US2107399A - Glow lamp - Google Patents

Description

P. L. SPENCER Feb. 8, 1938.

GLOW LAMP Original Filed Dec. 18, 1928 Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE oLowLAMP Application December 18, 1928, Serial No. 326,716 Renewed November 20, 1931 2- Claims.

This invention relates to glow lamps and par icularly to the use of such a lamp as a light valve. For certain purposes, such-as television and the photographic recording of sound, it is 5 desirable to have an actinically powerful source of light capable of instantaneous response to current variation.

My invention is based upon the fact that gases or vapors when in their natural or an excited state, have the property of selectively absorbing light of a particular frequency. 1 Modern theory-and experiments justify this consider that all substances have as their ultimate composition a nucleus or a charge of posi- 5 tive electricity and one or more electrons in spaced relation thereto, and having certain definite mo- .tions with respect to the nucleus. Thus, the hydrogen atom has a unit charge at the nucleus and. has a single electron revolving around it. As we go up the scale, the mass and charge of the nucleus increases with a correspondingly compensatory increase in the number of revolving electrons. As the number of electrons increases they assume certain orbits in accordance with a simple law. Thus, starting from hydrogen having one electron in a single orbit the series extends through all the elements to uranium having 92 electrons and disposed in 92 orbits.

When a particle is said to be ionized then at least one of the electrons has been removed from the system. In a natural state, such particles are in a condition of dynamic equilibrium. When ionized, the system has been placed in a condition of unstable dynamic equilibrium with the absorption of a certain quantum of energy. The actual value of this quantum of energy is a function of the number of electrons removed, as well as the original position of the electrons.

Instead of completely ionizing a particle, it is 40 possible, to merely remove an electron from one orbit and place it into an outer adjacent orbit. Such a particle is also in an unstable state. The assumption of this state is accompanied by the absorption of a particular quantum of energy.

. Such particles tend to resume their normal state,

in the first instance by adding an electron, and in the second instance, by the electron dropping back into its original orbit. When this resumption of normal state occurs, there is a flash of light emitted from the particle. This flash of light is the physical manifestation of a quantum of energy emitted. e

The ordinary method of ionizing and exciting particles is usually to bombard them with electrons. Impacts may result in ionization or in ex citation depending upon the electric field impelling the electron. However, this is not the only method of ionizing o1 exciting particles. It is obvious that if a certain frequency of light is the manifestation of a quantum of energy upon the resumption of a normal state by a particle, then the introduction of such a flash of light may result in its absorption by a particle with the assumption of an unstable state. I make use of this phenomenon in the following manner. 10

A region of excited and ionized gas is produced by any means, such as by electrodes so disposed, that a glow results. In this glow are a large number of excited and ionized gas particles. The

glow itself merely represents an integration of all 15 the tiny flashes emitted by particles when resuming their normal state. However, in such a region there are always a large number of particles in an unstable condition. Behind this glowing re gion, I dispose a source of illumination. Theoretically the ideal source would yield a monochromatic beam of such a frequency as to ionize or otherwise impart energy to excited particles of the gas or gases used. In practice, however, it is found that a tungsten filament operated at a 25 white heat is sufficiently satisfactory for all purposes in the art to which this invention relates.

The excited particles of gas within the glow region tend to absorb light of certain frequency emitted by the filament and in doing so become 30 ionized or excited in other ways. In absorbing this light, the light is entirely used up, and hence,

is not transmitted throughtheregion.

Light of a frequency corresponding to the ultra violet region has been foundto be equivalent to 35 between 3% and 5 volts as regards its effect on ionizing particles. As is well known, the ionizing voltage or the difference in potential down which an electron must fall to get up sufiicient speed to have an ionizing collision, is a property of a gas 40 or substance. Diflerent substanceshave different ionizing potentials. The same is true of the excitation -vo1tages. Thus, mercury has an ionization potential of 110.5 volts, while caesium has a potential of four volts. If excited mercury par- 45 ticles are present, a potential dilierence of from 3 to 5 volts is sufficient to ionize them. In lieu of this potential difference suflicient light energy of the particular frequency necessary, will perform the same thing. 50

By operating the filament at a White heat, a sufiicient amount of ultra-violet is emitted therefrom. When such light impinges on photographic sensitized paper, it is the ultra Violet portion which produces the greatest results. The effec- 55 absence of the ultra tiveness of the light decreases as the red region is approached. The glow region by selectively absorbing the ultra violet portion of the light thus robs the light of its most powerful constituent with respect to photographic effects. If a film having photographic sensitized material is run past at a sufliciently great speed, the entire violet from the filament will result in leaving the film substantially unexposed. By modulating the glow-region so that a' variable number of excited particles is produced, the amount of energy absorbed may be controlled.

The actual means for carrying this out comprises two concentric cylinders in a gas or vapor at a reduced pressure. These cylinders are at such a distance from each other that thegap between them is insulating. Hence, the discharge between them occurs in the central region enclosed by the inner cylinder. In line with this region is disposed a filament which is adapted to be operated at a bluish white heat. The cylinders, if desired, may be so coated with chemicals that the drop is thereby reduced.

Referring tothe drawing,-Figure l is a side view of a tube in section, with a diagrammatic circuit.

Figure 2 is a similar view of a modification. Figure 3 is a view of another modification. Within a glass tube l is a press 2 carrying wires 3, 4, 5, and 6. Wires 3 and 4 support members l3 and M respectively. As shown, member 13 'comprises a cylindrical portion 23 whichtapers down to a smaller cylindrical portion 24. Member l4 surrounds the smaller cylindrical portion 24. Wires 5 and 6 support a filament l5 within portion 23 of member l3. The tube is exhausted and freed oi occluded gases in accordance with customary practice and thereafter filled with a quantity of gas or vapor at a low pressure. The.

gas may be helium, argon, neon, either alone or in combination with each other. Iodine or any of the halogens may be used, either alone "or in combination with each other or in combination with one or more of'the rare gases. The pressure is preferably around 6-8 mm. of mercury.

The distance between 14 and 24 is such that with the gas pressure used, it is insulating. Filament' i5 is raised to an intense white heat by means oi';a suitable battery A. I Asuitable source of potential here shown as a batteryB, but which might be any suitable source, is connected across electrodes l3 and I4. Since the distance between l4 and 24 is insulating, the discharge fills the inside of 24 and thus produces an intense glow therein. In order to modulate this discharge, a

transformer '1 receives modulating impulses from any well-known means indicated diagrammatically at M. The transformer T is connected across battery B through a condenser C. In this way, the glow is'varied in accordance with modulating impulses. The variation of the glow will result in a variable number of excited gas particles being produced. Such a variable number will constitute a variable load for the absorption i vlig glow discharge this case, the

,combination with an envelope,

of the proper light energy emitted from the filament.

the glow discharge emit a minimum of actinic t and for this reason, I prefer iodine or other halogens to the rare gases, although the latter might be used in combination with the argon. 0f the rare gases, neon is the leasfdesirable because'of its highly actinic radiation.

when filament l5 burns at a white heat, it emits considerable actinic light within member l3. The glow discharge shields the filament from the photo-electrically active substance or apparatus used in conjunction therewith. By modulating the glow, varying amounts of actinic energy from the filament are absorbed thus resulting in a variable transmission 01 actinic energy from the filament through the glow region.

It is desirable that the gas or vapor used within 24 completely In Figure 2, the member l4 has been omitted I and the discharge takes the filament I; The filament-is energized to a white heat while acting as one o! the electrodes of the glow discharge.

In Figure 3, the two electrodes between which a occurs are H and 24 and both of substantially the same length, but of different diameter. Electrode i4 carries a shield-l1 to cut of! any undesired radiations from [5 whichmight travel outside of electrodes 24 and i4. In glow discharge is concentrated on the inside of electrode 24.

In this way, by the production of a steady source of illumination and a variable source, I may vary the amount of luminous energy available from said steady source. Hence, in the broader aspects 01' my invention I have devised a light valve in which the valve element itself is a region having light therein, the structure serving as a variable intensity lamp.

I claim:

1. A yariable intensity lamp comprising the of an attenuated atmosphere within the envelope, a filament to emit actinic rays, and concentric cylindrical electrodes. adjacent the filament forming a path therethrough and so positioned that upon activation a glow. discharge is produced between the electrodes and in the vicinity of the said source of rays, whereby some of the actinic rays will be absorbed by PERCY L. SPENCER.

place between l3 and a pair. of concentrically

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