CDs (compact discs) and DVDs (digital video (or versatile) discs) are optical disk storage media which are used to store large amounts of digital data. A typical CD includes a long spiraling track which originates near the center of the disk, and which spirals toward the edge of the disk. Information is stored by millions of bumps and flat areas (“lands”). Such a track provides for the storage of large amounts of data.
While the above system is effective, improvements in optical data processing are desirable.
While the above system is effective, greater data storage densities, as well as greater data transfer rates, are desirable. An array-based optical head is configured for read and/or write operations to optical media. In one implementation, a polarizing beam splitter is configured to direct laser light to optical media. A photodetector array is configured to receive light modulated by reflection off a checkered pattern on the optical media and to create an output signal corresponding to the modulated light.
The following detailed description refers to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure (Fig.) in which the reference number first appears. Moreover, the same reference numbers are used throughout the drawings to reference like features and components.
An array-based optical head is adapted for use with CDs (compact discs), DVDs (digital video (or versatile) discs) and other types of optical data-storage media. Unlike conventional optical read/write heads which detect or make single marks along an elongated spiraling data path, an implementation of the array-based optical head is configured to read and write checkered optical data patterns.
By reading and writing checkered optical data patterns 102, rather than single marks, the array-based optical head provides greater read/write speeds, as well as greater optical media data density. Read operations are facilitated by photodetector arrays within the array-based optical head, which provide high-resolution optical sensors configured to sense patterns within light modulated by reflection from the checkered optical data patterns. Write operations are facilitated by digital light processor arrays within the array-based optical head, which provide thousands or even millions of micro-mirrors to modulate light according to a pattern, and to enable that pattern to be written to optical media.
A polarizing beam splitter 206 has four optical sides, wherein a first of the four sides the laser 202, a second of the four sides a digital light processor array 208, a third of the four sides an objective lens 210 and a fourth of the four sides a photodetector array 212. In one implementation, the polarizing beam splitter 206 may be configured from two right triangle prisms. A beam splitting face 214 causes light to be redirected (i.e. reflected) at a 90 degree angle when polarization of the light is normal to the plane of incidence. The plane of incidence is the plane of the incident ray normal to the surface of the beam splitter 206. Conversely, where polarization of the light is parallel to the plane of incidence, light passes straight through the polarizing beam splitter 206 without reflection or redirection.
The digital light processor array 208 is an array comprising a plurality of microscopic mirrors (micro-mirrors). In some implementations, thousands, hundreds of thousands or even millions of mirrors are contained within the digital light processor array 208. Each microscopic mirror is individually addressable, and may be instructed to either reflect light back into the polarizing beam splitter 206, or to deflect the light into an absorber. The digital light processor array 208 is therefore useful in modulating light, i.e., the creation of light which casts a checkered pattern upon contact with a surface. For example, the digital light processor array 208 may be installed with respect to the polarizing beam splitter 206 so that light incoming from the beam splitter will strike the each microscopic mirror with approximately the same intensity. However, some micro-mirrors may be directed to reflect the light directly back to the polarizing beam splitter, while some micro-mirrors are directed to deflect the light in a direction that essentially causes the deflected light to disappear from the optical head 200. The light is considered to be modulated because some light is deflected from the system, and some light is returned. Thus, the modulated light creates a checkered pattern upon striking an object, such as the optical media. The operation of each individual mirror is controlled by a digital light processor controller, as will be seen in greater detail below.
The objective lens 210 is configured to focus light exiting the polarizing beam splitter 206 on the optical media 234. It is additionally configured to focus light reflected from the optical media for transmission to the polarizing beam splitter 206.
The photodetector array 212 is configured to detect patterns in the light modulated by reflection off checkered data patterns defined on the optical media. Accordingly, the resolution of the photodetector array 212 is typically greater than or equal to the resolution of the checkered data patterns defined on the optical media.
A first quarter-wave plate 216 is located between the polarizing beam splitter 206 and the digital light processor array 208. The quarter-wave plate 216 has the optical characteristic that the polarity of the waves of the light passing through it in both directions is rotated by 90 degrees (i.e. a quarter of a revolution). Thus, light traveling from the polarizing beam splitter 206 which is reflected off the digital light processor array 208 for return to the polarizing beam splitter 206, passes through the first quarter-wave plate twice. Accordingly, the first quarter-wave plate 216 configures the polarity of the light, so that upon its return to the polarizing beam splitter 206, it will be processed differently. That is, if the light was initially reflected at 90 degrees by the polarizing beam splitter 206 prior to the two passages (i.e., one passage in each direction) through the first quarter-wave plate 216, then the light will pass straight through on its next passage through the polarizing beam splitter 206.
A second quarter-wave plate 218 is located between the polarizing beam splitter 206 and the optical lens 210. The second quarter-wave plate 218 has similar characteristics to the first; i.e., the phase of light making two passes through the plate is rotated 90 degrees. Thus, light passing from the polarizing beam splitter 206 which is reflected off the optical media and back into the polarizing beam splitter 206 passes through the second quarter-wave plate 218 twice. Accordingly, the quarter-wave plate 218 configures the polarity of the light, so that upon its return to the polarizing beam splitter 206, it will be processed differently. That is, if the light passed straight through the polarizing beam splitter 206 prior to the passes through the second quarter-wave plate 218, then the light will be reflected at 90 degrees on its next passage through the polarizing beam splitter 206.
Referring to
The reflected light 222 exiting the polarizing beam splitter 206 passes through a quarter-wave plate 216, which rotates the polarity of the light 222 by 90 degrees. The rotated light 224 then reflects off the micro-mirrors of the digital light processor array 208. The digital signal processor array 208 is configured to substantially reflect light during a read operation, and to modulate the light during a write operation using various micro-mirror pattern settings which correspond to data to be written.
During the read operation, the light 224 is reflected by substantially all of the micro-mirrors of the digital light processor array 208. The reflected 226 light passes through the quarter-wave plate 216 where the polarity of the light is rotated by another 90 degrees. The rotated light 228 then passes into the polarizing beam splitter 206. Because the light has twice passed through the quarter-wave plate 216, the light 230 passes straight through the polarizing beam splitter 206 to the second quarter-wave plate 218, where the polarity is again rotated 90 degrees. The rotated light 232 is then focused by the objective lens 210 onto the optical media 234.
The optical media 234 defines checkered data patterns (i.e., arrays of marks, such as bumps of lands defined on the optical media), such as the example shown in
During a write operation, the light 226 is reflected by the digital light processor array 208 from a pattern of micro-mirrors which depends on the data to be written. The digital light processor array 208 is configured in a manner wherein the angle of orientation of each individual mirror contained within the array can be individually controlled. That is, depending on the data to be written, the digital light processor array controller 404 (
A digital light processor array controller 404 is configured to control the operation of the digital light processor array 408. In particular, the digital light processor array controller 404 processes the incoming data, which is to be written to the optical media, and sends signals representing data appropriate to configuring the micro-mirrors of the digital light processor array 208. The digital light processor array 208, upon receipt of a signal from the digital light processor array controller 404, orients each mirror according to information contained within the signal. By orienting the mirrors according to the signal, light is appropriately reflected by the digital light processor array 208. In a write operation, the digital light processor array controller 404 causes selected reflective elements within the digital light processor array 208 to reflect light according to data received by the controller 404 (i.e., to modulate the light). In contrast, in most embodiments, all the mirrors are oriented to reflect light in a read operation.
A photodetector array controller 406 is configured to interpret signals generated by the photodetector array controller 406 to produce data corresponding to the data read from the optical media 234.
At block 504, modulated laser pulses reflected off the checkered optical data patterns are received, such as by a photodetector array 212. Reception of the modulated laser pulses may be made according to the example illustrated by blocks 506-508. At block 506, modulated laser pulses are passed through a polarizing beam splitter 106. Referring briefly to
At block 510, the modulated laser pulses are decoded into data signals. This is typically performed by the array-based optical head controller 400, such as by the photodetector array controller 406. This may be performed as seen in the example of blocks 512-514. At block 512, patterns within the checkered optical data patterns 102 (
Thus, in a read operation, a pulse of laser light is reflected off checkered optical data patterns defined on optical media. Accordingly, the laser pulse is thereby modulated to include information based on the checkered data patterns. Typically, the pulse is directed through a polarizing beam splitter and terminates in a photodetector array. The photodetector array is configured to decode the modulated light, thereby obtaining the read data.
At block 606, the laser pulses are modulated according to the checkered data pattern to be written to the optical media. This may be performed using hardware similar to that seen in
Thus, in a write operation, a pulse of laser light is reflected off a digital light processor array prior to “burning” data onto the optical media. Specific settings applied to the micro-mirrors within the digital light processor result in modulation of the laser pulse to include information which will result in formation of checkered data patterns on the optical media consistent with the data to be written to the optical media.
Although the above disclosure has been described in language specific to structural features and/or methodological steps, it is to be understood that the appended claims are not limited to the specific features or steps described. Rather, the specific features and steps are exemplary forms of implementing this disclosure. For example, while actions described in blocks of the flow diagrams may be performed in parallel with actions described in other blocks, the actions may occur in an alternate order, or may be distributed in a manner which associates actions with more than one other block. And further, while elements of the methods disclosed are intended to be performed in any desired manner, it is anticipated that computer- and/or processor-readable instructions, performed by a computer or by a processor, typically located within the array-based optical disc drive will be utilized. While a computer- or processor-readable media could be utilized, such as a ROM (read only memory), disc or CD-ROM, an application specific integrated circuit (ASIC), gate array or similar hardware structure, could be substituted.
This patent application is related to U.S. patent application Ser. No. ______, titled “Array-Based Optical Storage”, filed on ______, commonly assigned herewith, and hereby incorporated by reference.