JPH087952B2 - Disk-shaped recording medium rotation control device - Google Patents

Description

The present invention relates to a rotation control device for recording on a disk-shaped recording medium at a constant linear velocity.

(B) Conventional technology When an information signal is recorded on a disc-shaped recording medium,
There are a case where the rotation of the disk is controlled at a constant linear velocity (CLV control) and a case where it is controlled at a constant angular velocity (CAV control).

When recorded at a constant linear velocity, the recording density can be increased. Therefore, CD (Compact Disc) is CLV controlled. Recording at a constant angular velocity is suitable for a document file because the control of disk rotation is simple and the amount of information per track is constant.

When performing CLV control, it is necessary to detect the position of the recording head (pickup means) on the disk and change the disk rotation speed according to this position.

A method for detecting the position of the pickup means is disclosed in JP-A-55-150.
As disclosed in Japanese Patent No. 165, there is a device which detects a pickup position by creating a pulse based on the movement of the pickup and counting the pulse. This method has the disadvantages of low accuracy, being easily affected by eccentricity, and having a large number of parts near the pickup.

In other words, magneto-optical recording (Radio Science February 1985 PP.99-1
03)) and write-once discs (see Sanyo Technical Review Vo1.16.NO1.1984, PP.4-10) have a track pitch of about 2 μm, so position detection requires considerable accuracy. . If the disk is eccentric, for example, there is an eccentricity of about 100 tracks,
If the tracking control is performed, the position of the pickup may change during the rotation of the disk, and the disk rotation speed may change during one rotation. That is, the linear velocity at the time of recording does not become constant but changes, which makes reproduction difficult. Arranging an encoder or the like in association with the pickup complicates the configuration and hinders size reduction.

(C) Problems to be Solved by the Invention As described above, the conventional position detecting method has poor accuracy and is easily affected by the eccentricity of the disk. Further, a mechanical encoder or the like has to be arranged in the vicinity of the pickup, which hinders downsizing of the device.

(D) Means for Solving the Problems In the present invention, the position detecting means of the pickup means detects the initial position of the pickup and means for detecting one rotation of the disk-shaped recording medium and counting one rotation detection pulse. It has and. Then, the rotation of the disc-shaped recording medium is controlled based on the output of the position detecting means.

(E) Action Since the disk-shaped recording medium has spiral tracks, if the pickup means traces the track by the tracking control means, the pickup is performed every time the disk-shaped recording medium makes one revolution. Is 1
It will be moved by the track. Therefore, the position of the pickup means can be detected by counting one rotation detection pulse.

(F) Embodiments Embodiments of the present invention will be described below with reference to the drawings. 3 and 9 are a plan view and a perspective view showing the disc-shaped recording medium (1). In the figure, (2) is a center hole of a disk-shaped recording medium (hereinafter referred to as a disk) (1), (3) is a magneto-optical recording portion used for magneto-optical recording, and (4) is information in the form of concave and convex pits. Is recorded on the optical recording portion, and (5) is a detection mark for detecting one rotation of the disc (1).

Recording / reproducing on / from the disc (1) is performed from the inner circumference to the outer circumference. Since the optical recording portion (4) is located on the inner circumference side of the disc, it corresponds to the lead-in portion of the magneto-optical recording portion (3). Further, the detection mark (5) is provided further on the inner peripheral side.

The disk (1) is formed by forming a perpendicular magnetic film (7) (hatched) of GdTbFe or TbFeCo which is an amorphous alloy of a rare earth metal and a transition metal on a substrate (6) made of polycarbonate or acrylic, and further by a dielectric material. The protective layer (8) is formed (see FIG. 9).

A spiral guide groove (6a) is formed on the substrate (6), and this portion serves as a recording track. Also, in the optical recording part (4), like the compact disc,
Information (conditions regarding recording and reproduction) is formed in advance in the form of uneven pits. In addition to recording in the form of uneven pits, it is also possible to record by removing the perpendicular magnetization film (7) as in a write-once disc.

With the above recording method, the already recorded information signal can be read by the change in the amount of reflected light from the disc (1). The method of recording in the form of uneven pits is advantageous because it is possible to form pits when forming the guide groove (6a) and there is no risk of erasing. still,
Laser light is emitted from the side of the plastic substrate (6) as shown by arrow A.

As a format for recording information on recording / reproducing conditions, in a device that can also use a compact disc, the subcode Q channel format of the compact disc is used. The format of the subcode Q channel is shown in FIG. Of these, in the 4 bits of the address, (0001), (0010), (00
11) is an important pattern for compact discs, but other patterns are meaningless for compact discs.

Therefore, in the optical recording portion (4) of the magneto-optical disk (1), for example, a pattern (1000) is recorded in the address portion of the subcode Q channel format.

In the 72-bit data portion, information on recording (including erasing) and reproducing conditions of the magneto-optical disk is recorded. This information relates to the laser power, the linear velocity, the strength and direction of the bias magnetic field at the time of recording, erasing, and reproducing, for example. It is also possible to record a specific pattern to indicate the beginning of the magneto-optical recording portion (3) (or the end of the recorded portion (4)). That is, the specific pattern is used as a mark indicating the reference position, and the rotation speed and time data (time code) up to the start portion of the magneto-optical recording portion is recorded.

The conditions for recording and reproducing are necessary for the following reasons. That is, as the material of the perpendicular magnetization film of the magneto-optical disk, there are GdFe, TbFe, TbFeCo, etc. as described above, but if the composition is different, the conditions of the laser power and the bias magnetic field will naturally be different. This is because the Curie point also rises as the proportion of Co increases even with the above materials, and it is necessary to increase the laser power for recording and erasing.

Therefore, if the laser power at the time of recording, erasing and reproducing, the strength of the bias magnetic field at the time of recording and erasing, or the required linear velocity is written in the already recorded portion (4), the Compatible with different magneto-optical disks.

In addition, even if the recording materials are the same, the magnetization direction of the magneto-optical recording portion in the non-recorded state may be different depending on the standard. Therefore, information that specifies the direction of the bias magnetic field during recording and erasing is recorded. What is done is effective.

The detection mark (5) may be formed, for example, by forming the perpendicular magnetization film (7) into a predetermined shape when a disc is formed, and forming a part of the innermost peripheral part having a different reflectance.

FIG. 2 is a diagram showing an optical system for recording / reproducing and a circuit block for deriving a signal. Semiconductor laser (10)
The light from is radiated to the disc (1) through the collimator lens (11), the beam splitter (12) and the objective lens (13). The reflected light from the disc (1) passes through the objective lens (13) and the beam splitter (12), and also passes through the half-wave plate (14) and the lenses (15) and (16) to obtain a polarization beam splitter (17). ), It is divided into two components. One of the split reflected lights is given to the first photodetector (18), and the other is given to the second photodetector (20) via the cylindrical lens (19).

The first photodetector (18) is divided into two, and a tracking error signal is obtained from the terminal (4) by taking the difference between both outputs.

The second photodetector (20) is divided into four, and the difference between the diagonal components is taken to obtain the focus error signal at the terminal (2
2) Derived. Also, by taking the sum of the diagonal components,
From the terminal (23), a total reflected light amount instruction signal proportional to the total reflected light amount from the disc (1) is obtained.

When the magneto-optical disk is reproduced, the difference between the outputs of the first and second photodetectors (18) and (20) (generated at the terminal (24))
Is used. When reproducing a compact disc, the sum of the outputs of the first and second photodetectors (18) and (20) (generated at the terminal (25)) is used.

The focus error signal, the total reflected light amount instruction signal, and the tracking error signal are also used during recording.

FIG. 1 is a block diagram showing the configuration of an apparatus for controlling the rotation of a disk.

In the figure, (35) is the input terminal for the total reflected light amount instruction signal, (36) is the input terminal for the tracking error signal, and (3
7) is an input terminal for one rotation detection signal. (38) is the first
An amplifier, (39) is a first comparator, (40) is a first level shift circuit, and (41) is a first inverter. or,
(42) is the second amplifier, (43) is the second comparator, (4
4) is a second level shift circuit, and (45) is a second inverter.

(46) is the first mono-multi that is triggered by the rising of the output of the second inverter (45), and (47) is the second mono-multi that is triggered by the falling of the output of the second inverter (45). (Four
8) is the output of the first inverter (41) and the first mono-multi (4)
6) First AND gate with output as input, (49) second AND gate with first inverter (41) output and second monomulti (47) output, (50) first AND gate (48) output And from terminal (51) The first NAND gate that inputs (described later), (52) is the same And a second NAND gate (49) that receives the output of the second NAND gate.

The one rotation detection signal triggers the third monomulti (53) and is further connected to the data input of the D-type flip-flop (54). The output of the third monomulti (53) is supplied to the clock input of the D-type flip-flop (54). (55)
Is a fourth monomulti (74LS123), the falling trigger input (A) (55a) is connected to the output of the first inverter (41), and the B input (55b) is connected to the power supply voltage. or,
The Q output of the D-type flip-flop (54) is applied to the clear terminal (CLR) (55c). The output of the fourth monomulti (55) is supplied to the clear terminal (CLR) (54c) of the D-type flip-flop (54), and the third AND gate (56) (since the input and output are negative logic, the symbol is Output). The output of the first NAND gate (50) is also applied to the third AND gate (56).

(57) is an up / down counter (15-bit binary counter). Up / down counter (57) is ▲
When a pulse is input to the ▼ terminal (57a), the count value increases, and when a pulse is input to the ▼ terminal (57b), the count value decreases. Further, the counter (57) is cleared by the output of the initial position determining means (58), and the content becomes "0".

(59) is a position-to-frequency conversion means, and a counter (5
Output the frequency signal in response to the digital output of 7). (60) is a spindle motor for rotating the disk, (62) is an FG signal detecting means, and (61) compares the FG signal with the output frequency signal of the position-frequency converting means (59) and the spindle motor (60 ) Is a rotation control means for controlling the rotation speed.

The one-rotation detection signal is created as shown in FIG. That is, a sensor (67) having a light emitting portion (65) and a light receiving portion (66) at a portion corresponding to the detection mark (5) of the disc (1).
Is arranged, the change of the reflected light is detected, it is amplified by the amplifier (68), and the waveform is shaped by the waveform shaping circuit (69).

The above This signal is output when the pickup means is out of the tracking state, and becomes active when it is at a low level. The state where the tracking is off is, for example, when the pickup means is abnormally sent due to vibration,
It occurs during search and access. And this Are created by the transfer device of the pick-up means. The transfer device for the pickup means has the following structure (see FIGS. 8, 12, and 13).

The rotating member (71) is instructed to rotate about the shaft (72), and the pickup (73) is fixed to one end thereof. The rotary member (71) is rotationally driven by the linear motor (74). For example, a magnet as a mover (74a) is fixed to the rotating member (71), and this mover (74a)
A yoke as a stator (74b) and a coil wound around the yoke are provided at predetermined intervals. The linear motor (74) is normally driven based on the tracking error signal applied via the (a) side of the switch (76). The tracking error signal is generated by the pickup (73). When the tracking error signal is within a predetermined value, the tracking control is performed by driving the objective lens (73a) of the pickup (73), and the tracking error signal exceeds the predetermined value. At this time, the linear motor (74) is driven, the entire pickup (73) moves, and tracking control is performed.

Now, the position of the pickup (73) is detected by the position detecting means (75). This means (75) is composed of a light emitting diode (75a) fixed to the rotating member (1) and a photo sensor (75b) arranged on the locus of this light emitting diode (75a) as shown in FIG. You can In FIG. 13, it is assumed that point C receives light from the light emitting diode (75a) and an electromotive force is generated. A resistor is formed between the terminal A and the point C and between the terminal B and the point C, and currents (I ₁ , I ₂ ) corresponding to the resistors flow. Therefore, for example, P = (I ₁ −I
₂ ) / (I ₁ + I ₂ ) can be the position signal.

This position signal (P) becomes one input of the comparison means (77). The other input of the comparison means (77) is the output of the counter (78).
D / A converted by the D / A converter (79). The output (V _O ) of the comparison means (77) is applied to a window comparator (80) composed of comparators (80a) (80b).
If (V _O ) is within the comparator level of the window comparator (80) (V _HA ＞ V _O ＞ V _LA ), the comparator (80a) (8a)
Both outputs of 0b) are at L level, and gates (81a) (81
b) are closed together. Therefore, the value of the counter (78) does not change. Now, when the pickup (73) moves,
The output (P) of the position detection means (75) changes, and the output (V _O ) of the comparison means (77) becomes (V _O > V _HA ) or (V _O <V _LA ).
When the oscillation output of the comparator (80a) or the output of (80b) becomes the H-level gate (81a) or gate (81b) opens oscillator (82) is applied to the counter (78), (V _HA The value of the counter (78) changes until> V _O > V _LA ). That is, the counter (78) is the pickup (73)
And the oscillator (82) as a writing means.

The output (V _O ) of the comparison means (77) is also applied to another window comparator (83) [comprised of comparators (83a) and (83b)]. The comparator level (V _HB , V _LB ) of this window comparator (83) is (V _HB >
V _HA ), (V _LB <V _LA ). Pickup (7
3) is greatly changed by external disturbance such as vibration, and the output (V _O ) of the comparison means (77) becomes (V _O > V _HB ) or (V _{O
When O} <V _LB , the output of the gate (84) becomes H level, the gates (81a) and (81b) are closed, and the value of the counter (78) is the value just before the pickup (73) changes due to disturbance. And the switch (76) is switched from the (a) side to the (b) side, and the drive of the linear motor (74) is stopped. The output (V _O ) of the comparison means (77) is passed through the (b) side contact of the switch (76) to the linear motor (74).
To the pickup (73) to the position of the pickup immediately before receiving the disturbance stored in the counter (78).

Switch (76) to (b) side
The pickup (73) is moved to the desired position (fast forward) by applying the oscillation output of 2) to the counter (78).
Can be made. In this case, the oscillation frequency of the oscillator (82) defines the moving speed of the pickup (73). Even in this case, if the pickup (73) malfunctions due to disturbance or the like, the movement of the pickup (83) is stopped by closing the gate (81a) or (81b) with the output of the window comparator (83). Can be done.

And This is the inverted output of the OR gate (84) in FIG.

Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIGS. FIG. 4 shows the tracking error signal (C) and the total reflected light amount instruction signal (a) when the pickup moves in the groove (6a) of the disc as shown by the arrow (A). When the signals (c) and (a) are compared with a certain level and converted into a square wave, the signals (b) and (d) are obtained.

Here, it is assumed that FIG. 4 corresponds to the movement of the pickup means from the inner circumference to the outer circumference. At this time, the rising of the square wave (d) corresponding to the tracking error signal exists in the high level period of the square wave (b) corresponding to the total reflected light amount instruction signal. On the other hand, when the pickup means moves from the outer circumference to the inner circumference, the time axis should be oriented in the direction of arrow (B) in FIG. That is, the trailing edge of the square wave (d) corresponding to the tracking error signal exists in the high level period of the square wave (b) corresponding to the total reflected light amount instruction signal. In other words, this makes it possible to distinguish in which direction the pickup means is transferred.

Also, when tracking is in progress, the disc 1
Since one track advances every rotation, the pickup position can be detected by counting one rotation detection pulse.

In the circuit of FIG. 1, the total reflected light amount instruction signal input to the terminal (35) is amplified by the amplifier (38) and compared with a predetermined level by the first comparator (39). Then, it is converted into a TTL level (50) by the level shift circuit (40). The output of the first inverter (41) is always at a low level in the tracking state, and changes as shown in FIG. 4 when the pickup means crosses the guide groove.

On the terminal (37), at the detection mark (5),
A one-rotation detection signal (B) (FIG. 5) which becomes H level is applied. Since the signal (b) applied to the terminal (37) may be mixed with noise such as (b) ″, a signal whose high level continues longer than the metastable period of the third monomulti (53). Only when (b) 'is input, a high-level signal is latched in the D-type flip-flop (54), and the Q output (d) of the D-type flip-flop (54) becomes high-level.

In the fourth monomulti (55) composed of 74LS123, the B input (55b) is at the high level and the A input (55a) is at the low level (since it is in the tracking state, the first inverter (4)
The output of 1) is configured to be triggered when the clear terminal (55c) rises when the output is low level.

Therefore, the Q output (D) of the D-type flip-flop (54)
Goes high, the fourth monomulti (55) is triggered, and as a result, the output (e) goes low. Then, the falling of this output (e) resets the D-type flip-flop (54). That is, the pulse (e) with a short width becomes
It is applied to the 3AND gate (56) (or gate in negative logic), and the count value of the counter (57) increases. The pulse width of the pulse (e) is determined by the transmission time of the fourth mono-multi (55) and the D-type flip-flop (54).

Next, consider the case of a search or the like, where the laser light spot from the pickup crosses a groove on the disk. At this time, as described above Goes low and the first and second NAND gates (50) (5
2) opens.

Then, a tracking error signal as shown in FIG. 4 (c) is applied to the terminal (36), converted into a square wave like the total reflected light amount instruction signal, level-shifted, and output from the second inverter (45) (f). Becomes

The rising of the output (f) of the second inverter (45) triggers the first mono-multi (46) and the falling thereof triggers the second mono-multi (47). ). Assuming that the pickup means is moving from the inner circumference to the outer circumference, the relationship between the repeatedly reflected light amount instruction signal and the tracking error signal is shown in FIGS.
It becomes like. That is, the pulse (g) related to the rising edge of the tracking error signal is selected and applied to the ▲ ▼ input terminal (57a) of the counter (57). ((Ri)
(E)).

Therefore, when the pickup means moves from the inner circumference to the outer circumference in the tracking-off state, the content of the counter (57) increases each time the track means crosses one track groove.

Conversely, when the laser light spot of the pickup means moves from the outer circumference to the inner circumference, the relationship between the total reflected light amount instruction signal and the tracking error signal is as shown in FIGS. Therefore, the pulse (H) related to the trailing edge of the tracking error signal is selected by the second AND gate (49) and applied to the ∇ input terminal (57b) of the counter (57).

That is, when the pickup means moves from the outer circumference to the inner circumference, the content of the counter (57) decreases each time it crosses one track groove.

Further, even in the tracking-off state, the counter (57) is incremented each time the disk makes one revolution. This is because the guide groove is formed in a spiral shape.

In other words, assuming that the laser spot light of the pickup means is stationary with tracking off, the laser spot light moves from the outer circumference to the inner circumference with respect to the guide groove on the disk due to the rotation of the disk. become.
Then, one rotation of the disk traverses one track, so one pulse is applied to the input (57b). However, since the laser light spot actually returns to the original position by making one rotation, the contents of the counter must not change. Therefore, one pulse is supplied to the input (57a) based on the one rotation detection pulse.

The same applies to the movement from inner circumference to outer circumference or outer circumference to inner circumference.

However, simply ORing with the output of the NAND gate (50) and applying it causes a problem when the two pulses overlap. Therefore, in the circuit of FIG. 1, the fourth mono-multi (5
By applying the output of the first inverter (41) to the A input (55a) of 5), the output (e) of the fourth monomulti (55) is not output until the output of the first inverter (41) becomes low level. I am doing it.

That is, when the output of the first inverter (41) is at a high level (that is, the period when the first AND gate output is obtained),
The fourth mono-multi (55) composed of LS123 is not triggered even if the output (d) of the D-type flip-flop (54) becomes high level. Then, since the D-type flip-flop (54) stores that the one-rotation detection signal is detected, when the first inverter (41) falls, the fourth mono-multi (55) is triggered, and The same operation is performed (see FIG. 6 (b), (c), (d) and (e)). There is no counting error.

As described above, with the configuration of FIG. 1, it is possible to count the number of tracks accompanying the movement of the pickup means in both the tracking state and the tracking off state. Therefore, for example, by clearing the counter (57) at the start track of the magneto-optical recording portion (3) on the disc (1) in FIG. 1, the count content of the counter (57) is the position of the pickup means on the disc. Is expressed in the form of the number of tracks.

The initial position determining means (58) is provided for this purpose. The following may be considered as the initial position determining means (58). First, a signal indicating the start of the magneto-optical recording portion (3) (or the end of the optical recording portion (4)) to the optical recording portion (4) or the start of the magneto-optical recording portion (3) as described above. If the time code indicating the time to the track is recorded, this signal is read by the pickup means (the output of the non-differential amplifier (28) in FIG. 2 is used because it is recorded by the uneven pits), There is a way to clear the counter (57) accordingly. Second, second
Since the output of the non-differential amplifier (28) in the figure can read only the information recorded by the uneven bits, when the output of this amplifier (28) stops, the optical recording part (4) and the magneto-optical recording part are This is a method of determining that it is the boundary of (3).

In both cases, the point that the optical recording portion (4) exists in the lead-in portion of the disc and the lead-in portion is reproduced prior to recording is utilized.

In the example of FIG. 1, the contents of the counter (57) are cleared, but a method of setting a predetermined preset value can also be used. Disc of the same size as a compact disc (1)
In this case, since the number of tracks is 20,000 or more, the counter (57) is a 15-bit counter. Then, the position frequency conversion means (59) converts the 15-bit digital output into a frequency.

The following are possible conversion methods. First, the output of the counter (57) is D / A converted, and a bias voltage is applied to this voltage to create a voltage proportional to the distance from the disk center to the pickup means. Then, the reciprocal of the voltage proportional to this distance is calculated and applied to the voltage / frequency converter to create a frequency signal inversely proportional to the position.

It is also possible to create a frequency signal by converting the output of the counter (57) into data proportional to the distance from the center, presetting it in the down counter, and repeating down counting with the reference clock.

Further, a method of preliminarily storing frequency data at each position in a memory, reading the frequency data using the output of the counter (57) as an address signal, and creating a predetermined frequency signal based on the frequency data by a microcomputer is also available. Conceivable.

In the above three methods, it is not necessary to use all 15-bit outputs. For example, if the upper 8 bits are used, a frequency signal that changes in units of about 100 can be created.

In this way, when a frequency signal having a frequency inversely proportional to the position of the pickup means is created, the rotation control means (61) of the spindle motor (60) compares the phase of this frequency signal with the FG signal. , Constant linear velocity control is performed.

Although the above embodiment is the control device of the disk rotation speed, it is also possible to detect the address scanned by the pickup means by using the track counting means.

(G) Effect of the Invention As described above, according to the present invention, the position of the pickup means is known by counting the tracks, and the rotation of the spindle motor is controlled. Therefore, it is not affected by the eccentricity of the disk-shaped recording medium. The effect is that the configuration around the pickup means is not complicated.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment, FIG. 2 is a block diagram showing an optical system, and FIG. 3 is a plan view showing a magneto-optical disk.
FIGS. 4, 5, 6, and 7 are waveform diagrams for explaining the operation, FIG. 8 is a perspective view of the pickup means, FIG. 9 is a perspective view showing a magneto-optical disk, and FIG. FIG. 11 is a block diagram showing a format of information, FIG. 11 is a block diagram showing one rotation detecting means, FIG. 12 is a block diagram showing a transfer device of a pickup means, and FIG. 13 is a diagram explaining position detecting means. (1) ... disk, (6a) ... guide groove, (58) ... initial position determining means, (57) ... counter.

Claims (1)

[Claims] 1. A disk-shaped recording medium rotation control device for recording or reproducing information on a disk-shaped recording medium having a spiral guide groove formed therein while tracking the guide groove, and a tracking error signal in a tracking-off state. Based on a signal generated from the amount of reflected light and the amount of reflected light, counting means for adjusting the number of interlacing guide grooves and the number of rotations of the disk-shaped recording medium after initial position detection are adjusted, and the output of the counting means Frequency conversion means for converting to a reference frequency, and based on the reference frequency emitted from the frequency conversion means,
A rotation control device for controlling the rotation of the disk-shaped recording medium, and a rotation control device for controlling the rotation of the disk-shaped recording medium.