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Cut-off street lamp using linear light source

The main feature of the optical performance of this type of lighting is that the peak light intensity must be as close to 65° as possible, the light intensity in the horizontal direction should be very close to 0°, and in the range of 0° to 30°, the light intensity should not exceed 80% of the peak light intensity.

Due to the strict limitation of horizontal light intensity, the method of using prisms on both sides of the lampshade to control the light beam is ruled out, because this will cause too much light to spill out from the side of the lampshade. Therefore, this lampshade must rely on the Reflector to control it so that no part of the lamp tube can be seen from the horizontal direction.

The Reflector can be installed in the white lamp trough. If a flat bowl-shaped cover is used under the lamp, the peak light intensity ratio of the lamp may be reduced to below 2.0 because the incident angle of light on the spherical surface can reflect a considerable amount of light in the light beam back to the lamp trough. Therefore, the slope of the edge of the bowl-shaped cover must be at right angles to the direction of the light beam, as shown in Figure 20-13. It should be noted that the light transmission effect of the curved part of the bowl-shaped cover cannot destroy the smoothness of the light distribution curve, nor can it reflect more light in the horizontal direction. If the white trough reflects too much light into the 0° to 30° area, where the light intensity is often limited by common lamp specifications, the bottom of the bowl-shaped cover must be designed in a style suitable for diffusion.