| 摘要 |
PURPOSE:To minimize variation in the distance between a light emission point and the principal point of a collimater lens with temperature by setting the ratio of the distance from a coupling position to the light emission point and the distance from the coupling position to the collimator lens principal point to the reciprocal of the ratio of the coefficient of heat expansion of respective holders. CONSTITUTION:When the coefficient of heat expansion of the material of the laser holder 2 is denoted as Ka and the coefficient of heat expansion of the material of a lens barrel 4 is denoted as Kb, a screw 5 is so arranged that A/B=Kb/Ka, where A is the position of the screw 5. Further, A=l/(1-Ka/Kb), where l is the focal distance of the collimator lens 3 which collimates the luminous flux from a semiconductor laser 1 into parallel luminous flux. Namely, the distance A from the light emission point of the semiconductor laser 1 to the screw 5 and the focal distance l of the collimator lens 3 are set as shown above and then the focal distance l can be held invariably constant against temperature variation. Consequently, the high-accuracy parallel luminous flux can be projected without being affected by the temperature variation. |
