JPH05325447A - Moving speed detecting device for optical pickup - Google Patents

Abstract

PURPOSE:To detect a good pickup moving speed even in the case of signal disorder by correcting the pickup moving speed when a track transverse signal goes out of order due to a preformat area. CONSTITUTION:A reference signal generating means 14 generates a reference signal 15 for showing preformat area irradiation with a light spot at the time of track follow-up operation. Also, a predictive window signal generating means 16 generates a predictive window signal for showing the preformat area irradiation with the light spot from the reference signal 15 at the time of access operation. On the other hand, a track transverse signal detecting means 6 detects a track transverse signal 7 and a periodic signal generating means 8 generates a periodic signal 9 from a period of the track transverse signal 7. Moreover, since an optical pickup moving speed detecting means 18 generates a pickup moving speed signal from the periodic signal 9 and corrects it by the predictive window signal 17, influence of light reflection factor of a preformat area can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving speed detecting device for an optical pickup used in an optical disk device.

[0002]

2. Description of the Related Art Since the track pitch of an optical disk, which is a recording medium of an optical disk device, is as small as 1 to 2 .mu.m, it is highly necessary to allow an optical pickup to access this track at high speed and perform a precise tracking servo operation. Control technology is required. Therefore, when the optical disk device was first introduced to the world, the slow access time was a major drawback of the optical disk device. However, in recent years, the slowness of access time has been considerably improved, and optical disk devices are becoming popular.

In an optical disk device, a tracking servo mechanism for moving a light spot onto a target track and following the track has a two-stage servo system in which a rough movement is performed by a linear motor or the like and a minute movement is performed by a coil actuator or the like. Widely adopted. In this method, a linear motor is used to roughly move the base on which the coil actuator and the components forming the optical system are mounted to the vicinity of the target track, and then the precise tracking operation is performed by the coil actuator. This operation is generally called an access operation. During the access operation, the optical pickup is controlled as follows. First, set the target speed according to the distance from the current track to the target track, that is, the number of remaining tracks to the target track, and use this set value as the speed command value of the servo mechanism that moves the optical pickup in the disk radial direction. Give, control the optical pickup movement speed,
Perform positioning. The moving speed of the optical pickup is detected based on the frequency of the sinusoidal cross-track signal that appears when the light spot crosses the track. Accurate detection of the moving speed of the optical pickup is extremely important for improving the accuracy of access control. The configuration of an access control system using a conventionally adopted moving speed detecting device for an optical pickup will be described below.

First, FIG. 8 schematically shows an access control system of a conventional optical pickup. Reference numeral 1 denotes an optical disc, in which groove-shaped tracks having a minute width are formed in the circumferential direction. In addition, a pre-formatted area is periodically provided in each track for describing data such as a track address. Reference numeral 2 denotes an objective lens that focuses the laser light and forms a light spot 3 on the track. An optical pickup 4 is configured to be driven in the radial direction of the disc. Reference numeral 5 is a sensor symbol detected by the optical pickup from the reflected light of the optical disc. Reference numeral 6 is a track crossing signal detecting means, which processes the sensor signal to obtain a track crossing signal 7. Reference numeral 8 denotes a periodic signal generating means, for example, a trigger signal generating means for generating a trigger signal when the cross-track signal exceeds a zero level given as a reference level, and a period of the trigger signal is measured and used as a periodic signal 9. It is composed of an output cycle measuring means. Reference numeral 10 is an optical pickup moving speed detecting means. Since the moving speed of the optical pickup is the reciprocal of the cycle of the track crossing signal, the reciprocal of the periodic signal is calculated to calculate the moving speed signal 11 of the optical pickup.
Is output. Reference numeral 12 is an access control means, which controls the moving speed of the optical pickup to match the target speed as described above, and positions the optical pickup. Reference numeral 13 is a drive signal for the optical pickup.

Next, FIG. 9 shows a process of detecting the moving speed of the optical pickup in a state where deceleration is performed at a constant acceleration in the radial direction of the disk. FIG. 9A shows a track crossing signal,
9B shows the above-mentioned trigger signal, the solid line in FIG. 9C shows the moving speed signal of the optical pickup, and the dotted line in FIG. 9C shows the actual moving speed of the optical pickup. The period of the track crossing signal is inversely proportional to the moving speed of the optical pickup, and the period is long. If the period of the track crossing signal is detected from the trigger signal generated when the track crossing signal exceeds the zero level and the reciprocal thereof is obtained, it becomes the moving speed signal of the optical pickup as shown by the solid line. However, since the trigger signal is discretely generated, the moving speed detection value is shown in FIG.
As shown by the solid line in (c), at the same time, there is a delay of one sampling time of the trigger signal on average.

[0006]

As described above, the moving speed of the optical pickup can be detected by the above conventional structure. However, since the light reflectance of the preformatted area of the optical disc is different from that of the data area, when the light spot passes through the preformatted area, the track crossing signal is
Disturbance occurs like 0 (a). Therefore, the correlation between the period of the track crossing signal and the moving speed of the optical pickup is distorted, and as a result, the moving speed detection signal of the optical pickup as shown by the solid line in FIG. 10C is obtained, and the accurate moving speed cannot be detected. Had a problem.

The present invention solves such a problem, and an object of the present invention is to provide a moving speed detecting device for an optical pickup which is not affected by the preformat area.

[0008]

In order to achieve this object, a moving speed detecting apparatus for an optical pickup according to the present invention generates a reference signal indicating a timing at which a light spot irradiates a preformatted area during a track following operation. Means, a means for generating a prediction window signal for estimating the timing at which the light spot irradiates the preformatted area from the reference signal during the access operation, a means for detecting the track crossing signal, and a cycle for measuring the track crossing signal. , A means for generating a periodic signal, a means for generating a moving speed signal of the optical pickup from the periodic signal, and a means for receiving the prediction window signal and correcting the moving speed signal of the optical pickup.

[0009]

According to the present invention, since the moving speed of the optical pickup which is affected by the disturbance of the track crossing signal when the light spot passes through the preformatted area is corrected by the above-described structure, the moving speed of the optical pickup can be satisfactorily detected. In addition, the timing at which the light spot passes through the pre-formatted area is accurately detected during the track following operation, and the passage timing is predicted from the timing during the access operation, so that the moving speed can be always corrected at the correct timing. ..

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an access control system of an optical pickup according to an embodiment of the present invention. In FIG. 1, 1 is an optical disk, 2 is an objective lens, 3 is a light spot, 4 is an optical pickup, 5 is a sensor signal, 6 is a track crossing signal detecting means, 7 is a track crossing signal, 8 is a periodic signal generating means, 9 Is a periodic signal, 11
Is a moving speed signal of the optical pickup, 12 is an access control means, and 13 is a drive signal of the optical pickup. These are the same as in the conventional example. 14 is a reference signal generating means, 1
Reference numeral 5 is a reference signal, 16 is a prediction window signal generating means, 1
Reference numeral 7 is a prediction window signal. Reference numeral 18 denotes a moving speed detecting means of the optical pickup which receives the prediction window signal and corrects the moving speed signal of the optical pickup while generating the moving speed signal of the optical pickup from the periodic signal.

Here, the reference signal generating means 14 outputs a reference signal 15 indicating the timing at which the light spot irradiates the preformatted area during the track following operation. The reference signal is generated, for example, as in 1) and 2) described below.

1) Preformatted areas having different light reflectances which appear periodically are detected by the difference between the reflected light quantity and the reference reflected light quantity, and the cycle and timing of irradiation of the light spot on the preformatted area are output as a reference signal. .. An example of the configuration of this method is shown in FIG. 2 and its operation is shown in FIG. 19 is a track, and 20 on the track is a data area,
Reference numeral 21 is a preformatted area in which light reflection is smaller than that in the data area. Reference numeral 22 is a reflected light amount detecting means, which outputs a signal A1 proportional to the amount of reflected light from the track 19. Reference numeral 23 is a comparison means, which compares a reference voltage V2 corresponding to the reference light amount with a voltage V1 indicating the reflected light amount, and V1 is V2.
When it is larger, L level signals D11, D13, D1
5, D17, D19 are generated, and when they are small, H level signals D12, D14, D16, D18 are generated. Reference numeral 24 is a reference signal generating means for outputting the generation cycle T1 of the H level signal of the signal A1 and the generation time t0 as a reference signal.

2) Of the data on the track which is being read sequentially, the period and timing of reading the signal described in the preformat area is output as a reference signal. A configuration example of this method is shown in FIG. Preformatted signals such as sector marks, VFO, and address marks are described in each preformatted area on the track. Reference numeral 25 is a preformat signal detecting means, which is 2
6 receives the pre-formatted signal, and the time t at which it occurs
Reference signal generating means for outputting 0 and the reproduction cycle T1 as reference signals.

Next, the operation of the prediction window signal generating means 16 will be described. Prediction window signal generation means 1
Reference numeral 6 predicts the irradiation timing by using the reference signal during the access operation. An example of the prediction method is shown in FIG. The prediction window signal generation means 16 reads from the reference signal the time t0 at which the light spot immediately before the track follow operation moves to the access operation irradiates the preformat area, and the prediction window signal is obtained for each pass cycle T1 of the preformat area indicated by the reference signal. Set 17 to H level. The width ΔT of the H level of the prediction window signal is appropriately determined by the time during which the light spot passes through the preformat area.

The moving speed detecting means 18 of the optical pickup calculates the reciprocal of the periodic signal to generate the moving speed signal of the optical pickup as in the conventional example. However, when the prediction window signal is received, the moving speed signal of the optical pickup is received. To correct. An example of the correction method will be described with reference to FIG. FIG. 6 shows a process of detecting the optical pickup moving speed in the present embodiment in the case where deceleration is performed at a constant acceleration in the radial direction of the disk when the cross-track signal is affected by the preformatted area. 6A is a track crossing signal, FIG. 6B is a trigger signal for period detection, and FIG.
6C shows the predicted window signal, the solid line in FIG. 6D shows the moving speed signal of the optical pickup, and the dotted line in FIG. 6D shows the actual moving speed of the optical pickup. Normally, the cycle of the track crossing signal is detected by the trigger signal as in part A,
The reciprocal thereof is obtained and used as the moving speed signal of the optical pickup. However, the correction is performed in the B section from the rise of the prediction window signal to the time when normal speed detection is possible. For example, if the deceleration of the pickup is estimated from the moving velocity detection values of the previous and the previous two times, and the moving velocity of the optical pickup is estimated from the deceleration, the solid line in FIG. 6D is obtained. A method of estimating the moving speed is shown in FIG. The deceleration a of the optical pickup is measured by the following equation from the speed detection values v2, v3 and Δt.

Using a = (v3-v2) / Δta, the estimated value v of the moving speed is obtained by v = v3 + at. Here, t is the elapsed time from time t0 when the prediction window signal rises.

As described above, according to this embodiment, the reference signal generating means for indicating the timing at which the light spot irradiates the preformatted area and the predictive window signal generating means for indicating the timing at which the light spot irradiates the preformatted area at the time of access. To compensate the influence of the track crossing signal disturbed by the preformatted area on the optical pickup moving speed signal.

[0018]

As is apparent from the above embodiments, according to the present invention, when the track crossing signal is disturbed due to the preformatted area, the optical pickup moving speed detection is corrected, so that the good optical pickup moving speed detection is performed. Therefore, a highly accurate and stable speed control can be obtained, and as a result, it is possible to provide a moving speed detecting device for an optical pickup that can realize a control device for an optical pickup that is resistant to disturbance and has a high access speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a moving speed detection device for an optical pickup according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a reference signal generation method in the same device.

FIG. 3 is an explanatory diagram of a reference signal generation process in the device.

FIG. 4 is a schematic configuration diagram of another reference signal generation method in the device.

FIG. 5 is an explanatory diagram of a prediction window signal generation process in the same device.

FIG. 6 is an explanatory diagram of a process of detecting the moving speed of the optical pickup in the same apparatus. (A) Track crossing signal (b) Trigger signal (c) Prediction window signal (d) Optical pickup moving speed signal and actual moving speed

FIG. 7 is an explanatory diagram of a moving speed estimated value generation process in the same apparatus.

FIG. 8 is a block diagram showing a configuration of an access control system of a conventional optical pickup.

FIG. 9 is an explanatory diagram of a conventional moving speed detection process of an optical pickup when there is no influence of a preformat area. (A) Track crossing signal (b) Trigger signal (c) Optical pickup moving speed signal and actual movement speed

FIG. 10 is an explanatory view of a conventional moving speed detection process of an optical pickup when there is an influence of a pre-formatted area. (A) Track crossing signal (b) Trigger signal (c) Optical pickup moving speed signal and actual movement speed

[Explanation of symbols]

 1 Optical Disc 4 Optical Pickup 6 Track Crossing Signal Detection Means 8 Periodic Signal Generation Means 14 Reference Signal Generation Means 16 Prediction Window Signal Generation Means 18 Optical Pickup Moving Speed Detection Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Sakata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. An optical disc having a preformatted region having a light reflectance different from that of a data region on a track, an optical system for irradiating a light spot on the optical disc and detecting a signal, and the optical system in a substantially radial direction of the disc. An optical pickup including a drivable optical pickup actuator,
Means for generating a reference signal indicating the timing at which the light spot irradiates the preformatted area during the track following operation, and a prediction window for estimating the timing at which the light spot irradiates the preformatted area during the access operation. Means for generating a signal using the reference signal; means for detecting a track crossing signal that appears when the light spot crosses a track;
Means for measuring the period of the track crossing signal and generating a periodic signal, and generating a moving speed signal of the optical pickup from the periodic signal, and receiving the prediction window signal and correcting the moving speed signal of the optical pickup. And a moving speed detecting device for an optical pickup.