| 摘要 |
PROBLEM TO BE SOLVED: To provide an information recording/reproducing device capable of controlling an exit light quantity from a light source with high precision by reflecting an eclipse of a luminous flux in an object lens. SOLUTION: The information recording/reproducing device, which performs recording/reproducing of information by condensing the luminous flux 10 from the light source 11 onto a recording medium 1 having a plurality of recording layers 2 by the object lens 17 via a collimator(Co) lens 14 movable in the direction of the optical axis, is provided with a beam splitter(BS) 15 which guides a transmitted luminous flux or a reflected luminous flux to the object lens 17 by transmitting and reflecting the luminous flux 10 from the Co lens 14, an optical device 19 which amplifies a change in parallelism of the luminous flux and exits the flux by entering the reflected luminous flux or the transmitted luminous flux from the BS 15, and a photodetector 20 having a light receiving area which receives the central part and the peripheral part of the exit luminous flux from the optical device 19. The exit light quantity from the optical source 11 is controlled and also the position of the Co lens 14 in the direction of the optical axis is controlled based on an output of the photodetector 20. |
