Abstract:
An optical media drive contains light reflective surfaces positioned about a transparent center portion of the optical media. The light reflective surfaces reflect laser light from a laser unit of the drive which is directed toward the transparent center portions of the optical media. Defects such as cracks in the optical media disturb the reflection. The disturbance is detected by a laser lens and represented by a signal corresponding to the size of the defect. Information about the cracks is used to determine a safe spin rate for the optical media.

Description:
FIELD OF THE INVENTION 
   The invention relates generally to optical drives, and in particular to detecting the structural integrity of optical media. 
   BACKGROUND OF THE INVENTION 
   Optical media typically come in the form of a round disc, which is spun in a drive device. The surface of the optical media is read by a laser device which moves radially about the disc as the disc spins to read data on the disc. Spin rates of the media have greatly increased since the original design. CD-ROM drives now have spin rates of 60 times the original spin rate. Such rates are still increasing. 
   High spin rates create destructive forces on optical media discs. If the discs have cracks or other structural integrity defects, they can break apart in the drive, destroying the disc, and harming the drive. The higher speed drives are both more expensive, and more likely to cause a disc to break apart, increasing the likelihood of catastrophic failure of both the disc and the drive. 
   SUMMARY OF THE INVENTION 
   An optical media drive detects structural or mechanical defects in optical media. The drive contains light reflective surfaces positioned above an inner transparent center portion of the optical media. The light reflective surfaces reflect laser light from a laser in the drive which is directed toward the transparent center portions of the optical media. Defects, such as cracks in the transparent center portion of the optical media disturb the reflection. The disturbance is detected by a laser lens and converted to a signal representing the size of the defect. 
   In one embodiment, the transparent center portion of the optical media is an inner ring having an inner vertical edge, and horizontal portion extending radially from the inner vertical edge to a data portion. An upper clamping plate of the drive has a mirror on a side that clamps the central portion of the optical media, and a transparent lower plastic plate. Each of the mirrors is positioned to reflect light from the laser back to the laser lens. 
   The laser of the drive is first focused proximate the inner vertical edge. When reflection from the mirror is detected, the media is spun at a low rpm rate, such as 1× as used in CD-ROM drives. Cracks in the inner ring of the media will disrupt the reflection received by the laser lens, causing the converted electrical output signal to indicate a gap in reflection similar to data pits on the data portion of the optical media. Such gaps are normally many times the size of a data pit in the media. The length of the disruptions of the signal represents the width of the crack. 
   The disc is rotated and the laser is moved from the inner to the outer circumference of the transparent inner ring. Information about cracks is collected, such as the length of a crack. The information about the cracks is used to determine a safe spin rate for the optical media. With small cracks, it may still be safe to spin the media at high rates. With larger cracks, slower spin rates are used. The lower spin rates reduce the risk of using media that has suspect integrity, but still allows the use of such media. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a block schematic diagram of an optical media reading device. 
       FIG. 2  is a representation of an optical media with and without cracks in combination with a graph of an output signal of the reading device of FIG.  1 . 
       FIG. 3  is a flowchart illustrating a method of checking optical media for defects. 
       FIG. 4  is a block diagram of a computer system to which the optical media reading device of  FIG. 1  is attached. 
   

   DETAILED DESCRIPTION 
   In the following detailed description of sample embodiments of the invention, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific sample embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the invention is defined only by the appended claims. 
   The present invention comprises an optical media drive and software operable to detect integrity problems with optical media, such as cracks which might lead to failure of the media and possible damage to the media drive. Cracks usually start near a center hole of an optical media disc. Optical media discs include laser discs, CD ROM, DVD and other types of discs that are rotated within a disc drive and read by a light source such as a laser. 
   A portion of a disc drive device is indicated generally at  110  in FIG.  1 . An optical media is shown in the disc drive at  115 . It is held in place by an upper clamper plate  120  and a lower clamper plate  125 . The clamper plates and disc are rotated via a spindle  130 , about which the disc and clamper plates are centered. A laser unit  135  is used to read data from an outer data portion of the disc  115 . 
   In one embodiment of the invention, the laser unit  135  has enhanced focus capability enabling it to focus past the normal distance of data pits, typically about 1-2 mm past such normal distance. The center ring portion is the portion of the disc that is clamped by the upper and lower clamper plates, and is transparent. The lower clamper plate  125  is also transparent, allowing light from the laser unit  135  to pass, allowing light to be reflected by mirrors positioned on the underside of the upper clamper plate  120 . The term “transparent” refers to multiple gradations of transparency, from near lossless transmission of light to losses that permit enough light to return to the laser unit and be detected by a laser lens device. 
   A mirror  140  is supported by the upper clamper plate  120  proximate an inner horizontal ring portion  145  of the disc  115 . In operation, the laser unit begins by directing light toward the inner horizontal ring portion closest to an inner vertical edge  155  of the disc  115 , and receives light reflected back from the mirror. The laser progresses from the inner vertical edge  155  towards the outer vertical edge of the lower clamper plate  125  and the upper clamper plate  120 . 
     FIG. 2  is a diagram showing a signal output from the laser lens for a disc  210  with no cracks, and a disc  220  with one crack indicated at  225  on the inner portion of the disc. Graphs of the electrical output signal provided by the laser unit is shown below each corresponding disc. The signal from the disc  210  with no cracks is a flat line. In other words, a constant, uninterrupted reflection is observed at the laser lens. The signal from disc  220  shows repetitive drop offs  230  in the signal, corresponding to crack  225  as the crack rotates past the laser unit. The crack reduces the amount of light reflected, and is interpreted similarly to a data pit on the data portion of the disc, without modification to the disc drive laser circuitry. Since a crack is much larger than a normal data pit, it shows up as a significant loss of signal as shown in  FIG. 2  at  230 . The length of the loss of signal is related to the severity of the crack, and can be from several data pit lengths to several hundred thousand data pit lengths. 
     FIG. 3  is a flowchart of a method of detecting cracks in an optical disc using the above modified disc drive. The method in one embodiment is implemented in computer programming code stored on a computer readable medium. It is embodied in a device driver for running on a host processor, or may also be executed on a local processor in the disc drive itself, with messages passed back to the host for display to a user regarding the status of the disc. 
   When a disc is inserted into the disc drive at  310 , a slow spin rate is selected at  315  that is not likely to harm a defective disc, such as 1×for a CD ROM type of drive. The laser is commanded to focus the laser beam into a top corner near the inside vertical edge of the horizontal surface. When a reflection of the light is detected, the disc begins to spin. The laser lens output is then provided to a processor for detecting defects at  320 . If the disc is not cracked, the laser lens receives a constant and steady reflected beam. The beam is converted to an electrical signal that is sent to a processor for analysis. In a further embodiment, once a defect is detected, no more checking is done, and results are returned to a processor. 
   If no defects have been detected near the vertical edge of the disc after one or more revolutions of the disc, the beam is moved incrementally from the top corner of the vertical edge to the horizontal surface area away from the center hole until the data zone is reached. The length of the increments may be varied. In one embodiment, the increment corresponds to about 10 data tracks in width. In a further embodiment, the increments are approximately 10 microns. Other increments may also be used without departing from the scope of the invention. 
   If a defect has not been detected as determined at  335 , the drive is instructed to run at a normal spin rate at  340 . If a defect has been detected, the severity of the structural or mechanical defect is analyzed at  343 , and a safe spin rate if any is determined at  345 . Since the size of the crack or cracks is represented by the signal from the laser lens, empirical measurements are used to determine a safe spin rate at  345 , and the disc is then spun at that rate at  350  and processing ends at  355 . The size of the crack is measured as a width along a circumference of the disc. In further embodiments, the size of the crack includes the radial length of the crack corresponding to detection of the crack as the laser is moved one or more increments. 
   In one embodiment, an interrupt is generated, and a user of a computer system is provided a pop-up window alerting the user to the condition of the disc, and allowing the user to select whether or not to continue to use the disc at the lower safe rate, such as down to a 1× rate. The choice provides the user the ability to not continue in the event of degraded performance of some CDs or DVDs at slow rates. 
     FIG. 4  shows a block diagram of a personal computer system. The personal computer system is capable of executing methods associated with detection of cracks in optical media. The methods are expressed in computer programming language stored on computer readable medium such as diskette, CD, tape, carrier waves, etc. 
     FIG. 4  shows a more detailed block diagram of a personal computer system  400  according to the present invention. Personal computers come in all shapes and sizes, from hand held personal digital assistants to laptop, portable, desktop, tower and rack configurations. Such computers are also programmable with personal information, including customization data. Customization data includes data such as color schemes and cursor response controls as well as many others. Personal information is transferred in the same manner as described above in the following personal computer embodiment. 
   In this embodiment, a processor  402 , a system controller  412 , a cache  414 , and a data-path chip  418  are each coupled to a host bus  410 . Processor  402  is a microprocessor such as a 486-type chip, a Pentium®, Pentium II®, Pentium III®, Pentium®4, or other suitable microprocessor. Cache  414  provides high-speed localmemory data (in one embodiment, for example, 512 kB of data) for processor  402 , and is controlled by system controller  412 , which loads cache  414  with data that is expected to be used soon after the data is placed in cache  412  (i.e., in the near future). Main memory  416  is coupled between system controller  414  and data-path chip  418 , and in one embodiment, provides random-access memory of between 16 MB and 128 MB of data. In one embodiment, main memory  416  is provided on SIMMs (Single In-line Memory Modules), while in another embodiment, main memory  416  is provided on DIMMs (Dual In-line Memory Modules), each of which plugs into suitable sockets provided on a motherboard holding many of the other components shown in FIG.  4 . Main memory  416  includes standard DRAM (Dynamic Random-Access Memory), EDO (Extended Data Out) DRAM, SDRAM (Synchronous DRAM), or other suitable memory technology. System controller  412  controls PCI (Peripheral Component Interconnect) bus  420 , a local bus for system  400  that provides a high-speed data path between processor  402  and various peripheral devices, such as graphics devices, storage drives, network cabling, etc. Data-path chip  418  is also controlled by system controller  412  to assist in routing data between main memory  416 , host bus  410 , and PCI bus  420 . 
   In one embodiment, PCI bus  420  provides a 32-bit-wide data path that runs at 33 MHz. In another embodiment, PCI bus  420  provides a 64-bit-wide data path that runs at 33 MHz. In yet other embodiments, PCI bus  420  provides 32-bit-wide or 64 bit-wide data paths that runs at higher speeds. In one embodiment, PCI bus  420  provides connectivity to I/O bridge  422 , graphics controller  427 , and one or more PCI connectors  421  (i.e., sockets into which a card edge may be inserted), each of which accepts a standard PCI card. In one embodiment, I/O bridge  422  and graphics controller  427  are each integrated on the motherboard along with system controller  412 , in order to avoid a board-connector-board signal-crossing interface and thus provide better speed and reliability. In the embodiment shown, graphics controller  427  is coupled to a video memory  428  (that includes memory such as DRAM, EDO DRAM, SDRAM, or VRAM (Video Random-Access Memory)), and drives VGA (Video Graphics Adaptor) port  429 . VGA port  429  can connect to industry-standard monitors such as VGA-type, SVGA (Super VGA)-type, XGA-type (extended Graphics Adaptor) or SXGA-type (Super XGA) display devices. Other input/output (I/O) cards having a PCI interface can be plugged into PCI connectors  421 . 
   In one embodiment, I/O bridge  422  is a chip that provides connection and control to one or more independent IDE connectors  424 - 425 , to a USB (Universal Serial Bus) port  426 , and to ISA (Industry Standard Architecture) bus  430 . In this embodiment, IDE connector  424  provides connectivity for up to two standard IDE-type devices such as hard disk drives, CDROM (Compact Disk-Read-Only Memory) drives, DVD Digital Video Disk) drives, or TBU (Tape-Backup Unit) devices. In one similar embodiment, two IDE connectors  424  are provided, and each provide the EIDE (Enhanced IDE) architecture. In the embodiment shown, SCSI (Small Computer System Interface) connector  425  provides connectivity for up to seven or fifteen SCSI-type devices (depending on the version of SCSI supported by the embodiment). In one embodiment, I/O bridge  422  provides ISA bus  430  having one or more ISA connectors  431  (in one embodiment, three connectors are provided). In one embodiment, ISA bus  430  is coupled to I/O controller  452 , which in turn provides connections to two serial ports  454  and  455 , parallel port  456 , and FDD (Floppy-Disk Drive) connector  457 . In one embodiment, ISA bus  430  is connected to buffer  432 , which is connected to X bus  440 , which provides connections to real-time clock  442 , keyboard/mouse controller  444  and keyboard BIOS ROM Basic Input/Output System Read-Only Memory)  445 , and to system BIOS ROM  446 . 
   Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the invention. It is intended that this invention be limited only by the claims, and the full scope of equivalents thereof