Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
2000-05-10
2004-06-08
Porta, David (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S216000, C369S044110
Reexamination Certificate
active
06747257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to optically assisted magnetic disk drives. More particularly, the invention relates to the optical detection system used in a optically assisted magnetic disk drive to detect marks on a magnetic disk and thereby precisely located the magnetic read/write head relative to tracks on the disk.
2. Brief Description of the Prior Art
Since the introduction of the personal computer in the 1970s and the development of the floppy disk, the need for greater and greater amounts of storage space has continued unabated. The original floppy disk could store less than 100 kilobytes and the most commonly used (3.5 inch) floppy disk today, introduced in the late 1980s can store 1.4 megabytes. Although fixed (hard) disks now store many gigabytes, there remains a need for removable storage media with high capacity.
High capacity removable storage media became popular in the 1980s with the advent of desktop publishing (DTP). Relatively large, clumsy, and undependable “cartridges” from Syquest, Iomega, and other companies were used to transport large DTP files that could not fit on a floppy disk, to a printing plant. High capacity storage media is still in demand today for transporting large files when a broadband connection is not available and for transporting confidential information without using the public network.
One high capacity removable media system which is growing in popularity is the “a:drive” from OR Technology Inc. of Campbell, Calif. While its outward appearance is almost indistinguishable from that of a 3.5 inch, 1.44 megabyte floppy disk drive, the “a:drive” provides 120 megabytes of storage on ultra high density disks, known as LS-120 media. At the same time, the “a:drive” product is compatible with current and legacy 3.5 inch technology and can read and write to both 720 kilobyte and 1.44 megabyte disks. As its name implies, the “a:drive” can serve as a bootable drive in any system in which it is installed.
The “a:drive” achieves its high capacity and enhanced accuracy and reliability by using an optical positioning system for accurately guiding a magnetic dual-gap head that accommodates the differing track densities of conventional and ultra high density disks without error or mishap. Prior art
FIG. 1
shows a dual media disk storage system for reading data from and writing data to the surface
10
of removable magnetic media
12
having an axis of rotation
14
and a plurality of concentric data tracks
16
. Although the disk drive system is capable of handling dual media, in this instance, for the sake of clarity, only one disk is shown, the well known 3.5 high density type that holds 1.44 megabytes when formatted. A read/write head
18
is guided by an actuator
20
and actuator arm
22
which positions the read/write head
18
over a desired track
16
on the surface
10
of disk
12
. The actuator arm
22
carries a strip having a periodic reflection profile
24
which is used in this instance because the 3.5 disks do not carry any location markings on their surface. In this instance, the periodic reflection profile
24
is a linear encoder. Actuator
20
is under control of a conventional, closed loop servo system
26
which is responsive to a signal from an optical sensor
30
mounted on the underside of sensor housing
28
.
FIG. 2
shows in more detail how a split beam arrangement is used to detect either the reflection profile for a linear encoder when reading/writing 3.5 disks or the markings on the surface of an LS-120 disk when reading/writing it. The sensor system carried on the arm
22
includes, in addition to the light detector
30
, a laser source
32
, a hologram
34
, a lens array
36
and a rooftop mirror
38
. Light from the laser.source
32
is diffracted by the hologram
34
and focused by the lens array
36
. The rooftop mirror directs the light and reflections to either the linear encoder
24
or the surface of an LS-120 disk
40
.
It can be appreciated from prior art
FIG. 2
that the sensor system requires multiple passive optical elements, all of which must be aligned during the assembly process. The alignment requires expensive tooling. Each passive element occupies a finite space and additional space must be provided for the alignment tooling. The sizes of the elements also require a large mechanical supporting structure.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an optical pickup for a data storage device.
It is also an object of the invention to provide an optical pickup for a data storage device that does not require alignment of elements during assembly of the data storage device.
It is another object of the invention to provide an optical pickup for a data storage device that reduces the overall cost of the data storage device.
It is still another object of the invention to provide an optical pickup for a data storage device that is smaller in size than conventional optical pickup systems.
It is also an object of the invention to provide an optical pickup that is a monolithic passive element.
It is another object of the invention to provide an optical pickup in which all optical system elements are fabricated on a single surface of a substrate.
It is still another object of the invention to provide an optical pickup in which each optical element and aperture are tightly controlled relative to each other.
It is also an object of the invention to provide an optical pickup that has a well controlled source distance for image creation and a well controlled image distance for reimaging onto one or more detectors.
It is another object of the invention to provide a monolithic optical pickup borne on a carrier with a laser source and one or more detectors.
In accord with these objects which will be discussed in detail below, the present invention provides a monolithic optical system having all passive optical elements aligned during fabrication, which is done on a wafer level in a batch process, thereby requiring no alignment during system assembly. Its supporting structure is the monolithic passive device itself. A single surface incorporates all the functions of an optical pickup system including a focusing element, image creation apertures and stops, scattering/reflection reduction, and return path optics and apertures.
The focusing element is placed on the monolithic surface to control the image location relative to the source location. Assembly techniques are utilized which tightly control the source location so that a monolithic optical element will repeatedly place the image at a required location. In addition, aberration correction is applied to the focusing element to ensure a precisely focused (diffraction limited) image is achieved in the image plane.
A metalized coating or optical feature to remove transmitted light from the image is lithographically placed about the focusing element. Having the apertures and stops at the principal plane of the focussing element allows for the image size to be precisely controlled by the image distance.
The scattering/reflection reduction is an optical feature that eliminates noise reflecting off the monolithic surface back to the detector plane and into the returning beam path. A monolithic optical element requires each element to be placed close together and a scattering reduction element allows areas that are sensitive to scattering or reflection to be controlled.
The monolithic optical pickup is well suited for use with multiple detector elements. It is necessary to apply apertures to the return path of the monolithic device in order to control cross talk, light designated for one detector that will hit another, and stray light from hitting a detector. The apertures are constructed of a metalization layer or of an optical element to change the direction of the transmitted light. The apertures are placed lithographically and therefore are well controlled in their placement.
Return path optical elements are placed on the monolithic substrate to control the field of view of the de
Cook Kirk
Farnsworth Stephen W.
Fish & Richardson P.C.
Infineon Technologies North America Corp.
Lee Patrick J.
Porta David
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