DE19712573A1 - Reading and writing of data into optical disc having two layers - Google Patents

Abstract

The reading and writing process is applied to an optical memory material which is in the form of two layers (4,5) from which information can written and read with the use of a single laser wavelength. The system has two laser diodes (6,7) with outputs focussed (8,9) onto prisms (10) and then to be focussed by an optical system (13,14) onto the two recording levels in the disc. Signals are reflected back to a beam splitter (18) to be received by detector elements.

Description

The invention relates to methods and devices for reading optical storage media with in two superimposed Information carrier layers located, for information storage serving, essentially parallel Traces, the upper information carrier layer partially trans is parent.

Optical storage media, in particular CD, CD-ROM, WORM-CD and MOD, have been known for some time (Laser Focus World, September 1995, pp. 103-111). Compared to other storage media, they have the particular advantage of a high storage density. Information can be stored on compact discs and similar optical storage media through a sequence of depressions within an information carrier layer. These recesses (pits) are arranged in a spiral from inside to outside tracks. Adjacent tracks, which are separated from one another by means of a continuous groove, run essentially parallel to one another. In the case of the WORM CD, who produces the pits by the focus of a laser beam on the in the scanned track of the information carrier layer causes a material removal in places via a modulated intensity. In magneto-optical SpeI chern, for. B. MOD, the information is stored on the traces of the information carrier layer in points with a certain magnetic orientation. To describe the MOD, the ferromagnetic information carrier layer is selectively heated by laser radiation up to the Curie temperature, in order to then set a defined magnetization with an external magnetic field. In the methods described, a laser diode is generally used as the laser source, the radiation of which is first brought into a parallel beam by means of a collimator lens and then brought to focus on a track via a memory focusing lens. For focus tracking, the radiation reflected from the storage medium and returned by the storage focusing optics is directed into an evaluation arm and brought onto a photodiode or a photodiode array. Because of the related prior art, reference is made, for example, to EP 0 559 435 A1 (description of FIG. 11). In order to increase the yield of the radiation reaching the evaluation arm and to avoid optical feedback, a polarizing coupling beam splitter is usually placed in the beam path between the collimator and the storage focusing lens, and a / 4 plate is placed between the coupling beam splitter and the storage focusing lens (Laser Focus World, September 1995, pp. 103-111). In order to be able to move the focus of the laser radiation used over the entire working range of the optical storage medium, the storage focusing optics are located in a movable reading head, the radiation being fed to the storage focusing optics via a deflection mirror.

The same can be used to read the described storage medium optical structure can be used. However, then with one lower laser power can be worked. The on the op information stored on the storage medium is won by the beam reflected back from the storage medium development in the evaluation arm of a photodiode or a photodiode array ray is fed. It can be the same photodiode (or array) act, which also regulate the focus leadership is used.

To increase the writing and reading speed, it is be knows, at the same time several tracks with the laser radiation act upon. From DE 26 34 243 it is known that Light from a laser via a beam splitter in two parts to split beams, each by a modulator for the radiation intensity can be managed. The partial beams are spaced apart and not completely parallel a deflecting mirror and then onto the storage focusing optics brought. This leads to the fact that on the optical storage dium simultaneously creates two foci lying side by side  with the help of two adjacent tracks at the same time can be written or read. From EP 0 653 748 A1 an optical disk storage is known, in which also Be more than two adjacent tracks at the same time can be written or read. From EP 0 559 435 A1 it is known the light of two laser radiation sources via a hologram element in this way onto a memory focus optics that bring two to adjacent tracks of an optical storage medium produces focused foci will.

It is known to increase the storage capacity (Laser Fo cus World, September 1995, p. 109), optical disk storage with several superimposed information carriers to be provided. The individual information carriers layers by vertically shifting the focus of the be hit laser radiation reached. For this, at least least use the upper layers of information for them Laser radiation can be partially transmissive.

A method and an apparatus for reading and / or reading write at least two superimposed pieces of information Carrier layers of optical storage media are from the patent application with the file number 196 34 590.1-53 known. It discloses a coaxial beam bundles of different wavelengths on one focus optics with pronounced chromatic longitudinal aberration to lead. The longitudinal aberration causes for the different Wavelengths different focal lengths, which exploited is, at the same time the traces in different informa to read or describe the carrier layers.

From DE-OS 26 34 243 (p. 10, 2nd paragraph) it is known to Guiding the beam describing a second lane a frequency of about 20 kHz perpendicular to the recording direction between this second track and a first track to move back and forth.  

They are also used for the controlled deflection of lasers radiate acousto-optical deflectors with sound waves knows (the electronics technician No. 1/1974; EL 25). An acousto-opti shear deflector comprises a solid, in the over a Transductor ultrasound waves are introduced. The Peri odicity of suitable ultrasonic waves leads to the Solid-state continuous electromagnetic radiation for Bragg reflection, and thus a distraction of a part of the beam at a certain angle. Through a variation the ultrasound frequency becomes a variation of the deflection kungswinkel the radiation reached. Such acousto-opti Deflectors (AOD's) are also from EP 0 490 013 A1 known. In particular, EP 0 490 013 A1 discloses one electro-optical scanner with an optical waveguide and an acoustic waveguide based on a transpa annuity substrate are arranged parallel to each other. By an acousto-optical interaction between the light waves in the optical waveguide with one in acoustic waves surface acoustic surface wave becomes a part the light waves from the optical waveguide con trolls distracted. It is disclosed this electro-opti scanner for reading and / or writing a tape conveyor to use information carriers in which the to be writing tracks perpendicular to the direction of movement of the ban the run. For this, it is used for reading and / or writing When the belt is running, the laser beam is used led along a complete track and then on brought the adjacent parallel track.

In the patent application with the file number 196 36 595.3-53 is the use of AOD's in connection with reading and / or writing to optical storage media. Accordingly, a laser beam is thus into a Oscillatory movement brought that focus in addition to several mutually lying tracks with a frequency in the MHz range scans. This means that several tracks of an In formation carrier layer can be read or described.  

It is an object of the present invention, method and Devices of the type mentioned are available who make it possible in an effective way to Data transfer rate when reading and / or writing opti storage media even when using only one wavelength to increase significantly.

In a method of the type mentioned at the beginning for reading op storage media in which laser radiation is directed towards the focused reading track and the reflected from the track Radiation to detect the information stored on the track mation is evaluated, the task is solved by that for simultaneous reading of traces in both informatics on carrier layers that have a certain direction of polarization having laser radiation by means of a birefringent optical element in two partial radiation beams with 90 ° divided polarization directions rotated against each other becomes a part and on both information carrier layers radiation beam is focused and from the storage medium reflected radiation after information carrier layers ge is evaluated separately.

The splitting of the laser radiation by means of the double bre appropriate optical element when using a umpte wavelength and a single memory focusing optics the generation of two foci with different focus so that both of them were exposed to radiation tion carrier layers of the storage medium simultaneously with the laser radiation can be scanned.

The method according to the invention can also be based on optical media media with more than two information carrier layers be performed. In this case they have to scanned information carrier layers also not immediately be directly adjacent to each other.

The method according to the invention can also be carried out in this way that that for reading at least two tracks simultaneously  in each of the two information carrier layers Focus on scanning the at least two tracks one after the other a predetermined frequency oscillating across the tracks is carried out and for each information carrier layer his information is sorted according to track affiliation.

The change between tracks has to be done so quickly that the focus, e.g. B. with rotating storage medium, a has just reached the track that has just been read out if there more information is available. So he becomes that is enough by a single beam, one after the other scans several tracks and from each of the tracks Informatio takes up these traces simultaneously and completely to be read. The order of the information gathered Appropriate software is used to track the this information taking into account the position of the Focus on the storage element controls applications or forwards data storage units.

In a procedure of the type mentioned at the outset ben optical storage media, for information transfer laser radiation modulated and applied in its intensity the track to be written is focused becomes the task solved in that for the simultaneous description of Spu ren in both information carrier layers on the upper In formation carrier layer a first linearly polarized Radiation bundles of a first radiation source and on the lower information carrier layer a second linear polar based radiation beam of a second radiation source fo is kissed by the in their polarization directions Radiation beams rotated 90 ° to one another in this way birefringent optical element that the Direction of polarization of the first radiation beam with the Direction of polarization for decent light and the polar direction of the second radiation beam with the pola direction of risk for extraordinary light coincides and by means of the different refractive behavior of the Beams of radiation in the birefringent optical element and  by means of memory focusing optics for each radiation a separate focus point is generated.

A second beam is used to write to optical memory Source of supply necessary, otherwise both information carriers would be described with the same information. The alignment of the linear polarization of the first or second beam on the polarization directions for ordinary or extraordinary light in double width The optical element allows a completely separate Focus the two beams on the bottom different layers of information. Inaccurate off direction of the polarization directions would z. B. a share from the first beam of light to extraordinary light split and thus on the wrong information carrier layer.

The inventive method for describing optical Memory can also be executed so that at the same time Describe at least two tracks in both Information carrier layers the respective focus the min scanning at least two tracks at a given frequency is oscillated over the tracks, the laser radiation the In intended for the track being scanned formation is modulated.

It is advantageous to use the aforementioned Ver drive so that the frequency is at least one MHz is. This can result in a data rate of more than one Mbit / s per track can be achieved.

With a device of the type mentioned at the beginning for reading optical storage media with a linearly polarized La radiation emitting radiation, in particular one Laser diode, a collimator optics for generating an im Diameter of constant radiation beam, one the beam bundle of solutions focusing on the storage medium focusing optics and one in the beam path between collima  coupling and storage focusing optics arranged decoupling beam splitter for decoupling from the storage medium the storage focusing optics reflected radiation into one Have means for evaluating the reflected radiation the evaluation arm, the task is solved by a beam lengang between decoupling beam splitter and storage medium located birefringent optical element, the optical axis of the birefringent optical element rela tiv to the direction of the linear polarization of the radiation bundle is oriented such that the incident beam bundle after first passing through the double arranged optical element in a partial radiation beam light and a partial radiation beam extraordinary Light is divided and by the storage focusing optics partial radiation on each of the two information carrier layers bundle is focused, in the evaluation arm a polarizing, the radiation reflected from the storage medium into the part beams of decent light and partial radiation bundle of extraordinary light splitting beamsplitters and both for the partial beam of decent light as well as the partial radiation beam of extraordinary light one detector element each for evaluating the data from the memory medium reflected radiation.

It is advantageous to design the device according to the invention in this way to form that for simultaneous writing at least two tracks in each of the two information carrier layers one in the beam path between the collimator and the coupling beam splitter arranged, a controlled, perpendicular to the Direction of propagation oscillating movement of at least one Part of the radiation beam generating deflection featured see is.

The device according to the invention can advantageously also do so be designed so that the deflection unit from the beam a static partial radiation beam and an os zilliering partial radiation beam generating acousto-opti shear deflector (AOD) and in the evaluation arm means for  Separation into the static and the oscillating beam bundles are provided.

In a device of the type mentioned for reading and / or writing optical storage media with a li near polarized laser light emitting first beam tion source, in particular a laser diode, a first Collimator optics for generating a constant diameter th first radiation beam, one the first radiation beam del focusing on the storage medium optics and one in the beam path between the collimator optics and Storage focusing optics arranged decoupling beam splitter for decoupling the storage medium from the storage medium kissing optics reflected radiation into a means for Evaluation of the evaluator having reflected radiation tearm, the task is solved by a linear polarizing tes laser light emitting second radiation source, esp special a laser diode, a second collimator optics for Er Generation of a second radiation constant in diameter bundle, a combination element to bring the two together Radiation bundle to a total radiation bundle, the to both radiation beams in the total radiation beam by 90 ° have mutually twisted directions of polarization, an im Beam path between the output beam splitter and storage space dium birefringent optical element, wherein the optical axis of the birefringent optical element is oriented such that the direction of polarization of the he most beams of ordinary light and Polarization direction of the second radiation beam that of extraordinary light and neat and extraordinary light in the birefringent element below have different radiation patterns, and double chende optical element is designed such that by the Storage focusing optics the first and second radiation beams focused on different layers of information are, and in the evaluation arm a polarizing, which from Storage medium reflected radiation in the first and second radiation beam splitting beam splitter, each  of the radiation beam from its own detector element evaluation of the radiation reflected from the storage medium leads is.

The device for reading and / or writing optical Storage media can advantageously also be designed such that the combination element is a polarizing beam ler cube is. The polarizing beam splitter cube is here to align so that the light of a radiation source can pass through almost losslessly, while the Light from the other radiation source almost completely at the by 45 ° against the direction of the first radiation beam inclined reflecting surface is reflected.

The device according to the invention can also advantageously do so be formed that the birefringent optical element is a concave lens.

Both radiation beams are applied through the concave lens expands. The widening is for the proper light and the extraordinary light different. When on enters the storage focusing optics following in the beam path two different focus points are therefore created.

As an alternative to the concave lens, a convex lens or a birefringent plane parallel plate can be used.

The device according to the invention can also be designed in this way be that the birefringent optical element is part the focusing optics.

According to the invention, the device for reading and / or loading write also be designed so that for simultaneous Writing and / or reading at least two tracks in each because two information carrier layers in the beam path between the combination element and the coupling beam part ler a controlled, perpendicular to the direction of propagation  oscillating movement of at least part of the total radiation deflecting unit is arranged.

Furthermore, the device according to the invention can be read and / or writing to optical storage media advantageously be designed so that the deflection unit one of the two Radiation beams each have a static partial radiation beam and an oscillating partial radiation beam generating acousto optical deflector (AOD) is a masking unit for masking provided glare of the static partial radiation beam is a first substitute beam for the first radiation source tion source, in particular a laser diode, with one of the Most radiation source corresponding polarization direction is provided on for the first substitute radiation source whose radiation is a first static equivalent radiation beam constant diameter generating collimator optics hen is means for coupling the first substitute radiation into the beam path following the masking unit are provided, the first beam of equivalent radiation hidden static partial radiation beam replaced, and in Evaluation arm for the first radiation beam means for opening of the first static equivalent radiation beam and oscillating partial radiation beam are provided.

An acousto-optical deflector generates with its static Partial radiation beam (zero order diffraction) a beam that is different from the oscillating radiation beam del (first order diffraction) remains on a track. At the Writing a storage medium would therefore be static Partial radiation beams destroy this trace, since the same che information sequence is modulated on how the oscillate the partial radiation beam; the static partial radiation beam would be all for several adjacent tracks agreed to transfer information to a track and this to destroy. So it is imperative to use the static beam to hide the bundle of light before it reaches the optical memory dium reached. However, since a static partial radiation beam is at least necessary for tracking, instead  the radiation of the substitute radiation source in the beam path coupled in such a way that it replaces the original static Partial radiation beam replaced. The replacement radiation beam del would only be used for tracking, the would correspond corresponding track of the storage medium is not described. This Disadvantage is compensated for by the fact that the partial radiation beams a multitude of traces can be described at the same time. But it is also possible Lich, the intensity of the equivalent radiation source dulate and thus the track it affects if to describe.

Furthermore, the device according to the invention can also look like this be formed that a for the second radiation source second substitute radiation source, in particular a laser diode, with a pola corresponding to the second radiation source direction of risk is provided for the second replacement Radiation source a second stati from their radiation equivalent radiation beam of constant diameter collimator optics is provided, means for coupling of the second beam of substitute radiation into that of the blanking Unit following beam path are provided, the second replacement radiation beam coaxial to the first replacement radiation beam runs, and in the evaluation arm for the second Radiation beam means for separating the second static Replacement radiation beam and oscillating partial radiation beam del are provided.

With the help of the second alternative radiation beam it is possible to describe another track.

The inventive device for reading and / or loading write can also be designed so that the fade Unit for blanking out the static partial radiation beam from a blanking which focuses the partial radiation beams focusing optics, one in the focal plane of the blanking focus sieroptik arranged point aperture and a collision mator optics exists.  

The static part becomes by the fade-out focusing optics focused on the spot diaphragm and on faded out from the subsequent beam path. As long as the oscillating partial radiation beam is not in the Position of the static partial radiation beam has happened it the blanking device. The collimator optics he creates a parallel beam again.

The inventive device for reading and / or loading write can also be designed so that the means for Coupling of the replacement radiation beam in the beam path arranged between blanking unit and coupling beam splitter Neter coupling beam splitter is.

The devices according to the invention can also be designed in this way det be that in the evaluation arm, the means for separating static radiation beam and oscillating part radiation beam in the beam path of both the first and of the second radiation beam are arranged and for each static beams of static radiation and any oscillating Partial radiation beam vorese a separate detector element hen is.

The evaluation arm reflects the one reflected by the storage medium Radiation using an appropriately oriented polarisie beam splitter again arranged in partial radiation beams light and extraordinary light, which one Division into the first (from the first radiation source originating) and the second (from the second radiation source originating) radiation beam corresponds. After this division lung is ordinary and extraordinary radiation again in one static and one oscillate split the share, which is then a detector element be fed.

This double division can also be done in reverse rows follow happen by first re of the storage medium  reflected radiation into a static and an oscillie is divided and the static as well also the oscillating partial radiation beam one at a time polarizing beam splitter cube is then supplied in turn the respective partial radiation beam in one partly ordinary light and partly extraordinary Divides light.

The devices according to the invention can also be advantageous be designed so that the means for doors in the evaluation arm static static radiation beam and oscillate an evaluation beam splitter for the partial radiation beam division of the radiation to be separated into two equal beams components, one focus for each radiation component optical optics, one for the first radiation component Focal plane of the first focusing optics arranged, alone on Location of the focus of the static equivalent radiation beam through casual aperture and one for the second radiation component arranged in the focal plane of the second focusing optics, for the radiation of the static equivalent radiation beam un are permeable point diaphragm.

Finally, the device according to the invention can be so forms be that the memory focusing optics a distinctive has chromatic aberration.

This makes it possible to change over targeted wavelengths the position of the two fo kiss at different thicknesses of the information carrier adapt layers.

The following are preferred embodiments of the invention method according to the invention and two preferred training shape the device according to the invention with reference to figures described.  

It shows a schematic representation

Fig. 1 is a read / write unit,

Fig. 2 shows a part of a read / write unit with acousto optical deflector,

Fig. 3 shows a detailed representation of part of the read / write unit. Fig. 2

Fig. 4 shows a further part of the read / write unit of FIG. 2.

In Fig. 1, a write / read unit is schematically Darge, with the two tracks 1 and 2 one here only in section and greatly enlarged WORM CD 3 can be written and / or read out simultaneously. Tracks 1 and 2 each belong to a different information carrier layer 4 and 5 . Laser radiation from two laser diodes 6 and 7 is used to write or read tracks 1 and 2 . The linear polarized radiation emerging from the laser diodes 6 and 7 is bundled by the collimating optics 8 and 9 and placed on a linearly polarizing beam splitter cube 10 . The direction of polarization of the radiation emanating from the laser diode 6 is perpendicular to that of the radiation emanating from the laser diode 7 . The linearly polarizing beam splitter cube 10 is oriented so that the radiation beam of the Laserdi ode 6 passes through the beam splitter cube 10 almost loss-free and the radiation beam of the laser diode 7 is reflected almost losslessly, so that both radiation beams are coaxial with each other in the further course.

By a further beam splitter 11 , which is not polarizing, however, part of the radiation beam is reflected in the direction of a storage focusing optics 12 . The memory focusing optics 12 is composed of a concave lens 13 made of birefringent material and an ordinary convex lens 14 . The optical axis of the birefringent material of the concave lens 13 is oriented such that the two mutually perpendicular polarization directions of the radiation from the laser diodes 6 and 7 correspond to the polarization directions of the ordinary and extraordinary light of the birefringent material. Furthermore, the orientation of the birefringent material must be such that in the concave lens 13 the ordinary and the extraordinary light have different refractive behavior. As a result, one of the radiation beams is expanded more than the other through the concave lens 13 . As a result, the convex lens 14 produces two focal points 15 and 16 offset from one another in the beam path. The radiation from the focal point 15 , which is directed onto the track 1 , originates, for. B. only the Laserdi ode 6 . Then the focal point 16 , which is directed to the track 2 ge, it is generated solely by radiation from the laser diode 7 . Thus, the two tracks 1 and 2 can be described independently of one another if different information is modulated onto the intensities of the radiation from the laser diodes 6 and 7 .

From the tracks 1 and 2 , the radiation is reflected back into the beam splitter 11 by the memory focusing optics 12 . The beam splitter 11 now functions as a coupling beam splitter, through which the radiation reflected by the CD 3 enters an evaluation arm 17 . Here is another linearly polarizing beam splitter cube 18 in the beam path, which is oriented such that again the radiation originating from the laser diode 6 is separated from that of the laser diode 7 and is focused on two different detector elements by means of focusing optics 19 and 20, respectively. It is therefore possible to read tracks 1 and 2 independently of one another.

To describe tracks 1 and 2 , only one of the detector elements 21 and 22 need to be put into operation for tracking.

Fig. 2 shows schematically part of a further read / write unit, which makes it possible to simultaneously write and / or read out several tracks 1 a, 1 b, 1 c or 2 a, 2 b, 2 c in two information carrier layers . Optical elements of this read / write head, which are also in accordance with the structure of the unit. Fig. 1 are present in Fig. 2 have the same reference numerals. For the description of the function of these same optical elements, reference is made to the description of FIG. 1.

Also according to the construction. Fig. 2 is the linearly polarized radiation of two laser diodes 6 and 7 via a linear polarizing beam splitter cube 10 , a non-polarize the beam splitter 11 and a memory focusing optics 12 with birefringent concave lens 13 on the CD 3 such that the radiation of each laser diode 6th or 7 is focused on another information carrier layer 4 or 5 . In the beam path between the polarizing beam splitter cube 10 and the beam splitter 11 , an optical path 23 is symbolized by the box in FIG. 2, which is shown schematically in FIG. 3.

Thus, hitting the polarizing beam splitter cube 10 leaving the total radiation beam 24 onto an acousto-optic rule deflector (AOD) 25th The AOD 25 generates a static partial radiation beam 26 and an oscillating partial radiation beam 27 , which is shown in FIG. 3 in its extreme positions. The oscillating movement of the partial beam bundle 27 has an effect on the CD 3 in such a way that the associated two focus points generated by the storage focusing optics 12 in the two information carrier layers 4 and 5 via the tracks 1 a, 1 b, 1 c and 2 a, 2 b, 2 c perform an oscillating movement. It is thereby achieved that the tracks 1 a, 1 c, 2 a, 2 c can be written to and / or read out simultaneously by means of the oscillating partial radiation beam 27 .

The static partial radiation beam 26 has to be faded out from the further beam path by means of the dazzle device 28 , because in the case of writing to the CD 3 the static partial radiation beam would transmit information for a plurality of traces of an information carrier layer 4 or 5 , but would remain constantly on the Track 1 b or 2 b and would destroy them as a result.

The blanking device 28 has a blanking focusing optics 29 , which focuses the oscillating partial radiation beam 27 and the static partial radiation beam 26 into the plane of a spot stop 30 . As a result, the static partial radiation beam 26 is completely masked out, while the oscillating partial radiation beam 27 can pass as long as it does not coincide with the static partial radiation beam 26 . In the further beam path, a collimation optics 31 ensures renewed focusing of the oscillating partial radiation beam 27 .

Without any further measure the dot screen 30 would cause would be that the tracks 1 and b 2 b is not applied in a suitable manner with radiation. For this reason, the static partial radiation beam 26 must be replaced by a static replacement beam 32 . This is done via an alternative radiation source, not shown here, by means of a coupling beam splitter 33 . Care should be taken to ensure that the replacement radiation coupled in through the coupling beam splitter 33 corresponds in its linear polarization to the radiation of the laser diodes 6 or 7 . If the static part of radiation beam 32 are only used to control the tracking, should therefore lanes 1 and b 2 b not be described at the same time or read a replacement sufficient radiation source. However, if both tracks 1 b and 2 b are to be written or read out, the radiation from a further substitute radiation source, also not shown here, must be coupled in by means of a two coupling beam splitter 34 , which then corresponds in its linear polarization to that of the other laser diodes 6 and 7 , respectively. After coupling the replacement radiation beam 32 successfully, both the oscillating partial radiation beam 27 and the static replacement radiation beam 32 hit the CD 3 . The oscillating partial radiation beam 27 oscillates from track 1 a or 2 a to track 1 c or 2 c with a frequency in the MHz range. The oscillation of the partial radiation beam 27 means a not necessarily sinusoidal back and forth but a jerky movement in order to remain on a track for a certain time and to read out information there or to describe the track.

From the tracks 1 a to 1 c and 2 a to 2 c, the incident radiation is reflected via the storage focusing optics 12 and the beam splitter 11 into the evaluation arm 17 and hits the polarizing beam splitter cube 18 there . This is aligned in such a way that the radiation is divided into two parts, one part coming only from the laser diode 6 and the corresponding substitute radiation source and the other part coming solely from the laser diode 7 and associated substitute radiation source.

Both parts meet in the further beam path in each case on a part of the evaluation unit which is no longer shown in FIG. 2 and is shown schematically in FIG. 4. The arrow in FIG. 4 indicates the direction of the radiation leaving the beam splitter cube 18 and thus corresponds to the arrows in FIG. 2. The radiation beams shown in FIG. 4 are, as described above, only those for a specific laser diode 6 or 7 and the corresponding replacement radiation source belonging to portions of the oscillating radiation beam 27 and the static radiation beam 32nd For a simplified illustration, the radiation beam del according to FIG. 4 is referred to in the following, however, again as an oscillating partial radiation beam 27 and a static replacement beam 32 .

To evaluate the radiation reflected from the CD, the static equivalent radiation beam 32 and the oscillating partial radiation beam 27 must be separated from one another. For this purpose, both radiation beams 27 and 32 are placed on a non-polarizing evaluation beam splitter 35 , which in turn generates two portions of the radiation. One portion is focused via a focusing optics on a spot diaphragm 37 , whereby the static beam of substitute 32 is faded out. The oscillating partial radiation beam 27 is brought to the detector element 39 via further focusing optics 38 . On the detector element 39, the Informa contained in the oscillating portion of radiation beam 27 is read out and then assigned tion of the associated focus on the disc 3 of the entspre sponding track, knowing the momenta NEN position. The oscillating part is hidden radiation beam 27 from the second through the Auswer testrahlteiler 35 generated portion in a corresponding manner by means of a pinhole 40th The static replacement beam 32 is focused via the focusing optics 41 and 42 on the detector element 43 , so that the static replacement beam 32 can be evaluated for reading out the associated track and / or for tracking.

Reference list

1

track

2nd

track

3rd

WORM CD

4th

Information carrier layer

5

Information carrier layer

6

Laser diode

7

Laser diode

8th

Collimator optics

9

Collimator optics

10th

linearly polarizing beam splitter cube

11

Beam splitter

12th

Memory focusing optics

13

birefringent concave lens

14

Convex lens

15

Focus point

16

Focus point

17th

Evaluation arm

18th

linearly polarizing beam splitter cube

19th

Focusing optics

20th

Focusing optics

21

Detector element

22

Detector element

23

optical path

24th

Total radiation beam

25th

AOD

26

static partial radiation beam

27

oscillating partial radiation beam

28

Masking device

29

Fade-out focusing optics

30th

Dot aperture

31

Masking collimator optics

32

Substitute radiation bundle

33

Coupling beam splitter

34

Coupling beam splitter

35

Evaluation beam splitter

36

Focusing optics

37

Dot aperture

38

Focusing optics

39

Detector element

40

Pinhole

41

Focusing optics

42

Focusing optics

43

Detector element

Claims (20)

1. A method for reading optical storage media ( 3 ) with th in two superimposed information carrier layers ( 4 , 5 ) for information storage serve the essentially parallel tracks ( 1 , 2 ), where the upper information carrier layer ( 4 ) is partially transparent, in which

• a) laser radiation is focused on the track to be read ( 1 , 2 ) and the radiation reflected by the track ( 1 , 2 ) is used to detect the information stored on the track ( 1 , 2 ),
  characterized in that
• b) for simultaneous reading of tracks ( 1 , 2 ) in both information carrier layers ( 4 , 5 ) the laser radiation having a certain polarization direction by means of a double refractive optical element ( 13 ) in two radiation beams with 90 ° rotated polarization directions divided on is and a partial radiation beam is focused on both information carrier layers ( 4 , 5 ), and
• c) the radiation reflected by the storage medium ( 3 ) is evaluated separately according to information carrier layers ( 4 , 5 ).

2. The method according to claim 1, characterized in that for the simultaneous reading of at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) layers in each of two information carriers ( 4 , 5 ) the respective focus at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) successively scanning with a predetermined frequency oscillating over the tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) is performed and for each information carrier layer ( 4 , 5 ) the information read is classified according to tracking. 3. A method for writing to optical memories ( 3 ) with th in two superimposed information carrier layers ( 4 , 5 ), for information storage serve the essentially parallel tracks ( 1 , 2 ), where the upper information carrier layer ( 4 ) is partially transparent the

• a) for information transmission, laser radiation is modulated in its intensity and focused on the track to be described ( 1 , 2 ), characterized in that
• b) for simultaneous writing to tracks ( 1 , 2 ) in both information carrier layers ( 4 , 5 ) on the upper information carrier layer ( 4 ) a first linearly polarized radiation beam of a first radiation source ( 6 , 7 ) and on the lower information carrier layer ( 5 ) a second linearly polarized radiation beam of a second radiation source ( 6 , 7 ) is focused by
  • aa) the radiation beams rotated in their polarization directions by 90 ° to one another are guided onto a double-breaking optical element ( 13 ) in such a way that the polarization direction of the first radiation beam coincides with the polarization direction for ordinary light and the polarization direction of the second radiation beam with the polarization direction for extraordinary light and
  • bb) a separate focal point is generated for each radiation beam by means of the different refractive behavior of the radiation beams in the birefringent optical element ( 13 ) and by means of storage focusing optics ( 12 ).

4. The method according to claim 3, characterized in that for simultaneously describing at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) in each of two information carriers layers ( 4 , 5 ) the respective focus at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) scanning with a predetermined frequency oscillating over the tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c ) is performed, the laser radiation being modulated with the information intended for the track being scanned ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c). 5. The method according to claim 2 or 4, characterized records that the frequency is at least one MHz. 6. Apparatus for reading optical storage media ( 3 ) with th in two superimposed information carrier layers ( 4 , 5 ), for information storage, serve the essentially parallel tracks ( 1 , 2 ), where the upper information carrier layer ( 4 ) is partially transparent, With

• a) a linearly polarized laser light-emitting radiation source ( 6 , 7 ), in particular a laser diode,
• b) collimator optics ( 8 , 9 ) for generating a radiation beam that is constant in diameter,
• c) one focusing the radiation beam on the storage medium ( 3 ) fo focusing optics ( 12 ) and
• d) one in the beam path between collimator optics ( 8 , 9 ) and storage focusing optics ( 12 ) arranged Auskoppelstrahltei ler ( 11 ) for decoupling the radiation reflected from the storage medium ( 3 ) through the storage focusing optics ( 12 ) in a means for evaluating the reflected radiation on pointing evaluation arm ( 17 ),
  marked by
• e) a birefringent optical element ( 13 ) located in the beam path between the output beam splitter ( 11 ) and the storage medium ( 3 ), the optical axis of the birefringent optical element ( 3 ) being oriented relative to the direction of the linear polarization of the radiation beam in such a way that the incident radiation beam after it has first passed through the birefringent optical element is divided into a partial radiation beam of ordinary light and a partial radiation beam of extraordinary light and the storage focusing optics ( 12 ) focus on each information carrier layer ( 4 , 5 ), one partial radiation beam each,
• f) in the evaluation arm ( 17 ) a polarizing, from the storage medium ( 3 ) reflected radiation into the partial radiation beam ordinary light and the partial beam extraordinary light beam splitter and
• g) a detector element ( 21 , 22 ) for evaluating the radiation reflected by the storage medium ( 3 ) both for the partial radiation bundle ordinary light and the partial radiation bundle extraordinary light.

7. The device according to claim 6, characterized in that for simultaneously writing to at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) in each of two information carrier layers ( 4 , 5 ) one in the beam path between the collimator ( 8 , 9 ) and the output beam splitter ( 11 ) arranged, a controlled, perpendicular to the direction of propagation movement at least a portion of the radiation beam generating deflection unit ( 25 ) is provided. 8. The device according to claim 7, characterized in that

• a) the deflection unit ( 25 ) from the radiation beam is a static partial radiation beam ( 26 ) and an oscillating partial radiation beam ( 27 ) generating acousto-optical de flector (AOD), and
• b) means are provided in the evaluation arm ( 17 ) for separation into the static and the oscillating partial radiation beam.

9. A device for reading and / or writing optical storage media ( 3 ) with two information information layers ( 4 , 5 ) one above the other, for information storage, essentially parallel tracks ( 1 a, 1 b, 1 c, 2 a , 2 b, 2 c), the upper information carrier layer ( 4 ) being partially transparent, with

• a) a linearly polarized laser light-emitting he most radiation source ( 6 ), in particular a laser diode,
• b) first collimator optics ( 8 ) for generating a first radiation beam which is constant in diameter,
• c) a storage focusing optics ( 12 ) focusing the first radiation beam onto the storage medium ( 3 ) and
• d) a coupling beam splitter ( 11 ) arranged in the beam path between the collimator optics ( 8 ) and the storage focusing optics ( 12 ) for coupling out the radiation reflected by the storage medium ( 3 ) through the storage focusing optics ( 12 ) into a means for evaluating the reflected radiation on pointing evaluation arm ( 17 ),
  marked by,
• e) a linearly polarized laser light-emitting second radiation source ( 7 ), in particular a laser diode,
• f) a second collimator lens ( 9 ) for generating a second radiation beam which is constant in diameter,
• g) a combination element ( 10 ) for bringing together the two radiation bundles to form a total radiation bundle ( 24 ), the two radiation bundles in the total radiation bundle ( 24 ) having polarization directions rotated by 90 ° to one another,
• h) a birefringent optical element ( 13 ) located in the beam path between the output beam splitter ( 11 ) and the storage medium ( 3 ), wherein
  • aa) the optical axis of the birefringent optical element ( 13 ) is oriented such that the direction of polarization of the first beam of ordinary light and the direction of polarization of the second beam of extraordinary light speaks and ordinary and extraordinary light in the birefringent element ( 13 ) have different radiation courses, and
  • bb) the birefringent optical element ( 13 ) is designed such that the storage focusing optics ( 12 ) focus the first and second radiation beams onto different information carrier layers ( 4 , 5 ), and
• i) in the evaluation arm ( 17 ) a polarizing, the radiation from the storage medium ( 3 ) reflected radiation into the first and second radiation beams splitting beam splitter ( 18 ), where each radiation beam has its own detector element ( 21 , 22 ) for evaluating the from the storage medium ( 3 ) reflected radiation is supplied.

10. The device according to claim 9, characterized in that the combination element ( 10 ) is a polarizing beam splitter cube. 11. Device according to one of claims 6 to 10, characterized in that the birefringent optical element ( 13 ) is a concave lens. 12. Device according to one of claims 6 to 11, characterized in that the birefringent optical element ( 13 ) is part of the focusing optics ( 12 ). 13. The device according to one of claims 9 to 12, characterized in that for simultaneous writing and / or reading at least two tracks ( 1 a, 1 b, 1 c, 2 a, 2 b, 2 c) in each of two information carrier layers ( 4 , 5 ) in the beam path between the combination element ( 10 ) and the outcoupling beam splitter ( 11 ) there is a controlled deflection unit ( 25 ), which oscillates perpendicularly to the direction of propagation and generates at least a part of the total radiation beam ( 24 ). 14. The apparatus according to claim 13, characterized in that

• a) the deflection unit ( 25 ) is an acousto-optic deflector (AOD) which generates a static partial radiation beam ( 26 ) and an oscillating partial radiation beam ( 27 ) from each of the two radiation beams,
• b) a blanking unit ( 28 ) for blanking out the static partial radiation beam ( 26 ) is provided,
• c) for the first radiation source ( 6 ) a first replacement radiation source, in particular a laser diode, with a polarization direction corresponding to the first radiation source ( 6 ) is provided,
• d) for the first alternative radiation source, a static alternative radiation beam ( 32 ) of constant diameter generating collimator optics is provided from the radiation thereof,
• e) means ( 33 ) for coupling the first alternative radiation beam into the beam path following the masking unit ( 28 ) are provided, the first alternative radiation beam replacing the masked static partial radiation beam ( 26 ), and
• f) means are provided in the evaluation arm ( 17 ) for the first radiation beam for separating the first static substitute radiation beam and the oscillating partial radiation beam ( 27 ).

15. The apparatus according to claim 14, characterized in that

• a) for the second radiation source ( 7 ) a second replacement radiation source, in particular a laser diode, with a polarization direction corresponding to the second radiation source ( 7 ) is provided,
• b) for the second alternative radiation source, a collimator optic is produced from the radiation of which a second static alternative radiation bundle of constant diameter is provided,
• c) means ( 34 ) for coupling the second alternative radiation beam into the beam path following the masking unit ( 28 ) are provided, wherein the second alternative radiation beam del is coaxial with the first alternative radiation beam ( 32 ), and
• d) in the evaluation arm ( 17 ) for the second radiation beam With tel for the separation of the second static replacement radiation beam del and oscillating partial radiation beam ( 27 ) are provided.

16. The apparatus according to claim 14 or 15, characterized in that the masking unit ( 28 ) for masking the static partial radiation beam ( 26 ) from a partial radiation beam ( 26 , 27 ) focusing masking optics ( 29 ), one in the focal plane of the masking focus optical optics ( 29 ) arranged point diaphragm ( 30 ) and an anti-glare collimator ( 31 ). 17. The device according to one of claims 14 to 16, characterized in that the means ( 33 , 34 ) for coupling the replacement radiation beam is a coupling beam splitter arranged in the beam path between the blanking unit ( 28 ) and coupling beam splitter ( 11 ). 18. The apparatus according to claim 8 or according to one of claims 14 to 17, characterized in that in the Auswer tearm ( 17 ) the means for separating static replacement radiation beam ( 32 ) and oscillating partial radiation del ( 27 ) in the beam path of both the first and of the second radiation beam are arranged and a separate detector element ( 39 , 43 ) is provided for each static replacement radiation beam ( 32 ) and each oscillating partial radiation beam ( 27 ). 19. The apparatus according to claim 8 or according to one of claims 14 to 18, characterized in that in the Auswer tearm ( 17 ) the means for separating static replacement radiation beam ( 32 ) and oscillating partial radiation del ( 27 )

• a) an evaluation beam splitter ( 35 ) for dividing the radiation to be separated into two equal radiation components,
• b) focusing optics ( 36 , 41 ) for each radiation component,
• c) for the first radiation component, one arranged in the focal plane of the first focusing optics ( 41 ), only at the location of the focus of the static substitute radiation beam ( 32 ) through a casual aperture plate ( 40 ) and
• d) for the second radiation component, a point diaphragm ( 37 ) which is arranged in the focal plane of the second focusing optics ( 36 ) and is opaque for the radiation of the static alternative radiation beam ( 32 )

are. 20. Device according to one of claims 6 to 19, characterized in that the memory focusing optics ( 12 ) has a pronounced chromatic aberration.