Optical disk and optical information processor

An optical disk for accumulating information in the form in which an information signal can be optically read, wherein to the end of additionally recording information, a line of pits are arrayed at periodical intervals on an information recording carrier and are recorded in a manner to minutely wobble in the rotating direction of the disk at a fixed period.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an optical disk for accumulating digital 
information etc. in a form in which the data can be optically recorded and 
reproduced. More particularly, it relates to an optical disk suitable for 
additionally recording information and also to an information processor 
therefor. 
2. Description of the Prior Art 
In, for example, an optical disk for accumulating digital information in a 
form in which it can be optically recorded and reproduced, there has 
heretofore been proposed a system for additionally recording the 
information wherein a groove for guiding a light beam spot is provided in 
the optical disk in advance and wherein in recording the information, the 
light beam spot is guided in reliance on the guide groove (Press 
information Philips Nov. 7, 1978). 
However, the prior-art optical disk in which the light beam spot is guided 
in reliance on the guide groove has a disadvantage as stated below. In 
order to execute the additional recording, any desired recording area 
(hereinbelow, termed "sector portion") must be reached by random access. 
To this end, an address signal must be recorded in a part of the sector 
portion in advance. Now, this will be described with reference to the 
drawings. FIGS. 1(a) and 1(c) are views showing the structure of the 
optical disk provided with the guide groove. FIG. 1(a) is a sectional view 
in a direction tangential to the groove, while FIG. 1(c) is a schematic 
sectional view in a radial direction of the disk. 
As illustrated in FIGS. 1(a) and 1(c), an address portion I is recorded by 
the phase type in which the phase of light waves is changed, and an 
additional recording portion II by the intensity type in which the 
intensity of light is changed. When this disk is subjected to reproduction 
by the reflection type, a signal 4 as shown in FIG. 1(b) is detected in 
correspondence with the pits. In the figures, numeral 1 designates a 
substrate, numeral 2 a metal film, letter h the depth of the pit 3 formed 
in the address portion I, and letter h' the depth of the groove G formed 
in the additional recording portion II. Shown at 5 is the pit which exists 
in the groove G. 
The portion of the phase type is recorded in such a way that the substrate 
1 (of, for example, PVC (polyvinyl chloride), glass or the like) is varied 
h in the depth direction. On the other hand, the portion of the intensity 
type is recorded depending upon the presence or absence of the metal thin 
film 2 which is evaporated or applied on the groove formed in the 
substrate 1. Letting T.sub.1 denote the reflection factor of the thin 
metal film 2 and T.sub.2 the reflection factor of the substrate 1, the 
detection signal 4 varies as shown in FIG. 1(b) as the readout spot moves 
in the direction of a time axis t. Usually, the reflection factor T.sub.2 
of the substrate 1 is 4-5%, and that T.sub.1 of the thin metal film 2 is 
40-50%. Moreover, when note is taken of the detection signal, reflected 
light intensities decrease in the pits of both the portions. Therefore, in 
case where the intensity type portion and the phase type portion have been 
separately recorded for the additional information and the address 
information, respectively, they cannot be distinguished insofar as the 
levels of the signal is concerned to the disadvantage of this type of 
recording. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide an optical disk which can 
additionally record information easily. 
Another object of this invention is to provide an optical disk which can 
reproduce information easily. 
Still another object of this invention is to provide an optical information 
processor which is suited to record and reproduce information. 
This invention for accomplishing such objects is characterized in that pits 
are recorded at any desired interval which is at least equal to the size 
of one information pit to be additionally recorded, and that the line of 
the pits is minutely wobbled at a fixed period in the recording, the 
recorded line of the pits serving as a guide groove.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 2 is a diagram showing the construction of an embodiment of this 
invention. 
In FIG. 2, pits 6 for a guide groove are indicated by solid lines 
(indicated by hatching), and pits 7 to be additionally recorded are 
indicated by dotted lines. For the sake of simplification, the pit 
interval of the guide groove corresponds to one pit of the additional 
recording. The line of the pits of the guide groove is recorded so as to 
wobble with respect to the traveling direction of the groove a minute 
amplitude .delta. at a period T, and the pit interval has a period t. 
According to the disk of such construction, owing to the fact that the line 
of the pits previously recorded is wobbling at the minute amplitude 
.delta. during the additional recording, a tracking operation in which a 
light beam spot accurately tracks the line of the pits can be executed by 
a method disclosed in the specification of Japanese Published Unexamined 
Patent Application No. 49-103515 filed by the applicant of the present 
application, and it is permitted to additionally record the information 
pits. 
Subsequently, since the line of the pits is always reproduced at the fixed 
period T, the PLL (phase locked loop) which has been used in order to 
accurately record and reproduce information against fluctuations in the 
rotating velocity of an information recording carrier in the recording and 
reproducing apparatus of this type, for example, a magnetic disk, a 
magnetic tape or the like, is easy to pull in and difficult to pull out. 
Moreover, since the positions of the pits to be additionally recorded can 
be determined with reference to those of the pits of the guide groove, 
timing errors in the case of reproducing the information are lessened. 
With the disk of such construction, the following effect is achieved. The 
additional recording is ordinarily carried out by the intensity type in 
which holes are provided in a thin metal film formed on a recording 
medium. As the guide groove, this invention is applicable to both the 
recording form of the intensity type stated above and the recording form 
of the phase type in which the pits are formed in the depth direction of 
the recording medium. Especially in case of the intensity type, it is 
unnecessary to work uneven parts in the information recording carrier in 
advance, a flat carrier can be used, and control information of addresses 
etc. are added at will, whereby the requirements of the users of the disks 
can be pliably met. 
FIG. 3 is a diagram showing another embodiment of this invention. Line (a) 
of FIG. 3 illustrates a section of a line of bits recorded. 6-1 to 6-5 
indicate guide pits, the depth of which is made 1/4 of the wavelength 
.lambda. of a laser beam for use in the reproduction. Suitable as a disk 
substrate 8 is photoresist which is applied on a PVC (polyvinyl chloride) 
or glass disk ordinarily used as a duplication disk. Line (b) of FIG. 3 is 
a sectional view of a disk for additional recording. On the line of pits 
shown in (a) of FIG. 3, a thin metal film 9 is formed by an expedient such 
as evaporation. Line (c) of FIG. 3 shows a surface part in (b) of FIG. 3, 
and depicts the relation between the guide pits and additional recording 
pits similar to FIG. 2. In this embodiment, the sizes of the recording pit 
and the guide pit are approximately equal. 
A third embodiment is shown in FIG. 4. The sectional shape of guide pits is 
similar to that in (a) of FIG. 3, and the preparation of an 
additionally-recorded disk is also similar to that in (b) of FIG. 3. 
However, the size of the guide pits 6-1 to 6-5 is made larger than that of 
recording pits 7-1 to 7-10 in order to facilitate separating the guide 
pits and the recording pits when the additionally-recorded information are 
to be reproduced. Thus, the guide pits and the recording pits can be 
separated on the basis of a waveform at the reproduction by utilizing 
unequal signal levels. 
Further, a fourth embodiment is shown in FIG. 5. The sectional shape of 
guide pits is depicted in (a) of FIG. 5. The depth of the pits is denoted 
by d. A disk is prepared as in (b) of FIG. 3, but the size of the guide 
pits 6-1 to 6-5 is made smaller than the recording pits 8-1 to 8-10 for 
the same reason as in the third embodiment. In this way, the guide pits 
and the recording pits can be separated from a reproduced signal waveform. 
Although the depth d may well be 1/4 of a reproducing laser wavelength 
.lambda., it should suitably be 1/8. 
A fifth embodiment is shown in FIG. 6. A guide groove is recorded by the 
intensity type in which holes are provided in a thin metal film formed on 
a disk surface. Also in this case, it is desirable that, in order to 
distinguish the guide pits from the recording pits, they are recorded in 
sizes different from each other as in the third and fourth embodiments. 
The guide pits 9-1 to 9-5 are recorded in the thin metal film 3 formed on 
an information recording carrier 12. By recording the guide groove in the 
intensity type, the additional recording disk which is capable of pliable 
compliance as stated before is prepared. 
The additional recording can be reliably performed by forming the guide 
groove described above. Although, in the embodiments, the guide pit 
interval has been exemplified to include one recording pit or two 
recording pits, it is a matter of course that the invention is not 
restricted thereto. 
A recording apparatus according to this invention for forming the guide 
grooves explained in the above embodiments will be described with 
reference to FIG. 7. A laser 61 beam 72 radiated from an argon ion laser 
for recording is subjected to an intensity modulation by passing through 
an optical modulator 62, and is adjusted through a light attenuator 73 so 
as to have the optimum power for the recording. After it is reflected by a 
reflective mirror 63, the reflected beam passes through an optical 
deflector 64 to be deflected in a very small quantity in a radial 
direction of a rotating disk 66 and is converged into a very small spot of 
about 1 .mu.m on the surface of the disk 66 by an objective 65. The disk 
66 is rotating about an axis of rotation 71 in the direction of the arrow. 
The rotational motion is caused through a spindle 67 from a motor 68. The 
disk is driven in the directions of arrows in such a manner that the disk 
66, the spindle 67 and the motor 68 become unitary and that forces from a 
driver 69 having known means are transmitted thereto through an arm 70. A 
signal from an oscillator 76 having a period t and a repetition frequency 
f.sub.0 and an output of an oscillator 77 having a repetition frequency 
f.sub.1 are added up by an adder 75, an output of which is applied to the 
optical modulator 62 so as to modulate the beam. Since the disk is 
rotating at a constant speed by the signal at f.sub.0, the guide pits of 
the period t as shown in FIG. 2 are formed. Although not shown in FIG. 2, 
a pit P for determining the phase of the wobbling as shown in FIG. 20 is 
also formed by the signal at f.sub.1. On the other hand, an output from an 
oscillator 78 having a period T and a repetition frequency f.sub.2 is 
applied to a synchronizer circuit 74 and is synchronized with the output 
of the oscillator 77, and the resultant output is applied to the optical 
deflector 64. In this way, the light beam is minutely vibrated on the disk 
surface, and the wobbling recording of the line of pits at the period T as 
illustrated in FIG. 2 is conducted. In order to form the guide pits 
explained previously, the embodiment employs as an information recording 
carrier a glass disk coated with photoresist and records the pits by the 
use of the recording apparatus of FIG. 7. Thereafter, the same course as a 
process for manufacturing a conventional record is traced to fabricate a 
replica. In the fifth embodiment, a glass disk or a PMMA (polymethyl 
methacrylate) disk on which a metal is evaporated can be used. The control 
of the size of the guide pit may be made in such a way that, in FIG. 7, a 
light intensity to be transmitted through the light attenuator 73 in which 
the thickness of an evaporated film is varied in a rotating direction is 
changed by a rotating motion. That is, when the intensity transmitted is 
high, the pit is formed to be large, and when the former is low, the 
latter is formed to be small. 
FIG. 8 is a view for explaining the construction of an embodiment of a 
recording apparatus of this invention. An optical disk 66 having the guide 
groove (guide pits) above stated is rotating in the direction of the arrow 
in the figure about an axis of rotation 71. A light beam (indicated by 
oblique lines) radiated through an optical system 82 from a semiconductor 
laser 81 is reflected by the optical disk 66, whereupon the reflected beam 
returns to the semiconductor laser 81 again through the optical path. 
Then, the quantity of light to emerge from the semiconductor laser 81 is 
modulated by the light returning from the disk. A signal on the disk can 
accordingly be read out in such a way that light emergent from one facet 
of the semiconductor laser 81 is detected by a photodetector 80. This 
detection method is based on the so-called self-coupling effect of a 
semiconductor laser as has been known. 
(a) of FIG. 9 shows a reproduced signal 93 from the detector 80. It is the 
change of the envelope of the signal owing to the guide groove of this 
invention that appears in the lower part of the reproduced signal 93. When 
the spot of the light beam is projected perfectly in the middle of the 
groove, the repetition period of the envelope becomes 2T. When the spot 
deviates from the groove towards either the inner periphery or outer 
periphery of the disk, a signal of a period T and a different phase 
appears in the envelope. The tracking is executed by utilizing this fact. 
The signal 93 from the detector 80 is applied to a tracking signal detector 
84, to detect a tracking signal by the known tracking method disclosed in 
the specification of Japanese Published Unexamined Patent Application No. 
49-103515. The tracking signal is applied to a phase compensator 85, to 
stabilize a control system. An output of the phase compensator is used to 
drive a linear motor 83, and an optical head (consisting of the 
semiconductor laser and the optical system) connected to the linear motor 
is moved for the tracking. Thus, the light spot tracks the guide groove. 
In order to perform the recording, first of all, the signal 93 from the 
photodetector 80 is applied to a digital signal detector 86. Here, a 
signal 87 (hereinbelow, termed "guide pulse signal") corresponding to the 
line of pits forming the guide groove and a periodic clock signal 89 are 
generated by a conventional means or method (for example, a comparator is 
used to convert an analog signal into a digital signal, or a phase 
synchronization in which a signal synchronous with the clock of a 
detection signal is generated is performed). The relation of the two 
signals on a time axis is seen from (b) and (c) of FIG. 9. This 
corresponds to the geometrical arrangement of FIG. 2 on the disk surface. 
The guide pulses 87 and the periodic clock pulses 89 are applied to an 
additional-recording clock generator (exclusive OR circuit) 88 to take the 
exclusive OR, whereby a recording clock signal for the additional 
recording is generated from the two signals. 
The recording clock signal is modulated by a modulator (AND circuit) 90 in 
accordance with an information signal 95 from a signal source 91 intended 
to be additionally recorded. The modulated signal 94 is applied to a 
semiconductor laser drive circuit 92, to modulate the laser oscillation 
power of the semiconductor laser. 
Here, the recording clock pulses do not overlap the guide pulses 87 on the 
time axis. According to the above method, therefore, the 
additional-recording pits are formed between the pits forming the guide 
groove. 
The simplest modulation method is such that, as illustrated in (d) and (e) 
of FIG. 9, the exclusive OR between the signal 87 and the signal 89 is 
taken to prepare the recording clock signal, whereupon the AND between the 
recording clock signal and the information signal 95 is taken to obtain 
the modulated signal 94. 
An apparatus for reproducing the information recorded in the above way will 
be described with reference to FIG. 10. 
FIG. 10, parts assigned the same numerals as in FIG. 8 effect the same 
operations and functions. As shown in FIG. 11A, a reproduced signal 100 
becomes a waveform similar to that in (a) of FIG. 9 and differs from the 
latter in including the additional-recording information. A tracking 
signal is detected in the same way as in the embodiment of FIG. 8. 
FIG. 11A illustrates the reproduced signal from the optical disk shown in 
FIG. 4. In this case, the degree of modulation of a signal from the 
additional-recording pits is lower in comparison with the degree of 
modulation of a signal from the pits forming the guide groove. Therefore, 
the additional information can be separated from among the data signal 
more easily than in the foregoing embodiment. That is, only the guide 
pulses are detected from the reproduced analog signal by selecting the 
levels of comparators, and using them, only the additional information 
signal can be detected from the data signal. More specifically, as 
illustrated in FIG. 11B, two comparators 11-1 and 11-2 are disposed, and 
outputs of these comparators are applied to an exclusive OR circuit 11-3. 
As shown in FIG. 11C, the threshold value of the signal level from the 
pits forming the guide groove is set to V.sub.1, and that of the signal 
level from the additional-recording pits to V.sub.2. The threshold values 
V.sub.1 and V.sub.2 are applied to one-side terminals of the comparators 
11-1 and 11-2, and the signal shown in FIG. 11A is applied to the other 
terminals of the comparators 11-1 and 11-2, whereby signals shown in FIGS. 
11D and 11E are obtained. By applying both these signals to the exclusive 
OR circuit 11-3, the additional information as shown in FIG. 11F is 
detected. 
The reproduced signal 100 provides the data signal 106 corresponding to the 
recorded pits (shown in (a) of FIG. 12) and a periodic clock signal 105 
(shown in (b) of FIG. 12) through an analog-to-digital converter 101 and 
by a conventional method (the analog signal is converted into a digital 
signal by the use of a comparator, and pulses whose phase is synchronous 
with the periodic signal included in the reproduced signal are formed by a 
PLL). 
The above operation is realized by an arrangement shown by a block diagram 
in (e) of FIG. 12. The arrangement in (e) of FIG. 12 is constructed of a 
comparator 101, a PLL circuit 103 and a demodulator 102, and it generates 
an information signal 107. The additionally-recorded information signal 
107 is obtained by applying the two signals 106 and 105 to the demodulator 
102. 
The operation of the demodulator 102 will be described with reference to 
FIG. 12. Since the data signal 106 includes the guide pulses, the guide 
pulses are prepared from the periodic clock signal 105 (in this case, the 
guide pulses are a train of pulses at a fixed recurrence frequency, and 
hence, they can be obtained by dividing the frequency of the periodic 
clock pulses on the basis of a characteristic signal (the so-called 
trigger signal) indicative of the beginning of the data signal), and the 
recorded clock signal of the additional recording is reproduced by the 
exclusive OR between the guide pulses and the periodic clock signal 105, 
whereby a signal shown in (c) of FIG. 12 is obtained. When the AND between 
this signal and the data signal 106 is taken, the additional-recording 
information signal 107 (shown in (d) of FIG. 12) is obtained. 
Such operation is realized by an arrangement shown by a block diagram in 
(f) of FIG. 12. The arrangement in (f) of FIG. 12 is constructed of a 
frequency divider circuit 12-1, an exclusive OR circuit 12-2 and an AND 
circuit 12-3. T.sub.R denotes a terminal for applying the trigger signal. 
Still another embodiment will be described with reference to FIG. 13. A 
signal 93 from a photodetector 80 is applied to a digital signal detector 
86' so as to generate a signal .phi.(1) corresponding to the line of pits 
forming the guide groove and a periodic clock signal .phi.(6). The 
relation of the two signals .phi.(1) and .phi.(6) on a time axis is 
illustrated in FIG. 15. In this embodiment, the repetition period T of the 
signal .phi.(1) and that t of the signal .phi.(6) are selected so as to 
satisfy the relation of T=6.times.t. A method of preparing the pulse train 
of the signal .phi.(6) from the signal .phi.(1) indicative of the line of 
pits of the guide groove by means of a PLL is known. 
The signals .phi.(6) and .phi.(1) are applied to an additional-recording 
clock signal oscillator 88', to form recording clock signals .phi.(4) and 
.phi.(5) shown in FIG. 15 by the use of a sequence circuit such as a known 
electric counter. An information signal (data) from a source 91' intended 
to be additionally recorded is modulated by a modulator (AND circuit) 90' 
in accordance with the recording clock signals, and the modulated signal 
94' is applied to a semiconductor laser drive circuit 92' so as to 
modulate the laser oscillation power of a semiconductor laser. 
The modulation system and the modulator 90' of the present embodiment will 
be described in detail. A method suitable as the modulation system of this 
invention is the combination between an encoding in which m bits of data 
are handled as a unit and converted into n recording bits, and the 
modulation of the code by NRZ 1 (non-return-to-zero one) (or by NRZ 
(non-return-to-zero)). Among such combinations, a case of using what is 
called 4/5MNRZ 1 will be stated as an example. 
The 4/5 conversion corresponds to a case where m=4 and n=5. A conversion 
table in this case is shown in FIG. 14. The construction of the modulator 
90' is shown in FIG. 16, and the timing chart in FIG. 15. The data is 
first stored in a memory 200. The data is read out in accordance with the 
clock signal .phi.(4), and is shifted to a 4-bit register 201 every period 
T. By the combination between an AND circuit 203 and an OR circuit 204 in 
FIG. 16, the conversion illustrated in FIG. 14 is performed, and the code 
is latched in a 5-bit register 200. When it is read out in accordance with 
the clock signal .phi.(5), the modulated signal 94' is formed. 
An apparatus for reproducing the information recorded by the preceding 
embodiment will be described with reference to FIG. 17. In FIG. 17, a 
reproduced signal 100' generates through an analog-to-digital converter 
101' a reproduced data signal 106' and a pulse signal 105' whose phase is 
synchronous with that of the periodic signal included in the reproduced 
signal. 
There will be explained means for generating the signals 106' and 105' from 
the signal 100'. Since the 4/5 conversion is executed, at least one pit 
exists infallibly in a part which does not include the pits forming the 
guide groove, that is, a part in which the additional information is 
recorded. Since a signal component of a period t is therefore existent in 
the reproduced signal, the phase lock can be effected by a PLL in 
synchronism with this period and the signal 105' can be generated. 
As illustrated in FIG. 18, a train of pulses .rho.(1) corresponding to the 
pits forming the guide groove is formed by the use of the foregoing signal 
105'. More specifically, in the apparatus for recording digital 
information as in this invention, the recording information is divided 
into blocks each consisting of a specified number of bits, and a signal 
indicative of the borders of the blocks is infallibly inserted. 
Accordingly, when the relation of the signal .rho.(1) indicating the 
borders is put into a predetermined rule and the signal 105' has its 
frequency divided by 6 (six) by the use of the signal indicating the 
borders, the signal .rho.(1) is obtained. 
When, using the aforecited signal .rho.(1), the signal corresponding to the 
pits forming the guide groove is removed from the reproduced signal 100', 
the reproduced data signal 106' is obtained. Means for demodulating the 
reproduced data signal 106' will be explained more with reference to FIG. 
17. 
The signal 105' is applied to a demodulating clock oscillator 110, to 
generate de-modulating clock signals .rho.(4) and .rho.(5). The reproduced 
data signal 106' is demodulated with a demodulator 111 in accordance with 
the signals .rho.(4) and .rho.(5), whereby demodulated data is obtained. 
A method of demodulation will be explained with reference to FIG. 19. The 
reproduced data signal 106' is put into a 5-bit shift register 120 in 
accordance with the signal .rho.(5), a pattern of 5 bits is converted into 
a pattern of 4 bits by the combination of AND circuits 122 and OR circuits 
123, and the pattern of 4 bits is latched in a 4-bit shift register 121 
and read out in accordance with the signal .rho.(4) every period T.