JP2913593B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device,
In particular, the present invention relates to an optical disc apparatus in which access control for searching for an arbitrary desired track on an optical disc is improved.

[0002]

2. Description of the Related Art An optical disk device has the characteristics that it can record or reproduce information at a high density without contact and can randomly access a target track at a high speed.

FIG. 2 is a block diagram showing a configuration of an access control unit of a conventional optical disk device. In the figure, 2
Reference numeral 1 denotes an optical disc having a recording film 27 for recording information, and is driven at a predetermined rotation speed by a spindle motor 20. FIG. 3 shows a track configuration of the continuous groove type optical disk 21 conforming to the ISO standard. In this case, in particular, an ID area in which disk address information and the like are previously formed by uneven pits is shown in an enlarged manner. It is. A guide groove (hereinafter, referred to as a pre-groove) 16 is provided for tracking control, and is about 1.6 μm.
They are arranged at pitch intervals. Pre-format part 17
Is an area in which address information and the like of the disk are recorded in advance in pits 15 having irregularities, and the data recording section 19 is an area for recording user information. A mirror section 18 between the pre-format section 17 and the data recording section 19 is provided for detecting an offset of a tracking signal and the like, and this section is a mirror area without the pre-groove 16. .

An optical head 30 for reading information recorded on a recording film 27 has a semiconductor laser element 2 as a light source.
2, collimator lens 23, deflection beam splitter 2
A quarter-wave plate 25, an objective lens 2 for converging laser light as a light spot having a diameter of about 1 μm on a recording film 27.
6. A two-divided photodetector 29 for receiving the return light from the recording film 27 through the focus lens 28 and converting the amount of light into a current, an actuator 31 and the like. The optical head 30 is further moved by a linear motor 32.
The entire optical head 30 is configured to be movable in the radial direction of the optical disk 21.

[0005] The differential amplifier circuit 40 calculates a tracking error signal 50 from the output signals of the two light receiving elements of the photodetector 29.
0 is generated. The tracking error signal 500 generated here is used for the tracking control circuit 41.
And input to the binarization circuit 45. The tracking control circuit 41 drives the actuator 31 according to the tracking error signal 500, and the light spot is
So-called tracking control is performed so as to follow the track along (between adjacent pregrooves 16).

On the other hand, when performing random access control, first, the tracking control is turned off by a microcomputer not shown, and the linear motor 3 is turned off.
2 to move the entire optical head 30 to any desired track. When the optical head 30 is moved in a state where the tracking control is OFF, a tracking error signal 500 having a sine wave shape is output from the differential amplifier circuit 40 every time the light spot crosses the track. This tracking error signal 5
00 is a track crossing signal 501 in which a pulse is generated by the binarization circuit 45 only at the rising portion of the tracking error signal 500. This track crossing signal 501 is
After being corrected by the track crossing correction circuit 50, the speed detection circuit 4 outputs a corrected track crossing signal 503.
3 and the target speed generating circuit 44. The speed detection circuit 43 detects the moving speed of the optical head 30 from the pulse generation period of the corrected track crossing signal 503, and this signal is input to the linear motor control circuit 42. The target speed generating circuit 44 counts the number of tracks crossed by the light spot based on the number of pulses of the corrected track crossing signal 503, and generates a target speed signal according to the number of remaining moving tracks to the desired track. The target speed signal is also input to the linear motor control circuit 42. In the linear motor control circuit 42, the input optical head 30
The linear motor 32 is controlled so that the moving speed becomes equal to the target speed, so that the optical head 30 can move to any desired track accurately.

Next, the operation of the track crossing correction circuit 50 will be described in more detail with reference to FIGS.
FIG. 4A shows the tracking error signal 500, and the time t0 to t1 shows a state where the light spot has passed through the mirror unit 18, for example. When a light spot passes through the mirror section 18, light diffraction does not occur in this portion, so that the tracking error signal 500 should have a waveform shown by a dotted line, but has a waveform shown by a solid line. FIG. 4B shows a track crossing signal 501 output from the binarization circuit 45, and detects a rising zero-cross timing of the tracking error signal 500 to generate a pulse as shown in FIG. This is called a track crossing pulse). The example in FIG. 4 shows that B4 is missing from the crossing pulses of B1, B2, B3, B4, and B5. The cycle measurement circuit 46 constantly measures the generation cycle (T1 to T3...) Of the track crossing pulse, and outputs the measured value to the lack determination circuit 47. The missing determination circuit 47 is for determining whether or not the track crossing pulse is missing from the generation cycle of the track crossing pulse (T1 to T3...), And multiplies the immediately preceding measurement value by K times (in this example, K = If no pulse is input after the elapse of 1.5), it is determined that the pulse is missing. If the pulse is recognized as missing, a pseudo pulse 502 for correction is generated. In the example of FIG. 4, the generation cycle T3 of the track crossing pulse
Of the generation cycle T2 of the crossing pulse measured last time.
Since it is larger than five times, a pseudo pulse C1 (502) for correction is generated as shown in FIG. OR circuit 4
Reference numeral 8 denotes a track crossing signal 501 and a pseudo pulse 5 for correction.
02, and outputs a corrected track crossing signal 503 shown in FIG. As a result, five track traversing pulses D1 to D5 are output on the correction track traversing signal 503, so that the missing B4 can be corrected.

As described above, in the conventional example, the light spot passes through the mirror portion, and the tracking error signal 500 becomes as shown in FIG. 4A. Because you can replenish the minutes,
Spot positioning accuracy at the time of access can be increased.

[0009] Incidentally, those related to this type of apparatus include, for example, Japanese Patent Application Laid-Open Nos. 2-137129 and 2-137.
58736 and the like.

[0010]

However, the above-mentioned prior art has the following problems. This will be described with reference to FIG. FIG. 5 shows, for example, a case where the light spot passes through the pre-format section 17. In FIG. 5, (A) shows a tracking error signal 500, and the light spot passes through the pre-format section. Unlike the case of FIG. 4, the signal is disturbed as shown in FIG. FIG. 5B shows a track crossing signal 501 generated based on this waveform, and B1, B2, and B3.
In addition to the above track crossing pulse, an extra pulse BN is generated due to the influence of the preformat portion. Therefore, the track crossing pulse generation cycle measured by the cycle measurement circuit 46 is T
1 to T3. FIG. 5C shows the lack determination circuit 47.
Since T3 is larger than 1.5 times T2, a pseudo pulse C1 for correction is generated. FIG. 5D shows a corrected track crossing signal 50 which is a logical sum of the track crossing signal 501 and the pseudo pulse signal 502 for correction.
3, in addition to the normal crossing pulses D1 to D3, extra pulses DN1 and DN2 are also output.

As described above, in the above-mentioned conventional example, when an extra pulse (BN in FIG. 5) is generated in the track crossing signal 501 due to the influence of the light spot passing through the pre-format section 17, this pulse is directly used as the correction track. Crossing signal 5
03 (DN1 in FIG. 5) and an extra correction pulse (DN2 in FIG. 5).
As a result, the positioning accuracy of the light spot at the time of access deteriorates.

Accordingly, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
It is an object of the present invention to provide an optical disk device that employs a track search method that can achieve extremely good positioning accuracy of a light spot during random access.

[0013]

In order to achieve the above object, an optical disk apparatus according to the present invention measures a binarizing circuit for detecting a track crossing signal from a tracking error signal and measures a generation cycle of a track crossing pulse. A period measurement circuit, and a plurality of window signal generation circuits for generating window signals having different window widths based on the generation intervals of the track crossing pulses measured by the period measurement circuit, wherein each of the plurality of window signal generation circuits outputs Generates a measurement timing signal for controlling the period measurement circuit based on the track crossing pulse detected during the window signal period and its presence / absence and controls the period measurement circuit, and also determines whether the track crossing signal is missing. Is determined, and a pseudo pulse for missing correction is generated in the case of missing.

[0014]

FIG. 6 shows a case where, for example, a light spot passes through the pre-format section 17, and FIG.
Is a tracking error signal 500, and the signal is disturbed as shown in the figure from t0 to t1 where the light spot passes through the pre-format portion. FIG. 6B shows the case where the tracking error signal 500 shown in FIG.
B1 to B2 are track crossing signals generated by binarization.
In addition to the track crossing pulse of No. 4, extra pulses of BN1 and BN2 are generated due to the influence of the preformat portion. The cycle of occurrence of B1 and B2 and the cycle of occurrence of B2 and B3 are measured by the cycle measuring circuit 1, and T1 and T2, respectively.
It is. tc is [(T1 + T1) when B3 is input.
2) / 2] is the estimated occurrence time of B4 calculated by the calculation of [2] / 2]. (WA) is a window signal generated by the first window signal generation circuit, and is set to include tc. (WB) is a window signal generated by the second window signal generation circuit, and is set relatively wide so as to include the window signal (WA) generated by the first window signal generation circuit. (P) is a signal for period measurement used in the period measurement circuit. In this case, among the output pulses of the binarization circuit, the first pulse is generated within the window signal period generated by the first window signal generation circuit. Is used to obtain a measured value T3.
FIG. 6C shows a corrected track crossing signal 503 used for counting the number of track crossings and detecting the speed. In this case, the pulse BN2 first generated during the window signal period generated by the second window signal generation circuit. Is used.

By the above control, for example, even if the light spot passes through the pre-format portion and the tracking error signal is disturbed and an extra pulse is generated in the track crossing signal, the influence of the extra pulse generated in the track crossing signal. This makes it possible to measure the traversing period without being affected by the traverse. For example, in the example of FIG. 6, the influence of the noise pulses of BN1 and BN2 generated in FIG. 6B can be avoided, and the pulse generation period T3 of B3 and B4 can be recognized as the crossing period. The corrected track crossing signal 503 of FIG. 6C used for counting the number of track crossings and detecting the speed has an irregular pulse generation cycle due to the influence of a noise pulse. High-precision access control becomes possible.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The optical disk device according to the present embodiment is the same as the conventional example shown in FIG. 2 except for the track crossing correction circuit. Here, only the track crossing correction circuit will be described.

FIG. 1 is a block diagram showing the configuration of the track crossing correction circuit 50. In the figure, a track crossing correction circuit generally indicated by reference numeral 50 includes gate circuits 3 and 4, window (signal) generation circuits 5 and 6 for generating window signals having different window periods, and a track crossing period. , A computing unit 2 for obtaining an average value of the measured two past track crossing periods, a measurement timing for generating a measurement timing signal to the period measurement circuit 1 and the window generation circuits 5 and 6. A signal generation circuit for generating a correction signal for generating a correction pseudo pulse when a track crossing pulse is missing from an output signal of a window circuit for generating a window signal having a long window period and an output signal of a gate circuit; It comprises a circuit 8 and a gate circuit 9.

Next, the operation of each component of the track crossing correction circuit 50 will be described. The arithmetic unit 2 calculates an average value of the past two track crossing periods measured by the period measuring circuit 1 and outputs the average value to the window generating circuits 5 and 6. The window generating circuits 5 and 6 use the average value of the past two track crossing cycles as an estimated value of the next track crossing cycle,
An estimated generation time tc of the next track crossing pulse is obtained.
Window generating circuit 5 generates window signal A so as to include estimated generation time tc, and window generating circuit 6 generates a relatively wide window signal B so as to include the window signal generated by window generating circuit 5. The gate circuits 3 and 4 output only one pulse generated first during each window period of the window signals A and B among the pulses generated in the track crossing signal 501. Further, when no pulse is generated in the track crossing signal 501 during the window period of the window signal A, the gate circuit 3 generates a pulse at the end of the window period of the window signal A. The correction signal generating circuit 8 outputs the gate circuit 4 before the end point of the window period of the window signal B.
When no pulse is output from the controller, it is determined that a track crossing pulse is missing, and a correction pseudo pulse is output. The gate circuit 9 performs a logical OR operation on the output of the gate circuit 4 and the output of the correction signal generation circuit 8 to generate the correction track crossing signal 5.
03 is output. Measurement timing signal generation circuit 7
Outputs a measurement timing signal A555 and a measurement timing signal B556, which are timing signals for period measurement, to the period measurement circuit 1 respectively. Measurement timing signal A55
5 is a logical sum of the output of the gate circuit 3 and the output of the gate circuit 4. If a pulse is generated in the measurement timing signal A555 before the end of the window period of the window signal A, the measurement timing signal B556 generates a pulse at the timing at the end of the window period of the window signal A. If no pulse is generated in the measurement timing signal A555 before the end of the window period of the signal A, a pulse is generated at the timing at the end of the window period of the window signal B. In the cycle measurement circuit 1, the measurement timing signal A555
The pulse generated immediately before the pulse of the measurement timing signal B556 among the generated pulses is determined to be a pulse for period measurement.

FIG. 7 shows an operation waveform of the circuit when, for example, a light spot passes through the pre-format section 17. The operation of the track crossing correction circuit 50 will be more specifically described with reference to this time chart. explain. FIG. 7A shows a tracking error signal 500, in which a disturbance as shown occurs at a portion between t2 and t3 when the light spot passes through the pre-format portion. FIG. 7B shows a track crossing signal 5 obtained by binarizing the tracking error signal 500.
01, BN1, BN due to the effect of the pre-format part.
Two extra pulses have occurred. (B ′) of FIG.
FIG. 5B is an enlarged view of a portion after t1 in FIG. (C) of FIG. 7 shows the estimated occurrence time tc of B4, and is from t3 to tc.
Time until the output of arithmetic unit 2 [(T1 + T2) / 2]
Given by FIG. 7D shows a window signal A551 of the window generating circuit 5, which sets a window period so as to include tc. FIG. 7E shows a window signal B552 of the window generating circuit 6, which sets a relatively wide window period so as to include the window signal A551. FIG. 7F shows the output signal 553 of the gate circuit 3.
And the first pulse B4 generated during the window period of the window signal A is output. FIG. 7G shows an output signal 554 of the gate circuit 4, in which the first pulse BN2 generated during the window period of the window signal B is output. FIG. 7H shows a measurement timing signal A555, which is a logical sum of the above (F) and (G). FIG. 7I shows the measurement timing signal B556, which is the end time t of the window period of the window signal A as described above.
Since a pulse is generated in the measurement timing signal A555 before r (BN2, B4), a measurement timing pulse is generated at tr. As a result, as described above, in the cycle measurement circuit 1, of the two pulses generated in the measurement timing signal A555, the pulse B4 immediately before the pulse generated in the measurement timing signal B556 is determined to be a pulse for cycle measurement. Then, T3 shown in FIG. 7 is determined as the track crossing cycle. The measurement timing signal B556 is also output to the window generating circuit 6, and the window pulse B552 in (E) should originally be generated as a dotted line. Since it is reset to the L level as indicated by the solid line, a plurality of pulses are not detected by one window signal. FIG. 7J shows a signal 557 output from the correction signal generating circuit 8. As described above, before the end of the window period of the window signal B552, the pulse BN2 is output to the output 554 of the gate circuit 4 shown in FIG. No pseudo pulse for correction is output because it has occurred. FIG. 7 (K) shows a corrected track crossing signal 503 for counting the number of track crossings and detecting the moving speed of the optical head. Is output.

By the above processing, the track crossing signal 50
It can be seen that it is possible to measure the generation period T3 of the track crossing pulse without being affected by the extra pulses BN1 and BN2 generated in No. 1. The above is the description of the operation when measuring T3 on the basis of the generation periods T1 and T2 of the track crossing pulse.
From T3, the generation cycle of the next track crossing pulse can be measured by repeating the same operation. On the other hand, in the corrected track crossing signal 503, the generation position of the track crossing pulse is deviated by the influence of the extra pulse BN2. However, since the track crossing pulse generation interval T3 is correctly measured, the number of track crossing pulse generations is reduced. Don't go crazy.

In the above description, the operation of the cycle measuring circuit 1 will be described in more detail with reference to FIGS.
Reference numerals 11 and 12 denote counter circuits.
The value is counted up by the clock pulse in which 0 occurs. The counter circuit 11 outputs the measurement timing signal A
555 is cleared by the pulse generated in the counter circuit 1
Reference numeral 2 denotes a pulse generated in the measurement timing signal A556, which latches the output value 651 of the counter circuit 11. 13,1
Reference numerals 4 and 15 denote latch circuits. The latch circuit 13 latches an input signal with a pulse generated in the measurement timing signal A555.
The input signal is latched by the pulse generated in 6. The outputs of the respective counter circuits and latch circuits are constituted by, for example, a 12-bit digital data bus in this embodiment. Note that (B ′), (H), and (I) in FIG. 9 are the same as the signals of the same symbols shown in FIG.
(B ') is a track crossing signal 501, (H) is a measurement timing signal A555, and (I) is a measurement timing signal B5.
56. (M) is an output value 651 of the counter circuit 11
And is cleared by the pulse of the measurement timing signal A555 shown in (H). (N) shows the output value 652 of the counter circuit 12, and the pulse of the measurement timing signal B556 shown in (I) is
The output value TH of 1 is latched. As a result, the output value 652 of the counter 12 of (N) becomes the pulse B as shown by the dotted line.
This is equivalent to the measurement from the position of No. 4, and the period measurement until the next track crossing pulse can be accurately performed. (O) is an output value 653 of the latch circuit 13;
With the pulse of the measurement timing signal A555 shown in (H),
From the output value 652 of the counter 12 shown in (N), T3A,
Latch T3B. (P) is the output value 654 of the latch circuit 14, and the measurement timing signal B55 shown in (I).
With the pulse of 6, the output value 6 of the latch circuit 13 shown in FIG.
Latch T3B from 53. As described above, from the output signal 654 of the latch circuit 14 shown in (P), B3 and B4
Is output as the measured value T3B of the occurrence interval. Further, from the output signal 655 of the latch circuit 15, an occurrence interval T2 between B2 and B3, which is one previous measurement value, is output.

Next, FIG. 10 shows a case where a tracking error signal different from that of FIG. 7 is generated. FIG.
(A) to (K) of 0 are signals having the same meaning as the signals indicated by the same symbols in FIG. FIG. 10 shows operation waveforms of the respective sections when, for example, a light spot passes through the mirror section 18. The operation of the track crossing correction circuit will be described in detail with reference to this time chart.
(A) is a tracking error signal 500, and a disturbance as shown in the figure occurs at a portion between t2 and t3 where the light spot passes through the mirror portion. (B) is a tracking error signal 500.
Is a binarized track crossing signal 501, and the position of the pulse of B4 has moved to B4 ′ due to the influence of the mirror unit.
(B ') is an enlarged view of a portion after (t1) of (B).
(C) is the estimated occurrence time tc of B4, which is tc from B3.
The time up to is given by the output [(T1 + T2) / 2] of the arithmetic unit 2. (D) is a window signal A551,
The window period is set to include tc. (E) is a window signal B552, which sets a relatively wide window period so as to include the window signal A. (F)
Is the output signal 553 of the gate circuit 3. As described above, since no pulse is generated in the track crossing signal during the window period of the window signal A, the pulse signal Fwa is generated at the end of the window period of the window signal A. Is output. (G) is an output signal 554 of the gate circuit 4, and the first pulse B4 'generated during the window period of the window signal B is output. (H) is a measurement timing signal A555, which is the logical sum of (F) and (G). (I) is a measurement timing signal B556. As described above, no pulse is generated in the measurement timing signal A555 before the end of the window period of the window signal A. Generates a measurement timing pulse. As a result, as described above, in the cycle measurement circuit 1, of the two pulses generated in the measurement timing signal A555, B4 ′ which is immediately before the pulse generated in the measurement timing signal B556 is defined as a pulse for cycle measurement. It is determined that T3 shown in FIG. 10 is the track crossing period. (J) is a signal 557 output from the correction signal generation circuit 8, and since the pulse B4 'is generated at the output 554 of the gate circuit 4 shown in (G) before the end point of the window period of the window signal B, No pseudo pulse for correction is output. (K) is a corrected track crossing signal 503 for counting the number of track crossings and detecting the moving speed of the optical head. The logical OR operation of (G) and (J) is performed and a pulse B4 'is output. .

As described above, the tracking error signal 500 is disturbed by the influence of the light spot passing through the mirror section,
Even when the position of the track crossing pulse generated in the track crossing signal 501 is out of order, the crossing pulse can be detected, and the counting error of the track crossing number does not occur.

Next, referring to FIG. 11, a case where a tracking error signal different from the cases of FIGS. 7 and 10 is shown. (A) to (K) are signals having the same meaning as the signals indicated by the same symbols in FIGS. FIG. 11 shows operation waveforms of the respective sections when, for example, a light spot passes through the mirror section 18. The operation of the track crossing correction circuit will be described in detail with reference to this time chart.
(A) is a tracking error signal 500, and a disturbance as shown in the figure occurs at a portion between t2 and t3 where the light spot passes through the mirror portion. (B) is a tracking error signal 500.
Is a binarized track crossing signal 501, and the pulse of B4 is missing due to the influence of the mirror unit. (B ') is an enlarged view of a portion after (t1) of (B). (C) is B4
Is the estimated occurrence time tc, and the time from B3 to tc is given by the output [(T1 + T2) / 2] of the arithmetic unit 2.
(D) is a window signal A551, and the window period is set so as to include tc. (E) is a window signal B552, which sets a relatively wide window period so as to include the window signal A. (F) is an output signal 553 of the gate circuit 3. As described above, since no pulse is generated in the track crossing signal during the window period of the window signal A, the pulse is generated at the end of the window period of the window signal A. The signal Fwa is output.
(G) is an output signal 554 of the gate circuit 4, and since no pulse is generated in the track crossing signal during the window period of the window signal B, no pulse is output.
(H) is a measurement timing signal A555, which is the logical sum of (F) and (G). (I) is a measurement timing signal B556. As described above, since no pulse is generated in the measurement timing signal A555 shown in (H) before the end of the window period of the window signal A, the window A measurement timing pulse is generated at the end of the period. As a result, as described above, the cycle measurement circuit 1 determines Fwa as a pulse for cycle measurement, and determines T3 shown in FIG. 11 as a track crossing cycle.
(J) is a signal 557 output from the correction signal generation circuit 8, and since no pulse is generated at the output 554 of the gate circuit 4 shown in (G) before the end of the window period of the window signal B, the signal 557 is used for correction. Is output. (K) is a corrected track crossing signal 503 for counting the number of track crossings and detecting the moving speed of the optical head. The logical sum of (G) and (J) is performed, and a pseudo pulse Jp for correction is output. Is done.

As described above, the tracking error signal 500 is disturbed by the influence of the light spot passing through the mirror section,
When a track crossing pulse generated in the track crossing signal 501 is lost, a false pulse for correction is generated to compensate for the loss, so that a count error in the number of track crossings does not occur. In addition, since the position where the missing track crossing pulse should occur should be estimated, and the period of the track crossing pulse is measured assuming that the track crossing pulse has occurred near the estimated position, the period that is not easily affected by the lack of the track crossing pulse is measured. Measurement becomes possible.

The components of FIG. 1 in the embodiment described above can be realized by the configuration shown in FIG. 8, for example, for the period measurement circuit 1, but other components are also shown in FIGS. An example of the configuration is shown. FIG. 12 is a block diagram of the arithmetic unit 2 and the window (signal) generating circuits 5 and 6. The arithmetic unit 2 inputs the past two track traversing cycles from the cycle measuring circuit 1 via a 12-bit digital data bus, and outputs the average value of the two track traversing cycles via the adder 60 and the shift circuit 61. calculate. The average value (for example, indicating tc in FIGS. 7, 10, and 11) is input to the window generating circuit 5, and multiplied by constants 0.9 and 1.1 in coefficient units 62 and 63, respectively. Is loaded into the down counters 66 and 67 by a pulse generated in the measurement timing signal B556. The latch circuit 7 is activated by the borrow signal BO of the down counters 66 and 67.
2 to generate a window signal A551 having a width of 0.9 to 1.1 times tc. The OR gate 70 is for resetting the window signal by the pulse of the measurement timing signal B556. The window generating circuit 6 performs the same operation as that of the window generating circuit 5 except that the coefficient values of the coefficient units 64 and 65 are different. 68 and 69 are down counters, 71 is an OR gate,
43 is a latch circuit.

FIG. 13 is a block diagram of the gate circuit 4. Numeral 74 denotes a latch circuit for generating a gate signal for controlling the AND gate 76, and a window signal B552 is output from the AND gate 76 by controlling the gate signal.
Only the first pulse generated in the track crossing signal 501 during the window period (H level period) is output. In addition, 75 is an inverter.

FIG. 14 is a block diagram of the gate circuit 3, and the gate circuit 79 is equivalent to the gate circuit 4 shown in FIG. An edge detection circuit 77 detects a falling edge of the window signal A551 and generates a pulse. The edge detection circuit 77 includes a delay circuit 85 and an AND gate 86. A gate signal generation circuit 78 includes a latch circuit 87 and an inverter 88. The gate signal generated by the gate signal is input to an AND gate 80, and a pulse generated by the edge detection circuit 77 is output from the AND gate 80. Control. An OR gate 81 combines the output pulse of the gate circuit 79 and the output pulse of the AND gate 80.

FIG. 15 is a block diagram of the correction signal generating circuit 8. Reference numeral 83 denotes an edge detection circuit for detecting a falling edge of the window signal B552 and generating a pulse, and includes a delay circuit 94 and an AND gate 95. Reference numeral 82 denotes a gate signal generation circuit including a latch circuit 92 and an inverter 93. The gate signal generated by the gate signal is input to an AND gate 84, and the edge detection circuit 8
3 to control whether or not to output the pulse generated as a pseudo pulse for missing correction.

FIG. 16 is a block diagram of the measurement timing generation circuit 7. Reference numeral 132 denotes an edge detection circuit for detecting a falling edge of the window signal A551 and generating a pulse, and includes a delay circuit 98 and an AND gate 99. An edge detection circuit 133 detects a falling edge of the window signal B552 and generates a pulse. The edge detection circuit 133 includes a delay circuit 100 and an AND gate 101. Reference numeral 138 denotes an OR gate for synthesizing pulses generated in the output signals of the gate circuits 3 and 4.
The gate signal generation circuit 131 includes an inverter 96 and a latch circuit 97. When a pulse is generated from the OR gate 138 during the window period (H level period) of the window signal B552, the latch circuit 97 is cleared. The output of the gate signal generation circuit 131 is the AND gate 13
4, 135, and controls whether or not to output a pulse generated by the edge detection circuit 132 as the measurement timing signal A555 and the measurement timing signal B556. OR
Gate 136 is OR gate 138 and AND gate 13
4 is generated and the OR gate 137 outputs
The pulses generated by the D gate 135 and the edge detection circuit 133 are synthesized.

Although not shown, it is obvious to those skilled in the art that the function of the gate circuit 9 can be realized by an OR gate. .

Although this embodiment has shown an example in which two types of window signal generation circuits are provided, three or more types of window signal generation circuits can be provided, and the number of window signal generation circuits can be increased. The more accurate the control becomes. The circuit configuration in that case can be easily inferred from the present embodiment.

The track traversing correction circuit 50 includes a high-speed CPU and a DSP (Digital Signal) in addition to the above-described configuration.
A similar algorithm can be implemented programmatically using the processer).

[0034]

Since the present invention is constructed as described above, the tracking error signal is disturbed by the influence of the light spot passing through the pre-format portion and the mirror portion of the optical disk, and an extra signal is added to the track crossing signal. When a pulse is generated or a track crossing pulse is missing, the following effects are obtained.

(1) When an extra pulse is generated in the track crossing signal, a window signal is generated based on the measured track crossing cycle, and a noise pulse generated in the track crossing signal by the window signal is removed.

(2) When a crossing pulse is lost, a window signal is generated based on the measured track crossing period,
The missing of the crossing pulse is recognized by the window signal, and a pseudo pulse for correction is generated.

(3) Two types of window signals are generated based on the track traversing period, and unnecessary pulses in the wide window signal can be removed by the narrow window signal. Therefore, even when an extra pulse is generated in the track crossing signal, the generation interval of the crossing pulse can be measured without being affected by the extra pulse, so that the stable correction operations (1) and (2) can be realized.

From the above (1) to (3), it is possible to accurately detect the number of track traversals of the light spot and to shorten the track search time. In particular, when the optical head is moved at a high speed, the frequency of the generated tracking error signal increases, and the difference from the frequency of the preformat data decreases. In this case, even when the tracking error signal is processed by the low-pass filter, an extra pulse is generated in the track crossing signal due to the influence of the preformat unit. The present invention is particularly effective when realizing such high-speed access.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional optical disc device.

FIG. 3 is an explanatory diagram showing a preformat unit and a mirror unit on an optical disc.

FIG. 4 is a timing chart for explaining the operation of the conventional example.

FIG. 5 is a timing chart for explaining a problem of the conventional example.

FIG. 6 is a timing chart for explaining an outline of the operation of the present invention.

FIG. 7 is a timing chart for explaining the operation of the embodiment of the present invention.

FIG. 8 is a block diagram showing a specific example of a cycle measuring circuit according to an embodiment of the present invention.

9 is a timing chart for explaining the operation of the cycle measuring circuit of FIG. 8;

FIG. 10 is a timing chart for explaining the operation of the embodiment of the present invention.

FIG. 11 is a timing chart for explaining the operation of the embodiment of the present invention.

FIG. 12 is a block diagram showing a specific example of an arithmetic unit and a window signal generation circuit according to an embodiment of the present invention.

FIG. 13 is a block diagram showing a specific example of a gate circuit according to an embodiment of the present invention.

FIG. 14 is a block diagram showing a specific example of another gate circuit according to an embodiment of the present invention.

FIG. 15 is a block diagram showing a specific example of a correction signal generation circuit according to an embodiment of the present invention.

FIG. 16 is a block diagram showing a specific example of a measurement timing signal generation circuit according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Period measuring circuit 2 Computing unit 3 Gate circuit 4 Gate circuit 5 Window generating circuit 6 Window generating circuit 7 Measurement timing signal generating circuit 8 Correction signal generating circuit 9 Gate circuit 21 Optical disk 22 Semiconductor laser element 26 Objective lens 29 Photodetector Reference Signs List 30 optical head 31 tracking actuator 32 linear motor 40 differential amplifier circuit 41 tracking control circuit 42 linear motor control circuit 43 target speed detection circuit 44 target speed generation circuit 50 track crossing correction circuit 501 tracking error signal 502 track crossing signal 503 Correction track crossing signal

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoyuki Suzuki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi, Ltd. Visual Media Research Laboratory (56) References JP-A-60-259992 (JP, A) Kaihei 1-2223675 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/085 G11B 21/08 G11B 21/10

Claims (1)

(57) [Claims] 1. An optical disk having a track for recording or reproducing information, an optical head for condensing a light spot on the optical disk, and an optical head for focusing the light spot on the track. An optical disc apparatus, comprising: a tracking control unit for finely adjusting a position; and a random access control unit for moving and positioning the light spot by moving the optical head based on a track crossing signal detected from the tracking signal. A track crossing signal detecting means for detecting a track crossing signal indicating that the light spot has crossed the track from a signal; and a window for generating a window signal for removing a noise component of an output signal of the track crossing signal detecting means. Signal generating means; the window signal; A noise gate circuit that receives a rack traversing signal, removes a noise component of the track traversing signal, and outputs the signal; a track traversing period measuring unit that measures a track traversing period from an output signal of the noise gate circuit; Information indicating that the track traversed is detected from the output signal of the track traversing signal detecting means based on the track traversing cycle,
Pseudo-track traversing signal generating means for generating pseudo-track traversing information; an output signal of the pseudo-track traversing signal generating means and an output signal of the noise gate circuit; A gate circuit for synthesizing the pseudo track traversing information and outputting a corrected track traversing signal , wherein a plurality of the window signal generating means are provided;
The window signal generating means is a window having a different length (width).
Dow signals are generated so as to overlap with each other in time, and a plurality of noise gate circuits are provided.
The is gate circuit has a different length from the track crossing signal.
And one of the window signals of
Priority is set for the output signal of each noise gate circuit
The noise that has detected the track crossing information.
Of the outputs of the gate circuit has the highest priority.
Selected, tiger using this selected track crossing information
An optical disc device characterized by measuring a clock traversing cycle .