Blu-ray Disc/DVD互換光学ヘッドの熱設計(熱工学,内燃機関,動力など)  [in Japanese] Thermal Design of Blu-ray Disc/DVD-Compatible Optical Heads(Thermal Engineering)  [in Japanese]

We developed a method for designing the thermal properties of an optical head for a Blu-ray^<TM> Disc (BD) apparatus. This optical head contains two laser diodes for BD and DVD compatibility, and the higher the operating temperature at which the laser diode emits a beam of light, the shorter its life-time becomes. Therefore, reducing the temperature increase of both laser diodes is necessary to obtain high reliability. First, we expressed the temperature increase of a laser diode as a summation of the products of the following three terms. The first term is the power dissipation of an electric component. The second term is a ratio of the amount of heat flow into the laser diode from the electric component to the total amount of its power dissipation. The third term is the summation including all thermal resistances between the laser diode and the ambient on the whole heat transfer paths from the electric component to the ambient via the laser diode. Then, by taking this interpretation into consideration, we designed the position of the laser driver IC, which dissipates the largest amount of electric power in the optical head. As a result, there was a 1/3 decrease in the amount of heat flow into each laser diode from the laser driver IC compared to that of the conventional optical head, and the calculated temperature increase of the laser diodes for BD and DVD were 10K or less and 15K or less, respectively.