lamp including therein a tungsten filament structure.

7. The combination according to Claim 6 wherein said tungsten filament structure comprises a coiled coil tungsten filament extending along the optical axis of the reflector and a substantially parallel support wire adjacent said coiled coil filament and spaced therefrom.

8. The combination according to Claim 7 wherein said filament is a coiled coil tungsten filament wherein the coil lies perpendicular to the optical axis of the reflector.

9. The combination according to Claim 1 wherein the width of each of said specular stripes is substantially similar to the width of each of said facets, said facets occupying a plurality of radial rows in each of said regions.

10. The combination according to Claim 9 wherein each of said specular stripes and each of said radial rows of facets possess a width that tapers to a maximum width at the periphery of the reflector.