| 摘要 |
PURPOSE: An optical pick-up unit is provided to employ a photo-detector having an eight-division pattern while using a two-wavelength light source module to reduce the price of the optical pick-up unit. CONSTITUTION: An optical pick-up unit includes a single two-wavelength light source module(1) for selectively projecting light beams having different wavelengths, a prism(3) for reflecting and transmitting the light beams, and a polarization converter(4) for converting linearly polarized beams reflected and transmitted through the prism into circular-polarized beams. The optical pick-up unit further includes an object lens(5) for focusing the circular-polarized beams on one point on an optical disc(6), a sensor lens(7) for generating astigmatism for detecting a focus error when a light beam that collides with a signal track of the optical disc to be reflected is transmitted, a photo-detector(20) having an eight-division pattern for detecting the light beam transmitted through sensor lens to convert the beam into an electric signal, and a hologram(10) for refracting two beams having different light paths to focus the beams on one point of the photo-detector. |
