| 摘要 |
PURPOSE:To obtain an optical head with superior stability for temperature by setting the center point of a line segment connecting a first focusing point and a second focusing point on an optical detector, the light emitting point of a semiconductor laser, and the center of a reflection type hologram optical device so as to be aligned on the same plane. CONSTITUTION:The midpoint (xf, yf, zf) of the line segment connecting a first convergent point 16(x1f, y1f, z1f) to a second convergent point 17(x2f, y2f, z2f) on the optical detector 22, the light emitting point 18(xg, yg, zg) of the semiconductor laser 1, and the center (origin of coordinate 19) of the reflection type hologram optical device 27 are arranged so as to be positioned on the same plane (reference plane 20) judging from a packaging point of view. Also, the focal power of the reflection type hologram optical device 27 is removed as far as possible, and distance d1f, d2f, and dg from the origin 19 shown in equation I are set as d1f=d2f=dg to suppress the occurrence of aberration in a vertical direction due to the fluctuation of wavelength. In such a way, it is possible to obtain an optical head device having stable error detecting characteristics against the fluctuation of the wavelength of a light source. |
