*
`vee
`4,240,010
`[11]
`United States Patent t
`Buhrer
`[45]
`Dec. 16, 1980
`
`
`altham,
`
`Mass.
`
`[54] ELECTRODELESS FLUORESCENT LIGHT
`SOURCE HAVING REDUCED FAR FIELD
`ELECTROMAGNETIC RADIATION LEVELS
`(75]
`Inventor: Carl F, Buhrer, Framingham, Mass.
`.
`.
`[73] Assignee: Beneraones Incorporated,
`[21] Appl. No.: 49,773
`[22] Filed:
`Jun, 18, 1979
`[52]
`Int. Ch3 vccesneeseee HO5B 41/16; HOSB 41/24
`[52] ULS. C1, neeecsessetessresesssarseeneneee 315/248; 315/57;
`.
`315/70; 315/85; 336/226; 336/232
`[58] Field of Search.........beseoreane 315/248, 344, 39, 57,
`315/85, 70; 336/226, 232
`[56]
`References Cited
`U.S. PATENT DOCUMENTS
`6/1931
` MOrrisOm .......scscseeersenes 315/248 X
`7/1931 Morrison...
`.. 315/248 X
`
`
`~. 336/226 X
`5/1949
`Reinartz....
`
`Blackman......
`- 315/248 X
`5/1960
`
`3/1976 Haugsjaa et al. ween 315/248
`
`....scssssmsesen 315/248
`3/1976 Hauggjaa et al.
`
`... 315/248:
`3/1976 McNeill etal. ...
`
`wo 315/248
`10/1976
`Anderson......
`ANdersOon ....ssccssecercersseeeteees 315/248
`10/1976
`
`1,807,927.
`1,813,580
`2,471,777
`2,939,049
`3,942,058
`3,942,068
`3,943,404
`3,987,334
`3,987,335
`
`4,017,764
`4/1977 Anderson coscnesesensenceeessenssesees 315/248
`ewe "yiovg
`caner tk a ssseesneneseeeannseneey seyve
`
`117,
`Jr. ceeeccsceeeeeeees
`ASCOCK,
`
`10/1978 Hollister ween 315/248
`4,119,889
`
`KWOM wissesesesseesteseeeeesnens 315/344
`4,171,503
`10/1979
`
`2/1980 Houston oo.
`cccsesseceseneeees 315/248
`4,187,445
`Stout et al. cascssssusesssssneeeee 315/85
`4,187,447
`2/1980
`Primary Examiner—Saxfield Chatmon,Jr.
`Attorney, Agent, or Firm—William R. McClellan
`[57]
`ABSTRACT
`An electrodeless fluorescent light source includes an
`electrodeless fluorescent lamp and an induction coil
`wherein the magnitudeofthe far field electromagnetic
`radiation, produced directly by the induction coil,
`is
`minimized. The induction coil includes current loops
`which are configured
`that themagneticdipole mo-
`dipolemomentofother‘currentloops in ordertomini.
`mize the net magnetic dipole momentof the induction
`coil. One embodiment of the induction coil includes a
`conductor wound in the shape of a square prism. The
`current on adjacentside edgesofthe prism is in opposite
`directions,
`thus resulting
`in two pairs of mutually op-
`;
`»
`Haus
`resulng
`P
`Posing magnetic dipole moments.
`
`14 Claims, 6 Drawing Figures
`
`76
`
`
`
`
`
`
`78
`
`HIGH FREQUENCY
`POWER SOURCE
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 001
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 001
`
`

`

`U.S. Patent
`
`Dec. 16, 1980
`
`Sheet 1 of 2
`
`4,240,010
`
`ig
`
`FIG. |
`PRIOR ART
`
`
`
`CODLDLLEPLLLREoi
`DEPELLETLLLLELEEES
` 24
`
`
`
` Le
`
`LS
`
`
`
`
`HIGH FREQUENCY
`POWER SOURCE
`
`20
`
`28
`
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`
` 30
`
`
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 002
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 002
`
`

`

`U.S. Patent
`
`Dec. 16, 1980
`
`Sheet 2 of 2
`
`4,240,010
`
`76
`
`\
`
`
`
`
`
`
` 86 [NW
`=TAVV&\\—++SLA nN_
`
`YZ]S
`
`
`
`2Y
`
`
`
`
`
`84
`
`
`
`HIGH FREQUENCY
`POWER SOURCE
`
`
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 003
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 003
`
`

`

`1
`
`4,240,010
`
`ELECTRODELESS FLUORESCENT LIGHT
`SOURCE HAVING REDUCED FAR FIELD
`ELECTROMAGNETIC RADIATION LEVELS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`C. F. Buhrer, “Planar Electrodeless Fluorescent
`Light Source”, assignee’s docket no. 21,593,filed con-
`currently with the present application and assigned to
`the same assignee as the present application, discloses
`electrodeless fluorescent light sources having a planar
`structure and having for excitation an induction coil
`which produces minimalfar field electromagnetic radi-
`ation levels.
`BACKGROUND OF THE INVENTION
`
`15
`
`This invention relates to electrodeless fluorescent
`light sources excited byhigh frequency power. More
`particularly, this invention relates to electrodeless fluo-
`rescent light sources having reduced far field radiation
`levels.
`Conventional high brightness fluorescent lamps pro-
`vide long life and efficient operation but requirelarge,
`heavy and expensiveballasting circuits for operation at
`line frequencies. The low pressure glow discharge in
`mercury vapor that provides the phosphorexcitation in
`fluorescent lampsis usually powered by a currentat the
`power line frequency between two internal emissive
`electrodes. Current control is required because of the
`negative impedance characteristic of the discharge, and
`this is obtained by means ofthe series inductive impe-
`dance of an iron core ballast. In addition, as one at-
`tempts to make small fluorescent lamps, power losses
`connected with the electrodes become an increasingly
`large fraction of the applied power. Electrodeless exci-
`tation of the glow discharge by radio frequency fields
`has the potential advantageof providing a light weight
`system by eliminating the usual ballast. Also, without
`the usual filaments, lamp life would be increased.
`Several
`approaches
`to electrodeless
`fluorescent
`lamps have been taken in the past. In one approach,
`frequencies in the range of 10 to 500 KHz were used
`with ferrite structures designed to link the high fre-
`quency magnetic field through a closed loop of plasma
`discharge. In U.S. Pat. No. 3,500,118 issued Mar. 10,
`1970 to Anderson and U.S. Pat. No. 3,521,120 issued
`July 21, 1970 to Anderson, there are disclosed elec-
`trodeless fluorescent light sources which utilize a mag-
`netically induced radio frequencyelectric field to ionize
`a gaseousradiating medium.Ferrite coresare utilized to
`couple energy to the discharge. A great variety of ge-
`ometriesis possible. For example, the use of closed loop
`ferrite core circuits to minimize stray fields that can
`radiate was disclosed in U.S. Pat. No. 4,005,330 issued
`Jan, 25, 1977 to Glascock,Jr. et al.
`In a second approach,the frequencies are in the 3 to
`300 MHzrange, and noferrites are needed. In U.S. Pat.
`No. 4,010,400 issued Mar. 1, 1977 to Hollister, radio
`frequency power is coupled to a discharge medium
`contained ina phosphor coated envelope by an induc-
`tion coil with a nonmagnetic core ‘connected to a radio
`frequency source. Radiation by the magnetic’ dipole
`field of the excitation coil is a problem.
`A third approach to electrodeless fluorescent light
`sources, utilizing even higher frequencies in the 100
`MHzto 300 GHzrange, was disclosed by Haugsjaa et
`al.
`in pending U.S. application Ser. No. 959,823 filed
`
`30
`
`35
`
`40
`
`45
`
`60
`
`65
`
`2
`Nov. 13, 1978 and assigned to the assignee of the present
`invention. High frequency power,
`typically at 915
`MHz,is coupled to an ultravioletproducing low pres-
`sure discharge in a phosphor-coated electrodeless lamp
`which acts as a termination load within a termination
`fixture. Electromagnetic radiationis less of a problem at
`the higher frequencies of operation because shielding
`can be accomplished with a fine conductive mesh
`which blocks only a small percentage of the light out-
`put. At lower frequencies of operation, such as those
`disclosed in the Hollister patent, a heavier conductive
`mesh is required to accomplish effective shielding be-
`cause of the reduced skin effect at lower frequencies.
`The heavier mesh is impractical because more of the
`light output is blocked.
`Regardless of the frequency range utilized for excit-
`ing the glow dischargeofa fluorescent lampthe control
`of electromagnetic radiation at the operating frequency
`and its harmonics is of high priority. In the low fre-
`quency range, a lamp system utilizing a free running
`class C oscillator coupled througha coil orferrite struc-
`ture to a discharge radiates harmonics randomly dis-
`persed through the 500-1600 KHz broadcast band and
`gives severe radio interference. In the higher frequency
`range, the effect is similar, but the interference is to
`otherclasses of radio and television services. In general,
`therefore, the operating frequency should be fixed and
`chosen for electromagnetic compatibility, the power
`source should be well shielded with its output filtered to
`remove harmonics, and the coupling system and glow
`discharge geometry should be chosen to minimize radi-
`ation. The power source aspect of this problem was
`recognized in U.S. Pat. No. 4,048,541 issued Sept. 13,
`1977 to Adams et al wherein a power source for an
`electrodeless fluorescent lamp was designed to elimi-
`nate second harmonics.
`
`SUMMARYOF THE INVENTION
`
`It is an object of the present invention to provide
`improved
`electrodeless
`fluorescent
`light
`sources
`wherein high frequency poweris inductively coupled
`to the discharge and wherein the far field elegtromag-
`netic radiation produced directly by the induction coil
`is minimized.
`According to the present invention, this and other
`objects and advantages are achieved in an electromag-
`netic discharge apparatus including an electrodeless
`lamp and means for excitation of the discharge in the
`electrodeless lamp by high frequency power. Theelec-
`trodeless lamp has an envelope madeofa light transmit-
`ting substance. The lamp envelope has onits inner sur-
`face.a phosphor coating which emits visible light upon
`absorption of ultraviolet radiation and encloses a fill
`material which emits ultraviolet radiation during elec-
`tromagnetic discharge. The excitation means includes
`induction coil means located in sufficiently close prox-
`imity to the electrodeless lamp to cause discharge. The
`induction coil means includes a plurality of current
`loops, each having an individual magnetic dipole mo-
`ment, which emits electromagnetic radiation, and has a
`net magnetic dipole moment whichis the vector sum of
`said individual magnetic dipole moments. The current
`loops are configured so that each individual magnetic
`dipole momentis offset by other individual magnetic
`dipole momentsin order to minimize said net magnetic
`dipole moment. In this way, the magnitude of the far
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 004
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 004
`
`

`

`3
`field electromagnetic radiation, produced directly by
`said induction coil means, is. minimized.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4,240,010
`
`In the Drawings:
`FIG.1 is a simplified sectional view of an electrode-
`less fluorescent light source according to thepriorart.
`FIG. 2 is a perspective view of an induction coil
`according to one embodimentof the present invention.
`FIG.3 is a top view of the induction coils shown in
`FIG.2 illustrating pictorially the magnetic fields and
`magnetic dipole moments.
`FIG. 4 is a perspective view of an induction coil
`according to another embodimentof the present inven-
`tion.
`,
`FIG. 5 is a perspective view of a light source in ac-
`cordance with the present invention.
`FIG.6 is a side view of an induction coil according to
`another embodimentof the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`The induction coil 20 results in a much lowerlevel of
`far field radiation than the helical coil used in the prior
`art. Considering individually each side face of the
`prism,currentcirculates around that face and produces
`a dipole radiation pattern. FIG.3 is a top view of induc-
`tion coil 20 andillustrates the magnetic dipole moment
`40 produced by the current loop on each face of the
`For a better understanding of the present invention,
`prism. Also shownin FIG. 3 are the magneticfiled lines
`together with other and further objects, advantages and
`42 generated by induction coil 20. The fields produced
`capabilities thereof, reference is made to the following
`by adjacent conductors are of opposite polarity. These
`disclosure and appended claims in connection with the
`are the fields which interact with the electrodeless lamp
`above-described drawings.
`fill material as will be discussed hereinafter. The dipole
`light
`A typical prior art electrodeless fluorescent
`moments from opposite sides of the prism also are of
`source is shown in FIG.1. It includes an electrodeless
`opposite polarity. Thus, when viewed from thefarfield,
`lamp 10 with a phosphor.coating 12, an induction coil 30 or distances much greater than the dimensionsof induc-
`14, and a high frequency power source 16. The elec-
`tion coil 20, the dipole contribution from each face of
`trodeless lamp 10 has an envelope madeofa light trans-
`the prism is offset by the contribution from the opposite
`mitting substance such as glass and enclosesa fill mate-
`face to give a net dipole momentof approximately zero.
`rial such as mixtures of mercury and an inert gas which
`The resulting dipole radiation field in a practical induc-
`emit ultraviolet light during discharge. High frequency 35 tion coil 20 is not exactly zero because of imperfections
`poweris coupled to the discharge by induction coil 14.
`in the coil construction and because of second order
`The phosphor coating 12 on the inner surface of lamp
`effects. One requirement for the above discussion to
`10 emitsvisible light upon absorptionofultravioletlight
`hold true is that the length of the conductor used to
`from the discharge. Such a light source is shownin U.S.
`form induction coil 20 be small in comparison with the
`Pat. No. 4,010,400. The induction coil 14 is wound ina
`wavelength at the frequency of operation. This is neces-
`helical configuration and radiates
`an appreciable
`sary to insure that there is no phase retardation between
`amount of energy at the frequency of operation.
`radiation from dipole moments on opposite faces of the
`According to the present invention, unique configu-
`prism. It is also required that the separation between
`rations of the induction coil are utilized to reduce the
`opposite faces of the prism be small in comparison with
`radiated high frequency energy. Referring now to FIG.
`the wavelength of the excitation signal. Therefore,
`2, there is shownan inductioncoil 20 having the general
`when an electrodeless fluorescent light source is oper-
`shape of a square prism. As used in this disclosure, the
`ated at 40.68 MHz, which has a wavelength of about 7.4
`term “inductioncoil”is intended to include any config-
`meters, the maximum dimensions of induction coil 20
`uration of an elongated conductor which has the pur-
`should be a few centimeters to avoid problemsof phase
`retardation.
`pose of coupling magnetic fields to an electrodeless
`lampandis not limited to a series ofspirals or rings. The
`Theinduction coil 20 shownin FIG.2 is one example
`induction coil 20 is formed from insulated wire and can
`of induction coil geometries which meet the require-
`be supported by an insulating form of dielectric mate-
`ments of the present invention. The essential require-
`rial. Alternatively, the induction coil 20 can be formed
`ment is that each dipole momentbe offset by one or
`from wire which hassufficient stiffness to be self-sup-
`more dipole moments of opposite polarity to minimize
`porting. Regardless of how the induction coil 20 is
`the net magnetic dipole moment so that the far field
`supported,it can be visualized as outlining an imaginary |
`electromagnetic radiation level produced directly by
`square prism which has four rectangular side faces and
`the induction coil is minimized. The net magnetic dipole
`twosquare end faces. The prism thushasfour side edges
`momentsofthe induction coil is the vector sum ofthe
`formed by the intersections of the four side faces. As
`individual magnetic dipole moments produced by each
`shownin FIG,2, the conductor forming induction coil
`current loop of the induction coil. Thus,
`the prism-
`20 starts at input 22 and runs up edge24, across the top
`shaped induction coil can have a rectangular base as
`of the prism and down edge 26. The conductor then
`well as a square base. Also, the side faces of the prism
`runs across the bottom of the prism, up edge 28, across
`can be parallelograms as well as rectangles. The dipole
`the top of the prism, and down edge 26. From here, the
`moments produced by opposite faces of such induction
`conductorruns across the bottom of the prism, up edge
`coils offset each other. In general, the base of the prism-
`24, across the top of the prism, and down edge 30. Fi-
`shaped induction coil can be regular polygonal where
`nally,
`the conductor runs across the bottom of. the
`the polygon has an even numberofsides, for example,
`
`4
`prism, up edge 28, across the top of the prism, down
`‘edge 30, and across the bottom ofthe prism to input22.
`This confiiguration results in two conductors along each
`side edge of the square prism. While other winding
`sequencescanbeused, the important requirementis that
`current at any instant of time must flow in opposite
`directions on adjacent side edges and in the samedirec-
`tion on diagonally opposite side edges of the prism. The
`direction of current flow at one instant of time on side
`edges 24, 26, 28 and 30 is shownin FIG.2 by the arrows
`parallel to the conductors. The current in edges 24 and
`28 is up whereas the current in edges 26 and 30 is down.
`The indicated directions of current flow, of course,
`reverse with time becauseofthe alternating input cur-
`rent.
`
`—_ 0
`
`20
`
`25
`
`40
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`45
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`50
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`60
`
`65
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 005
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 005
`
`

`

`4,240,010
`
`5
`regular hexagonal or regular octagonal. An induction
`coil in the shape-of a regular polygonal prism according
`to the present invention has an even numberof side
`faces and an even numberof side edges formed by the
`intersections of the side faces. The conductor forming
`the induction coil is configured to run parallel to and
`coincide with the side edges in such a direction that,at
`any instant of time, current in the conductor on adjacent
`side edges of the coil flows toward opposite endsof the
`coil. The dipole moment produced by the conductor on
`each face of the regular polygonalprism is offset by the
`dipole moment of one or more other conductors. In the
`case of a rectangular induction coil, the dipole moment
`producedby eachfaceis offset by the dipole moment of
`the opposite face. However, in the case of a regular
`hexagonal
`induction coil,
`the dipole moments. offset
`each other in groups ofthree.
`The maximum numberof sides on the prism-shaped
`induction coil has two limitations. Thefirst, discussed
`above,
`is that the conductor length must be short in
`relation to the wavelength of operation. This is harder
`to meet as the number of sides on the prism increases,
`and requires smaller dimensions, and a lower operating
`frequency. The second limitation, to be discussed later,
`relates to problemsof effective excitation of the elec-
`trodeless lamp. Another variation to any of the induc-
`tion coils discussed above is to repeat.the winding ‘pat-
`tern one or more times, thereby increasing the induc-
`tarice of the coil. Based on the above considerations,
`preferred dimensionsof square prismatic induction coils
`are in the range of 1 cm to 5 cm square by 2 cm to 10cm
`in length.
`A simplified version of induction coil 20 is shown in
`FIG.4 as induction coil 50. It is similar to induction coil
`20 in that it generally out lines the form.of a square
`prism, but the conductor passes only once along each
`side edge of the prism. The conductorstarts at input 52,
`runs along edge 54, across the top of the prism and
`down edge 56. The conductor then runs across the
`bottom of the prism, up side edge 58, across the top of
`the prism, and down side edge 60 to input 52. This
`configuration meets the requirement, stated above, that
`the current on adjacent side edges of the prism be in
`opposite directions at any instant oftime.
`While the conductor on each face of the prism does
`not form a complete loop, the current flow in the side
`edges of each face results in a dipole moment whichis
`offset by the dipole moment of the opposite face. Thus,
`this configuration also has a net dipole moment of
`nearly zero and the far field electromagnetic radiation
`level is minimal.
`An electromagnetic discharge apparatus according to
`the present invention is shown in FIG.5 as an electrode-
`less fluorescent light source. The light source includes
`an electrodeless lamp 70 and a meansfor excitation of
`discharge in electrodeless lamp 70 by high frequency
`power. The excitation means includes an induction coil
`72 which can be either of those shown in FIG. 2 or
`FIG. 4 and described above or any other configuration
`whichis configured to minimize the net magnetic dipole:
`moment of the induction coil so that the magnitude for
`the far field electromagnetic radiation, produced .di-
`rectly by the induction coil is minimized. Electromag-
`netic radiation emitted by the discharge inside elec-
`trodeless lamp 70 and by the phosphor coating is not
`suppressed by the present invention. The electromag-
`netic radiation produced directly by the induction coil
`is in the frequency range from 1 to 100 MHz and har-
`
`6
`monics thereof, as discussed hereinafter. Induction coil
`72 must be in sufficiently close proximity to electrode-
`less lamp 70 to cause discharge. That is, a substantial
`percentage of the magnetic field produced by induction
`coil 72 must be within electrodeless lamp 70.
`Electrodeless lamp 70 has an envelope madeofa light
`transmitting substance, such as glass, and enclosesa fill
`material which emits ultraviolet light upon excitation
`by high frequency power. The inner surface 74 of the
`envelope has a phosphor coating which emits visible
`light upon absorption of ultraviolet light. The phosphor
`coating can be any of the conventional phosphors used
`in commerical fluorescent lamps of the electroded type.
`The electrodeless lamp 70 shown has the shape of a
`cylinder with a cavity 76 extending throughits center
`for insertion of induction coil 72. The lamp 70 can have
`other shapes provided the induction coil 72 is suffi-
`ciently close. to couple power to the discharge in the
`electrodeless lamp. For example, the lamp can be simi-
`lar in shape to that shown in FIG.5, but can have a
`cavity extending only partially through the center of
`the lamp. Also, the lamp can be similar in shape to a
`standard incandescent lamp,that is, pear-shaped, witha
`cavity for induction coil 72. In another configuration, a
`tubular-electrodeless lampis placed inside the induction
`coil. The fill material for electrodeless lamp 70 is typi-
`cally an inert gas, such as argon, under low pressure and
`mercury which mixture emits ultraviolet radiation upon
`excitation by high frequency power.
`The light source shown in FIG.5 can include a high
`frequency power source 78 which has its output cou-
`pled to induction coil 72. The power source 78 is in the
`frequency range from 1 MHz to 100 MHz. Twopre-
`ferred frequencies of operation are 13.56 MHz and 40.68
`MHzwhich are both in ISM (Instrument, Scientific and
`Medical) bands set aside for devices such as the light
`source herein disclosed. The power source 78 should
`have a stable output frequency and preferably be crystal
`controlled to avoid interference with radio services.
`Anysuitable high frequency power source can be used,
`such as the power source shown in U.S. Pat. No.
`4,048,541 issued Sept. 13, 1977 to Adamset al. The high
`frequency power source 78 can be mechanically pack-
`aged with electrodeless lamp 70 and induction coil 72 to
`produce a complete fluorescent light source having a 60
`Hzline frequency input. The light source according to
`the present invention can also includea filter 80 having
`its input coupled to the output of power source 78 and
`its output coupled to induction coil 72. The purpose of
`filter 80 is to remove harmonics and other spurious
`outputs of high frequency power source 78, thereby
`reducing electromagnetic radiation at frequencies other
`than that chosen for operation ofthe light source. Filter
`80 is typically a low-pass filter having a cutoff fre-
`quency just above the operating frequency. A capacitor
`82 can be connected across induction coil 72 to tuneit
`to resonanceat the frequency of operation.
`In operation, the oscillating magnetic field generated
`by induction coil 72 penetrates the inner wall of elec-
`trodeless lamp 70 and induces a circulating plasma cur-
`rent just outside the four side faces of induction coil 72.
`Twoloopsof plasma current 84 and 86areillustrated in
`FIG. 5. Adjacent plasma current loops, such as 84 and
`86, are of opposite phase. These regions of plasma emit
`ultraviolet radiation which excites the phosphorcoating
`to producevisible light.
`Thelimitations, discussed above, on the geomeiry of
`induction coil 72 are related to excitation of the lamp as
`
`15
`
`25
`
`30
`
`35
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`40
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`45
`
`350
`
`55
`
`60
`
`65
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 006
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 006
`
`

`

`4,240,010
`
`7
`8
`well as to the far field level of electromagnetic radia-
`means for excitation of the discharge in said elec-
`tion.. The plasma currents discussed above exist in the
`trodeless lamp by high frequency power, said exci-
`near field regions adjacent to each conductive segment
`tation means including induction coil’ means lo-
`of induction coil 72. As one moves further from a par-
`cated in sufficiently close proximity to said lamp to
`cause discharge, said induction coil means includ-
`ticular segment, the contribution to the field strength 5
`ing a conductor configured to generally outline the
`from other segments begins to take effect and reduce
`shape of a regular polygonal prism having an even
`the net field. Thus, the plasma current is reduced. As
`number of side faces and an even numberofside
`the conductive segments are moved closer together, ’as
`edges formed bythe intersectionsofsaid side faces,
`is the case in the higher order polygonal coil geometry
`said conductor being configured to run parallel to
`discussed above,
`the plasma current region is con- 10
`and coincide with said side edges in such a direc-
`stricted closer to the induction coil 72. Since it‘is desir-
`tion that, at any instantof time, current in the con-
`able to have the plasma current fill the entire lamp
`ductor on adjacent side edges ofsaid prism flows
`volume for effective light production, this plasma cur-
`toward opposite ends of said prism, said induction
`rent constriction is to be avoided.
`coil means thereby includinga plurality of current
`An electrodeless fluorescentlight source constructed 15
`loops, each having an individual magnetic dipole
`in accordance with the present invention utilized an
`moment which emits electromagnetic radiation,
`electrodeless lamp of the shape shown in FIG. 5. The
`and having a net magnetic dipole moment whichis
`lamp had an outside diameter of4.7 cm,an inside diame-
`the vector sum ofsaid individual magnetic dipole
`ter of 2.5 cm and a length of 13 cm. Thefill material
`moments, said current loops being configured so
`included 3 milligrams of mercury and 6 torrof neon’ 20
`that each individual magnetic dipole momentis
`which included 0.1% argon. The phosphor coating was
`offset by other individual magnetic dipole moments
`a blend of two high temperature phosphors which can
`in order to minimize said net magnetic dipole mo-
`maintain efficiency to at least 250° C. The phosphor
`ment, whereby the magnitude of the farfield elec-
`consisted of 60 weight percent of (Y, Eu)2 O3 and 40
`tromagnetic radiation, produced directly by said
`weight percent of (Ce, Tb)MgAIloxide. The induction 25
`induction coil means, is minimized.
`coil was of the type shown in FIG. 4 and was suffi-
`2. The electromagnetic discharge apparatus as de-
`ciently large to fill the inner cavity of the electrodeless
`fined in claim 1 wherein said excitation means further
`lamp. When operated at an input frequency of 40.68
`includes a high frequency power source having its out-
`MHz, the light source produced approximately 8000
`lumens with 200 watts of input high frequency power. 30 put coupled to said induction coil means.
`Analternative embodiment of an induction coil 90
`3. The electromagnetic discharge apparatus as de-
`according to the present invention is shown in FIG.6.
`fined in claim 1 wherein said regular polygonal prism is
`Coil 90 is of the general type having helical or spiral
`a square prism.
`windings. However, the coil winding reverses direction
`4. The electromagnetic discharge apparatus as de-
`at the midpoint 92 of induction coil 90 so that the lower 35 fined in claim 3 wherein said excitation means further
`half94 is woundin onedirection while the upper half 96
`includes a high frequency powersourcehavingits out-
`is wound in the opposite direction. Such a winding
`put coupled to said induction coil means.
`configuration produces the dipole moments 98 shownin
`5. The electromagnetic discharge apparatus as de-
`FIG.6. Since the lower half 94 and the upperhalf 96 of_fined in claim 4 wherein said excitation means further
`induction coil 90 are wound in opposite directions, the 40 includes, coupled to the output of said high frequency
`magnetic dipole moments are of opposite polarity and
`powersource, means for reducing harmonic frequency
`offset each other in the far field. Thus, the level of|components of the output power produced bysaid
`electromagnetic radiation produced by induction coil
`source.
`:
`90 in the far field is nearly zero as discussed above.
`6. The electromagnetic discharge apparatus as de-
`Induction coil 90 can be usedin the light source shown 45 fined in claim 5 wherein said excitation means further
`in FIG. 5 or in similar configurations. Induction coil 90
`includes, coupled to said induction coil means, means
`generates two plasma current loops in an electrodeless
`for tuning said induction coil means to resonance.
`lamp. Both loops are concentric with induction coil 90
`7. The electromagnetic discharge apparatus as de-
`but flow in opposite directions. One plasma loop is
`fined in claim 6 wherein said high frequency power
`adjacentto the upperhalf 96 of induction coil 90 and the 50 source is in the range from 1 MHz to 100 MHz.
`secondplasma loop is adjacent to the lower half 94of
`8. The electromagnetic discharge apparatus as de-
`induction coil 90.
`fined in claim 3 wherein said electrodeless lamp has a
`While there has been shown and described whatis at
`cavity therein and said induction coil is located in said
`present considered the preferred embodiments of the
`cavity.
`invention, it will be obvious to thoseskilled in the art 55.
`9, An electromagnetic discharge apparatus compris-
`that various changes and modifications may be made
`ing:
`therein without departing from the scope ofthe inven-
`an electrodeless lamp having an envelope madeof a
`tion as defined by the appended claims.
`light transmitting substance, said envelope having
`Whatis claimedis:
`on its inner surface a phosphorcoating which emits
`1. An electromagnetic discharge apparatus compris- 60
`visible light upon absorption of ultraviolet radia-
`ing:
`tion, said envelope enclosing a fill material which
`an electrodeless lamp having an envelope made of a
`emits ultraviolet radiation during electromagnetic
`light transmitting substance, said envelope having
`discharge; and
`on its inner surface a phosphor coating which emits
`means for excitation of the discharge in said elec-
`visible light upon absorption of ultraviolet radia- 65
`trodeless lamp by high frequency power,said exci-
`tion, said envelope enclosing a fill material which
`tation means including induction coil means lo-
`emits ultraviolet radiation during electromagnetic
`cated in sufficiently close proximity to said lamp to
`discharge; and
`cause discharge, said induction coil means includ-
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 007
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 007
`
`

`

`4,240,010
`
`_ 0
`
`9
`10
`onits inner surface a phosphorcoating which emits
`ing a conductor configured to generally outline the
`visible light upon absorption of ultraviolet radia-
`shape of a rectangular prism having fourside faces
`and four side edges formed by the intersections of
`tion, said envelope enclosingafill material which
`said side faces, said conductor being configured to
`emits ultraviolet radiation during electromagnetic
`run parallel to and coincide with said side edges in
`discharge; and
`means for excitation of the discharge in said elec-
`such a direction that, at any instant of time, current
`trodeless lamp by high frequency power, said exci-
`in the conductor on adjacent side edges of said
`prism flows toward opposite ends of said prism and
`tation means including induction coil means lo-
`cated in sufficiently close proximity to said lamp to
`current in the conductor on diagonally opposite
`side edges ofsaid prism flows toward the same end
`cause discharge, said induction coil means includ-
`ing a conductor configured in a generally helical
`of said prism, said induction coil means thereby
`form, said conductor being wound one-half in a
`including a plurality of current loops, each having
`clockwise direction and one-half in a counterclock-
`an individual magnetic dipole moment which emits
`electromagnetic radiation, and having a net mag-
`wise direction, said induction coil means thereby
`including a plurality of current loops, each having
`netic dipole moment which is the vector sum of
`an individual magnetic dipole moment which emits
`said individual ma