The external feedback effect on the relative intensity noise characteristics of 405 nm InAlGaN laser diode has been analyzed taking into account the spontaneous emission noise and the high frequency modulation of the injection current. A Langevin diffusion model was exploited to characterize its relative intensity noise. The spontaneous emission noise components were quantitatively evaluated from the optical gain properties of the InAlGaN multiple quantum well active regions by using the multiband Hamiltonian for the strained wurtzite crystals. The extracted parameters were applied to the rate equations taking into account the external feedback and external current modulation effects. The simulation results were investigated to optimize the relative intensity noise characteristics.
We presented new way of fitting the result of the scalar diffraction simulation to that of the FDTD method by modifying the wall angle of the media to reduce the time for the channel data simulation
A prototype of ultra small optical drive was studied and developed in order to see the feasibility of mobile application, which is targeted to be attachable into the PCMCIA II slot in small mobile devices. A new design and fabrication technology of optical flying head (OFH) for first surface MO recording was studied, and an effective OFH precisely equipped with high NA lens and MO coil was developed based on miniaturization technology. Design consideration of small form factor optical drive is discussed. Some technical issues and barriers in designing and manufacturing the OFH are introduced. Head-disk interface for reliability and flying stability on plastic disk media was tested and evaluated. Basic tracking and read-write performances in a test bed system were tested.
For the application to the 5mm height optical drive, we have developed a small optical pick-up module within its dimension of 3.0×2.0×5.5mm, by integrating refractive and diffractive optical elements with laser diode and photo diodes assembly.
KEYWORDS: Computer programming, Optical recording, Digital video discs, Compact discs, Radon, Computer simulations, Digital electronics, Digital recording, Consumer electronics, Modulation
We will report on new dc-free runlength-limited codes (DCRLL) intended for the next generation of DVD. The efficiency of the newly developed DCRLL schemes is extremely close to the theoretical maximum, and as a result, significant density gains can be obtained with respect to prior art coding schemes.
KEYWORDS: Optical discs, Semiconductor lasers, Signal detection, Objectives, Digital video discs, Modulation, Optical storage, Laser systems engineering, Monochromatic aberrations, Photography
Continuing demands for higher-capacity optical disc storage system become even stronger as High-Definition TV Broadcasting and Internet are creating new needs for data storage. Recently, high density optical disc systems using blue laser diodes have been reported as potential candidates for next generation industry-standard. At ISOM/ODSí '99, we have proposed to reduce substrate thickness to 0.3 mm, and showed its potential advantage by read-out test using blue laser diode. Later, we reported experimental results of read-only and rewritable disc systems based on the 0.3 mm plastic injection-molded substrate. In this paper, we will report on some of the new features of our blue wavelength system as well as the technical progress we have achieved so far.
KEYWORDS: Nonlinear optics, Linear filtering, Optical recording, Performance modeling, Modulation, Systems modeling, Optical engineering, Electronic filtering, Digital video discs, Complex systems
We prepared and tested a disc that has a transparent plastic substrate of 0.3 mm thickness to confirm the readout capability using a blue laser diode. And the test results of injection molding for the plastic substrate of 0.3 mm thickness are shown.
KEYWORDS: Sensors, Signal to noise ratio, Performance modeling, Data modeling, Optical storage, Detection and tracking algorithms, Digital electronics, Electronics, Optical discs, Semiconductor lasers
As linear recording density of optical discs increases, the channel non-linearity grows larger. And narrowing of track pitch also makes the read-out signals affected by large crosstalk from adjacent tracks. These non-linearity and crosstalk degrade the performance of the disc read-out systems. So we need to design equalizers and detecting methods - especially MLSD(Maximum Likelihood Sequence Detector) - considering those deteriorating factors.
As the recording density increases, the linear convolution model, which expresses the time-dependent readout signal as a convolution of unit optical stylus with a data sequence, does not simulate the readout signal well enough to be used for performance analysis.
Rewritable optical disks require higher recording density in order to record HD-Video signal. Improvement in random accessibility is also highly recommended for realizing RTRW (real time recording requirement). In this paper, we propose a new addressing method which employs phase modulated(PM) wobble signal to encode a physical address for land/groove recording. We call this method as address in Phase modulated wobble (APMW). By using proposed new addressing method, we could increase recording density as compared with a pit addressed method such as applied in DVD-RAM and improve random accessibility as compared with that of DVD-RW.
Optical pick-ups offering DVD, CD and CD-R/RW compatibility begin to use non-conventional optical components. Possible influences to HF and servo signals caused from these components are discussed. And the newly developed compatible pick-up is introduced.
A simple model to clearly show the causes of offset in DPD (Differential Phase Detection) signal is suggested. From this model, we can see the offset mechanism in case lens shift and disc tilt occur, respectively. We also suggest the feasibility of using 2-segment DPD. Comparison of 2-seg. DPD with conventional 4-seg. DPD is made.
We have developed several HD-CD players, which can play 2X, 3.3X, and 4.2X higher density than normal disc respectively, to compare cost/performance characteristics.
We suggest a simple model to quantify the crosstalks from adjacent tracks, and show some simulation results which can be used for recording density optimization. It is shown that disc parameters and optical pick-up configuration should be carefully matched with each other to achieve better performance.
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