Browse Prior Art Database

Low-Profile Optical Storage Head

IP.com Disclosure Number: IPCOM000035995D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR

Abstract

The conventional optical storage head usually uses a 45-degree beam bender before the focusing lens to bend the optical beam 90 degrees to the magneto-optic (MO) disk surface. This limits the profile height of the head to be at least twice the incident beam diameter, D.

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Low-Profile Optical Storage Head

The conventional optical storage head usually uses a 45-degree beam bender before the focusing lens to bend the optical beam 90 degrees to the magneto-optic (MO) disk surface. This limits the profile height of the head to be at least twice the incident beam diameter, D.

In this disclosure, the idea of reducing the head profile height by a factor of two using a modified conventional lens system is dis cussed. Fig. 1 shows a high numerical aperture (0.7) single element lens with a short working distance. One or both surfaces may be aspherical to minimize the aberrations of the lens. With the index of refraction of the lens n = 1.9, the thickness of the numerical aperture (NA) 0.7 lens can be slightly larger than D, where D is the aperture of the lens. The working distance of this lens will be about 0.1D. With this thick lens, a 45-degree mirror can be built inside the lens to bend the beam 90 degrees. The back surface of the lens is now rotated 90 degrees with respect to the input surface, as shown in Fig. 2. Another lens element can be put in front of the lens to correct the aberrations, if needed. This new lens design enables the lens to serve both the bending and focusing functions needed for a low profile optical head. The NA of the bender lens depends on the index of refraction of the glass used for the lens. For an NA larger than 0.7, it may need glass with n >
1.9.

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