Vertical light distribution - Let's go to school

...On a horizontal plane passing through the light center, the angle between a reference vertical plane that includes the lamp axis and another vertical plane is called the horizontal angle φ. The light distribution on this vertical plane is called the vertical light distribution, and the light distribution on the horizontal plane is called the horizontal light distribution. A vertical light distribution rotated 360 degrees horizontally around the lamp axis is called a symmetrical light distribution, and any other light distribution is called an asymmetrical light distribution.

*Some of the terminology that refers to "vertical light distribution" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…光中心を通る水平面上，灯軸を含む一つの基準鉛直面よりほかの鉛直面のなす角を水平角φという。この鉛直面上の配光を鉛直配光，水平面上の配光を水平配光という。一つの鉛直配光を灯軸を軸として水平角で360度回転した配光を対称配光といい，そうでない配光を非対称配光という。…

※「鉛直配光」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報