Qhov pib ua lub teeb thaum ntxov Cov khoom siv nyob rau lub sijhawm ntawd yog gaasp, emitting liab teeb (λp =650 nm). Nrog kev tsav tsheb tam sim no ntawm 20 ma, qhov luminous flux tsuas yog ob peb txhiab ntawm lub lumen, uas ua rau lub lumen, uas ua rau muaj lumined efficacy ntawm kwv yees li 0.1 lumen / watt.
Nyob rau hauv nruab nrab-1970s, kev qhia txog hauv thiab n} {{{{=555} =590 luminous efficicacy tau txhim kho rau 1 lumen / watt.
Thaum ntxov xyoo 1980s, Gaalas coj teeb pom kev, ua kom liab liab ua kom tiav txoj kev lumous efficacy ntawm 10 lumens / watt.
Thaum xyoo 1990, kev vam meej ntawm ob cov ntaub ntawv tshiab - lub teeb thiab xiav thiab xiav} Txhim kho cov luminous equicts ntawm cov coj. Xyoo 2000, tus qub tau muab cov teeb nrog lub lumens ib qho ntawm 50 lumens nyob rau hauv thaj av liab thiab txiv kab ntxwv (λp}=530 nm).
