Abstract:
The present invention improves the conventional information reproduction practice by providing a high-performance optical information processing apparatus having various hardwares for arriving at multitasking capability as well as means for achieving disc-loading and -unloading flexibility, thereby allowing a user to launch a software program or simultaneously several software programs directly from an optical disc and/or several optical discs stored therein, eliminating tedious and time-consuming software installation, affording a kind of copy-right protection to softwares, and alleviating the burden of a hard-disk drive during the process of information reproducing.  
                       References Cited     U.S. PATENT DOCUMENTS                                           5,375,113   December 1994   Pollard et al.   369/30         5,335,218   August 1994   Osada   369/178         5,253,235   October 1993   Isobe et al.   369/37         5,251,192   October 1993   Liu   369/36         5,193,079   March 1993   Ko et al.   369/37         5,189,652   February 1993   Inoue   369/36         5,146,451   September 1992   Kang   369/178         5,119,354   June 1992   Umesaki   369/36         5,043,963   August 1991   Iwamoto   369/36         4,888,751   December 1989   Yoshimaru et al.   369/36         4,722,078   January 1988   Nakanishi et al.   369/39         4,644,515   February 1987   Allebest et al.   369/32

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to the field of information processing utilizing optical discs and particularly to a high-efficient optical-disc-type apparatus used in connection with a host computer that provides disc-loading and -unloading flexibility a user and allows the host computer to effectively and/or multitaskingly perform various information processing actions directly from optical discs so as to alleviate the heavy burden of a hard-disk drive in the process of information reproducing.  
         BACKGROUND OF THE INVENTION  
         [0002]    An optical disc or compact disc (CD) is made from a transparent plastic material with a thickness of about 1.2 mm that contains a protected thin metal film wherein pits (or depressions) are formed. The pits have light reflectivities different from the light reflectivity of nonpitted portions of the metal film, thus forming a series of 0s and 1s for digital storing of data. In production, a master disc is first developed from a glass disc coated with a uniform layer of photoresist material that is subjected to a series of exposure to a high-power energy beam or laser for forming various pits via the technology of photolithography. The master disc is then used to develop a nickel mother for use in stamping out multiple copies of the discs in transparent plastic material. Each of these is then coated with a thin metallic reflecting layer and then with a protective polymer coating on top of that. When reproducing the stored information, a low-power laser is used to sense the presence or absence of pits. Because a laser beam can be so focused, adjacent tracks of the spiral of pits need be no larger than 1.6±m. As a result, one side of a typical 120-mm (4.72-in) CD can have 20,000 tracks for holding a minimum of 500 megabytes of data which can easily store the text of a 20-volume encyclopedia, while both surfaces of a typical 133-mm (5.25-in) or a 89-mm (3.5-in) floppy disk are able to respectively hold only 1.2 or 1.44 megabytes.  
           [0003]    Owing to the nature of their high storage capacity, optical discs are especially suitable for storing information requiring or taking large storage spaces, such as patent information, video data, and digital audio files. In addition to the floppy-disk version, software developers have recently produced the 120-mm read-only-memory CD (CD-ROM) version of executable softwares or programs, such as IBM® OS/2 and Microsoft Windows® 95 for use in personal information processing apparatuses, such as desktop- or notebook-type computers.  
           [0004]    Even though becoming increasingly popularly equipped in computers, a CD-ROM drive plays a much less significant role in information processing when compared with a hard-disk drive that utilizes the magnetic recording technology. This is because the currently available computers are designed to execute a program or software basically through reproducing the information stored on hard-disk drives, especially when the size of a program exceeds the storage capacity of a floppy disk. When sold to an end user, a software for use in applications such as disk controlling, word processing, spread sheet, drawing, and presentation making, is compressedly stored on a plurality of floppy disks or an optical disc. Regardless of being either stored in floppy disks or an optical disc, a purchased software needs to go through a tedious software installation process through which all program files are decompressedly copied to a hard-disk drive wherefrom the software is then executed. In accordance with this conventional practice, the storage space of a hard-disk drive is quickly filled up. This not only incurs indirect cost in the expenditure of the hard-disk drive in addition to the purchased price of a software to the end user, but eventually slows down the read-and-write operation efficiency of the hard-disk drive because any data files created are constantly rewritten, fragmentally relocated, and eventually scattered all over the hard-disk drive. Accordingly, a longer time is needed to find all of the data of a particular file. The only remedy currently available for this problem is to routinely run a hard-disk maintenance process in order to remove file fragmentation. Unfortunately, as more softwares or data files are stored on a hard-disk drive, the hard-disk maintenance process becomes more and more time-consuming, because it also involves relocation of the program files that occupy most of the space of the hard-disk drive but are never changed or altered throughout the entire life of their usage. Still there is another concern that a hard-disk drive is subject to nonphysical damages, for instance, such as program files being truncated or cross-linked due to improper assessing or writing during information reproducing or being infected by computer virus. As a result, a software program becomes corrupted; and, another tedious software installation process is again needed. All of these point to the fact that the currently available computers are designed to proceed information processing from reproducing the information stored on hard-disk drives; and, this is not necessarily desirable.  
           [0005]    Since a software is mostly stored on a plurality of floppy disks for its distribution, an end user is routinely advised to make a set of backup copies because floppy disks are susceptible to physical and external damages. Inevitable is to incur another disadvantage: a time-consuming process for making backup copies.  
           [0006]    The need to install a purchased software to a hard-disk drive further incurs another problem: it is extremely difficult for software developers to stop or prevent illegal-copying of a software. There are existing hardware-type protection devices and password-type protection approaches; but they are affordable only for high-price software programs with an aim of selling at most a few thousand copies for use in trading stocks or futures in real time, for instance. In contrast, volume softwares are sold in sealed envelopes. Once a sealed envelope is opened, an end user is assumed to accept the software license agreement set by a software developer; and, the software is not returnable. Unfortunately, there is no practical way to prevent an end user from illegally coping such a software. As with the software developers producing high-volume and low-price softwares suffer from their products being illegally copied, the consumers lose their opportunity to try out a software program before purchasing.  
           [0007]    In view of the disadvantages and problems mentioned hereinbefore, it is clear that currently available computers and optical disc or floppy-disk apparatuses are not designed to achieve their optimal potential. Owing to the nature of durability and storage capacity far superior to that of a floppy disk, an optical disc has a greater potential to become a memory storage medium for constructing a special type of apparatus to remedy the disadvantages currently encountered in the available information processing apparatuses. Thus, the main interest of the present invention is to design a high-efficient optical disc apparatus wherefrom software programs can be directly launched so as to eliminate the tedious, time-consuming software installation and thus to offer an alternative of copy-right protection to software developers, as well as to alleviate the heavy burden of a hard-disk drive in information processing. Also essential for an information processing apparatus of this type of the present invention is the feature of disc-loading and -unloading flexibility that allows a user to easily change or replace desired discs at will. In order to achieve the highest efficiency in information reproduction, furthermore, any disc and thus disc track should be readily accessible by at least one optical unit at any time. An optical read head should be able to travel from a disc to another, and its travelling should be limited to one-directional movement (either linear or circular) because multiple-directional or three-dimensional movement will greatly slows down optical-read-head travelling efficiency. It is also highly desirable that an information processing apparatus of this type in accordance with the present invention comprises multiple disc sites each able to detachably hold a disc so that various software programs are readily available because Microsoft®, WordPerfect®, or Lotus® are most likely to produce their own software discs.  
           [0008]    Multitasking or multiprocessing is another highly desirable feature for an information processing apparatus of this type in accordance with the interest of the present invention. In the context of the present invention, multitasking or multiprocessing is defined to refer to separate hardware control units that allow execution of separate or several software programs simultaneously. Because of containing a plurality of discs wherefrom several programs can be directly launched, an information processing apparatus of this type needs a safeguard device to prevent the discs stored therein from being unauthorizedly removed. Further, this type of information processing apparatus should be compact enough to be internally installed in a computer, because with the trend towards miniaturization, no future computers would be spacious enough for internally storing a bulky CD apparatus holding more than two horizontally spaced 120-mm discs.  
           [0009]    An information processing apparatus of this type with all or a selected combination of the features mentioned hereinbefore in the present invention is not yet readily taught by the prior arts. This is discussed as follows.  
           [0010]    U.S. Pat. No. 4,644,515 describes a laser-disc digital data video storage system in which multiple discs stacked upon a common rotatable drive shaft are to be read by a plurality of stationary read head arrays for commercial use. This jukebox-like system allows multiple users to access its information by employing a huge number of read heads, for example 55,000 heads (or one head for each track), in each read head array. One of the main disadvantages of this type of system is its lacking disc-loading and -unloading flexibility; that is that a user is impossible to access the common drive shaft for changing or replacing a desired disc at will. U.S. Pat. No. 4,888,751 describes an image information processing system in which (at least) an optical unit having an optical head arm rotatable through 180 degrees is used to scan the information stored on either adjacent side of multiple discs that are stacked at predetermined intervals on a detachable mounting mechanism. The detachable mounting mechanism provides some improvement in disc-loading and disc-unloading flexibility over U.S. Pat. No. 4,644,515 mentioned above, but is still inconvenient for a user to replace or change a desired disc at will due to the stacking nature of its disc arrangement. This prior apparatus is afforded with a plurality of optical units such that one of the optical units is most likely readily available for vertically moving to a next selected disc. In such a manner, the process of accessing information recorded on a different disc is speeded up; otherwise, the access time will unacceptably slow since an optical unit in such a system has first to retract out of a disc space by swinging, to move vertically to a new disc space to be entered, and then to seek a new track by swinging. In this prior art, it is obvious that the presence of the multiple optical units is intended for speeding up disc-track access time between discs, but not for arising any multitasking.  
           [0011]    To improve the access time for reproducing the information stored on different discs, U.S. Pat. No. 5,189,652 describes a stationary-type optical disc apparatus that is characterized by comprising a plurality of optical units each slidable into a disc space to access a predetermined position of a disc. Although it reduces the access time, this system neither affords disc-loading and -unloading flexibility referred to above because of its stationary and disc-stacking natures, nor provides any multitasking capability.  
           [0012]    Instead of using the approach of stacking as used in the abovementioned prior arts, U.S. Pat. No. 4,722,078 employs a plurality of horizontally spaced disc compartments (or trays) each holding an audio disc, upon selected, which can be scanned by a disc playback module that is capable of being horizontally transported between the disc compartments. Because each disc compartment has a separate means for independently extending and retracting out of and into the apparatus, this audio CD player requires multiple front entrances. In other words, this configuration is too bulky and cannot be internally installed into the existing slots of the current computers, which typically have dimensions of 146-mm (5.75-in) in width, 41-mm (1.75-in) in height, and up to about 254-mm (10-in) in depth. In addition, it lacks multitasking capability.  
           [0013]    Other examples using the nonstacking approach are embodied in U.S. Pat. Nos. 5,146,451, 5,193,079, and 5,251,192. However, in accordance with these prior arts, discs are not readily accessible at any time because their disc-storage sites need to move a predetermined position before a selected disc becomes accessible, thus slowing down information-reproduction efficiency. Similar inefficiency is also seen in U.S. Pat. Nos. 5,119,354 and 5,335,218 that utilize a disc transfer means comprising a drive roller to deliver a disc selected from a disc container or magazine (having a plurality of discs in a pile therein) to a disc drive for rotating and thus reading. Although improving disc-loading and -unloading flexibility referred to above, all of these prior apparatuses with capability of holding a plurality of discs require several additional transitional stages before a selected disc becomes accessible to a singular optical unit. These apparatuses are best for use in as-intended audio applications, not for use in information processing that requires high-efficient, high-speed information reproduction.  
           [0014]    Providing disc-loading and -unloading flexibility to some extent, U.S. Pat. No. 5,043,963 designs an information processing apparatus capable of playing a disc selected either from a plurality of sizes such as 80-, 120-, 200- or 300-mm in diameter. These multisized discs are laid on a tray wherein a circular-like section used to store a plurality of small-sized discs is rotatable for their selection. Different versions of apparatuses capable of playing optical discs with different diameters are seen in U.S. Pat. Nos. 5,119,354 and 5,253,235. The ability of playing the discs with different diameters is desirable, however, the discs in these prior apparatuses fail to be readily accessible by their single optical unit at any time.  
           [0015]    In the conventional CD apparatuses, a single clamp device (or press member) capable of pivoting downwardly or upwardly is often used to pinch a disc mounted to a drive shaft or turntable for rotating. Clamp devices of this type are embodied in U.S. Pat. Nos. 4,722,078, 5,146,451, 5,251,192, and 5,253,235. Those are not suitable for use when a plurality of discs need to be in a readily-accessible state at any time. U.S. Pat. No. 5,375,113 describes a simple clamping mechanism for each of turntables, which is desirable. However, it remains to be seen whether the clamping mechanism can provide necessary clamping force and at the same time can afford an easy release of a loaded disc. Accordingly, there is a need to design a simple, yet effective and space-saving disc-clamping device with disc-loading and -unloading flexibility for use in the information processing apparatus in accordance with the interest of the present invention.  
           [0016]    In order to simultaneously launch several software programs directly from either an optical disc or multiple optical discs in accordance with the interest of the present invention, the hardware of an information processing apparatus must be rendered to possess multitasking capability. This requires not only having a plurality of optical units but also a variety of signal process means (such as decoders), control means (including a plurality of microprocessors or a microprocessor with multitasking capability) and data transmitting means that all coordinately work together for arriving at reproducing a plural sets of data simultaneously from various disc tracks on a disc or on several discs and at the same time transmitting them to a host computer. Otherwise, neither optical units can be instructed to independently and simultaneously move to a plurality of predetermined disc tracks, nor a plural sets of data retrieved from discs can be simultaneously processed for returning back to their original state and then transmitted to a host computer. Thus, equipping with plural discs and optical units will make an information processing apparatus more efficiency in information access time, but will not necessarily arrive at any multitasking nature needed for future high-speed information processing. One of the instances is exemplified in U.S. Pat. No. 5,375,113 describing an apparatus that has a plurality of disc storage sites (in nonstacking from), each having a separate drive means and an optical disc situated together, for reading data specifically from one single, selected optical disc. The main object of the prior art is to eliminate much of the costly and duplicative hardware found in systems utilizing drive cartridges so that common control means such as latches, demultiplexers, and multiplexers are used in order to fulfill its main object for delivering a power signal to a selected single disc storage site for activating its drive means to read information from its respective disc. Even though various electronic configurations are given, the prior art utilizes only one single microprocessor for instructing which drive means should be turned on or which servo control device should be activated. Under the circumstances, it is not possible to simultaneously issue multiple commands or control signals to activate and thus to control a plurality of drive means for performing information reproduction from plural discs at the same time. In essence, the prior apparatus is specifically designed for information reproduction to take place one at a time in a selected disc storage site; thus, it inherits no multitasking nature to be claimed in the present invention. This is further substantiates in the fact that throughout the entire context, this prior art neither mentions nor even suggests retrieving information simultaneously from plural discs and sending a plural sets of retrieved information at the same time to its host computer, which are all essential for multitasking to take place.  
           [0017]    It is now becoming clear that each of the current CD apparatuses has its own merit but all suffer from various types of disadvantages, such as unable to launch programs directly from optical discs, lack of multitasking capability, unable for all discs and thus disc tracks to maintain in a readily accessible state to at least one optical unit at any time, lack of disc-loading and -unloading flexibility, lack of flexibility for optical units to travel between discs, lack of an efficient means for an optical read head to selectively travel between discs, too bulky to be installed in a host computer, and/or lack of a device to safeguard optical discs from being unauthorizedly removed.  
         OBJECTS OF THE INVENTION  
         [0018]    A primary object of the present invention is to provide an information processing apparatus with multitasking-capability hardwares so that a plurality of optical units are capable of independently and simultaneously moving to a plurality of disc tracks or locations, thus it is possible to launch a or several software programs directly from the information processing apparatus, to provide true multitasking capability, to eliminate tedious and time-consuming software installation, to offer a kind of copy-right protection, and to alleviate the burden of a hard-disk drive in information reproduction processing.  
           [0019]    Another object of the present invention is to provide an information processing apparatus with turntables having disc-loading and -unloading flexibility, wherein each of turntables comprises a disc-holding and -releasing means with self-clamping and self-releasing feature for each optical disc.  
           [0020]    Another object of the present invention is to provide an information processing apparatus with turntables and optical units being arranged in a particular manner, wherein each optical unit comprises an efficient driving means for moving at least one optical read head selectively between discs so that several optical read heads are able to independently move to a plurality of predetermined disc tracks on the same disc surface of a selected optical disc for simultaneously retrieving a plurality of information stored thereon.  
           [0021]    Another object of the present invention is to provide an information processing apparatus with turntables and optical units being arranged in a particular manner so that the same driving mechanism is used to move the optical read head of each of said optical units selectively between disc tracks and between discs, greatly improving information access efficiency when an optical unit needs to move between discs.  
           [0022]    Another object of the present invention is to provide an information processing apparatus with a variety of control means (including a plurality of microprocessors or a microprocessor with multitasking capability) so that at least two of optical units are able to work coordinately and simultaneously on separate portions of a software program, greatly improving efficiency in information reproduction.  
           [0023]    Another object of the present invention is to afford an information processing apparatus with a security means to safeguard the optical discs stored therein from being unauthorizedly removed.  
           [0024]    Another object of the present invention is to provide an information processing apparatus with a plurality of disc compartments so that it is possible to replace an optical disc in one disc compartment while the other optical discs stored in another disc compartment remain operating.  
           [0025]    Another object of the present invention is to provide an information processing apparatus with a control means to allow a disc to be scanned either at a constant angular velocity (CAV) method or at a constant linear velocity (CLV) method.  
           [0026]    Another object of the present invention is to provide an information processing apparatus with at least one turntable that can accommodate an optical disc with different disc diameters, affording greater application flexibility.  
         SUMMARY OF THE INVENTION  
         [0027]    The present invention improves the conventional information reproduction practice by providing an optical information processing apparatus with multitasking-capability hardwares and disc-loading and -unloading flexibility means, thereby allowing a user to launch a software program or simultaneously a plurality of software programs directly from an optical disc or several optical discs stored therein. The multitasking-capability hardwares of the present invention comprise a plurality of turntables, optical units, control means, signal-process means, and data transmitting means to coordinately work together for multitaskingly retrieving, controlling and transmitting a plurality of information simultaneously from various tracks of a disc or several discs to a host computer. Turntables and optical units are arranged and rendered in a particular manner such that at least one optical unit can access any tracks of at least two discs, a plurality of optical read heads situated in said optical units can independently and simultaneously access a plurality of tracks of on the same surface of a disc for high-speed information processing, and/or a plurality of tracks of separate disc surfaces for multitaskingly perform several programs at the same time. In accordance with the present invention, the number of optical units can be less as compared with that of turntables, for reducing the production costs of making an optical information processing apparatus while maintaining high efficiency in information reproduction.  
           [0028]    An optical information processing apparatus of this type is optionally equipped with a plurality of disc compartments so that one disc compartment can be independently open for disc exchanging while the other disc compartment remains closed and active programs remain in operating, with a disc holding means having self-clamping and self-releasing feature to facilitate disc-loading and -unloading operation, with at least one turntable capable of accommodating a disc with various disc diameters, with a control means to allow a disc to be scanned either at a constant angular velocity (CAV) method or at a constant linear velocity (CLV) method, and/or a safeguard mechanism. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a perspective view of a multitasking information processing apparatus in accordance with the present invention having two optical units capable of being used to reproduce information simultaneously from two different tracks of an optical disc.  
         [0030]    [0030]FIG. 2 is a cutaway side view taken along the line A-A of FIG. 1, schematically showing an arrangement of the multitasking information processing apparatus.  
         [0031]    [0031]FIG. 3 is a perspective, partial-cutaway view of a multitasking information processing apparatus of the present invention showing a plurality of multisized discs set in two disc compartments and a disc-compartment transporting means for the front disc compartment to be able to separately drawn out and into the playhousing.  
         [0032]    [0032]FIG. 4 is a cutaway view of the underside of the subchassis traverse driving mechanism taken along the line B-B in FIG. 3 of the present invention.  
         [0033]    [0033]FIG. 5 is an exploded perspective view of the disc-compartment transporting means seen in FIG. 3 of the present invention.  
         [0034]    [0034]FIG. 6 is an illustrative top plane view of the multitasking information processing apparatus seen in FIG. 3 therein horizontally disposed with six optical units and eight optical discs.  
         [0035]    [0035]FIG. 7 is a block diagram of a control system of the multitasking information processing apparatus shown in FIG. 6 of the present invention.  
         [0036]    [0036]FIG. 8 is an alternative configuration of turntables and optical units.  
         [0037]    [0037]FIGS. 9A and 9B are perspective top and cutaway side views respectively for the turntable having a disc-holding and -releasing means with self-clamping and self-releasing feature in accordance with the present invention.  
         [0038]    [0038]FIG. 10 is a perspective top view of an optical unit as used in FIG. 6 that is able to access different tracks of three discs through horizontally swinging in accordance with the present invention.  
         [0039]    [0039]FIG. 11 is a cutaway view of an optical unit with an optical read head and a driving mechanism, and a turntable with a disc-holding and -releasing means.  
         [0040]    [0040]FIG. 12 is an illustrative, cutaway side view of an optical read head.  
         [0041]    [0041]FIG. 13 is an illustrative top view of an optical unit of the present invention comprising a driving means in a cutaway top view that enables an optical read head not only to position at a selected track on a disc but also to travel between three discs.  
         [0042]    [0042]FIG. 14 is an illustrative top view of a single optical unit in accordance with the present invention, having a driving means for at least one optical read head situated therein to travel to at least one predetermined track selectively between a plurality of discs for retrieving information stored thereon.  
         [0043]    [0043]FIG. 15 is a cutaway view of an optical unit comprising an upper optical read head and a lower optical read head for simultaneously reproducing information stored on both surfaces of a disc. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0044]    Referring now to FIGS. 1 and 2, one embodiment of the present invention will be described in detail hereinbelow.  
         [0045]    [0045]FIG. 1 is a perspective view of an information processing apparatus with multitasking capability in accordance with the present invention, having two optical units and one optical disc in a loaded condition. Apparatus  1  has a structural frame  2  on which various mechanism components are mounted. The frame also serves for the apparatus to be either internally installed as a built-in unit in a computer or covered by a housing for use as a stand-alone unit to be connected to a computer. Provided with apparatus  1  is a front panel  3  having a disc-releasing button  4  and a disc supplying slot  5  on which there exists a larger opening  6 . Disc supplying slot  5  is in a size just allowing an optical disc to be inserted into or extracted out of the apparatus. Larger opening  6  is provided to allow a user&lt;&lt;s finger to push a disc, being inserted through first guide roller pairs  7  and  8  and then second guide roller pairs  9  and  10 , further toward the inside of the apparatus by moving a disc levelling mechanism  11  backward. Disc levelling mechanism  11  has a flat area  12  that is in a horizontal position slightly lower than the disc-setting table  29  (seen in FIG. 2) of turntable (or spindle)  13  so that a disc is prevented from being tipped over and thus is disposed onto disc-setting table  29  during loading. Disc levelling mechanism  11  is slideable along a pair of horizontally disposed guide rails  14  through a pair of bearings  15 . When pushed backward to a predetermined position, disc levelling mechanism  11  moves the rear-end portion  16  of disc clamp arm  17  backward so that disc clamp head  18  at the distal end of clamp arm  17  is pivoted downward about a fulcrum  19  by compressing springs  20  mounted on the rear portion of guide rails  14  so that a rod  21  connecting disc levelling mechanism  11  to a mechanical holding mechanism  22  is pulled backward. When pulled to a predetermined position, the top portion of position holder  23  of mechanical holding mechanism  22  is pivoted backward about a fulcrum  24  so as to move the middle portion of position holder  23  over a spring strip  25 . The spring strip is arranged to have one end fixed to a support plate  26  and the other end being free, thus allowing the move-over action of position holder  23  to take place whenever there is an external force sufficient to overcome the holding force of spring strip  25 . Position holder  23  is being held by spring strip  25  against the force of compressed springs  20  and disc levelling mechanism  11  is thus not touching the edge of disc  27 .  
         [0046]    During disc loading, disc levelling mechanism  11  is moved backward to a predetermined position so that a microswitch (not shown) activates a solenoid  28  to pivot disc clamp head  18  downward further so as to tightly grip optical disc  27  onto turntable  13  for subsequent rotation. As detailed in FIG. 2, that is a partial cutaway side view taken along the line A-A of FIG. 1, on the top of turntable  13  are a disc-setting table  29  for bearing disc  27  horizontally and a concave portion  30  for accommodating convex portion  31  of disc clamp  32 . Together with concave portion  30 , convex portion  31  horizontally moves disc  27  to a correct position for gripping and thus for rotation about turntable shaft  33 . The top of convex portion  32  is rotatably connected to disc clamp head  18  by a connecting member  34  and is provided with bearings  35  for its rotation. While the top portion of turntable  13  is rotatably stabilized by disc clamp head  18  of clamp arm  17 , the middle portion of turntable shaft  33  is rotatably held by bearings  36  mounted on support frame  37  and the bottom end is supported by pivot  38 . Support frame  37  also holds turntable motor  39 . Turntable shaft  33  is rotated by turntable motor  39  through a power transmission system, including gear  40  mounted on motor shaft  41  and gear  42  mounted on the near-bottom end of turntable shaft  33 .  
         [0047]    Apparatus  1  has two optical units  43  and  44  horizontally supported by a common frame  45  that is held by the top portions of the side panels of structural frame  2 . Optical unit  43  has an optical read head  46  with a lens system  47  for reading the information stored on the lower surface of disc  27 . Read head  46  is supported by a bearing-type carrier member  48  which is slideable along a sliding rail  49 , and a carrier member  50  having a hole with a female screw which is engaged with a screw shaft  51 . Screw shaft  51  is rotatably supported by bearings  52  and  53  mounted on common frame  45  and has a gear  54  engaged with gear  55  on motor shaft  56  of motor  57 , thus forming a driving mechanism for optical read head  46 . Similarly disposed horizontally on the other end of the same common frame  45  is optical unit  44  that comprises an optical read head  58  with a lens system  59 , support bearings  60  and  61 , a bearing-type carrier member  62 , a carrier member  63  with female screw, a gear  64  on screw shaft  65 , a gear  66  on motor shaft  67  of motor  68 , thus forming a driving mechanism for optical read head  58 . Optical read heads  46  and  58  are to the best extent arranged to have travelling paths falling onto the same imaginary travelling plane (not shown) parallel to the disc surface. Upon receiving power signals from microprocessors (not shown), motors  57  and  68  independently and simultaneously move optical read heads  46  and  58  to predetermined distances in a radial direction of disc  27  for simultaneously reproducing information from two separate tracks of information-stored area  69  on the same surface of disc  27 .  
         [0048]    In order to perform the abovementioned multitasking, motor  39  and thus disc  27  are rotated at a constant angular velocity (CAV) method. Even though being reduced to half, the storage capacity of a compact disc employing the CAV method remains enormous, for instance, an 120-mm optical disc can still hold a minimum of 250 megabytes of data. Most importantly, the CAV rotation method allows the apparatus of the present invention to rotate at a constant, higher angular velocity for multitaskingly performing high-speed information reproduction.  
         [0049]    Referring now to FIGS.  3 - 7 , another embodiment of the present invention will be described in detail hereinbelow.  
         [0050]    [0050]FIG. 3 is a perspective, partial-cutaway view of a multitasking information processing apparatus  70  in accordance with the present invention, showing a front disc compartment  71  and a rear disc compartment  72  loaded with multisized discs, a pair of disc-compartment transporting means  73  for compartments  71  and  72  retractable into and out of playhousing  74 , and various control means on front panel  75 . Note that neither the disc-compartment transporting means on the other side of apparatus  70  nor optical units are shown in FIG. 3. The pair of disc-compartment transporting means  73  not only allows both disc compartments to extend out of and retract into playhousing  74  but also enables front disc compartment  71  currently containing a single 120-mm optical disc to be independently extended to a disc loading/unloading position without disturbing the information reproduction being proceeded in rear disc compartment  72 . As shown in FIG. 3, seven smaller optical discs with 45 mm in diameter are horizontally spaced in rear disc compartment  72 . In the front panel  75  of apparatus  70 , there are a push-type button  77  for the open/close operation of front disc compartment  71 , a turn-type button  78  for the open/close operation of both compartments  71  and  72 , a microphone connector  79  for sound output to an earphone or speakers (not shown), and a volume controller  80  for adjustment of sound level. Also equipped in apparatus  70  is lockout device  76  for locking disc compartments  71  and  72  and thus for safeguarding the optical discs stored therein from being unauthorizedly removed. In addition to a mechanical key, the lockout device  76  is responsive to an electrical signal issued by a host computer, so that it allows the open/close operation of disc compartments controlled from the input of the keyboard of a host computer (not shown).  
         [0051]    A partial cutaway view of the underside of the subchassis traverse driving mechanism  81  taken along the line B-B of FIG. 3 is shown in FIG. 4. Servo motor  82  fixed to the subchassis of front disc compartment  71  has a transverse rubber-roller  83  that tightly contacts the chassis of playhousing  74 . Upon rotating, transverse rubber-roller  83  thus move front disc compartment  71  through disc-compartment transporting means  73  to a disc loading/unloading position or a disc playing position. Rear disc compartment  72  is similarly moved by servo motor  84  with a transverse rubber-roller  85 . In order to enable both disc compartments to perform simultaneous close/open operation, the rear end of front disc compartment  71  is provided with protruding part  86  having a center hole and the front end of rear disc compartment  72  is furnished with protruding part  87  having also a center hole. Both center holes are aligned so as to allow the fastening/unfastening operation of latch  88  controlled by solenoid  89 .  
         [0052]    The exploded perspective view of disc-compartment transporting means  73  of FIG. 3 is detailed in FIG. 5. Playhousing  74  is made to have narrow openings  90  and  91  that form supporting rails  92  and  93  respectively. Supporting rails  92  and  93  having bearings  94  and  95  respectively support a suspended sliding device  96  that has five guiding rails. The top and the bottom guiding rails  97  and  98  of suspended sliding device  96  have bearings  99  and  100  respectively. All together, these rails and bearings allow suspended sliding device  96  to perform sliding operation inbetween supporting rails  92  and  93 . On suspended sliding device  96 , guiding rail  101  has bearings  102  and  103  and guiding rail  104  has bearings  105  and  106 , while guiding rail  107  has no bearing. Guiding rails  101  and  104  and their respective bearings form a gap accommodating sliding rail  108  that is fastened only to front disc compartment  71 . At the distal end of sliding rail  108 , there exists a sliding roller  109  that extends to rear disc compartment  72 . Thus, front disc compartment  71  can individually slide to a disc loading/unloading position. Fastened to rear disc compartment  72  is a sliding rail  110  with sliding rollers  111  and  112 , which slide along the space formed by guiding rails  104  and  107 . Because of the arrangement of suspended sliding device  96 , rear disc compartment  72  can thus be fully opened into a disc loading/unloading position.  
         [0053]    [0053]FIG. 6 is an illustrative top plane view of the multitasking information processing apparatus  70  seen in FIG. 3 therein horizontally disposed with eight optical discs and six optical units. Suited in front disc compartment  71  are an 120-mm disc  113  horizontally disposed on turntable  134  and two optical units  121  and  122  that are able to independently and simultaneously move to any predetermined tracks in radial directions with respect to disc  113  for multitaskingly reproducing information stored on the lower surface of disc  113 . It is also possible that each optical unit  121  or  122  has an additional optical read head as the configuration to be shown in FIG. 15 for simultaneously reproducing information, if any, stored on the upper surface of optical disc  113 .  
         [0054]    In addition to the 120-mm disc, turntable  134  stored in disc compartment  71  can be used to hold a disc with a smaller disc diameter. Turntable  134  is capable of rotating in a CLV or CAV scheme. For a CLV-recorded disc, only optical unit  121  is in operation; while optical unit  122  will be additionally in effect if the information of disc  113  is detected to be in a CAV-recorded scheme. Thus, either CAV-recorded or CLV-recorded disc can be scanned accordingly for information reproduction: while a CLV-recorded disc doubles its storage capacity, a CAV-recorded disc can be scanned in a high-speed, multitasking way.  
         [0055]    Horizontally disposed in rear compartment  72  are seven 45-mm-diameter discs  114 - 120  respectively stored on turntables  135 - 141  and four optical units  123 - 126  respectively comprising optical read heads  127 - 132 . The disc-setting tables of turntables  136 - 141  are arranged in such a manner that discs  114 - 120  are horizontally aligned with each other, thus falling onto an imaginary disc plane (not shown). Optical read heads  129 - 132  are also aligned to the best extent, forming a horizontal travelling plane (consisting of the broken circular lines) underneath and parallel to the imaginary disc plane for facilitating their focusing during retrieving the information stored on the lower surfaces of discs  114 - 120 .  
         [0056]    While FIG. 6 shows a configuration in which optical read heads  127 - 132  are all arranged to face the lower surfaces of discs  113 - 120 , it is possible that some of the optical units  121 - 126  and thus their respective optical read heads  127 - 132  are arranged to face the upper surfaces of discs  113 - 120  so as to provide capability for retrieving information stored on the lower and the upper surfaces of these discs.  
         [0057]    Turntable  137  and disc  116  are normally rotated in the CAV method by a turntable motor  722  that also drives the other six turntables and thus discs to rotate in the CAV method. As illustrated by the broken circular lines, each of optical units  123 - 126  is able to travel horizontally to an optical disc selected between discs  114 - 116 , between discs  116 - 118 , between discs  116 ,  119  and  120 , and between discs  118  and  119 , respectively, for information reproduction. Information stored on the 45-mm discs is preferably in the CAV scheme, in order for optical units  123 - 126  to perform high-speed, multitasking information reproduction. A single side of a 45-mm disc of this type is capable of holding a minimum of 60 megabytes of data, sufficient for storing a package of executable software programs such as a combination of Microsoft Word® Version 6.0a (about 17 megabytes), Microsoft Excel® Version 5.0 (about 17 megabytes), and Microsoft PowerPoint® Version 4.0 (about 18 megabytes). Use of a 45-mm disc or other similarly small discs is also more realistic than that of an 120-mm disc because software developers such as Microsoft®, WordPerfect®, or Lotus® are most likely to produce their own software discs but each of their software programs is not big enough to even fill up 15% of an 120-mm disc capacity. This also gives a user flexibility to choose a preferred program, for instance, a word processing program between WordPerfect® Version 6.0a (about 28 megabytes) and Microsoft Word®, since both are unlikely to be stored on the same disc.  
         [0058]    As shown in FIG. 6, disc  116  is capable of being simultaneously scanned by three optical units  123 - 125 . This allows three executable software programs, for instance, Microsoft Word®, Excel®, and PowerPoint®, to be simultaneously executed. Disc  118  that can be scanned by optical units  124  and  126  is an ideal location for storing a Microsoft Windows® 95 disc containing a disk operating system (DOS) and other shared programs. While running executable programs from discs situated in rear disc compartment  72 , a user can enjoy digital music by playing a disc situated in front disc compartment  71 . The individual open/close operation capability of front disc compartment  71  through disc-compartment transporting means  73  (shown in FIG. 5) further allows a user to change a music disc, when needed, without interrupting his/her active programs that are based on the information reproduction of the discs situated in rear disc compartment  72 .  
         [0059]    [0059]FIG. 7 is a block diagram of a control system of the multitasking information processing apparatus of FIG. 6. Basically, each of optical units  121 - 126  seen in FIG. 6 comprises a respective one of optical read heads (i.e., pickups)  127 - 132  and a separate driving means  705 . Each of optical units  121 - 126  is interfaced with a separate signal amplifier  701 , a separate servo system  704 , and a separate signal-processing system. Each servo system  704  comprises several servo controls that separately control a separate driving means  705  for radial tracking of a respective one of optical read heads  127 - 132  as well as the focusing of said respective one of optical read heads  127 - 132 . Each signal-processing system comprises a separate CIRC (Cross Interleaved Reed-Solomon Code) decoder  706 , a separate CD-ROM decoder  707 , and a separate RAM (random access memory)  708 . In essence, each optical read head is capable of being independently moved by a separate driving means controlled through a separate servo system to a predetermined disc-track position of an optical disc selected from discs  113 - 120  and being independently focused thereat for retrieving information stored thereon.  
         [0060]    Signals sensed by each of optical read heads  127 - 132  are very weak and thus amplified by signal amplifier  701  to derive usable error signals and high-frequency signals. The derived error signals interface with respective servo system  704  to control focusing and radial tracking of the respective one of optical read heads  127 - 132 . CLV/CAV controls  702  and  703  that also receive the derived error signals through high-speed system control bus  716  are used to respectively control the rotation speeds of turntable motors  721  and  722  at a constant linear velocity (CLV) scheme when either of optical read heads  127 - 132  senses CLV-recorded information from discs  113 - 120 . The high-frequency signals derived from each of optical read heads  127 - 132  are in a compact disc format or specifically in the EFM (eight-to-fourteen modulation) format and thus need to be processed by a signal-process system comprising CIRC (Cross Interleaved Reed-Solomon Code) decoder  706 , CD-ROM decoder  707 , and RAM (random access memory)  708  in order for the signals to be deinterleaved, demodulated, and decoded for error-correction process, restoring the original sequence of data symbols, and finally converting the 14-bit word back to the original 8-bit data symbol. RAMs  708  are used in temporarily storing data for reassembling during the signal processing proceeded in the respective signal-process system. A digital-to-analog converter (D/A C)  710  and audio amplifier  711 , which are only necessary when discs have audio tracks, is shared by optical units  121 - 126  for discs  113 - 120 .  
         [0061]    In order for multitasking to take place most effectively, disc  116  disposed on turntable  137  is normally rotated in the CAV method by turntable motor  722  that also provides the same rotation speed for turntables  135 ,  136 , and  138 - 141 . Optical read heads  129 ,  130 ,  131 , and  132  are able to travel through controlled swinging by respective driving means  705  to positions proximate the lower surface of an optical disc selected between discs  114 - 116 , between discs  116 - 118 , between discs  116 ,  119  and  120 , and between discs  118  and  119 , respectively, for simultaneously retrieving a plurality of information sets stored thereon. This allows the total number of optical units and thus optical read heads to be less than that of turntables, thus not only reducing production costs but still providing high-efficiency and multitasking capability to the information retrieving operation proceeded on the same disc and/or different discs.  
         [0062]    Also provided in FIG. 7 are (1) a plurality of control means comprising microprocessors (MPUs)  712 - 714 , ROM/RAM (read only memory and random access memory)  715 , and (2) data transmitting means comprising high-speed system control bus  716 , ITDM (intelligent time-division multiplexer)  717 , wide-band host interface bus  718 , and ROM/RAM (read only memory and random access memory)  719 . Each of buses is a collection of multiple lines forming control bus, address bus, and data bus for carrying module-to-module communications. Multitasking capability is necessary for said control means and said data transmitting means in order for a plurality of sets of information to be simultaneously handled and transmitted to a host computer  720 . MPUs  712  and  713  that share ROM/RAM  715  issue commands or control signals to CIRC decoders  706  and CD-ROM decoders  707  in a parallel manner through high-speed system control bus  716 . The read only memory portion of ROM/RAM  715  contains basic instructions needed for MPUs  712  and  713  to issue a plurality of control signals to a plurality of servo systems  704  and a plurality of driving means  705  so as to independently and simultaneously move optical read heads  127 - 132  to a plurality of predetermined disc tracks located either on the lower surface of one disc or on the lower surfaces of several discs for multitaskingly reproducing a plurality of information sets constituting either a program or several programs stored thereon. The random access memory portion of ROM/RAM  715  is used for temporarily storing the instructions issued from host computer  720  served as the input of MPUs  712  and  713  for controlling the travelling motions of optical read heads  127 - 132 .  
         [0063]    After being deinterleaved, demodulated, and decoded by CIRC decoders  706  and CD-ROM decoders  707 , the plurality of information sets retrieved from optical read heads  127 - 132  are converted back to the original 8-bit data symbol. The plurality of converted information sets are multiplexed by ITDM  717  in order to be simultaneously transferred to host computer  720  through wide-band host interface bus  718  that is interfaced with microprocessor  714 , and ROM/RAM  719 . Microprocessor  714  with multitasking capability controls the simultaneous transmitting of the multiplexed information to host computer  720 . The read only memory portion of ROM/RAM  719  contains basic instructions defining how MPUs  712  and  713  should work coordinately and simultaneously together to issue commands to optical units  121 - 126  in order for a plurality of them to efficiently, multitaskingly, and simultaneously retrieve a plurality of information sets constituting one program or several programs stored on one disc or separately on plural discs. The random access memory portion of ROM/RAM  719  is used as a buffer memory storage for temporarily storing the information to be transmitted when host computer  720  is tied up with other operations. When ready, the host computer  720  can accept the information temporarily stored in ROM/RAM  719  in bursts according to the instruction of MPU  714 . While three microprocessors  712 - 714  are shown in FIG. 7 for controlling the reproducing and transmitting of information, it is possible that more microprocessors can be utilized or these microprocessors are replaced by a single high-performance multitasking microprocessor having a full 32-bit architecture with 32-bit address and data bus systems or better. Similarly, a less proportion of shared electronics such as digital-to-analog converter  710  and audio amplifier  711  are possible; so are other electronic configurations.  
         [0064]    Owing to the high-speed and multitasking nature of the information processing apparatus of the present invention, it becomes practical to execute programs directly from optical discs. This eliminates the conventional, tedious and time-consuming software installation procedure in which a software stored on a plurality of floppy disks or an optical disc has to be (decompressedly) copied to a hard-disk drive of a computer from where the software is then executed. This advantage is described in detail using the exemplary configuration of FIGS. 6 and 7 in which presumedly disc  116  contains a package of Microsoft® software programs including Microsoft Word®, Excel®, and PowerPoint® and disc  118  is a Microsoft Windows® 95 disc containing a disk operating system (DOS) program and other shared Windows files for the basic operation of host computer  720 . After discs  116  and  118  are properly loaded, optical read heads  129 - 132  first recognize the existence of both discs and their corresponding programs in order to create a disc directory-structure file, which is similar to a file allocation table (FAT) created for monitoring the use of the sectors of a hard-disk drive, for storing the basic information of both discs such as disc locations and directory structures to the hard-disk drive of host computer  720 . The disc directory-structure file is updated only if discs  116  and  118  are replaced by others or newer discs are added to other empty turntables. There is essentially no software installation as manually needed in the conventional practice. Software programs can be written in such a way as to automatically creating or modifying: (1) a user definable boot file (such as autoexec.bat) on a hard-disk drive in order to quickly direct the host computer  720  the locations of the software programs contained in discs  116  and  118 , and (2) a working directory on the hard-disk drive of host computer  720  for storing resulting files that will be created or changed during the execution of the programs.  
         [0065]    Because none of the program files on the optical disc is copied to the hard-disk drive, the approach of the present invention essentially eliminates software installation, therefore alleviating the heavy burden of a hard-disk drive in information reproduction. Note that according to the conventional practice both software programs and resulting/working files are mixedly stored on a hard-disk drive for the routine operation of a computer. Accordingly, the present invention provides two additional advantages: (1) eliminating the need to demand a high-capacity hard-disk drive for storing program files that will never be altered throughout the entire life of their usage, and (2) eliminating time-consuming hard-disk drive maintenance that involves file defragmentation in order for a hard-disk drive to regain its performance.  
         [0066]    Further, the capability of launching a program directly from an optical disc loaded in the information processing apparatus of the present invention eliminates the need for an end user to make a set of backup copies (on floppy disks) for a purchased software program and thus a software developer can make its CD-version products not executable from a hard-disk drive, accordingly minimizing illegal-copying of a software. This can be simply based on, for instance, the difference in recording formats between the optical disc and the hard-disk drive. A software developer can embed a key code in the EFM format onto an optical disc containing the program to be copy-right protected. Without detecting the presence of the embedded key code in the EFM format, a computer will not execute the program. This in effect disables the program to be executed from a hard-disk drive, thus completely prevents spreading of a software program. This type of software program can be considered to be a hardware in nature, because its copy-right protection is not relied on the conventional practice of using a sealed envelope. As with software manufacturers are well protected, consumers have their opportunity to really use a fully-working version of a software before deciding whether to keep it or not.  
         [0067]    During the process of booting, host computer  720  in accordance with the booting instruction of a user defined boot file (e.g., autoexec.bat) created on the hard-disk drive interfaces through wide-band host interface bus  718  with MPU  714  that determines and issues the most efficient instructions to MPUs  712  and  713  in order for them to provide power signals to respective servo systems  704  and respective driving means  705  so as to move optical read heads  130  and  132  to disc  118  for simultaneously reproducing the disk operating system (DOS) information and Microsoft Window® 95 information. It is preferred that ROM/RAM  715  stores a set of predefined instructions; and, software programs stored on the disc are written and arranged in a particular manner so that optical read head  130  is controlled to move specifically to a predetermined position selected from a set of disc tracks that contain sound information and/or other non-video files while optical read head  132  is instructed to move specifically to another predetermined position selected from another set of disc tracks that contain video information and/or other non-sound files. In other words, optical read head  130  is controlled for producing sound effects and other non-video files while optical read head  132  is instructed mainly to produce video images and other non-sound files. Controlled by data transmitting signals issued by microprocessor  714 , video images can be transmitted in bursts through wide-band host interface bus  718  directly to a video circuit (not shown) of host computer  720 . With this scheme, proceeding of video images and sound effects can be simultaneous, thus allowing a program to be executed at a much higher speed and arriving at a ready-to-run state in no time.  
         [0068]    On the contrary, in accordance with the current conventional practice, the proceeding of a Windows-based software program is inevitably interrupted constantly, especially when video information and sound information are too large to be read within a reasonable time period.  
         [0069]    Disc  116  loaded on turntable  137  can be simultaneously accessed by three optical read heads  129 - 131 . Accordingly, an information processing apparatus of this type will hardwarely allow a user to simultaneously execute three different programs at the same time. Front disc compartment  71  seen in FIG. 6 has its own turntable  134 , optical units  121  and  122 , CLV/CAV control  702  and turntable motor  721  (both shown in FIG. 7) for rotating and scanning an 120-mm CD at either the CLV or the CAV method; thus, an audio CD can be simultaneously played while a user is working on the software programs stored on the discs disposed in rear disc compartment  72 .  
         [0070]    Shown in FIG. 8 is an information processing apparatus  800  with an alternative configuration of disc-storage locations and optical units, having a rear disc compartment  801  different from FIG. 6. The rear disc compartment  801  of FIG. 8 bears six discs  802 - 807  and six optical units  808 - 813 . In accordance with the present invention, at least, discs  802  and  803 , discs  804  and  805 , and discs  806  and  807  are respectively aligned with each other. Further, each of optical units  808 - 813  is capable of linearly moving along screw shaft  814  and sliding rail  815  by a predetermined distance in a radial direction of a selected disc so as to allow each of respective optical read heads  816 - 821  to be correspondingly positioned on a predetermined track for retrieving information stored thereon. Thus, each of discs  802 - 807  can be either scanned by either one optical read head or by two optical read heads simultaneously for information reproduction.  
         [0071]    [0071]FIGS. 9A and 9B are perspective top and cutaway side views respectively of the turntable showing a disc-setting table and a disc-holding and-releasing means having a self-clamping and-releasing mechanism for detachably holding an optical disc thereon in accordance with the present invention. The disc-holding and-releasing means and thus the self-clamping and -releasing mechanism of the turntable herein are characterized by miniaturization and are designed to facilitate disc loading/unloading operation. In the following, exemplary illustration is given to turntable  135  and disc  114  disposed thereon as seen in FIG. 6. To facilitate illustration, only FIG. 9B is loaded with disc  114 . Turntable  135  basically comprises a disc-setting table  150  for horizontally bearing a disc thereon and an elevated center portion  151  which is sized to fit into the center hole of optical disc  114  as shown in FIG. 9B. Elevated center portion  151  comprises a hollow member  152  being in a cylindrical shape wherein a spring device having a flat bottom  153  and four strip ends  154  is situated on the top of spring  155  that provides up-and-down motion through a guiding ring  156 . During disc loading, spring strip ends  154  are forced to retract through four openings  157  to the insider of hollow member  152  and then returns to its outward-biased normal position that also provides a slightly downward force so as to hold disc  114  in place as shown in FIG. 9B. Also comprised in the elevated center portion  151  is a release mechanism having a pressing button portion  158  and a release bottom portion  159 . Pressing button portion  158  is confined in the inside of hollow member  152  by means of the circular edge  160  of hollow member  152 . When pressing button portion  158  is pushed by a user&lt;&lt;s finger for disc unloading, release bottom portion  159  and thus flat bottom  153  are accordingly moved downward to cause the retraction of spring strip ends  154  into the insider of hollow member  152 , thus releasing disc  114 . To obtain self-releasing function, disc-setting table  150  is made to comprise disc-releasing springs having one end fixed held by the rectangular slots  161  and the other end  162  biased upward but capable of being pushed downward when disc  114  is held in place by spring strip ends  154 .  
         [0072]    Hollow member  152  may optionally have a noncircular outer boundary such as having a locking portion  163  for adapting an optical disc having a center hole with a complementary boundary or shape so as to ensure precision griping, thus allowing disc  114  to rotate at a speed much higher than the conventional practice.  
         [0073]    [0073]FIG. 10 is an enlarged perspective top view of optical unit  124  and three surrounding discs  116 - 118  which are arranged in the same configuration as seen in FIG. 6, illustrating that a single driving means (or swing mechanism) is used to horizontally move an optical read head selectively between disc tracks as well as between a plurality of discs for information reproduction in accordance with the present invention. Information starting from disc directory structures is stored from each innermost track  164  to the outermost edge of discs  116 - 118 . Located at the distal end of optical unit  124  is an optical read head  130  that is currently positioned at the innermost track  164  of disc  118 . Optical read head  130  is able to swing about axis  166  that is rotatably supported by bearing  191  and supporting frame  222  attached to driving means  168 , in accordance with a broken circular line or travelling path  167 . The swing motion of optical read head  130  is powered by a driving means (or swing mechanism)  168  through a toothed belt  169 . Discs  116 - 118  are horizontally aligned each other so as to facilitate the focusing action of optical read head  130  to each of discs, and are concentric with respect to axis  166  so that the innermost tracks of the three discs are reachable as indicated by the broken circular line  167 . Thus, by spinning these discs and by swinging optical read head  130  about axis  166 , information stored on any tracks of discs  116 - 118  becomes readily reproducible.  
         [0074]    [0074]FIG. 11 is a cutaway view, showing turntable  139  on which disc  118  is horizontally disposed and optical unit  124  that comprises optical read head  130  and driving means (or swing mechanism)  168  for providing a necessary force to horizontally swing optical read head  130  to a selected position. Turntable  139  has a turntable shaft  213  which is rotatably supported by bearings  214  and  215  that are attached to supporting frame  216  fastened to the bottom frame  224  of compartment  72 . At the bottom portion of turntable shaft  213  are pulleys  217  and  218  that are connected respectively by toothed belt  219  and  220  for transmitting rotation power from turntable motor  722  seen in FIG. 7 and to other turntables. Under these circumstances, a plurality of turntables can be driven by a single turntable motor. This greatly reduces construction costs and space for commercializing the optical information processing apparatus of the present invention.  
         [0075]    Optical read head  130  situated in optical-read-head housing  221  comprises a semiconductor laser diode  170 , a lens system  171 , photosensors  172  and  173 , and a focusing mechanism  174  situated on the distal end of optical-read-head housing  221 . As detailed in FIG. 12, semiconductor laser diode  170  is a light source for producing a laser beam. The laser beam emitted from laser diode  170  is converted by a collimator  175  to a parallel light beam  176  that is bent at an angle of 90° by means of a mirror  177  and is then focused by a focusing mechanism  174  onto the information-stored surface layer  178  of disc  118 . A beam of light reflected from the information-stored surface layer  178  is deflected at an angle 90° C. by mirror  175  and is then condensed through a quarter-wavelength (λ/4) plate  179 , a polarizing beam-splitting prisms  180  and  181 , a lens  182  to a photosensor  172  that reads the change of the output signals.  
         [0076]    Focusing mechanism  174  detailed in FIG. 12 comprises an objective lens  184  attached to a vertically movable device  185 , tension springs  187 , and focus-tracking coil  188  wound around stationary bobbin  189 . Vertically movable device  185  has a ring-type magnet  186  fixedly situated therein. Tension springs  187  provide tension and keep objective lens  184  straight in the focusing mechanism  174  as the objective lens  184  vertically moves. Projection lens  183  and photosensor  171  are arranged in a direction of the beam that is reflected from disc  118 , bent by mirror  177 , and condensed through λ/4 wave plate  179 , polarizing beam-splitting prisms  180  and  181 , thereby detecting a focusing error. In the focused condition, a zero error exists from photosensor  171 . When an error signal produced from either a too-far or a too-close condition is detected by photosensor  171 , the detected error signal is amplified and fed to focus-tracking coil  188  wound around the stationary bobbin  189  which then produces a magnetic field to cause ring-type magnet  186  and thus objective lens  184  to move in the relevant direction until the error signal becomes zero and the beam is in focus.  
         [0077]    As shown in FIG. 11, the other distal end of optical-read-head housing  221  is attached to a shaft  190  that is rotatably supported by bearings  191  and  192  and has a pivoted end  193  for its swinging. Bearings  191  and  192  are respectively supported by tope and bottom supporting frames  222  and  223  fixedly attached to driving means  168 . A stop pin  194  fixedly attached to the bottom frame  224  of rear disc compartment  72  and two helical tension springs  195  and  196  arranged in opposite direction are provided in order to produce torque restrain for a steady swing of shaft  190  about its axis  166 . A stop pin  197  fixedly attached to the bottom portion of shaft  190  is provided for shaft  190  to rest at a reference position. Toothed belt  169  connects pulley  198  on shaft  190  and pulley  199  on moving-coil shaft  200  for transmitting rotation power. Pulley  199  has a diameter larger than pulley  198  so that driving means  168  can provide a maximal swing angle of 300°. Supported by bearings  201 , moving-coil shaft  200  has top and bottom pivots  202  and  203  that are respectively held in place by top and bottom frames  204  and  205  for its swing.  
         [0078]    Driving means (or swing mechanism)  168  as seen in FIG. 11 is further detailed in FIG. 13 in a partial cutaway top view in which top frame  204  and supporting frame  222  (seen in FIG. 11) are removed. In accordance with the present invention, driving means  168  is able to provide a rotating force to horizontally swing optical read head  130  about axis  166  for a maximal swing angle of 300° as indicated by the broken circular line or travelling path  167 . This allows optical read head  130  to travel between tracks of a selected disc as well as between discs  116 - 118 . Most importantly, the travelling of optical read head  130  between these discs is as rapid as that between tracks of a selected disc, because the travelling involves neither multidirectional nor three-dimension maneuver but needs only one single-directional movement.  
         [0079]    In order to provide a rotating force, driving means  168  is arranged as shown in FIGS.  11  and  13 , in which one end of moving coil  206  is fixedly attached to moving-coil shaft  200 , the other end is allowed to freely travel in the uniform air gap  207  defined by outer soft-iron pole piece  208  and inner pole piece  209 . Bonded to outer soft-iron pole piece  208  is magnet  210 . Air gap  211  extending to the inner area of covering frame  212  is provided in order for moving-coil shaft  200  with attached moving coil  206  to be assembled into the configuration of FIG. 13 and also allows moving-coil shaft  200  and the fixedly attached end of moving coil  206  to rotate about the axis defined by pivots  202  and  203  (FIG. 11). Attached to the outer circular area of magnet  210  is laminated steel shell  213  that acts as a magnetic collector ring and also effectively shields the element from stray fields.  
         [0080]    Illustrated in FIG. 14 is another preferred embodiment of the present invention, wherein information processing compartment  300  has an optical unit  301  comprising an optical read head  302  and a driving means (or swing mechanism)  303 , wherein said driving means  303  enables said optical read head  302  to travel by swinging about axis  316  to any tracks on discs  304 - 309  respectively disposed on turntables  310 - 315  for information reproduction. Each of these discs has a diameter of 45 mm. Within the compartment, these discs are horizontally and concentrically disposed at predetermined positions such that the disc centers are at an equal distance from the axis  316  of optical unit  301 . Underneath turntable  310  is a turntable motor (not shown) which is also used to drive turntables  231 - 315  simultaneously. Each of turntables  310 - 315  comprises its own disc-loading and releasing means with self-clamping and -releasing feature so that once being loaded onto turntables  310 - 315 , discs  304 - 309  will remain being clamped at any time and can be rotated simultaneously. Thus, without going through other intermediate loading stages (such as internal disc changing or selecting used in the prior art), information reproduction can be effectively proceeded by simply moving optical unit  301  to a disc selected between discs  304 - 309  disposed within the same compartment. This eliminates any need to design an information processing apparatus equipped with a disc-turntable rotating mechanism, a disc transporting means, or other disc changers described in prior arts such as U.S. Pat. Nos. 5,119,354, 5,146,451, 5,193,079, and 5,334,218.  
         [0081]    Driving means  303  enables optical unit  301  to perform a maximum of 350° swing about axis  316 , starting from position  318 , for accessing selectively between disc tracks and discs  304 - 309 . In essence, optical read head  302  of optical unit  301  travels in accordance with the broken circular line  317 ; thus, any information stored on these discs becomes readily accessible. Because of being designed for discs with smaller sizes and being equipped with a single turntable motor and a shared optical unit  301 , compartment  300  can be economically produced in a size similar to the commercially available single 120-mm-disc player, for being installed into the interior of a personal computer.  
         [0082]    Apparatus  300  is optionally equipped with a servo control (not shown), which enables the turntable motor to rotate at a constant linear velocity (CLV) in addition to at a constant angular velocity (CAV). Use of the CLV-recording method doubles the storage capacity of the 45-mm disc to 120 megabytes from 60 megabytes compared with use of the CAV-recording method. This is advantageous for a software developer to fit a lengthy program or several programs as a package into a single small-sized disc. On the other hand, if information to be stored in a 45-mm disc is less than 60 megabytes, the CAV method is preferred in order to allow information reproduction to be proceeded at a higher speed.  
         [0083]    In a further preferred embodiment of the present invention, discs  304 - 309  shown in FIG. 14 are arranged in a manner so that there is an open space between disc  304  and disc  309  for optical unit  301  to park at position  318 . This open space allows optical unit  301  of apparatus  300  to further comprise an upper optical read head  320  in addition to lower optical read head  321  as shown in FIG. 15, without causing any inconvenience to disc loading/unloading operation. Upper and lower optical read heads  320  and  321  have configurations similar to the embodiments of optical read head  130  singularly situated in optical-read-head housing  221  hereinbefore detailed in FIG. 12. Optical-read-head housing  322  has a horizontal open slot  323  for an optical disc selected from discs  304 - 309  to insert therein so that the innermost tracks on both surfaces of the disc become simultaneously accessible to objective lens  323  of upper optical read head  320  and objective lens  323  of lower optical read head  324 . Note that objective lens  323  is disposed in a direction facing to objective lens  324 , so as to face the other surface (i.e., the upper surface) of an optical disc selected from disc  304 - 309 . The use of two optical read heads in an optical unit provides twofold advantages: doubling not only the information storage capacity of a disc but also the speed of information reproducing.  
         [0084]    While preferred embodiments of the present invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes, modification, and substitutions will occur to those skilled in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.