JPH10162395A - Tilt servo mechanism and tilt servo method for disk recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time for performing tilt servo and enable high speed access. SOLUTION: A tilt servo mechanism is provided with a motor M1 sliding a pickup 6 emitting a laser beam to a back face of a disk in the direction of a radius at the time of recording and reproducing, and a motor M2 tilting the pickup to the disk corresponding to a warp of a disk. A servo circuit 5 is connected to a memory 4 storing a tilt angle of the pickup 6, previously slides the pickup 6, and stores a tilt angle of the pickup 6 at the prescribed position on the direction of a radius of the disk in the memory 4. At the time of recording and reproducing, the circuit 5 reads a tilt angle corresponding to this prescribed position from the memory 4, and tilts the pickup 6 by a tilt angle while the pickup 6 is moved to the prescribed position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt servo mechanism and a tilt servo method for a disk recording / reproducing apparatus for tilting the direction of irradiation of a laser beam from a pickup in accordance with a warp of a disk.

[0002]

2. Description of the Related Art In general, a disk recording / reproducing apparatus is provided with a pickup slidably below a disk in a radial direction of the disk, irradiates a laser beam from the pickup to a back surface of the disk, and picks up a reflected signal again by the pickup. read. As shown in FIG. 11, a plurality of concave pits (73) (73) are formed along the circumferential direction on the back surface of the disk (7).
A digital signal consisting of 0 and 1 is reproduced by a difference in intensity of reflected light when a laser beam is applied to the pit (73) and a portion other than the pit (73). FIG. 12 is a diagram showing a spot of the laser beam applied to the disk (7). Optically, the spot diameter d1 is proportional to a value obtained by dividing the wavelength λ of the laser beam by the sine of the incident angle θ. . This sin θ is defined as NA (numerical
aperture), and the larger the NA, the smaller the diameter d1.
For example, in the case of a compact disc, NA = 0.
45. Here, large diameter of laser disk etc.
In the case of a (30 cm) disk, the downward warpage of the disk outer periphery may be large due to the weight of the disk.
A tilt servo mechanism that inclines the irradiation direction of the laser light according to the warp is generally used so that the laser light from the pickup (6) accurately returns to the pickup (6).

FIG. 10 schematically shows the tilt servo mechanism.
(a) and (b) show. The pickup (6) is a sub-chassis (9) that slides on the chassis (1) in the radial direction of the disk (7).
And pivots in a vertical plane including the radial direction. The pickup (6) includes a light emitting unit (61) that emits infrared light toward the back surface of the disk (7), separately from a known laser light emitting element (not shown) that emits laser light for reading a signal on the back surface of the disk. ) And a light receiving section (60) for receiving the infrared light reflected by the disk (7). A shaft (68) projects laterally from the pickup (6) and engages with a cam (90) that slides radially on the sub-chassis (9). The pickup (6) is connected to a control circuit (92) to which a signal from the light receiving section (60) is input, and the control circuit (92) is connected to a mechanism (not shown) for sliding the cam (90). .

When there is no warp on the disk (7), FIG.
As shown at 0 (a), the pickup (6) emits infrared light directly above the light emitting section (61). The infrared light reflected on the back surface of the disk (7) enters the light receiving section (60) of the pickup (6). As shown in FIG. 10 (b), when the disk (7) is warped downward, the control circuit (92) controls the cam (9).
Then, the pickup 6 is rotated counterclockwise about the pivot 91 with the sub-chassis 9. The pickup (6) continues to emit infrared light toward the disk (7), and when the amount of reflected light incident on the light receiving section (60) becomes maximum, the control circuit (92) controls the cam (90). Is stopped, and the rotation of the pickup (6) is stopped.

[0005]

The tilt servo mechanism is generally used for a laser disk having a large warp, but it is not necessary to use a tilt servo for a read-only compact disk having a small diameter (12 cm). Absent. However, in recent years, a DVD (Digital Video Disc) has been proposed which not only reproduces using a disc having the same diameter as a compact disc but also records video and audio signals. In the DVD, since a video signal is also recorded, it is necessary to record information at a high density, and the interval between the pits (73) and (73) in the disk circumferential direction is narrow. Accordingly, it is necessary to reduce the spot diameter d1 of the laser beam in FIG.
A pickup (6) having a lens having an A value of about 0.6 must be used. At the same time, slight warpage of the disk affects recording and reproduction, so that it is necessary to use a tilt servo mechanism like a laser disk.

[0006] By the way, as a feature of the DVD, which is superior to a conventional compact disc or the like, there is a demand in the market for high-speed access, that is, a reduction in the time from when the reproduction is in a standby state until the video is actually displayed on the screen. In the conventional tilt servo, after the pickup (6) is slid to find the information recorded on the disk, the pickup (6) is tilted. However, the actual tilt angle of the pickup (6) is within 1 degree, and if the pickup (6) is tilted quickly, accurate tilt servo cannot be performed. Therefore, it is necessary to tilt the pickup 6 slowly, and thus, even if the sliding speed of the pickup 6 is high, high-speed access, which is a market need, cannot be achieved. SUMMARY OF THE INVENTION It is an object of the present invention to shorten the time for performing tilt servo and to enable high-speed access.

[0007]

A tilt servo mechanism irradiates a laser beam on the back surface of the disk (7) while sliding in the radial direction of the disk (7) during recording and reproduction.
Is tilted with respect to the disk (7) in accordance with the warp of the disk (7), and the laser light reflected by the disk (7) reaches the pickup (6). The tilt servo mechanism includes a memory (4) for storing an inclination angle of the pickup (6) and a pickup (6) at a predetermined position in a radial direction of the disk (7) by sliding the pickup (6) in advance. A storage unit for storing the tilt angle in the memory (4), and a tilt angle corresponding to the predetermined position is read from the memory (4) and picked up
And light receiving attitude changing means for tilting the pickup (6) by the tilt angle during the movement to the predetermined position in (6).

[0008]

[Operation and effect] The tilt servo mechanism
(7) The tilt angle at a predetermined position in the radial direction is stored in the memory (4)
At the time of recording and playback
During the sliding of (6), the pickup (6) is tilted. By this operation, it is possible to reduce the time from when a signal indicating that a predetermined position on the disk (7) should be reproduced to when the information is reproduced. That is, conventionally, the pickup (6) is slid to a predetermined position, and then the pickup (6) is moved.
However, as shown in this example, when the pickup (6) is completely slid by tilting the pickup (6) during the sliding of the pickup (6), the attitude of the pickup (6) is already set to the disc position. And the recording / reproducing operation can be executed immediately, so that high-speed access is possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1A is a plan view of a disk recording / reproducing apparatus provided with a tilt servo mechanism, and FIG.
FIG. 2 is a front view of the above. A turntable (7) on which a disc (7) is mounted is mounted on a motor shaft of a spindle motor (M3) fixed on the chassis (1).
The disc (7) is mounted on the turntable (70), pressed by the clamper (71) from above, and rotated integrally with the turntable (70). Clamper (7
The description of the lifting mechanism in 1) is omitted.

Below the disk (7), a support frame (2) is pivotally supported (10) on the chassis (1) and tilts in a vertical plane including the radial direction of the disk (7). Guide shafts (20) (20) extending along the radial direction of the disc (7) on the support frame (2)
Are provided on the guide shafts (20) and (20).
(6) is slidably fitted. There are various possible mechanisms for moving the pickup (6).
For example, as shown in FIG. 1, a rack (62) is provided on the side surface of the pickup (6), and the power of the motor (M1) provided on the chassis (1) is transmitted to the intermediate gears (65) and (66). Through the rack section
(62) is conceivable.

The support frame (2) is provided with a side wall (21) orthogonal to the sliding direction of the pickup (6).
A cam groove (22) extending obliquely upward is provided. Outside the support frame (2), a slide body (3) is slidably provided facing the side wall (21). Slide body (3) is side wall
The shaft (30) protrudes toward (21), and the shaft (30) is fitted in the cam groove (22). A rack surface (31) is formed on the slide body (3), and a motor (M2) is provided on the side of the rack surface (31) and on the back side of the chassis (1). Rack surface (31)
Is engaged with a pinion (35) attached to the motor (M2). If the motor (M2) rotates, the slide (3)
Slides at right angles to the sliding direction of the pickup (6), and the shaft (30) fitted in the cam groove (22) slides, whereby the support frame is moved.
(2) tilts around a pivot (10) with the chassis (1).
Therefore, the pickup with respect to the axis (72) of the disk (7)
The inclination angle of (6) changes. As shown in FIG. 1, a light emitting unit that emits infrared light is provided on a pickup (6) as in the conventional case.
(61) and a light receiving section (60) are provided. In FIG. 1, for convenience of explanation, the light emitting unit (61) and the light receiving unit (60) are shown separately, but they are actually provided almost integrally.

(First Example) FIG. 3 is a block diagram of a circuit for driving the motors (M1) and (M2). A motor (M1) for sliding the pickup (6) and a motor (M1) for rotating the support frame (2)
As is well known, FG (frequency gener
ator) Counter that emits pulses and counts the number of FG pulses
It is connected to the servo circuit (5) via (51) and (52). The output from the light receiving section (60) of the pickup (6) is
Amplified by 0) and input to the servo circuit (5). The servo circuit (5) knows how much the motors (M1) and (M2) have rotated based on the number of FG pulses counted by the counters (51) and (52).

Since the reduction ratio from the motors (M1) and (M2) to the rack portion (62) of the pickup (6) and the rack surface (31) of the slide body (3) is constant, the pickup (6) is driven. Pickup (6) by the number of FG pulses of motor (M1)
The motor that tilts the support frame (2) can know the sliding amount of
Support frame (2) and pickup from (M2) FG pulse number
It is possible to know the inclination angle at which (6) is inclined with respect to the axis (72) of the disk (7). The servo circuit (5) has a counter (51)
From the number of FG pulses of the motors (M1) and (M2) measured by (52),
A program for calculating the sliding amount of the pickup (6) and the inclination angle of the pickup (6) is stored. Servo circuit
(5) is connected to a memory (4) in which the tilt angle of the pickup (6) is temporarily stored using the position of the disk (7) in the radial direction as an address.

In the case of a DVD, high-speed access is required. In this example, while the pickup (6) is moving,
Tilt the pickup (6). Hereinafter, this procedure will be described with reference to the flowcharts of FIGS. First, before performing high-speed access, insert the pickup (6)
It is moved to the inner periphery A (see FIG. 4) of (7) (S1). The detection of the inner peripheral portion A of the disk (7) is performed by reading the lead-in area data (Readin area data) written in the inner peripheral portion A. The disc (7) is sandwiched between the turntable (70) and the clamper (71), and while the disc (7) is rotated, the motor (M2) is energized and the
Slide (3) to tilt the support frame (2) about the pivot (10) with the chassis (1). The pickup (6) irradiates the back surface of the disc (7) with infrared light from the light emitting section (61), and the light receiving section (60).
When the reflected light from the disk (7) incident on the motor (7) becomes maximum, the servo circuit (5) stops the power supply to the motor (M2) and stops the sliding of the slide body (3). Servo circuit (5)
Is the motor (M2) counted by the counter (52) by the time of the stop.
Of the support frame (2) is calculated from the number of FG pulses of
2), the value of the inclination angle α is stored in the memory (4).

Next, the servo circuit (5) energizes the motor (M1) to slide the pickup (6) from the inner peripheral portion A to the outer peripheral portion D of the disk (7) (S3). A plurality of predetermined positions at which the pickup (6) should temporarily stop are set at regular intervals on the disk radial direction, and the distance between the predetermined positions is stored in the servo circuit (5) in advance. . In this example, as shown in FIG. 4, in addition to the inner peripheral portion A and the outer peripheral portion D, two predetermined positions B between the inner peripheral portion A and the outer peripheral portion D,
C is set. For convenience of explanation, the predetermined position is a total of 4
However, it is needless to say that the number is not limited to four.

When the servo circuit (5) detects that the pickup (6) has reached a predetermined position from the number of FG pulses of the motor (M1), it stops sliding of the pickup (6).
As described above, the motor (M2) is energized at the predetermined position,
The support frame (2) is tilted, and the tilt angle is calculated (S4). Thereafter, the above operation is repeated (S5), and the predetermined positions B and C
The inclination angles β, γ, and δ at the outer peripheral portion D of (7) are calculated, and the values of each inclination angle are sequentially stored in the memory (4) using the position in the disk radial direction as an address. The tilt angle may be obtained by averaging a plurality of calculation results.

When the storing operation to the memory (4) is completed, the servo circuit (5) returns the pickup (6) to the disk inner peripheral portion A and waits (S6). When an operation signal indicating that the information at any one of the predetermined positions B and C is to be reproduced is input from the outside to the servo circuit (5) (S7), the servo circuit (5) reads the information from the memory (4). The tilt angle at the predetermined position is called.
The operation signal is the motor (M3) linked to the turntable (70)
(See FIG. 2) is also input to a circuit (not shown) for driving
The turntable (70) rotates.

Next, the servo circuit (5) energizes the motor (M1) and slides the pickup (6) to a predetermined position.
(S8), energize the motor (M2), slide the slide (3), and attach the support frame (2) and the pickup (6) to the chassis.
It is rotated around the pivot 10 with (1) to the tilt angle retrieved from the memory (4) (S9). That is, the servo circuit (5)
Turns the pickup (6) to change the light receiving position of the infrared light reflected by the disk (7). Servo circuit
(5), when it is detected from the number of FG pulses of the motor (M2) that the support frame (2) has tilted to the tilt angle read from the memory (4), the power supply to the motor (M2) is stopped ( S10). When the pickup (6) reaches a predetermined position, the motor (M1)
The power supply to the disk (7) is stopped (S11), and the signal on the disk (7) is reproduced in this state.

As described above, the tilt angle at a predetermined position in the disk radial direction is stored in the memory (4) in advance,
When the pickup (6) slides to the predetermined position, the pickup (6) and the support frame (2) are tilted so that a signal indicating that the predetermined position on the disk should be reproduced is input, and then the information is reproduced. The time until the operation is completed can be shortened. That is, in the prior art, the pickup (6) was slid to a predetermined position and then the pickup (6) was tilted.
By tilting (6), high-speed access becomes possible.

The present embodiment relates to a DVD using a disk having a diameter of 12 cm, and the amount of warpage is smaller than that of a laser disk using a disk having a diameter of 30 cm. Therefore, the disk is warped substantially linearly, and the amount of warpage of the disk at a predetermined position and the distance from the inner peripheral portion of the disk to the predetermined position are substantially directly proportional. The average value of the inclination angles of the adjacent predetermined positions corresponds to the inclination angle at an intermediate portion between the adjacent predetermined positions. Therefore, if the average value of the inclination angles of adjacent predetermined positions is calculated and stored in the memory (4), the data of the amount by which the pickup (6) should be inclined can be obtained at an arbitrary point in the disk radial direction. Can be increased, and more precise high-speed access becomes possible. That is,
The same effect as increasing the predetermined position can be obtained. The intermediate portion between the adjacent predetermined positions is indicated by points E, F,
G, the inclination angles at the points E, F, and G are ε,
ζ and η. Further, as shown by the dotted line in FIG. 3, it is necessary to connect an arithmetic circuit (8) for calculating the average value of the inclination angles of adjacent predetermined positions to the servo circuit (5) and the memory (4).

(Second Example) The applicant has also proposed a high-speed access shown in the flowchart of FIG. This example has the same internal blocks as the first example, but the operation of the servo circuit (5) is different. First, before performing high-speed access, the pickup (6) is moved to the inner peripheral portion A of the disk (7) (S20), and the motor (M2) is energized while the disk (7) is rotated. The slide body (3) is slid, and the support frame (2) is tilted about the pivot (10) with the chassis (1). After the reflected light from the disk (7) incident on the light receiving section (60) becomes maximum, the motor (M2) is stopped. The servo circuit (5) is configured to measure the FG of the motor (M2) measured by the counter (52).
From the number of pulses, the inclination angle α of the support frame (2) and the pickup (6) in the inner peripheral portion A is calculated (S21) (see FIG. 9) and stored in the memory (4). This operation is the same as in the first example.

Next, the servo circuit (5) energizes the motor (M1) to move the pickup (6) toward the outer periphery D of the disk (7) (S22). When the counter (51) detects that the pickup (6) has reached the outer peripheral portion (D) of the disk (7) from the counted number of FG pulses, the sliding of the pickup (6) is stopped. The servo circuit (5) energizes the motor (M2), tilts the support frame (2) about the pivot (10), stops the motor (M2), calculates the tilt angle δ (S23), It is stored in the memory (4). An arithmetic circuit (8) connected to the memory (4) and the servo circuit (5) reads the inclination angles α and δ from the memory (4) and calculates an average value (α + δ) / 2 of both inclination angles ( S24), the calculation result is transmitted to the servo circuit (5). The servo circuit (5) energizes the motor (M1), returns the pickup (6) to the inner peripheral portion A of the disk (S25), and energizes the motor (M2) while the pickup (6) is moving. (2) and the pickup (6) are rotated about the pivot (10) with the chassis (1), and tilted to the tilt angle (α + δ) / 2 (S26). When the pickup (6) reaches the inner periphery A of the disk (7), the motor
The power supply to (M1) is stopped, and the sliding of the pickup (6) is stopped. The pickup 6 waits for the next reproduction operation while being tilted by the tilt angle (α + δ) / 2.

When reproducing the inner peripheral portion A of the disc (7), the pickup (6) reaches the reproducing position,
(α + δ) / 2 = (α-δ) / 2
When reproducing the outer peripheral portion D of (7), the pickup (6) may be tilted by δ− (α + δ) / 2 = (δ−α) / 2 after reaching the reproduction position. Further, when reproducing the intermediate position E between the inner peripheral portion A and the outer peripheral portion D of the disc (7), it is not necessary to tilt the pickup (6). That is, the pickup 6 may be tilted in the range of (α−δ) / 2 to (δ−α) / 2 at the time of reproduction, and the tilt angle range becomes narrower than in the past. In this way, by tilting the pickup 6 before starting the reproducing operation, the reproducing operation is accelerated, and high-speed access can be achieved. The angle at which the pickup (6) is initially tilted
The reason why (α + δ) / 2 is set is that the time required for tilting the pickup (6) at the inner peripheral portion A and the outer peripheral portion D of the disk (7) is made equal by setting the inclination angle. It is.

In the above example, the inclination angles at the inner peripheral portion A and the outer peripheral portion D of the disk 7 are read from the memory 4 to determine the angle at which the pickup 6 should be inclined. However, from the inner peripheral portion A of the disk (7) to the servo circuit (5),
The distance between the inner peripheral portion A and the outer peripheral portion D to the intermediate position E is stored, and the pickup (6) is moved to the intermediate position E in advance. At the intermediate position E, the pickup (6) may be tilted so that the amount of infrared light incident on the light receiving section (60) is maximized, and the pickup (6) may be made to stand by at the inclined position. That is, the servo circuit (5) serves as a means for previously tilting the pickup (6) by the tilt angle corresponding to the intermediate position E. In this case, the memory (4) and the arithmetic circuit (8) become unnecessary, and the configuration is simplified.

The tilt servo mechanism according to the above example is a DVD which is expected to replace a CD-ROM in the near future.
-Applicable to ROM. That is, by providing the configuration of the above example, the DVD-ROM can be accessed at a high speed comparable to a CD-ROM.

The description of the above embodiments is for the purpose of illustrating the present invention and should not be construed as limiting the invention described in the appended claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1A is a plan view of a tilt servo mechanism, and FIG. 1B is a side view of the tilt servo mechanism as viewed from the direction of arrow A in FIG.

FIG. 2 is a front view of the same.

FIG. 3 is a block diagram illustrating a circuit configuration of a tilt servo mechanism.

FIG. 4 is a diagram showing a predetermined position of a disk and an angle at which a pickup should be tilted.

FIG. 5 is a diagram showing a predetermined position of a disc and an angle at which a pickup should be tilted.

FIG. 6 is a flowchart showing an operation procedure of a tilt servo.

FIG. 7 is a flowchart illustrating an operation procedure of a tilt servo.

FIG. 8 is a flowchart showing an operation procedure of a tilt servo.

FIG. 9 is a diagram showing a predetermined position of a disk and an angle at which a pickup should be tilted.

FIG. 10 is a side view of a conventional tilt servo mechanism.
(a) shows the case where the disk has no warp, and (b) shows the case where the disk is warped.

FIG. 11 is a bottom view showing pits on the back surface of the disk.

FIG. 12 is a side view showing a spot of a laser beam.

[Explanation of symbols]

 (4) Memory (6) Pickup (7) Disk

Claims (6)

[Claims] 1. A pickup (6) for irradiating a laser beam to the back surface of a disk (7) while moving in the radial direction of the disk (7) during recording / reproduction, the disk (7) corresponding to the warp of the disk (7). In a tilt servo mechanism for tilting the laser light reflected by the disc (7) to the pickup (6) and reaching the pickup (6), a memory (4) for temporarily storing the tilt angle of the pickup (6)
Then, move the pickup (6) in advance and set the disc (7)
Storage means for storing the tilt angle of the pickup (6) at a predetermined position in the radial direction in the memory (4), and storing the tilt angle corresponding to the predetermined position at the time of recording / reproducing.
A tilt servo mechanism for a disc recording / reproducing apparatus, comprising: a light receiving attitude changing means for reading from (4) and tilting the pickup (6) by the tilt angle while the pickup (6) is moving to a predetermined position. 2. The storage means is connected to an arithmetic means for calculating an average value of the inclination angles of adjacent predetermined positions, and the storage means calculates the inclination angle of the pickup (6) at the predetermined position together with the calculation means of the arithmetic means. 2. The tilt servo mechanism according to claim 1, wherein the result is stored in a memory (4). 3. A pickup (6) for irradiating a laser beam on the back surface of the disk (7) while moving in the radial direction of the disk (7) during recording / reproduction, according to a warp of the disk (7). (4) In a tilt servo mechanism for tilting the laser light reflected by the disk (7) to reach the pickup (6), a memory (4) for temporarily storing the tilt angle of the pickup (6)
From the inclination angles of the pickup 6 at the inner peripheral portion A and the outer peripheral portion D of the disk 7 previously recorded in the memory 4, the inner peripheral portion A and the outer peripheral portion D of the disk 7 are determined. Calculating means for calculating the tilt angle of the pickup (6) at the intermediate position E; and a pickup (6) at a predetermined position in the radial direction of the disk.
A tilt servo mechanism for a disk recording / reproducing apparatus, wherein a tilt means for tilting the pickup (6) in advance by a tilt angle based on a calculation result of the calculating means is provided before moving. 4. A pickup (6) for irradiating a laser beam on the back surface of the disk (7) while moving in the radial direction of the disk (7) during recording / reproduction, according to a warp of the disk (7). ), The laser beam reflected by the disk (7) reaches the pickup (6) in a tilt servo mechanism, and the intermediate position E between the inner peripheral portion A and the outer peripheral portion D of the disk (7) is previously determined.
A tilt servo mechanism for a disk recording / reproducing apparatus, characterized in that an irradiation position determining means for moving the pickup (6) in advance and tilting the pickup (6) in advance at the inclination angle at the intermediate position E is provided. 5. A pickup (6) for irradiating the back surface of a disk (7) with a laser beam during recording and reproduction, and a pickup
Memory for storing the tilt angle of (6) with respect to disk (7)
(4) is provided, the pickup (6) is moved in advance, and the tilt angles of the pickup (6) at a plurality of predetermined positions in the radial direction of the disk (7) are stored in the memory (4). The tilt angle corresponding to the predetermined position is read from the memory (4), and during the movement of the pickup (6) to the predetermined position,
(6) A tilt servo method for a disk recording / reproducing device in which the tilt angle is adjusted to the tilt angle. 6. A pickup (6) for irradiating a back surface of a disk (7) with a laser beam during recording and reproduction, and a pickup.
A memory (4) for storing the inclination angle of the disk (7) with respect to the back surface of the disk (7) is provided, and the inclination angle of the pickup (6) at the inner peripheral portion A and the outer peripheral portion D of the disk (7) is previously stored in the memory (4). ), And an intermediate position E between the inner peripheral portion A and the outer peripheral portion D of the disc (7) from both inclination angles.
Before the pickup (6) moves to a predetermined position in the radial direction of the disc, the pickup (6) is tilted to the calculated inclination angle before disc recording. A tilt servo method for a playback device.