Optical disk storage tray having multiple storage sites and corresponding drive components

An optical disk storage tray having a plurality of storage locations, each of which is supplied with a separate optical head and drive mechanism and with common electronics for controlling the optical heads and drive mechanisms and for interfacing them to a host device.

FIELD OF THE INVENTION 
The present invention relates to the field of information storage and 
retrieval. It relates particularly to a low-cost apparatus for storing 
optical disks and retrieving the data stored on them. 
BACKGROUND OF THE INVENTION 
Optical disks are an increasingly popular medium for digitally storing 
information. Information is stored in binary format, with binary zeros 
represented by non-reflective pits stamped into a plastic disk and binary 
ones represented by reflective high points on the disk. The data is 
retrieved by an optical head which directs a laser source onto the surface 
of the disk and which utilizes a light sensitive photo diode to detect 
light reflecting from the disk surface. The binary information is 
converted to electrical signals and decoded into audio and/or video 
output. 
In present large-scale optical disk storage and retrieval systems each disk 
is installed in a separate cartridge having a separate drive. Each drive 
is comprised of an enclosed casing which includes the disk and all of the 
components, including the interface, loading and unloading mechanics, 
drive mechanics, optical head, and all of electronics which are necessary 
for retrieving the data from the disk and delivering the data to the host 
computer. The drives installed in the storage system are multiplexed to 
the central processing unit. 
These extensive storage systems are highly desirable because of their large 
capacity and because they provide immediate access to data stored on any 
of the installed disks. However, these storage systems require 
considerable amounts of bulky hardware and therefore are extremely costly 
and highly consumptive of space and power. This makes them impractical for 
use in schools, small libraries and other small businesses. 
OBJECT AND SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a storage system for 
optical disks which eliminates much of the costly and duplicative hardware 
found in systems utilizing drive cartridges. 
It is a further object of the present invention to provide a storage system 
for optical storage disks which provides multiple disk storage sites which 
have individual drive mechanics but which share common electronics. 
The present invention comprises a tray having numerous disk storage sites. 
Drive mechanics, particularly a motor spindle and an optical head, are 
positioned at each storage site. Common electronics are provided for 
controlling the operation of the drive mechanisms and for interfacing the 
drive mechanisms to the host computer. The degree to which electronics are 
shared varies between embodiments and depends on the desired cost and 
speed for performance.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is comprised generally of a tray 10, several disk 
storage sites 12, and drive mechanisms 14 positioned at each storage site. 
FIG. 1 is an embodiment of the invention with the disks 16 in place. The 
top face 18 of the tray 10 has a rectangular portion 20 which is recessed 
slightly from the remainder of the top face. The disk storage sites 12 are 
situated in this recessed rectangular portion 20. The tray is preferably 
designed to be a drawer which, as with an audio compact disk player, 
slides in and out of the host device 8 for manual placement and 
replacement of the disks. The disk storage sites 12 may be arranged in a 
variety of ways to accommodate varying numbers of disks. FIG. 3 shows one 
alternative to the disk layout of FIG. 1. 
FIG. 2 shows the first embodiment of the invention with the disks removed 
from the disk locations. Each disk storage site 12 is comprised of a 
circular recess 22 which is sized to accommodate the size of disks (e.g. 
51/4 in.) which are to be stored in the tray. Below each circular recess 
22 is a drive mechanism 14, a detailed top view of which is shown in FIG. 
4. Each drive mechanism is comprised of a motor spindle 24 for rotating 
the disk when the information on the disk is being read, and an optical 
head 26 having a lens 25 which reads the information from the disk. A 
leadscrew 27, which is operated by a motor 23, enables the optical head 26 
to travel radially with respect to the center of the disk in order to 
access information at various locations on the disk. The concept of how to 
design and construct an optical head is well known to one of skill in the 
art of optical storage disk technology and need not be repeated here. 
A perspective view of the motor spindle is shown in FIG. 5. The motor 
spindle is comprised of a turntable 54 having an elevated center portion 
56 which is sized to fit into the center hole of an optical disk (not 
shown). Spring loaded disk clamping balls 58 and disk location fingers 60 
are biased slightly outward from the perimeter 62 of the elevated center 
portion 56 so as to grip the disk by exerting friction on the inside 
perimeter of the hole in the disk. 
The electronic components of the present invention may be configured in a 
variety of ways. The cost of the device as well as the amount of space 
consumed by the electronics will decrease with increased sharing of the 
electronics by the drive mechanisms. However, fewer shared electronics may 
be preferred in order to maintain a higher level of efficiency for the 
device. FIGS. 6 through 9 provide four examples of circuit implementations 
that may be utilized with the present invention. 
FIG. 6 is a schematic representation of an electronics layout utilizing the 
greatest proportion of shared electronics. Each disk storage site 12 has 
separate drive components, including a motor spindle 24, an optical pickup 
26, and a radio frequency amplifier 28. Each of the drive mechanisms is 
interfaced to the remaining electronics, which are shared by all of the 
drive mechanisms. These electronics include the microprocessor 38, a read 
only memory (ROM) or random access memory (RAM) 52 connected to the 
microprocessor, servo control 30, cyclical redundancy checker (CIRC 
decoder) 32, the CD-ROM decoder 34 which is interfaced to the host 
computer, a random access memory (RAM) 50 which is connected to the CD-ROM 
decoder 34, and the audio amplifier 36 which is only necessary in systems 
where disks having audio tracks are installed. 
Because a single servo control device 30 is used to control each of the 
drive mechanisms, a latch device 40 is provided to detect the logic 
signals from the microprocessor 38 which indicate which drive mechanism 
should be turned on. A demultiplexer 42 is provided to interpret those 
signals and to direct the power signal from the servo control 30 to the 
selected drive. Similarly, a second latch 44 and a multiplexer 46 direct 
the output data from the selected drive to the decoders 32, 34. 
The embodiment of FIG. 7, is similar to the FIG. 5 embodiment except that a 
separate servo control device 30a is provided for each drive mechanism. 
Logic lines passing from the microprocessor 38 to a decoder 48 indicate 
which servo control device is to be activated, and the decoder 48 delivers 
the activation signal to the indicated device. 
In addition to having a separate servo control device 30b, the embodiment 
of FIG. 8 provides a separate CIRC decoder 32b and a separate audio 
amplifier 36b for each drive mechanism. The non-audio component of the 
output from the CIRC decoder is multiplexed 46b to the CD-ROM decoder 34. 
FIG. 9 shows an embodiment which provides the greatest degree of efficiency 
but which is the most costly and least compact of the embodiments 
described above. A separate CD-ROM decoder 34c is additionally provided 
for each drive and is separately interfaced to the host computer. In this 
embodiment the drives share only the microprocessor device 38. 
While varying disk layouts and electronic configurations have been 
described, many others are possible according to the present invention. 
The scope of the present invention is not limited to the specific 
embodiments described above but is rather defined by the claims recited 
below.