This is the memorial Iecture for late Prof. Nakano. After explaining various modes of light production, investigations on phosphorescence and allied subjects are reviewed up to date, and a new proposal for illumjnation is put forward.
Then the light cone is given, the illumination vector is settled. The fours of light cone considered are pyramid, elliptic cone, and circular cone. The magnitude and direction of the vectors are calculated. As the examples of the above discussion, the calculations of the Cue to quadric source are shown.