Patent ID: 8254236

Claim:
An optical information reproducing apparatus comprising: a laser source; a first optical divider configured to divide a light beam emitted from the laser source; a condensing optical system configured to focus on an optical information recording medium one of light beams divided at the first optical divider, the light beam being emitted from the laser source; a variable focusing mechanism configured to cause a focus position of the light beam to be variable, the light beam being focused by the condensing optical system; an interference optical system configured to cause signal light and reference light to optically interfere with each other, the signal light being focused on and reflected off the optical information recording medium, the reference light being obtained from the other of the divided light beams; a splitting optical system configured to divide a coherent light beam at the interference optical system into a plurality of coherent light beams; a plurality of detectors configured to individually detect the plurality of coherent light beams divided at the splitting optical system in a state in which phase relations are different from each other; and a second optical divider configured to separate the plurality of coherent light beams into a first light bundle near an optical axis and a second light bundle in an edge portion and diverge the first and second light bundles so that the first and second light bundles are focused on the plurality of detectors, wherein: a focus error signal is detected for the first light bundle; and the focus error signal is used to control the variable focusing mechanism.