JPH09231588A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably record/reproduce information by controlling an objective lens by using an optimum control offset in a groove part and a land part of a medium. SOLUTION: When the changeover instruction between a land L and a groove G is outputted from a CPU 35 to an L/G changeover circuit 34, a servo controller 33 changes the control so as to irradiate the instructed land L and groove G of a medium with a light spot. At the same time, an offset changeover part 32 is operated by an offset changeover signal, the offset values of the land L/groove G are changed over and a control signal calculated by the optimum control offset value is sent to the servo controller 33. Consequently, the control of the objective lens by the optimum control offset value is performed in the groove part and the land part and the stable information reproduction/recording is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive for reproducing a recording signal or recording information in both a groove portion and a land portion of a medium, or for reproducing a recording signal of each layer in a single-sided reading type two-layer medium. The present invention relates to an optical disc drive that records information. Further, the present invention relates to an optical pickup for a DVD drive device and an MO drive.

[0002]

2. Description of the Related Art As one method for realizing a high density of a disk, by recording on both a groove (guide groove: guide groove) and a land (between guide grooves: between guide grooves), a track density is increased. A method has been proposed in which the density is doubled compared with the conventional method. If the depth of the groove is set to a predetermined value, the crosstalk between the information mark recorded on the land and the information mark recorded on the adjacent groove becomes small, and high density recording becomes possible (OPTRO).
NICS 1994. No. 5, p. 122 to p. 126, "High Density of Phase Change Optical Disk by Land & Groove Recording").

As described above, media such as a high density optical disk capable of recording information on both the groove portion and the land portion have been conventionally known. In the case of such a medium, since the groove portion and the land portion have information,
The objective lens needs to illuminate both of them. Various types of optical disk drives are used for reproducing a recording signal or recording information using such a medium. In an optical disc drive that reproduces a recording signal or records information in both the groove portion and the land portion of this medium, when recording / reproducing information, the optical spot emitted from the objective lens of the optical pickup is set to a predetermined value on the medium. The position is illuminated. Here, the conventional technique will be sequentially described with reference to the drawings.

FIG. 7 is a perspective view showing a partially enlarged structure of a main portion of a medium having recorded information in both the groove portion and the land portion. In the figure, 1 is a medium (recording medium), 1a is a substrate, 1b is a recording film, G is a groove track, L is a land track, M is a recording mark,
p indicates the track pitch, and arrow A indicates the incident direction of the laser light.

As shown in FIG. 7, a groove track G and a land track L are formed on one surface of the medium 1, and both the groove portion and the land portion are formed.
Information as indicated by the recording mark M can be recorded. The medium 1 has a recording film 1b on a substrate 1a on which groove tracks G and land tracks L are formed.
Is provided, and information is recorded / reproduced by laser light from the direction indicated by arrow A. Further, the distance between the groove track G and the land track L, that is,
The track pitch p is constant. And record information
At the time of reproduction, the laser light focused by the objective lens from the direction of arrow A is applied to a predetermined position on the groove track G or the land track L. This laser beam
It is emitted from the optical pickup.

FIG. 8 is a perspective view showing the structure of a general optical pickup. In the figure, 2 is an optical pickup,
3 is an objective lens, 4 is an actuator, 5 is a seek shaft, 6 is a seek motor, 7 is a first gear, 8 is a second gear group, and 9 is an engaging tooth formed on the optical pickup 2.

An objective lens 3 is attached to the optical pickup 2, and the objective lens 3 is supported by an actuator 4. The objective lens 3 has a function of condensing a light beam from a semiconductor laser (not shown) on the recording surface of the medium in order to reproduce and record information. Therefore, the objective lens 3 needs to be positioned in a predetermined relationship with respect to the medium, and the actuator 4
Is moved in the tracking direction (radial direction) and the focus direction by and stopped at a predetermined position. The movement control in the tracking direction and the focus direction is performed by an electric tracking control signal and a focus control signal in which the reflected light from the medium is detected by the optical pickup 2 and photoelectrically converted by the light receiving element. The positional relationship between the objective lens 3 and the medium 1 will be described with reference to FIG.

FIG. 9 is a side view showing the relationship between a medium having recording information in the groove portion and the land portion and the objective lens. Reference numerals in the drawing are the same as those in FIGS. 7 and 8, 1c is a protective film of the medium 1, 1d is a recording surface of the medium 1, arrow B is a radial direction, arrow C is a focusing direction, arrow D is a tracking direction, and LB is Indicates laser light.

As shown in the side view of FIG. 9, the objective lens 3 is arranged on one side of the medium 6 and is moved in the radial direction (lateral direction in the figure) indicated by the arrow B, and the focusing indicated by the arrow C. Direction (up and down direction in the figure). When moving in the radial direction, the seek motor 6 moves along the seek shaft 5 in FIG. The movement in the focusing direction is performed by the actuator 4. The movement in the tracking direction is also performed by the actuator 4.

As described above, the tracking control signal and the focus control signal are used for the movement control in the tracking direction and the focus direction. However, these control signals have an offset due to an optical offset such as an assembly of the optical pickup 2 and a variation in optical performance, an offset of a circuit system, and the like. Therefore, in order to perform control with high accuracy, it is necessary to cancel these offsets.

FIG. 10 is a diagram for explaining an offset in tracking control. Reference numerals in the figure are the same as those in FIG. 7, Tr is a tracking error signal, ΔTr is a tracking control offset amount, and E is accurate (to be corrected).
Indicates the control position.

In the conventional tracking control, the tracking error signal Tr is detected and, as shown in FIG.
The objective lens is controlled so as to coincide with the center positions of the groove G and the land L of the medium 1. However, if the tracking control offset amount ΔTr is present for various reasons as described above, the tracking position at which the tracking error signal Tr becomes “0” and the control position E to be corrected do not match. As a result, the objective lens cannot be moved to the accurate control position E by the tracking control that controls the radial direction of the medium 1. Such a problem also applies to the focus control that controls the distance between the objective lens and the medium 1.

FIG. 11 is a diagram for explaining an offset in focus control. The reference numerals in the figure are the same as those in FIG. 9, Fo is a focus error signal, ΔFo is a focus control offset amount, and F is an accurate (corrected) control position.

As shown in FIG. 11, even in the focus control by the focus error signal Fo, the objective lens 3 cannot be moved to the accurate control position F by the focus control offset amount ΔFo. Further, as one conventional method for canceling such an offset amount (ΔTr or ΔFo), a circuit as shown in FIG. 12 is used. Note that this circuit is adopted not for the medium 1 capable of recording information on both the groove portion and the land portion but for the medium capable of recording information on only one of the groove portion and the land portion. is there.

FIG. 12 is a diagram showing a configuration for offset canceling a medium in which recording is performed only on one of the groove portion and the land portion. (1) is a perspective view showing the structure in the vicinity of the objective lens, and (2) is An offset cancel circuit for tracking control, and (3) is an offset cancel circuit for focus control. In the figure, 11 is an optical head,
12 is an objective lens, 13 is a tracking coil, 14
Is a focusing coil, 15 is a comparator, 16 is a tracking controller, 17 is a comparator, and 18 is a focus controller.

As shown in FIG. 12 (1), a tracking coil 13 and a focusing coil 14 are arranged close to the objective lens 12. Then, as shown in FIG. 12 (2), when canceling the offset of the tracking control, the comparator 15 compares the tracking error signal Tr generated by detecting the reflected light from the medium with the pickup and the offset amount ΔTr. Give to. The comparison output from the comparator 15 is used as a tracking controller 16
The offset of the tracking control is canceled by applying the offset to the tracking coil 13 via.

The same applies to the case of canceling the focus control offset. As shown in FIG. 12 (3), the focus error signal Fo and the offset amount ΔFo are given to the comparator 17, and the comparison output is given to the focus controller 18.
Is output to the focusing coil 14 via. This figure 1
The offset canceling method as shown in 2 (1) to (3) is conventionally known.

A single-sided reading type double-layer medium is also known. Even in an optical disc drive that reproduces a recording signal or records information by using this one-sided read type two-layer medium, when recording / reproducing information, the groove portion and the land portion shown in FIG. Similar to the case of the medium 1 having recorded information in both, the light spot emitted from the objective lens of the optical pickup is irradiated to a predetermined position of the medium.

FIG. 13 is a view for explaining the position of the objective lens at the time of reading each recording layer in the one-sided reading type two-layer medium. In the figure, 21 is a single-sided reading type two-layer medium, 21a is a substrate, 22 is the position of the objective lens when reading the layer 0, and 23 is the position of the objective lens when reading the layer 1.

As shown in FIG. 13, the one-sided reading type two-layer medium 21 is provided with two recording layers of layer 0 and layer 1. The distance between the two recording layers is about 5
At 0 μm, the thickness of the substrate 21a is about 0.6 mm. Therefore, position 2 of the objective lens when reading layer 0
2 and the position 23 of the objective lens when reading the layer 1 are different. The amount of offset generated in this case differs depending on the layers 0 and 1 that irradiate the laser beam. Therefore, as in the case of the medium 1 having recorded information in both the groove portion and the land portion, the objective lens needs to be positioned in a predetermined positional relationship with the two-layer medium 21, and tracking for controlling the radial direction of the medium is required. Focus control for controlling the control and the distance to the medium is performed.

[0021]

First, as shown in FIG. 7 as a conventional technique, in the case of the medium 1 having recorded information in both the groove portion and the land portion, the offset amount is laser light irradiation. A difference occurs depending on the position to be applied, that is, the groove G or the land L. The cause of the difference in the offset amount is that the groove shape of the medium 1 is different, the diffraction pattern of the reflected light is different between the groove G and the land L, and the influence of an optical assembling error is changed. is there.

FIG. 14 is a diagram for explaining the phase shift that occurs in the tracking error signal. Reference numerals in FIG.
Is the ideal tracking error signal,
Indicates a tracking error signal with a phase shift.

As shown in FIG. 14, if the ideal tracking error signal (Tr) is obtained, accurate tracking control is possible. As shown in FIG. 14, if the tracking error signal is out of phase, accurate tracking control cannot be performed. Such a phase shift of the tracking error signal is caused by the groove shape of the medium. In this case, the amount of control offset is different between the land L and the groove G.

Further, such a phase shift may similarly occur in the focus error signal. As described above, the tracking control and the focus control are performed by the tracking error signal (Tr) and the focus error signal (Fo). However, these control signals have an offset amount optically and electrically, which causes a control error. In order to reduce this control error, it is necessary to cancel the offset and perform control. This offset value is generally different between the groove portion and the land portion of the medium due to factors such as the degree of imbalance in the groove shape of the medium.

A first object of the present invention is to enable high quality recording / reproducing by optimizing different control offset values for the groove portion and the land portion of the medium. ). A second problem is to realize a method for measuring a control offset value (the invention of claim 2). A third problem is to enable high-quality recording / reproduction by optimizing different control offset values for the groove portion and the land portion for the one-sided reading type two-layer medium (claim 3). invention). Finally, a fourth problem is to realize a control offset value measuring method for a two-layer medium of the one-sided reading method (the invention of claim 4).

[0026]

According to another aspect of the present invention, there is provided an optical disk drive according to claim 1, further comprising means for measuring a control offset value of each of a groove portion and a land portion and storing the measured control offset value. The control offset value is switched depending on the position where the spot is illuminated.

According to a second aspect of the present invention, in the optical disc drive according to the first aspect, when a medium having pre-pits is loaded, the control offset is optimized by pre-pits pre-recorded in the groove portion and the land portion. It is a control offset value when the amplitude of the generated RF signal becomes maximum.

According to another aspect of the optical disk drive of the present invention, each layer of the medium is provided with means for measuring the control offset and storing the measured value of the control offset, and the layer on which the light spot of the objective lens is irradiated. The control offset value is switched by.

In the optical disc drive of claim 4, in the optical disk drive of claim 3, when a medium having pre-pits is loaded, the control offset is optimized by pre-recording the pre-pits in the groove portion and the land portion. It is a control offset value when the amplitude of the RF signal generated in 1 is maximized.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment The first embodiment corresponds to the inventions of claims 1 and 2. In the first embodiment, by optimizing different control offset values for the groove portion and the land portion of the medium, high quality recording / reproducing is possible (the invention of claim 1), and the control offset. It is characterized in that the value is measured (the invention of claim 2).

FIG. 1 is a functional block diagram showing an example of an embodiment of the main configuration of the optical disk drive of the present invention. In the figure, 31 is a comparator, 32 is an offset switching unit, 33 is a servo controller, 34
Is an L / G switching circuit, and 35 is a CPU.

When the CPU 35 outputs a command for switching between the land L and the groove G to the L / G switching circuit 34, the servo controller 33 irradiates the land L and the groove G of the designated medium with a light spot. Switch control. At the same time, the offset switching unit 32 is operated by the offset switching signal, and the land L
The offset value of the groove G is switched, and the control signal calculated by the optimum control offset value is sent to the servo controller 33.

In this way, the control offset values are measured at the groove portion and the land portion, and the measured values are stored, and the position where the light spot of the objective lens is irradiated (whether it is the groove portion or the land portion). The control offset value is switched according to whether or not (Claim 1).
Invention). Therefore, the objective lens can be controlled by the optimum control offset value in the groove portion and the land portion, and stable information reproduction / recording is realized. Next, a method of measuring the offset will be described. Time information in the media,
If the address information has a pre-pit recorded in advance, the optimum offset value is measured using the pre-pit.

FIG. 2 is a diagram for explaining the offset measuring method in the optical disk drive of the present invention. (1) is the arrangement state of prepits on the track of the medium, (2) is the relationship between the offset value and the RF signal. FIG. In the figure, P1 and P2 indicate prepits.

As shown in FIG. 2 (1), prepits (P1, P1) in which time information, address information, etc. are recorded in advance.
In the case of the medium provided with 2), when measuring the tracking control offset, an error is added to the control offset value to slightly move the tracking position of the objective lens. Then, if the C / N of the RF signal of the prepit is measured while slightly moving, the error amount that maximizes the C / N becomes the control offset, as shown in FIG. 2 (2). The C / N of the RF signal is measured at the land portion and the groove portion, respectively. Also, the focus control offset is similarly measured while adding an error to the control offset value and slightly moving the focus position of the objective lens.

As described above, in optimizing the control offset value, the control offset value when the amplitude of the RF signal generated in the prepit recorded in advance in the groove portion and the land portion becomes maximum is obtained (claim 2). Invention). Therefore, the control offset value is measured quickly and with high accuracy, and stable information reproduction / recording is realized. The above operation is shown in the flow.

FIG. 3 is a flow chart showing the main processing flow at the time of irradiation with the control offset value in the optical disk drive of the present invention. In the figure, # 1 to # 1
# 3 indicates a step.

In step # 1, the control offset value is measured for each of the groove portion and the land portion, and the optimum offset measurement value is stored. In step # 2, CPU3
5 outputs a land / groove switching command. In step # 3, by the control offset value stored previously,
Irradiate a light spot on the commanded land / groove.

Second Embodiment The second embodiment corresponds to the inventions of claims 3 and 4. In the first embodiment, the case where the medium has the recording information in the groove portion and the land portion has been described.
In the second embodiment, for the two-sided medium of the one-sided reading method as shown in FIG. 13, by optimizing the control offset value in each recording layer (layer) of the medium, high-quality recording / reproduction is performed. The invention is characterized in that it makes possible (the invention of claim 3) and that the control offset value is measured (the invention of claim 3).

Even in the one-sided reading type two-layer medium, the offset amount varies depending on the recording layers (layer 0 and layer 1) to be irradiated. The difference in the offset amount is due to the difference in the groove shape of the medium, the difference in the substrate thickness, and the like. Specifically, the phase shift amount of the tracking error signal as described with reference to FIG. 14 and the optimum focus offset value of focus as described with reference to FIG. 4 vary depending on the substrate thickness of the medium.

FIG. 4 is a diagram showing an example of changes in the substrate thickness and offset of the medium for the single-sided reading type two-layer medium shown in FIG. The horizontal axis of the figure shows the substrate thickness, and the vertical axis shows the focus offset value (Fo).

As shown in FIG. 4, in the two-layer medium shown in FIG. 13, the optimum focus offset value (Fo) is obtained when the substrate thickness is 0.6 mm. Generally speaking, this offset value is different for each recording layer of the medium due to factors such as the degree of imbalance of the groove shape of the medium and the difference in the thickness of the medium. Therefore,
In the second embodiment, the control offset is measured for each layer of the two-layer medium, each measured value is stored, and the control is performed by the recording layer (layer) irradiated with the light spot of the objective lens. The offset value is switched (the invention of claim 3).

FIG. 5 is a functional block diagram showing an example of a second embodiment of the main configuration of the optical disk drive of the present invention. Reference numerals in the figure are the same as those in FIG. 1, and 41 indicates an offset switching unit.

In FIG. 5, only the portions changed in the previous FIG. 1 are shown. That is, in the offset switching unit 32 of FIG. 1, the land / groove offset value is switched to the side instructed by the L / G switching circuit 34. In the offset switching unit 41 of this FIG.
Instead of switching land / groove, the offset value is switched to layer 0 / layer 1. Other operations are the same as in FIG. 1 (the invention of claim 3). Therefore, the objective lens can be controlled by the optimum control offset value in each recording layer (layer 0 / layer 1), and stable information reproduction / recording is realized.

The optimum control offset value measuring method in this case is the same as that described with reference to FIG. 2 above, and the control offset is set to the error amount that maximizes the C / N of the RF signal of the prepit. The value (the invention of claim 4). As a result, the control offset value is measured quickly and with high accuracy,
Stable information reproduction / recording is realized. The flow is basically the same as that of FIG. 3 except that the layer 0 / layer 1 is switched instead of the land / groove.

In the first embodiment, the case where the control offset value of the land / groove is switched is used. In the second embodiment, the control offset value of the two recording layers (layer 0 / layer 1) is changed. The case where the switching is performed is described above. If such a control offset switching part is performed for a combination of two recording layers (layer 0 / layer 1) and lands / grooves, it is possible to correspond to the L / G recording of the two-layer medium shown in FIG. You can

FIG. 6 is a functional block diagram showing another example of the embodiment of the essential structure of the optical disk drive of the present invention. Reference numerals in the figure are the same as those in FIG. 1, and reference numeral 42 denotes an offset switching unit.

The offset switching section 42 shown in FIG.
The control offset value is switched four times, which is larger than the offset switching unit 32 in FIG. 1 and the offset switching unit 41 in FIG. That is, layer 0
Of the groove, the control offset value of the land of layer 0, the control offset value of the groove of layer 1, and the control offset value of the land of layer 1 0 /
Servo control is optimal for layer 1 and land / groove combination).

[0049]

According to the optical disk drive of the first aspect, the objective lens is controlled by the optimum control offset between the groove portion and the land portion of the medium. Therefore, stable reproduction / recording of information becomes possible.

In the optical disc drive of claim 2, in the optical disc drive of claim 1, when a medium having pre-pits is loaded, the control offset is optimized by pre-pits prerecorded in the groove portion and the land portion. It is a control offset value when the amplitude of the generated RF signal becomes maximum. Therefore, in addition to the effect of the optical disk drive of claim 1, it becomes possible to measure the control offset easily and with high accuracy.

In the optical disk drive of the third aspect, the objective lens is controlled by the optimum control offset in each layer of the medium. Therefore, stable reproduction / recording of information becomes possible.

According to the optical disc drive of claim 4, in the optical disc drive of claim 3, when a medium having pre-pits is loaded, the control offset is optimized by pre-pits prerecorded in the groove portion and the land portion. It is a control offset value when the amplitude of the generated RF signal becomes maximum. Therefore, in addition to the effect of the optical disk drive of claim 3, the control offset can be measured easily and with high accuracy.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an example of an embodiment of the main configuration of an optical disc drive of the present invention.

FIG. 2 is a diagram illustrating an offset measuring method in the optical disc drive of the present invention.

FIG. 3 is a flowchart showing a main processing flow at the time of irradiation with a control offset value in the optical disc drive of the present invention.

FIG. 4 is a diagram showing an example of changes in the substrate thickness and offset of the medium for the single-sided reading double-layer medium shown in FIG.

FIG. 5 is a functional block diagram showing an example of a second embodiment of the main configuration of the optical disc drive of the present invention.

FIG. 6 is a functional block diagram showing another example of an embodiment of the main configuration of the optical disc drive of the present invention.

FIG. 7 is a partially enlarged perspective view showing the structure of a main part of a medium having recorded information in both the groove part and the land part.

FIG. 8 is a perspective view showing a structure of a general optical pickup.

FIG. 9 is a side view showing a relationship between a medium having recorded information in a groove portion and a land portion and an objective lens.

FIG. 10 is a diagram illustrating an offset in tracking control.

FIG. 11 is a diagram illustrating an offset in focus control.

FIG. 12 is a diagram showing a configuration for performing offset cancellation with respect to a medium on which recording is performed only on one of a groove portion and a land portion.

FIG. 13 is a diagram showing a single-sided reading double-layer medium,
It is a figure explaining the position of the objective lens at the time of reading of each recording layer.

FIG. 14 is a diagram illustrating a phase shift that occurs in a tracking error signal.

[Explanation of symbols]

 31 comparator 32 offset switching unit 33 servo controller 34 L / G switching circuit 35 CPU

Claims (4)

[Claims] 1. A control offset value is measured for each of the groove portion and the land portion, and a means for storing the measured value of each control offset is provided, and the control offset value is set according to a position where the light spot of the objective lens is irradiated. Optical disk drive characterized by switching. 2. The optical disc drive according to claim 1, wherein when a medium having prepits is loaded,
The optical disc drive characterized in that the control offset is optimized by setting the control offset value when the amplitude of the RF signal generated in the prepits recorded in advance in the groove portion and the land portion becomes maximum. 3. A control offset value is switched for each layer of the medium, and the control offset value is switched depending on the layer on which the light spot of the objective lens is irradiated. An optical disk drive characterized in that 4. The optical disk drive according to claim 3, wherein when a medium having pre-pits is loaded,
The optical disc drive characterized in that the control offset is optimized by setting the control offset value when the amplitude of the RF signal generated in the prepits recorded in advance in the groove portion and the land portion becomes maximum.