Multiple focus lens, an optical head apparatus and an optical in

Details Multiple focus lens, an optical head apparatus and an optical in Multiple focus lens, an optical head apparatus and an optical in

1996-08-12

1999-11-16

Henry, Jon W.

Optical: systems and elements

Holographic system or element

Using a hologram as an optical element

359 16, 359566, 359570, 365216, G02B 532

Patent

active

059867795

ABSTRACT:
Coma of an objective lens occurs depending on the lens-forming condition when plural disks of different substrate thickness are recorded and reproduced. An objective lens according to this invention is not influenced by the coma even if the thickness of the substrates is changed. For this purpose, a diffraction grating whose aberration is corrected is formed on the first side of an aspheric objective lens. Due to this correction, light beams having different diffraction orders, e.g. 0th order diffracted light and +1st order diffracted light, are focused respectively on two kinds of substrates of different thickness. The whole objective lens is tilted to correct its axial coma, and the tilt angle is predetermined to be substantially identical with respect to plural substrates which are different in thickness.

REFERENCES:
patent: 5161040 (1992-11-01), Yokoyama et al.
patent: 5349471 (1994-09-01), Morris et al.
patent: 5446565 (1995-08-01), Komma et al.
patent: 5473471 (1995-12-01), Yamagata et al.
Optical Review, vol. 1, No. 1 (1994):27-29, "Dual Focus Optical Head for 0.6 mm and 1.2 mm Disks," Yoshiaki Komma, Seiji Nishino and Sadao Mizuno.

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