High output low pressure mercury (LPM) discharge UV lamps have been briefly introduced. In order to measure the 254 nm radiant efficiency simply and preciously, Keitz formula was used and its advantage was illustrated. The LPM lamps had outer diameter of 19 mm (T6). The buffer gases are neon (65%) and argon (35%) with total pressure 1-10 Torr (133-1333 Pa). The lamps were operated with cold spot temperatures from 20°C to 80°C and discharge current from 0.8 A to 2.0 A. The electric field, input power, 254 nm UV irradiance and irradiance of other Hg lines from 265 to 579 nm in positive column were measured. The radiant power of each wavelength can be calibrated according to the 254 nm output and the Keitz formula. It was shown that the radiant efficiency of 254 nm can reach a maximum of above 40% at cold spot temperature 45-47 °C and current 1.6 A for filling pressure less than 3 Torr. The optimal mercury vapor pressure was 1.2 to 1.4 Pa. The output percentage of other Hg lines was below 5%. With the decrease of buffer gas pressure, the 254 nm radiant efficiency increased obviously.
The electric field and absolute radiance of 13 strong lines in the positive column of narrow bore T2 (outer diameter 7 mm) low-pressure Ar-Hg discharges were measured experimentally, which includes 11 Hg lines ranging from 185 to 579 nm and 2 Ar lines of 811, 842 nm. The discharges were operated with different argon filling pressure ranging from 2 to 10 Torr (corresponding to 266 to 1333 Pa), for discharge currents 20-200 mA and cold spot temperature 20-80 °C (0.16-11.8 Pa Hg vapour pressure). The Koedam factors of important emission lines were also measured for various discharge parameters, in order to convert radiance to exitance, whereafter the radiant power of all the lines except 185 nm, could be calculated and their radiant efficiency could be compared as well. Considering the absorption of 185 nm radiation in air, the ratio of the radiance at 185 nm to that at 254 nm was measured instead of its Koedam factor for current 80-200 mA and cold spot temperature 20-60 °C. Therefore, 185 nm radiant power was derived indirectly from that of 254 nm in corresponding discharge conditions. According to our measured results, the argon pressure for the maximum production of 254 nm radiation is around 5 Torr. It is showed that the optimum cold spot temperature for 254 nm radiant efficiency is higher than 50 °C, which is consistent with the temperature dependence on the tube diameter. With increasing discharge current and cold spot temperature, 185 nm radiant power has the similar tendency to that of 254 nm, while the fraction of electrical power converted to 185 nm radiation increases slightly with these parameters. Generally, the ratio of radiant power at 185 nm to that at 254 nm is higher than 0.2. For evaluating the energy balance of the positive column as well as the luminous efficacy of the fluorescent lamp product, the radiant powers of other strong lines also has significantly effect though they are considerably smaller than that of 254 nm and 185 nm. Besides, it must be taken in consideration that mercury depletion on the axis of positive column is serious for T2 narrow tube discharge especially at low Hg vapour pressure and high current.
Rare earth iodides are commonly used in ceramic metal halide (CMH) lamps, a kind of high intensity discharge (HID) lamp. Rare earth metals in the discharge plasma inside the arc tube contribute to the superb performance of CMH lamps. On the other hand, however, polycrystal alumina (PCA) arc tube corrosion due to its reaction with rare earth iodides causes the deterioration of parameter maintenance, and constrains lifetime of the lamps. In this study, PCA arc tubes with specific rare earth iodides are prepared. Aging tests up to 2000 hours are conducted to evaluate the effects of single rare earth iodides on lamp performance. Also X-ray analysis shows the corrosion content of PCA arc tube by different rare earth iodides. The result shows that PCA tubes with single rare earth iodides are more corrosive than the mixture of various rare earth iodides.
As a rapid developing solid state lighting, light-emitting diodes (LEDs) have great potential in application of road lighting, but their performance evaluation in a long term are still lacked. In situ and laboratory measurements were conducted for the purpose of comparing the characteristic parameters and lighting performance of three kinds of street lamps: LEDs, high pressure sodium (HPS) lamps and ceramic discharge metal halide (CDM) lamps. The results of laboratory measurements in 2000 hours show the three kinds of lamps have almost the same initial luminaire efficacy, which lead to the average road illuminance is proportion to the lamp power. The results of road illuminance distribution measurements in 3000 hours show LEDs have better color rendering index, longitudinal uniformity of illuminance, and maintenance of road illuminance than HPS and CDM lamps.
Most of the measurement methods for blue light hazard (BLH) evaluation are based on radiance, which are too complex and hard to find out the highest radiance. We proposed a methodology for measurement of BLH with imaging luminance meter. We measured the relative spectral power distribution with a spectrometer and the maximum luminance with an imaging luminance meter for LEDs and compact fluorescent lamps, and calculated the BLH weighted radiance. The BLH efficacy and the upper limit of luminance with blue light safe of various light sources were also calculated on the basis of the BLH weighted function. The results show absolute blue light safe can be obtained if the luminance is limited to 100 kcd m2 for color temperature lower than 6500 K. LEDs with high color temperature, especially those without diffused window, have potential risk of BLH. Our method can be used in online measurement of the BLH of LEDs.
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