DE3145128A1 - DEVICE FOR RECORDING DATA INFORMATION IN A DISK-SHAPED OPTICAL READABLE RECORDING CARRIER - Google Patents

Description

II Flips'61oeilampenfabriok6n; -Ei:, lL, .-: i 1. : · -; \ 3 U 51 2

PHN 9886. . . L 24-3-1981

Apparatus for recording data information in a · * 'Jn- i *; <-. η försni (ran optically "readable recording medium.

The invention relates to an apparatus for recording information on a recording medium comprising a disk-shaped substrate with a ■ radiation-sensitive information layer contains and with a spiral or concentric

.Supplied information areas arranged in a track pattern • is, this device having a light source, an optical system for directing a beam of light onto the Information areas of this recording medium, one Recording circuit for modulating the light beam as a function of the digital signal to be recorded and an optical system with a detector for detection Loren olner from. Record carriers reflected or raL La durchgeXassenon radiation is provided.

A recording medium of the type mentioned at the beginning

Art and a device for recording and / or reading out information on and / or from such Recording medium is known from DE-OS 29 09 877,

the information areas with synchronization areas 20

alternate with the address of the next Information area included. When using such a The clock generation is involved in the recording medium and sometimes not particularly reliable. At the

It is possible, but complicated, to read from the on-25

Hdiriobonen data signal and from the in the synchronization /; olili »t <i mi1 '; - γ ° iioiniiionon ΓηΓο rnuil-ioiiaad- ^ nal uii olii to create. When writing data signals into the information areas, the clock generation is even more complex, because then only the information recorded in the synchronization areas can be used, in which case a Clock generator which, when reading out the synchronization areas, uses a phase-locked loop with the in the

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■: 3U5128

PHN 9886. £ 25-3-1981

Synchronization areas recorded information synchronized can be applied, which in addition to the complexity mentioned after the additional disadvantage shows that the 5th phase-locked loop in question is caught again at the beginning of each synchronization area must be and then the synchronous advance with the locomotion of the recording medium for data recording in the information areas is not reliable, so that not every information area used to its end ^ is because space must be reserved to take the effects of any Changes in speed of the recording medium and of the information recording as a result of the change to compensate for the frequency of the clock generator. In the cited patent application it was therefore proposed that · in the Information areas to include additional synchronization areas, thereby reducing the problems mentioned, but not eliminating them and thereby reducing the information storage capacity of the recording medium will. With Auf ζ i cimungs t r ä {; o im, where ltelno synchroni -

20th

application areas between information areas become digital, such as recording media for recording encoded audio signals, clock generation is even more complex. .

In the German patent registration P 3100-21.0, which was not previously published by the applicant, the solution was

. suggested the tracks of the record carrier beforehand. to be provided with periodic track modulation in order to simplify clock generation. This older patent application

is as Figures 1 - 13 with the associated description in the 30th

present application included.

Another problem also plays a role in devices of the type mentioned above. When recording digital Information, the reliability of the recorded information must be very high. There are already a. A number of methods have been proposed for correcting errors in the recorded data signal. A disturbing one Failure to take all measures to increase this reliability eliminated, occurs when recording the "

PHN 9886 5 "3/25/1981

Laser beam unintentionally leaves the track and "scratches" information that has already been written. If this 'happens, this scribble is caused by the inertia • of a radial follow-up system used (see, among others,

US-PS 4,223-187) very graciously on the information in the neighboring sectors are drawn, so that much "Information within a single information area is corrupted; this is a situation that even occurs through very satisfactory error correction methods no longer can be improved.

One possible solution is that the signal of the radial follow-up system is monitored and that, if this signal exceeds set limits, the recording is interrupted and the information is transferred to another Information area is rewritten. It should be noted that if the recording is wrongly interrupted becomes, unnecessary rewritten information areas are obtained, and that when recording is not erroneously interrupted, poor reliability of the recorded information is obtained. That The method proposed here for monitoring the radial follow-up signal is not entirely satisfactory in this regard, because according to this method the information is a relatively low-frequency part of the signal spectrum

is taken, making this procedure, for faults with not irrecoverable consequences, such as changes in.dem reflection coefficient of the plate and local Flaw in the plate that is quite sensitive; these

• Disturbances often lead to a tracking error, the

However, it is not large enough to bring the beam onto a different track, thereby interrupting the zooming process would not be required, but still takes place.

The invention has the object to provide a device ■ · of the type mentioned, which, in use,

■ the problems mentioned do not adhere to the system.

The device according to the invention is characterized »that for reading out a recording

PHN-9886 W ' 3/25/1981

carrier in which the information areas are a periodic Track modulation, the period of which corresponds to a frequency, ' in the case of the performance spectrum of the digitally coded information to be recorded or possibly recorded has at least almost one zero point, .for the generation of a clock signal with bit frequency for synchronization of the digitally coded information when recording and / or reproducing, this periodic Track modulation is installed in the track in such a way that

¹ ^ points of this track modulation with the same phase from track to track along one of the radial directions

^ line deviating from the line so that the track modulation Ι

each track as a function of the circumferential angle of the disc-shaped Recording medium in the one radial direction

15th

direction in phase always compared to the track modulation of the in

this radial direction adjoining track leads and always opposite in phase in the other radial direction lags the track modulation of the track adjoining it in the other radial direction, the "device ent- ' 20th

holds: a bandpass filter for filtering a SifjnalH mil:

a frequency, which is determined by the period of the periodic track modulation, from this defceked radiation, this signal as. Clock signal of the write circuit for the synchronization of the / ^ to be recorded. 25th '

! Information signal with the periodic track modulation is supplied so that the information to be recorded is recorded in a fixed phase relationship with this periodic track modulation, and a phase comparison circuit to monitor the current phase of the

oU

called filtered signal, in order, when the phase is in a predetermined measure from that of a signal with it ' uniformly changing phase deviates, · a signal for Generate interruption of the recording process, gg The invention is based on the knowledge that

it in the proposed system in the said earlier application, in which one with the bit frequency of the to be recorded Data signal synchronous frequency is previously attached to the record carrier, this frequency

PIIN 9886 % s 25.3.1981.

■% ■

both when reading and when writing information can be detected without significant interference with this data signal and without loss of storage capacity, so that an exactly synchronous and reliable clock signal is always available is possible by monitoring the phase response the periodic track modulation to gain a signal that indicates whether the write beam is inadmissible deviates from the track mentioned because the offset phase of the adjacent track is then detected. This method is less sensitive to low frequency interference because according to this method, the information is taken from a high-frequency signal.

'A preferred embodiment of this device can further characterized in that the phase comparison

¹ ^ circuit is included in a phase-locked loop, this phase comparison circuit said filtered signal and that of an oscillator controlled by the output signal of this phase comparison circuit via a low-pass oscillator.

Resulting signal are supplied, the output signal

this Rixisaaverfjlcdchsschaining is fed to a window detector!

This device, which with optical means for ■ directing a with the information to be recorded modulier- ' th. Beam of light on the information areas and for directing a ray of help on the information areas behind the

·

modulated beam for reading out the modulated by the Light beam recorded information is provided, can be further characterized in that the auxiliary beam increases Reading out the periodic track modulation for generation

of the clock signal is used to write information. '

tion with the other beam, and for that Supplying the signal to the phase comparison circuit. Some embodiments of the invention are in the drawing and are described in the following:

Fig. T shows a possible embodiment of an assembly

Drawing carrier, in which the principle according to the invention is applied, - wherein Fig. 1a is a plan view of the recording medium, FIG. 1b shows, on an enlarged scale, part of a track 4 of this recording medium and FIG. 1c

PHN 9886 Jf ;. · Π_ · 3- | <) Η1

a synchronization area on a larger scale Represent part;

FIG. 2 shows a small part of a section along the line H-II ¹ of FIG. 1a; ■

3 in FIGS. 3a to 3d schematically a longitudinal section through part of the track k, FIG. 3a showing such a section in an unwritten, prepared disk according to a known technique, FIG. 3b such a section according to FIG. 3a, after information in the information area 9 is inscribed, Fig. 3c such a section in an unwritten, prepared disk according to the invention, Fig. 3d such a section according to Fir, "· ") <■ '* after digital information has been written in .LaL, Fig the signal obtained when reading out the in Fig.

. 3d part of the track and FIG k shown in section, jt 'eh txs schematically a plan view of a part of the track to your writing digital information represented in other ways than shown in Fig 3b and 3d.

FIG. H shows the relevant power spectra of three digital information signal modulations; FIG.

Fig. 5 is a diagrammatic representation of these modulations;

Fig. -6 in Fig. 6a schematically shows an apparatus for producing a recording medium according to Fig. 3t; FIG. 6b schematically shows a device for writing information into the recording medium according to FIG. 6c and FIG. 6c a device for reading out a written recording medium;

Figure 7 shows a number of examples of periodic track modulation according to the invention;

8a shows the principle of a reading part of a device for reading out and / or recording a digital signal from or possibly on a recording medium according to the invention and FIG. 8b the frequency spectrum

^ ⁵ of the signal detected by the detector 27;

Fig. 9a shows a device according to Fig. 8a, the. themselves also suitable for generating a radial follow-up signal, and FIG. 9b shows the frequency spectrum of the front detector 27 do LoU-I. i or-

PHX 0886 '3 »^ 224-3-1981

th signal;

10 shows a modification of the device according to FIG. 9a; .

11a shows a device according to FIG. 9a> that for a record carrier with a radial track modulation with almost the same period as the periodic track modulation is set up, and Fig. 11b the frequency-K ι) o U I. v-iuii of the detector 27 de (.eic tier th signal;

FIG. 12 shows a device which is used for a recording medium with radial track modulation having the same period as the periodic track modulation is;

.Fig. 13 shows part of an apparatus for recording an information signal on a record carrier according to the invention for obtaining a clock signal during recording using an auxiliary laser beam. . Fig. \ H the periodic modulation of Figure 7, modified ijemüs.s of the invention;

Fig. T5 shows a record carrier with a periodic track modulation is provided as shown in Fig. 14;

Fi ff. 16 a device for "writing a Record carrier with a periodic track modulation is provided according to the invention, and Figs. 17 and 18 show some explanatory diagrams the mode of operation of the device according to FIG. 16.

Fig. 1 shows a possible embodiment of a recording medium in which the principle according to the invention can be applied, wherein in Fig. 1a a plan view of this recording medium, in Fig. 1b a part of a track h of this recording medium on an enlarged scale and in Fig. 1c a synchronization area of this. Part is shown in glazed-Össertem scale. The recording ■ recording trägerkörpe.r 1 is with a spiral-shaped

Sf) Hr h provided. This track h is in a multitude of ^3! > Sok Loren 7> e.g. 128 per revolution -, - subdivided. Every sec. 1 for 7 contains an information area 91 which is intended to receive coded information in the form of information, and a synchronization area 8.

To ensure that the digital information is written in a precisely defined path, track h acts as a servo track. For this purpose, the information areas 9 of the sectors 7 have an amplitude structure according to FIG. 2. This FIG. 2 shows a small part of the section along the line 2-2 ^f in FIG. 1a and thus shows a number of track parts lying next to one another, in particular information areas of the servo track k. The direction of the servo tracks k is thus perpendicular to the plane of the drawing. These servo tracks h, in particular the information areas 9 ′, are therefore provided as grooves in the substrate 5. This makes it possible to have a beam of radiation directed onto the recording medium for writing digital information coincide precisely with this servo track k , in other words to regulate the position of the beam of radiation in the radial direction via a servo system that controls the light reflected from the recording medium The measurement of the radial position of the radiation spot on the recording medium can correspond to the systems used for optical recording media provided with a video signal and as described in "IEEE Transactions on Consumer Electronics". November 197ö, P. 3P7.

In order to be able to record digital information, the recording carrier body is provided with a layer a material 6 is provided which, if it is suitable Radiation is exposed, an optL.sch ilo tek tie rable ajIorung learns. In principle, it would only be necessary that Information areas 9 of the sectors with such Layer to be provided. In terms of production, however, it is a ' subjects, the entire recording medium surface with one such layer too. Mistake. This layer 6 can for example consist of a thin layer of metal such as tellurium. This metal layer can be melted locally by laser radiation of a sufficiently high intensity, so that locally this information layer 6 receives a different reflection coefficient, so that when scanning an on oiiiu such way inscribed information track by means of

·: I ·: ■: · :: - ·· 3U5128

PHN 9886 gf 24-3-1981

of a readout radiation beam one of the recorded Information corresponding amplitude modulation of the reflected Radiation beam is obtained.

The layer 6 can also be in the form of a double layer made of .under the action of incident radiation - contain chemically reactive materials, e.g. aluminum au Γ iron.

At the point where a high-energy radiation bundle 1 hits the plate, FeAl / - is formed, which badly reflected. The same effect results from a double layer of bismuth on tellurium where Bi_Te " is formed. A simple layer of tellurium can also be used.

By using the as a groove in the sub— strafc 5 formed servo track of the write radiation spot . coincides exactly with this servo track, in particular • During the scanning of an information area, the digital information modulating the write radiation beam becomes exactly in the "20 information area coinciding with this servo track".

As can be seen from the above, the i'Viv (l <m users bcs timmteri recording media, in which no information has yet been written into the information areas, contain a groove structure in these information fields within the sectors.

Such a recording medium also contains within each sector a synchronization area implemented in an optically detectable relief structure 8. Fig. 1b shows a part on an enlarged scale a track 4, from which the sequence of a number of information areas 9 and synchronization areas 8 emerges. The synchronization areas 8 consist of a lie I i η I "s t i'uk Lur, · d Le of a sequence of depressions in Abwi'i-liHo Lung with. Ordered intermediate areas. .

· '* "Dabo ί Lsi. Ciiö Tiol'u eier recesses in .these

Structure · of the synchronization area greater than the depth der Sex ^ vospur in the information area 9 · This depth of the Deepening is classified according to general visual rules

3U5128

PHN 9886 Xf '. 24-3-1981

depending on the shape of these depressions in the selected readout system is chosen such that an optimal readout of the information represented by the structure is obtained. In which from olrioin Aus * 1 osoHy "low iiu; -iiv <>fvntic;<m becomes, Im" i dem the Si reflected from the recording medium. rah I in, ";!" - bundles from a single Photode fcektor de beküiort, is ,, can be used as depth for the recesses ^1/1 IA are selected, where Λ the waves ength is the radiation beam used Venn here for · depth. If the servo track in information area 9 is selected to be 1/8 or smaller, this servo track has almost no influence on the amount of light detected by the detector.

In order to specify the structure of the synchronization area in more detail, such a synchronization area is shown enlarged again in FIG. 1c, the information layer 6 being omitted for the sake of simplicity. Such a 'synchronous L & n i. i.ontjgobiu I, H on (.IuM I I. ν, ννο i Toi I ι ·, namely a display part IO and an address part L 11.-In the address part 11 is all the information required for controlling the Einclxre ib process When digital information is written in, this information is converted into a series of bits arranged in so-called words. This address part contains information about the word distribution, which defines the positioning of the bit words when writing and the correct decoding of the bit words when reading 11 information about the track number of the corresponding track circumference. This information is applied as a relief structure using a digital modulation technique suitable for the recording medium already all for the positioning of the information as B divided into bit words he series of information required in these information areas contains information in the synchronization area, the requirements placed on the writing and reading device used by the user need to be less strict. By having this continue completely beforehand

11 * V W w

3U5-128 "

PHN 9886 'l /' 24-3-1981

attached information is attached as a relief structure in the recording medium, this recording medium is particularly suitable for mass production, where the usual pressing techniques can be used. FIG. 3 shows in FIG. 3 a to 3d schematically in a longitudinal section through the servo tracks 4 part of such a servo track K with part of the synchronization area 8 and part of the information area 9, FIG. 3a showing such a section 3b shows this section after the writing of digital information 14 in the information area 9 »FIG 3d 15 show the section according to Fig. 3c after information 14 has been written into the information area 9. Fig. 3e shows schematically the signal obtained when reading out the part of the track h _{shown in section in FL 1} -; .. '3d and Fig. 3f κι! if} - (. srlioniutisrh a plan view of part of the track '+ after information is written in a different way than shown in Figs. 3b and 3d ■.

The prepared plate is provided with the servo track k , which is attached in the substrate 5, for example by means of a laser beam. In the synchronization area 8, by modulating the intensity of the laser beam, an in-. Formation-containing relief structure with "pits" 13 can be attached. The whole can then, just like, for the sake of simplicity, the part of the recording medium 1 outside the grooves h, be covered with the reflective informa— (. I oius.si-III eliL .o (It is moreover possible to write information in the information area 9, for example by making holes 14 in the reflective information layer 6 by means of a laser beam. Fig. 3b shows such a written record carrier the holes 14, ■ the same as when reading out, for example by means of a laser beam, this information, it is van. Meaning that the writing

PHN 9886 ^ l 24-3-1981

'45 *

or, if necessary, reading this information is synchronized with the aid of a clock signal via which the synchronization areas 8 can contain information. In order to be able to provide an exactly synchronous clock signal during writing and reading continuously, that is to say also for writing or possibly reading in the information logs 9, according to the invention, the servo-groove 4 is provided with a structure that has a Modulation of the light reflected from the recording medium when following the servo track h when reading or possibly writing causes.

However, this attached structure must be such

that · it does not interfere with the reading of information.

The fact that d4.es is possible is explained with reference to FIGS. H and 5, in which FIG. H shows the arbitrary power spectra of three possible binary information signal modulations and FIG. 5 shows a diagrammatic representation of these modulations.

With a in Fig. 5 a modulation is indicated. Eul.el ;, known as "biphase" modulation. The offered digital Signal converted into a binary signal that represents a logical "one" of the digital signal offered during the Time T / 2 and negative - during the following time T / 2 where T is the bit time of the digital signal offered. A logical "zero" delivers exactly the opposite binary signal, i.e. negative during time T / 2 and positive during the following time T / 2. These Modulation technique results in a binary signal that is a frequency spectrum the energy distribution, as it is in.

Fig. H is denoted by a. The frequency fo corresponds to 1 / T.

A modulation is indicated by b in FIG. 5, known as "Miller" modulation. The binary signal generated with this modulation has a

³ ^ Transition halfway through a logical "one" of the digital signal offered and at the transition between two consecutive J'o Lgoii— the logical "zeros". The frequency spectrum 'of the binary signal obtained using this modulation technique

3U5128

PHN 9886 Λ ** 24-3-1981

• ν «» η

r w m

Ln Fig. h is denoted by b.

Finally, c in FIG. 5 indicates a modulation which is known as "four-phase" modulation ("quad phase"), the bit series of the digital signal being initially divided into ± n consecutive groups of two bits. From each group of two bits rai.t of a duration 2T, a binary signal is derived which has the same profile as the original two bits in a first time interval T and an inverse profile in the subsequent time interval T. The possible bit combinations 11, 00, 01 or TO are converted into the bit combinations 1100, 0011, 0110 or .1001. The bi.na.re signal _o dulationstechnik obtained by this M has a frequency spectrum as' 5 in FLg. k is denoted by c.

From FIG. H it can easily be seen that these modulation techniques have the common property that the binary signal obtained with them does not have any strong frequency components at relatively low frequencies, for example frequencies lower than 0.2 f o. This date is of great importance Benefit in the use of optical recording media and the writing and reading systems used. ¥ ie already indicated, both a servo control to keep the scanning spot precisely focused on the recording medium and a servo control are used in such systems This is of great importance because the control signals required for these servo controls are derived from the radiation beam reflected from the recording medium, which is also modulated by the relief structure of the synchronization area that the frequency spec ectrum of the binary signal stored in the address part does not contain any strong frequency components within the frequency band intended for the control signals. Fig. H thus shows that the frequency band below approximately 0.2 fo can be used well for such control signals. The control signals for the mentioned servo systems ■ can

. ;;. ·! . 3U5128

PHN 9886

• ♦ ο «

e.g. extend up to a maximum frequency value of 15 kHz. Venn for the frequency fο = =; e.g. the value of 500 kHz is selected, it can be readily seen from FIG. 5 that the binary signals a, b or c at the frequency of 15 kHz and below only very weak frequency components exhibit.

From FIG. H it can also be seen that at the frequency 2fo and when the modulation method c_ is used, zero points also occur in the spectrum at a frequency fo. It is therefore possible to provide the recording medium with a clock structure with a frequency 2fo without this interfering with the information signals. Zero points at the frequency 2fo also occur with andei'exi modulation methods. ■■

When using four-phase modulation (modulation c) and when using certain other modulation methods the frequency fo is particularly suitable for this purpose; this frequency corresponds to the bit frequency -, making this four-phase modulation very attractive.

With the modulation method b, a structure with the frequency fo can also be applied in certain cases because the components of the spectrum of the modulation are relatively small at this frequency. Further, it is theoretically possible higher for the structure of a frequency _a i _s 2To corresponding modulation to Scavenge on, NHOR wmm at <Ιοι · practice usually is not realizable. With rucks loIiI. For a maximum information density, the dimensions of the pits 13 and 1 ^, which at a normal speed of rotation of the disk 1 correspond to at least one bit time 1/2 T, are selected as close as possible to the resolution of the writing / reading system used, so that a surface structure corresponding to frequencies higher than 2fo is almost undetectable. With special modulation techniques, zero points in power spectra can also be achieved at frequencies other than fo or 2fo, for example at i / 2 fo.

"Next is one of the applicant earlier

submitted, but not previously published, Dutch Lache patent application no. -8000 103 vcsrv.lo.soji, in iloi ¹ oi.no before-

PHN 9886 1/5 2 * 1-3-1981

■ Λ2 ·

improved modulation technology is described.

Fig. 3c shows a section according to. 3a corresponding section through a recording medium according to the invention, the surface being provided with a relief structure with a height jd at least at the location of the track h. One possibility for producing this recording medium is that the laser is modulated, with the aid of which the synchronization area; 8 and the groove h of the information area 9 herge-μ U ¹ I 1 L aj iicl. In the present case, this modulation in the synchronization area 8 only takes place between the pits 13 by limiting the intensity of the laser beam. found. In principle, however, it is also possible to provide the bottom of the pits with a relief structure. 15 · ¥ ie Fig. 3d shows, can also with the plate

.according to the invention, information is written in, that holes 14 in the relief structure covering Reflective layer 6 are attached.

Fig. 3c shows an example of one obtained Signal when reading out a relief according to Fig. 3d

This signal has miniina at the locations of the pits or possibly holes 13 and 1 h and one of the MUCIIIIIIl-JC) IiSsLi ¹ UlVtIIr (d in Fig. 3c) corresponding amplitude modulation with the frequency fo at the maxima. . The modulation of the structure of the holes 1 ^ - hardly contributes to the signal because it hardly reflects any light due to the removal of the reflective layer 6. In this connection it should be noted that it is also possible, for example, to apply a non-reflective layer 6 on a reflective substrate 5, which is locally removed. As a result, the modulation with the frequency fo can be read out well precisely at the points 14 where the non-reflective layer has been removed.

In Fig. 'Ja.- 3d the pits 13 or given- •' 5 jioii (': vl Is cl.i u Lörlwr] h as continuous holes or ge- fiobcMHMira I Ls pits represent ^ esLel 1 L, thus if it is more than one bit. It is an elongated slot with one of the number of bits connected one behind the other.

3,5128

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AO «t *

speaking length. But it is also possible to attach each bit as a single bit or, if necessary, a hole. 3f illustrates this and shows a track k in which the clock modulation structure is indicated with different hatching. In the synchronization area 8, the pits 13 can then, for example, be in the middle of the maxima or given! "A L Ls miniina of the structure angwbractib and coated with the reflective layer 6 like 3 Lud even I'm LI s', which symbolically through the through this may pits 13 continuous hatching is ai'igedeutet in Inforniationsgebiet 'J. the Infonriationslöcher 14 are attached tion structure in the reflective layer 6 on the maxima and minima of Taktinforma- Alternatively, it is possible -.. like · the infor- ■ tion area 9 3f shows holes 14 ′ to be attached to the base points of the information structure The position of the pits 13 or possibly holes 1 h is not essential in this context, provided that the phase relationship to the clock information structure is fixed and known the information structure is of little importance. Instead of the ν Ln I ¹ * ig. '3 shown rectangular shape, it can very well have a sinusoidal curve which is very well possible in the production of a modular laser beam. It is only important that the clock synchronization structure has an easily detectable frequency component at the frequency fo or, if necessary, 2fo and no strong components within the spectrum of the inscribed or against. ■ if necessary has synchronization or possibly digital information signals to be written in, which is generally the case when the clock information structure d has a fundamental frequency fo or possibly 2fo with only higher-order harmonics; the next following *; Harmonic is then 21Ό or gübenonl'a I Ls Ί Γ ο, the,. . As Fig. h shows, lies outside the essential part of the iHfoJTinationsprektrum.

To illustrate the implementation of the structures according to FIG. 3, FIG. 6 shows one after the other apparently in Fig. 6a a device for producing a recording

PHN 9886 J ^ 24-3-1981

funding carrier according to Flg. 3c, in Fig. 6b - a device for writing information into the recording medium according to Fig. 3c and in Fig. 6c a device for reading of such a recorded recording medium.

In the device according to FIG. 6a, the beam 16 of a laser 15 is projected via, for example, an intensity modulator 57, a mirror 17 and a focusing optics 18 onto a dj-parallel plate 1 in order to there the spiral groove k (FIG. 1) form. The laser 15 is controlled by a circuit 20 which effects the pulsing of the laser 15 in order to make the pits 13 (FIG. 3) in the synchronization area 8. The modulator 57 is supplied by a source 19 with the frequency fo (or if necessary 2fo) controlled in order to form a clock modulation structure in the groove h . As an alternative, it is also possible to modulate the laser 15. The plate 1 is driven by a motor 21 which is provided with a servo control to control the speed, which can emtliaLteii e.g. a Tacliogenerator · 2 ^, a speed reference quo 1 Io 'lh und- oj.rioii Sorvover-Hl.ärker 213. Uni dLe Aurzeicluiuiigsgebie te 8 in the correct place on the plate in the track h and, if necessary, around the To obtain modulation fo in a correct tangential distribution on the disk, the circuit 20 and, if necessary, the source 19 with the frequency fo can be coupled to the servo control.

PHN yöö6

Furthermore, the circuit 29 is controlled by the source 19 to ensure a correct phase relationship between the Ensure synchronization pits 13 and the modulation structure. After this process, the plate 1 -with " the said layer 6 are provided.

6b shows schematically a device with the aid of which the prepared plate 6 is provided with information, the clock modulation structure being read out at the same time. This device contains the threatening plate 1 and a laser 15, whose beam H> iibor ("inoii semitransparent mirror 17 and a focusing optics 18 '* are projected onto the plate 1. A reflected beam 30 with a cell 27 »For example one, a photodiode, is detected and converted into an electrical signal, from which the bandpass filter 28 filters out the component with the frequency fo (or possibly 2fo), which originates from the clock modulation structure installed primarily in track k this signal can also be fed to a phase-locked loop 29, which • improves the filtering, increases the constancy of the clock signal and compensates for any short-term disturbances due to signal interruptions. The output 11 then has the "clock signal. Data information can thereby be input." That the laser beam 1b is pulsed Toruiig modulated by placing a modulator directly in the beam or by as in 6b, the laser 15 itself is modulated with a write modulator circuit 25 which

• the information is supplied via an input 26 and dig tnit is synchronized with the clock signal at output 31.

The reflected beam 6o is converted via the light-sensitive element 27 and a reading circuit 30 ″

• Information available in the synchronization areas read out, this information appearing at an output 32. This reading circuit 30 can also be synchronized with the clock signal at the output 31. Di.cvae information can be used to switch circuit 25 to synchronize and search for the exact position on the disk.

PIlN OSHO "

This information is also used in a servo control (not shown in Pig, 6b) to mount the optics 18 and the mirror 17 in a radial position in order to describe the desired part of the track k and to control the drive of the disk 1; which is symbolically indicated in Fig. 6b by the dashed line 62.

Furthermore, the device can also be provided with a track To Ige circuit 33 which derives a sequence signal from the signal of the detector 27 in order to keep the beam 16 directed to the track by controlling the angle of the mirror 17 on the beam 16, which "is indicated symbolically l th line 61 a." ri.che such FoIgeschaltung is, for example, k in the US-PS 223,187 described: in Fig, 6 by the tyes l. .

Fig. 6 shows a device for reading ■ a written disk 1, which device in • practice, mostly • will be combined with that of FIG. 6b. The device again contains a laser 15, the beam Ί6 of which is projected onto the plate 1 via the mirror 17 and the optics 18. The reflected beam 60 is detected with the photodiode 27 and the electrical signal obtained is passed through the bandpass filter 28 with pass frequency fo and a phase-locked loop 29 tuned to the frequency fo, so that the clock signal with the frequency fo (or possibly 2fo) is available. From the electrical signal supplied by the photodiode 27 , the readout circuit 30 decodes the information contained in the data so that the digital information and the information contained in the synchronization areas 8 are output at an output 3 of the same This readout circuit is synchronized with the clock signal at the output 31. In addition, a tracking signal can be derived from the beam detected by the photodiode 27 with the aid of a tracking circuit -33 in order to control the mirror 17 in such a way that the

Beam 16 exactly follows track k. The motor 21 for driving the disk can be integrated into a servo control system, which, for example, consists of the Tiioliu (jeniii'iitor22, the Bezu, 'jsqiaelle Zh- and the .Servover-

3U51-28

PHN 9886 2ygT 24-3-1981

• 23 ·

stronger 23 exists, be included in order to regulate the speed., This regulation with the AusIeseschaltung 3ü can be coupled. The device also contains a control mechanism 35 »around the optics 18 fails the mirror 17 and the detector 27 - soft structure in Fig. 6c is denoted by 36 - in the radial direction move so that a certain part of the plate can be read out under control. one Input 37 of the control mechanism 35 introduced information ■ 10 tion as well as under the control of the output 32 of the reading circuit 30 information obtained from the synchronization areas. · ■

The clock information structure that is in the track attached may take many forms.

7 shows some examples in this context.

Fig. 7a shows schematically a track 4 in which the clock information is brought as a change in height - symbolically indicated by dashed hatching - e.g. with the help of modulation of the intensity of the laser beam writing track k ; Fig. 7b shows track 4 , in which the clock. ™ information is attached as a change in the width of the track.4, for example by modulating the focusing of the laser beam, for which purpose, for example, the objective T8 (FIG. 6a) can be regulated by means of the device 59 (FIG. 6a) - A combination of width and depth changes is also possible, which in practice will often be the case with modulation of the intensity or, if necessary, focusing of the laser beam - and FIG. 7c shows track 4 in which the Radial change in the position of the track 3 "is attached, for which purpose, for example, dex 'angle of the spindle 1.7 (Fig. 6c) to the beam 16 by means of the device.

58 can be modulated · Dnbo.i. wuison »11.1 ο (juvu.» J. (y (. »ii ΛΙ> -

V conversions have a period length Lo, which is equal to Lo = -, where V is the tangential speed of the plate 1 at the relevant point and f represent the frequency of the desired clock signal, this frequency f a Zero point in any frequency spectrum to be recorded Data information, e.g. at. Four phase modulation

PHN 9 886 & ϊ 24-3-1981

dor I'VoqutMiv: I'd, (l ' ^A ig, 4o mid "3c) oritspi ^ iclit.

One of the possibilities for obtaining a track Talge signal is the application of a radial "wobble""in the groove-shaped track, for example by controlling the mirror 17 (FIG. 6a), ie a radial displacement with a wavelength that changes sinusoidally, for example the disk, which, when played back at normal speed, generates a detected change in light intensity by the detector 27 (FIG. 6), the frequency of which is outside the spectrum of the data information, i.e. below the frequency 0.2 fo (FIG. 4), as for example in the said US-PS h 223 187 is described.

From this signal component, for example, with synchronous detection, a measure for the deviation of the center of the detector with respect to the center of the track k can be derived. Such a radial wobble can be structured with a T;> k tinoduLa tion structure, for example with the one shown in FIG. Yes. clock modulation structure shown, and this combination is shown in Fig, Jd. shown. A special combination is obtained when the wobble is given a wavelength on the disk which is equal to the clock modulation structure and has a fixed phase relationship, which makes synchronous detection superfluous.

Fig. Each shows such a structure in which a depth modulation structure (indicated by alternately hatched and non-hatched areas) in the track h niLt oiiiüitUibel over 90 ° (equal to a quarter of the IOr iod «diestii 'SLrukfcur) vtvr. Schnhftnen 'radifilnn, I.agpmänrif * - run (j, which can be generated with the device according to Fig. 6a by modulus of the mirror 17 to the beam ³ ^ 16 by means of the device 58. If the depth modulation structure is selected such that the "shallow" coincide parts of these modulations to the surface of the disc-shaped recording medium 1, remaining from the servo track k or the order in mutual tangential intervals equal to the said distance Lo lying and asymmetric in the radial direction of pits. Fig. Jf shows an example of such a track k. '- ■

m »· α ee * <3.«

O#. _o »Ο wd, *

PHN 9886 Ti 2h-3- 1081

8a shows the principle of the reading part of a device for writing data information into or, if necessary, for reading data information from a recording medium according to the invention, FIG I shows. The device contains a photodetector 27 ' along which the track k moves. The signal which is emitted by the detector 27 'has a spectrum shown in FIG. 8b with, in the present example, the spectrum of a four-phase modulated signal Sd and a clock signal Sc. The clock signal Sc is separated by means of a bandpass filter 28, which is preferably a phase

locked loop 2 ° - connects. The clock signal Se / can be taken from the output "} λ . The digital signal.

Sd, i.e. that recorded in the synchronization area 8 Signal and when reading out that in synchronization area 8 and the signal recorded in the information area 9, is detected with the reading circuit 30, which with the · clock signal Sc is synchronized. The read out data signal appears at the output 32. From the "signal" from the detector 27 a radial follow-up signal can also be derived. When writing information in information areas, be O the circuit 30 detects only the information recorded in the synchronization areas 8, which then together with the clock signal Sc of the write circuit 25 is supplied, to modulate the beam of a writing laser 1.5.

When using a low-frequency radial wobble to obtain a radial follow-up signal, the device according to FIG. 9a can be used, FIG. 9b showing the frequency spectrum of the signal detected by the detector 27. When reading out a track h with radial wobbling, a photodetector 27 can successfully be used which is divided into two parts a and b along an axial line. A differential amplifier 41 or an equivalent element supplies the difference between the signals detected by the parts a and b and a summation amplifier 41 or an equivalent element supplies the sum of these signals.

.: 3U5128

PHN 9886. ^ T "24-3-19 81

• ·

The frequency spectrum (Fig. 9b) contains again the spectrum of the four-phase modulated signal Sd, des Clock signal Sc and the low frequency signal Sw brought about by the wobble. In the sum signal makes itself .3 the wobble · as an amplitude modulation with the clock synaLs Sc'as a carrier wave noticeable, which in Fig. 9b by . Soap bands Sc-w and Sw + w is shown which side bands have an amplitude equal to zero if the detector 27 precisely follows the center 45 of the track 4. A filtering

^ this sum signal by means of the bandpass filter 28 results the clock signal Sc and, provided that this filter is not too narrow, also these sidebands. That The output of this band-pass filter 28 becomes the phase-locked Loop 29 is supplied, and at its output 31

¹ ^ the clock signal Sc appears. The output signal of this bandpass filter 28 is also fed to a synchronous demodulator 42 KUtt.'iiimit-üi with the clock signal Sc. This Demodula-I.or Γ Lel'ei'L then the modulation Sw.

The difference signal of the amplifier 40 becomes

² P mi (. CltMii UamlpMSsfilter 38 and the phase-locked loop 39 obtained the frequency of the radial wobble, which is fed together with the output signal of the synchronous detector 42 to a synchronous detector V}. radial follow-up signal can be used, and represents the deviation of the detector 27 with respect to the center of the track 4 indicated in Fig. 9a by the dashed line 45. This radial follow-up signal can then, as is symbolically shown in Figs. 6b and 6c, control the mirror 17.

AIIF same manner as in the apparatus in Fi ₁ ¹ are from the sum signal at the output of amplifier 41.?. 8a obtained the data present in track 4.

With regard to the writing of information, you can

similar measures as in the device according to FIG. 8a can be applied, which also applies to the device according to FIG. 10, FIG. 11a and FIG.

Fig. 10 shows a modification of the device

.-. .I-3H5128

PHN 9886 ** Γ 24-3-1981

ST-

according to Fig. 9, with which better signal separation can be achieved. The detector 27 is also subdivided along a tangential line in such a way that four quadrants a, b, c and d arise, with parts a and b or ο and d on both sides of the tangential line and parts a and c .respectively. b and d lie on either side of the radial line. An amplifier 41 or an equivalent element determines the sum of the signals generated by the parts a, b, c and d, whereby this amplifier is particularly sensitive to changes in the intensity of the beam reflected from the track k and therefore to the data signal Sd ; An amplifier 421 determines the difference between the signals generated by the two parts a + b and c + d lying on both sides of the tangential line, whereby this amplifier 421 in particular for changes in track k in the radial direction and therefore for the clock signal Sw is sensitive, while an amplifier kB determines the difference between the signals generated by the two parts a + c and b + d lying on either side of the radial LLnLc, whereby this amplifier is used in particular for changes in the track k in tangential direction and therefore sensitive to the clock signal Sc.

According to the device according to FIG. 9a, the clock signal Sc is obtained from the output signal of the amplifier k6 by means of the Baid- <e * jt »25 pass filter 28 and the phase-locked loop 29 and the frequency of the Vobbelsig- nals Sw won.

The output signal of the band pass filter 28, which is the wobble signal Sw a! η Amp IL tudoiimodu I a I. i. 011 tics TuU Im L ₁ ", -nals Sc contains, is detected synchronously with the clock signal with the aid of the synchronous detector k2 and delivers the wobble signal Sw as an amplitude change of the deviation of the detector 27 with respect to the center 4-5 of the track .

This signal Sw is detected synchronously with the output signal of the phase-locked loop 39, that is, the ¥ obbelfrequenzen are detected by means of the synchronous detector k3 , whereby the radial sequence signal at the output kh

appears. The output of the amplifier ^ l is from Clock signal Sc synchronized and with the read switch the data signal is obtained.

The effect of the devices according to FIG. 9a and FIG. 10 can be explained mathematically in relation to the extraction of the radial follow-up signal as follows. That from Detector 27 detected signal I is a product of the clock modulation, the wobble modulation and the radial sequence .TeIi I ers what is expressed (apart from the data signal) can be called

I = Ar sin (^ t) sindfw t),

where Ar is a function of tracking error, u> the angular frequency of the wobble signal Sw, uJ_ the angular frequency of the

"C

Pilot signals Sc and t represent time.

Synchronous detection with the pilot signal Sc results in the term Ar sin (vJ t), and the subsequent synchronous Detection with the wobble frequency ^ results in the signal Ar. The distribution of the detector 27 along only one radial Line to ■ the sensitivity for the clock signal Sc to enlarge "can be used in a corresponding manner in the device according to FIG. 8a.

Fig. 11a shows a reading part of a device for reading data from a track h, in which a clock modulation structure and a wobble for obtaining a radial Fo1 gesignals are incorporated, the frequency of the wobble signal Sw being approximately equal to the frequency of the clock signal Sc, while 11b shows the frequency spectrum in which Sd represents the data signal and Sc-w is the term with.: A frequency equal to the difference between the frequencies of the clock signal Sc and the wobble signal Sw, this difference being, for example, 30 kHz, which term thereby it is obtained that the photodiode 27 receives the product · of the wobble modulation and the clock modulation. This term is therefore in the low frequency part of the spectrum and is

35 'almost not bothered by the digital information. The amplitude of this term forms the radial sequence signal. The amplitude is zero when the heart line k $ is followed closely on the track. Then one more of the wobble remains

PHN 9886 H ^ _Λ ■ ■ 2 ^ -3-1981

29 ·

Term with twice the · difference frequency, which · ■ 'term is not used, as well as the wobble frequency itself. The device contains, like the .Vorrichtung according to FIG. 10, an amplifier 41 for supplying the sum of the signals supplied by the parts a, b, c and d of the photodiode 27, from this sum with the help of the bandpass filter h8 the term with the named difference frequency a, is filtered out. With the help of the Synchrondetek ^ t. ors ¹ V), to which this difference frequency is fed, this term is demodulated and, if necessary, a low pass V.) e r-

appears at the output kt \ - the radial follow-up signal. _ The clock signal Sc is generated in the same way as'

obtained in the device according to FIG. 10 in that with the amplifier h6 the difference between the signals supplied by the two halves a + c and b + d of the photodiode 27 is determined and this difference is determined by filtering with the sand pass filter 28 of the phase locked loop 29. ' is fed. ·

The wobble signal Sw is obtained, as in the device according to FIG. 10, by using the amplifier Η ', Ιλ to determine the difference between the signals supplied by the two axial elements a + b and c + d of the photodiode 27 and this is fed to a phase-locked loop 39 via a bandpass! "11 tier 13H.

^ 25 ■ The difference frequency fed to the reading circuit detector k3 is obtained by feeding the clock signal Sc and the wobble property Sw obtained in this way to a synchronous detector hZ , after which the signal obtained with the mentioned difference frequency is fed to the synchronous detector k3 via the bandpass filter 4 7 .

With the reading circuit 30, which is synchronized with the clock signal Sc, the output signal of the amplifier 4i the data signal can be recovered.

When the frequency of the wobble signal Sw is " the frequency of the clock signal is selected is from Fig. 11b it can be seen that the term with the DIffor-ejiziVoiiuen /. simultaneously forms the DC tracking signal. This track signal can then be obtained without synchronous detection.

PHN 0 886 ' Zf * sr \ 24-3-1981

The phase between the two track modulations should not be equal to 0, because if both modulations are in phase are, only one modulation can be distinguished .kanu. An optimal phase difference is as found was, 90 °.

Such a structure is shown in Figures 7e and 7d and this can be read out with the simple readout circuit according to FIG.

In the device according to FIG. 12, the photodiode 2'7 is divided into two radial halves a and b for optimal detection of the clock signal Sc which appears at the output after the amplifier k6 has been used to determine the difference between the two halves a and b determined signals supplied, this difference signal is filtered with the bandpass filter 28 and then fed to the phase-locked loop 29 ·. By filtering the output signal of the amplifier 46 with a low-pass filter h9 , the radial follow-up signal appears directly at an output kk. Da ^- S digital signal is obtained from the difference signal with dec Les'esohal tuiig 30, which is synchronized with the clock signal Sc. As an alternative, it is also possible to obtain the data signal and the low-frequency subsequent signal from the sum of the two halves.

With respect to writing tracking of data signals, the devices according to FIGS which are expanded with the clock signal Sc and the signal read out from the synchronization areas is synchronized, as shown in Fig. 6b apart. --OHOtZt is. ·

The top was always a single detector 27 nii.sfjR (iaiii; fin, which .detects the ref lelct.Lort beam 16 (Fig. 6). It can be questionable, especially with high bit frequencies when writing file information in the information areas 9 »which writing process in relation to the readout with a relatively high-energy Laser beam is carried out, the clock information from the beam reflected between every two writing pulses

PHN 9886 3 «er 24-3-1981

^s to regain. Since often to be able to detect the written data signal, a subsequent laser beam is used in such cases the device according ■ "can ig. Find 13 application in which the track k, which relative to the detector 27 in the direction of arrow 63 The mirror 17a and 17b and the optical systems 18a and 18b are obtained by means of a beam splitter 68, for example. A modulator can be arranged in the beam 16a to modulate the beam 16a. This device contains a photodiode 27 'which, with regard to the reading out of data signals and sequence signals, is completely analogous to the devices according to one of FIGS. The device also contains a photodiode 50 for detecting the reflected following beam 16b, which is projected onto the track at some distance behind the beam i6a The reading process as well as when reading out the synchronization areas 8. is carried out by the signal detected by the photodiode 27 via an amplifier (not shown in this figure for the sake of simplicity ) (e.g. k6 in FIG. 11a) and a bandpass filter (e.g. the phase-locked loop 29 trains leading I. is obtained, the clock signal Sc. In addition, this clock signal is also obtained in a similar manner from the signal detected by the photodiode 50 via a bandpass filter (not shown) and via a phase-locked loop 501, in particular during the writing process, but this clock signal is obtained in relation to the signal via the photodiode 27

3u obtained clock signal is delayed. The output signal will be is fed to the output 31 via a delay device 5I. The delayed clock signal is used in the phase comparator 52 with the phase of the Gewonrrenexi from the photodiode 27. Clock signal compared, and a switch 53 is the

"" Delay device 51 set in such a way that the about the VerssögerunRavui direction 51 Vörzii ^ oi'l.e Takts r, ", um.I of the photodiode 50 to that obtained via the photodiode 51 Signal is in phase. When reading out the synchronization

. «. .: 3US 128

PHN 9'8Ö6. ^ λ »24-3-1981

In areas 8, the switch 33 is closed and the delay circuit 51 is set in such a way that the clock signal "of the photodiode 50 delayed by this delay circuit 5I is in phase with the clock signal received via the photodiode.27. When writing data in il Lo 1 ril'ornia tioiis ('; ebie te 9 is dex * switch 53 open and the clock signal is obtained from the reflected auxiliary beam 16b via the photodiode 50 and delayed with the delay circuit 51 for the time set when reading out the synchronization TO area 8. The switch 53 is operated in response to the "command of the synchronization signal read out from the synchronization areas 8 by the reading circuit 30.

It should be noted that the writing of information with unit pits, ie that the information with individual detectable changes in the surface structure. door of the recording medium is recorded, as in Fifi. Each LIt is allowed to be '3-1', a frequency component with the croqiience that results in '2Co in the spectrum (Fig. K) of the signal that has been read out. This need not be questionable for the application of a clock modulation rule, because this clock modulation, if it has a frequency equal to 2fo, can be used when writing the information and if a correct phase relationship to the clock signal is maintained when writing, " when reading out coincides with the component · 2fo due to "the use of unit pits. When using four-phase modulation (FIGS. 4c and 5c), the clock signal will have a frequency equal to fo and in this case said component with the .30 frequency 2fo is not disturbing.

There can be many disturbances, such as local foil solder in the plate 1 odex vibrations, that when writing the laser beam 16 - while it is in ο Liioiii bo.st Liiiinten sector <) (Fig. 16) with a track the trail leaves and strips over an adjacent track, it overrides the sector in question, - - is the input 'busy write ³ ^ of-already described, or must be enrolled still be -.-. Although the radial follow-up mechanism -

PHN 9886> <f. 24-3-1981

• 33

must be able to bring the beam back on track, this situation is undesirable because then it is not only the sector to be described that is incompletely Is written, but also the neighboring sector (dio

neighboring sectors) are considered lost must (must). This situation should be avoided. The "write" process is intended when leaving a 'track through the - The beam must be stopped so that no adjacent tracks are damaged. The sector 9> in the at this point in time is then considered lost

and the information must be in a new sector 9 on α. new ones are written. A reliable method for timely detection of a tracking error can be large with respect to FIG. 1 h and plate 15 described are performed -1. Preformed tracks k with clock information are attached, as described with reference to FIGS. 1 to 13. The clock modulation is applied in such a way that points with the same phase are aligned along a line A deviating from line B in a radial direction. As a result, the phase of the clock structure in track hh has a positive phase difference with the clock structure in track k * and a negative phase difference with the clock structure in track 4 ".

** p 25 If the beam 16 leaves the track k ', will, Je.

according to the direction, a positive or negative phase shift in relation to the uniform phase change. occur when following the track k in the read clock signal. This phase shift can be detected from the _amplitude-U nd same can be derived a signal indicating an inadmissible track deviation to stop the write operation. From the polarity of the. Information about the direction of the tracking error can be derived from the phase shift, this InJ.'oriuat.ion could be used to return the beam 16 in time to the track h so that the writing process can be restarted in the following sector 9.

In Fig, k there is always a phase difference of ⁽ JO °

.: ".: ..... _: 3U5128-

tr ■ * * *

24-3-1981

observed between the clock modulations of the successive tracks. This is the optimal phase relationship. Because a phase difference of 0 ° or 36O ⁰ iergibt no error signal while lost in a phase difference of 18O ° directional information. An additional. The advantage of the plate according to FIGS. Ik and 15 is that the influence of crosstalk during reading is reduced by the shifted phase.

Fig. Ί6 shows an embodiment of a Vorricht.inifv for describing a plate according to Figs. 1 and 15 K · For the principle of the effect is made to the description. FIGS. 1-13, in particular FIGS. 6b and 12, are referred to, corresponding reference numerals being used.

In contrast to the situation with the device according to FIG. 12, it is assumed that the tracks k, k * , k " ... have a low-frequency wobble, as described, for example, with reference to FIGS. 9 and 10. The device 33 for 6b, the write modulator 25 is provided with an input 70. A signal at this input stops the write process.

The phase locked loop 29 is in the device; 16, with a synchronous demodulator 7, which compares the clock signal obtained via the filter 28 with respect to the phase with the signal received from a voltage-controlled oscillator JZ , this oscillator 72 is controlled by the output signal of the demodulator J \ obtained via the low-pass filter 73. The output signal of the oscillator 72 forms the clock signal Sc, which is output at the output 31. The output signal of the demodulator 71 is a measure of the instantaneous phase difference between the output signal of the oscillator 72 and the clock signal obtained via the filter 28, which originates from the disk 1.

-If, as in Fig, TYes. is shown, a data track T in the track. + is written in a specific sector 9 between synchronization areas 8 (see FIG. 1), a uniform clock signal Sc is obtained.

3145Ί28

PHN 9886> er 2 ^ -3-1981

The output signal of the demodulator 71> class Ln "Pig. 17t> is then almost equal to zero. If the writing track T shifts from track k to track k 'for any reason, the output signal becomes.

of the demodulator 71 to increase the oscillator 7 <- nacli / .uregeln. The Schreibvorgaiig should interrupted weiHloxi before ■ passes "the track T on the adjacent track '+' This can _t;.. On the amplitude of the output signal of the demodulator can be detected 71 Similarly, the data track T can be removed in the other direction, which, as shown in Fig. 17b

is, leads to a negative output signal of the demodulator ^ _- . Behind the demodulator is a low pass 7h. a window detector 75 is arranged, which detects whether the output signal of the demodulator 71 exceeds predetermined limits + Sd or -Sd (Fig. 17t>), and then generates a signal at the output 76 (Fig. 17c), which via the input 7- 0 of the writing modulator 2 ¹ J "the writing v (> r, <;; nJi ^ stop! ..

The Tiül'pasa 7'l serves; in addition, because "Syyl.oin door Sl.öi- · - to make impulses and the like un sensitive IL cli, and ίν ^ ίϊ'ΊκΜίΐ'ΐι-if can be combined with the low pass 73 ', which is with the' dashed Line 77 in FIG. 16 is indicated. When the data track T leaves the track k , the tracking signal will also have a greater positive or negative value than in the case of undisturbed tracking. It is possible to detect this via a window size detector 78 and to combine the output signal of this detector with the output signal of the window detector 75 in a combination circuit 79; this possibility is shown in Fig. 16 by dashes. This double safeguarding may be desirable in order to ensure the operational safety of the v.ti cm-IiöIumi system. The protection via the spurt "ο Lgesignn I." is less suitable per se than the protection via the phase endLiTerenzsignaL at the output of the demodulator 7I because, as FIG. 18 shows, the tracking signal is a low frequency

or

^p Part C of the spectrum and the said phase difference signal takes its information from a high-frequency part E of the spectrum, while disturbances such as changes in reflection of the plate and small defects in the surface of the plate, which

PIiN <) 886. £ 3 "24-3-1981

.36.

would not lead to a lane change according to Fig. 17a, mainly also in a low-frequency part D of the spectrum occur.

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Claims (1)

•• ■ • I. ":": .X '\ ■ 3U51? R PHN 9886 25-3-1981 PATENT CLAIMS: 1 J device for recording information on ■ a recording medium, which is a disc-shaped substrate with a radiation-sensitive information layer and with a spiral or concentric look Track pattern arranged information areas is provided, this device with a light source, an optical system for directing a beam of light the information areas of this recording medium, one Axif display circuit for modulating the light beam Lh ^ Depending on the digital signal leaning on ζ uz ο an optical system with a detector for Dctokl-iot'cii a radiation reflected or possibly transmitted by the recording medium is provided, characterized, that for reading out a recording ·. . . '$ · "^" carrier in which the information areas are a periodic X track modulation, the period of which corresponds to a frequency, \ in which the range of services to be recorded or optionally recorded digitally coded information has at least almost a zero point for which · Generation of a clock signal with bit frequency for synchronization of the digitally encoded information when recording and / or reproducing, this periodic track modulation being attached to the track in such a way that dots this track modulation with the same phase of track '. to track along a line deviating from the radial direction, so that the track modulation of each track as a function of the circumferential angle of the disc-shaped recording medium in one radial direction always leads in phase with respect to the track modulation of the track adjoining it in this radial direction and in the other radial direction in the phase always opposite the track modulation of the 'in the other radial direction on it * - PHN 9886 Ä. 25-3-1981 trailing bordering track, the device includes: a band pass filter for filtering a signal with a frequency, (Ii ο duroli (Ii ο period dor periodic track modulation be.s I. i irmit LhI, from this detected radiation, where this signal · as a clock signal of the write circuit for the Synchronization of the information signal to be recorded is fed with the periodic track modulation, so that the information to be recorded in a fixed Phase relationship to this periodic track modulation ¹ ^ is drawn, as well as a phase comparison circuit for monitoring the ■ instantaneous phase of said filtered signal in order, if the phase deviates to a certain extent from that of a signal with "uniformly changing phase, a signal to" inter- ¹ '«to generate the recording process. : i. Apparatus according to claim 1, characterized in that Lehnet. that the "phase comparison circuit is incorporated into a phase-locked loop, this phase comparison circuit said filtered signal and that originating from an oscillator controlled by the output signal of this phase comparison circuit via a low-pass filter Signal are fed, the output signal of this phase matching circuit to a window detector is fed.
25th 3 · "'device according to claim 1 or 2, with optical means for aligning one with the one to be recorded ! Information modulated light beam on the information (iobiote and for directing an auxiliary beam at the Informat Lons / rebiote behind the modulated beam for readout ' the information recorded by the light beam modulated by the dome is provided, characterized in that the auxiliary beam for reading out the periodic track modulation for the Generation of the clock signal to synchronize the writing of information with the other beam, and for the Feeding the signal to the phase comparison circuit is used. PHN 9886 · · 3 * 'ΐΗ -'} - Λ 98 I. Information modulated light beam on the information areas and for directing an auxiliary beam on the information areas behind the modulated beam for reading out the information recorded by the modulated light beam is provided, characterized in that the auxiliary beam for. Reading out the periodic track modulation for .the Generation of the clock signal in order to write information to synchronize with the other beam, and used for feeding the signal to the phase comparison circuit will.