CN1352454A

CN1352454A - Multistage storage CD read and write system based on phase changing material

Info

Publication number: CN1352454A
Application number: CN 01139829
Authority: CN
Inventors: 徐端颐; 佘鹏; 刘嵘; 雷志军; 齐国生
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2001-11-30
Filing date: 2001-11-30
Publication date: 2002-06-05
Anticipated expiration: 2021-11-30
Also published as: CN1142546C

Abstract

The invention relates to a reading/wriing system for multi-stage optical storage disc. It includes writing light path along longitudinal direction, reading path along transverse direction, a set for detecting phase directly located above spectroscope, and multi-stages optical disc. The writing light path is from writing laser, collimating lens, spectroscope to converging lens. The reading light path is from reading laser, collimating lens, spectroscope, WoIastoh prism, to spectroscope and converging lens in the writing light path. The writing and reading lasers are located on the flocal point of relevant spectroscopes. The direct phase detecting set consists of spectroscope, then in I optical path: 1/4 wae plate, half-wave plate, polarized spectroscope; and in II optical path; middle density filter of reflector, half-wave plate, polarized spectroscope. The end of optical path is a photoelectric detector that receives a beams of light. The invented system provides capacities to realize high density of storage and high data transferring rate with simple structure.

Description

Multistage storage CD read and write system based on phase-change material

Technical field

Multistage storage CD read and write system based on phase-change material belongs to field of optical storage technology.

Background technology

In existing various optical storage systems, all adopt and read reflective light intensity and change the device that reads storing data information, as in digital multi-purpose disk (Digital Versatile Disc-DVD), all adopting single beam serial read-write equipment, ask for an interview index path shown in Figure 1: laser instrument 1 sends single wavelength light beam through 2 one-tenth parallel beams of collimation lens, directive polarization spectroscope 3, through quarter wave plate 4 directive condensers is object lens 5, focuses the beam on the read/write surface for read of CD 6.Folded light beam through read/write surface for read is returned through object lens 5 along former road, quarter wave plate 4 directive polarization spectroscopes 3, and folded light beam focuses the beam on the photodetector 8 through convergent lens 7 and reads.There is following shortcoming in it: (1) data are write and series read-out by the single beam serial, and its read or write speed is difficult to improve; (2) read based on intensity modulation, be subjected to the influence of card flaw or Laser Modulation error easily, its sensitivity is difficult to adapt to the requirement of following optical disc storage to short wavelength, large-numerical aperture and multistage storage development; (3) at present because each recording stack of disc uses different saturating, reflectance, very big for the influence of the light intensity returned, for guaranteeing to obtain enough read output signals, so that recording stack is generally only accomplished is two-layer, so be difficult to improve the storage dimension, its memory capacity also is difficult to improve.

Summary of the invention

The objective of the invention is provides a kind of simple in structure on the basis that makes full use of existing CD storage technique and scale production technology means, can realize the multistage storage CD read and write system based on phase-change material of high storage density and high data transmission rate.

The invention is characterized in that it contains: independently vertically write light path respectively, laterally read light path, be arranged in Direct Phase pick-up unit and the multi-stage optical disk of reading light path spectroscope top; Wherein, write light path and be provided with downwards successively and write laser instrument, collimation lens, spectroscope and condenser, described writing on the focus that laser instrument is positioned at collimation lens; Read light path and be provided with to the right successively and read laser instrument, collimation lens, spectroscope, (Wollaston) Hui Lasidun prism and write spectroscope, condenser in the light path; The Direct Phase pick-up unit contains: be input as the output light of reading optical splitter on the light path and be output as the spectroscope of the last two bundle laser of light path I and II, be configured in the quarter wave plate on the light path I successively backward, half-wave plate and incident angle are 45 ° polarization spectroscope, be configured in the catoptron on the light path II successively, close filter in the reception mirror reflects light, another half-wave plate and another incident angle are 45 ° polarization spectroscope, respectively four photodetectors of the light exported behind optically focused of last two polarization spectroscopes of receiving light path I and II; Multi-stage optical disk is based on the digital phase transformation multi-layer multi-order stored CD of phase-change material.Described multi-stage optical disk is based on 3 layer of 4 exponent number word CD of phase-change material.

Use proof: it has reached intended purposes.

Description of drawings

The reading and writing data index path of Fig. 1 .DVD-ROM.

Fig. 2. the multistage storage CD structural representation.

Fig. 3 .n rank information writes schematic diagram.

Fig. 4. the index path that writes of the present invention.

Fig. 5. the index path of reading of the present invention.

Fig. 6. optical disc surface read the hot spot synoptic diagram.

Fig. 7. the index path of Direct Phase pick-up unit.

Embodiment

Fig. 2 is the structural representation of the multistage storage CD of employing.On the dish 9 substrate 10 is arranged, its first surface is dish outside surface 11, the from then on surperficial incident of laser.Substrate 10 usefulness light transmissive materials are made as also available other polymkeric substance of glass.N recording stack 12 (2≤n≤10) arranged on the substrate 10, and each recording stack has a recording dielectric layer and a wall.The overall height of this n recording stack 12 is no more than the depth of focus of system's object lens, generally about 1 μ m.Reflection horizon 13 is arranged on recording stack 12, and the material in reflection horizon 13 is metals that high reflectance is arranged, as Al, and Au and Ag.Matcoveredn 14 on reflection horizon 13.N=3 in the present embodiment, Al is used in reflection horizon 13.

Fig. 3 has illustrated multistage signal has been written to process on the CD.N layer recording stack 12 is made up of the different material of Writing power threshold values, being positioned at top is the less recording stack of Writing power threshold values, being positioned at following is the recording stack of Writing power threshold values maximum, recording stack only laser power surpass oneself write threshold values the time just can undergo phase transition reaction.As long as accurately the Writing power of control laser just can reach on the n layer, perhaps on n and n-1 layer, or the purpose that on all layers, writes, realize multistage writing.N layer recording materials Writing power threshold values separately is respectively C1～Cn, C1＜C2＜... Cn, establishing Writing power is P.Laser can not write any one deck recording materials when P＜C1, obtains state 1 this moment; When Writing power was C1＜P＜C2, the laser of this moment write the n layer material, obtains state 2; When Writing power is C2＜P＜C3, write top two-layer recording stack i.e. n and n-1 layer, state 3, so analogize, th writing power P＞Cn, then laser can write all recording layers, obtains n+1 kind state, promptly notes the information on n rank.During n=3, can obtain 4 kinds of states.Because laser is after recording stack writes, the measuring point that is written on the recording dielectric layer undergoes phase transition, and causing its folding rate and not being written into the zone has significant change, is written into if any multilayer, and then its refractive index is exactly the accumulation of each layer variations in refractive index.So, can detect with Direct Phase during read output signal and read, its detected signal is proportional to the tangent of the phase difference value between the different recording point, the input sensitivity.Readout laser sends the minimum Writing power threshold values of power ratio recording materials and also wants little laser, laser obtains shaping after awarding mirror by collimation, then by after the Wollaston prism by a branch of two bundles that become, utilize a branch of conduct in the two bundle laser that arrive on the disc to read light, in addition, a branch of light for referencial use after the light beam that comprises phase information returns, obtains read output signal thereby enter the Direct Phase pick-up unit through Amici prism.

Fig. 4 and Fig. 5 are respectively the index paths when writing and reading.See Fig. 4 and Fig. 5, the 1st, write laser instrument, the 2nd, collimation lens, 15 is spectroscope, and 5 is object lens, and 6 is digital phase transformation multi-layer multi-order stored CD, the 16th, three-dimensional working platform, the 17th, Wollaston prism, the 18th, Direct Phase pick-up unit, the 19th, readout laser.Writing laser instrument 1 and be with wavelength is 407nm, and power is the semiconductor laser tube of 30mw, and reading laser instrument 19, to adopt wavelength be 407nm, and power is the semiconductor laser tube of 5mw.The size of used spectroscope 15 is 10mm * 10mm * 10mm, and the diameter of Wollaston prism 17 is 10mm, and the digital aperture of object lens 5 is 0.85, and depth of focus is less than 1 μ m.Write, read on the focus that

laser instrument

1,19 is positioned over collimation lens 2 separately respectively.Because when writing and read, all recording stacks 12 all are within the focal depth range of laser, so do not need complicated automatic focusing device, used focusing and tracking device all adopt mode known in the art.

Ask for an interview Fig. 7, the 15th, spectroscope, the 4th, quarter wave plate, the 20th, half-wave plate, the 3rd, polarization spectroscope, the 5th, object lens, the 21st, catoptron, the 22nd, in close filter, the 8th, the four-quadrant photodiode, its responsiveness is 0.25 a microampere/microwatt.It can make and arrive this interference optical field that installed at 18 o'clock from the CD card and be divided into phase shift and differ successively

4 heavy light, the light intensity of its each heavy light is respectively:

A＝I ₀(1+rcosφ)，B＝I ₀(1-rsinφ)

C＝I ₀(1-rcosφ)，D＝I ₀(1+rsinφ)

Wherein, I ₀Be average intensity, the phasing degree of φ for surveying;

Calculate:

Above-mentioned 4 heavy light fields under r=1 through the output current in 4 four-quadrant photodiodes behind the Direct Phase pick-up unit 18 are:

For photodiode 8a:I ' ₂=I ' ₀(1-cos φ);

For photodiode 8c:I ' ₁=I ' ₀(1+cos φ);

For photodiode 8b:I ' ₄=I ' ₀(1+sin φ);

For photodiode 8d:I ' ₃=I ' ₀(1-sin φ); Wherein, I ' ₀Be average output current, so

Output current according to each photodiode 23～26 can be obtained the φ value.

Under n=3, for 3 layer of 4 exponent number word CD, can obtain 4 and read state, because the phase effect difference that each recording stack is not written into and writes under two kinds of situations reading laser is bigger, so utilize Direct Phase pick-up unit 18 can correspondingly obtain 4 kinds of states: " 00 ", " 01 ", " 10 ", " 11 ", the laser intensity of reading are 1.5mw.The signal that takes out from Direct Phase pick-up unit 18 contains data message, and focusing and tracking information can be respectively applied for data and read and servo link.

This shows that native system has sensitivity, waits advantage easily and fast.

Claims

1, a kind of multistage storage CD read and write system based on phase-change material contains and writes and readout laser, multi-stage optical disk and other annexes, it is characterized in that, it contains: independently vertically write light path respectively, laterally read light path, be arranged in the Direct Phase pick-up unit of reading light path spectroscope top, and multi-stage optical disk; Wherein, write light path and be provided with downwards successively and write laser instrument, collimation lens, spectroscope and condenser be described to be write on the focus that laser instrument is positioned at collimation lens; Read light path and be provided with to the right successively and read laser instrument, collimation lens, spectroscope, (Wollaston) Hui Lasidun prism and write spectroscope, condenser in the light path; The Direct Phase pick-up unit contains: be input as the output light of reading optical splitter on the light path and be output as the spectroscope of the last two bundle laser of light path I and II, be configured in the quarter wave plate on the light path I successively backward, half-wave plate and incident angle are 45 ° polarization spectroscope, be configured in the catoptron on the light path II successively, close filter in the reception mirror reflects light, another half-wave plate and another incident angle are 45 ° polarization spectroscope, respectively four photodetectors of the light exported behind optically focused of last two polarization spectroscopes of receiving light path I and II; Multi-stage optical disk is based on the digital phase transformation multi-layer multi-order stored CD of phase-change material.

2, according to the multistage storage CD read and write system based on phase-change material of claim 1, it is characterized in that: described multi-stage optical disk is based on 3 layer of 4 exponent number word CD of phase-change material.