.i
`*'
`e
`Umted States Patent
`
`[19]
`
`[11]
`
`4,240,010
`
`
`Buhrer
`[45]
`Dec. 116, 1980
`
`4,017,764
`29:35:33
`,
`,
`4,119,889
`4,171,503
`4,187,445
`
`4,137,447
`
`4/1977 Anderson ............................. 315/248
`
`Elmer Ci a}- --------- gig/gig
`1(9);3;;
`r.
`..
`.....
`ascoc <,
`
`10/1978 Hollister ................... 315/248
`
`10/1979 Kwon ........... 315/344
`
`2/1980 H sto ........... 315/248
`
`2/1980
`
`51(13):: ellal. ............................. 315/35
`
`Primary Examiner—Saxfield Chatmon, Jr.
`Attorney, Agent, or Firm—William R. McClellan
`
`[54] ELECTRODELESS FLUORESCENT LIGHT
`SOURCE HAVING REDUCED FAR FIELD
`ELECTROMAGNETIC RADIATION LEVELS
`Inventor: Carl F. Buhrer, Framingham, Mass.
`
`[75]
`
`[73] ASSigne€=
`
`gilelg:ab°fit°fi°S “comma“,
`
`at am,
`
`ass.
`
`[21] Appl- N0-= 49.773
`
`[22] Filed:
`
`Jun. 18, 1979
`
`Int. Cl.3 ...................... H0513 41/16; H0513 41/24
`[51]
`[52] US. Cl. ...................................... 315/248; 315/57;
`_
`315/70; 315/85; 336/226; 336/232
`[58] Fleld of Search ......... z ......... 315/248, 344, 39, 57,
`“5/85, 70; 336/226’ 232
`References Cited
`
`[56]
`
`1,807,927
`1,813,580
`2,471,777
`’
`’
`2 939049
`3’942’058
`3,942,068
`3,943,404
`3,987,334
`3,987,335
`
`U'S' PATENT DOCUMENTS
`6/1931 Morrison ......................... 315/248 X
`
`-- 315/248 X
`7/ 1931 Morrison
`
`5/1949 Reinartz
`335/226 X
`
`"
`"""
`.
`5/1960
`Blackman
`315/248 x
`
`
`'
`"""" “5/248
`3/1976 HaugSJaa et al.
`
`3/1976 Haugsjaa et a]. ............ 315/248
`3/1976 McNeil] et a1.
`315/248
`
`..._315/248
`10/ 1976 Anderson ......
`10/ 1976 Anderson ............................. 315/248
`
`75
`
`
`
`[57]
`
`ABSTRACT
`
`An electrodeless fluorescent light source includes an
`electrodeless fluorescent lamp and an induction coil
`wherein the magnitude of the far field electromagnetic
`radiation, produced directly by the induction coil,
`is
`minimized. The induction coil includes current loops
`which are configured so that the magnetic dipole mo-
`ment of each current loop is offset by the magnetic
`dipole moment of other current loops in order to mini‘
`mize the net magnetic dipole moment of the induction
`coil. One embodiment of the induction coil includes a
`conductor wound in the shape of a square prism. The
`current on a Jacent 51 e e ges o t e prism 1s 1n oppos1te
`d.
`-d
`d
`f h
`.
`-
`~
`~
`directions thus resultin in two airs of mutuall o -
`.
`’
`.
`.
`g
`p
`y
`1’
`P051113 “138116th dIPOIC moments-
`
`14 Claims, 6 Drawing Figures
`
`
`
`
`78
`
`HIGH FREQUENCY
`POWER SOURCE
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 001
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 001
`
`

`

`US. Patent
`
`Dec. 16, 1980
`
`Sheet 1 of2
`
`4,24o,om
`
`24
`
`
`
`
`
`/20
`
`28
`
`
`
`
`
`‘
`
`26/1
`
`
`
`
`
`l
`i
`30
`H ii ii
`
`\_\
`22?:/ "
`
`FM 3
`
`42
`
`42
`
`
`42
`
`>
`
`.
`
`40
`
`'
`
`42
`
`40
`
`FIG: 3
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 002
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 002
`
`

`

`US. Patent
`
`Dec. 16, 1980
`
`Sheet 2 of2
`
`4,240,010
`
`
`
`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 minimal far field electromagnetic radi-
`ation levels.
`'
`BACKGROUND OF THE INVENTION
`
`This invention relates to electrodeless fluorescent
`light sources excited by_ high 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 require large,
`heavy and expensive ballasting circuits for operation at
`line frequencies. The low pressure glOw discharge in
`mercury vapor that provides the phosphor excitation'in
`fluorescent lamps is usually powered by a current at 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 of the 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 advantage of 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 frequency electric field to ionize
`a gaseous radiating medium. Ferrite cores are utilized to
`couple energy to the discharge. A great variety of ge-
`ometries is 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 MHz range, and no ferrites are needed. In U.S. Pat.
`No. 4,010,400 issued Mar. 1, 1977 to Hollister, radio
`frequency power is coupledto a discharge medium
`contained in a 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
`MHz to 300 GHz range, was disclosed by Haugsjaa et
`al.
`in pending U.S. application Ser. No. 959,823 filed
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`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 radiation is 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 discharge of a fluorescent lamp the 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 through a coil or ferrite 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
`other classes 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 a1 wherein a power source for an
`electrodeless fluorescent lamp was designed to elimi-
`nate second harmonics.
`
`SUMMARY OF THE INVENTION
`
`It is an object of the present invention to provide
`improved
`electrodeless
`fluorescent
`light
`sources
`wherein high frequency power is 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. The elec-
`trodeless lamp has an envelope made of a light transmit-
`ting substance. The lamp envelope has on its 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 which is the vector sum of
`said individual magnetic dipole moments. The current
`loops are configured so that each individual magnetic
`dipole moment is offset by other individual magnetic
`dipole moments in 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
`
`

`

`4,240,010
`
`3
`field electromagnetic radiation, produced directly by
`said induction coil means, is minimized.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`In the Drawings:
`FIG. 1 is a simplified sectional view of an electrode-
`less fluorescent light source according to the prior art.
`FIG. 2 is a perspective view of an induction coil
`according to one embodiment of 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 embodiment of 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 embodiment of the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`10
`
`15
`
`20
`
`4
`prism, up edge 28, across the top of the prism, down
`edge 30,,and across the bottom of the prism to input 22.
`This configuration results in two conductors along each
`side edge of the square prism. While other winding
`sequences can be used, the important requirement is that
`current at any instant of time must flow in opposite
`directions on adjacent side edges and in the same direc-
`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 shown in 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 because of the alternating input cur-
`rent.
`
`The induction coil 20 results in a much lower level of
`far field radiation than the helical coil used in the prior
`art. Considering individually each side face of the
`prism, current circulates around that face and produces
`a dipole radiation pattern. FIG. 3IS a top view of induc-
`tion coil 20 and illustrates the magnetic dipole moment
`40 produced'by the current loop on each face of the
`prism. Also shown in FIG. 3 are the magnetic filed lines
`42 generated by induction coil 20. The fields produced
`by adjacent conductors are of opposite polarity. These
`are the fields which interact with the electrodeless lamp
`fill material as Will be discussed hereinafter. The dipole
`moments from opposite sides of the prism also are of
`opposite polarity. Thus, when viewed from the far field,
`or distances much greater than the dimensions of induc-
`tion coil 20, the dipole contribution from each face of
`the prism is offset by the Contribution from the opposite
`face to give a net dipole moment of approximately zero.
`The resulting dipole radiation field in a practical induc-
`tion coil 20 is not exactly zero because of imperfections
`in the coil construction and because of second order
`effects. One requirement for the above discussion to
`hold true is that the length'Of the conductor used to
`form induction coil 20 be small in comparison with the
`wavelength at the frequency of operation. This is neces-
`sary to insure that there is no phase retardation between
`radiation from dipole moments 011 opposite faces of the
`prism. It is also required that the separation between
`opposite faces of the prism be small in comparison with
`the wavelength of the excitation signal. Therefore,
`when an electrodeless fluorescent light source is oper-
`ated at 40.68 MHz, which has a wavelength of about 7.4
`meters, the maximum dimensions of induction coil 20
`should be a few centimeters to avoid problems of phase
`retardation.
`
`The induction coil 20 shown in FIG. 2 is one example
`of induction coil geometries which meet the require-
`ments of the present invention. The essential require-
`ment is that each dipole moment be offset by one or
`more dipole moments of opposite polarity to minimize
`the net magnetic dipole moment so that the far field
`electromagnetic radiation level produced directly by
`the induction coil is minimized. The net magnetic dipole
`moments of the induction coil is the vector sum of the
`individual magnetic dipole moments produced by each
`current loop of the induction coil. Thus,
`the prism-
`shaped induction coil can have a rectangular base as
`well as a square base. Also, the side faces of the prism
`can be parallelograms as well as rectangles. The dipole
`moments produced by opposite faces of such induction
`coils offset each other. In general, the base of the prism-
`shaped induction coil can be regular polygonal where
`the polygon has an even number of sides, for example,
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 005
`
`For a better understanding of the present invention,
`together with other and further objects, advantages and
`capabilities thereof, reference is made to the following
`disclosure and appended claims in connection with the
`above-described drawings.
`light
`A typical prior art electrodeless fluorescent
`source is shown in FIG. 1. It includes an electrodeless
`lamp 10 with a phosphorcoating 12, an induction coil
`14, and a high frequency power source 16. The elec-
`trodeless lamp 10 has an envelope made of a light trans-
`mitting substance such as glass and encloses a fill mate—
`rial such as mixtures of mercury and an inert gas which
`emit ultraviolet light during discharge. High frequency
`power is coupled to the discharge by induction coil 14.
`The phosphor coating 12 on the inner surface of lamp
`10 emits visible light upon absorption of ultraviolet light
`from the discharge. Such a light source is shown in U.S.
`Pat. No. 4,010,400. The induction coil 14 is wound in a
`helical configuration and radiates
`an appreciable
`amount of energy at the frequency of operation.
`According to the present invention, unique configu-
`rations of the induction coil are utilized to reduce the
`radiated high frequency energy. Referring now to FIG.
`2, there is shown an induction coil 20 having the general
`shape of a square prism. As used in this disclosure, the
`term “induction coil” is intended to include any config-
`uration of an elongated conductor which has the pur-
`pose of coupling magnetic fields to an electrodeless
`lamp and is not limited to a series of spirals or rings. The
`induction coil 20 is formed from insulated wire and can
`be supported by an insulating form of dielectric mate-
`rial. Alternatively, the induction coil 20 can be formed
`from wire which has sufficient stiffness to be self—sup-
`porting. Regardless of how the induction coil 20 is
`supported, it can be visualized as outlining an imaginary .
`square prism which has four rectangular side faces and
`two square end faces. The prism thus has four side edges
`formed by the intersections of the four side faces. As
`shown in FIG. 2, the conductor forming induction coil
`20 starts at input 22 and runs up edge 24, across the top
`of the prism and down edge 26. The conductor then
`runs across therbottom of the prism, up edge 28, across
`the top of the prism, and down edge 26. From here, the
`conductor runs across the bottom of the prism, up edge
`24, across the top of the prism, and down edge 30. Fi-
`nally,
`the conductor runs across the bottom of the
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Momentum Dynamics Corporation
`Exhibit 1012
`Page 005
`
`

`

`4,240,010
`
`preferred dimensions of square prismatic induction coils
`are in the range of 1 cm to 5 cm square by 2 cm to 10 cm
`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 conductor starts 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 40
`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 of time.
`While the conductor on each face of the prism does
`not form a complete loop, the current flow111 the side
`edges of each face results in a dipole moment which is
`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 means for excitation of 55
`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
`which is 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-
`
`45
`
`50
`
`60
`
`65
`
`‘5
`regular hexagonal or regular octagonal. An induction
`coil in the shape-0f a regular polygonal prism according
`to the present invention has an even number of side
`faces and an even number of 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 ends of the
`coil. The dipole moment produced by the conductor on
`each face of the regular polygonal prism is offset by the
`dipole moment of one or more other conductors. In the
`case of a rectangular induction coil, the dipole moment
`produced by each face is 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 of three.
`The maximum number of sides on the prism-shaped
`induction coil has two limitations. The first, 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 problems of 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~
`tance of the coil. Based on the above considerations,
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`6
`monies 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 made of a light
`transmitting substance, such as glass, and encloses a 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 through its 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, with a
`cavity for induction coil 72. In another configuration, a
`tubular. electrodeless lamp is 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. Two pre-
`ferred frequencies of operation are 13.56 MHz and 40.68
`MHz which 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.
`Any suitable 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 Adams et 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
`. Hz line frequency input. The light source according to
`the present invention can also include a 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 of the 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 tune it
`to resonance at 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.
`Two loops of plasma current 84 and 86 are illustrated 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 phosphor coating
`to produce visible light.
`The limitations, discussed above, on the geometry of
`induction coil 72 are related to excitation of the lamp as
`
`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 number of side
`the conductive segments are moved closer together,‘as
`edges formed by the intersections of said 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 instant of time, current in the con-
`able to have the plasma current fill the entire lamp
`ductor on adjacent side edges of said 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 including a plurality of current
`An electrodeless fluorescent light 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 which is
`lamp had an outside diameter of 4.7 cm, an inside diame—
`the vector sum of said individual magnetic dipole
`ter of 2.5 cm and a length of 13 cm. The fill material
`moments, said current loops being configured so
`included 3 milligrams of mercury and 6 torr'of neon' 20
`that each individual magnetic dipole moment
`is
`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 far field elec-
`consisted of 60 weight percent of (Y, Eu)2 03 and 40
`tromagnetic radiation, produced directly by said
`weight percent of (Ce, Tb)MgAl oxide. 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.
`An alternative 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
`half 94 is wound in one direction while the upper half 96
`includes a high frequency power source having its 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 upper half 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
`power source, means for reducing harmonic frequency
`offset each other in the far field. Thus, the level of
`components of the output power produced by said
`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 used in 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
`adjacent to the upper half 96 of induction coil 90 and the 50 source is in the range from 1 MHz to 100 MHz.
`second plasma loop'1s adjacent to the lower half 94 of
`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 what is 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 those skilled 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 of the inven-
`an electrodeless lamp having an envelope made of a
`tion as defined by the appended claims.
`light transmitting substance, said envelope having
`Whatis claimed1s:
`on its inner surface a phosphor coating 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 1nner surfaceaphosphor 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
`
`9
`ing a conductor configured to generally outline the
`shape of a rectangular prism having four side faces
`and four side edges formed by the intersections of
`said side faces, said conductor being configured to
`run parallel to and coincide with said side edges in
`such a direction that, at any instant of time, current
`in the conductor on adjacent side edges of said
`prism flows toward opposite ends of said prism and
`current in the conductor on diagonally opposite
`side edges of said prism tlows toward the same end
`of said prism, said induction coil means thereby
`including a plurality of current loops, each having
`an individual magnetic dipole moment which emits
`electromagnetic radiation, and having a net mag-
`netic dipole moment which is the vector sum of
`said individual magnetic dipole moments, said cur-
`rent loops being configured so that each individual
`magnetic dipole moment is offset by other individ-
`ual magnetic dipole mOments in order to minimize
`said net magnetic dipole moment, whereby the
`magnitude of the far field electromagnetic radia-
`tion, produced directly by said induction coil
`means, is minimized.
`10. The electromagnetic discharge apparatus as de-
`fined in claim 9 wherein said electrodeless lamp has a
`cavity therein and said induction coil is located in said
`cavity.
`11. The electromagnetic discharge apparatus as de-
`fined in claim