| 摘要 |
PURPOSE:To minimize defocusing due to the variance of temperature to improve the precision of recording and reading by selecting properly the coefficient of linear expansion of a member, which connects a collimator lens and a semiconductor laser, to minimize the occurrence of defocusing. CONSTITUTION:Since a collimator lens 11 is pressed strongly to a collimator lens stopper 11 by a spring 15, the distance between the collimator lens 1 and a semiconductor laser 2 is kept constant. Meanwhile, the coefficient of linear expansion of a semiconductor laser supporting base 4 is denoted as alpha3, and lengths of individual parts are determined as shown in the figure. The temperature characteristic of the collimator lens is dependent upon the constitution of the collimator lens. A change rate W of the operating distance is so set that the operating distance is shorter according as the temperature rises. Consequently, conditions where the collimator lens is not defocused with respect to the variance of temperature are given by a formula. Thus, defocusing due to the variance of temperature is minimized to improve the precision of recording and reading. |
