Electron-stimulated luminescence (ESL) is production of light by cathodoluminescence,[1][2][3][4] i.e. by a beam of electrons made to hit a fluorescent phosphor surface. This is also the method used to produce light in a cathode ray tube (CRT). Experimental light bulbs that were made using this technology do not include magnetic or electrostatic means to deflect the electron beam.[5]
A cathodoluminescent light has 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 has a power supply providing at least 5kVDC to the light emitting device, and the electrons transiting from cathode to anode are essentially unfocused. Additional circuits allow TRIAC-type dimmers to control the light level.[6] Sample produced with lights produced so far have a color rendering index of 90. The energy consumption can be 70% less than that of a standard incandescent light bulb. Claimed lifetime can be as long as 10,000 hours which is more than ten times that of a standard incandescent light bulb.[7]
Unlike fluorescent lamps, which produce light through the electrical excitation of mercury vapor, ESL lamps do not use mercury.[8] The first commercially available ESL product was a reflector bulb.
Drawbacks include high weight, a slightly larger-than-normal base and – as with all cathode ray tubes – when switched on, a slight delay before illumination begins and a static charge which attracts dust to the bulb face. As of 2016 the cost is higher and claimed efficiency is less than half that of commercially available LED bulbs, although it is considerably better than that of traditional incandescent lamps.[9]
History
editIn 1958, Ferranti introduced a line of flood beam CRT-type stroboscope lamps.[10]
Following delays, one company, called Vu1 Corporation, released ESL lamp samples in 2011.[11] The company has not continued in operation.
See also
editReferences
edit- ^ Melanson, Donald (17 September 2009). "Vu1 Corporation sees bright future for ESL light bulbs". engadget. AOL Inc. Retrieved 31 May 2016.
- ^ Zyga, Lisa (16 September 2009). "Company Claims ESLs to be the Future of Light Bulbs (w/ Video)". Phys.org. PhysOrg.com. Retrieved 31 May 2016.
- ^ Hornyak, Tim (16 September 2009). "Are ESL bulbs better than CFL or LED?". CNET. CBS Interactive Inc. Retrieved 31 May 2016.
- ^ Nitz, Brian (12 March 2012). "Are ESLs A Mercury-Free Replacement for CFL Lights?". Green Prophet. Green Prophet. Retrieved 31 May 2016.
- ^ Vestel, Leora Broydo (9 April 2009). "The Promise of a Better Light Bulb?". The New York Times. Retrieved 31 May 2016.
- ^ Hunt; et al. (16 November 2010). "United States Patent 7,834,553". US Patent & Trademark Office, Patent Full Text and Image Database. Archived from the original on 17 July 2012. Retrieved 31 May 2016.
- ^ Ravindran, Sandeep (18 September 2009). "Newest Lightbulb Tech Combines Advantages of Incandescent, Fluorescent, and LED". Popular Science. Popular Science. Retrieved 31 May 2016.
- ^ "Will ESL Light Bulbs Beat LEDs?". Forbes. 22 November 2010. Retrieved 31 May 2016.
- ^ Provey, Joe (26 January 2011). "ESL Lightbulbs - DIY Product Review". DIY life. AOL Inc. Archived from the original on 5 March 2012. Retrieved 21 May 2016.
- ^ "Vacuum light sources - High speed stroboscopic light sources" (PDF). Ferranti Instruments. August 1958. Archived from the original (PDF) on 14 March 2019. Retrieved 18 January 2020.
- ^ "Vu1 Light Bulb Delayed (Again)". 4 April 2011.