JPH0449173B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the recording of information signals by an optical head from a disk, such as an optical video disk, in which the information signals are recorded on a spiral track so that they can be read optically. The present invention relates to a head feed control device for an optical disc player for playback, in particular for moving the head in the radial direction of the disc by following the track.

BACKGROUND TECHNOLOGY AND PROBLEMS In optical discs such as optical video discs, information signals are recorded in a spiral track formed by an array of pits, and the player uses a light beam from an optical head to record information signals. The information signals are read from the tracks of the disk. In this case, in order to make the light beam of the head follow the track, for example, in the head, the light beam from the light source is reflected by a tracking mirror and incident on the disk, and the light beam is directed to the disk. The deviation of the incident position from the track is detected, and based on the detected signal,
The inclination of the mirror is controlled to move the incident position of the light beam onto the disk in the radial direction of the disk. However, the variable range of the tilt of this tracking mirror is relatively small, and simply changing the mirror tilt cannot make the head light beam follow the track over the entire area from the inner circumference to the outer circumference of the disk. I can't. Therefore, the head itself, which has a mirror and a mirror drive device that changes the inclination of the mirror, is made to move in the radial direction of the disk, and based on the DC component of the signal given to the mirror drive device, this DC component becomes zero. The radial advance of the disk of the head is controlled in this way.

FIG. 1 shows an example of a conventional head feed control device for an optical disc player, in which information signals are recorded on a disc 10 in the form of a spiral track formed by an arrangement of pits, and an optical head 20 is recorded on the disc 10.
, a light beam from a laser light source passes through various optical components to a tracking mirror 21.
The light beam enters the disk 10 and is reflected by the focusing lens 22, and is focused by the focusing lens 22 and enters the disk 10.
and a mirror drive device 24 which is configured to reach the photodetector 23 via various optical components, and which changes the inclination of the mirror 21 to move the incident position of the light beam onto the disk 10 in the radial direction of the disk 10.
is provided. Also, the light beam disk 1
In order to detect a so-called tracking error, which is a deviation in the position of incidence on the 0 track, two light beams other than the light beam for reading the information signal are incident on the disk 10 (not shown). The light beam reflected by the photodetector 25
and 26. Then, the outputs of the photodetectors 25 and 26 are subtracted by a subtraction circuit 31, thereby producing a so-called tracking error signal, which is a signal indicating the deviation of the incident position of the light beam for reading the information signal onto the disk 10 with respect to the track. This tracking error signal is supplied to the mirror drive device 24 via the phase compensation circuit 32 and the amplifier circuit 33, thereby forming a servo loop for tracking control.

A thread 41 is attached to the optical head 20. For example, the thread 41 is screwed onto a shaft 42 extending in the radial direction of the disk 10, and a motor 43 is connected to the shaft 42 to move the head 20 in a radial direction of the disk 10. A head feeding mechanism is configured to move the head in the direction. Then, the tracking error signal given to the mirror drive device 24 is supplied to the low-pass filter 51, and the DC component voltage V _D of the tracking error signal is taken out _.
is supplied to the motor 43 via the amplifier circuit 53, forming a servo loop for head feed control.

If the DC component of the tracking error signal given to the mirror drive device 24 is zero, the mirror 2
1 is normally tilted so that the light beam passes near the optical axis of the focusing lens 22 and enters the disk 10 as shown by the solid line arrow as shown by the solid line 21a in FIG. - The variable range of the inclination of the mirror 21 within a range in which the light beam due to the alternating current component of the error signal does not deviate from the field of view of the focusing lens 22, that is, the range in which the light beam can follow the track is maximized by tracking control. On the other hand, if the DC component of the tracking error signal given to the mirror drive device 24 is not zero,
As shown by the solid line 21b in FIG. 3, the mirror 21 normally causes the light beam to enter the disk 10 through a point shifted from the optical axis of the focusing lens 22 toward the outer circumference of the disk 10 as indicated by the solid arrow. Or, although not shown, the light beam can be tilted in the opposite direction by the focusing lens 2.
In this case, depending on the steady inclination, the AC component of the tracking error signal is The range in which the inclination of the mirror 21 can be varied within a range in which the light beam does not deviate from the field of view of the focusing lens 22, that is, the range in which the light beam can follow a track due to tracking control becomes small. In the conventional head feed control device shown in FIG. 1, the DC component of the tracking error signal applied to the mirror drive device 24, that is, the voltage V _D of the output of the low-pass filter 51 becomes zero.
The movement of the head 20 is controlled so that the mirror 21 is normally tilted so that the light beam passes near the optical axis of the focusing lens 22 and enters the disk 10 as shown in the figure.

However, because it is difficult to make the DC gain of the servo loop for head feed control sufficiently large, the DC component of the tracking error signal cannot be reduced to zero, and the mirror 21 of the head 20 cannot match the state shown in the figure. It ends up being sent slightly tilted. However, this may occur during constant speed playback in the forward direction in which the head 20 is moved so that the light beam traces a spiral track directly from the inner circumference to the outer circumference of the disk 10, or conversely when the light beam traces a spiral track from the inner circumference to the outer circumference of the disk 10. Move the head 2 to trace the track from the outer periphery of the disk 10 to the inner periphery.
During constant speed playback in the reverse direction in which zero is moved, the direct current component of the tracking error signal is minute and the mirror 21 is only slightly tilted relative to the state shown in the figure, so it does not pose much of a problem. However, for example, in the case of an optical video disc player,
In addition to the constant speed playback mode, the light beam can be used for one round of the track 11 at radial positions P _A and P _B , which are 180 degrees apart from each other, where the vertical blanking period portion of the video signal is recorded, as shown by the arrow 12 in FIG. A high-speed playback mode such as forward triple-speed playback in which the head 20 is moved to trap-jump outward and trace is selectively available. When the DC component of the error signal becomes too large to ignore, mirror 2
1, the light beam is tilted significantly so that it enters the disk 10 through a point considerably deviated from the optical axis of the focusing lens 22.

Figure 5 shows this reproduction mode and the mirror drive device 24.
This shows the relationship between the voltage V _D of _the DC component _of the tracking error signal given to
becomes a very small value V _F1 , and the mirror 21 normally tilts only slightly in the clockwise direction with respect to the state indicated by the solid line 21a in FIG. Assuming that at time t ₁ the forward constant speed playback is switched to the forward triple speed playback,
During triple speed playback in the forward direction, the voltage V _D becomes a large value V _F3 with the same polarity as during constant speed playback in the forward direction, and the light beam is moved from the optical axis of the focusing lens 22 to the outer peripheral side of the disk 10. The mirror 21 rotates the third mirror so that the light enters the disk 10 through the shifted point.
As shown by the solid line 21b in the figure, the solid line 21a in FIG.
It becomes tilted significantly clockwise compared to the state of . Furthermore, assuming that at time t ₂ the forward playback is switched from 3x playback to constant speed playback in the reverse direction, during constant speed playback in the reverse direction, the voltage V _D has a slight polarity that is opposite to that during playback in the forward direction. The value becomes −V _R1 , and mirror 2
1 is steadily tilted only slightly in the counterclockwise direction with respect to the state indicated by the solid line 21a in FIG. moreover,
Assuming that at time _t3 the constant speed playback in the reverse direction is switched to the triple speed playback in the reverse direction, during triple speed playback in the reverse direction, the voltage V _D has the same large value - of the polarity as during constant speed playback in the reverse direction. V _R3 , and the mirror 21 is placed in the state shown by the solid line 21a in FIG. On the other hand, it will tilt significantly counterclockwise.

In this way, in the conventional head feed control device, especially in the case of high-speed reproduction, the voltage of the DC component of the tracking error signal applied to the mirror drive device 24 is
When V _D reaches a size that cannot be ignored, the head 20 is sent with the mirror 21 tilted greatly so that the light beam enters the disk 10 through a point considerably deviated from the optical axis of the focusing lens 22. - The variable range of the inclination of the mirror 21 within the range in which the light beam due to the alternating current component of the error signal does not deviate from the field of view of the focusing lens 22, that is, the range in which the light beam can follow the track due to tracking control becomes small. There is a disadvantage that it is difficult to make the beam accurately follow the track and perform stable reproduction.

Purpose of the Invention In view of this, the present invention provides a system in which, regardless of the playback mode, the tracking mirror is at an optimal inclination so that the light beam passes near the optical axis of the focusing lens and enters the disk. The head is fed forward to ensure stable playback at all times.

Summary of the Invention In the present invention, a voltage of a target value according to the reproduction mode is added to the voltage of the DC component of the tracking error signal given to the mirror drive device, and the added voltage is used to drive the head feeding motor. In this case, the target value voltage is such that the DC component voltage of the tracking error signal is at a constant value of zero or close to zero regardless of the playback mode.
Change depending on the playback mode.

Embodiment FIG. 6 shows an example of the head feed control device of the present invention, in which the output voltage of the low-pass filter 51, that is, the DC component voltage V _D of the tracking error signal applied to the mirror drive device 24 is supplied to the adder circuit 52. The added voltage V _C is added to the target voltage _V A loop is constructed. The voltage generation circuit 60 includes a power source that can obtain different voltages corresponding to constant speed playback in the forward direction, triple speed playback in the forward direction, constant speed playback in the reverse direction, and triple speed playback in the reverse direction, and a power source that generates the respective voltages. It has switches S _F1 , S _F3 , S _R1 and S _R3 to take out the operation part 70 .
By operating any of the operation buttons P _F1 , P _F3 , P _R1 and P _R3 for forward constant speed playback, forward playback at 3x speed, constant speed playback in the reverse direction, and triple speed playback in the reverse direction. , the corresponding switches S _F1 , S _F3 , S _R1 and S _R3 are turned on and a voltage corresponding to the regeneration mode is taken out, and this voltage is applied to the resistor R ₁ through the capacitor C ₂ and the resistor R ₂ . By passing the series circuit through a transient compensation circuit 61 connected in parallel, the voltage V _X is set to a target value.

In the conventional device shown in FIG. 1, the voltage of the target value is equivalently zero, and the voltage V _D of the output of the low-pass filter 51 with respect to the voltage of the target value is as shown in FIG. 7A. , when playing at constant speed in the forward direction.
The deviation is by V _F1 , by V _F3 during triple speed playback in the forward direction, by -V _R1 during constant speed playback in the reverse direction, and by -V _R3 during triple speed playback in the reverse direction. Therefore _, in response to this deviation, the target value of the voltage _V -V _F3 for 3x speed playback, and -V F3 for constant speed playback in the reverse direction.
to V _R1 , and to V _R3 when playing at 3x speed in the reverse direction.
You can set them respectively.

According to this, the voltage of the DC component of the tracking error signal applied to the mirror drive device 24, that is, the voltage V _D of the output of the low-pass filter 51, is the voltage of the target value V _X =- during constant speed reproduction in the forward direction.
Only V _F1 against V _F1 , only V _F3 against target value voltage V _X = -V _F3 during forward 3x speed playback,
During constant speed playback in the reverse direction, the target value voltage V _X =
The difference is -V _R1 with respect to V _R1 , and by _{-V R3 with} respect to the target value voltage _V It becomes zero regardless of the playback mode. Therefore,
Regardless of the playback mode, the mirror 21 is set at an optimal inclination, as shown by the solid line 21a in FIG. In this state, the head 20 is fed.

Effects of the Invention According to the present invention, the DC component voltage of the tracking error signal applied to the mirror drive device 24
A _target value _of voltage _V Regardless of the playback mode, _the target value voltage _V , a tracking mirror 21 and a focusing lens 22 for the light beam.
The head 20 is sent in an optimally tilted state so that the light passes near the optical axis of the head and enters the disk 10.
Stable playback is always achieved.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a conventional head feed control device, Figures 2 and 3 are diagrams for explaining the state of tilt of a tracking mirror, and Figure 4 is a diagram showing the order of an optical video disc. Figure 5 is a diagram to explain the state of the light beam trace in the case of triple speed reproduction in the direction, Figure 5 is a diagram to explain the operation in various reproduction modes in the apparatus of Figure 1, and Figure 6 is FIG. 7 is a diagram showing an example of the head feed control device of the invention, and is a diagram for explaining its operation in various playback modes. In the figure, 10 is a disk, 20 is an optical head, 2
1 is a tracking mirror, 24 is a mirror drive device, 43 is a head feed motor, 51 is a low-pass filter, and 60 is a voltage generating circuit.

Claims (1)

[Claims] 1 A mirror that reflects a light beam for reading an information signal from a light source and makes it incident on a disk recorded on a spiral track so that the information signal can be optically read; an optical head having a mirror drive device that changes the inclination of the mirror in order to move the incident position of the light beam onto the disk in the radial direction of the disk based on a signal indicating a deviation of the incident position with respect to the track; A low-pass filter that extracts the DC voltage of the signal applied to the mirror drive device, a voltage generation circuit that generates a voltage according to the playback mode, and an addition of the output voltage of the low-pass filter and the voltage obtained from the voltage generation circuit. and a head feeding mechanism that moves the optical head in the radial direction of the disk by the applied voltage, and is obtained from the voltage generating circuit so that the output voltage of the low-pass filter becomes a predetermined constant value regardless of the reproduction mode. An optical disc player head feed control device in which the voltage is varied depending on the playback mode.