| 摘要 |
PURPOSE:To erase variation in a triangle prism outgoing direction and a detecting error in a focus position detecting system and a track position detecting system at the time of changing an environmental temperature and to improve reliability by specifying the material of a triangle prism to convert the light flux shape of an outgoing light from a semiconductor laser with the refraction of light. CONSTITUTION:A triangle prism 3 is provided to convert the light flux shape of the outgoing light from a semiconductor laser 1 by the refraction of the light and the material of this triangle prism 3 is obtained to satisfy the condition of an expression I. In the expression I, a deltan/deltalambda is the wavelength dispersion of the triangle prism refracting rate and a deltalambda/deltaT is the temperature coefficient of a semiconductor laser oscillating wavelength. Thus, to the change of the environmental temperature, the fluctuation of the refracting rate in the material of the triangle prism is erased and the change of the direction of the triangle prism outgoing light is not generated. Then, the detecting error is not generated in focus error detection and track position detection and the device of the high reliability can be obtained. |
