KR890002237B1 - Optical recorder provided digital information signal - Google Patents

Abstract

The method of recording a binary information signal on a data storage medium uses an active layer responding to radiation to permit recording of data by control of the incident radiation by generating radiation pulses of fixed intensity and duration at controlled intervals. The binary data stream is converted to a binary modulted signal using Miller modulation which permits only 2,3 or 4 bit cells per binary interval. To increase the data storage density the recording radiation is modulated to produce an impulse between the bit cells of the Miller encoded signal, thus generating one impulse for 2 bits, 2 for 3 bits, and 3 for 4 bits.

Description

Digital binary information signal recording device and control device

1, 2 and 3 show signal waveform diagrams and associated recording mark diagrams for illustrating the method according to the invention;

4 is an exemplary view of an apparatus for obtaining pulses of radiation required for the method according to the invention.

5 is a signal waveform diagram of the apparatus of FIG.

Fig. 6A shows a recording carrier in which information can be recorded in accordance with the present invention.

FIG. 6B is a detailed view of the recording carrier of FIG. 6C, 7, 8A and 8B in FIG. 6A on an enlarged scale.

9 shows an apparatus for recording information on a recording carrier.

* Explanation of symbols for main parts of the drawings

S, S ': Record mark I, I': Information signal

K: clock signal 1: delay device

3: radiation source 15: laser

29 phase locked loop 30 readout circuit

33: tracking circuit

2 이다.The present invention relates to a method of recording a binary information signal on a record carrier having a radiation sensing information layer, wherein the recording pattern is recorded by the generation of radiation pulses of fixed period and intensity at selected instantaneous values of successive instantaneous values corresponding to the bitset. Coincident with the information signal formed into the information layer of the carrier, the radiation pulse having energy for forming a unit recording mark on the recording carrier, wherein the information signal has a series of at least consecutive bit cells of the same first shape; Bitcell, where n

2

The invention also relates to a record carrier provided with a digital information signal stored in an information track, said information signal comprising a series of bit cells, wherein at least n consecutive bit cells are of the same type and of the first type. A series of bit cells is always represented by multiple unit record marks in the information track.

2 인 적어도 n개의 연속한 비트셀이 동일한 형태로 되어 있는 일련의 비트셀을 포함하고 있다.The invention also relates to an apparatus for performing the method for recording a digital information signal, comprising: an optical system for focusing a radiation source and a radiation beam emitted by the radiation source to a radiation sensing information layer of a record carrier; And a control device for controlling the radiation source according to the applied binary information signal, wherein the information signal is n

At least n consecutive bitcells, which are two, contain a series of bitcells of the same type.

It is of great interest to date a record carrier with a radiation sensitive information layer, which is mainly due to the large amount of information recorded on the record carrier, for example data information and digitalized video and audio information. This is because it has a very high memory capacity.

The information layer of such a record carrier contains a material that exhibits a physical reaction upon exposure to a radiation beam of a suitable intensity, so that by adjusting this recording ratio a corresponding recording pattern is formed on the recording carrier. The information layer may consist of a metal, for example tellurium, which is locally melted by heating as it is exposed to the radiation beam. Alternatively, the information layer may comprise, for example, a double layer structure of a substance which chemically reacts to the bismuth or ions on tellurium under the influence of a radiation projection beam. Another suitable material may be a magneto-optical material such as, for example, Gd-Fe and cobalt ferrite. The material selected for the information layer is such that a recording pattern corresponding to the information signal is formed from the material by exposure to the modulated radiation beam, which is irrelevant to the present invention.

For optimal use of the storage capacity of the record carrier, the information signal is usually modulated in a special way, i.e. the source coding of the information signal is converted to channel coding in the case of the recording carrier in the case of the invention, which channel coding Applies to suit the characteristics. In this respect, the parameters are important, and in particular,

(1) The maximum frequency of the recorded information signal is due to the limited transmission bandwidth of the record carrier and the recording and reproducing apparatus.

(2) The low frequency signal component of the information signal, which is due to the crosstalk between the low frequency servo signal and the information signal which are often used in a reading device for an optical record carrier for focusing the reading spots on the information track and focusing the reading spots.

(3) The maximum number of consecutive bit cells of the same type, since the clock information is often required to be separated from the information signal during the write carrier and the read.

Dutch patent application No. 8000121 (PHN09666) describes a method of the type mentioned at the outset and also describes channel coding. In addition, the patent application described two methods for recording an information signal on a recording carrier in accordance with channel coding. According to the first method, the light beam is precisely modulated in accordance with the digital signal so that a variable-length recording mark is recorded on the recording carrier, which corresponds to a period in which the information signal takes one digital value. According to the second method, the light beam is pulsed, that is, a radiation pulse of fixed length and magnitude is generated for each bit cell of one type in the information signal.

These radiation pulses on the recording carrier produce respective adiabatic recording marks, unit recording marks and a certain number of recording marks, which in turn represent one particular type of bitcell. Compared to the first method, this second method has the advantage that the dispersion in the radiation source is small and also has a good effect on the life of the radial source.

In addition, the Dutch patent application describes channel coding in which at least two or more bit cells are always the same. As the minimum number of consecutive bitcells of the same type, n, increases, the maximum frequency of the binary information signal decreases. It is evident that this has a beneficial effect on the storage capacity achievable and the required bandwidth of the recording and playback apparatus.

It is an object of the present invention to provide a method in which a very high information density is achieved on a record carrier without requiring extremely stringent requirements of the recording equipment as mentioned at the outset, and also further reduces the dispersion of the radiation source.

n (m과 n은 정수), 또한 다수의 연속적인 방사펄스에 의해 발생되고 최소한 연속적인 다수의 단위 기록마크에 의해 매우 많은 수의 동일한 제1형태의 연속적인 비트셀이 표현되는 것을 특징으로 한다.For this purpose, the present invention is characterized in that the radiation pulses are dimensioned such that the unit recording mark formed by the radiation pulses represents m consecutive comparison cells of the same first type, where 1 <

n (m and n are integers), which are also generated by a plurality of consecutive radiation pulses and are represented by a very large number of identical first type consecutive bitcells, at least by a plurality of consecutive unit record marks. .

The present invention is based on the recognition of the fact that the minimum size of a single write mark is in fact limited. This depends on the material parameters of the information layer and on the properties of the optical component which causes the radiation beam in the recording device to be focused on the information layer.

n 기록캐리어의 기억용량이 실질적으로 증가될 수 잇다. 본 발명의 수단에 의해 얻어진 증가분은 m의 값에 의거한다. 본 발명에 의한 방법의 양호한 실시예는 m=n인 것을 특징으로 하다. 이것은 기억용량의 최대증가를 제공한다.In an encoding system in which the number of consecutive bitcells of the same type is larger than one bitcell, if the unit record mark is related to m bitcells rather than one bitcell, 1 <m

n The storage capacity of the recording carrier can be substantially increased. The increment obtained by the means of the invention is based on the value of m. A preferred embodiment of the method according to the invention is characterized in that m = n. This provides the maximum increase in memory capacity.

(m과 n은 정수)인 제1형태의 m개의 연속적인 비트셀을 표시하는 것을 특징으로 하며, 또한 최소한 연속한 단위기록 마크에 의해 매우 많은 수의 상기 제1형태의 연속적인 비트셀이 표시되는 것을 특징으로 한다.In the recording carrier according to the present invention, one unit recording mark is 1 &lt; m

(m and n are integers) to display m consecutive bit cells of the first type, and a very large number of consecutive bit cells of the first type are indicated by at least continuous unit recording marks. It is characterized by.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a schematic diagram showing the first transformation of the method according to the invention using a Miller modulation scheme.

1A shows a bit string of a digital signal comprising a series of logics "0" and "1". According to the Miller modulation method, the digital signal is converted into a binary information signal as shown in FIG. 1B. In accordance with the Miller modulation scheme, the binary information signal represents a transition between two consecutive logic "0s" and a transition in the middle of logic "1" of the applied digital signal.

A unique feature of the Miller modulation is that the length of time that the binary signal has one of two values in succession can take a certain number of discrete values whose value matches the formula nT. T is the greatest common divisor of these discrete values, and in Miller modulation it corresponds to half the bit length of the original digital signal. In this Miller modulation the parameter n can take on values 2, 3 or 4 as is apparent from the figure. In the following, the time interval T is conventionally regarded as a bit cell.

In order to record a binary information signal on a record carrier with a radiation sensing layer, the radiation beam is modulated in such a way that a recording mark is formed on the record carrier, the sequence of which represents the binary information signal. For this purpose this radiation can of course also be modulated directly with the binary information signal to be recorded.

In addition, Dutch Patent Application No. 8000121 describes the possibility that the unit record mark is recorded on the record carrier by the pulsed action of the radiation source. For this purpose, as shown in FIG. 1C, one radiation pulse is generated for each bit cell T denoted by a logic " 1. " Each radiation pulse has a sufficiently high energy to yield a unit write mark corresponding to one bit cell on the record carrier.

Thus, a pattern of a fixed number of recording marks S (shown in FIG. 1d) is formed on the recording carrier, the recording marks are regarded as unit recording marks and the patterns represent binary information signals. In practice, the dimensions of these unit recording marks, i.e., generally the diameter of the round mark, are limited to the minimum value. This minimum depends on the parameters of the radiation-sensitive material and on the properties of the optical element used for recording. For example, a radiation-sensitive material is a material that melts when exposed to radiation of sufficient intensity, and a certain minimum radiation energy is required because of the reliability of the write-in process, where the radiation energy is a unit record mark of a specified size through the heating of the material. To form. If a much smaller unit record mark is required, the recording process becomes unreliable. The optical components installed in the recording device determine the diameter of the writing point at which the information layer radiates upward. This writing point can be given a very small diameter by the focal length, which results in the high storage capacity of the optical record carrier but in practice is also limited. Indeed, for example, the writing point diameter must always be maintained irrespective of the plane processing defect of the information layer, among which strict conditions are imposed on the flatness of the information layer and the focusing control of the recording apparatus. Moreover, it should be noted that even if a very small number of unit record marks are formed on the recording carrier by a complicated technique, this is of importance for the reading device in which the recording carriers are entangled. The reading device must be able to reliably read the unit write mark, which imposes very strict requirements on the optical components and control devices used, for example track devices and poker devices. In particular, if the reader is a consumer product for reading digital video or audio information, for example, the imposed requirements will be limited. As a result, the diameter of the unit recording mark S shown in FIG. 1d is practically limited to a specific minimum dimension.

n 인, 2진정보 신호내의 동일한 형태의 m개의 연속적인 비트셀에 대응하는 단위기록 마크를 기록하는 것에 제한된다.This diameter with respect to the modulator determines the storage capacity of the record carrier. The present invention aims to increase this memory capacity in a simple manner. Instead of recording the unit recording mark corresponding to one bit cell, 1 &lt; m

It is limited to recording unit recording marks corresponding to m consecutive bit cells of the same type in a binary information signal of n.

As mentioned earlier, in the case of Miller modulation, n = 2, so m = n = 2 for this modulation system according to the present invention, and as a result, one unit write mark S 'corresponds to two bit cells. Also many successive bitcells of the same type are represented by at least a plurality of adjacent unit record marks.

When the method according to the present invention is applied to the binary information shown in Fig. 1b, this results in a pattern of unit recording marks shown in Fig. 1f, for example, in which the radiation pulse shown in Fig. 1e is shown. Is needed.

The comparison of the pattern of the unit recording marks shown in Figs. 1d and 1f is, for example, the first two unit recording marks S in Fig. 1b are replaced by a single unit recording mark S 'in Fig. 1, and It is then shown that three consecutive unit recording marks are replaced by two partially overlapping unit recording marks S 'as shown in FIG. 1f. The dimension of the unit recording mark shown in FIG. 1f is selected so as to enable direct comparison with the pattern shown in FIG. 1d, and the unit recording mark K 'is actually selected to be the same as the recording mark S in FIG. At this time, it is apparent that the pattern shown in FIG. 1f is reduced to the pattern shown in FIG. 1g, thereby doubling the storage capacity of the recording carrier of the method according to the present invention.

In addition to the Miller coding described above, there are several other codes, where the minimum number of consecutive bitcells of the same type is greater than one. These coats include a serial code in which data bits of a digital source signal are successively converted into bitcells of a binary information signal, and so-called block codes in which words of the digital signal are converted into explicit types of bitcells of a binary information signal. do. An example of such a code is Dutch patent application No. 8004028, so-called EFM (8-14 modulation), which code is used as a modulation for recording audio information on an optical disc in a so-called compact disc audio system. In the case of the EFM modulation, the generated binary information signal is characterized in that at least three consecutive bitcells have the same shape and the maximum is 11. Numerous alternatives to the method according to the invention will be described with reference to FIG. 2, which shows the signal obtained by the EFM modulation.

2A shows a binary signal. The radiation pulse used for recording is such that a unit recording mark S having a minimum number m = n = 3 of three bit cells, that is, consecutive bit cells of the form " 1 "

Multiple bitcells of type "1" may be recorded in a method as shown in FIG. 1 by a plurality of consecutive radiation pulses spaced at intervals of one bitcell, which in turn is shown in FIG. The pattern shown is generated by the radiation pulse shown in FIG. 2b.

In the pattern of radiation pulses shown in FIG. 2d, all second radiation pulses of the sequence in which a plurality of consecutive bitcells of type " 1 " should be recorded are suppressed except for the last radiation pulse of such a sequence.

It can be seen from the pattern of the unit recording mark corresponding to the radiation pulse shown in FIG. 2C that the pattern clearly represents a binary signal. The advantage thus obtained is, of course, that the dispersion of the radiation source is reduced.

In addition to the first and final radiation pulses whose presence and position are compulsory, the pattern of radiation pulses shown in FIG. Pulses, which are realized by placing intermediate radiation pulses at equal intervals relative to the first and final radiation pulses.

Finally, in the pattern of unit recording marks shown in FIG. 2i, a series of consecutive bitcells of type " 1 " may be represented by a plurality of non-overlapping consecutive unit recording marks, so that the required number of radiation pulses ( 2h) is further reduced.

It is evident that by means of logic circuits the desired form of radiation pulses can be derived from the binary information signal in a simple manner.

The dispersion is another matter and the choice of the pattern of radiation pulses depends on the desired reliability. If the number of single write marks is reduced, this ultimately leads to a decrease in reliability.

3 shows an alternative to the method shown in FIG. FIG. 3A shows the binary signal shown in FIG. 2A again. However, in contrast to the state of FIG. 2, the unit write mark S now corresponds to two bit cells and thus m = 2. The sequence of radiation pulses shown in FIG. 3B results in a pattern of unit recording marks S as shown in FIG. 3C.

This alternative method also allows the number of radiation pulses to be suppressed, e.g. all the second radiation pulses (except the last pulse) of each sequence will result in the sequence of radiation pulses shown in Figure 3d and Figure 3e. This results in a pattern of the unit recording marks shown.

4 illustrates, by way of example, a logic circuit for deriving a radiation pulse from a binary information signal, and FIG. 5 shows a corresponding signal. This example is based on the binary information signal I in which at least three consecutive bit cells are of the same form and in which a unit record mark corresponding to the three bit cells can be recorded.

In the logic circuit shown in FIG. 4, the binary information signal I (FIG. 5A) is applied to the delay device 1 so that the information signal is delayed by two bit cells (FIG. 5A). The delayed information signal I 'and the information signal I are applied to two inputs of the ANA gate 2.

The third input of this AND gate 2 receives a clock signal K (Fig. 5C) including a pulse in the middle of each bit cell. At the output of the AND gate 2, the pulse train shown in FIG. 5d is generated and the pulse train is applied to the radiation source 3. This radiation source 3 generates radiation pulses for forming unit recording marks corresponding to three bit cells on the recording carry.

Optical components and control systems, such as the focus control device used in this recording apparatus, are applied to the organizational structure on the recording carrier, for example, when there is no track previously recorded on this recording carrier. As an example of this feature of the recording apparatus, reference is made to the aforementioned Dutch patent application No. 8000121, which is incorporated herein.

FIG. 6A shows a possible embodiment of a recording carrier to which the principles of the invention can be applied, FIG. 6B shows on an enlarged scale a part of the track 4 of the recording carrier, and FIG. 6C shows a synchronization area of the track portion. It shows on an enlarged scale. The recording carrier body D is provided with a spiral track 4. This track 4 is divided into, for example, 128 multiple sectors 7 per revolution. Each center 7 comprises an information area 9 and a synchronization area 8 for recording digitally coded information.

The tracks 4 are used as tracks with each other to ensure that digital information is recorded in exactly defined passages.

For this purpose, the information area 9 of the sector 7 has an amplitude structure as shown in FIG. FIG. 7 shows a portion of the cross section taken along the line II-II 'of FIG. 6a, and therefore shows a number of adjacent track portions of the servo track 4, in particular the information area. The direction of the servo track 4 is perpendicular to the plane of the drawing. The servo track 4, in particular the information area 9, therefore takes the form of a groove in the substrate 5. In this way, it is possible to precisely match the radiation beam directed towards the recording carrier with the servotrack 4 in order to record digital information, i.e. radially via a servo system using the light reflected by the record carrier. It is possible to control the position of the radiation beam at. The measurement of the radial position of the radiation spot on the record carrier may be made with a matching system similar to that used for optical record carriers provided with video signals, especially described on page 307 of the November IEEE 1976 Minutes of Consumer Electronics. It is.

For digital information recording, the record carrier body is provided with a layer 6 of material which, upon exposure to the appropriate radiation, makes an optically detectable change. Such a layer mainly needs to be provided only in the information area 9 of the sector 6.

However, manufacturing techniques make it simple to provide an entire recording carrier surface with such a layer. The material layer 6 may comprise a thin layer of metal, such as, for example, delurium. The dissimilar metal layer can be locally melted by laser radiation of sufficiently high intensity, so that the information layer 6 is locally given a different reflection coefficient and as a result the reflected radiation beam is scanned by the engraved information track reading beam. The amplitude is modulated according to the recorded information.

Alternatively, the information layer 8 may form a double layer of a material such as aluminum on iron, which chemically reacts to incident radiation. FeAl ₆ is formed at the position where the high power radiation beam is incident on the disk, which is an insufficient reflector. A similar effect is obtained in the case of bismuth bilayers above with delurium, and Bi ₂ Te ₃ is formed.

It is also possible to use tellurium monolayers. With the aid of a grooved servo track in the substrate 5, the write radiation spot is exactly coincident with the servo track, in particular the digital information modulating the write beam is accurately recorded in the information area coinciding with the servo track.

It is apparent from the foregoing that the user record carrier whose information area does not contain information has a home structure in the information area in the sector. Furthermore, in each sector the record carrier has a synchronization area in the form of an optically detectable relief structure. FIG. 6B shows a portion of the track 4 on an enlarged scale, from which the sequence of the plurality of information areas 3 and the synchronization area 8 is evident. In this case the synchronization and region 8 comprise a relief structure consisting of a series of recesses alternating with the intermediate region.

In this structure of the synchronization area the depth of the recess is greater than the depth of the servo track in the information area 9. The depth of the recess is selected by the general optical law in accordance with the shape of the recess in the selected reading system in such a way that an optimal reading of the information represented by the structure is obtained. In the case of a reading system in which the radiation beam reflected by the record carrier is detected by a single photo detector, 1/4? May be selected as the depth for the recess, where? Is the wavelength of the radiation beam used. If a value of 1/8 lambda or less is selected for the depth of the servo track in the information area 9, this servo track has little effect on the amount of light detected by the detector.

To further explain the structure of the synchronization area, FIG. 6C shows such a synchronization area on an enlarged scale, and for simplicity, the information layer 9 is omitted. This synchronization area 8 comprises two parts: the display part 10 and the address part 11. The address portion 11 contains all the information necessary to control the writing process. When recording digital information, this information is converted into so-called word-organization bit series. The address portion contains information about the word organization, so that the position of the bit word during writing is limited and the bit word is properly decoded during reading. The address portion 11 also contains information on the associated track number. This information takes the form of a relief structure in accordance with a digital modulation technique suitable for the recording medium. In addition to the home-shaped servo track in the information part 9, the writing used by the user since the record carrier in the synchronization area already contains all the information necessary to locate the bit word organization bit series type information in the information area. And the requirements imposed on the panning device may be less stringent. In addition, since such completely prerecorded information is formed on the record carrier as a relief structure, the record carrier makes it possible to use conventional pressing techniques, which is particularly suitable for mass production.

8a and 8b show two different embodiments of the servotrack 4 in the cross section in the longitudinal axis direction of the servo track 4 having a part of the synchronization area 8 and a part of the information area 9. Figure 8a shows a cross section on the blank preparation area. The prepared disk is provided with a servo track 4 formed on the substrate 5 by, for example, a laser beam. By adjusting the intensity of the laser beam, it becomes possible to form a relief structure of "pits 13" containing information in the synchronization area 8.

Subsequently, for the sake of simplicity, the entire disc including the record carrier portion D outside the groove may be coated with the reflective information layer 6. Therefore, the information prepared in the record carrier can be recorded in the information area 9 by forming a hole in the reflective information layer 6 using, for example, a laser beam.

8B shows a blank ready disk provided with clock information or a signal of frequency fo. As described in Dutch Patent Application No. 8000121, clock information is used to synchronize the recording operation.

A recording apparatus for a disc shown in FIG. 8B is shown in FIG. 9, which schematically shows an apparatus for providing a prepared disc with information and simultaneously driving a clock modulation structure. The device comprises a laser 15 which projects the beam of the laser onto the disk D through the translucent mirror 17 and the focusing optics 18. The reflected beam is converted into the form of an electrical signal, for example detected using a photodiode cell 27 and extracting a frequency fo component using the band pass filter 28, the frequency fo component being mainly a track (4). Is generated by the clock modulation structure formed at The signal may also be applied to the phase locked loop 29, which improves the aftershocks to increase the constantness of the clock signal and also compensate for simple signal dropouts. The output signal is then available to the output 31. The data can be recorded by pulse modulation of the laser beam 16 by directly incorporating a modulator or as shown in FIG. 6B by modulating the laser 15 with the write modulator circuit 25, wherein the write modulator circuit Information is applied via an input 26 which is registered with the clock signal on the output 31.

The information contained in the synchronization portion is recovered from the reflected beam via the photosensitive element 27 and the readout circuit 30, which is shown on the output 32. The read circuit 30 may also be synchronized with the clock signal on the output 31. This information may be used to synchronize the write modulator circuit 25 and locate the correct location on the disk. This information can also be used for servo control to radially position the optical device 18 and the mirror, to engrave the desired portion of the track and to control the drive of the disk D.

The recording apparatus may also be provided with a tracking circuit 33 which derives the tracking signal from the signal supplied by the detector 27 to hold the beam in the track 4 by controlling the angle associated with the beam of the mirror 17. It may be.

Claims (3)

An optical system for focusing the radiation source and the radiation beam emitted by the radiation source to the radiation sensing information layer of the recording carrier;

A control device for controlling a radiation source in accordance with an applied binary information signal comprising a series of bitcells having at least n consecutive bitcells of 2 in the same form, the recording carrier having a radiation sensing information layer An apparatus for recording a binary information signal, wherein the control device is configured to supply a control pulse to a radiation source, wherein the radiation source is configured to generate radiation pulses in response to the control pulse. 1 <m in signal

A digital binary information signal recording apparatus characterized in that unit recording marks corresponding to m consecutive bit cells of the same first type of n are formed on a record carrier. 2. The control apparatus according to claim 1, wherein the control device comprises (p + 1) radiation sources in which (n + p) consecutive bit cells of the same first type of information signal are consequently spaced apart from each other at time intervals corresponding to one bit cell. A digital binary information signal recording apparatus characterized in that it is configured to be a control pulse. n

A control device for controlling a radiation source in accordance with an applied binary information signal comprising a series of bitcells of at least n consecutive bitcells of the same type, wherein the control device supplies a control pulse to the radiation source. And the radiation source is adapted to generate a control pulse, wherein the same first type (n + p) consecutive bit cells of the information signal are consequently mutually spaced at a time interval corresponding to one bit cell. And (p + 1) radiation source control pulses spaced from the control device.

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