| 摘要 |
PROBLEM TO BE SOLVED: To enable simple switching of the number of openings of an optical system and to realize ultrahigh resolution by constituting the space modulation element of a part functioning as a diffraction type lens element and a part functioning as a rotary polarization optical element, and controlling functions of the diffraction type lens element and the rotary polarization optical element by an electrical signal. SOLUTION: When the function of a diffraction type lens element 105 is stopped and the function of the rotary polarization optical system 106 is made valid, since linearly polarized light passing through the optical rotating optical element 106 and linear polarization light passing through the diffraction type lens element 105 intersect orthogonally to each other, ultrahigh resolution is produced. The number of openings for an optical device is decided by a condenser lens 107, read and write of DVD are performed in this state. Next, when a function of the optical rotating optical element 106 is stopped and a function of the diffraction type lens element 105 is made valid, ultrahigh resolution will not be produced. The focal distance of an optical device is made a combined focal distance by the diffraction type optical element 106 and the condenser lens 107, it is assumed that the number of openings is varied as compared with that of the condenser lens 107 only, and reading of a CD is performed in this state. |
