Electron-stimulated luminescence

Electron-stimulated luminescence (ESL) is production of light by cathodoluminescence, 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.

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.{{cite web |archive-url=https://archive.today/20120717023417/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/PTO/srchnum.htm&r=1&f=G&l=50&s1=7834553.PN.&OS=PN/7834553&RS=PN/7834553 |url-status=dead |archive-date=17 July 2012 |display-authors=etal |access-date=31 May 2016

Unlike fluorescent lamps, which produce light through the electrical excitation of mercury vapor, ESL lamps do not use mercury. 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.