Regular Paper

[OPTICAL REVIEW Vol. 21, No. 5 (2014) 668-675]
© 2014 The Japan Society of Applied Physics

Dual Focus Diffractive Optical Element with Extended Depth of Focus

Katsuhiro UNO1* and Isao SHIMIZU2

1Graduate School of Science and Engineering, Faculty of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan
2Research Institute of Advanced Technology (RIAT), Naka, Ibaraki 319-2103, Japan

(Received March 31, 2014; Revised May 23, 2014; Accepted June 13, 2014)

A dual focus property and an extended depth of focus were verified by a new type of diffractive lens displaying on liquid crystal on silicon (LCoS) devices. This type of lens is useful to read information on multilayer optical discs and tilted discs. The radial undulation of the phase groove on the diffractive lens gave the dual focus nature. The focal extension was performed by combining the dual focus lens with the axilens that was invented for expanding the depth of focus. The number of undulations did not affect the intensity along the optical axis but the central spot of the diffraction pattern.

Key words: dual focus lens, extended depth of focus, axilens, daisy lens, lotus lens

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