Optical pickup device

Abstract

Abstract PURPOSE:To detect the focus dislocation of an optical beam to the signal surface of a signal recording medium by comparing a signal obtained from a first detecting part and the sum signal of signals respectively obtained from second and third detecting parts. CONSTITUTION:A first detecting part 9 is formed according to one astigmatism direction generated on a detecting surface to detect the focus dislocation of the optical beam. Then, the second and third detecting parts 10 and 11 are parallely provided according to the other astigmatism direction generated on the detecting surface so that the first detecting part 9 can be put between them. When the focus dislocation is generated in one direction of the optical beam, quantity of light to be photodetected by the first detecting part 9 is increased and the quantity of light to be photodetected by the second and third detecting parts 10 and 11 is decreased. When the focus dislocation is generated in the other direction of the optical beam, inversely, the quantity of light to be photodetected by the first detecting part 9 is decreased and the quantity of light to be photodetected by the second and third detecting parts 10 and 11 is increased. Thus, the focus dislocation of the optical beam to the signal surface of the signal recording medium can be detected.

Inventors

• 👤 Ryoichi Kawasaki
• 👤 Tomio Uchida
• 👤 Noriyoshi Oyama
• 👤 Masami Shimizu
• 👤 Kozo Suzuki
• 👤 Chikashi Yoshinaga

Bibliographic Details