JP3045897B2 - Recording and playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for reproducing information recorded in advance on a record carrier having a large number of tracks and / or for recording arbitrary information.

[0002]

2. Description of the Related Art As a conventional recording / reproducing apparatus, for example, there is an optical recording / reproducing apparatus. This optical recording / reproducing apparatus uses an information carrier (hereinafter referred to as a disc) in which an optically recordable / reproducible material film is formed on a surface of a substrate having tracks of concentric concavo-convex structure by vapor deposition or the like. The light is emitted from a light source such as a semiconductor laser onto the disk by a convergent lens, and the signal is read from the reflected light from the disk with a relatively weak constant light amount during signal reproduction, and the signal is recorded. In some cases, a signal is written by modulating the intensity of a light beam depending on a signal to be recorded.

In such an optical recording / reproducing apparatus, focus control is performed so that the light beam is always substantially converged on the recording material film, and the light beam is always positioned on a predetermined track. Tracking control is performed. One of several proposed methods of detecting a tracking error signal for performing tracking control is a sample servo method. The sample servo method detects a tracking error signal from a preformatted wobble mark. FIG.
FIG. 1 shows an example of a structure diagram of a sample servo type disk. The disk of the sample servo system is configured such that servo blocks for detecting servo signals alternately provided in the circumferential direction and data blocks on which data is written or written are divided on the disk. . Although only eight servo blocks are shown in FIG. 2 for simplification, in actuality, several thousand servo blocks are provided at substantially equal intervals around the disk. As a result, focus control and tracking control are performed using the servo signal detected from the servo block, and it is possible to sufficiently suppress surface deviation, eccentricity, and the like of the disk with sufficient accuracy. Since the servo blocks and the data blocks are provided alternately in the circumferential direction, there are also thousands of data blocks which are also distributed substantially equally around the disk. The servo block and the data block are configured so that their positions are aligned in the disk radial direction as shown in FIG.

FIG. 3 is an enlarged view of a servo block and a data block of a disk of a sample servo system. FIG.
As shown in (1), the servo block further includes a unique distance area, a pair of wobble marks, a clock mark, a focus area, and an address. Among them, the wobble mark, the clock mark, and the address are composed of pits having a concave-convex structure having an optical depth of approximately λ / 4 (the wavelength of the used light beam is λ). The wobble mark is a pair of pits distributed to the left and right from the center of the track. By comparing the amount of reflected light from each pit, the amount of deviation from the center of the track,
That is, a tracking error signal is detected. Technical details of a method of detecting a tracking error signal by a wobble mark are known to those skilled in the art, and are supervised by "Optical Disc Technology" by Morio Onoe.
Radio Technology Co., Ltd. Pages 79 to 98 1. Descriptions in prior art documents, such as Chapter 2.5 Focusing and Tracking Error Detection, are omitted. The address is an identifier for identifying individual tracks from a large number of tracks. The clock mark is for generating a servo clock for reading a wobble mark, an address, and the like. The focus area is an area for detecting a focus error signal for performing focus control, and is a flat mirror section having no pits. The servo clock is obtained by detecting clock marks arranged at equal intervals on the disk and generating a frequency-multiplied signal phase-synchronized with the clock marks. The unique distance area in the servo block is for generating a window for detecting a clock mark. The unique distance area is a continuous mirror section, and its length is set to be longer than a mirror section existing in another part of the data block or the servo block. The detection of the unique distance area is performed by “not detecting a pit for a predetermined period or more”.

[0005] In the servo block, the wobble mark, the address, the focus area, and the like are all provided at positions determined by the servo clock with respect to the clock mark. Therefore, in order to operate the tracking control, it is necessary to accurately detect the center position of the clock mark and detect the position of the wobble mark from the servo clock generated based on the center position. The same applies to reading the address of the track that the light beam follows. If the detection of the clock mark position fails or is erroneously detected, the tracking error signal is detected and the address is read by the reflected light from the disk at a position different from the original position. Erroneous reading of the address occurs. In order to reproduce or record the disk of the sample servo system as described above, it is extremely important to correctly and accurately detect the center position of the clock mark.

For this reason, the center position of the clock mark is detected by a center position detecting circuit having a configuration as shown in the block diagram of FIG. That is, the reproduced signal is output from the comparator 3
0 and input to the differentiating circuit 31. Comparator 30
Detects the presence or absence of a pit by binarizing a reproduced signal with a predetermined threshold value. The reproduced signal differentiated by the comparator 30 and the differentiation circuit 31 is input to a servo mark detection circuit 36 composed of a comparator 32, an inverter 33, and an AND gate 34. The zero-crossing point of the differentiated reproduction signal is detected by the comparator 32, and is gated by the signal output from the comparator 30 by the AND gate 34 via the inverter 33 and output. FIG. 8 shows a time chart when a disk of the sample servo system is reproduced by the center position detecting circuit. In FIG. 8, for simplification, it is assumed that the servo block is only a clock mark and a wobble mark as shown in FIG. FIGS. 8B to 8F show the reproduction signal, the differentiation circuit 31, the comparator 32, the comparator 30, and the AND signal, respectively.
This is an output signal of the gate 34. By gating the maximum and minimum points of the reproduced signal detected by the comparator 32 with the output of the comparator 30, the peak position, which is the center position of each pit, is accurately detected at the rising edge of the output signal of the AND gate 34. . The cutoff frequency fc of the differentiating circuit 31 is set so that the differentiating circuit 31 performs a differentiating operation on the frequency fs of the pit included in the reproduced signal.
The frequency characteristics are set as shown in FIG. In FIG. 9, the horizontal axis represents the frequency of a logarithmic scale, the gain is displayed in dB, and the phase is displayed in degrees.

The servo blocks are arranged radially from the center of the disk so that the phase and frequency of the servo clock need not be changed even if the light beam moves to another track. CAV (constant angul) that rotates at a constant angular velocity regardless of the position of
ar relocity) control is performed. Therefore, pits such as wobble marks and clock marks in the servo block are formed so that their circumferential angles are equal. That is, FIG.
As shown in the figure, the pit becomes longer toward the outer periphery. Similarly, pits of data in the data block are formed or recorded so as to have an equal circumferential angle. At this time, a servo clock can be used as a data clock for reproducing or recording data.

On the other hand, as the amount of information handled by computers has increased in recent years, the amount of information
In other words, the demand for large capacity is increasing. One of the methods for increasing the capacity of an optical disk is a method called zone bit recording. FIG. 5 shows a disc structure diagram of the zone bit recording, and FIG. 6 shows an enlarged view of a dotted line portion in FIG.
Shown in In zone bit recording, a disk is divided into concentric annular zones, and the circumferential angle of data pits is switched for each zone, so that the linear recording density of a data block is substantially constant at the inner and outer circumferences. As a result, the linear recording density, which has been reduced at the outer peripheral portion, can be improved to the same level as that at the inner peripheral portion, so that the capacity of the optical disc can be increased. However, the pits in the servo block are formed at the same circumferential angle as in the conventional case. This is because when the circumferential angle of the pits in the servo block is changed, the position of the wobble mark or address changes depending on the radial position, so that each time the light beam moves to another track, the phase and frequency of the servo block are changed. Is required to be changed.

[0009]

The zone bit recording discs shown in FIGS. 5 and 6 (the following are all related to the zone bit recording discs shown in FIGS. 5 and 6 and will be referred to as There is a method called zone CLV as a method of reproducing or recording information from a "disc". This is a method of switching the rotational angular velocity of the disk for each zone. Specifically, the rotational angular velocity is reduced toward the outer periphery so that a clock for reproducing data is constant.
As a result, the inner and outer data transfer rates become substantially constant. However, since the rotational angular velocity of the disk is switched for each zone, a long time is required for a search operation for moving to another track. Therefore, the zone CLV has a substantially constant data transfer rate, and is optimal for storing moving image data with high data continuity.

However, as described above, the servo block is formed with a constant circumferential angle. Therefore, the zone CL
In V, when the rotational angular velocity of the disk was reduced at the outer peripheral portion, the frequency of the clock mark and the address in the reproduced signal decreased by an amount proportional to the rotational angular velocity, and the frequency of the clock mark and the like now changed from fs to fs'. Then, as shown in FIG. 9, the output amplitude of the differentiating circuit is greatly reduced. As a result, the detection of the center position of the clock mark and the failure in reading the address may occur. This is shown in FIG. FIG. 10 is a time chart of each part of the center position detection circuit of FIG. 7 when the outer peripheral portion of the disk is operated in the zone CLV.
(A) to (f) in FIG. 10 are (a) to (f) in FIG.
Same as (f). As described above, since the servo block has a constant circumferential angle, the pits on the outer peripheral portion of the disk are longer than those on the inner peripheral portion, whereas the pits on the data block are almost the same as the inner peripheral portion. Has become. Here, when the rotational angular velocity of the disk is reduced, the frequency of the reproduced signal of the servo block is reduced (see FIG. 3C). As a result, the output amplitude of the differentiating circuit 31 is greatly reduced, and detection of a clock mark or the like fails.

An object of the present invention is to provide an apparatus capable of recording and reproducing data on a large-capacity optical disk with a substantially constant data transmission speed, while taking the above conventional problems into consideration.

[0012]

In order to solve the above problems, a recording / reproducing apparatus according to the present invention binarizes a reproduction signal to detect the presence or absence of a servo mark, an address reading circuit, and a reproduction signal. The circuit has a plurality of differentiating circuits having different cutoff frequencies for differentiating, and a servo mark detector for detecting the center position of the servo mark from the differential signal output from the differentiating circuit and the output signal from the comparator.

[0013]

With this configuration, at the outer peripheral portion of the disk,
By using the differentiated signal output by the differentiating circuit having a small cutoff frequency according to the read address value, even if the frequency of the servo mark of the signal changes due to a decrease in the rotational angular velocity of the disk, the amplitude of the differentiated signal decreases. Does not occur, the center position of the servo mark can be stably detected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A recording and reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a recording / reproducing apparatus according to one embodiment of the present invention. The disk 1 having the format shown in FIGS. 5 and 6 is rotated by a disk motor 2. A light source such as a semiconductor laser and optical components such as a focusing lens for focusing and irradiating a light beam on the disk 1, and for moving the light beam in a focus direction perpendicular to the disk 1 and a tracking direction perpendicular to tracks on the disk 1. An optical head 3 having an actuator, a photodetector for detecting the reflected light from the disk 1, and the like is mounted on a transfer table 4. The transfer table 4 moves the entire optical head 3 in the radial direction of the disc 1 by a drive signal applied to the transfer table 4.
The disc 1 is configured to be able to move largely from the innermost circumference to the outermost circumference. A head amplifier 5 for amplifying the output signal of the photodetector of the optical head 3 is also mounted on the transfer table 4. The output signal of the head amplifier 5 is input to a comparator 6 and differentiating circuits 7, 8, and 9. The comparator 6 binarizes the output signal of the head amplifier 5 by comparing it with a predetermined threshold value. Comparator 6
Are input to an address reading circuit 10 for reading an address provided in a servo block and an AND gate 16 for identifying each track. A zone identification signal corresponding to the address value read by the address reading circuit 10 is transmitted to the disk motor clock circuit 1.
2 and the multiplexer 14. The disk motor clock circuit 12 supplies a disk motor clock corresponding to the received zone identification signal to the disk motor control circuit 11. The disk motor 2 is provided with a pulse generator 13 that generates, for example, ten pulses with one rotation of the disk motor. The pulse output from the pulse generator 13 is input to the disk motor control circuit 12. The disk motor control circuit 12 controls the rotation angular velocity of the disk motor 2 so that the pulse frequency input from the pulse generator 13 and the frequency of the disk motor clock input from the disk motor clock generation circuit 11 become equal. It is. For example, disk 1 has 3
Assuming that there are two zones and the addresses corresponding to each zone and the rotational angular velocity of the disk motor 2 are as shown in Table 1, the zone identification output from the address reading circuit 10 according to the address read by the address reading circuit 10 is shown. The signal and the disk motor clock output from the clock generation circuit 11 are switched as shown in Table 2. Thus, the zone CLV operation for changing the rotational angular velocity of the disk 1 according to the zone is performed.

[0015]

[Table 1]

[0016]

[Table 2]

On the other hand, the outputs of the differentiating circuits 7, 8, and 9 are input to the multiplexer 14. The zone identification signal output from the address reading circuit 10 is input to the multiplexer 14, and the multiplexer 14 according to the zone identification signal, as shown in Table 2,
The outputs of 8 and 9 are selected and output to a mark detection circuit 18 composed of a comparator 15, an inverter 17, and an AND gate 16. The operation of the servo mark detection circuit 18 is the same as that of the servo mark detection circuit 36 shown in FIG.

The differentiating circuits 7, 8, and 9 have different cutoff frequencies fc as shown in FIG.
1, fc2, fc3, and fc1,
fc2 and fc3 satisfy the following relationship.

Fc1>fc2> fc3 That is, as shown in FIG. 1, the differentiating circuits 7, 8, and 9 are composed of a resistor R, a capacitor C, and an operational amplifier. If the resistors R are all equal, C1 <C2 <C3 and 0, When the disk 1 is rotated at the angular velocities shown in Table 1 in the zones 1 and 2 and the reproduction signal frequencies of the clock marks in the servo block output from the head amplifier 5 are fs1, fs2 and fs3, respectively. fs1 / fc1 = fs2 / fc2 = fs3 / fc3 = Δf.

As a result, when the rotational angular velocity of the disk decreases in the outer peripheral portion in the zone CLV, the frequency of a clock mark or the like in the reproduced signal decreases in proportion to the rotational angular velocity, and changes from fs1 to fs3 or from fs1 to fs2. However, the input and output gain and phase in the differentiating circuit are kept in a constant relationship. As a result, in the detection of the center position, the output amplitude of the differentiating circuit hardly occurs, and the reading of the clock mark and the address does not fail.

FIG. 12 shows a zone CLV at the outermost periphery of the disk.
2 is a time chart of each part of FIG. FIG. 12A is a diagram showing the arrangement of pits in the servo block and the data block at the outermost periphery of the disk as in FIG. 10A, and FIGS. 12B to 12F are diagrams in FIG.
Are the output signals of the head amplifier 5, multiplexer 14, comparator 15, comparator 6, and AND gate 16 when the light beam follows the track center at a constant speed. In FIG. 12A, only the wobble mark and the clock mark are shown in the servo block for simplification.

Now, it is assumed that the light beam is located in the outermost peripheral zone. At this time, based on the read address value, the address reading circuit 10 outputs the zone identification signal '3' indicating that the zone is located in the outermost zone from the disk motor clock generating circuit 11 and the multiplexer 14. As a result, the disk motor 2 is rotating at the rotational angular velocity of the outermost peripheral zone. Therefore, as shown in FIG. 12B, the frequency of the reproduction signal corresponding to the pit of the servo block is fs3 in the reproduction signal output from the head amplifier 5.
To decline. However, at the same time multiplexer 14
Also selects the output signal of the differentiating circuit 9, and its cutoff frequency is also set to fc3. For this,
The amplitude of the differential signal output from the multiplexer 14 in the servo block hardly decreases (FIG. 10C).
reference). As a result, the position of the clock mark or the like of the servo block is detected without omission by the comparator 15 and the AND gate 16 ((d) to (f) in the same drawing).

In this embodiment, the address provided on the disk 1 is read, and the differentiating circuit to be used is switched based on the address. However, the rotational angular velocity of the disk motor 2 or the disk 1 is changed instead of the read address. Obviously, the same effect can be obtained by detection. Since the rotational angular velocity of the disk motor 2 or the disk 1 is directly related to the frequency of a clock mark or the like in the reproduction signal, it is effective even during a transient response in which the rotational angular velocity of the disk motor 2 is changing. Another advantage is that the differentiation circuit can be switched.

In this embodiment, a plurality of differentiating circuits having different characteristics are provided and switched, but it is also possible that one differentiating circuit capable of changing the characteristics can be used instead. Imagine

Further, in this embodiment, the number of zones is three, but it is apparent that the present invention is not limited by the number of zones. In addition, the configuration is such that a differentiating circuit is provided for each zone and switching is performed. However, it is added that the number of zones and the number of differentiating circuits do not necessarily have to correspond one-to-one. When the number of zones is large, it is naturally possible to cover a plurality of zones with one differentiation circuit.

[0026]

As is apparent from the above description of the embodiment, the present invention uses a differential signal output from a differentiating circuit having a small cutoff frequency in accordance with the read address value in the outer peripheral portion of the disk. Even if the frequency of the servo mark of the reproduction signal changes due to a decrease in the rotational angular velocity of the disk, the amplitude of the differential signal does not decrease, so that the center position of the servo mark can be detected stably.

[Brief description of the drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is a structural view of a sample servo type disk.

FIG. 3 is an enlarged view of a servo block and a data block of a sample servo type disk;

FIG. 4 is an enlarged structural view of a sample servo type disk.

FIG. 5 is a disc structure diagram of zone bit recording.

FIG. 6 is an enlarged structural diagram of a zone bit recording disc.

FIG. 7 is a block diagram of a conventional center position circuit.

FIG. 8 is a time chart when a sample servo type disc is reproduced by a conventional apparatus.

FIG. 9 is a characteristic diagram of a differential circuit.

FIG. 10 is a time chart when a sample servo type disc is reproduced by a conventional apparatus.

FIG. 11 is a characteristic diagram of the differentiating circuit according to the embodiment of the present invention.

FIG. 12 is a time chart when a sample servo type disc is reproduced in the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 disk 2 disk motor 3 optical head 4 transfer table 5 head amplifier 6 comparator 7 differentiating circuit 8 differentiating circuit 9 differentiating circuit 10 address reading circuit 11 disk motor clock generating circuit 12 disk motor control circuit 13 pulse generator 14 multiplexer 15 comparator 16 comparator 17 Inverter

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Kino 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-274796 (JP, A) JP-A-5 −41046 (JP, A) JP-A-5-258468 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 20/10 G11B 19/247

Claims (8)

(57) [Claims] 1. A recording / reproducing apparatus using a record carrier having a track having an address and a mark for causing a light beam for recording or reproducing information to follow the track radially with respect to a center of rotation. Rotating means for rotating the recording medium at an arbitrary angular velocity, detecting means for irradiating the record carrier with a light beam to detect the amount of reflected light, and detecting the presence or absence of the mark by comparing an output signal of the detecting means with a predetermined value. Comparing means, an address reading means for reading the address from the output signal of the detecting means, a plurality of differentiating means having different cut-off frequencies for differentiating the output of the detecting means, and one of the plurality of differentiating means. The timing at which the light beam is located on the center of the mark is detected from the selected differential signal output from the differentiating means and the output signal from the comparing means. A recording / reproducing apparatus having mark detecting means for changing the angular velocity of rotation of the record carrier by the rotating means in accordance with the address read by the address reading means, and selecting the differentiating means selected by the mark detecting means. A recording / reproducing apparatus characterized by switching. 2. The method according to claim 1, wherein as the track following the light beam is further away from the center of rotation, the rotating means reduces the angular velocity of rotating the record carrier and selects a differentiating means having a small cutoff frequency. The recording / reproducing apparatus according to claim 1. 3. A recording / reproducing apparatus using a record carrier having a track having an address and a mark for causing a light beam for recording or reproducing information to follow the track radially with respect to the center of rotation. Rotating means for rotating at an arbitrary angular velocity, angular velocity detecting means for detecting the angular velocity of rotation of the record carrier, detecting means for irradiating the record carrier with a light beam and detecting the amount of reflected light, and the detecting means Comparison means for comparing the output signal with a predetermined value to detect the presence or absence of the mark, address reading means for reading the address from the output signal of the detection means,
A plurality of differentiating means having different cutoff frequencies for differentiating the output of the detecting means; a differential signal output from one differentiating means selected alternatively from the plurality of differentiating means; and a light beam based on an output signal of the comparing means. Is a recording and reproducing apparatus having a mark detecting means for detecting a timing located on the center of the mark, wherein the rotating means changes the angular velocity of rotation of the record carrier according to the address read by the address reading means, A recording / reproducing apparatus, wherein the differentiating means selected by the mark detecting means is changed according to the angular velocity detected by the angular velocity detecting means. 4. The rotating means decreases the angular velocity of rotating the record carrier as the track following the light beam is separated from the center of rotation, and the mark detecting means cuts as the angular velocity detected by the angular velocity detecting means decreases. 4. The recording / reproducing apparatus according to claim 3, wherein differentiating means having a small off-frequency is selected. 5. A recording / reproducing apparatus using a record carrier having a track having an address and a mark for causing a light beam for recording or reproducing information to follow the track radially with respect to the center of rotation. Rotating means for rotating the recording medium at an arbitrary angular velocity, detecting means for irradiating the record carrier with a light beam to detect the amount of reflected light, and detecting the presence or absence of the mark by comparing an output signal of the detecting means with a predetermined value. Comparing means, an address reading means for reading the address from an output signal of the detecting means, a differentiating means capable of selecting a cutoff frequency for differentiating an output of the detecting means, a differential signal outputted from the differentiating means, A recording / reproducing apparatus having mark detection means for detecting a timing at which a light beam is positioned on the center of the mark from an output signal of the comparison means; A recording / reproducing apparatus, wherein the rotating means changes an angular velocity of rotation of the record carrier and a cutoff frequency of the differentiating means in accordance with an address read by the address reading means. 6. The rotating means reduces the angular velocity of rotating the record carrier and the differentiating means reduces the cutoff frequency as the track following the light beam is separated from the center of rotation. Item 6. The recording / reproducing device according to Item 5. 7. A recording / reproducing apparatus using a record carrier having a track having an address and a mark for causing a light beam for recording or reproducing information to follow the track radially with respect to the center of rotation. Rotating means for rotating at an arbitrary angular velocity, angular velocity detecting means for detecting the angular velocity of rotation of the record carrier, detecting means for irradiating the record carrier with a light beam and detecting the amount of reflected light, and the detecting means Comparison means for comparing the output signal with a predetermined value to detect the presence or absence of the mark, address reading means for reading the address from the output signal of the detection means,
A differentiating means capable of selecting a cutoff frequency for differentiating the output of the detecting means, and detecting a timing at which the light beam is positioned on the center of the mark based on a differential signal output from the differentiating means and an output signal of the comparing means. A recording / reproducing apparatus having a mark detecting means, wherein the rotating means changes the angular velocity of rotation of the record carrier in accordance with the address read by the address reading means, and the differentiation is performed in accordance with the angular velocity detected by the angular velocity detecting means. A recording / reproducing apparatus characterized by changing a cutoff frequency of the means. 8. The rotating means reduces the angular velocity of rotating the record carrier as the track following the light beam is separated from the center of rotation, and the differential means cuts off as the angular velocity detected by the angular velocity detecting means decreases. The recording / reproducing apparatus according to claim 7, wherein the frequency is reduced.