Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-11-12
2001-03-27
Edun, Muhammad (Department: 2753)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S116000, C369S047360, C369S044120
Reexamination Certificate
active
06208609
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to retrieving encoded information from an optical disk. It is particularly related to methods and apparatus for an information pick-up system within an optical disk reader head. It is also particularly related to methods and apparatus for detecting and compensating for tracking, focusing, and magnification errors. The invention is still more particularly related to the application of surface-emitting semiconductor microlaser and semiconductor photo detectors in miniaturization of data pick-up and servo control methods and apparatus in optical disk reader heads. It is also particularly related to providing mobility and thus capacity of adjustment to data pick-up, tracking, focusing, and magnification servo systems. It is also particularly related to the application of molded aspheric bilens in optical reader heads. The invention is further particularly related to reading single track and simultaneously reading multiple tracks of data on an optical disk to provide the optical reader with very high data transfer rates.
BACKGROUND OF THE INVENTION
Optical disks have become widely used in part due to their relatively high storage capacity. Whereas a 3½-inch floppy disk stores merely 1.44 MB (megabytes) of data, a 12-cm compact optical disk can store upwards of 650 MB. The increased track density and the decreased pit size on a same size DVD-ROM provides 4.7 GB (gigabytes) of memory capacity. Optical disks are therefore increasingly becoming the most popular portable media for audio/video entertainment and data storage. Future development promises to bring increased memory capacity, such as double-sided, dual layer high definition (HD) DVD-ROM of 30 GB, and much shorter seek and access times to optical disk technology. Organizing optical disks in a jukebox that contains dozens to hundreds of disks and several disk drives can form very large archives, thus substantially increasing the value of optical disks as a versatile removable data storage media.
The market demand for optical disk drives is phenomenal. Audio CD players have become a necessary component in home entertainment appliances. The installed base of CD-ROM drives, now an estimated 195 million plus worldwide, will peak after the millennium. DVD, promising a new level of quality and convenience for movies, music, multimedia and interactive software, and digital analysis and storage, will inevitably revolutionize the way we view entertainment and gather information, and are estimated to replace the CD and dominate the optical disk market by the year 2002.
Increased availability of CD and DVD products, coupled with the availability of increasingly faster microprocessors, has created an enormous need for ever-faster optical disk drives. As a result, disk drives capable of operating at multiplied speeds of standard drives are becoming available. While the very first CD-ROM drive, introduced in 1991, operated at 1× speed, the performance of CD-ROM drives has leapfrogged from 8× to 24× speeds over the past year (1997), defying everything from overheating to increased vibration. The notion that faster is better has flattened the CD-ROM drive development cycle to approximately six months. The fastest drives available at present operate at 40×.
Currently available techniques for designing such high speed drives is limited to increasing the rotating speed of the optical disk to reduce data access latency and increase data transfer rate. Unfortunately, a main drawback of using constant angular velocity instead of constant linear velocity is that the data transfer rate across the entire disk is not uniform. Take, for instance, a CD-ROM specified as 24× by the manufacturer. While the data on the outside track may indeed be transferred at 24×, the rate on the inner tracks, where most of today's software is located, is only typically between 12× and 16×. It is unlikely that the manufacturers will be able to deliver reliable drives at or higher than 32×. The very high spindle speed compromises the performance reliability of such optical disk drives by creating additional cooling requirements and various stability issues.
To accelerate the data transfer rate further, another obvious alternative to increasing the disk angular velocity is by reading multiple data tracks simultaneously. Several patents have disclosed attempts to accomplish such a goal. U.S. Pat. No. 4,094,010 to R. Pepperl et al. describes a multi-channel optical disk storage system wherein a single beam is split into several read beams by using a series of partially transmitting beam splitters. In such a scheme, all the different optical elements must be aligned precisely relative to each other to achieve the highest packing density while preventing cross talk between the multiple beams or focused beam spots. Optical alignment is further complicated by thermal drifts, and the adjustment process can be tedious and time consuming. This need and the technical difficulties of achieving stringent optical alignment will inevitably slow down on the data transfer rate, thereby defining the purpose of using a multi-beam configuration.
U.S. Pat. No. 4,074,085 to J. T. Russell describes another multi-beam scheme, in which multiple illumination sources are applied to provide a plurality of record/read beams. The need for optical alignment as stated above imposes similar problems in this design. U.S. Pat. No. 4,449,212 to C. W. Reno discloses an attempt to use multiple beams split from the output of a single laser to retrieve data. The beams are independently modulated by an acousto-optic device to record and playback data simultaneously. One skilled in the art will note that the extra device will inevitably complicate the servo system and increase the volume of the embodiment. U.S. Pat. No. 5,619,487 to T. Tanabe, et al. submits an ingenious proposal for two beams to read three tracks, but the sequential integration of the read information along the track is in practice difficult to accomplish.
Alternatively, U.S. Pat. No. 5,426,623 to A. Alon, et al. describes a broad beam illumination approach to multi-track reading. In this case, a static illumination/detection section provides a broad incoherent laser beam through a movable optical head section to illuminate several tracks at once. The reflected beam is directed onto a pixel array on the imaging detector. Unfortunately, incoherent light is very disadvantageous when used in CD-ROM pick-up systems. One of the main disadvantages of this broad beam design is that it requires high-energy output of the initial laser beam, risking thermal degradation of the optical disk surface and adding further cooling requirements. The incoherency of the light reduces image contrast provided by interference effect. The broad area of reflected disk image makes the algorithm for detector array pixel analysis extremely complicated and potentially inaccurate or unreliable.
In yet another design described in U.S. Pat. No. 5,729,512 to A. Alon, a multi-beam approach is proposed. A diffraction grating splits a single laser beam into seven evenly spaced and discrete beams to read data from seven adjacent tracks. The central beam is responsible for focusing and tracking. Seven separate optical pickups read the reflected beams and pass the signals through an integrated circuitry that multiplexes the data while performing focusing and tracking error calculations and corrections. Current commercially available multi-beam CD-ROM drives operate at 40×, offering a maximum data transfer rate of 6.0 MB/sec. Concomitantly, the ceiling of laser output energy destines the split beams at the border to be low, thus compromising the accuracy and reliability of the reading and complicating the signal analysis system. The same problems also limit maximum number of split beams (currently at seven) for reading even greater number of tracks at the same time. Additional optical elements required by the device further compound the bulkiness of the p
Hang Zhigiang
Lazarev Victor
Edun Muhammad
New Dimension Research & Instrument, Inc.
O'Connell Law Firm
LandOfFree
Optical system with interactive data capability does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical system with interactive data capability, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical system with interactive data capability will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453645