| 摘要 |
<P>PROBLEM TO BE SOLVED: To shorten the optical path length of the whole optical system and to reduce the size and cost of a device in a reproducing or recording optical system of an optical recording medium. <P>SOLUTION: An optical head device 7 is provided with a light emitting source 2 and an optical system 4 including a light-transmissive optical element 3 and irradiates the optical recording medium 5 with light transmitted from the light emitting source 2 through the optical element 3. The optical element 3 has a face or a face group having negative power on the light emitting source side and a face or a face group having positive power on the optical recording medium side. One or more faces are formed as hologram faces in order to increase the power of the face or the face group to form a concentric hologram pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
