Although a cold cathode fluorescent lamp (CCFL), whose diameter is 4 mm, has been used for the backlighting of liquid crystal displays, it is being replaced by an LED. Thus, the CCFL seems to be vanishing from the backlighting field. However the CCFL has an excellent long life performance. If the CCFL could have a higher output on a par with the linear fluorescent lamp used in the general lighting whose diameter is 25 mm (FHF lamp), it would be possible to replace the FHF lamp with it because of its long lifetime and its easy control of the light distribution. We investigated the influence of the gas pressure on the performance of the positive column of a discharge lamp with a 4 mm diameter, and found that the electron temperature of this lamp is lower than that of a fluorescent lamp with a 25 mm diameter and that the higher electron temperature by decreasing the gas pressure could increase the lumen output and the efficiency of the positive column of the discharge lamp with the 4 mm diameter.
The filling gas pressure of mercury-free HID lamp is much higher than that of the mercury containing lamp. A high filling gas pressure leads to a high ignition voltage in mercury-free HID lamp and this makes the ballast with ignition circuit bigger and heavier in order to maintain the ignition reliability. Therefore, it is important to decrease the ignition voltage of mercury-free HID lamps. It is necessary to better understand how the discharge starts and grows in the HID lamp burner in order to decrease the ignition voltage. An ultra high speed camera was used for the discharge observation, the shutter speed of which is 5 ns. As a result, we found that a very weak discharge occurred outside the burner before the burner ignited. It is believed that this weak discharge influences the ignition condition from two points of view, which are the ultraviolet rays radiating from this discharge and the electric field distortion formed by the attached electric charge on the outside of the burner wall. We found that the attached electric charge on the outside of the burner wall strongly influences the ignition performance and that the ultraviolet radiation little influences the ignition performance.
Under the current lighting standard, a vehicle’s headlamps are not taken into consideration in the visibility evaluation for obstacles on the surface of a road based on the tunnel lighting. In this paper, we quantitatively evaluate the visibility for obstacles based on the total power revealing properties, while considering a vehicle’s headlamps and the tunnel lighting. As a result, in the case of a symmetric lighting system, the visibility of obstacles on the road based on the headlamps and tunnel lighting decreased at a point in vertical illuminance that was lower for a higher average road surface luminance. In contrast, a pro-beam lighting system showed that the obstacle visibility scarcely changed even if the headlamps were added, and that it is the effective in the terms of coordination of tunnel lighting and headlamps.
A mutual comparison of the measured values of the total-luminous-flux between the sphere photometers when using an integrating sphere in which the sizes differ was made, and the consistency was also considered. The same total-luminous-flux standard lamp was used to prevent affecting measured value to standard traceability. The LED lamps used for measurement were turned on for 100 hours or more. The reproducibility for all the lamps was less than ±0.2%. The total-luminous-flux of omnidirectional lamps with an angular luminous intensity distribution was the same as that for a standard lamp, which is accorded in less than 1% in the spheres. On the other hand, the total-luminous-flux of directional lamps was accorded in more than 1.5% in spheres. The low light flux value measured by using the integrating sphere with a 1- m o diameter is considered to be the influence of the lamp support stand and another structure in the integrating sphere. Since the measured value of the integration hemisphere is the same as that of the large integrating spheres, there is very little structure that is causing the error with it.