We developed a method for improving the luminous flux of fluorescent lamps. The phosphor layer in fluorescent lamps is generally not uniformly thick because the phosphor suspension is poured into a vertical glass tube. We examined the relationship between the luminous flux and uniformity of the phosphor layer thickness to determine the optical thickness. By changing the thickness ratio between the ends of the lamp from 10:6 to 10:8 we improved the luminous flux by 0.9%. Changing the ratio from 10:8 to 10: 10 improved it only 0.2%. An improved luminous flux will improve the efficiency of fluorescent lamps.
Two methods are used for color matching: visual color matching and CCM (computerized color matching) which is now used quite frequently. Although CCM decrease the color difference more easily, color correction must be repeated in the case of poor color development due to the limited color reproducibility. There is no CCM system to display coloring reproducibility. A previous report described how coloring reproducibility can be displayed by using the spectral differences between the measured and CCM simulated spectral reflectance of color matching samples. The main point of the research reported here is identification of the coloring agents causing poor coloring reproducibility. It is especially important to identify the achromatic coloring agent. It become possible by the following methods. The spectral difference between the measured and simulated spectral reflectance of the abnormal coloring sample includes the coloring error and regular simulated error. The coloring error is calculated with deducting the regular simulated error. Identification of abnormal coloring agent is described on the change of recipe based on the cause of coloring error.
The diffusion characteristics of mercury vapor in small-diameter cold cathode fluorescent lamps used for backlighting liquid-crystal displays have been investigated. A cold cathode fluorescent lamp in which the mercury was concentrated at one side of the lamp was operated at 50kHz AC, and the increase in light output at three different axial positions was measured. The inner diameter of the lamp was varied from φ1.2mm to φ3.8mm. The lamp current of each lamp was varied from 3mA to 10mA. Calculation of the mercury diffusion coefficient at each position showed that the mercury diffused more slowly the smaller the diameter and the higher the discharge current.
An electronic ballast is described that uses fewer parts and costs less than conventioal ballast, which require separate switching element and control units for the half-bridge inverter and power-factor-correction (PFC) circuits because these circuits operate independently. In the proposed ballast, the switching element of the half-bridge inverter works as a buck-boost converter, eliminating the need for a PFC circuit. Even though it has fewer operating parts, the proposed ballast still reduces the number of harmonic components in the input current to below that specified by IEC Standard 61000-3-2 for Class C equipment.
An electronic ballast is described that uses fewer parts and costs less than conventioal ballast, which require separate switching element and control units for the half-bridge inverter and power-factor-correction (PFC) circuits because these circuits operate independently. In this paper, the operation of an electronic ballast in which the switching element of the half-bridge inverter works as a buck-boost converter has been analyzed and harmonic components that an input current included is calculated theoretically. The proposed ballast reduced the harmonics component in the input current to below by IEC Standard 61000-3-2 for Class C, because the amplitude of a sine wave is kept than 2.6 times of the amplitude of a rectangular wave.