Measuring spot sizes of laser-excited phosphor ceramics with a goniophotometer

In packaging processes of laser lighting sources, the matching degree between excited laser spots and the sizes of phosphor conversion materials directly affects light efficiency of packaged light sources. The sizes of excited laser spots and conversion light spots need to be measured. Therefore, an effective spot measurement method is necessary. In practical applications, laser spots usually include circular spots and non-circular spots. This study proposes a method for measuring both circular spots and non-circular spots. A goniophotometer is used to measure luminous intensity distribution curves and average luminous intensity divergence angles of lighting sources. Spot sizes can be calculated according to the divergence angles. The spot sizes of the LD, YAG:Ce phosphor ceramic and Mn-doped red YAG:Ce phosphor ceramic in three directions are measured. The results show that the spot sizes of LD are 4.002, 1.467, and 1.126 mm, which shape is non-circular. The spot sizes of the YAG:Ce phosphor ceramic are 42.240, 42.762, and 43.242 mm, the spot sizes of Mn-doped red YAG:Ce phosphor ceramic are 39.594, 40.395, and 41.065 mm. This method is of great significance for spot control in laser lighting packaging.