FOCUS SIGNAL GENERATION APPARATUS AND FOCUS SIGNAL GENERATION METHOD

• Main Authors: NAKAHARA HIROISA, TAKESHITA NOBUO, TAKUSHIMA SHU, KONO HIROYUKI, SEKI MAKITO, KISHIGAMI SATOSHI
• Format: Patent
• Language: English; Japanese
• Published: 22.06.2015
• Subjects: INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; PHYSICS

PROBLEM TO BE SOLVED: To provide a focus signal generation apparatus and a focus signal generation method which suppress an influence of diffraction light when a detection range for obtaining a focus signal is reduced.SOLUTION: A focus signal generation apparatus 100 comprises: a laser source 101 emitting a laser beam; an object lens 105 focusing the laser beam onto an object 106; a separation element 108 separating, into two laser beams, a laser beam 102 reflected on the object 106 and transmitting through the object lens 105; a first light receiving element 110 and a second light receiving element 112 receiving the two laser beams and converting the beams into electric signals, respectively; astigmatism application means 109, 111 applying astigmatism to at least one of the laser beams entering the light receiving elements 110, 112; an aberration correction element 107 correcting aberration generated in an optical path from the object lens 105 to the first light receiving element 110 and to the second light receiving element 112; and focus signal generation means 113 generating a focus signal based on outputs of the light receiving elements 110, 112. 【課題】焦点信号が得られる検出範囲を狭くした場合に、回折光の影響を抑制することが難しいという問題があった。【解決手段】焦点信号生成装置１００は、レーザ光を出射するレーザ光源１０１と、レーザ光を対象物１０６に集光する対物レンズ１０５と、対象物１０６で反射されて対物レンズ１０５を透過したレーザ光１０２を２つのレーザ光に分離する分離素子１０８と、当該２つのレーザ光をそれぞれ受光して電気信号に変換する第１の受光素子１１０および第２の受光素子１１２と、受光素子１１０，１１２に入射するレーザ光のうち、少なくとも一方に非点収差を付与する非点収差付与手段１０９，１１１と、対物レンズ１０５から第１の受光素子１１０および第２の受光素子１１２までの光路で生じる収差を補正する収差補正素子１０７と、受光素子１１０，１１２の出力に基づいて焦点信号を生成する焦点信号生成手段１１３とを備える。【選択図】図１