| 摘要 |
An optical information recording/reproducing apparatus records information on and/or reproduces information from an optical recording medium and detects a tracking error and a focal error based on a reflected light beam from the optical recording medium. The apparatus includes beam splitter means (75) for splitting the reflected light beam into at least one first beam which is used for detecting the tracking error and at least two second beams which are used for detecting the focal error, and photodetector means (36,56,66) including a first photodetector (36c,56c,66c,66f,66i) which detects the first beam at a position other than an image formation point of the first beam, and second photodetectors (36a,36b,56a,56b,66a,66b,66d,66e,66g,66h) for detecting the second beams approximately at image formation points of the second beams, means for detecting the tracking error according to the push-pull technique based on outputs of the first photodetector (36c,56c,66c,66f,66i), and means for detecting the focal error according to the Foucault technique based on outputs of the second photodetectors (36a,36b,56a,56b,66a,66b,66d,66e,66g,66h). The beam splitter means (75) comprises a hologram optical element which splits the reflected light beam into the first and second beams and deflects at least the second beams to the second photodetectors (36a,36b,56a,56b,66a,66b,66d,66,e,66g,66h), said first beam being a 0th order diffracted light and said second beams being +1st and -1st order diffracted lights. |
