An optical disk carrying barcoded information

Abstract: An optical disk on which data is recorded comprises an identifier in a prescribed region for indicating whether a barcode-like mark is present or not on said optical disk, said identifier and said barcode-like mark being in respectively different locations on said disk, said barcode-like mark being disposed in a circumferential direction and having a plurality of bars each extending in a radial direction, wherein at least a portion of said barcode-like mark overwrites a pre-pit area of the disk.

Description: The present invention relates to an optical disk having a barcode-like mark according to the preamble part of claim 1. An optical disk of this kind is known from EP-A- 741382. In the manufacturing process of optical disks, it has been commonly practiced to record a serial number, lot number, etc. on each optical disk in the form of a barcode. Since such information cannot be written to a pit information area of the optical disk, it has been practiced to write the barcoded information to a non-information area, or unused space, on the optical disk. When reproducing (playing back) such an optical disk, the pit information is read by an optical pickup; to read the barcoded information such as a serial number, etc. recorded in the non-information area, however, a separate reading device has been used. In the above prior art optical disk, since information carrying a serial number and the like is not recorded in a pit area but recorded in a non-information area, as described above, a separate reading device has had to be provided in addition to the usual optical pickup, the resulting problem being increases complexity of the playback apparatus construction. In view of the above problem with the prior art, it is the object of the present invention to provide an optical disk wherein data such as a disk ID number, etc. is converted into a barcode and recorded on the disk, in fashion permitting the use of a single optical pickup to read both the bit data and barcode data. The invention is an optical disk as set forth in claim 1. Preferred embodiments of the invention are subject matter of the dependent claims. Figure 1 is a diagram showing a disk manufacturing process and a secondary recording process; Figure 2(a) is a top plan view of a disk according to the embodiment, (b) is a top plan view of the disk according to the embodiment, (c) is a top plan view of the disk according to the embodiment, (d) is a transverse sectional view of the disk according to the embodiment, and (e) is a waveform diagram of a reproduced signal according to the embodiment; Figure 3 is a flowchart illustrating a process of recording encrypted position information on a disk in the form of a barcode according to the present embodiment; Figure 4 is a diagram showing a disk fabrication process and a secondary recording process (part 1); Figure 5 is a diagram showing the disk fabrication process and the secondary recording process (part 2); Figure 6 is a diagram showing a two-layer disk fabrication process (part 1); Figure 7 is a diagram showing the two-layer disk fabrication process (part 2); Figure 8(a) is an enlarged view of a nonreflective portion of a laminated type, and (b) is an enlarged view of a nonreflective portion of a single-plate type; Figure 9(a) is a reproduced-waveform diagram for a nonreflective portion, (b) is a reproduced-waveform diagram for a nonreflective portion, (c) is a reproduced-waveform diagram for a nonreflective portion, and (d) is a plan view of a master disk produced by a master disk method; Figure 10(a) is a cross-sectional view of a nonreflective portion of the laminated type, and (b) is a cross-sectional view of a nonreflective portion of the single-plate; Figure 11 is a schematic diagram, based on an observation through a transmission electron microscope, illustrating a cross section of the nonreflective portion; Figure 12(a) is a cross-sectional view of a disk according to the present embodiment, and (b) is a crosssectional view of the nonreflective portion of the disk according to the present embodiment; Figure 13 is a block diagram of a low-reflectivity position detector according to the embodiment; Figure 14 is a diagram illustrating the principle of detecting address/clock positions of a low-reflectivity portion according to the embodiment; Figure 15A is a flowchart illustrating a procedure for encryption, etc. using an RSA function; Figure 15B is a flowchart illustrating a position information check process; Figure 16 is a block diagram of a stripe recording apparatus; Figure 17 is a diagram showing a signal waveform and a trimming pattern in RZ recording; Figure 18 is a diagram showing a signal waveform and a trimming pattern in NRZ recording; Figure 19 is a diagram showing a signal waveform and a trimming pattern in PE-RZ recording; Figure 20 is a diagram showing a top plan view of disk stripes, along with signal waveforms; Figure 21(a) is a perspective view of a converging unit, and (b) is a diagram showing a stripe arrangement and an emitting-pulse signal; and Figure 22 is a diagram showing the arrangement of stripes on a disk and the contents of control data. The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the description hereinafter given, position information for piracy prevention, which is a form of ID, is taken as an example of information to be barcoded. In the first-half part (I) of the description, a detailed explanation will be given of the piracy prevention position information as a form of ID, followed by a brief explanation of how the information is converted into a barcode to complete an optical disk and how the optical disk is played back. In the second-half part (II), the technique for barcoding the piracy prevention position information will be described in further detail and in a concrete manner. More specifically, the first-half part (I) deals with (A) Manufacturing a disk, (B) Forming a marking by using laser light, (C) Reading the position information of the marking, (D) Encrypting the position information, converting the encrypted position information into a barcode, and writing the barcode in a pre-pit area of the optical disk in overwriting fashion, and (E) Playing back the optical disk on a player. The second-half part (II) first describes (A) Usefulness of the barcode for a laminated-type optical disk, then proceeds to (B) Barcoding the position information of the marking as a disk-unique ID, (C) Features of the barcode-recorded optical disk format, methods of tracking control, and methods of rotational speed control during reading of the barcode, and (D) Playing back the barcode-recorded optical disk. The second-half part (II) further deals in detail with (E) Manufacturing techniques for implementing the barcode recording method, followed by a brief explanation of a barcode playback apparatus (player). Finally, a description is given of (F) An example of the above barcode encryption and another application example of the barcode. (I) Before proceeding to the description of the above (A) to (E), we will first describe a general process flow from disk manufacturing to the completion of an optical disk by using the flowchart of Figure 1. In this patent specification, laser trimming is also referred to as laser marking, while a nonreflective optical marking portion is simply referred to as the barcode, stripe, marking, or optical marking or, sometimes, as the physical ID unique to a disk. First, the software company performs software authoring in software production process 820. The completed software is delivered from the software company to the disk manufacturing factory. In disk manufacturing process 816 at the disk manufacturing factory, the completed software is input in step 818a, a master disk is produced (step 818b), disks are pressed (steps 818e, 818g), reflective films are formed on the respective disks (steps 818f, 818h), the two disks are laminated together (step 818i), and a ROM disk such as a DVD or CD is completed (step 818m, etc.). The thus completed disk 800 is delivered to the software maker or to a factory under control of the software maker, where, in secondary recording process 817, an anti-piracy marking 584, such the one shown in Figure 2, is formed (step 819a), and accurate position information of this mark is read by a measuring means (step 819b) to obtain the position information which serves as the physical feature information of the disk. This physical feature information of the disk is encrypted in step 819c. The encrypted information is converted to a PE-RZ-modulated signal which is then recorded in step 819d as a barcode signal on the disk by using a laser. The disk physical feature information may be combined together with software feature information for encryption in step 819c. The above processes will be described in further detail. That is, a disk fabrication process, a marking formation process, a marking position reading process, and an encrypted information writing process for an optical disk according to the present invention will be described in detail with reference to Figures 4 and 5 and Figures 8 to 12. A supplementary explanation will also be given dealing with a disk having two reflective layers with reference to Figures 6 and 7. In the following description, the marking formation process and the marking position reading process are collectively called the secondary recording process. (A) First, the disk fabrication process will be described. In the disk fabrication process 806 shown in Figure 4, first a transparent substrate 801 is pressed in step (1). In step (2), a metal such as aluminum or gold is sputtered to form a reflective layer 802. An adhesive layer 804 formed from an ultraviolet curing resin is applied by spin coating to a substrate 803 formed in a different processing step, and the substrate 803 is bonded to the transparent substrate 801 having the reflective layer 802, and they are rotated at high speed to make the bonding spacing uniform. By exposure to external ultraviolet radiation, the resin hardens, thus firmly bonding the two substrates together. In step (4), a printed layer 805 where a CD or DVD title is printed, is printed by screen printing or offset printing. Thus, in step (4), the ordinary laminated-type optical ROM disk is completed. (B) Next, the marking formation process will be described with reference to Figures 4 and 5. In Figure 4, a laser beam from a pulsed laser 813 such as a YAG laser is focused through a converging lens 814 onto the reflective layer 802, to form a nonreflective portion 815 as shown in step (6) in Figure 5. That is, a distinct waveform, such as the waveform (A) shown in step (7), is reproduced from the nonreflective portion 815 formed in step (6) in Figure 5. By slicing this waveform, a marking detection signal such as shown by waveform (B) is obtained, from which hierarchial marking position information comprising an address, such as shown in signal (d), and an address, a frame synchronizing signal number, and a reproduced clock count, such as shown in signal (e), can be measured. At the rising edge of the thus obtained marking detection signal, a specific address (indicated by address n in Figure 5(d)) is read by the optical pickup from within the plurality of addresses shown in Figure 5(d). Figure 5(b) shows the physical location of the specific address in schematic form. On the other hand, Figure 5(e) shows the logical structure of the data. As shown in Figure 5(e), there are m frame synchronization signals under address n, and k reproduced clock pulses under each frame synchronization signal. Therefore, the position of the marking measured by the optical pickup can be represented by address, frame synchronization signal number, and reproduced clock count.As previously stated, a supplementary explanation will be given below of an alternative type of disk (a two-layer laminated disk) with reference to Figures 6 and 7.Figures 4 and 5 showed a disk generally known as a single-layer laminated disk which has a reflective layer only on one substrate 801. On the other hand, Figures 6 and 7 show a disk generally known as a two-layer laminated disk which has reflective layers on both substrates 801 and 803. For laser trimming, the processing steps (5) and (6) are fundamentally the same for both types of disks, except with significant differences which are briefly described below. First, while the single-layer disk uses a reflective layer formed from an aluminum film having reflectivity as high as 70% or over, in the two-layer disk the reflective layer 801 formed on the reading-side substrate 801 is a semi-transparent gold (Au) film having a reflectivity of 30%, while the reflective layer 802 formed on the print-side substrate 803 is the same as that used in the single-layer disk. Second, as compared with the single-layer disk, the two-layer disk is required to have high optical accuracy; for example, the adhesive layer 804 must be optically transparent and be uniform in thickness, and the optical transparency must not be lost due to laser trimming.Parts (7), (8), and (9) of Figure 7 show the signal waveforms obtained from the first layer of the two-recording-layer disk. Likewise, parts (10), (11), and (12) of Figure 7 show the signal waveforms obtained from the second layer of the two-recording-layer disk. The contents of these signal waveforms are essentially the same as those of the waveforms described with reference to parts (a) to (c) of Figure 5. The waveform from the second layer is similar to that from the first layer, though the signal level is lower than from the first layer. However, since the first and second layers are bonded together, relative positional accuracy between them is random and can be controlled only with an accuracy of a few hundred microns. As will be described later, since the laser beam passes through the two reflective films, to make an illegal disk the position informations on the first and second layers for the first mark, for example, have to be made to match the same value on the legitimate disk. But making them match would require a near-submicron accuracy in laminating, and consequently, making illegal disks of the two-layer type is practically impossible.The technique for forming the nonreflective optical marking portion will be described in further detail in sections (a) to (d) below with reference to Figures 8 to 12, etc., dealing with the laminated type in comparison with a single-plate type. Figures 8(a) and (b) are micrographs showing plan views of nonreflective optical marking portions, and Figure 10(a) is a simplified schematic cross-sectional view of a nonreflective portion of the two-layer laminated disk. (a) Using a 5 µj/pulse YAG laser, a laser beam was applied to a 500angstrom aluminum layer lying 0.6 mm below the surface of a 1.2mm thick ROM disk consisting of two 0.6mm thick disks laminated together, and, as a result, a 12 µm wide slit-like nonreflective portion 815 was formed, as shown in the X 750 micrograph of Figure 8(a). In this X 750 micrograph, no aluminum residues were observed on the nonreflective portion 815. Thick swollen aluminum layers, 2000 angstroms thick and 2 µm wide, were observed along boundaries between the nonreflective portion 815 and reflective portions. As shown in Figure 10(a), it was confirmed that no significant damage had occurred inside. In this case, the application of the pulsed laser presumably melted the aluminum reflective layer, causing a phenomenon of molten aluminum buildup along the boundaries on both sides due to the surface tension. We call this a hot melt surface tension (HMST) recording method. This is a characteristic phenomenon observed only on a laminated disk 800. Figure 11 is a schematic diagram, based on an observation through a transmission electron microscope (TEM), illustrating a cross section of the nonreflective portion formed by the above laser trimming process. And Figure 11 shows that the adhesive layer of the disk has been removed by using solvent. In the figure, if the aluminum film swollen portion is 1.3 µm wide and 0.20 µm thick, the amount of increased aluminum in that portion is 1.3 x (0.20 - 0.05) = 0.195 µm 2 . The amount of aluminum originally deposited in a half portion (5 µm) of the laser exposed region (10 µm) was 5 x 0.05 = 0.250 µm 2 . The difference is calculated as 0.250 - 0.195 = 0.055 µm 2 . In terms of length, this is equivalent to 0. 055/0.05 = 1.1 µm. This means that an aluminum layer of 0.05 µm thickness and 1.1 µm length remained, and therefore, it can be safely said that almost all aluminum was drawn to the film swollen portion. Thus, the result of the analysis of the figure also verifies the explanation about the above-described characteristic phenomenon. (b) We will next deal with the case of a single-plate optical disk (an optical disk comprising a single disk). An experiment was conducted by applying laser pulses of the same power to a 0.05 µm thick aluminum reflective film formed on a single-sided molded disk, of which result is shown in Figure 8(b). As shown in the figure, aluminum residues were observed, and since these aluminum residues cause reproduction noise, it can be seen that the single-plate type is not suitable for secondary recording of optical disk information of which a high density and a low error rate are demanded. Furthermore, unlike the laminated disk, in the case of the single-plate disk, the protective layer 862 is inevitably damaged, as shown in Figure 10(b), when the nonreflective portion is subjected to laser trimming. The degree of damage depends on the laser power, but the damage cannot be avoided even if the laser power is controlled accurately. Moreover, according to our experiment, the printed layer 805 formed by screen printing to a thickness of a few hundred microns on the protective layer 862 was damaged when its thermal absorptance was high. In the case of the single-plate disk, to address the problem of protective layer damage, either the protective layer has to be applied once again or the laser cut operation should be performed before depositing the protective layer. In any case, the single-plate type may present a problem in that the laser cut process has to be incorporated in the pressing process. This limits the application of the single-plate disk despite its usefulness. (c) A comparison between single-plate disk and laminated disk has been described above, using a two-layer laminated disk as an example. As is apparent from the above description, the same effect as obtained with the two-layer laminated disk can be obtained with the single-layer laminated disk. Using Figures 12(a), 12(b), etc., a further description will be given dealing with the single-layer laminated disk type. As shown in Figure 12(a), the reflective layer 802 has the transparent substrate 801 of polycarbonate on one side, and the hardened adhesive layer 804 and a substrate on the other side, the reflective layer 802 thus being hermetically sealed therebetween. In this condition, pulsed laser light is focused thereon for heating; in the case of our experiment, heat of 5 µJ/pulse is applied to a circular spot of 10 to 20 µm diameter on the reflective layer 802 for a short period of 70 ns. As a result, the temperature instantly rises to 600°C, the melting point, melting state is caused. By heat transfer, a small portion of the transparent substrate 801 near the spot is melted, and also a portion of the adhesive layer 804 is melted. The molted aluminum in this state is caused by surface tension to build up along boundaries 821a and 821b, with tension being applied to both sides, thus forming buildups 822a and 822b of hardened aluminum, as shown in Figure 12(b). The nonreflective portion 584 free from aluminum residues is thus formed. This shows that a clearly defined nonreflective portion 584 can be obtained by laser-trimming the laminated disk as shown in Figures 10(a) and 12(a). Exposure of the reflective layer to the outside environment due to a damaged protective layer, which was the case with the single-plate type, was not observed even when the laser power was increased more than 10 times the optimum value. After the laser trimming, the nonreflective layer 584 has the structure shown in Figure 12(b) where it is sandwiched between the two transparent substrates 801, 803 and sealed with the adhesive layer 804 against the outside environment, thus producing the effect of protecting the structure from environmental effects. (C) Next, the process of reading the position of the thus formed marking will be described. Figure 13 is a block diagram showing a low reflectivity light amount detector 586 for detecting the nonreflective optical marking portion, along with its adjacent circuitry, in an optical disk manufacturing process. Figure 14 is a diagram illustrating the principle of detecting address/clock positions of the low reflectivity portion. For convenience of explanation, the following description deals with the operating principle when a read operation is performed on a nonreflective portion formed on an optical disk constructed from a single disk. It will be recognized that the same operating principle also applies to an optical disk constructed from two disks laminated together.As shown in Figure 13, the disk 800 is loaded into a marking reading apparatus equipped with a low reflectivity position detector 600 to read the marking, and in this case, since a signal waveform 823 due to the presence and absence of pits and a signal waveform 824 due to the presence of the nonreflective portion 584 are significantly different in signal level, as shown in the waveform diagram of Figure 9(a), they can be clearly distinguished using a simple circuit.Figure 9(a) is a diagram showing the waveform of a playback signal from a PCA area, described later, containing the nonreflective portion 584 formed by laser light. Figure 9(b) is a diagram showing the waveform of Figure 9(a) but with a different time axis.By removing the reflective film by laser light, as described above, a waveform easily distinguishable from that of a pit signal is obtained. Rather than forming an anti-piracy identification mark by removing the reflective film by laser light, as described above, the anti-piracy mark may be formed by changing the shape of pits on the master disk. This method will be described below. Figure 9(c) shows the waveform of a playback signal when the anti-piracy identification mark was formed by making pits longer than other data pits on the master disk. It can be seen from the diagram that the waveform 824p of the anti-piracy identification mark is distinguishable from the waveform of other pit data. In this way, a waveform similar to that obtained from the PCA area described later can be obtained by forming longer pits on the master disk; in this case, however, the waveform is a little difficult to distinguish as compared to the waveforms shown in parts (a) and (b) of Figure 9.By removing the reflective film by laser light, as described above, a waveform easily distinguishable from that of a pit signal is obtained. Rather than forming the barcode of the invention by removing the reflective film by laser light, as described above, the barcode may be formed by changing the shape of pits on the master disk. This master disk method will be described below. Figure 9(d) is a plan view showing a portion of a master disk wherein pits 824q in a few hundred tracks on the master disk are made longer than other data pits and made equal to the barcode bar width t (= 10 µm). Since reflectivity drops in this longer-bit area, a waveform 824 p as shown in Figure 9(c) is obtained. It can be seen from the diagram that the waveform 824p by the master disk method is distinguishable from the waveform of other pit data. In this way, a waveform similar to that obtained from the PCA area described later can be obtained by the master disk method; in this case, however, the waveform is a little difficult to distinguish as compared to the waveforms shown in parts (a) and (b) of Figure 9.As shown in Figure 14(1), the start and end positions of the nonreflective portion 564 having the above waveform can be easily detected by the low reflectivity light amount detector 586 shown in the block diagram of Figure 13. Using the reproduced clock signal as the reference signal, position information is obtained in a low reflectivity position information output section 596. Figure 14(1) shows a cross-sectional view of the optical disk.As shown in Figure 13, a comparator 587 in the low reflectivity light amount detector 586 detects the low reflectivity light portion by detecting an analog light reproduced signal having a lower signal level than a light amount reference value 588. During the detection period, a low reflectivity portion detection signal of the waveform shown in Figure 14(5) is output. The addresses and clock positions of the start position and end position of this signal are measured.The reproduced light signal is waveshaped by a waveform shaping circuit 590 having an AGC 590a, for conversion into a digital signal. A clock regenerator 38a regenerates a clock signal from the waveshaped signal. An EFM demodulator 592 in a demodulating section 591 demodulates the signal, and an ECC corrects errors and outputs a digital signal. The EFM-demodulated signal is also fed to a physical address output section 593 where an address of MSF, from Q bits of a subcode in the case of a CD, is output from an address output section 594 and a synchronizing signal, such as a frame synchronizing signal, is output from a synchronizing signal output section 595. From the clock regenerator 38a, a demodulated clock is output.In a low reflectivity portion address/clock signal position signal output section 596, a low reflectivity portion start/end position detector 599 accurately measures the start posistion and end position of the low reflectivity portion 584 by using an (n-1) address output section 597 and an address signal as well as a clock counter 598 and a synchronizing clock signal or the demodulated clock. This method will be described in detail by using the waveform diagrams shown in Figure 16. As shown in the cross-sectional view of the optical disk in Figure 14(1), the low reflectivity portion 584 of mark number 1 is formed partially. A reflection slope signal such as shown in Figure 14(3), is output, the signal level from the reflective portion being lower than the light amount reference value 588. This is detected by the light level comparator 587, and a low reflectivity light detection signal, such as shown in Figure 14(5), is output from the low reflectivity light amount detector 586. As shown by a reproduced digital signal in Figure 14(4), no digital signal is output from the mark region since it does not have a reflective layer.Next, to obtain the start and end positions of the low reflectivity light detection signal, the demodulated clock or synchronizing clock shown in Figure 14(6) is used along with address information. First, a reference clock 605 at address n in Figure 14(7) is measured. Then the address immediately preceding the address n is detected by the (n-1) address output section 597, it is found that the next sync 604 is a sync at address n. The number of clocks from the synch 604 to the reference clock 605, which is the start position of the low reflectivity light detection signal, is counted by the clock counter 598. This clock count is defined as a reference delay time TD which is measured by a reference delay time TD measuring section 608 for storage therein.The circuit delay time varies with reproduction apparatus used for reading, which means that the reference delay time TD varies depending on the reproduction apparatus used. Therefore, using the TD, a time delay corrector 607 applies time correction, and the resulting effect is that the start clock count for the low reflectivity portion can be measured accurately if reproduction apparatus of different designs are used for reading. Next, by finding the clock count and the start and end addresses for the optical mark No. 1 in the next track, clock m+14 at address n+12 is obtained, as shown in Figure 14(8). Since TD = m + 2 , the clock count is corrected to 12, but for convenience of explanation, n+14 is used. We will describe another method, which eliminates the effects of varying delay times without having to obtain the reference delay time TD in the reproduction apparatus used for reading. This method can check whether the disk is a legitimate disk or not by checking whether the positional relationship of mark 1 at address n in Figure 14(8) relative to another mark 2 matches or not. That is, TD is ignored as a variable, and the difference between the position, A1 = a1 + TD , of mark 1 measured and the position, A2 = a2 + TD , of mark 2 measured is obtained, which is given as A1 - A2 = a1 - a2 . At the same time, it is checked whether this difference matches the difference, a1 - a2, between the position a1 of the decrypted mark 1 and the position information a2 of the mark 2, thereby judging whether the disk is a legitimate disk or not. The effect of this method is that the positions can be checked after compensating for variations of the reference delay time TD by using a simpler constitution. (D) Next, the encrypted information writing process will be described. The position information read in the process (C) is first converted into ciphertext or "signed" with a digital signature. Then, the marking position information thus encrypted or signed is converted into a barcode as an ID unique to the optical disk, and the barcode is recorded in overwriting fashion in a prescribed region of a pre-pit area on the optical disk. Barcode patterns 584c - 584e in Figure 2(a) indicate the barcode written to the prescribed region of the pre-pit area, that is, in the innermost portion of the pre-pit area. Parts (1) to (5) of Figure 3 show the process from the recording of the barcode to the demodulation of the barcode detection signal by a PE-RZ modulated signal demodulator. In part (1) of Figure 3, the reflective layer is trimmed by a pulsed laser, and a barcode-like trimming pattern, such as shown in part (2) of the figure, is formed. At the playback apparatus (player), an envelope waveform some portions of which are missing, as shown in part (3) of the figure, is obtained. The missing portions result in the generation of a low level signal that cannot occur with a signal generated from an ordinary pit. Therefore, this signal is sliced by a second slice level comparator to obtain a low-reflectivity portion detection signal as shown in part (4) of the figure. In part (5) of the figure, the playback signal of the barcode is demodulated from this low-reflectivity portion detection signal by the PE-RZ modulated signal demodulator 621 which will be described in detail in the second-half part (II). It will be appreciated that, instead of the PE-RZ modulated signal demodulator 621, a pulse-width modulated signal demodulator (PWM demodulator) may be used, in which case also, a similar effect can be obtained.When applying the above encryption or digital signature, a secret key of a public key encryption function is used. As an example of the encryption, Figures 18A and 18B show an encryption process using an RSA function.As shown in Figure 1 5 A, the process consists of the following major routines: step 735a where marking position information is measured at the optical disk maker, step 695 where the position information is encrypted (or a digital signature is appended), step 698 where the position information is decrypted (or the signature is verified or authenticated) in the reproduction apparatus, and step 735w where a check is made to determine whether the disk is a legitimate optical disk or not.First, in step 735a, the marking position information on the optical disk is measured in step 735b. The position information is then compressed in step 735d, and the compressed position information H is obtained in step 735e.In step 695, the ciphertext of the compressed position information H is constructed. First, in step 695, a secret key, d, of 512 or 1024 bits, and secret keys, p and q, of 256 or 512 bits, are set, and in step 695b, encryption is performed using an RSA function. When the position information H is denoted by M, M is raised to d-th power and mod n is calculated to yield ciphertext C. In step 695d, the ciphertext C is recorded on the optical disk. The optical disk is thus completed and is shipped (step 735k).In the reproduction apparatus, the optical disk is loaded in step 735m, and the ciphertext C is decrypted in step 698. More specifically, the ciphertext C is recovered in step 698e, and public keys, e and n, are set in step 698f; then in step b, to decrypt the ciphertext C, the ciphertext C is raised to e-th power and the mod n of the result is calculated to obtain plaintext M. The plaintext M is the compressed position information H. An error check may be performed in step 698g. If no errors, it is decided that no alterations have been made to the position information, and the process proceeds to the disk check routine 735w shown in Figure 1 5 B. If an error is detected, it is decided that the data is not legitimate one, and the operation is stopped.In the next step 736a, the compressed position information H is expanded to recover the original position information. In step 736c, measurements are made to check whether the marking is actually located in the position on the optical disk indicated by the position information. In step 736d, it is checked whether the difference between the decrypted position information and the actually measured position information falls within a tolerance. If the check is OK in step 736e, the process proceeds to step 736h to output software or data or execute programs stored on the optical disk. If the check result is outside the tolerance, that is, if the two pieces of position information do not agree, a display is produced to the effect that the optical disk is an illegally duplicated one, and the operation is stopped in step 736g. RSA has the effect of reducing required capacity since only the ciphertext need be recorded. (E)The processing steps in the optical disk manufacturing process have been described above. Next, the constitution and operation of a reproduction apparatus (player) for reproducing the thus completed optical disk on a player will be described. The construction of an optical disk will be described first. A marking is formed on a reflective layer deposited on the optical disk. In the manufacturing process of the optical disk, the position of the marking was detected by position detecting means, and the detected position was encrypted as marking position information and written on the optical disk in the form of a barcode.Position information reading means reads the barcode, and decrypting means contained therein decrypts the contents of the barcode for output. Marking reading means reads the actual position of the marking and outputs the result. Comparing/judging means compares the decrypted result from the decrypting means contained in the position information reading means with the result of reading by the marking reading means, and judges whether the two agree within a predetermined allowable range. If they agree, a reproduction signal for reproducing the optical disk is output; if they do not agree, a reproduction stop signal is output. Control means controls the reproduction operation of the optical disk in accordance with these signals; when the reproduction stop signal is output, an indication to the effect that the optical disk is an illegal duplicated disk is displayed on a display and the reproduction operation is stopped. In the above operation, it will be recognized that it is also possible for the marking reading means to use the decrypted result from the decrypting means when reading the actual position of the marking.Namely in this case, the marking reading means checks whether the marking is actually located in the position on the optical disk indicated by the position information which is decrypted by the decrypting means.Thus the reproduction apparatus of the above construction can detect an illegally duplicated optical disk and stop the reproduction operation of the disk, and can prevent illegal duplicates practically. (II) We finish here the description of the first-half part (I), and now proceed to the description of the second-half part (II). This part focuses particularly on techniques, including a barcode formation method, used when barcoding the above marking position information (ID information) as a disk-unique ID. (A) Features of the optical disk of the present invention will be described. Then a barcode is recorded by laser trimming on the above-described single-plate disk, the protective layer 862 is destroyed, as explained in connection with Figure 10(b). Therefore, after laser trimming at a press factory, the destroyed protective layer 862 has to be reformed at the press factory. This means that a barcode cannot be recorded on the optical disk at a software company or a dealer that does not have the necessary equipment. The problem expected here is that the application of barcode recording is greatly limited.On the other hand, when the marking position information was recorded as a barcode by laser trimming on the laminated-type disk of the invention formed from two transparent substrates laminated together, it was confirmed that the protective layer 804 remained almost unchanged, as already explained in connection with Figure 10(a). This was confirmed by experiment by observing the disk under an optical microscope of 800X magnification. It was also confirmed that no change had occurred to the reflective film in the trimmed portion after an environmental test of 96 hours at a temperature of 85°C and a humidity of 95%.In this way, when the laser trimming of the present invention is applied to a laminated disk such as a DVD, there is no need to reform the protective layer at the factory. This offers a great advantage in that a barcode can be recorded by trimming on the optical disk at a place other than the press factory, for example, at a software company or a dealer. The usefulness of barcode recording on the laminated-type optical disk was thus confirmed.In this case, since the secret key information for encryption that the software company keeps need not be delivered to a party outside the company, security increases greatly, particularly when security information such as a serial number for copy prevention is recorded as a barcode in addition to the above-described position information. Furthermore, in the case of a DVD, since the barcode signal can be separated from DVD pit signals by setting the trimming line width at a value greater than 14T or 1.82 microns, as will be described later, the barcode signal can be recorded in the pit recording area on the DVD in superimposing fashion. The barcode formed in this way offers the effect that the barcode can be read by the optical pickup used to read the pit signal. This effect can be obtained not only with the laminated-type disk but also with the previously described single-plate disk.Thus, by applying the barcode forming method and modulation recording method of the invention to a laminated-type disk such as a DVD, a laminated-type optical disk can be provided that permits secondary recording after shipment from the factory. The above description has dealt mainly with a case in which the barcode is formed by laser trimming on a laminated-type disk of a two-layer, single-sided structure (with two reflective layers formed on one side). This single-sided, two-layered optical disk is the type of disk that permits playback of both sides from one side of the disk without having to turn over the disk.On the other hand, when trimming is performed on a double-sided, laminated-type optical disk that needs turning over when playing back the reverse side, the laser light passes through the two reflective films each formed on one side of the disk. Therefore, the barcode can be formed simultaneously on both sides. This provides an advantage for media fabrication in that the barcode can be recorded simultaneously on both sides in a single step.In this case, when the optical disk is turned over to play back the reverse side on a playback apparatus, the barcode signal is played back in just the opposite direction to the direction that the barcode signal on the front side is played back. A method for identifying the reverse side is therefore needed. This will be described in detail later. (B) Referring now to Figures 16 to 19, etc., we will describe the construction and operation of an optical disk barcode forming apparatus for converting the marking position information (ID number) into a barcode as a disk-unique ID and for recording the barcode in a prescribed region of a pre-pit area. A barcode recording method, etc. will also be described. (a) First, the optical disk barcode recording apparatus will be described with reference to Figure 16. Figure 16 is a diagram showing the configuration of the barcode recording apparatus for implementing an optical disk barcode forming method in one embodiment of the present invention. In the above mentioned embodiment, data to be barcoded is the data of encrypted version of marking position information. But the data to be barcode is not restricted to the above embodement. It may include, for example, input data and an ID number issued from an ID generator 908, as shown in Figure 16, or any other kind of data.In Figure 16, the input data and the ID number issued from the ID generator 908 are combined together in an input section 909; in an encryption encoder 830, the combined data is subjected to signature or encryption using an RSA function, etc. as necessary, and in an ECC encoder 907, error-correction coding and interleaving are applied. The encryption process and the playback process will not be described in detail.The data is then fed into an RZ modulator 910 where phase-encoding (PE) RZ modulation to be described later is performed. The modulating clock used here is created by a clock signal generator 913 in synchronism with a rotation pulse from a motor 915 or a rotation sensor 915a.Based on the RZ-modulated signal, a trigger pulse is created in a laser emitting circuit 911, and is applied to a laser 912 such as a YAG laser established by a laser power supply circuit 929. The laser 912 thus driven emits pulsed laser light which is focused through a converging unit 914 onto the reflective film 802 on the laminated disk 800, removing the reflective film in a barcode pattern. The error-correction method will be described in detail later. For encryption, a public key cipher, such as the one shown in Figure 18, is appended as a signature to the serial number with a secret key that the software company has. In this case, since no one other than the software company has the secret key and therefore cannot append a legitimate signature to a new serial number, this has an enormous effect in preventing illegal manufacturers from issuing a serial number. Since the public key cannot be deciphered, as previously described, the security is greatly enhanced. Disk piracy can thus be prevented even when the public key is recorded on the disk for delivery.The converging unit 914 in the optical disk barcode forming apparatus of the present embodiment will be described below in more detail.As shown in Figure 21(a), light emitted from the laser 912 enters the converging unit 914 where the entering light is converted by a collimator 916 into a parallel beam of light which is then converged in only one plane by a cylindrical lens 917, thus producing a stripe of light. This light is limited by a mask 918, and is focused through a converging lens 919 onto the reflective film 802 on the optical disk to remove the film in a stripe pattern. A stripe such as shown in Figure 28(b) is thus formed. In PE modulation, stripes are spaced apart at three different intervals, 1T, 2T, and 3T. If this spacing is displaced, jitter occurs and the error rate rises. In the present invention, the clock generator 913 generates a modulating clock in synchronism with a rotation pulse from the motor 915, and supplies this modulating clock to the modulator 910 to ensure that each stripe 923 is recorded at a correct position in accordance with the rotation of the motor 915, that is, with the rotation of the disk 800. This has the effect of reducing jitter. Alternatively, a laser scanning means 950, such as shown in Figure 3(1), may be provided by which a continuous-wave laser is scanned in a radial direction to form a barcode. (b) Next, a barcode recording method, etc., for forming a barcode using the above-described barcode recording apparatus, will be described with reference to Figure 17 to 19. Figure 17 shows signals coded with RZ recording (polarity return-to-zero recording) of the invention and trimming patterns formed corresponding to them. Figure 18 shows signals coded with a conventional barcode format and trimming patterns formed corresponding to them.The present invention uses RZ recording, as shown in Figure 17. In this RZ recording, one unit time is divided into a plurality of time slots, for example, a first time slot 920a, a second time slot 921, a third time slot 922, and so on. Then data is "00", for example, a signal 924a of a duration shorter than the period of the time slot, that is, the period T of a channel clock, is recorded in the first time slot 920a, as shown in part (1) in Figure 19. The pulse 924a whose duration is shorter than the period T of the recording clock is output between t=T1 and t=T2 . In this case, using a rotation pulse from the rotation sensor 915a on the motor 915, the clock signal generator 913 generates a modulation clock pulse as shown in part (1) of Figure 17; by performing the recording in synchronism with the clock pulse, the effects of rotational variation of the motor can be eliminated. In this way, as shown in part (2) of Figure 17, a stripe 923a indicating "00" is recorded on the disk within a recording region 925a, the first of the four recording regions shown, and a circular barcode such as shown in part (1) of Figure 20 is formed.Next, when data is "01", a pulse 924b is recorded in the second time slot 921b between t=T2 and t=T3 , as shown in part (3) in Figure 17. In this way, a stripe 923b is recorded on the disk within a recording region 926b, the second region from the left, as shown in part (4) of Figure 17.Next, when recording data "10" and "11", these data are recorded in the third time slot 922a and fourth time slot, respectively.Here, for comparison purposes, NRZ recording (non-return-to-zero recording) used for conventional barcode recording will be described with reference to Figure 18.In NZR recording, pulses 928a and 928b, each having a width equal to the period T of time slot 920a, are output, as shown in part (1) of Figure 18. In RZ recording, the width of each pulse is 1/nT; on the other hand, in the case of NZR recording, a pulse as wide as T is needed, and furthermore, when T appears successively, a pulse of double or triple width, 2T or 3T, becomes necessary, as shown in part (3) of Figure 18. In the case of laser trimming such as described in the present invention, changing the laser trimming width is practically difficult since it necessitates changing settings, and therefore, NRZ is not suitable. As shown in part (2) of Figure 18, stripes 929a and 929b are respectively formed in the first and third recording regions 925a and 927a from the left, and in the case of data "10", a stripe 929b of width 2T is recorded in the second and third recording regions 929b and 927b from the left, as shown in part (4) of Figure 18. In the conventional NRZ recording, the pulse widths are 1T and 2T, as shown in parts (1) and (3) of Figure 18; it is therefore apparent that NRZ recording is not suitable for the laser trimming as described herein. According to the laser trimming as described herein, a barcode is formed as shown in the experiment result shown in Figure 8(a), but since trimming line width differs from disk to disk, it is difficult to precisely control the line width; when trimming the reflective film on a disk, the trimming line width varies depending on variations in laser output, thickness and material of the reflective film, and thermal conductivity and thickness of the substrate. Further, forming slots of different line widths on the same disk will result in an increased complexity of the recording apparatus. For example, in the case of the NZR recording used for product barcode recording, as shown in parts (1) and (2) of Figure 18, the trimming line width must be made to precisely coincide with the period 1T of the clock signal, or 2T or 3T, that is, with nT. It is particularly difficult to record various line widths such as 2T and 3T by varying the line width for each bar (each stripe). Since the conventional product barcode format is an NRZ format, if this format is applied to the laser-recorded barcode of the present invention, the fabrication yield will decrease because it is difficult to precisely record varying line widths such as 2T and 2T on the same disk; furthermore, stable recording cannot be done since the laser trimming width varies. This makes demodulation difficult. Using RZ recording, has the effect of achieving stable digital recording even if the laser trimming width varies. Further, this offers the effect of simplifying the construction of the recording apparatus since RZ recording requires only one kind of line width and the laser power therefore need not be modulated.As described, by employing the above RZ recording for optical disk barcode recording, there is offered the effect of ensuring stable digital recording.An example of the phase-encoding (PE) modulation of RZ recording will be described with reference to Figure 19.Figure 19 shows signals and an arrangement of stripes when the RZ recording shown in Figure 17 is PE-modulated. As shown, data "0" is recorded in the left-hand time slot 920a of the two time slots 920a and 921a; on the other hand, data "1" is recorded in the right-hand time slot 921a, as shown in part (3) of Figure 19. On the disk, data "0" is recorded as a stripe 923a in the left-hand recording region 925a and data "1" as a stripe 923b in the right-hand recording region 926b, as shown in parts (2) and (4) of Figure 19, respectively. Thus, for data "010", a pulse 924c is output in the left-hand time slot for "0", a pulse 924d is output in the right-hand time slot for "1", and a pulse 924e is output in the left-hand time slot for "0", as shown in part (5) of Figure 19; on the disk, the first stripe is formed in the left-hand position, the second stripe in the right-hand position, and the third stripe in the left-hand position, by laser trimming. Figure 19(5) shows signals modulated with data "010". As can be seen, a signal is always available for every channel bit. That is, since the signal density is constant, the DC component does not vary. Since the DC component does not vary, PE modulation is resistant to variation in low-frequency components even if a pulse edge is detected during playback. This has the effect of simplifying playback demodulator circuitry of the disk playback apparatus. Furthermore, since one signal 923 is always available for every channel clock 2T, this has the effect of being able to reproduce a synchronization clock for a channel clock without using a PLL.A circular barcode, such as shown in Figure 20(1), is thus formed on the disk. Then data "01000", shown in part Figure 20(4), is recorded, in the PE-RZ modulation of the invention a barcode 923a having the same pattern as the recorded signal shown in part (3) is recorded as shown in part (2). Then this barcode is played back by an optical pickup, a signal waveform, such as shown in part (5) REPRODUCED SIGNAL, is output with portions thereof dropped corresponding to missing portions of a pit-modulated signal where no reflection signals are obtained due to removal of the reflective film, as explained with reference to part Figure 5(6). By passing this reproduced signal through a second-order or third-order LPF filter, the filtered signal waveform shown in Figure 20(6) is obtained. By slicing this signal by a level slicer, reproduced data "01000" of part (7) is demodulated. (C) We will next describe features of the optical disk format with a barcode formed in the above manner, tracking control methods, and rotational speed control methods that can be used when playing back the optical disk. (a) We will first describe the features of the optical disk format with a barcode formed according to the present embodiment, while dealing with an example of a condition that permits tracking control during playback (this condition is also referred to as the tracking ON condition). A playback operation using tracking control, and its details will not be given. In the case of a DVD disk in the present embodiment, all data are recorded in pits with CLV, as shown in Figure 30. Stripes 923 (forming a barcode) are recorded with CAV. CLV recording means recording with constant linear velocity, while CAV recording means recording with constant angular velocity.In the present invention, the stripes 923 are recorded with CAV, superimposed on a pre-pit signal in a lead-in data area holding an address which is recorded with CLV. That is, the data is overwritten with the stripes. In the present invention, the pre-pit signal area maps into all the data areas where pits are formed. The prescribed region of the pre-pit signal area, as mentioned in the present invention, corresponds to an inner portion of the optical disk; this region is also called a post-cutting area (PCA). In this PCA area, the barcode is recorded with CAV, superimposed on pre-bit signals. In this way, the CLV data is recorded with a pit pattern from the master disk, while the CAV data is recorded with laser-removed portions of the reflective film. Since the barcode data is written in overwriting fashion, pits are recorded between the barcode stripes 1T, 2T, and 3T. Using this pit information, optical head tracking is accomplished, and Tmax or Tmin of the pit information can be detected; therefore, motor rotational speed is controlled by detecting this signal.

Claims: An optical disk on which data including control data is recorded and comprising of a location (923) for receiving a barcode-like mark extending in a circumferential direction and having a plurality of bars (923a, 923b...) each extending in a radial direction, characterized in that said optical disk further comprises of an identifier (937) for indicating whether a barcode-like mark is present or not on said location (923) of the disk, said identifier (937) being provided in an area holding control data (936) and that at least a portion of said barcode-like mark overwrites a pre-pit area of said disk. An optical disk according to claim 1, wherein one of said bars (923a), when present, has a lower reflectivity than an average reflectivity of an area between said one of said bars (923a) and another of said bars (923b). An optical disk according to claim 1, wherein said pre-pit area is a portion of said disk at which pits are recorded.

Inventors: GOTOH YOSHIHO, KOISHI KENJI, MORIYA MITSURO, OSHIMA MITSUAKI, TANAKA SHINICHI, GOTOH, YOSHIHO, KOISHI, KENJI, MORIYA, MITSURO, OSHIMA, MITSUAKI, TANAKA, SHINICHI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1996
Main classification: G11B7
IPC codes: G11B20, G11B13, G11B23, G11B7, G06K19, G11B19, G11B5, G11B27, G06K1