PROBLEM TO BE SOLVED: To provide a beam splitter having small absorption loss of light, small dependence on incident angle and small separation difference of polarized light is formed, and to provide a composite optical element, an optical pickup device and an optical recording/reproducing device capable of dealing with high-density and high-capacity. ;SOLUTION: A half mirror film 2 consisting of 20 layers 2a to 2t is formed on the face 3a to form a beam splitter film. Among the 1st to 20th layers, 1st, 5th, 11th, 15th and 19th layers 2a, 2e, 2k, 2o, 2s are, for example, TiO2 films having 2.32 refractive index, the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th and 20th layers 2b, 2d, 2f, 2h, 2j, 2l, 2n, 2p, 2r, 2t are, for example, Al2O3 films having 1.63 refractive index, and 3rd, 7th, 9th, 13th and 17th layers 2c, 2g, 2i, 2m, 2q are, for example, SiO2 films having 1.46 refractive index.;COPYRIGHT: (C)2000,JPO
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机译：解决的问题：提供一种分光器，其具有光的吸收损耗小，对入射角的依赖性小以及偏振光的分离差小，并且提供一种复合光学元件，光学拾取装置和光学记录/再现。能够处理高密度和高容量的设备。 ;解决方案：在表面3a上形成由20层2a至2t组成的半反射镜膜2，以形成分束膜。在第1至第20层中，第1，第5，第11，第15和第19层2a，2e，2k，2o，2s例如是具有2.32折射率的TiO 2膜，第2，第4，第6，第8，第10，第12层。 ，第14，第16，第16，第18和第20层2b，2d，2f，2h，2j，2l，2n，2p，2r，2t例如是具有1.63折射率的Al 2 O 3膜，以及第3、7、9、13和17层。层2c，2g，2i，2m，2q例如是折射率为1.46的SiO2膜。;版权：（C）2000，JPO
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