Dual-focus forming method and apparatus thereof

摘要

A dual-focus forming method for both a 0.6 mm disk and a 1.2 mm disk, which prevents the increase of wave-front aberration caused by a refractive lens, utilizes a hologram lens having hologram devices respectively formed on the receive and emitting-planes of a transparent plate. The receiving-plane hologram device diffracts incident light from a light source into a zero-order light beam and a 1st-order diffracted light beam, and the emitting-plane hologram device diffracts the zero-order transmitted light beam and 1st-order diffracted light beam into two 1st-order diffracted light beams for being focused onto one or the other disk. The hologram lens exhibits good optical performance due to its low wave-front aberration and is easy to manufacture at low cost.