JP2002183986A - Disk player - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly realize focusing servo and tracking servo having high precision regardless of a change in temperature, in a disk player which reproduces signals from a disk by irradiating the disk with laser beams from an optical head. SOLUTION: The disk player is provided with a reproducing signal amplifying circuit 5 which generates error signals in accordance with a deviation of focusing or tracking of an optical head 4, a servo circuit 6 which controls focusing or tracking for the optical head 4 based on the error signals, a temperature sensor 16 which detects a temperature of the optical head 4, a system controller 10 which obtains the optimal value of an offset to the error signals when a changing quantity of detected temperature exceeds a prescribed threshold, and an adding machine 21 which applies an offset adjustment to the error signals based on the optimal offset value. Focusing or tracking for the optical head 4 is controlled based on the error signals to which the offset adjustment is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk reproducing apparatus for irradiating a disk with laser light from an optical head and reproducing a signal from the disk.

[0002]

2. Description of the Related Art Hitherto, as a recording medium of a disk recording / reproducing apparatus capable of recording a signal on a disk and reproducing a signal from the disk, it is rewritable, has a large storage capacity, and has high reliability Magneto-optical disks have been developed and are widely used as external memories of computers and audio-visual devices. Particularly in recent years, lands (17) and grooves (18) are alternately formed on the signal surface of the magneto-optical disk (1) as shown in FIG. A technology has been developed to increase the recording density by recording data.

The land (17) and the groove (18) meander (wobble) as shown in the figure, and the meandering frequency is FM-modulated at a predetermined center frequency. By controlling the rotation of the magneto-optical disk so that the detected wobble signal always has the center frequency, constant linear velocity control is realized. Further, the wobble signal is subjected to FM modulation as described above and contains various information (wobble information) such as address information. At the time of signal reproduction, various control operations are realized based on the wobble information. You.

In a disk recording / reproducing apparatus, during signal reproduction or recording, a focus servo or tracking servo is executed on an actuator incorporated in an optical head based on a focus error signal or a tracking error signal. Thus, a good focus state and tracking state can be obtained. When the disk recording / reproducing apparatus is started, the focus and tracking offsets are adjusted so that focus servo and tracking servo in subsequent signal reproduction and signal recording are performed with high accuracy.

[0005]

However, in a disk recording / reproducing apparatus, with a change in environmental temperature,
Distortion of the housing and parts of the optical head, displacement of the optical sensor, change in the laser wavelength, etc. occur, and these factors may cause the offset to deviate from the optimum value, resulting in reduced accuracy of the focus servo and tracking servo. I do. If the offset value greatly deviates from the optimum value T as shown in FIG. 7, the bit error rate of the reproduction signal exceeds the threshold value Rbt, and normal reproduction operation becomes difficult. SUMMARY OF THE INVENTION An object of the present invention is to provide a disk reproducing apparatus in which focus servo and tracking servo with high accuracy are always performed regardless of a change in environmental temperature.

[0006]

According to the present invention, there is provided a disk reproducing apparatus comprising: an error signal generating means for generating an error signal corresponding to a shift in focus or tracking of an optical head; Control means for controlling focus or tracking, temperature detection means for detecting a temperature near the optical head, and calculation for obtaining an optimum value of an offset with respect to the error signal when a change in the detected temperature exceeds a predetermined threshold. Processing means, comprising, based on the determined optimum offset value, offset adjustment means for performing offset adjustment on the error signal,
Based on the error signal subjected to the offset adjustment,
The focus or tracking of the optical head is controlled.

In the disk reproducing apparatus of the present invention, the temperature near the optical head is monitored not only at the time of start-up but also during signal reproduction, and when a large temperature change occurs, the focus or tracking at the time is detected. An optimum offset value for the error signal corresponding to the deviation is obtained, and offset adjustment is performed based on the optimum offset value. As a result, an error signal subjected to an optimal offset adjustment according to the temperature is reproduced, and the focus or tracking of the optical head is accurately controlled based on the error signal.

In determining the optimum offset value,
A method for detecting a signal reproduction state detecting element such as a bit error rate or a signal level of a reproduction signal while actually changing the offset value, and setting an offset value when a good signal reproduction state is obtained as an optimum value. Can be adopted.

As a method of detecting an optimum signal reproduction state, a method of detecting a signal reproduction state detecting element while gradually changing an offset value and searching for an optimum point can be employed. As a method for speeding up the processing, the values of the signal reproduction state detecting elements at at least three offset values are detected, these values are approximated by a quadratic curve, and the center value passing through the vertex of the quadratic curve is optimized. A method of setting an offset value can be adopted.

Further, in a disk reproducing apparatus in which the power of a laser beam is controlled in accordance with a change in temperature or the like, the optimum offset value changes depending on the magnitude of the laser power. By correcting the optimal value of, it is possible to realize more accurate signal reproduction.

[0011]

According to the disk reproducing apparatus of the present invention, highly accurate focus servo and tracking servo are always performed regardless of a change in environmental temperature.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention applied to a disk recording / reproducing apparatus using a magneto-optical disk as a recording medium will be specifically described with reference to the drawings. As shown in FIG. 1, a disk recording / reproducing apparatus according to the present invention includes a spindle motor (2) for rotating and driving a magneto-optical disk (1). In addition, a laser drive circuit (1
5), an optical head (4), a reproduction signal amplification circuit (5), a reproduction signal detection circuit (7), and an error correction circuit (11). At the time of signal reproduction, the laser drive circuit (15) controls the optical head (4). Is driven to irradiate the magneto-optical disk (1) with laser light.

On the other hand, a magnetic head drive circuit (14) and a magnetic head (3) are provided as a signal recording system.
The laser drive circuit (15) and the optical head (4) operate to locally heat the magneto-optical disk (1). Further, as a control system, a temperature sensor (16), an A / D converter (2)
0), system controller (10), memory (9), D / A converter (19), adder (21), servo circuit (6), external synchronization signal generation circuit (8), delay circuit (12) and A timing pulse generating circuit (13) is provided.

The optical head (4) irradiates the laser beam to the magneto-optical disk (1) and detects the reflected light as an optical signal and a magneto-optical signal. The reproduction signal amplification circuit (5) is an optical head
After amplifying the optical signal and magneto-optical signal obtained from (4),
A focus error signal and a tracking error signal included in the optical signal are supplied to a servo circuit (6). The reproduction signal amplification circuit (5) supplies an optical signal detected due to the discontinuous area formed at a constant interval in the groove of the magneto-optical disk (1) to the external synchronization signal generation circuit (8). At the same time, a magneto-optical signal is supplied to a reproduction signal detection circuit (7).

An external synchronizing signal generating circuit (8) generates an external synchronizing signal and supplies it to a servo circuit (6), a reproduced signal detecting circuit (7), and a delay circuit (12). The servo circuit (6) includes an actuator mounted on the optical head (4) based on the focus error signal and the tracking error signal.
A focus servo and a tracking servo are executed for an (not shown), and the rotation of the spindle motor (2) is controlled based on an external synchronization signal.

The reproduction signal detection circuit (7) supplies the detected reproduction signal to the error correction circuit (11), and the error correction circuit (11)
Demodulates the reproduction signal, detects an error in the reproduction data obtained thereby, corrects the error, and outputs the corrected reproduction data to the subsequent circuit. The delay circuit (12) creates a synchronization signal in which the phase of the external synchronization signal is delayed by a predetermined time, and outputs the synchronization signal to the timing pulse generation circuit (13). When recording a signal, the timing pulse generation circuit (13) uses the recording data modulated by a predetermined method and a delay circuit.
Receiving the synchronization signal input from (12), the
Generate a pulse signal for applying an alternating magnetic field to (1),
A pulse signal (write clock) for irradiating the magneto-optical disk (1) with pulse light is generated and supplied to the laser drive circuit (15). The timing pulse generating circuit (13) generates a pulse signal for irradiating the magneto-optical disk (1) with a pulse light based on the synchronization signal from the delay circuit (12) when reproducing the signal.
(Read clock) is generated and supplied to the laser drive circuit (15), the reproduction signal detection circuit (7), and the error correction circuit (11).

The magnetic head drive circuit (14) generates a drive signal for the magnetic head (3) based on the pulse signal from the timing pulse generation circuit (13). Magnetic head (3)
Applies an alternating magnetic field to the magneto-optical disk (1) based on a drive signal from the magnetic head drive circuit (14). The laser drive circuit (15) drives a semiconductor laser (not shown) provided in the optical head (4) based on a pulse signal from the timing pulse generation circuit (13). The optical head (4) generates a laser beam based on a drive signal from the laser drive circuit (15) and irradiates the magneto-optical disk (1).

The output signal of the temperature sensor (16) is supplied to a system controller (10) after being converted into temperature data via an A / D converter (20). System controller (1
0) controls the operation of the delay circuit (12) based on the external synchronization signal obtained from the external synchronization signal generation circuit (8). Further, the system controller (10) executes an offset adjustment procedure described later based on the error correction number EC obtained from the error correction circuit (11) and the temperature data obtained from the A / D converter (20). Then, an optimum offset value for the focus error signal and the tracking error signal is obtained, and both the optimum offset values are output to the D / A converter (19). The optimum offset signal for the focus error signal and the tracking error signal obtained from the D / A converter (19) is an adder.
(21) to be added to the focus error signal and the tracking error signal from the reproduction signal amplifier circuit (5), respectively, whereby the offset adjustment is performed on both signals. The focus error signal and the tracking error signal that have been subjected to the offset adjustment are input to the servo circuit (6), and are provided to the focus servo and the tracking servo.

FIG. 2 shows a general flow of the offset adjustment procedure executed by the system controller 10 during signal reproduction. First, in step S1, occurrence of a large temperature change exceeding a predetermined value is detected. Then, in step S2, the idle time of data processing using the buffer in the memory is detected, and at the time of the detection, step S3
Then, the procedure for optimizing the offset values for the focus error signal Fo and the tracking error signal Tr is repeated. .

FIG. 3 shows a specific procedure of step S1. First, in step S11, an initial value (initial temp) is added to the temperature data TEMP representing the immediately preceding temperature.
Is written, the output of the temperature sensor is monitored in step S12, and the temperature data SENTe representing the current temperature is monitored.
Get mp. Next, in step S13, the temperature difference TN is calculated by subtracting the immediately preceding temperature data TEMP from the current temperature data SENtemp. Then, step S14
Then, it is determined whether or not the temperature difference TN exceeds a predetermined threshold Threshold. If the determination is NO, the process returns to step S12 to monitor the temperature sensor. On the other hand, when the temperature difference TN is greater than the predetermined threshold value Threshold, and when the answer is YES in step S14, the process proceeds to step S15, where the immediately preceding temperature data TE
The current temperature data SENtemp is substituted for MP. Thereafter, in step S16, execution of offset adjustment is requested.

When the interrupt request for executing the offset adjustment is generated as described above, the system controller 10 monitors the memory at the end of one recording or reproduction process by the MPU as shown in FIG. After confirming the capacity, a message is issued to allow offset adjustment. For example, if it is confirmed that the recording data buffer is almost empty during the recording operation and that the reproduction data buffer is almost full during the reproducing operation, an offset adjustment permission message is issued.

The specific procedure of the offset adjustment shown in FIG. 4 is executed according to the offset adjustment permission message. In the offset adjustment for the focus error, first, in step S31, the offset value FOre is set.
After changing g by a predetermined value i (i = 0, ± 1, ± 2,... ± N), in step S32, a signal is reproduced (read) from a test track provided in advance on the magneto-optical disk. Then, in step S33, the offset value F.
Error correction number Err [(F.
O.reg)] and calculates the error correction number Err (i)
Hold as. Then, the predetermined value i is increased or decreased, and the process returns to step S31, and the test track is read by changing the offset value FO.reg with the predetermined value i.

As a result, all offset values FO.reg
Then, the test track is read, and the error correction number Err (i) of the reproduced data is held, and then step S34 is performed.
Then, the minimum error correction number Min [Err (i)] is selected, and in step S35, the change amount i of the offset value that realizes the minimum error correction number is set as the output value Output. In this way, the optimum offset value for the focus error is obtained.

Thereafter, in the offset adjustment for the tracking error, first, in step S36, the offset value TOreg is set to a predetermined value j (j = 0, ± 1, ± 2,...).
. ± .N), at step S37, a signal is reproduced (read) from a test track provided in advance on the magneto-optical disk, and at step S38, the signal at the offset value T.O.reg at that time is read. The error correction number Err [(TOreg)] of the reproduced data is calculated, and the result is held as the error correction number Err (j). Then, the predetermined value j is increased or decreased, and the process returns to step S36,
By changing the offset value T.O.reg with the predetermined value j,
Read the test track.

As a result, all offset values T.O.reg
Then, the test track is read, and the error correction number Err (j) of the reproduced data is held.
Then, the minimum error correction number Min [Err (j)] is selected, and in step S40, the change amount j of the offset value that realizes the minimum error correction number is set as the output value Output. In this way, the optimum offset value for the tracking error is obtained.

The optimum offset values for the focus error and the tracking error are output to the D / A converter (19) shown in FIG. Adjustment is performed. As a result, in the servo circuit (6), an appropriate focus error signal and tracking error signal are always generated irrespective of the temperature change near the optical head (4), thereby realizing highly accurate focus servo and tracking servo. Is done.

The offset adjustment for the focus error and the tracking error at the time of signal recording can be performed in the same manner. After the optimum offset value is obtained by the above-described offset adjustment procedure, the optimum value is set to:
By multiplying the ratio (Pw / Pr) of the laser power Pr at the time of signal recording and the laser power Pw at the time of signal reproduction, an optimum offset value at the time of signal recording can be obtained.

The configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims. For example, the adjustment according to the temperature near the optical head includes not only the offset values for the focus error and the tracking error, but also various gains of the servo circuit.
(Servo gain) is also effective.

In a disk recording / reproducing apparatus which changes laser power in accordance with the temperature of a magneto-optical disk or the like, the optimum offset or servo gain is corrected in accordance with the change in laser power so that the laser power can be changed regardless of the laser power. A highly accurate servo operation can always be realized. That is, the gain is inversely proportional to the power, and the offset is proportional to the power.
f, Gain adjustment result is Gain_ref, playback power at adjustment is P
When r_ref is used, the optimum servo gain Gain and the optimum offset Offset when the laser power is changed from Pr_ref to Pr or Pw can be calculated by the following equations. However, Pw at this time is an optical effective value. In other words, in the case of so-called DC irradiation recording in which laser irradiation is always performed, the following formula may be used. In other cases, in other words, in the case of pulse irradiation recording in which laser pulse emission is performed, The effective value is converted according to the ratio and applied to the next Pw.

Offset correction (at the time of reproduction) Offset = Offset_ref × Pr / Pr_ref Offset correction (at the time of recording) Offset = Offset_ref × Pw / Pr_ref Gain correction (at the time of reproduction) Gain = Gain_ref × Pr_ref / Pr Gain correction (at the time of recording) Gain = Gain_ref × Pr_ref / Pw

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a disk recording / reproducing apparatus according to the present invention.

FIG. 2 is a flowchart showing an overall flow of an offset adjustment procedure in the device.

FIG. 3 is a flowchart illustrating a specific temperature change detection procedure in the offset adjustment procedure.

FIG. 4 is a flowchart illustrating a specific offset optimization procedure in the offset adjustment procedure.

FIG. 5 is a time chart illustrating a flow of a process executed by a system controller.

FIG. 6 is a perspective view showing lands and grooves formed on the magneto-optical disk.

FIG. 7 is a graph showing a relationship between an offset value for a focus error or a tracking error and a bit error rate.

[Explanation of symbols]

 (1) Magneto-optical disk (4) Optical head (6) Servo circuit (10) System controller (11) Error correction circuit (21) Adder

Continuation of the front page (72) Inventor Shuno Yano 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5D075 AA03 CE01 5D118 AA13 AA20 BB06 CA08 CA09 CD02 CD03 CD08 CD11

Claims (5)

[Claims] 1. A disk reproducing apparatus for irradiating a disk with laser light from an optical head and reproducing a signal from the disk, comprising: an error signal generating means for generating an error signal corresponding to a shift in focus or tracking of the optical head; A control unit that controls focus or tracking of the optical head based on the error signal, a temperature detection unit that detects a temperature near the optical head, and when a change amount of the detected temperature exceeds a predetermined threshold, An arithmetic processing unit for obtaining an optimum value of an offset with respect to the error signal; and an offset adjusting unit for performing an offset adjustment on the error signal based on the obtained optimum offset value. The focus or tracking of the optical head is controlled based on the That disk reproducing apparatus. 2. The disk according to claim 1, wherein the arithmetic processing means detects a signal reproduction state while changing the offset value, and determines an offset value when a good signal reproduction state is obtained as an optimum value. Playback device. 3. The disk reproducing apparatus according to claim 2, wherein the arithmetic processing means detects the quality of the signal reproduction state by using a bit error rate or a signal level of the reproduction signal as a signal reproduction state detection element. 4. The arithmetic processing means according to claim 3, wherein the value of the signal reproduction state detection element at least at three offset values is approximated by a quadratic curve, and a center value of the quadratic curve is set as an optimum offset value. Disk playback device. 5. The arithmetic processing means corrects an optimum value of the offset according to the power of the laser beam.
The disk reproducing apparatus according to claim 4.