Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2001-10-29
2003-06-10
Korzuch, William (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112040, C369S112120
Reexamination Certificate
active
06577582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an optical electronic technology. More particularly, the present invention relates to a diffractive stack pickup head for an optical disk drive and a method to fabricate the diffractive stack pickup head.
2. Description of Related Art
Pickup heads are an opto-electronic means by which a signal is written to or read from an optical disk.
FIG. 1
is a system drawing, schematically illustrating a conventional optical disk pickup system. In
FIG. 1
, the generic optical disk pickup system includes a laser diode light source
20
, a beamsplitter
22
, and at least one lens
24
for precisely focusing the light from the laser diode
20
onto an information bearing surface of the optical disk
26
. The system further includes a multi-element photodetector
28
for receiving light that is reflected from the disk
26
, and a servo-generating element
30
, such as the cylindrical lens, which is used to alter the reflected beam from the disk
26
into some form whereby the state of focus and tracking can be easily extracted from the signals generated by the light incident on the multi-element photodetector
28
. This conventional system can be referred to A. B. Marchant, Optical recording, A Technical Overview, Addison-Wesley Publishing, Menlo Park Calif., 1990, p.197. The general mounting arrangement for these optical elements into a pickup head unit is shown in FIG.
2
. In
FIG. 2
, each component is mounted separately, one at a time, into a pickup head housing
32
. The size of the housing
32
is directly related to the image distance of the focusing lens(es)
24
, i.e., the distance from the laser diode
20
to the focused image of the laser diode
20
on the disk
26
of FIG.
1
. With current technology of refractive molded aspheric lenses, this distance is typically in the range of 25-40 mm, and the size of the housing is roughly of the same order. In some designs, the servo-generating element can be an integral part of the beamsplitter
22
and sometimes is implemented using a diffractive or holographic optical element (DOE).
FIG. 3
is a pickup system drawing, schematically illustrating an alternate generic pickup design where the beamsplitter and servo-generating elements are combined into a single DOE and the complete optical system excluding the objective lens is packaged in a small module. In
FIG. 3
, the design of the pickup system
38
has the advantage that most of the opto-electronic components
40
, except the focusing lens/actuator
42
, are assembled in a miniature module. The components
40
are also assembled one at a time to form the miniature module. To complete the pickup system, the components
40
are mounted in a pickup housing similar to the one shown in FIG.
2
. However, the general size of the pickup system
38
is still determined by the imaging distance of the focusing lens. In other words, the holographic module approach has certain advantages but it does not significantly change the size or weight of the complete pickup system.
SUMMARY OF THE INVENTION
The invention provides an optical disk pickup head with the current state-of-the-art technology having an objective that the invention allows many pickups to be made simultaneously in parallel, thereby significantly reducing manufacturing cost.
The invention also includes another objective that the entire pickup, including the focusing lens, can be made in a very small dimension, such as a few millimeters on a side. This allows multiple pickups to be utilized in a single drive.
As embodied and broadly described herein, the invention provides a pickup head used in an optical data storage system. The pickup head includes a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors.
The middle layer's function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate the polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5481386 (1996-01-01), Shimano et al.
patent: 5663944 (1997-09-01), Mun
patent: 5771218 (1998-06-01), Feldman et al.
patent: 5946281 (1999-08-01), Ito et al.
patent: 6272097 (2001-08-01), Nakao et al.
Chu Kim-Kwok
Industrial Technology Institute
J.C. Patents
Korzuch William
LandOfFree
Diffractive stack pickup head for optical disk drives and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diffractive stack pickup head for optical disk drives and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diffractive stack pickup head for optical disk drives and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3093417