Multilevel storage is the easiest two-dimensional storage technology. On the basis of recording and read-out optical
system of Digital Versatile Disc (DVD), by the method of multilevel run-length coding, the storage capacity can be
increased by 60 percent of DVD9's, reaching 14 Giga Bytes.
In order to meet the requirement of a 10-4 raw Bit Error Rate (BER) of data readout, this paper presents a method of
multilevel run-length coding with changeable level numbers. This method can take advantage of run-length redundancy
to the utmost and reduce Inter-Symbol Interference (ISI) caused by multilevel run-length. Multilevel run-length coding
uses the method of two steps modulation. This paper introduces a coding method of DK (1, 9) and R=1 code rate.
Realized by Pulse Width Modulation, multilevel run-length modulation coding with changeable level has good
symmetry. Its readout characteristics are the same as that of DVD with normal run-length modulation, therefore the
servo control system needn't be changed. Also the signal can be recognized in two aspects respectively, run-length and
level. In the sample disc, average raw BER in the two aspects is less than 10-3.
Multilevel run-length modulation coding could be applied in various systems of run-length modulation coding. On the
basis of the structure and characteristics of the primitive system, the comprehensive efficiency of coding could be
increased by 33 to 50 percent.
During the design process of Blu-ray Disc Optical Pick-Up (BD OPU), the optical system design plays a significant role,
and the collimator lens design is especially important. According to the PW optical design formulas, this paper
calculates the initial parameters of collimator lens. It chooses the triplet type collimator lens instead of aspheric lens to
design in order to reduce the manufacture difficulty according to the real situation in China. And then based on the
initial parameters of collimator lens, the paper optimizes the triplet collimator lens to reach a good quality effect of
parallel beam. At last it puts these design data into manufacture and adjusts the distance between the LD and the
collimator lens by using the sleeve mechanism structure to see the real effect of collimating. Finally the assembly
experiment of whole BD OPU validates these design that it can be used in BD OPU very well.
Nowadays, OMNERC research group is going to advance the capacity to 15GB by reducing the 3T pit length and
increasing the level of long pit based on the signal waveform modulation (SWM) ML recording technology. In order to
prove this method is realizable, this paper proposes the restriction points of consideration to reduce the minimum pit
length which influence the basic specification design of multi-level disk and the difficulty of the following signal
processing. Firstly the restriction of optical pick-up resolution is considered. Secondly, the restriction caused by read-out
channel is discussed in the paper. At the same time as write strategy has its limit based on the previous research, this
paper finally discuss the influence caused by minimize shortest pit length for level design of long length pit.
In Blu-ray Disc Optical Pick-up, the collimating and beam shaping play a significant role for laser beam process. So this
paper firstly gives out a collimating and beam shaping system according to China manufacture situation. And then based
on Laser Optics and Fourier Optics, this paper improves the calculation method of energy coupling efficiency for
collimator lens. At last, it builds a simple Interference Instrument which is used for adjusting the collimator lens and
beam shaper. This apparatus is built based on the theory of interference theory. The simplest example of an
electromagnetic wave is the plane wave. The plane wave is produced by a monochromatic point source at infinity and is
approximated by a collimated light source. Here the paper uses this Interference Instrument to assemble the collimator
lens with laser diode and check the quality of the beam shaping. Meanwhile this collimating and beam shaping system
can be produced easily in China, as it is suitable for Chinese optical element manufacture skill lever and can be precise
assembled by using simple instruments. So it will make that producing BD OPU in China with a lower cost comes true.
It is well known that the optical pick-up (OPU) plays a very important role in optical storage system. And the quality of OPU can be measured by the characteristics of OPU read-out spot for high density optical storage. Therefore this paper mainly designs an OPU model for high density optical storage to study the characteristics of OPU read-out spot. Firstly it analyses the optical read-out principle in OPU and contrives an optical read-out system based on the hereinbefore theory. In this step it chiefly designs the grating, splitter, collimator lens and objective lens. Secondly based on the aberrations analysis and theory involved by the splitter, the collimator lens and the optical lens, the paper uses the software CODE V to calculate the aberrations and to optimize the optical read-out system. Then the author can receive an ideal OPU read-out spot for high density optical storage and obtain the characteristics of the ideal OPU read-out spot. At the same time this paper analyses some influence factors which can directly affect the characteristics of the OPU read-out spot. Thirdly according to the up data the author practically manufactures a real optical pick-up to validate the hereinbefore designed optical read-out system. And it uses the Optical Spot Analyzer to get the image of the read-out spot. Comparing the ideal image to the actual image of the designed optical read-out system, the author finds out that the upwards analyses and design is suitable for high density storage and can be used in the actual production. And the author also receives the conclusion that the mostly influences on characteristics of OPU read-out spot for high density optical storage factors is not only the process of designing the grating, splitter, collimator lens and objective lens, but also the assembling work precision
The evaluation and adjustment for characteristic parameters of DVD traverses is the key in the batch production. This paper classifies the parameters and proposes a particular method which possesses the special servo combined with the commercial servo, damping detecting and obliquity detecting, and then constructs an evaluation and adjustment system for parameters of DVD traverses and introduces the economy structure of hardware with module functions and difficulties of software design.
This paper is concerned with enhancing the accuracy of the coordinate measurement system by compensating the Abbe error in real-time through combined gratings. This research is carried out on a 2D measuring system with a maximum moving range of 200mm X 100mm. According to its structure, a mathematical model using the rigid body assumption is deduced and altogether five metrology gratings are installed along two moving axes to compensate three angel errors according to this model. A special grating subdividing system is designed to realize 200 times subdivision for each of the five gratings. Experiment shows that this system can largely raise the accuracy of the coordinate measurement device. Besides, this research is also very valuable in the upgrading of machine tools.