Abstract:
A system for determining a cleanliness of a lens of an optical disc drive. The system includes a controller configured to control movement of the lens of the optical disc drive between a first position and a second position relative to the optical disc. The first position is located a first distance from an outer surface of the optical disc and corresponds to a position causing the lens to focus light on a data layer of the optical disc. The second position is located a second distance, different than the first distance, from the outer surface and corresponds to a position causing the lens to focus light on the outer surface. The controller is further configured to receive a measurement of light reflected by the optical disc while the lens is in the second position and determine the cleanliness of the lens based on the measurement of the light.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure is a continuation of U.S. patent application Ser. No. 13/670,936 (now U.S. Pat. No. 8,687,472) filed on Nov. 7, 2012, which claims the benefit of U.S. Provisional Application No. 61/557,315, filed on Nov. 8, 2011. The entire disclosures of the applications referenced above are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to the field of optical disc drives. More particularly, the present disclosure relates to contamination of a lens of an optical disc drive. 
     BACKGROUND 
     The lens in an optical disc drive focuses light on the data layer of an optical disc. The reflected light passes through the lens and is sensed by a photo detector, which provides corresponding electronic signals that are processed to provide output signals such as audio and video signals. With time and use, the lens becomes contaminated. For example, dust, hair, lint, smoke residue, and the like (collectively referred to herein as “dust”) accumulates on the lens. This dust causes diffusion of the light, causing less light to reach the photo detector. As a result, the optical disc drive experiences playback problems such as skipping and freezing, as well as reduced quality of the output signals. 
     SUMMARY 
     In general, in one aspect, an embodiment features an apparatus comprising: a light source configured to produce light; a lens configured to focus the light on an optical disc; a photo detector configured to obtain a measurement of the light reflected by the optical disc; and a controller configured to determine a cleanliness of the lens based on the measurement of the light reflected by the optical disc responsive to the lens focusing the light on a surface of the optical disc. 
     Embodiments of the apparatus can include one or more of the following features. In some embodiments, the measurement of the light reflected by the optical disc represents a power of the light reflected by the optical disc. In some embodiments, the controller is further configured to determine the cleanliness of the lens based on a power of the light produced by the light source. 
     In general, in one aspect, an embodiment features a method comprising: causing a lens to focus a light on a surface of an optical disc; obtaining a measurement of the light reflected by the optical disc responsive to the lens focusing the light on the surface of the optical disc; and determining a cleanliness of the lens based on the measurement of the light reflected by the surface of the optical disc. 
     Embodiments of the method can include one or more of the following features. Some embodiments comprise indicating the cleanliness of the lens. 
     In general, in one aspect, an embodiment features a controller configured to perform functions comprising: causing a light source of an optical disc drive to produce light; causing a lens of the optical disc drive to focus the light on a surface of an optical disc; obtaining a measurement of the light reflected by the optical disc responsive to the lens focusing the light on the surface of the optical disc; and determining a cleanliness of the lens based on the measurement of the light reflected by the surface of the optical disc. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a simplified diagram of a portion of an optical disc drive according to one embodiment. 
         FIG. 2  illustrates the spatial relationship between the lens and the optical disc of  FIG. 1  during playback. 
         FIG. 3  illustrates the spatial relationship between the lens and the optical disc of  FIG. 1  during a lens dust measurement according to one embodiment. 
         FIG. 4  shows a dust measurement process for the optical disc drive of  FIG. 1  according to one embodiment. 
     
    
    
     The leading digit(s) of each reference numeral used in this specification indicates the number of the drawing in which the reference numeral first appears. 
     DESCRIPTION 
     Embodiments of the present disclosure provide lens dust detection for optical disc drives. Put another way, these embodiments determine a cleanliness of the lens in an optical disc drive by using a light source of the optical disc drive to detect dust on the lens of the optical disc drive. Moreover, “blue” light, such as that produced by a 450 nm laser, is particularly useful for such lens dust detection. According to the described embodiments, the dust can be detected when the lens is focused on the surface of the disc. In this description, the term “surface” is used to describe the interface between the air and the protective layer of an optical disc. The light reflection from the surface of an optical disc is fairly constant for all discs. And because the amount of reflected light decreases as the amount of dust increases, the amount of reflected light can be used to indicate the amount of dust on the lens. 
       FIG. 1  is a simplified diagram of a portion of an optical disc drive  100  according to one embodiment. Although in the described embodiments the elements of optical disc drive  100  are presented in one arrangement, other embodiments may feature other arrangements. For example, elements optical disc drive  100  can be implemented in hardware, software, or combinations thereof. The described optical disc drives can also be implemented as optical disc burners, optical disc players, and the like. 
     Referring to  FIG. 1 , optical disc drive  100  includes a controller  102 , a pickup head  104 , a focus servo  106 , and a dust indicator  108 . The controller  102  can be implemented as a processor. Processors according to various embodiments can be fabricated as one or more integrated circuits. 
     The pickup head  104  includes a lens  110 , a light source  112 , a photo detector  114 , and a mirror  116 . In operation, the controller  102  generates control signals  118  that cause the focus servo  106  to move the pickup head  104  so that the lens  110  focuses onto an optical disc  128 . The light source  112  produces light  124 . The mirror  116  reflects the light  124  from the light source  112  to the lens  110 , and passes the light  126  reflected from the optical disk  128  to the photo detector  114 . Based on the reflected light  126 , the photo detector  114  provides electronic signals  120  to the controller  102 . The controller  102  processes the electronic signals  120  to provide output signals  122  such as audio and video signals, data signals, and the like. 
     According to one embodiment, the light source  112  is implemented as one or more lasers. The lasers  112  include a “blue” laser such as those used in some DVD players. Note that even though the laser  112  is called “blue,” its color is actually in the violet range. That is, the wavelength of the light produced by the blue laser  112  is approximately 405 nm. The lasers  112  can also include a 650 nm red laser such as those used in some DVD players, a 780 nm infrared laser such as those used in CD players, and the like. 
     The optical disc drive  100  supports an optical disc  128 . The optical disc  128  includes a data layer  130 , a protective layer  132 , and a substrate  134 . The substrate  134  is generally implemented as a polycarbonate layer. In some optical discs  128  such as CDs and DVDs, the protective layer  132  is implemented as a polycarbonate substrate. In other optical discs  128  such as some DVDs and CDs, the protective layer  132  is implemented as a protective coating. The data layer  130  includes pits and lands that represent data. The pits and lands have different reflectivity, which the photo detector  114  employs to generate the electronic signals  120 . 
       FIG. 2  illustrates the spatial relationship between the lens  110  and the optical disc  128  of  FIG. 1  during playback. During playback, the pickup head  104  is positioned so that the lens  110  is focused on the data layer  130  of the optical disc  128 . The controller  102  and the focus servo  106  closely maintain this spatial relationship throughout playback. 
       FIG. 3  illustrates the spatial relationship between the lens  110  and the optical disc  128  of  FIG. 1  during a lens dust measurement according to one embodiment. During the lens dust measurement, the pickup head  104  is positioned so that the lens  110  is focused on the surface  136  of the optical disc  128 . That is, the distance between the center of the lens  110  and the surface  136  of the optical disc  128  is the focal length f of the lens  110 . This spatial relationship can be attained in any manner. 
     In conventional optical disc drives, before playback begins, the pickup head  104  seeks the data layer  130  of the optical disc  128 . During loading of the optical disc  128  into the optical disc drive  100 , the controller  102  causes the focus servo  106  to keep the pickup head  104  far from the optical disc  128  to avoid damage. When playback is initiated, for example when a user pushes the “play” button of the optical disc drive  100 , the seek process begins. In this seek process, the controller  102  causes the focus servo  106  to move the pickup head  104  toward the optical disc  128  until the lens  110  is focused on the data layer  130  of the optical disc  128 . During this movement, the focal point of the lens  110  passes through the surface  136  of the optical disc, as shown in  FIG. 3 . The dust measurement is obtained at that time. Alternatively, the controller  102  can cause the focus servo  106  to move the pickup head  104  to the position of  FIG. 3  at any time in order to obtain the dust measurement. 
       FIG. 4  shows a dust measurement process  400  for the optical disc drive  100  of  FIG. 1  according to one embodiment. Although in the described embodiments the elements of process  400  are presented in one arrangement, other embodiments may feature other arrangements. For example, in various embodiments, some or all of the elements of process  400  can be executed in a different order, concurrently, and the like. Also some elements of process  400  may not be performed, and may not be executed immediately after each other. In addition, some or all of the elements of process  400  can be performed automatically, that is, without human intervention. 
     Referring to  FIG. 4 , at  402 , the light source  112  produces light  124 . At  404 , the mirror  116  reflects the light  124  to the lens  110 . At  406 , the lens  110  focuses the light on the surface  136  of the optical disc  128 . At  408 , the surface  136  of the optical disc  128  reflects the light  124  as reflected light  126 . At  410 , the mirror  116  passes the reflected light  126  to the photo detector  114 . At  412 , the photo detector  114  obtains a measurement (electronic signals  120 ) of the light  126  reflected by the optical disc  128 . At  414 , the controller  102  determines a cleanliness of the lens  110  based on the measurement of the light  126  reflected by the optical disc  128  responsive to the lens  110  focusing the light on the surface of the optical disc  128 . At  416 , the dust indicator  108  indicates the cleanliness of the lens  110 . The dust indicator can be implemented, for example, as an LED on the front panel of the optical disc drive  100 . 
     The controller  102  can determine the cleanliness of the lens  110  based on the reflected light  126  by any means. In some embodiments, the measurement of the light  126  reflected by the optical disc  128  represents the power of the light  126  reflected by the optical disc  128 . In some embodiments, the controller  102  determines the cleanliness of the lens  110  by comparing the power of the light  126  reflected by the optical disc  128  to the power of the light  124  produced by the light source  112 . In some embodiments, the controller  102  determines the cleanliness of the lens  110  based on a calibration value, where the calibration value represents a measurement of the light  126  reflected when the lens  110  is clean. Other embodiments can employ any combination of the above techniques. 
     As mentioned above, different types of optical discs  128  implement the protective layer  132  with different materials. In some embodiments, the dust measurement process accounts for these differences. In such embodiments, the optical disc drive  100  first determines the type of optical disc  128  present in the optical disc drive  100 , for example using conventional techniques. The optical disc drive  100  then modifies the measurement process according to the type of protective layer  132  used in that type of optical disc  128 . For example, the controller  102  can employ a respective reflection coefficient for each type of optical disc  128 . 
     In some embodiments, the optical disc drive  100  is implemented as a stand-alone unit such as an optical disc player or the like. In other embodiments, the optical disc drive  100  is implemented as part of a computer system. For example, the optical disc drive  100  can be installed in a personal computer or the like. In such embodiments, the computer can request the cleanliness of the lens  110 , for example by issuing an ATA Packet Interface (ATAPI) command. The response to the command can be the percentage of light reduction compared with a clean optical disc  128 . 
     Various embodiments of the present disclosure can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof. Embodiments of the present disclosure can be implemented in a computer program product tangibly embodied in a computer-readable storage device for execution by a programmable processor. The described processes can be performed by a programmable processor executing a program of instructions to perform functions by operating on input data and generating output. Embodiments of the present disclosure can be implemented in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, processors receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer includes one or more mass storage devices for storing data files. Such devices include magnetic disks, such as internal hard disks and removable disks, magneto-optical disks; optical disks, and solid-state disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). 
     A number of implementations have been described. Nevertheless, various modifications may be made without departing from the scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.