Halogen lamp

Abstract: White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm) and nUV (380-400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+) is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

Abstract: A retrofittable lamp using light emitting diodes as the illumination source, the lamp is fitted with any one of the common lamp bases and is intended as a retrofit for incandescent lamps having such bases in illuminated signs such as exit signs and the like. The invention contemplates the packaging of a number of light emitting diodes in a circuit usually having a current limiting device to allow LED operation at a desired current level. The light emitting diodes are placed within a standard glass or plastic bulb envelope in arrangements capable of providing even illumination from the lamp.

Abstract: Objective: The main goal of this study was the hardness evaluation of a composite resin cured by five LED (Light Emitting Diodes) based devices and a comparison with a conventional curing unit. The hardness test was used to compare the efficacy of both types of light source. Methods: The LED-based devices were made employing an array of LEDs (Nichia Chem. Ind., Japan) emitting light peaked at 470 nm. Composite resin (Z100, shade A3) was cured for 20, 40, 60, 120 and 180 s with each LED-based device and for 40 s with the halogen lamp. The composite samples were prepared with 0.35, 1.25 and 1.8 mm of thickness. Five samples of each set of parameters were done. The hardness evaluation was performed at the non-illuminate surface with three indentations for each sample. Results: All the samples cured by the LED-based devices showed inferior hardness values when compared with the halogen lamp at the typical curing time (40 s). The L6 (device composed of six LEDs) was the most efficient one of the LED-based devices. Its obtained irradiance was 79 mW/cm 2 , whereas the halogen lamp irradiance was of 475 mW/cm 2 . For the L6 device here presented, longer exposure times or a thinner resin layer are required to achieve reasonable hardness values. Significance: Besides the difference of irradiance when compared with halogen lamps, LED-based devices show to be a promising alternative curing instrument. Further development in instrumentation may result in devices even more efficient than conventional lamps.

Abstract: An advanced magneto-optical technique is described, which allows simultaneous determination of two mutually-conjugate parameters–Kerr rotation and reflectance magneto-circular dichroism–using a piezo-birefringent modulator. This technique provides a sensitivity of 0.002° for Kerr rotation at λ=500 nm with 12 nm resolution, using a halogen lamp (150 W) as the light source. The wavelength region covered by the method can be extended from 300–2500 nm by suitable selection of gratings and light detectors. The new technique was used to measure magneto-optical hysteresis loops for several wavelengths and magneto-optical spectra on an rf-sputtered amorphous Gd-Co film, and the results are reported here.

Abstract: An advanced magneto-optical technique is described, which allows simultaneous determination of two mutually-conjugate parameters–Kerr rotation and reflectance magneto-circular dichroism–using a piezo-birefringent modulator. This technique provides a sensitivity of 0.002° for Kerr rotation at λ=500 nm with 12 nm resolution, using a halogen lamp (150 W) as the light source. The wavelength region covered by the method can be extended from 300–2500 nm by suitable selection of gratings and light detectors. The new technique was used to measure magneto-optical hysteresis loops for several wavelengths and magneto-optical spectra on an rf-sputtered amorphous Gd-Co film, and the results are reported here.