Electron stimulated luminescence
Encyclopedia
Electron Stimulated Luminescence (ESL) is light produced by accelerated electrons hitting a phosphor
(fluorescent
) surface in a process known as cathodoluminescence.
The light generation process is similar to a cathode ray tube
(CRT) but lacks magnet
ic or electrostatic
deflection.
A cathodoluminescent lighting system has a light emitting device having a transparent glass envelope coated on the inside with a light-emitting phosphor layer. Electrons emitted from a cathode strike the phosphor; the current returns through a transparent conductive coating on the envelope. The phosphor layer emits light through the transparent face of the envelope. The system also has a power supply for providing at least five thousand volts of power to the light emitting device, and the electrons transiting from cathode to anode are essentially unfocused. Additional circuits allow triac-type dimmer
s to control the light level. The light has a rated color rendering index of 85. The energy consumption is less than that of an incandescent light bulb
. The lifetime is longer than an incandescent light bulb. Light is generated instantly when power is applied. The cost is estimated at per bulb in 2010.
Incandescent bulbs produce light by heating a wire with current. Fluorescent lamp
produce light by exciting mercury vapor
in a plasma process
which in turn radiate UV light towards a phosphor layer that converts the light into the visible spectrum.
ESL lamps do not use mercury
in the lighting process The first commercially available ESL product is a reflector bulb in the R‐30 shape which was briefly available through the manufacturer's web site but direct sales were stopped as of May 23, 2011, in anticipation of outsourcing this activity. An A19-type "Edison" light bulb is expected to be ready for market by mid-2011.
Independent product testing and anecdotal feedback suggests ESL boasts better light quality than both LED and CFL bulbs, with full dimmability. Drawbacks included a slightly larger-than-normal base (which favors newer recessed "can" installations) and a slight delay in illumination when switched on, similar to CFLs.
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
(fluorescent
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
) surface in a process known as cathodoluminescence.
The light generation process is similar to a cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
(CRT) but lacks magnet
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
ic or electrostatic
Electrostatics
Electrostatics is the branch of physics that deals with the phenomena and properties of stationary or slow-moving electric charges....
deflection.
A cathodoluminescent lighting system has a light emitting device having a transparent glass envelope coated on the inside with a light-emitting phosphor layer. Electrons emitted from a cathode strike the phosphor; the current returns through a transparent conductive coating on the envelope. The phosphor layer emits light through the transparent face of the envelope. The system also has a power supply for providing at least five thousand volts of power to the light emitting device, and the electrons transiting from cathode to anode are essentially unfocused. Additional circuits allow triac-type dimmer
Dimmer
Dimmers are devices used to vary the brightness of a light. By decreasing or increasing the RMS voltage and, hence, the mean power to the lamp, it is possible to vary the intensity of the light output...
s to control the light level. The light has a rated color rendering index of 85. The energy consumption is less than that of an incandescent light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
. The lifetime is longer than an incandescent light bulb. Light is generated instantly when power is applied. The cost is estimated at per bulb in 2010.
Incandescent bulbs produce light by heating a wire with current. Fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
produce light by exciting mercury vapor
Mercury-vapor lamp
A mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb...
in a plasma process
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
which in turn radiate UV light towards a phosphor layer that converts the light into the visible spectrum.
ESL lamps do not use mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
in the lighting process The first commercially available ESL product is a reflector bulb in the R‐30 shape which was briefly available through the manufacturer's web site but direct sales were stopped as of May 23, 2011, in anticipation of outsourcing this activity. An A19-type "Edison" light bulb is expected to be ready for market by mid-2011.
Independent product testing and anecdotal feedback suggests ESL boasts better light quality than both LED and CFL bulbs, with full dimmability. Drawbacks included a slightly larger-than-normal base (which favors newer recessed "can" installations) and a slight delay in illumination when switched on, similar to CFLs.
See also
- CRT projectorCRT projectorA CRT projector is a video projector that uses a small, high-brightness CRT as the image generating element. The image is then focused and enlarged onto a screen using a lens kept in front of the CRT face. Most modern CRT projectors are color and have three separate CRTs , and their own lenses to...
- Cathode ray tubeCathode ray tubeThe cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
(CRT) - ElectroluminescenceElectroluminescenceElectroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field...
- Electroluminescent displayElectroluminescent displayElectroluminescent Displays are a type of Flat panel display created by sandwiching a layer of electroluminescent material such as GaAs between two layers of conductors. When current flows, the layer of material emits radiation in the form of visible light...
(ELD) - Light through electric current - FluorescenceFluorescenceFluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
- Fluorescent lampFluorescent lampA fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
- Light through excited atoms in a plasma