1. Rotation and symmetry
The luminaire employs a rotationally symmetric reflector and mounts the axis of symmetry of the source with a rotationally symmetric light distribution along the axis of the reflector. The iso-intensity curves of such lamps are concentric.
In the case of single-lamp illumination, the illumination spot on the illuminated surface has an illuminating unevenness, but when the illumination is multi-lighted, the spots are superimposed on each other to produce a satisfactory illumination effect. For example, hundreds of rotating symmetrical spotlights are commonly used in stadiums and installed on high towers around the stadium to achieve high illumination and high uniformity.
2. Two symmetrical plane shapes
The iso-intensity curve of this type of floodlight has two planes of symmetry. Most of the luminaires use a symmetrical cylindrical reflector and the linear light source is mounted along the cylinder axis.
3. A symmetric plane line
The equal intensity curve of the luminaire has only one symmetry plane (Fig. 2). The luminaire uses an asymmetric cylindrical reflector or a symmetrical cylindrical reflector plus a grid that limits light. The most typical is the sharp cut-off block retracting light distribution. Such a light intensity distribution single lamp can obtain a satisfactory illumination distribution.
The iso-intensity curves of such lamps do not have a plane of symmetry. It is mainly used for light-mixing lamps of different kinds of light sources with different light intensity distributions and special lamps designed according to the specific lighting requirements of the place of use.