CA1162972A - Ellipsoidal envelope for incandescent infra-red energy reflecting lamp - Google Patents
Ellipsoidal envelope for incandescent infra-red energy reflecting lampInfo
- Publication number
- CA1162972A CA1162972A CA000360404A CA360404A CA1162972A CA 1162972 A CA1162972 A CA 1162972A CA 000360404 A CA000360404 A CA 000360404A CA 360404 A CA360404 A CA 360404A CA 1162972 A CA1162972 A CA 1162972A
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- filament
- envelope
- foci
- electric lamp
- distance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K1/00—Details
- H01K1/28—Envelopes; Vessels
- H01K1/32—Envelopes; Vessels provided with coatings on the walls; Vessels or coatings thereon characterised by the material thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K1/00—Details
- H01K1/28—Envelopes; Vessels
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- Non-Portable Lighting Devices Or Systems Thereof (AREA)
- Lenses (AREA)
- Resistance Heating (AREA)
Abstract
ABSTRACT
An incandescent electric lamp having an ellipsoidal shaped envelope with a coating of a material thereon which trans-mits energy in the visible light range and reflects energy in the infrared range. The envelope has a major axis with two foci and an incandescent filament is provided which is mounted along said major axis with the two foci of the major axis of the ellipsoidal envelope located at spaced points along the filament, preferably between the end and one-half the distance of the center from each end of the filament, to reduce side and/or end aberration loses and to produce a more uniform temperature distribution along the length of the filament.
An incandescent electric lamp having an ellipsoidal shaped envelope with a coating of a material thereon which trans-mits energy in the visible light range and reflects energy in the infrared range. The envelope has a major axis with two foci and an incandescent filament is provided which is mounted along said major axis with the two foci of the major axis of the ellipsoidal envelope located at spaced points along the filament, preferably between the end and one-half the distance of the center from each end of the filament, to reduce side and/or end aberration loses and to produce a more uniform temperature distribution along the length of the filament.
Description
g7Z
ELLIPSOIDAL ENVELOPE FOR INC~NDESCENT
1 _ INFRA-RED_ENERGY REFLECTING LAMP
~ackground of the Invention The use of a visible transmit-ting infrared reflecting coating on the envelope of an incandescent lamp to reflect infrared energy back -to the filament to raise its operating temperature and thereby reduce the amount of energy consumed by the filament to a desired temperature is known. A typical approach is to use optically precise spherical envelopes and a compact filament which is located at the optical center of the envelope. A lamp of this type is shown in United States Patent 4,160,929, granted July 10, 1979, which is assigned to the : assignee of this invention. Using such an approach, energy savings in excess of 50~ with the coating of the foregoing patent in a spherical envelope is theoretically attainable. This 15 corresponds to an increase in luminous efficacy in excess of ~:~
about 2 times that attainable in a normal lamp operating at -the same filament temperature.
From a practical point of view, it is not possible to make either a point source or a spherical filament. In general, it 20 has been determined that an elongated filament, either coiled-coil or triple coiled which is either horizontally or vertically mounted with respect to a spherical envelope is the most practical embodi-ment of lamp to be made with an infrared reflecting coating.
However, when an optically precise spherical reflector is used in : 25 conjunction with a non spherical, such as an elongated, filament some of the radiation returned from the reflector on the envelope is lost due to aberra-tion a-t the ends of the filament. Once this radiation is lost on one reflection, it is essentially lost for all subse~uent reflections from the envelope reflective coating unless 30 some type of recovery mechanism is employed.
~ ~2~72 The present irvention relates to an improved incandescent lamp having a filament therein -in which the envelope is ellipsoidal in shape and has a coating for reflecting infrared energy emitted by the filament back toward the filament and for transmitting visible energy. The filament is elongated and mounted along the major axis of the ellipsoid of the envelope.
The foci of the envelope are located on the axis of the filament and at predetermined distances from each end of the filament to reduce side or end aberrational losses By using this approach, the aberrational losses can be reduced to-about half that of a sphere enclosing the same cylindrical filament. Also, the use of an ellipsoidal element concentrates the returned IR radiation at two points of predetermined distances from the ends of the filament rather than at a single point. This makes the temperature gradient more uniform.
It îs, therefore, an obiect of the present invention to provide an incandescent lamp whose envelope has an infrared reflective coating means in which the envelope is in the shape of an ellipsoid.
Another object is to provide an incandescent lamp with an ellipsoidal envelope having its foci lying along the axis of an elongated - filament.
A further object is to provide an incandescent lamp whose envelope is in the shape of the ellipsoid, with the ellipsoid design such that the two foci of the ellipsoid are located at a predetermined distance from each end of the filament.
According to a broad aspect of the invention there is provided an incandescent electric lamp comprising: an ellipsoidal shaped envelope having a base portion, said envelope defining a major axis on which is a pair of spaced focal points, an incandescent filament mounted within said envelope, means for supplying electrical energy to said filament to cause it to incandesce to produce energy in both the infrared and the visible range9 ~0 means for cooperating with said envelope to return to the filament a sub-stantial portion of the infrared energy produced by said filament and for ~ 162~72 transmitting therethrough a substantial portion of the visible range energy produced by said filament said filament being elongated, generally cylindrical and linear along its ma~or axis, at least as long as tlle dis-tance between the two foci of the major axis of the envelope~ and being mounted along the ma~or axis of the ellipsoidal envelope so that the two foci of the ellipsoid are located on the filament at spaced points therealong.
Other ob~ects and advantages of the present invention will become more apparent upon reIerence to the following specification and annexed drawings in which:
Figure 1 is an elevational view in section o~ a prior art incandescent lamp;
Figure 2 is a side vie~ of the lamp of Figure 1 illustrating the aberrational effects;
' ' :~
~ ~ ~2a~
1 Fig. 3 is an elevational view of an ellipsoidal envelope showing the principals of the invention; and Fig. 4 is a cross-sectional view of the lamp of Fig. 3 showing the placement of the f ilament.
Fig. 1 shows a type of prior art incandescent lamp 10.
The lamp includes an envelope 11 which is preferably of a desired optical shape, the illustrative shape being shown as being spheri-cal except at the base portion. The lamp has a mechanism for returning infrared (IR) energy produced by the filament upon in-candescence to the filament. The lamp 10 has coated on the major part o~ its spherical surface, either internally or externally, a coating 12 which is highly transparent ~o visible wavelength energy and highly reflective to IR wavelength energy. A suitable coating is described in the aoresaid U.S. Patent 4,160,929, granted July 10, 1979, and which is assigned to the same assignee. Other coatings can be used.
A filament 22 is mounted on a pair of lead-in wires 18, 20 held in an arbor or stem, 17. The lead-in wires 18,20 are brought out through the arbor to electrical contacts 14,16 on a base 13. Arbor 17 also has a tubulation (no~ shown) through which the interior of the lamp envelope is exhausted and filled, if desired, with a gas. Suitable gases are, for example, argon, a mixture of argon-nitrogen, or a high molecular weight gas, such as ` krypton. The lamp also can be operated as a vacuum type.
When voltage is applied to the lamp, the filament 22 incandesces and produces energy in both the visible and the IR range. The exact spectral distribution of the filament depends upon the resistance of the filament. Typical f ilament operating temperatures are in the range of from about 2650K to about 2900K, although operation at a temperature as low as 2000K and as high as 3050K can be used. As the filament operating temperature increases, the spectral distribution shifts further to the red, 1 i.e. it produces more infrared energyO
The coating 12, in combination with the optical shape of the lamp, serves to reflect back to the filament a substantial, and preferably as large a portion as possiblel i.e. about 85% or more, of the IR energy produced by the filament. When the energy is reflected back to the filament, it increases i~s operating tempera-ture and thereby decreases the power (wattage) required to operate the filament at this temperature.
Fig~ 2 shows how the aberrational effects from the ends of the filament are produced. This shows the lamp cross~section along the longitudinal axis of the envelope. For purposes of explanation, it is considered that the envelope is a closed sphere in this direction. Consider that ~he filament 22 has a length ~ and that the center of this filament C is located at the optical center of the spherical envelope. The filament also is in the general form of a cylinder having a diameter D. Con-sidering the rays which originate from one end O of the filament at a point off the axis as it incandesces, these rays are produced effectively at a variety of angles covering a spherical surface.
Two such rays Rl and R2 are shown which are given off at an angle which is substantially acute with respect to the axis of the filament. Two other rays Sl and S2 are shown which are produced at angle which is somewhat obtuse with respect to the longitudinal axis of the filamentO As shown, the image point for the rays Rl and R2 will be near the image point I2, which is outside of the filament, while the image points for the rays Sl and S2 will be near the image point Il, which is at the end of the filament. It can be shown that for all of the rays originating from the end point O that the image points for many of these rays lie in a region outside of the end of the filament opposite the end O. The infrared energy which is not re-imaged back onto the filament is lost unless recaptured.
1 A similar analysis can be made for the rays which are emitted from the end of the filament opposite 0. An analysis is presented below for calculating these end losses.
The total aberration losses arise from image distortion associated with the sides, or outside surface of the filament, as well as its ends. The losses from the sides occur because the filament geometry does not precisely conform to the shape of the envelope so that the wavefront of rays from the sides of the filament also does not exactly correspond to the envelope and there will be some aberration when they are reflected back to the filament.
It can be shown that the aberrational losses Lc from the sides of an elongated filament centered at the optical center of an optically precise sphere of radius R is as follows:
~ L = _L ~ ~c~
c 31J~ C ~t~ePre ) Where:
Q is the filament length R is the radius of the Eilament cylinder.
c is the surface area of the cylinder assumed for the diameter of the filament.
AE is the end area of the filament.
` Ec is the emissivity of the cylinder.
Ee is the emissivity of the end of the filament.
For a filament 1300mm long in an 80mm G 25 spherical glass enclosure for Ec equals 0.55 and an Ee is approxi-mately 1, the side losses Lc can be calculated to be about 3.1%. That is, this amount of infrared energy will not re-image onto the filament and will be lost.
Fig. 3 shows an ellipsoidal envelope made to reduce the end losses while Fig. 4 is a schematic elevational view to 1 that is, an ellipse is taken and rotated by 360 to produce the ellipsoid. The envelope has a base 13 with stem and tubulation.
The incandescent filament 22, which is preferably coiled-coil or triple coiled, is treated as a cylinder whose axis lies along the major axis of the ellipser The envelope 42 is coated, either on the interior or the exterior with the IR reflective and visible transmissive coating 12.
Referring to Fig. 4, the envelope 42 is designed with respect to the filament so that the location of the foci of the ellipse are positioned to minimize the sum of end and side aberra-tions. In an ellipsoid, rays emitted near one of the foci points located along the length of the filament will be reflected by the coating on the envelope wall back to companion points near the foci points on the opposite side, considering the center C as a dividing line, of the filament from which the ray is emitted.
Usually one internal reflection is required. However, the visible energy passes out through the coating, by an amount determined by the coating transmittance, on the first impingement of the coating.
Rays emitted from near the foci points have no aberraO
tion. However, there is still aberration at the ends of the filament due to distortion.
In an IR reflecting envelope, whether spherical or ellipsoidal, The image of a ray emitted from the end of the filament at an angle ~ with respect to the filament axis, forms at some distance S behind the opposite given by the e~uation
ELLIPSOIDAL ENVELOPE FOR INC~NDESCENT
1 _ INFRA-RED_ENERGY REFLECTING LAMP
~ackground of the Invention The use of a visible transmit-ting infrared reflecting coating on the envelope of an incandescent lamp to reflect infrared energy back -to the filament to raise its operating temperature and thereby reduce the amount of energy consumed by the filament to a desired temperature is known. A typical approach is to use optically precise spherical envelopes and a compact filament which is located at the optical center of the envelope. A lamp of this type is shown in United States Patent 4,160,929, granted July 10, 1979, which is assigned to the : assignee of this invention. Using such an approach, energy savings in excess of 50~ with the coating of the foregoing patent in a spherical envelope is theoretically attainable. This 15 corresponds to an increase in luminous efficacy in excess of ~:~
about 2 times that attainable in a normal lamp operating at -the same filament temperature.
From a practical point of view, it is not possible to make either a point source or a spherical filament. In general, it 20 has been determined that an elongated filament, either coiled-coil or triple coiled which is either horizontally or vertically mounted with respect to a spherical envelope is the most practical embodi-ment of lamp to be made with an infrared reflecting coating.
However, when an optically precise spherical reflector is used in : 25 conjunction with a non spherical, such as an elongated, filament some of the radiation returned from the reflector on the envelope is lost due to aberra-tion a-t the ends of the filament. Once this radiation is lost on one reflection, it is essentially lost for all subse~uent reflections from the envelope reflective coating unless 30 some type of recovery mechanism is employed.
~ ~2~72 The present irvention relates to an improved incandescent lamp having a filament therein -in which the envelope is ellipsoidal in shape and has a coating for reflecting infrared energy emitted by the filament back toward the filament and for transmitting visible energy. The filament is elongated and mounted along the major axis of the ellipsoid of the envelope.
The foci of the envelope are located on the axis of the filament and at predetermined distances from each end of the filament to reduce side or end aberrational losses By using this approach, the aberrational losses can be reduced to-about half that of a sphere enclosing the same cylindrical filament. Also, the use of an ellipsoidal element concentrates the returned IR radiation at two points of predetermined distances from the ends of the filament rather than at a single point. This makes the temperature gradient more uniform.
It îs, therefore, an obiect of the present invention to provide an incandescent lamp whose envelope has an infrared reflective coating means in which the envelope is in the shape of an ellipsoid.
Another object is to provide an incandescent lamp with an ellipsoidal envelope having its foci lying along the axis of an elongated - filament.
A further object is to provide an incandescent lamp whose envelope is in the shape of the ellipsoid, with the ellipsoid design such that the two foci of the ellipsoid are located at a predetermined distance from each end of the filament.
According to a broad aspect of the invention there is provided an incandescent electric lamp comprising: an ellipsoidal shaped envelope having a base portion, said envelope defining a major axis on which is a pair of spaced focal points, an incandescent filament mounted within said envelope, means for supplying electrical energy to said filament to cause it to incandesce to produce energy in both the infrared and the visible range9 ~0 means for cooperating with said envelope to return to the filament a sub-stantial portion of the infrared energy produced by said filament and for ~ 162~72 transmitting therethrough a substantial portion of the visible range energy produced by said filament said filament being elongated, generally cylindrical and linear along its ma~or axis, at least as long as tlle dis-tance between the two foci of the major axis of the envelope~ and being mounted along the ma~or axis of the ellipsoidal envelope so that the two foci of the ellipsoid are located on the filament at spaced points therealong.
Other ob~ects and advantages of the present invention will become more apparent upon reIerence to the following specification and annexed drawings in which:
Figure 1 is an elevational view in section o~ a prior art incandescent lamp;
Figure 2 is a side vie~ of the lamp of Figure 1 illustrating the aberrational effects;
' ' :~
~ ~ ~2a~
1 Fig. 3 is an elevational view of an ellipsoidal envelope showing the principals of the invention; and Fig. 4 is a cross-sectional view of the lamp of Fig. 3 showing the placement of the f ilament.
Fig. 1 shows a type of prior art incandescent lamp 10.
The lamp includes an envelope 11 which is preferably of a desired optical shape, the illustrative shape being shown as being spheri-cal except at the base portion. The lamp has a mechanism for returning infrared (IR) energy produced by the filament upon in-candescence to the filament. The lamp 10 has coated on the major part o~ its spherical surface, either internally or externally, a coating 12 which is highly transparent ~o visible wavelength energy and highly reflective to IR wavelength energy. A suitable coating is described in the aoresaid U.S. Patent 4,160,929, granted July 10, 1979, and which is assigned to the same assignee. Other coatings can be used.
A filament 22 is mounted on a pair of lead-in wires 18, 20 held in an arbor or stem, 17. The lead-in wires 18,20 are brought out through the arbor to electrical contacts 14,16 on a base 13. Arbor 17 also has a tubulation (no~ shown) through which the interior of the lamp envelope is exhausted and filled, if desired, with a gas. Suitable gases are, for example, argon, a mixture of argon-nitrogen, or a high molecular weight gas, such as ` krypton. The lamp also can be operated as a vacuum type.
When voltage is applied to the lamp, the filament 22 incandesces and produces energy in both the visible and the IR range. The exact spectral distribution of the filament depends upon the resistance of the filament. Typical f ilament operating temperatures are in the range of from about 2650K to about 2900K, although operation at a temperature as low as 2000K and as high as 3050K can be used. As the filament operating temperature increases, the spectral distribution shifts further to the red, 1 i.e. it produces more infrared energyO
The coating 12, in combination with the optical shape of the lamp, serves to reflect back to the filament a substantial, and preferably as large a portion as possiblel i.e. about 85% or more, of the IR energy produced by the filament. When the energy is reflected back to the filament, it increases i~s operating tempera-ture and thereby decreases the power (wattage) required to operate the filament at this temperature.
Fig~ 2 shows how the aberrational effects from the ends of the filament are produced. This shows the lamp cross~section along the longitudinal axis of the envelope. For purposes of explanation, it is considered that the envelope is a closed sphere in this direction. Consider that ~he filament 22 has a length ~ and that the center of this filament C is located at the optical center of the spherical envelope. The filament also is in the general form of a cylinder having a diameter D. Con-sidering the rays which originate from one end O of the filament at a point off the axis as it incandesces, these rays are produced effectively at a variety of angles covering a spherical surface.
Two such rays Rl and R2 are shown which are given off at an angle which is substantially acute with respect to the axis of the filament. Two other rays Sl and S2 are shown which are produced at angle which is somewhat obtuse with respect to the longitudinal axis of the filamentO As shown, the image point for the rays Rl and R2 will be near the image point I2, which is outside of the filament, while the image points for the rays Sl and S2 will be near the image point Il, which is at the end of the filament. It can be shown that for all of the rays originating from the end point O that the image points for many of these rays lie in a region outside of the end of the filament opposite the end O. The infrared energy which is not re-imaged back onto the filament is lost unless recaptured.
1 A similar analysis can be made for the rays which are emitted from the end of the filament opposite 0. An analysis is presented below for calculating these end losses.
The total aberration losses arise from image distortion associated with the sides, or outside surface of the filament, as well as its ends. The losses from the sides occur because the filament geometry does not precisely conform to the shape of the envelope so that the wavefront of rays from the sides of the filament also does not exactly correspond to the envelope and there will be some aberration when they are reflected back to the filament.
It can be shown that the aberrational losses Lc from the sides of an elongated filament centered at the optical center of an optically precise sphere of radius R is as follows:
~ L = _L ~ ~c~
c 31J~ C ~t~ePre ) Where:
Q is the filament length R is the radius of the Eilament cylinder.
c is the surface area of the cylinder assumed for the diameter of the filament.
AE is the end area of the filament.
` Ec is the emissivity of the cylinder.
Ee is the emissivity of the end of the filament.
For a filament 1300mm long in an 80mm G 25 spherical glass enclosure for Ec equals 0.55 and an Ee is approxi-mately 1, the side losses Lc can be calculated to be about 3.1%. That is, this amount of infrared energy will not re-image onto the filament and will be lost.
Fig. 3 shows an ellipsoidal envelope made to reduce the end losses while Fig. 4 is a schematic elevational view to 1 that is, an ellipse is taken and rotated by 360 to produce the ellipsoid. The envelope has a base 13 with stem and tubulation.
The incandescent filament 22, which is preferably coiled-coil or triple coiled, is treated as a cylinder whose axis lies along the major axis of the ellipser The envelope 42 is coated, either on the interior or the exterior with the IR reflective and visible transmissive coating 12.
Referring to Fig. 4, the envelope 42 is designed with respect to the filament so that the location of the foci of the ellipse are positioned to minimize the sum of end and side aberra-tions. In an ellipsoid, rays emitted near one of the foci points located along the length of the filament will be reflected by the coating on the envelope wall back to companion points near the foci points on the opposite side, considering the center C as a dividing line, of the filament from which the ray is emitted.
Usually one internal reflection is required. However, the visible energy passes out through the coating, by an amount determined by the coating transmittance, on the first impingement of the coating.
Rays emitted from near the foci points have no aberraO
tion. However, there is still aberration at the ends of the filament due to distortion.
In an IR reflecting envelope, whether spherical or ellipsoidal, The image of a ray emitted from the end of the filament at an angle ~ with respect to the filament axis, forms at some distance S behind the opposite given by the e~uation
2(1/ )2 cos2 e S(~ (2) The distance from the end oE the filament to the center is~
Thus, at some range of angles of rays emitted by each end of the filament, there will be a loss, that is, the rays will not re-image on the opposite end of the filament after reflection .
2g72 1 from the coating. It can be shown that the rays within the solid angle between 0 and 2 are lost to the filament. That isl the rays from the left end of the filament hetween the two conical angles are not intercepted by the filament.
The end loss LE can be calculated to be LE = (cos ~1 ~ cos ~2) [ EeAe where, the other quantities have been defined above.
For the 13mm long filament in an 80mm diameter G-25 envelope, ~1 and ~2 are about 10.8 and 64.3. The end aberration loss LE is about 6~8% and the side is about 3.1~, as previously discussed, giving a total of 9.9~. This would be the loss in a spherical enclosure where the elongated filament was precisely optically centered.
To determine dimensions of the ellipse to minimize the aberration losses, it is considered that for an ellipse that is not too eccentric, that the end aberration will depend upon the distance from one of the foci in the same manner as the aberration depends upon the distance of the end of the filament from the center of the sphere. This spherical aberration depends on the square of the distance from the center and it is assumed that the elliptical aberration depends on the square of the distance from the nearest of the two foci loca~ed at a distance from the ` ellipse cneter. The elliptical aberration loss L is then taken as the sum of both the end and side losses.
~ ~ ) c L ~ (4) ; where, Lc = the lo~s along the cylinder.
The terms ( ~Q _ X)2 and x2 in the brackets arise from side aberration away from the ellipse center and toward the
Thus, at some range of angles of rays emitted by each end of the filament, there will be a loss, that is, the rays will not re-image on the opposite end of the filament after reflection .
2g72 1 from the coating. It can be shown that the rays within the solid angle between 0 and 2 are lost to the filament. That isl the rays from the left end of the filament hetween the two conical angles are not intercepted by the filament.
The end loss LE can be calculated to be LE = (cos ~1 ~ cos ~2) [ EeAe where, the other quantities have been defined above.
For the 13mm long filament in an 80mm diameter G-25 envelope, ~1 and ~2 are about 10.8 and 64.3. The end aberration loss LE is about 6~8% and the side is about 3.1~, as previously discussed, giving a total of 9.9~. This would be the loss in a spherical enclosure where the elongated filament was precisely optically centered.
To determine dimensions of the ellipse to minimize the aberration losses, it is considered that for an ellipse that is not too eccentric, that the end aberration will depend upon the distance from one of the foci in the same manner as the aberration depends upon the distance of the end of the filament from the center of the sphere. This spherical aberration depends on the square of the distance from the center and it is assumed that the elliptical aberration depends on the square of the distance from the nearest of the two foci loca~ed at a distance from the ` ellipse cneter. The elliptical aberration loss L is then taken as the sum of both the end and side losses.
~ ~ ) c L ~ (4) ; where, Lc = the lo~s along the cylinder.
The terms ( ~Q _ X)2 and x2 in the brackets arise from side aberration away from the ellipse center and toward the
3 ~2~17~
1 ellipse center. When X = 0, the ellipse degenerates into a sphere and:
L = LE + LCl as required.
The minimum aberration is given by setting d~ = o. Solving this equation leads to:
X ~ ) (5) ~/~ E 2Lc If LE = I X is half way to a filament end from the ` center. That is, the foci is located at X by a distance one-fourth of the length of the filament from the end of the filament.
At this location of the foci, the elliptical aberration is one-quarter of the aberration of a filament in a spherical envelope.
If Lc = ~ then X is at the filament end and there is no elliptical aberration. Thus, the spherical aberration is reduced by a factor one-fourth or less within the ellipse.
In a practical example~ X - 0.76 (Q/2) and the foci are located about three-fourths of t:he distance from the center ! to an end. The total aberration loss is then about 2.4% compared to about 9.9~ in a sphere.
As mentioned, the use of the ellipsoid having two foci has further advantages in that the reflected IR radiation will be ~ concentrated about two points, the foci, rather than about a single ; point in a sphereical geometry. This makes the temperature more evenly distributed along the length of the filament. Further, the returned energy will be focussed at two points rather than one and ` there will be less defocusing in between. Since the luminous efficacy of a ~ilament is a function of temperature, decreasing at the cooler positionsf the more even temperature distribution will produce a greater lumen output. Also, unequai temperature gradients lead to shorter filament lives and the more even tempera- ;
ture gradient helps to eliminate this.
1 ellipse center. When X = 0, the ellipse degenerates into a sphere and:
L = LE + LCl as required.
The minimum aberration is given by setting d~ = o. Solving this equation leads to:
X ~ ) (5) ~/~ E 2Lc If LE = I X is half way to a filament end from the ` center. That is, the foci is located at X by a distance one-fourth of the length of the filament from the end of the filament.
At this location of the foci, the elliptical aberration is one-quarter of the aberration of a filament in a spherical envelope.
If Lc = ~ then X is at the filament end and there is no elliptical aberration. Thus, the spherical aberration is reduced by a factor one-fourth or less within the ellipse.
In a practical example~ X - 0.76 (Q/2) and the foci are located about three-fourths of t:he distance from the center ! to an end. The total aberration loss is then about 2.4% compared to about 9.9~ in a sphere.
As mentioned, the use of the ellipsoid having two foci has further advantages in that the reflected IR radiation will be ~ concentrated about two points, the foci, rather than about a single ; point in a sphereical geometry. This makes the temperature more evenly distributed along the length of the filament. Further, the returned energy will be focussed at two points rather than one and ` there will be less defocusing in between. Since the luminous efficacy of a ~ilament is a function of temperature, decreasing at the cooler positionsf the more even temperature distribution will produce a greater lumen output. Also, unequai temperature gradients lead to shorter filament lives and the more even tempera- ;
ture gradient helps to eliminate this.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An incandescent electric lamp comprising:
an ellipsoidal shaped envelope having a base portion, said envelope defining a major axis on which is a pair of spaced focal points, an incandescent filament mounted within said envelope, means for supplying electrical energy to said filament to cause it to incandesce to produce energy in both the infrared and the visible range, means for cooperating with said envelope to return to the filament a substantial portion of the infra-red energy produced by said filament and for transmitting therethrough a substantial portion of the visible range energy produced by said filament;
said filament being elongated, generally cylin-drical and linear along its major axis, at least as long as the distance between the two foci of the major axis of the envelope, and being mounted along the major axis of the ellipsoidal envelope so that the two foci of the ellipsoid are located on the filament at spaced points therealong.
an ellipsoidal shaped envelope having a base portion, said envelope defining a major axis on which is a pair of spaced focal points, an incandescent filament mounted within said envelope, means for supplying electrical energy to said filament to cause it to incandesce to produce energy in both the infrared and the visible range, means for cooperating with said envelope to return to the filament a substantial portion of the infra-red energy produced by said filament and for transmitting therethrough a substantial portion of the visible range energy produced by said filament;
said filament being elongated, generally cylin-drical and linear along its major axis, at least as long as the distance between the two foci of the major axis of the envelope, and being mounted along the major axis of the ellipsoidal envelope so that the two foci of the ellipsoid are located on the filament at spaced points therealong.
2. An incandescent electric lamp as in claim 1 wherein each foci is located at a distance from between a respective end of the filament to about one half of the distance to the center of the filament.
3. An incandescent electric lamp as set forth in claim 1 when the filament is longer than the distance between the foci.
4. An incandescent electric lamp as in claim 2 wherein each foci is located at a respective end of the filament to minimize side losses.
5. An incandescent electric lamp as in claim 2 wherein each foci is located at about one half of the distance from a respective end of the filament to the center of the filament.
6. An incandescent electric lamp as in claim 2 wherein each foci is located at about three fourths of the distance from the center of the filament to a respec-tive end.
7. An incandescent electric lamp as in either of claims 1 or 2 wherein said cooperating means comprises a coating on the envelope wall.
8. An incandescent electric lamp as in claim 1 wherein each foci is located at a distance from a respec-tive end of the filament to its center such as to produce a more uniform temperature distribution along the filament.
9. An incandescent electric lamp as in claim 1 hwerein the two foci are each located at respective points along the length of the filament to reduce side or end aberration losses.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7635879A | 1979-09-17 | 1979-09-17 | |
| US76,358 | 1979-09-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162972A true CA1162972A (en) | 1984-02-28 |
Family
ID=22131507
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000360404A Expired CA1162972A (en) | 1979-09-17 | 1980-09-17 | Ellipsoidal envelope for incandescent infra-red energy reflecting lamp |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5682565A (en) |
| CA (1) | CA1162972A (en) |
| DE (1) | DE3035068A1 (en) |
| FR (1) | FR2465313B1 (en) |
| GB (1) | GB2059154B (en) |
| MX (1) | MX148084A (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4535269A (en) * | 1983-08-01 | 1985-08-13 | General Electric Company | Incandescent lamp |
| JPS6077347A (en) * | 1983-10-05 | 1985-05-01 | 東芝ライテック株式会社 | Halogen bulb |
| JPH0512920Y2 (en) * | 1986-02-04 | 1993-04-05 | ||
| DE19701794A1 (en) * | 1997-01-20 | 1998-07-23 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Incandescent lamp with reflective coating |
| DE19701792A1 (en) * | 1997-01-20 | 1998-07-23 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Incandescent lamp with reflective coating |
| CN1049761C (en) * | 1997-09-26 | 2000-02-23 | 叶乃光 | Incandescent lamp, halogen-tungsten lamp and electric arc lamp with infrared reflecting film |
| DE19843852A1 (en) * | 1998-09-24 | 2000-03-30 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Electrical incandescent lamp has light body(ies) in lamp vessel with flat, esp. strip-shaped, light body element(s) radiating in infrared and visible regions, infrared reflective filter(s) |
| DE19844519C2 (en) * | 1998-09-28 | 2000-08-03 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Electric light bulb with IR reflection layer |
| DE102004043176B4 (en) * | 2004-09-03 | 2014-09-25 | Osram Gmbh | infrared Illuminator |
| US7518299B2 (en) * | 2006-09-27 | 2009-04-14 | Osram Sylvania Inc. | Compact PAR lamp comprising an ellipsoid reflector having more than one focal point |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4160929A (en) * | 1977-03-25 | 1979-07-10 | Duro-Test Corporation | Incandescent light source with transparent heat mirror |
| JPS5498072A (en) * | 1978-01-18 | 1979-08-02 | Toshiba Corp | Incandescent lamp |
| NL184651C (en) * | 1979-02-26 | 1989-09-18 | Philips Nv | ELECTRIC LIGHT BULB. |
-
1980
- 1980-09-10 FR FR8019496A patent/FR2465313B1/en not_active Expired
- 1980-09-12 JP JP12784180A patent/JPS5682565A/en active Pending
- 1980-09-17 GB GB8030066A patent/GB2059154B/en not_active Expired
- 1980-09-17 DE DE19803035068 patent/DE3035068A1/en not_active Ceased
- 1980-09-17 MX MX18396480A patent/MX148084A/en unknown
- 1980-09-17 CA CA000360404A patent/CA1162972A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2059154B (en) | 1983-04-07 |
| MX148084A (en) | 1983-03-10 |
| FR2465313A1 (en) | 1981-03-20 |
| FR2465313B1 (en) | 1986-04-11 |
| DE3035068A1 (en) | 1981-04-02 |
| GB2059154A (en) | 1981-04-15 |
| JPS5682565A (en) | 1981-07-06 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |