位相補正素子を用いた超解像によるスポット形状の微小化

概要

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When using semiconductor lasers to detect extremely small objects, smaller laser beam spots allow higher resolution. For example, the optical head for optical disk generates an extremely small spot of light to detect an extremely small pit that represents data on the optical disk, thus realizing high storage capacity. The spot size is determined by the wavelength of the laser and the numerical aperture (NA) of the objective lens. So it cannot be below the diffraction limit. There is, however, a method of increasing the resolution of an ideal optical system by varying the state of the laser light that enters the objective lens. This is a kind of super-resolution. That method, however, generates side-lobes, which are a characteristic of super-resolution. In this paper we propose the super-resolution spot shape suitable for data reading from an optical disk. We used a phase correction element to get the super-resolution spot. With practicality as a priority, we simplified the element structure to the fullest extent. We confirmed effective data reading from an optical disk using this phase correction element.
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