Abstract:
An optical disc drive having a cover member attached thereto is disclosed. The cover member serves to protect optical components located in the optical disc drive from shock, vibration, and contamination. The cover member is affixed to the optical disc drive in the proximity of the optical components. The optical disc drive moves the optical components under the cover member when the optical components are not required for the operation of the optical disc drive. The optical components are, thus, held in a secure position by the cover member, which protects the optical components from shock and vibration. The cover member provides additional protection for the optical components by removing the optical components from the reach of a user. In addition, the cover member blocks any harmful light emissions by the optical components from contacting the user.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to optical disc drives and, more particularly, to a mechanism and method for securing and covering the optical pickup unit of an optical disc drive when the optical disc drive is not in use. 
     BACKGROUND OF THE INVENTION 
     Optical disc drives are devices that use light to translate information stored on an optical disc to a machine-readable format, e.g., binary data. Examples of optical disc drives are known in the art as compact disc drives (often referred to simply as CDs) and digital versatile disc drives (often referred to simply as DVDs). Some optical disc drives have the additional capability of being able to write data onto an optical disc by the use of a light source, e.g., a laser. Optical disc drives are being used in various applications including music and video playing and recording devices and computer data storage devices. As these applications become more portable, the optical disc drives also need to become more portable. For example, they must be compact and able to withstand the shock and vibration to which portable applications are commonly subject. 
     The optical disc is a round, flat device similar to a record. Digital data is stored in spiral tracks on the optical disc in much the same way analog audio information is stored in a spiral groove on a record. The data stored on an optical disc, however, is much more compact than the audio information stored on a record. For example, the radial distance between tracks on an optical disc is typically approximately 1.6 microns for a compact disc and less for a digital versatile disc. The data on the optical disc consists of a plurality of optical transitions that are detected or “read” by the optical disc drive as the optical disc spins. The optical disc may spin at varying speeds of up to 4000 rpm as data is being read from or written to the optical disc. 
     A schematic diagram of a side view of a conventional optical disc drive  100  is illustrated in FIG.  1 . The optical disc drive  100  is illustrated with an optical disc  110  attached thereto wherein data is stored on an optical surface  112  of the optical disc  110 . The optical disc drive  100  has three basic components, a drive motor  120 , an optical pickup unit  130 , and an optical mechanical assembly  140 . The drive motor  120  serves to spin the optical disc  110  at predetermined rates that typically vary from several hundred to several thousand rpm. The optical pickup unit  130  serves to read and write data from and to the optical surface  112  of the optical disc  110 . The optical mechanical assembly  140  serves to move the optical pickup unit  130  in a radial direction  152  relative to the optical disc  110  to predetermined locations relative to the optical disc  110 . 
     The optical pickup unit  130  typically has a laser, not shown, to illuminate the optical surface  112 , an objective lens  132  to focus the laser, and a photodetector, not shown, to translate light to machine-readable data. Other optical components may be located within the optical pickup unit  130  to direct light between the photodetector and the objective lens  132 . Mechanical components may be located in the optical pickup unit  130  and may serve to support the objective lens  132  and to move the objective lens  132  relative to the optical pickup unit  130 . 
     The optical pickup unit  130  emits incident light that is directed through the objective lens  132  and onto the optical surface  112  of the optical disc  110 . The optical pickup unit  130  may, as an example, output approximately 20 milliwatts of coherent light having a wavelength of approximately 790 nanometers. Light is reflected from the optical surface  112  of the optical disc  110  through the objective lens  132  and back to the optical pickup unit  130 . The light reflected from the optical surface  112  of the optical disc  110  varies in intensity wherein the variations are caused by light reflecting from the optical transitions on the optical surface  112  as the optical disc  110  spins. These variations in intensity are representative of the data stored on the optical surface  112 . 
     As the optical disc  110  spins, the mechanical components in the optical pickup unit  130  move the objective lens  132  in a radial direction  152  and a normal direction  150 . Specifically, the optical pickup unit  130  moves the objective lens  132  normal to the optical surface  112  of the optical disc  110  to focus light between the optical surface  112  and the optical pickup unit  130 . This focusing allows a sharp image of the optical transitions on the optical surface  112  to be focused onto the photodetector, which improves the operation of the optical disc drive  100 . The optical pickup unit  130  moves the objective lens  132  radially relative to the optical surface  112  of the optical disc  110  to follow the tracks on the optical disc  110  as the optical disc  110  spins. This movement of the objective lens  132  is very fine because the objective lens  132  has to follow the tracks with a tolerance of approximately one micron in the radial direction  152  as the optical disc  110  spins. The objective lens  132  is generally mounted to the optical pickup unit  130  by the use of very delicate components. This delicate mounting is required in order for the objective lens  132  to move as precisely as is required to follow the tracks on the spinning optical disc  110  and to focus the optical transitions from the spinning optical disc  110  onto the photodetector. 
     As described above, the objective lens  132  has to move very precise distances in very short periods in order to follow the tracks on the optical surface  112 . This makes the optical pickup unit  130  a relatively delicate device. The fragile nature of the optical pickup unit  130  makes it susceptible to failure due to relatively mild shock or vibration. One cause of failure is due to the objective lens  132  becoming dislodged from the structural components in the optical pickup unit  130  that secure the objective lens  132  to the optical pickup unit. Another cause of failure is due to the components that move the objective lens  132  becoming damaged. These problems are more prevalent in optical disc drives used in portable devices because these optical disc drives are typically subjected to greater and more frequent shock and vibration. 
     Additional problems occur in optical disc drives that have the objective lens  132  exposed to a user when an optical disc  110  is being exchanged from the motor  120 . For example, a user may inadvertently touch the objective lens  132 , which may damage the optical pickup unit  130  or contaminate the surface of the objective lens  132  with oils from the user&#39;s skin. In addition, during the exchange of the optical disc  110 , the optical pickup unit  130  becomes exposed to the environment and may become damaged if contaminants from the environment enter it. An exposed optical pickup unit  130  may also be dangerous to the user if the optical pickup unit  130  becomes active in the presence of a user. Laser light is typically emitted by the optical pickup unit, which is a relatively bright and narrow beam of coherent light. This light may pose health risks to the user, such as causing irreversible and permanent damage to the user&#39;s retinas. 
     Therefore, a need exists for a mechanism incorporated into an optical disc drive that will secure the optical pickup unit in a fixed position and out of sight and reach of a user when the optical disc drive is not in use. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is directed toward the operation for an optical disc drive of the type including a moveably mounted optical pickup unit. The method may comprise providing a cover member attached within the optical disc drive, wherein the cover member is non-movable relative to the optical disc drive. The optical disc drive may be deactivated solely by moving the optical pickup unit to a position adjacent the cover member such that the optical pickup unit is protected by the cover member. The optical disc drive may be activated by moving the optical pickup unit away from the cover member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of a side view of a prior optical disc drive. 
     FIG. 2A is a schematic diagram of a side view of an optical disc drive in an operative condition. 
     FIG. 2B is a schematic diagram of a side view of an optical disc drive in a non-operative condition. 
     FIG. 3 is a side perspective view of an optical disc drive having a cover member attached thereto. 
     FIG. 4 is a side view of the cover member of FIG. 3 wherein the cover member has an indented portion. 
     FIG. 5 is a side view of the cover member of FIG. 3 wherein the cover member has an extended portion. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 2A through 5, in general, illustrate a method of operation for an optical disc drive  200  of the type including a movably mounted optical pickup unit  300  therein. The method comprises: providing a cover member  450 ,  490  in association with the optical disc drive  200 ; deactivating the optical disc drive  200  by moving the optical pickup unit  300  to a position adjacent the cover member  450 ,  490  such that the optical pickup unit  300  is protected by the cover member  450 ,  490 ; activating the optical disc drive  200  by moving the optical pickup unit  300  away from the cover member  450 ,  490 . 
     FIGS. 2A through 5 also, in general, illustrate a method of protecting an objective lens  320  of an optical disc drive  200 , wherein the objective lens  320  is movably mounted relative to the optical disc drive  200 . The method comprises: providing a cover member  450 ,  490  in association with the optical disc drive  200 ; providing the objective lens  320  with a first operating position and a second operating position, wherein the objective lens  320  is in the first operating position when the objective lens  320  is located adjacent the cover member  450 ,  490 , and wherein the objective lens  320  is in the second operating position when the objective lens  320  is not located adjacent the cover member  450 ,  490 ; causing the objective lens  320  to move from the second operating position to the first operating position. 
     FIGS. 2A through 5 also, in general, illustrate an optical disc drive  200  comprising: a rotation point  510 ; an optical pickup unit  300  moveable between a first position remote from the rotation point  510  and a second position closer to the rotation point  510 , relative to the first position; a cover member  450 ,  490  located at the first position; wherein the optical disc drive  200  includes: a non-operative condition in which the optical pickup unit  300  is positioned at the first position adjacent the cover member  450 ,  490 ; and an operative condition in which the optical pickup unit  300  is positioned between the first position and the rotation point  510 . 
     Having described the optical disc drive  200  and the components thereof in general, they will now be described in greater detail. Referring to FIGS. 2A and 2B, in summary, the optical disc drive  200  may have an optical pickup unit  300  that is used to read data from an optical disc  100 . The optical disc drive  200  may have a cover member  490  that may serve to protect the optical pickup unit  300  when it is not in use. Specifically, the optical disc drive  200  moves the optical pickup unit  300  between an operative position as illustrated in FIG. 2A and a non-operative position as illustrated in FIG.  2 B. The non-operative position may be a position where the optical pickup unit  300  is covered by the cover member  490  when the optical pickup unit  300  is not in use. The cover member  490  illustrated in FIGS. 2A and 2B is one example of a cover member. Other examples of cover members are illustrated in FIGS. 3 through 5 and are depicted numerically as  450 . 
     Having described the optical disc drive  200  and the components thereof in general, they will now be described in greater detail. A summary description of the optical disc drive  200  is followed by a more detailed description of the optical disc drive  200 . Referring to FIGS. 2A,  2 B, and  3 , in summary, the optical disc drive  200  may have an optical pickup unit  300  that is used to read data from an optical disc  110 . Specifically, the optical pickup unit  300  reads data stored in the form of optical transitions in narrow tracks located on an optical surface  112  of the optical disc  110  as the optical disc  110  spins. The optical pickup unit  300  may emit a narrow beam of light having a specific wavelength that is used to illuminate the optical surface  112 . The light may, as an example, be emitted by a laser. The optical pickup unit  300  receives light reflected from the optical surface  112  and translates the reflected light to machine-readable image data, thus, the optical pickup unit  300  “reads” the data stored on the optical disc  110 . The embodiment of the optical disc drive  200  shown in FIG. 2A is in an active or second operating condition when the optical pickup unit  300  is in a second operating position. The embodiment of the optical disc drive  200  shown in FIG. 2B is in an inactive or first operating condition when the optical pickup unit  300  is in a first operating position. 
     The optical pickup unit  300  may have an objective lens  320 . The objective lens  320  may move in a normal direction  216  and a radial direction  210  relative to the optical pickup unit  300  as the optical pickup unit  300  is reading the data from the optical surface  112 . The movement of the objective lens  320  in the normal direction  216  may serve to focus an image of the optical surface  112  onto optical components located in the optical pickup unit  300 . The movement of the objective lens  320  in the radial direction  210  may serve to precisely follow the tracks on the optical surface  112  as the optical disc  110  spins. The objective lens  320  may only move distances in the order of microns relative to the optical pickup unit  300 . Thus, the mechanisms within the optical pickup unit  300  that move the objective lens  320  tend to be very delicate, making the optical pickup unit  300  a relatively delicate device. 
     The light emitted by the optical pickup unit  300  may pose health risks to the user. For example, the light may damage the user&#39;s retinas, which generally causes permanent and irreversible damage to the user&#39;s vision. A user is exposed to the optical pickup unit  300  when he or she exchanges the optical disc  110 , however, the optical pickup unit  300  is normally deactivated when an optical disc  110  is being exchanged. If, however, the optical pickup unit  300  becomes activated for any reason while the user is exposed to the optical pickup unit  300 , the light may contact the user and endanger the health of the user. 
     As was previously described, a user may be exposed to the optical pickup unit  300  when he or she is exchanging an optical disc  110 . If the user touches the objective lens  320  or causes an object to contact the objective lens  320 , the optical pickup unit  300  may be damaged. For example, oils from the user&#39;s hands may contaminate the objective lens  320 , thereby making the optical pickup unit  300  unable to read the optical surface  112  of the optical disc  110 . In another example, the user may damage the mechanism that moves the objective lens  320  relative to the optical pickup unit  300 , which will render the optical pickup unit  300  and, thus, the optical disc drive  200  inoperable. The optical disc drive  200  may also be rendered inoperable if the optical disc drive  200  is subject to excessive shock or vibration that damages the mechanism that moves the objective lens  320  relative to the optical pickup unit  300 . 
     The optical disc drive  200  described herein overcomes the aforementioned problems by providing a cover member  450 , 490  that protects the optical pickup unit  300  from shock, vibration, and contamination. The cover member  450 , 490  also protects the user from dangerous light emitted by the optical pickup unit  300 . The cover member  450 , 490  may be appropriately shaped so that the optical disc drive  200  may move the optical pickup unit  300  under the cover member  450 , 490  when the optical disc drive  200  is not in use. Locating the optical pickup unit  300  under the cover member  450 , 490  keeps the user from contacting the objective lens  320  and protects the user from being exposed to dangerous light should the optical pickup unit  300  become active. The cover member  450 , 490  may be appropriately shaped so that it secures the objective lens  320  in a fixed position when the optical pickup unit  300  is not in use. Securing the objective lens  320  lessens the likelihood that the optical pickup unit  300  will fail if it is subject to shock or vibration. 
     Having summarily described the optical disc drive  200  with the cover member  450 ,  490  incorporated therein, the optical disc drive  200  will now be described in greater detail including other components that are used by the optical disc drive  200 . The following description describes the cover member  450 , FIG. 3, followed by a brief description of the cover member  490 , FIGS. 2A and 2B. 
     FIGS. 2A and 2B are simplified schematic illustrations depicting some of the components comprising the optical disc drive  200 . The optical disc drive  200  may have a motor  500 , the optical pickup unit  300 , an optical mechanical assembly  400 , and the cover member  450 . Except for the addition of the cover member  450 , the optical disc drive  200  may be similar to optical disc drives as are known in the art. The motor  500  may serve to spin the optical disc  110  at a predetermined rate. The rotation rate of the optical disc  110  typically varies between a few hundred rpm to several thousand rpm. As will be described below, the optical pickup unit  300  reads data from or writes data to the optical disc  110  as it spins. 
     FIG. 3 is a top perspective and more detailed view of the optical disc drive  200 . The optical disc drive  200  of FIG. 3 illustrates a slightly different embodiment of a cover member  450  than was illustrated in FIGS. 2A and 2B. The differences in these embodiments will be described in detail below. For illustration purposes, the optical disc  110 , FIG. 2, is not illustrated in FIG.  3 . The motor  500 , optical pickup unit  300 , optical mechanical assembly  400 , and cover member  490  may be mounted to a chassis  230 . The chassis  230  may have a front side  232 , a rear side  234 , a left side  236 , and a right side  238 . The chassis  230  may have a length  240  extending between the front side  232  and the rear side  234 . The chassis  230  may also have a width  242  extending between the left side  236  and the right side  238 . 
     The optical pickup unit  300  may have a housing  310 . The housing  310  may have a length  312 , e.g., approximately two centimeters, and a width  314 , e.g., approximately 1.5 centimeters. The housing  310  may have a top portion  330  (sometimes referred to herein as a surface) wherein the top portion  330  may have an opening  332 . The optical pickup unit  300  may have an objective lens  320  movably mounted relative to the housing  310 . The objective lens  320  may be situated in the proximity of the opening  332 . A plurality of supports  322  may attach the objective lens  320  to a magnetic actuator  324  wherein the magnetic actuator  324  may serve to move the objective lens  320  relative to the housing  310  in a conventional manner. Specifically, the magnetic actuator  324  may serve to move the objective lens  320  in a radial direction  210  and a normal direction  216 . The radial direction  210  is comprised of a positive radial direction  212  and a negative radial direction  214 . The normal direction  216  is comprised of a positive normal direction  218  and a negative normal direction  220 . As will be described in further detail below, the optical pickup unit  300  may serve to translate data stored on the optical disc to machine-readable data. 
     The magnetic actuator  324  may, as an example, move the objective lens  320  in the normal direction  216  a distance of 0.35 millimeters in either the positive normal direction  218  or the negative normal direction  220  to focus light between the optical disc and the optical pickup unit  300 . The magnetic actuator  324  may also, as an example, move the objective lens  320  a distance of 0.25 millimeters in either the positive radial direction  212  or the negative radial direction  214  to follow the tracks on the optical disc as the optical disc spins. 
     The motor  500  may serve to spin an optical disc in a conventional manner. The motor may have a spindle  510  (sometimes referred to as a rotation point) and a hub  512 . The spindle  510  may serve to center the optical disc on the hub  512 . The hub  512  may have a hub surface  514  that may serve to support the optical disc on a plane as it spins. The motor  500  may serve to spin the spindle  510 , the hub  512  and, thus, the optical disc, at various speeds, e.g., several hundred to several thousand rpm. 
     The optical mechanical assembly  400  may serve to move the optical pickup unit  300  in the radial direction  210  wherein the radial direction  210  is a direction that extends from the spindle  510 . The optical mechanical assembly  400  typically does not have the precision for movement in the radial direction  210  as the magnetic actuator  324  does. Thus, the optical mechanical assembly  400  may serve to move the optical pickup unit  300  to an approximate location relative to an optical disc. The magnetic actuator  324  may then serve to move the objective lens  320  to a precise location relative to the optical disc. 
     The optical mechanical assembly  400  may operate in conjunction with a transport mechanism  410 , a guide mechanism  416 , and a slide mechanism  418 . The transport mechanism  410  may serve as an interface between the optical pickup unit  300  and the optical mechanical assembly  400 . The guide mechanism  416  and the slide mechanism  418  may be affixed to the chassis  230  and may support the optical pickup unit  300 . The guide mechanism  416  and the slide mechanism  418  may be parallel and may also serve to guide the optical pickup unit  300  as it is moved by the optical mechanical assembly  400 . The optical mechanical assembly  400  may, as an example, comprise a conventional servo system, not shown, to move the optical pickup unit  300 . 
     The cover member  450  may be attached to the chassis  230  by conventional means, e.g., rivets, screws, or adhesives. Referring to FIG. 4, the cover member  450  may have a left support portion  452 , a right support portion  454 , a left elevation portion  476 , a right elevation portion  478 , and a top portion  460 . The left support portion  452  and the right support portion  454  may have holes  456 ,  458  respectively. The holes  456 ,  458  may serve to attach the left support portion  452  and the right support portion  454  to the chassis  230 , FIG. 3, in a conventional manner, i.e., screws may pass through the holes  456 ,  458  and the chassis  230 . The left elevation portion  476  and the right elevation portion  478  may serve to elevate the top portion  460  from the left support portion  452  and the right support portion  454 . The top portion  460  may have a lower side  462  that is separated from the left support portion  452  and the right support portion  454  by a distance  464 . As will be described below, the lower side  462  may serve to support the optical pickup unit  300 , FIG. 3, when the optical pickup unit  300  is not in use. 
     The lower side  462  may have a recess  470  located therein. The recess may have a width  472  and a depth  474 . The recess  470  may be lined with a cushion or elastic material  480  having a thickness  482 . The recess  470  may serve to secure the objective lens  320 , FIG. 3, in a fixed location when the optical disc drive  200  is inactive. The cushion material  480  may serve to protect the objective lens  320 , FIG. 3, from being scratched or contaminated when it is held in the fixed location by the recess  470 . 
     Referring again to FIG. 3, the optical disc drive  200  may place the optical pickup unit  300  in two different operating positions. The first operating position of the optical pickup unit  300  is where it is positioned under or adjacent the cover member  450 . In this position, the optical pickup unit  300  and, thus, the optical disc drive  200  are inactive as the optical pickup unit  300  is not able to read data from the optical disc. The second operating position of the optical pickup unit  300  is where it is not positioned adjacent or under the cover member  450 . In this position, the optical pickup unit  300  and, thus, the optical disc drive  200  are active as the optical pickup unit  300  may read data stored on the optical disc. 
     Having described the optical disc drive  200  and the components thereof, the operation of the optical disc drive  200  will now be described. 
     Referring to FIG. 3, when the optical disc drive  200  is in use, an optical disc is located on the hub surface  514  and centered about the spindle  510 . The motor  500  spins the optical disc at a predetermined speed, which may vary from several hundred rpm to several thousand rpm. The optical mechanical assembly  400  moves the optical pickup unit  300  in the positive radial direction  212  from the first operating position to the second operating position where it may read data from the optical disc. 
     The optical disc drive  200  receives instructions to read data from a specific portion of the optical disc. In order to read the data, the optical mechanical assembly  400  determines the present position of the optical pickup unit  300  and calculates how far in either the positive radial direction  212  or the negative radial direction  214  the optical pickup unit  300  must move in order to read the specified data. The optical mechanical assembly  400  in conjunction with the transport mechanism  410  then moves the optical pickup unit  300  on the guide mechanism  416  and the slide mechanism  418  to the position where the optical pickup unit  300  may read the data on the optical disc. The guide mechanism  416  may, as an example, pass through the transport mechanism  410  so as to assure that the transport mechanism  410  moves on an axis defined by the guide mechanism  416 . The slide mechanism  418  may serve as support for the optical pickup unit  300  to assure that the optical pickup unit  300  does not tilt relative to the chassis  230 . 
     When the optical pickup unit  300  is located in the approximate position of the data on the optical disc, the optical pickup unit  300  commences to read data located on the optical disc. The optical pickup unit  300  emits light through the objective lens  320  to illuminate a specific track on the optical disc. Light is reflected from the track, through the objective lens  320  and to a photodetector, not shown, in the optical pickup unit  300  that converts the reflected light to machine-readable data, e.g., digital data. A laser is typically used to generate the light used to illuminate the tracks on the optical disc. The laser may, as an example, emit light having a wavelength of approximately 790 nanometers and a power of approximately 70 milliwatts. The tracks on the optical disc have different reflective areas, sometimes referred to herein as pits and lands. Light reflected from the pits has a different intensity than light reflected from the lands. Binary data may be stored in the tracks on the optical disc by the use of the pits and the lands wherein the pits may represent binary zeros and the lands may represent binary ones. Accordingly, light reflected from a track on the optical disc changes between a high intensity and a low intensity as the optical disc spins. These changes in the intensity of the reflected light are, thus, representative of the data stored on the optical disc. 
     The optical mechanical assembly  400  does not have the precision to guide the objective lens  320  to follow a specific track on the optical disc as the optical disc spins. In order to solve this problem, the optical pickup unit  300  moves the objective lens  320  to the precise track from where the requested data is stored as the optical disc spins. Specifically, the magnetic actuator  324  moves the objective lens  320  in the positive normal direction  218  or the negative normal direction  220  to focus an image of the track onto the above-described photodetector located in the optical pickup unit  300 . The magnetic actuator  324  also moves the objective lens  320  in the positive radial direction  212  or the negative radial direction  214  to follow a specific track as the optical disc spins. The objective lens  320  must constantly move in the radial direction  214  in order to follow the track because the track spirals around the optical disc and will be in constant radial movement relative to the objective lens  320 . The radial movement of the objective lens  320  is very precise as the tracks are separated by a radial difference of approximately 1.6 microns and the optical disc spins at speeds of a few hundred to several thousand rpm. 
     When the optical disc drive  200  is not reading the optical disc, an instruction is transmitted to the optical mechanical assembly  400  to move the optical pickup unit  300  to the first operating positions. The optical mechanical assembly  400  moves the optical pickup unit  300  in the negative radial direction  214  far enough so that the objective lens  320  moves under the cover member  450 . Referring to FIGS. 3 and 4, the objective lens  320  slides into the recess  470  where it is secured in a fixed position by the cushion material  480 . Locating the objective lens  320  under the cover member  450  serves to secure the objective lens  320  in a fixed position, which lessens the likelihood of damage to the optical pickup unit  300  when the optical disc drive  200  is subjected to vibration or shock. This location also serves to protect the optical pickup unit  300  from being contacted by a user. For example, a user is less likely to be able to touch the optical pickup unit  300  or inadvertently contact the optical pickup unit  300  with an optical disc, either of which could damage the optical pickup unit  300 . Locating the objective lens  320  under the cover member  450  also serves to shield a user from the light emitted by the optical pickup unit  300  should the light source, not shown, located in the optical pickup unit  300  become active. 
     Referring to FIGS. 2A,  2 B, and  3 , the cover member  450 ,  490  may be located in the radial direction  210  beyond the optical disc  110 . Accordingly, the optical mechanical assembly  400  may have to be adapted to increase the movement of the optical pickup unit  300  beyond that of conventional optical disc drives so that the optical pickup unit is able to be located under the cover member  450 ,  490 . 
     In one embodiment of the optical disc drive  200 , the surface  330  of the optical pickup unit  300  contacts the lower side  462  of the cover member  450  when the optical pickup unit  300  is located under the cover member  450 . Contacting the surface  330  with the lower side  462  further serves to protect the optical pickup unit  300  from damage as a result of shock or vibration by holding the optical pickup unit  300  in a fixed position. Contacting the surface  330  with the lower side  462  lessens the likelihood that the optical pickup unit  300  will become dislodged from the transport mechanism  410 . It also lessens the likelihood that shock and vibration will cause the optical pickup unit  300  to damage components located in the optical mechanical assembly  400 . 
     The optical pickup unit  300  has been described herein with the objective lens  320  extending in the positive normal direction  218  beyond the surface  330  of the optical pickup unit  300 . In some optical pickup units, the objective lens  320  may be flush with the surface  330  or slightly recessed into the optical pickup unit  300 . An optical disc drive using either of these optical pickup units  300  may use the cover member  450  illustrated in FIG.  5 . The cover member  450  of FIG. 5 is identical to the cover member  450  of FIG. 4, except that it has a cushion material  490  extending from the surface  462  rather than having a recess  470 , FIG.  4 . The cushion material  490  may have a width  492  and may extend a distance  494  from the surface  462 . The width  492  and the distance  494  are appropriately sized to allow the cushion material  490  to fit through the opening  332 , FIG. 3, in the surface  330 . 
     Referring to FIGS. 3 and 5, when the optical pickup unit  300  is moved under the cover member  450 , the cushion material  490  passes through the opening  332  to contact the objective lens  320 . The cushion material  490  secures the objective lens  320  in a fixed position, which as described above, lessens the likelihood that the objective lens  320  will be damaged if the optical disc drive is subjected to shock or vibration. 
     The optical disc drive  200  has been described using embodiments of the cover member  450  as illustrated in FIGS. 4 and 5. These cover members  450  contact the surface  330  of the optical pickup unit  300  and components located on the surface  330 . The optical disc drive  200  illustrated in FIGS. 2A and 2B depicts another embodiment of a cover member  490 . The cover member  490  is c-shaped, thus, the optical pickup unit  300  moves into the cover member  490  rather than under it. Accordingly, the cover member  490  encompass the optical pickup unit  300  and provides additional support. 
     Referring to FIGS. 2A,  2 B, and  3 , in another embodiment of an optical disc drive  200 , the optical mechanical assembly  400  moves the objective lens  320  under the cover member  450 ,  490  every time a user exchanges an optical disc  110 . For example, prior to powering itself down, the optical disc drive  200  may instruct the optical mechanical assembly  400  to move the objective lens  320  from the position shown in FIG. 2A to a position under the cover member  450 ,  490  as shown in FIG.  2 B. 
     Some optical disc drives have an access door that must be opened in order for a user to gain access to the optical disc. In these applications, the optical disc drive may instruct the optical mechanical assembly  400  to move the objective lens  320  under the cover member  450 ,  490  when the user attempts to open the door. In some other optical disc drives the chassis  230  sides out from a housing when a user changes the optical disc, thus, exposing the objective lens  320  to the environment and the user. In these optical disc drives, the optical disc drive may instruct the optical mechanical assembly  400  to move the objective lens  320  under the cover member  450 ,  490  prior to sliding the chassis out of the housing. 
     While an illustrative and presently preferred embodiment of the invention has been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.