本帖最后由 dongnanfei 于 2012-11-5 13:00 编辑

有谁知道那个英文标准对光束角进行了定义
能否贴出标准+金币哦
自己答算了
'beam angle' means the angle between two imaginary lines in a plane through
the optical beam axis, such that these lines pass through the centre of the front
face of the lamp and through points at which the luminous intensity is 50% of
the centre beam intensity, where the beam intensity is the value of luminous
intensity measured on the optical beam axis 1 metre from the light-emitting
surface;