WO2002019255A1

WO2002019255A1 - Multilayer fluorescent optical medium, method and apparatus for high- speed recording

Info

Publication number: WO2002019255A1
Application number: PCT/US2001/026404
Authority: WO
Inventors: Vladimir Schwartz; Anatoly Dovgan; Jacob Malkin; Eugene Kapinus; Mark Alperovich; Eugene Levich; Boris Chernobrod
Original assignee: Trid Store Ip Llc
Priority date: 2000-08-25
Filing date: 2001-08-24
Publication date: 2002-03-07
Also published as: AU2001286693A1

Abstract

A multi-layer medium (6) for optical memory recording (such as WORM) has photosensitive layers with fluorescent marks. The medium has a transparent substrate and multiple bonded information layers, spatially divided by dye polymer layers and assembled using adhesives. Information is stored as marks on a thin photosensitive layer. The reading and writing having a laser source (1) emitting a laser beam, a holographic or diffraction element (3), and an optical device (4) for splitting the laser beam. The laser beams are positioned using a tracking method referenced to a wobbling groove at the boundary of the information field and the information can be recorded in parallel with multiple beams.

Description

MULTILAYER FLUORESCENT OPTICAL MEDIUM, METHOD AND APPARATUS FOR HIGH-SPEED RECORDING Reference to Related Application

The present application claims the benefit of U.S. Provisional Application No. 60/227,849, filed August 25, 2000, whose disclosure is hereby incorporated by reference in its entirety into the present disclosure. Field of the Invention

The present invention is directed to the recording of digital or analog information and more particularly to the high-speed recording of such information on ROM (read-only memory) or WORM (write once, read many) media. Description of Related Art

The use of photosensitive fluorescent materials to record information is known, for example, from U.S. Provisional Application No. 60/208,505, filed June 2, 2000, and having inventors in common with the present application. The disclosure of that application is hereby incorporated by reference in its entirety into the present disclosure. There were three suggested types of photosensitive compounds, each with a sharp threshold of phase transition.

The first was a two-layer system with a fluorescent dye in the first film and a mixture of quencher and absorber in the second layer. During illumination by laser light, the second layer absorbs the light and is melted. The quencher diffuses into the fluorescent layer and provides efficient spot bleaching

The second involved a photo-induced thermal activation of a chain reaction in so-called "energetic" materials, followed by the generation of radicals that destroy the fluorescent response of a dye polymer to create marks. The third involved a photo-induced thermal dissociation of cyanine dye utilized as efficient quencher of fluorescence in a compound system of fluorescent and cyanine dyes to create marks.

However, it would be desirable to incorporate such techmques into a system providing high capacity and high recording speed.

Summary of the Invention

It will be readily apparent from the above that a need exists in the art to record information at high speed and high capacity. It is therefore a primary object of the invention to incorporate fluorescent optical storage techniques into a high-speed, high-capacity recording system.

It is another object of the invention to do so for the recording of ROM or WORM media.

To achieve the above and other objects, the present invention is directed to a technique using a multi-layer medium for optical memory recording (such as WORM) using photosensitive layers with fluorescent marks. The medium has a transparent substrate and multiple bonded information layers, spatially divided by dye polymer layers and assembled using adhesives. Information is stored as marks on a thin photosensitive layer. The reading and writing laser beam is positioned using a tracking method referenced to a wobbling groove at the boundary of the information field. A high recording speed is enabled by efficient, fast phase transition and by multi-laser beam parallel recording.

Brief Description of the Drawings

A preferred embodiment of the present invention will be set forth in detail with reference to the drawings, in which:

Fig. 1 shows a cross-sectional view of a portion of an information recording medium for use with the present invention; and

Fig. 2 shows a schematic diagram of an optical device for use with the medium of Fig. 1.

Detailed Description of the Preferred Embodiment

A preferred embodiment of the present invention will be set forth in detail with reference to the drawings, in which like reference numerals refer to like elements throughout. Fig. 1 shows a multi-layer WORM disc 100 having a substrate 100 and a plurality of dual compound layers 103, held together by adhesive layers 104. Each dual compound layer 103 includes a first component layer 106 of a solid solution of fluorescent dye-polymer and a second component layer 108 of a mixed solution of quencher and absorber creating a polymer compound. In the case in which the medium 100 is a disc, each dual compound layer 103 also has at least one circular wobble groove 110 imprinted thereon, whose use will be explained below.

The polymer compound of the second component layer 108 has a lower inciting temperature than the first fluorescent component layer 106. Recording and reading can thus be realized by using the same laser or two different lasers with different wavelengths. The data recording time is given by the expression:

t = dT*C*m*N/(P*a), where dT is the difference in temperature, C is the coefficient of thermo-capacity, m is the mass of a single information mark volume, N is the number of layers, P is the focusing power, and a is the absorption coefficient. For dT = 200 K, C = 1.7 J/g, m =

1.25 x 10^"14 g, P = 50 mW, and a = 0.1, the above expression gives t - 53 min for

writing 5 GB of digital data. In case of parallel recording, by using 20 laser beams, the recording time will be t = 2.65 min.

These estimations show that the process of parallel recording could be considered as an efficient method of ROM (read only memory) production. The method includes a process of manufacturing multi-layer dual compound media assembled on an optically transparent substrate, as described above with reference to Fig. 1. To form a multi-beam structure from a single laser beam, the optical system 200 of Fig. 2 is used. In that system 200, a laser 202 emits a light beam LI, which passes through a telescope optical system 204, a holographic or diffractive optical element 206, a beam splitter 208, and an objective lens 210 onto a recording medium 100. The holographic or diffractive optical element 206 breaks up the light beam LI so that multiple light beams L2 are incident on the medium 100. The reflected light L3 passes through the objective lens 210 and is reflected by the beam splitter 208 through a collimating lens system 212 onto a photodetector system 214. The multiple light beams L2 can be modulated in any of several suitable ways, which are known in the art.

The system 200 allows the use of one or several side beams for auto-focusing and auto-tracking systems. To enable tracking, each layer has one or several wobble grooves in the information field, which are utilized by a laser beam servo-system for control of data mark track pitch. The remaining part of the information field is without any geometrical features or marks. The auto-focusing is provided by a servo- system that utilizes the wobble groove principle and a fluorescence signal from a certain recording spot. The photodetector system 214 has a single or multi-section avalanche diode. In another method, an auto-focusing system uses the astigmatic principle and a multi-section PIN diode matrix. Focusing and tracking techniques are well known in the art of optical information storage and retrieval, e.g., with regard to known CD and CD-ROM reading systems, and therefore will not be explained in further detail here.

In a particular media production method, multiple optical plastic films are coated with the above described fluorescent dye polymer and dual compound quencher layer. Next, a plurality of such films are bonded together by using an optically clear adhesive substance. The resulting multi-layer film structure may be collected in rolls or otherwise. The multi-layer film structure is then cut or shaped as needed for various optical recording devices. In the case of rotating media such as discs, each layer is centrally imprinted with at least one circular wobble groove to enable laser beam tracking during data writing and reading.

After the creation of the multilayer film structure, data are written onto each film layer with the use of multiple laser beams to bleach out a fluorescent effect in a pattern of microscopic fluorescing and non-fluorescing marks representing digital or analog data. The resulting marks can be read as digital or analog information in player/reader systems. If fluorescent dye polymers with different colors are used on adjacent film layers, reading and writing can be done on multiple layers simultaneously.

While a preferred embodiment and various modifications have been set forth above, those skilled in the art who have reviewed the present disclosure will readily appreciate that other embodiments can be realized within the scope of the present invention. For example, the numerical values taught above are illustrative rather than limiting. Therefore, the present invention should be construed as limited only by the appended claims.

Claims

We claim:

1. A fluorescent medium for recording information, the medium comprising:

(a) a substrate;

(b) a plurality of compound layers, each of the compound layers comprising a fluorescent dye and a quencher for the fluorescent dye; and

(c) a plurality of adhesive layers for adhering the plurality of dual compound layers to one another and to the substrate.

2. The medium of claim 1, wherein each of the plurality of compound layers comprises: (i) a first component layer of a solid solution of fluorescent dye-polymer; and

(ii) a second component layer of a mixed solution of the quencher and an absorber creating a polymer compound.

3. The medium of claim 1, wherein the medium is formed as a disc, and wherein each of the plurality of compound layers has at least one circular wobble groove for tracking.

4. The medium of claim 1, wherein at least two adjacent ones of the plurality of compound layers have fluorescent dyes of different fluorescent wavelengths.

5. A method for recording information, the method comprising:

(a) providing a medium having a plurality of compound layers, each of the compound layers comprising a fluorescent dye and a quencher for the fluorescent dye;

(b) providing a plurality of laser beams for recording the information in parallel; and

(c) directing the plurality of laser beams onto the medium to cause phase transitions in the medium to record the information.

6. The method of claim 5, wherein each of the plurality of compound layers comprises:

(i) a first component layer of a solid solution of fluorescent dye-polymer; and (ii) a second component layer of a mixed solution of the quencher and an absorber creating a polymer compound.

7. The method of claim 5, wherein step (b) comprises splitting a single laser beam by use of a holographic or diffractive optical element.

8. The method of claim 5, wherein the medium has at least one wobbling groove, and wherein step (c) comprises tracking the plurality of laser beams on the medium by use of the at least one wobbling groove.

9. The method of claim 5, wherein the information is written in digital form.

10. The method of claim 5, wherein the information is written in analog form.

11. The method of claim 5, wherein the medium is a ROM medium.

12. The method of claim 5, wherein the medium is a WORM medium.

13. An apparatus for writing information in parallel onto a medium, the apparatus comprising:

(a) a source of a plurality of laser beams;

(b) a light detecting system for receiving reflected light from the medium and for determining tracking information from the reflected light; and (c) an optical system for directing the plurality of laser beams onto the medium and for directing the reflected light onto the light detecting system.

14. The apparatus of claim 13, wherein the source comprises: a laser; and a holographic or optical element for breaking light from the laser into the plurality of laser beams.

15. The apparatus of claim 13, wherein the optical system comprises an objective lens for focusing the plurality of laser beams onto the medium.

16. The apparatus of claim 13, wherein the optical system comprises a beam splitter for separating the plurality of laser beams from the reflected light and for directing the reflected light onto the light detecting system.