JPH0341627A - Tracking control method - Google Patents

Abstract

PURPOSE:To form information in the shape of a track so that a track pitch can be fixed by similarly displacing both beams in a tracking direction corresponding to a tracking error signal, which shows tracking error between the beam for monitor and the track, and controlling the position of the main beam in the tracking direction. CONSTITUTION:An output from a sensor, which receives the beam for recording, is supplied to a focus error detecting circuit 6 and an output from a sensor, which worked to a focus error signal in this circuit 6. Further, an output from a sensor, which receives the beam for monitor, is supplied to a tracking error detecting circuit 7 and worked to the tracking error signal in this circuit 7. The two error signals, which are prepared in such a way, are supplied to an objective lens actuator driving circuit 4. The main beam is displaced in a tracking correcting direction together with the beam for monitor corresponding to the tracking error of the beam for monitor. Thus, even when a track for recording is not formed in a medium beforehand, the recording track can be formed with the fixed track pitch.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to a method for controlling tracking of a light beam.

(B) Prior Art A conventionally known tracking control method is disclosed in Japanese Patent Publication No. 62-7608 (G11B7109), for example. Such a tracking control method involves irradiating a beam onto the edge of a track and creating a tracking error signal in accordance with the intensity of the beam reflected from the edge.

Also, as another tracking control method, for example, Japanese Patent Application Laid-open No. 49
There is a tracking control method disclosed in Publication No. 50954 (104GO>). Such a tracking control method is the so-called three-beam method, in which first-order diffracted light formed through a diffraction grating is irradiated to the edge portion of the track, respectively. A tracking error signal is created by comparing the intensities of the reflected beams.

Furthermore, other conventionally known tracking control methods include the Bubbles method, the Heterodyne method, and the Obring method.

However, in each of these methods, a tracking error signal is created based on the state of the reflected beam when the beam is irradiated onto the track, so when creating the tracking error signal, the track is formed on the medium in advance. There is a need. Therefore, a playback-only player,
Alternatively, although it is suitable for a device that writes information on tracks previously formed on a medium, it cannot be used for a device that writes information on a medium that has no tracks formed at all.

Incidentally, in recent years, research has been carried out on devices for recording information on optical tape by a helical scanning method (for example, see Japanese Patent Application Laid-open No. 57-64333!'!a). With this optical tape, it is difficult to form diagonal recording tracks in advance on the optical tape with high accuracy on the order of microns. On the other hand, if tracking control of the recording beam is not performed during recording, the distance between adjacent recorded tracks will not be constant due to vibrations of the rotating drum or tape, and in severe cases, adjacent tracks will overlap. , there is a risk that playback may not be performed properly.

(c) Problems to be Solved by the Invention Therefore, the present invention provides a tracking control method that can form information in a triangular shape so that the track pinch is constant even if no recording tracks are previously formed on the medium. Our first objective is to provide a method for tracking information, and we also propose a new tracking control method that can be applied to erasing information, etc.

(d) Means for Solving the Problems In view of the above-mentioned problems, the present invention aims to irradiate a medium with a monitor beam and a main beam aligned in the tracking direction, and to detect tracking errors that indicate a track misalignment between the monitor beam and the track. The first feature is that both beams are similarly displaced in the trunking direction in response to a signal, thereby controlling the position of the main beam in the tracking direction. Both beams are irradiated onto the medium so as to lead in the tracking direction.
A second feature is that both the beams are similarly displaced in the tracking direction in response to a tracking error signal indicating a track deviation between the track already recorded on the medium by the recording beam and the monitoring beam. .

Furthermore, both beams are irradiated onto the medium so that the monitoring beam precedes the erasing beam in the tracking direction,
A third feature is that both the beams are similarly displaced in the tracking direction in response to a tracking error signal indicating a track deviation between the monitoring beam and the track.

(E) According to the first feature of the action, the main beam is shifted along with the monitor beat according to the tracking deviation of the monitor beam.
1 is displaced in the king correction direction.

Furthermore, according to the second feature, since the recording beam is displaced together with the monitoring beam in the tracking correction direction in accordance with the positional deviation between the monitoring beam and the recording track, the distance between the already recorded track and the current recording track is becomes constant, and therefore the trunk pitch of the recording track becomes constant.

Furthermore, according to the third feature, since the erasing beam is displaced in the tracking correction direction together with the monitoring beam in accordance with the positional deviation between the monitoring beam and the recording track, even if the track pitch of the recording track is constant. For example, by appropriately setting the distance between the two beams, the erasing beam can always be positioned on the recording track.

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the actuator and control block of this embodiment. In the figure, (1) is a cylindrical rotating drum, inside which a pickup (2) is arranged. The pickup (2) includes a semiconductor laser (201), a collimator lens (202), a half prism (203), an objective lens (204), and an objective lens drive actuator (202).
05), converging lens (206) and photodetector (207)
It becomes more. Here, the semiconductor laser (201) has two light emitting arrays, and each array has a semiconductor laser drive circuit (
3). That is, in the recording mode, one array is driven to output a modulated beam (recording beam) according to the recording data signal, and the other array is driven to output a beam (monitoring beam) having a predetermined intensity level. )
is driven to output. Note that the intensity of the monitor width beam is much smaller than the intensity of the recording beam.

Further, the objective lens drive actuator (205) drives the objective lens (204) in the focusing direction and the tracking direction in response to a signal from the objective lens actuator drive circuit (4).

Further, as a photodetector (207), two sensors are prepared to receive reflected components of the beams from the two arrays from the optical tape (5).

Of these, the output from the sensor that receives the recording beam is supplied to a focus error detection circuit (6), where it is processed into a focus error signal.

Furthermore, the output from the sensor that receives the monitoring beam is supplied to a tracking error detection circuit (7), where it is processed into a tracking error signal. It should be noted that various conventionally known methods can be used to create the seven-occasion error signal and the tracking error signal, and the explanation thereof will be omitted here as it is not the gist of the invention.

The focus error signal and tracking error signal created in this way are supplied to the objective lens actuator drive circuit (4). The objective lens actuator drive circuit (4) drives the objective lens (204) in the 7-orcus direction and the tracking direction in response to these two error signals, thereby directing the recording beam and the monitoring beam onto the optical tape (5). converge to a predetermined position.

The optical tape (5) is wound diagonally around the outer periphery of the rotating drum (1) and is guided by the rollers (8) (8) and transported in the horizontal direction, and the rotating drum (1) is The optical tape (5) is rotated in the same direction as the tape transport direction, whereby the optical tape (5) is obliquely scanned by the recording beam and the monitoring beam.

FIG. 2 is a diagram showing the scanning operation of the optical tape by such a beam. In the figure, (B1) is the spot of the recording beam (recording spora l-'), and (B2) is the spot of the monitoring beam (monitoring spot). The recording spot (B1) and the monitoring spot (B2) are moved in the directions of arrows B and C, respectively, by the rotation of the rotating drum (1). Further, the optical tape (5) is transported in the direction of arrow A.

In this embodiment, the track (T) formed by the recording spot y ) (Bl) is then scanned by the monitoring spot (B2) after one revolution of the rotating drum (1).Such a state is Adjust the transport speed of the optical tape (5), the rotation speed of the rotating drum (1), and the distance between the recording spot (B1) and the monitoring spot (B2) in the direction perpendicular to the track (T) (tracking direction). This can be achieved freely.

The distance in the tracking direction between the two spots (Bl) (82) can be adjusted by changing the distance between the two emission arrays in the semiconductor laser (201). ) can also be adjusted by changing the angle between the straight line and the trag (T). The latter adjustment can be achieved by rotating the semiconductor laser (201) about its optical axis.

By the way, as mentioned above, the monitoring spot (B2) is used to detect the deviation tL with respect to the track (T) based on the state of the reflected beam of the monitoring beam from the optical tape (5), but this deviation is caused by a tracking error. Correction is made by driving the objective lens (204) in the tracking direction in accordance with the tracking error signal from the detection circuit (7). Therefore, the monitoring spot (B2) constantly scans the track (T).

Now, when the objective lens (204) is moved to correct the tracking deviation of the monitor spot (B2), since the recording beam is incident on this objective lens (204), the recording beam The spot (Bl) is also displaced in the same manner as the monitor subo-soto (B2). Therefore, the distance in the tracking direction between the recording spot (Bl) and the monitoring spot (B2) does not change. Therefore, if tracking control of the monitor spot (B2) to the track (T) is performed well, the recording spot (B2)
In step 1), the optical tape (5) is scanned at a certain distance from the previously recorded track. That is, the tracks (T) can be sequentially formed while keeping the track pitch of the recording tracks (T) constant. Note that the first track to be recorded is formed on the optical tape depending on the mechanical accuracy of the track since there is no previously recorded track. As described above, according to this embodiment, it is possible to sequentially form tracks at a constant track pitch without forming recording tracks on an optical tape in advance.

Further, as another embodiment, multi-track recording of information can be performed by increasing the number of light emitting arrays of semiconductor lasers (21) 1). FIG. 3 shows an example in which a semiconductor laser is provided with four light emitting arrays, one beam for monitoring and three beams for recording. In this case, adjust the tape transport speed and rotation speed of the rotating drum as described above so that the monitoring spot (B2) scans the rightmost track in FIG. 3 with one rotation of the rotating drum. good. Furthermore, if the distance between the monitoring spot and the recording groove is made larger than the distance between the recording spots, the tracks (T) can be separated into each track block as shown in FIG.

Furthermore, the tracking control method according to the present invention is also applicable to erasing recorded tracks. That is, by arranging the erasing spot (B3) and the monitoring spot (B2) as shown in FIG. 5, the tracks (T) can be sequentially erased.

Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, as a means for emitting a plurality of beams, a plurality of light emitting arrays are disposed on a semiconductor laser, but a single laser beam may be divided into a plurality of beams by a diffraction grating. However, in this case, since the monitoring beam is also modulated according to the data signal to be recorded, it becomes difficult to create a tracking error signal depending on the state of the monitoring beam reflected from the optical tape. Therefore, during recording, it is better to arrange a plurality of light emitting arrays on a semiconductor laser as described above or to prepare a plurality of beams using a plurality of semiconductor lasers.

Furthermore, it goes without saying that the tracking control method of the present invention can be applied not only to optical tape devices but also to optical disk devices and the like.

(G) Effects of the Invention As described above, according to the present invention, recording tracks can be formed satisfactorily with a constant track pitch without having to separately form recording tracks on a medium in advance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining a state in which a recording track is formed according to the same embodiment, and FIG. 3 is a diagram illustrating a state in which a recording track is formed according to another embodiment. 4 is a diagram for explaining a state in which a recording track is formed according to another embodiment, and FIG. 5 is a diagram for explaining a state in which a recording track is formed according to another embodiment. FIG. 5 is a diagram showing a track when the present invention is applied to erase a recording track FIG. (201)...Semiconductor laser, (204)...Objective lens, (205)...Objective lens drive actuator, (7)...Tracking error detection circuit, (B1
)...Recording spot, (B2>...Monitor m spot.

Claims (3)

[Claims] (1) A monitor beam and a main beam are aligned in the tracking direction and irradiated onto the medium, and both beams are similarly displaced in the tracking direction in response to a tracking error signal indicating a track deviation between the monitor beam and the track. A tracking control method characterized in that the position of the main beam in the tracking direction is controlled. (2) Both beams are irradiated onto the medium so that the recording beam precedes the monitoring beam in the tracking direction,
A tracking control method comprising displacing both beams in the same way in the tracking direction in response to a tracking error signal indicating a track deviation between a track already recorded on a medium by the recording beam and the monitoring beam. (3) Both beams are irradiated onto the medium so that the monitoring beam precedes the erasing beam in the tracking direction,
A tracking control method characterized in that both the beams are similarly displaced in the tracking direction in response to a tracking error signal indicating a track deviation between the monitor beam and the track.