Title:
CONDENSER SYSTEM FOR HIGH INTENSITY LIGHT SOURCE
United States Patent 3702395
Abstract:
An elliptical mirror is utilized in combination with a xenon arc projection lamp and a high melting point metal stop to provide in one embodiment an improved vertical axis point light source for point light source projectors, and in another embodiment to provide a condensed, vertical axis beam which is annular in section for panoramic projectors using transparencies having an azimuthal scene recorded in annular form.
US Patent References:
AUTOMOTIVE HEADLIGHT
Biggs - August 1971 - 3598989
Method and apparatus for registering negatives with printing surfaces
Kanolt - December 1931 - 1838312
APPARATUS FOR GENERATING FINE LINE,DISCRETE TRACKS
Ucko et al. - July 1969 - 3457012
Solar simulator
Miles et al - May 1967 - 3321620
/1279638.html
Blake - September 1918 - 1279638
AUTOMOTIVE HEADLIGHT
Biggs - August 1971 - 3598989
Method and apparatus for registering negatives with printing surfaces
Kanolt - December 1931 - 1838312
APPARATUS FOR GENERATING FINE LINE,DISCRETE TRACKS
Ucko et al. - July 1969 - 3457012
Solar simulator
Miles et al - May 1967 - 3321620
/1279638.html
Blake - September 1918 - 1279638
Application Number:
05/079416
Publication Date:
11/07/1972
Filing Date:
10/09/1970
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
353/102, 353/97
International Classes:
F21V13/04; F21V13/00; F21V13/04
Field of Search:
240/41.3,41.35,41 353/55,56,97,100,102 355/78,133
US Patent References:
| 3174067 | Construction for projection lamps eliminating undesired infrared radiation | March 1965 | Bahrs | |
| 3078760 | Optical projection system | February 1963 | Brownscombe | |
| 3241440 | Illumination system | March 1966 | Kugler | |
| 2338901 | Vehicle lamp | January 1944 | Chiti | |
| 3371202 | Medical headlight | February 1968 | Moore et al. | |
| 3590239 | RADIATION CONDENSERS | June 1971 | Bernard |
Other References:
"That Important Optical Train", International Projectionist, Vol. 32, No. February 1957.
Primary Examiner:
Matthews, Samuel S.
Assistant Examiner:
Sheer, Richard M.
Claims:
What is claimed is
1. In a vertical axis condenser system for use with a high intensity light source such as a xenon arc lamp:
1. In a vertical axis condenser system for use with a high intensity light source such as a xenon arc lamp:
Description:
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
Various projection and display devices require a high intensity light source. One commonly used high intensity light source is the xenon "arc" lamp. Use of the xenon arc projection lamp has been limited to use with condenser arrangements wherein the direction of light propagation from the projector is generally horizontal. The construction of xenon projection lamps is characterized by a glass envelope having a bulbous central portion and diametrically opposed tubular portions extending therefrom. Tungsten electrodes define a gap within the bulbous portion of the envelope while elongated electrode supporting and conductive leads extend in opposite directions through the tubular portions. The electrodes, gap, and electrode supporting leads all lie on a common axis. These lamps are required to be operated with the axis of the electrodes disposed in a vertical or nearly vertical position.
Operating the lamps with the electrode axis vertical is satisfactory for applications using condenser systems following the conventional approach wherein the condensed light beam axis is in a horizontal direction. There are, however, applications which require a condensed light beam which has a vertical axis. The requirement of a vertical light beam axis contradicts the usual requirement that a xenon arc lamp be burned with the electrode axis vertical, provided the condenser system follows the conventional approach. It will be appreciated that this is so inasmuch as the tubular portions of the envelope, as well as the electrode supports or leads and the electrodes themselves, obstruct the efficient emission of light in a vertical sense.
Additionally, light sources such as the xenon arc lamp are generally characterized by light emission from a rather small luminous area; and within this area the luminance is strongly non-uniform. These characteristic features are contrasted by, for instance, the pure carbon or high intensity (so called Beck) arc lamp and require special attention in the form of carefully adapted condenser systems, in order to utilize the light to the highest possible degree without compromising uniformity of screen illumination within acceptable standards. Xenon arc lamps have been used to some degree in combination with an elliptical reflector in schlieren projection systems. In those systems, typified by the conventional projection system produced by the Dojun Koki Co. of Japan, it is desired to provide even illumination over a relatively wide field, whereas the instant invention is concerned mainly with a combination which will provide an effective point light source.
In the art of simulators and trainers there is a need for high intensity light source and condenser systems which can efficiently provide light propagation in a vertical sense, either upwardly or downwardly. One such need is in a point light source vertical projection system (see U.S. Pat. No. 3,135,160 for a horizontally oriented point light source system). Another is in conjunction with a panoramic or around the horizon projection system utilizing an annular transparency and requiring a vertical axis condenser system and illumination of a cone between 25° and 85° from the condenser axis.
SUMMARY OF THE INVENTION
With the foregoing in mind, it is a principal object of this invention to provide, in combination with a projection lamp (such as a xenon lamp) which requires burning in an approximately vertical position, a condenser system which will utilize the light emitted around the entire equatorial zone and brought out in the direction of the longitudinal axis of the lamp, that is in a vertical direction.
As another object the present invention aims to provide an improved light source or condenser arrangement utilizing a generally elliptical mirror having a central opening for accommodating a vertically extending, elongated portion of a projection lamp, the mirror having first and second focal points along the vertical axis thereof, the light emitting portion of the lamp being centered at the first focal point, and a stop or lens being located at the second focal point.
Still another object of this invention is the provision of a light source and condenser of the foregoing character which is relatively simple and inexpensive to manufacture and to align or adjust, and which compensates for a rather large source of emission and which is aspherical in shape.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying sheet of drawings forming a part of this specification, and in which:
FIG. 1 is a diagrammatic illustration of an improved, vertical axis condenser system embodying the present invention, showing the same as used in conjunction with a point light source projection system;
FIG. 2 is a graphical illustration showing the relationship between a stop element of the system of FIG. 1 and the illumination in the plane of that stop element; and
FIG. 3 is a diagrammatic illustration of another embodiment of the invention as used with panoramic projection system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the form of the invention which is illustrated in FIG. 1 in association with a point light source projection system 10, there is provided a xenon arc projection lamp 12. The lamp 12 is of conventional construction including a transparent envelope 14 having diametrically opposed tubular portions 14a, 14b having their long axes arranged vertically, or substantially so. These axes may be said to define the vertical axis 15 of the lamp 12. A tungsten electrode or anode 16 is supported by a lead 18 which extends vertically through the tubular portion 14a. A tungsten electrode or cathode 20 is supported by a lead 22 which is axially aligned with the lead 18 and extends through the tubular portion 14b. The envelope is filled with the gas xenon at a number of atmospheres pressure. Upon an appropriate starting pulse, and thereafter with a direct current voltage on the order of 200 volts applied via lines L 1 and L 2 across the leads 18 and 22, a bell shaped arc A is established and maintained between the electrodes 16 and 20. The arc A emits an intense white light, suitable for projection, through the side walls of the envelope 14.
Surrounding the projection lamp 12 is an elliptical concave mirror 30 having an inner reflecting surface 32 which constitutes a portion of a surface of revolution about an axis which is coincident with the vertical axis 15 of the lamp 12. The elliptical mirror 30 has a central aperture or opening 34 through which the bulb portion 14a extends and is configured so that a first focal point F 1 thereof is located at the center of the arc A, while the second or remote focal point F 2 is located along the axis 15 at a substantial distance below the lamp 12.
There results from the aforedescribed combination of the lamp 12 and the elliptical mirror 30 a conical zone of occlusion which subtends an angle a, and a zone of illumination which subtends a maximum angle b. The elliptical mirror 30 is selected to have the focal point F 2 far enough down the axis 15 that the ratio of the angle a to the angle b is approximately as 25 is to 85, or 0.295.
The rays 40 emanating horizontally from the arc A will be anastigmatic in their reflection and mergence at the remote focal point F 2 . These rays may be considered the central or chief rays of the unoccluded part of the illumination cone. The resulting image of the arc A, if formed by the chief rays 40 alone, would also be free of spherical aberrations. However, rays outside the chief rays, such as rays 42 and 44, will be subject to astigmatism. There will also be coma present in the image at F 2 . These aberrations may be compensated for in the lens system 46 which serves principally to render a reduced and better defined image A' of the arc A, which will better serve as essentially a pin-point light source for projecting a scene, recorded on a transparency 48, through the projection system 10. The lens system 46 follows well known principles for a lens triplet and need not be described in detail.
In order to prevent stray light from entering the system and degrading the quality of the image A', an aperture 50 of diameter D is defined by a stop member 52 arranged in the plane of the focal point F 2 . Since a large amount of heat is produced at F 2 , the stop member 52 is advantageously formed of a high melting point metal such as tantalum or titanium. As is illustrated by curve 54 in FIG. 2 the intensity of illumination in the plane of the stop member 52 and second focal point F 2 is characterized by a plateau, the width of which is determinative of the diameter D of the aperture 50.
A particular advantage of the described system over a conventional imaging system is that the light distribution in the image at F 2 has rotational symmetry, thus overcoming the conventional strong non-uniformity of the arc image in a conventional system.
Referring now to FIG. 3, in which reference numerals corresponding to those in the foregoing description identify corresponding parts, there is illustrated another embodiment of the invention which is shown in conjunction with panoramic projection means including a transparency 60 and panoramic projection optics 62. The transparency 60 and optics 62 form no part of the invention per se. Suffice it to say that in the projection system with which this embodiment of the invention is most advantageously used, the transparency 60 comprises an azimuthal scene recorded in annular form, and when properly illuminated the optics 62 project the scene onto a suitably curved screen 64.
In this embodiment, the lamp 12 and elliptical mirror 30 are substantially the same as described earlier. However, the lens means 46 and stop member 52 are replaced by a negative lens means 68 deployed ahead of the focal point F 2 . The lens means 68 serves to defocus the converging rays represented by 40, 42, and 44 and to form them into parallel rays. The resulting light constitutes a condensed beam 70 of light which is annular in section in that it surrounds a central occluded zone 72.
Again, stray light is excluded by an aperture 74 defined by a stop member 76. The light beam 70 of annular section is of a size to correspond to the annularly recorded scene on the transparency 68, thereby obtaining the most efficient use of the light output of the lamp 12.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
Various projection and display devices require a high intensity light source. One commonly used high intensity light source is the xenon "arc" lamp. Use of the xenon arc projection lamp has been limited to use with condenser arrangements wherein the direction of light propagation from the projector is generally horizontal. The construction of xenon projection lamps is characterized by a glass envelope having a bulbous central portion and diametrically opposed tubular portions extending therefrom. Tungsten electrodes define a gap within the bulbous portion of the envelope while elongated electrode supporting and conductive leads extend in opposite directions through the tubular portions. The electrodes, gap, and electrode supporting leads all lie on a common axis. These lamps are required to be operated with the axis of the electrodes disposed in a vertical or nearly vertical position.
Operating the lamps with the electrode axis vertical is satisfactory for applications using condenser systems following the conventional approach wherein the condensed light beam axis is in a horizontal direction. There are, however, applications which require a condensed light beam which has a vertical axis. The requirement of a vertical light beam axis contradicts the usual requirement that a xenon arc lamp be burned with the electrode axis vertical, provided the condenser system follows the conventional approach. It will be appreciated that this is so inasmuch as the tubular portions of the envelope, as well as the electrode supports or leads and the electrodes themselves, obstruct the efficient emission of light in a vertical sense.
Additionally, light sources such as the xenon arc lamp are generally characterized by light emission from a rather small luminous area; and within this area the luminance is strongly non-uniform. These characteristic features are contrasted by, for instance, the pure carbon or high intensity (so called Beck) arc lamp and require special attention in the form of carefully adapted condenser systems, in order to utilize the light to the highest possible degree without compromising uniformity of screen illumination within acceptable standards. Xenon arc lamps have been used to some degree in combination with an elliptical reflector in schlieren projection systems. In those systems, typified by the conventional projection system produced by the Dojun Koki Co. of Japan, it is desired to provide even illumination over a relatively wide field, whereas the instant invention is concerned mainly with a combination which will provide an effective point light source.
In the art of simulators and trainers there is a need for high intensity light source and condenser systems which can efficiently provide light propagation in a vertical sense, either upwardly or downwardly. One such need is in a point light source vertical projection system (see U.S. Pat. No. 3,135,160 for a horizontally oriented point light source system). Another is in conjunction with a panoramic or around the horizon projection system utilizing an annular transparency and requiring a vertical axis condenser system and illumination of a cone between 25° and 85° from the condenser axis.
SUMMARY OF THE INVENTION
With the foregoing in mind, it is a principal object of this invention to provide, in combination with a projection lamp (such as a xenon lamp) which requires burning in an approximately vertical position, a condenser system which will utilize the light emitted around the entire equatorial zone and brought out in the direction of the longitudinal axis of the lamp, that is in a vertical direction.
As another object the present invention aims to provide an improved light source or condenser arrangement utilizing a generally elliptical mirror having a central opening for accommodating a vertically extending, elongated portion of a projection lamp, the mirror having first and second focal points along the vertical axis thereof, the light emitting portion of the lamp being centered at the first focal point, and a stop or lens being located at the second focal point.
Still another object of this invention is the provision of a light source and condenser of the foregoing character which is relatively simple and inexpensive to manufacture and to align or adjust, and which compensates for a rather large source of emission and which is aspherical in shape.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying sheet of drawings forming a part of this specification, and in which:
FIG. 1 is a diagrammatic illustration of an improved, vertical axis condenser system embodying the present invention, showing the same as used in conjunction with a point light source projection system;
FIG. 2 is a graphical illustration showing the relationship between a stop element of the system of FIG. 1 and the illumination in the plane of that stop element; and
FIG. 3 is a diagrammatic illustration of another embodiment of the invention as used with panoramic projection system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the form of the invention which is illustrated in FIG. 1 in association with a point light source projection system 10, there is provided a xenon arc projection lamp 12. The lamp 12 is of conventional construction including a transparent envelope 14 having diametrically opposed tubular portions 14a, 14b having their long axes arranged vertically, or substantially so. These axes may be said to define the vertical axis 15 of the lamp 12. A tungsten electrode or anode 16 is supported by a lead 18 which extends vertically through the tubular portion 14a. A tungsten electrode or cathode 20 is supported by a lead 22 which is axially aligned with the lead 18 and extends through the tubular portion 14b. The envelope is filled with the gas xenon at a number of atmospheres pressure. Upon an appropriate starting pulse, and thereafter with a direct current voltage on the order of 200 volts applied via lines L 1 and L 2 across the leads 18 and 22, a bell shaped arc A is established and maintained between the electrodes 16 and 20. The arc A emits an intense white light, suitable for projection, through the side walls of the envelope 14.
Surrounding the projection lamp 12 is an elliptical concave mirror 30 having an inner reflecting surface 32 which constitutes a portion of a surface of revolution about an axis which is coincident with the vertical axis 15 of the lamp 12. The elliptical mirror 30 has a central aperture or opening 34 through which the bulb portion 14a extends and is configured so that a first focal point F 1 thereof is located at the center of the arc A, while the second or remote focal point F 2 is located along the axis 15 at a substantial distance below the lamp 12.
There results from the aforedescribed combination of the lamp 12 and the elliptical mirror 30 a conical zone of occlusion which subtends an angle a, and a zone of illumination which subtends a maximum angle b. The elliptical mirror 30 is selected to have the focal point F 2 far enough down the axis 15 that the ratio of the angle a to the angle b is approximately as 25 is to 85, or 0.295.
The rays 40 emanating horizontally from the arc A will be anastigmatic in their reflection and mergence at the remote focal point F 2 . These rays may be considered the central or chief rays of the unoccluded part of the illumination cone. The resulting image of the arc A, if formed by the chief rays 40 alone, would also be free of spherical aberrations. However, rays outside the chief rays, such as rays 42 and 44, will be subject to astigmatism. There will also be coma present in the image at F 2 . These aberrations may be compensated for in the lens system 46 which serves principally to render a reduced and better defined image A' of the arc A, which will better serve as essentially a pin-point light source for projecting a scene, recorded on a transparency 48, through the projection system 10. The lens system 46 follows well known principles for a lens triplet and need not be described in detail.
In order to prevent stray light from entering the system and degrading the quality of the image A', an aperture 50 of diameter D is defined by a stop member 52 arranged in the plane of the focal point F 2 . Since a large amount of heat is produced at F 2 , the stop member 52 is advantageously formed of a high melting point metal such as tantalum or titanium. As is illustrated by curve 54 in FIG. 2 the intensity of illumination in the plane of the stop member 52 and second focal point F 2 is characterized by a plateau, the width of which is determinative of the diameter D of the aperture 50.
A particular advantage of the described system over a conventional imaging system is that the light distribution in the image at F 2 has rotational symmetry, thus overcoming the conventional strong non-uniformity of the arc image in a conventional system.
Referring now to FIG. 3, in which reference numerals corresponding to those in the foregoing description identify corresponding parts, there is illustrated another embodiment of the invention which is shown in conjunction with panoramic projection means including a transparency 60 and panoramic projection optics 62. The transparency 60 and optics 62 form no part of the invention per se. Suffice it to say that in the projection system with which this embodiment of the invention is most advantageously used, the transparency 60 comprises an azimuthal scene recorded in annular form, and when properly illuminated the optics 62 project the scene onto a suitably curved screen 64.
In this embodiment, the lamp 12 and elliptical mirror 30 are substantially the same as described earlier. However, the lens means 46 and stop member 52 are replaced by a negative lens means 68 deployed ahead of the focal point F 2 . The lens means 68 serves to defocus the converging rays represented by 40, 42, and 44 and to form them into parallel rays. The resulting light constitutes a condensed beam 70 of light which is annular in section in that it surrounds a central occluded zone 72.
Again, stray light is excluded by an aperture 74 defined by a stop member 76. The light beam 70 of annular section is of a size to correspond to the annularly recorded scene on the transparency 68, thereby obtaining the most efficient use of the light output of the lamp 12.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.