JP2004103234A - Optical disk device and optical disk processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device which can carry out focus control so that an objective lens will not crash with a disk, even if the distance between the disk and the objective lens is short and even if focus error signals become small and servo comes off due to the effect of flaws or dust on a disk. <P>SOLUTION: This device comprises a first optical system which has the objective lens with a first NA (optical numerical aperture, hereinafter referred to as NA), a second optical system which has the objective lens with a second NA lower than the first NA, an addition means to add the focus error signals detected by the first and the second optical systems, and a positioning means to decide the position of the objective lens according to the addition result by the addition means. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an optical disc apparatus that irradiates an optical disc having an information recording track with a light beam, records information on the information recording track, and reproduces information recorded on the information recording track. In particular, the present invention relates to detection of a focus error of a light beam in the optical disk device. The invention also relates to an optical disk processing method.

In recent years, various research and development on improving the recording density of optical disks has been promoted. Along with this, in an optical disk device, an attempt has been made to reduce the spot diameter of an optical spot by increasing an optical numerical aperture (NA: Numerical Aperture) or employing a laser having a short wavelength. On the other hand, it has been pointed out that when the optical NA is increased, the specification of the tilt of the objective lens becomes strict, and that the distance between the objective lens and the optical disk surface becomes shorter.

It is known that the specification of the tilt of the objective lens can be relaxed by reducing the distance from the optical disk surface (light incident surface) to the recording surface, that is, the thickness of the substrate. For an existing DVD or the like having a substrate thickness of about 0.6 mm, an optical disk having a shorter distance, for example, a substrate thickness of about 0.1 mm has been prototyped.

On the other hand, the adoption of a high NA also reduces the distance between the objective lens and the information recording surface. The distance between the objective lens and the optical disk is 1 mm or more in the current DVD. However, if a high NA exceeding 0.8 is adopted, the distance between the objective lens and the optical disk is close to a value less than 0.2 mm. As described above, the biggest problem when the objective lens and the optical disk are brought close to each other is that the objective lens collides with the optical disk. Such collision occurs when the focus control is deviated when disturbance is mixed in the reflected light from the optical disk at the time of focus pull-in (at the time of initial alignment of the objective lens) and the influence of scratches and fingerprint marks on the optical disk. There has been a demand for a focus control method that realizes a stable focus pull-in operation and has high resistance to the influence of scratches and fingerprint marks.

Conventionally, as a method of avoiding such collision, a method of performing an arc-shaped processing on the optical disk surface side of an objective lens has been proposed (see Patent Document 1). The objective lens having such a configuration utilizes the fact that a floating force with respect to the optical disk is generated by an air flow generated in a gap between the optical disk and the objective lens as the optical disk rotates. The objective lens is passively positioned at a position where the floating force and the driving force in the focusing direction are balanced. However, in this method, since the floating force of the objective lens with respect to the disk changes depending on the rotational speed of the disk, the floating amount is likely to change due to the fluctuation of the disk rotation, and unstable when the rotational speed of the disk is not constant. The control method was prone to

In order to accurately perform focus control, it is preferable to use a servo using a focus error signal by a focus system performed in a conventional optical disk device. For example, there has been proposed a method of achieving a stable focus pull-in operation by adding signals of a focus error detection system having two different focus error detection ranges (see Patent Document 2). According to this method, a focus error signal from a detection optical system capable of obtaining a wide focus error detection range and a focus error signal from a detection optical system capable of obtaining a high detection sensitivity while the focus error detection range is narrow are added to achieve stable focus pull-in. Implement the operation. At the same time, precise focus positioning is realized. However, in the state where the disk surface has scratches, dust, and fingerprint marks, it is inevitable that the amplitude of the focus error signal itself used for the servo signal becomes small, and that an event such as being affected by disturbance occurs. Furthermore, when the NA is high, the spot diameter on the disk surface becomes small, so that it is susceptible to these disturbances, and as a result, it is inevitable that the focus servo deviates. These unstable states operate similarly in focus pull-in, and a stable focus pull-in operation cannot be performed. That is, using the return light from one optical spot formed on the information recording surface of the optical disc to generate the above two types of focus errors, the optical spot formed by the optical system having a high NA has Instability cannot be avoided. As a result, conventionally, the focus control is weak against disturbances depending on the surface state of the optical disk such as scratches, dust and fingerprints, and the focus servo is likely to come off due to the influence of the disturbances.

Furthermore, once the servo is disengaged in this way, it may collide with the disc, not only scratching the optical disc, but also damaging the objective lens, making it impossible to record or reproduce information. there were. In this way, a focus error detection system that makes it difficult for the focus servo to come off even if it is affected by scratches, dust, dust, fingerprint marks, etc. Has been a common problem in realizing an optical disk device compatible with a high-density optical disk.
JP-A-2000-20985 JP-A-2000-11401

As described above, in the conventional focus error detection circuit, when applied to an optical system having a high NA, the possibility that the objective lens collides with the disk has increased. In addition, it was inevitable that the focus servo itself would come off due to the influence of scratches, dust, and fingerprint marks attached to the disk. When the focus servo deviates in this manner, the objective lens collides with the optical disk because the distance between the objective lens and the disk is small.

Furthermore, in the case of a high-density optical disk having a two-layer information recording surface, it was inevitable that the range of focus error detection would be narrowed. Therefore, problems such as deterioration of focus control performance occur. If the focus control fails, it is inevitable that the objective lens collides with the optical disk. Therefore, it is essential to realize a stable focus pull-in operation.

Further, in the case of an optical disk having a small substrate thickness, since the substrate thickness differs between individual optical disks, it is necessary to perform substrate thickness variation correction such as spherical aberration correction. It was necessary to realize a complicated control system such as performing focus control while performing spherical aberration correction that affects focus control.

An object of the present invention has been made in view of the above circumstances, and has as its object to provide the following optical disk device and optical disk processing method.

(1) An optical disc device capable of achieving stable focus control and focus pull-in operation even when a high NA optical system is used.

(2) An optical disk processing method capable of realizing stable focus control and focus pull-in operation even when an optical system having a high NA is used.

In order to solve the above problems and achieve the object, an optical disk apparatus and an optical disk processing method according to the present invention are configured as follows.

(1) An optical disc device according to the present invention includes an objective lens, an objective lens holder that holds the objective lens, and is supported so as to be drivable in the optical axis direction of the objective lens and in one direction perpendicular to the optical axis. A focusing actuator for driving the objective lens holder in the optical axis direction, and a light beam focused by the first numerical aperture among the light beams focused by the objective lens, First focus detecting means for detecting the displacement in the optical axis direction and focusing the light beam on the information recording surface of the optical disc; and a first numerical aperture of the light beam condensed by the objective lens Based on the reflected light of the light beam condensed at the lower second numerical aperture, the displacement in the optical axis direction is detected, and the light beam is focused on the information recording surface of the optical disk. Second focus detection means, addition means for adding a focus error signal detected by the second focus detection means to a focus error signal detected by the first focus detection means, and an output of the addition means And a drive control means for driving the focusing actuator.

に よ り With the above configuration, the following effects can be obtained.

A signal obtained by adding two focus error signals of a high NA (first numerical aperture) and a low NA (second numerical aperture) is used as a focus error signal for focus positioning of the objective lens. The focal point of the detection system is located slightly closer to the disk surface than the focal point of the high NA focus error detection system, and generates a driving force that becomes a large repulsive force when the objective lens defocuses in the direction of collision with the disk Let it.

ス ポ ッ ト In addition, since the spot diameter on the disk surface is larger in the low NA optical system than in the high NA optical system, it is possible to adopt a configuration resistant to the effects of dust, scratches and dust on the disk surface. Therefore, for example, even when the signal of the focus error detection system by the high NA optical system becomes small due to the influence of scratches or dust, the focus servo does not break down and the objective lens does not collide with the disk, and always goes away from the disk. A configuration in which servo is applied in the direction can be realized.

(2) An optical disk processing method according to the present invention provides a first optical system having a first objective lens having a first numerical aperture and a second optical system having a second objective lens having a numerical aperture higher than the first numerical aperture. A first step of irradiating a predetermined optical disk being rotated with a light beam through the first objective lens of the first optical system among the two optical systems to execute a focus pull-in process; A second step of determining an optical system suitable for the recording / reproducing process of the optical disc; and, if the optical system suitable for the recording / reproducing process of the optical disc is the first optical system, the first optical system A third step of irradiating the optical disc with a light beam through the first objective lens to process the optical disc, and an optical system suitable for recording / reproducing processing of the optical disc is provided by the second optical system. In case , Through the second of said second objective lens of the optical system, a light beam irradiated to the optical disc, and a, a fourth step of processing the optical disc.

According to the present invention, the following optical disk device and optical disk processing method can be provided.

(1) An optical disc device capable of achieving stable focus control and focus pull-in operation even when a high NA optical system is used.

(2) An optical disk processing method capable of realizing stable focus control and focus pull-in operation even when an optical system having a high NA is used.

Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

第一 [First Embodiment] The camera has two objective lens actuators, learns the surface shake, and performs focus pull-in.

FIG. 1 is a diagram showing a configuration of an optical disk device having a focus error detection circuit according to the present invention. FIG. 2 is an enlarged view around the objective lens actuator. In this configuration, two types of optical systems are used, and information is reproduced or recorded on a predetermined optical disk using a low NA optical system, and at the same time, a corresponding optical disk is reproduced using a high NA optical system. The optical head has two objective lenses and an actuator so that information can be reproduced or recorded.

(4) The optical disc 1 having the information recording surface is mounted on the spindle motor 2 and its rotation is controlled. An optical head that forms an optical spot on the information recording surface of the optical disc 1 and reproduces / records information is supported movably in the radial direction of the optical disc, and is positioned in the radial direction by a feed motor such as a stepping motor 3. On the carriage 4 on which the optical head is mounted, two objective lens actuators 5 and 6 are mounted, and the information recording tracks formed on the information recording surface are positioned in a focus direction in the direction perpendicular to the disk and tracks in the direction transverse to the tracks. The optical spot is precisely positioned in two directions. Here, of the two objective lens actuators, the first objective lens actuator 5 is provided for an optical system having a low NA, and receives, for example, a laser beam having a wavelength of about 650 nm to 780 nm, The lens 7 forms an optical spot on the information recording surface of the optical disk. The first objective lens actuator 5 is supported by a first objective lens support wire 15. On the other hand, the second objective lens actuator 6 is provided for an optical system having a high NA. For example, a laser beam having a wavelength of about 400 nm is incident on the second objective lens actuator 6, and the second objective lens 8 optically applies information to the information recording surface of the optical disc. Form spots. The second objective lens actuator 6 is supported by a second objective lens support wire 16. Here, an optical disk in which an optical spot is formed by the first objective lens and an optical disk by the second objective lens have different physical properties. That is, the optical disc on which information is reproduced and recorded by the first optical system is an optical disc on which information can be reproduced and recorded by a laser beam having a laser wavelength of 650 nm to 780 nm. -Plays and records RAM. On the other hand, an optical disc on which information is reproduced / recorded by the second optical system is an optical disc capable of reproducing / recording information with a laser beam having a laser wavelength of about 400 nm, and has a higher areal recording density than a DVD or the like. An optical disc in which the size of the optical spot formed on the information recording surface is smaller than the optical spot by the first optical system. In order to reproduce and record information on these two or more types of optical discs using laser beams of a plurality of wavelengths, the first and second optical systems are used in a switched manner.

FIG. 3 is a block diagram showing a main part for focus control of a focus pull-in method and a focus control method in an optical disk device having this configuration, and particularly a focus control method of an optical disk corresponding to a second optical system having a high NA. , And the flowchart of FIG.

First, a discrimination is made to determine whether the optical disc 1 attached to the spindle motor 2 is an optical disc for reproducing / recording information with the first optical system or an optical disc for reproducing / recording information with the second optical system. Perform (ST3). The disc discriminating sequence starts with the operation of performing focus control by the first optical system using the first objective lens with a low NA (ST2). Light reflected from the optical disk is incident on a first PD (Photo Detector) 21 via a beam splitter 11 and a condenser lens 13. Alternatively, the light is incident on the second PD 26 via the beam splitter 12 and the condenser lens 14. That is, a kick pulse for focusing is input to the first objective lens actuator while using the focus error signal detected by the first PD 21 for focus error detection provided in the first optical system. . FIG. 13 is a schematic diagram of a detection system using an astigmatism method as a general method of generating a focus error signal. In the figure, the value given by (A + C)-(B + D) of the four-divided PD is the focus error amount. At this time, it is desirable that the second objective lens actuator 6 is displaced and restrained in a direction away from the optical disc in order to avoid collision with the surface of the target optical disc (ST1). In the above operation procedure, the first objective lens actuator 5 is subjected to focus control on the optical disc 1 by the first focus control circuit 23 using the focus error signal from the first focus error detection circuit 22 having a low NA. This operation is performed in ascending order of wavelength by the number of laser light sources of the first optical system. For example, first, 780 nm laser light is incident to perform focus control, and subsequently, 650 nm laser light is incident to perform focus control. Here, after focus control has been tried with laser light of all wavelengths of the first optical system, if the information signal can be reproduced, or if the reproduced signal is a desired signal, the target optical disc is the first optical system. It is determined that the optical disk is compatible with the system (ST3). In this case, information recording / reproducing processing by the first optical system is executed (ST4).

After the focus control was attempted with laser light of all wavelengths of the first optical system, if the information signal could not be reproduced or the reproduced signal was not the desired signal, the target optical disk was compatible with the first optical system. It is determined that the optical disk is not an optical disk but an optical disk compatible with the second optical system (ST3), and an optical system switching operation occurs.

{However, before performing this switching operation, learning of the surface shake operation of the target optical disk is performed using the control signal of the focus control by the first objective lens actuator 5 (ST5). This control signal may be performed using a laser beam having any wavelength of the first optical system, but is preferably performed using a laser beam having the longest wavelength, for example, a laser beam having a wavelength of 780 nm. The learning operation is an operation of synchronizing the control signal of the actuator, which is output in response to the runout, with the rotation angle information of the spindle motor and storing the control signal by the runout phase estimation circuit. The first and second objective lens actuators are generally driven and controlled by electromagnetic driving. Control signals for these electromagnetically driven actuators are given as acceleration signals of the actuator. In the case where the drive signal is driven to follow a surface fluctuation which is a disturbance element having a low frequency such as a disk rotation frequency, the drive signal can be handled as a signal that changes in substantially the same phase as the position signal. In particular, the focus pull-in operation is performed in an inner peripheral portion of the disk where surface disturbance is expected to be small, and is in a region around 40 Hz, which is slightly higher as a rotation frequency for rotating the disk. Basically, it is not difficult to estimate the wobble phase in this frequency domain. For example, it is possible to perform an operation such as estimating the displacement of the actuator from the drive signal using a known response model of the dynamic characteristics of the actuator, and estimating the wobble phase as being equivalent to the wobble displacement.

The surface blur phase estimation circuit 24 stores the rotation angle information from the rotation angle detection circuit 25 of the spindle motor and the control output of the first focus control circuit 23 in synchronization. This storage operation will be described with reference to FIG. The rotation angle detection circuit 25 is configured to detect rotation angle information for each angle obtained by dividing 360 degrees into a plurality, for example. For example, in the case of detecting at every 60 degrees, the focus control output is sampled together with the rotation angle information at every 60 degrees, and for example, a voltage output value is stored as a sample value as shown in FIG. As described above, the stored voltage value is information that allows the value of the period and phase of the drive signal to be known even by linear interpolation. After the state of the runout is stored in synchronization with the rotation angle in this manner, the optical system is switched from the first optical system to the second optical system while controlling the rotation of the optical disk at the same rotation speed. In this switching operation, a laser beam of a predetermined wavelength is incident on the second objective lens actuator 6, and at the same time, a kick pulse control signal for pulling focus into the second objective lens actuator 6 is transmitted through the second focus control circuit. (ST6). The pull-in pulse is a drive signal for moving the second objective lens 8 in a direction to approach the optical disc. Therefore, the objective lens actuator 6 moves toward the optical disk surface simultaneously with the input of the kick pulse control signal. At the same time, the objective lens actuator 6 uses the focus error signal detected by the second photodetector 26 provided in the second optical system and calculated by the second focus error detection circuit 27 to perform the second focus control. It is controlled by the circuit 28. If the objective lens 8 moves to a position where the focus error signal can be detected by the second focus error detection circuit 27, and the relative speed between the objective lens 8 and the information recording surface of the optical disc 1 is smaller than a predetermined speed, the focus is adjusted. The pull-in operation succeeds (ST7). The surface wobbling speed is estimated from the surface wobbling state estimated by the surface wobbling phase estimation circuit 24 so that the relative speed falls within a predetermined range and the pull-in control is successful. Further, the kick pulse and the brake pulse are superimposed on the focus control signal from the pull-in pulse generation circuit 29 at the optimum timing when the relative speed with respect to the moving speed of the objective lens becomes small. Specifically, it is preferable that the surface shake amount is in the vicinity of the region closest to the objective lens 8 because the surface shake speed of the optical disc is low and the relative speed with the objective lens can be reduced. As described above, this pull-in operation is performed using the focus error signal from the second focus error detection circuit 27 provided in the second optical system. FIG. 4 shows the relationship between the signal of the surface shake phase estimating circuit, the pull-in pulse, and the focus error signal.

After the focus pull-in operation is performed in accordance with the phase shift phase, the focus of the second objective lens actuator 6 is controlled on the information recording surface of the optical disc. However, since the NA is high, the end surface of the objective lens is positioned at a position of about 0.2 mm or less from the optical disk surface. After confirming that the optical spot formed by the second objective lens 8 is in focus on the information recording surface of the optical disk, the fine adjustment operation is subsequently performed by the spherical aberration correction system provided in the second optical system. (ST8). This fine adjustment operation will be described with reference to FIG. 5 which is a block diagram showing a main part of the focus fine adjustment system.

(5) The spherical aberration correction system 30 shown in FIG. 5 is constituted by, for example, a relay lens, and adjusts the diameter of a laser beam or the spread angle of incidence on an objective lens by controlling the distance between two lenses. That is, it is a system that eventually corrects the spherical aberration of the optical spot. In the second optical system having a high NA, the thickness from the optical disk surface to the information recording surface is about 0.1 mm, and individual optical disks have thickness unevenness. Such a spherical aberration correction system may be employed to correct the thickness unevenness. The spherical aberration correction system 30 provided in this manner detects the total amount of return light from the optical disc detected by the second photodetector 26 in a state where the second objective lens actuator is under focus control, and detects the second return light. It is preferable that the spherical aberration correction control circuit 32 adjusts the spherical aberration correction system 30 so that the return light amount is maximized while the detection is performed by the circuit 31. Focusing on the fact that when the spherical aberration of the optical spot formed on the information recording surface is corrected, the return light also increases. By performing the above adjustment, a high-quality optical spot can be obtained. .

This completes the focus pull-in operation in the second optical system. After the focus pull-in operation is completed, the predetermined information recorded on the optical disk is read and reproduced, and it is confirmed that the target optical disk is an optical disk corresponding to a high NA optical system, and the recording or reproduction operation of the desired information signal is performed. (ST9).

In the above-described operation, the run-out learning may not be performed using the first optical system but may be performed using an optical system provided separately. In addition, in the step (ST5) of the surface blur learning and the pull-in step (ST6) at the optimal timing, it is not necessary to switch the first optical system to the second optical system. The focus pull-in of the second objective lens actuator may be realized in a state where the focus servo is applied while the objective lens actuator follows the surface deviation. In this case, the rotation speed of the disk does not need to be controlled at the same rotation speed as the rotation speed at the time of the runout learning, and may be rotated at an arbitrary rotation speed.

In the first optical system, a plurality of laser beams are incident on the same objective lens. However, for example, one objective lens actuator having two objective lenses, two laser light sources, and two laser light sources And a focus error detection circuit corresponding to the above. Specifically, it may be configured to include an objective lens corresponding to a wavelength of 780 nm, a first objective lens actuator holding an objective lens corresponding to 650 nm, and a laser beam and a detection system of the two wavelengths. Absent.

It is desirable that the second objective lens actuator is restrained at a position distant from the optical disk surface until the above-mentioned first optical system performs the surface shake phase learning. The positional relationship between the first and second lens actuators at this time will be described with reference to FIGS. First, when focus servo is performed by the first objective lens actuator having a low NA and the second objective lens actuator is not retracted and constrained, the first and second optical systems perform recording and reproduction when the first optical system performs recording and reproduction. The positional relationship between the two lens actuators is as shown in FIG. That is, the first objective lens actuator is driven so that the information recording surface 71 of the optical disc is brought into just focus. At this time, if the surface 70 of the optical disk is deviated, it is expected that the surface 70 of the optical disk will collide with the second objective lens. Then, in order to avoid this collision, as shown in FIG. 16, the second objective lens actuator is retracted and restrained at that position. Further, at the time of recording and reproduction by the second optical system, the positional relationship between the first and second lens actuators is as shown in FIG. The restraint described in FIG. 16 has a configuration in which a mechanical projection 73 is provided on the objective lens holder and restrained by a rotor 75 provided at the tip of a motor 74 as shown in FIGS. No problem. Further, as shown in FIG. 20, for example, the electromagnetic coil 76 provided on the second objective lens actuator may be configured to be electrically restrained with respect to the protrusion 77 of the carriage 4. In such a case, the retracting operation may be realized by the restoring force of the support spring when releasing from the constraint without using a drive control signal such as a retracting pulse. For example, if the objective lens actuator 6 is held in a direction away from the optical disk surface from the mechanical neutral position due to electromagnetic restraint, the objective lens actuator 6 may move toward the optical disk surface by spring force at the same time as the opening. become. The retracting operation may be realized by this moving speed.

In the focus pull-in operation, the above-described configuration does not perform the pull-in operation at the focal point on the optical disk surface, but realizes the focus pull-in operation only on the information recording surface. This is realized by providing a counter or the like so that the error signal is drawn into a portion where the error signal has changed for the second time while observing the focus error signal. However, since these counter operations are often not stable, a configuration is used in which focus control is first performed on the optical disk surface using a focus error signal observed on the optical disk surface, and then the focus is pulled into the information recording layer by a focus jump. It does not matter. Similarly, in the case of an optical disk having a plurality of information recording layers, it is preferable to always focus on the information recording layer on the near side and then sequentially jump to the back layer. It is possible to select a target information recording layer and perform focus pull-in by the counter operation. However, in consideration of the stability of the counter operation, it is possible to perform pull-in early for a layer before pull-in which can be performed. A reliable focus pull-in operation can be realized.

Also, in the focus system fine adjustment by the spherical aberration correction system, while observing the DC component of the focus control signal in the second focus control circuit 28, the spherical aberration correction system 30 is adjusted so as to reduce the DC component. A configuration such as 7 may be used. At this time, it is also possible to detect the return light amount at the same time and correct the spherical aberration to an optimum position.

Next, a second embodiment of the present invention will be described with reference to the drawings.

[2nd Embodiment] Two focus errors are generated and combined by the focus error detection optical system.

FIG. 8 is a diagram showing a configuration of an optical disk device having the focus error detection circuit of the present invention. Since the configuration of the first optical system with a low NA is the same as that of the first embodiment, only the configuration of the second optical system with a high NA is shown here.

In this configuration, a phase converter 51 having an action of shifting only the transmission phase near the center of the optical axis by about λλ (wavelength) is inserted in the optical axis of the high NA optical system. Part of the light incident on the second objective lens 8, in particular, light near the center of the optical axis is not condensed by the first constituent lens 62 constituting the second objective lens, and is not condensed by the second constituent lens 61. The light is condensed only by the light and forms a spot on the information recording surface of the optical disc. FIG. 9 shows the configuration of such a second objective lens 8. Light near the center of the optical axis condensed only by the second component lens 61 forms an optical spot so that the spot size on the information recording surface becomes large due to low NA. On the other hand, the light beam slightly outside the optical axis center where the wavelength is not shifted by the phase converter is condensed at a high NA by the first and second constituent lenses and forms a spot on the information recording surface in the optical disc. . This spot size is small due to the high NA. After each incident light is reflected by the information recording surface, it is separated by the polarizing beam splitter 52, and the light beam near the center of the optical axis is incident on the third PD 54 through the condenser lens 53 to detect the third focus error. The signal is detected by the circuit 55 as a third focus error signal. On the other hand, the light beam slightly distant from the center of the optical axis enters the second PD 26 via the beam splitter 12 and the condenser lens 14. The second focus error detection circuit 56 detects a second focus error signal based on the light intensity detected by the PD 26. The second focus error signal and the third focus error signal are respectively input to a second focus error calculation circuit 57, where addition and subtraction are performed. The calculated focus error signal is used as a focus error signal for driving the second objective lens actuator 6 in the second focus control circuit.

The calculation performed by the second focus error calculation circuit 56 at this time will be described with reference to FIG. In the second focus error calculation circuit 56, a focus error signal for the information recording surface of the optical disk is detected by a small optical spot focused at a high NA. For this reason, the range of the displacement amount having the sensitivity of the focus error signal is reduced, and the spot size on the optical disk surface is also reduced. On the other hand, in the third focus error calculation circuit 55, a focus error signal for the information recording surface of the optical disk is detected by a slightly larger optical spot focused at a low NA. For this reason, the range of the displacement amount having the sensitivity of the focus error signal can be made slightly large, and the spot size on the optical disk surface is also large. By using the focus error signal having the two properties as described above, it is possible to obtain a focus error signal for driving the second objective lens actuator 6 by performing, for example, addition by calculation.

The focus error signal thus calculated as shown in FIG. 11 has a large detection area of the third focus error signal, a property of being resistant to the influence of scratches and dust on the optical disk surface, and a property of the second focus error signal. It is possible to combine the two properties of high detection resolution in order to accurately perform focus positioning. Assuming that the second focus error signal is FE2 and the third focus error signal is FE3, the calculated focus error signal FE-Cal is, for example, FE-Cal = FE2 + α × FE3
It is required as follows. Here, α is an arbitrary positive number. By calculating the focus error in this way, the focus pull-in operation can be stably performed using the property of the third focus error signal, and the focus can be precisely positioned by the property of the second focus error signal. Is possible. Further, even when the second focus error signal is disturbed by the influence of disturbance such as scratches and dust on the optical disk surface and cannot be detected, the third focus error signal is strong against disturbance and can be detected. . For this reason, although the positioning accuracy of the focus control is slightly degraded, a gradual focus control that follows the surface deviation of the optical disk is realized without the control being lost and the objective lens colliding with the optical disk.

In the third focus error detection circuit 55 having the above configuration, the third focus error signal may be slightly electrically offset to detect the third focus error signal so that the third focus error signal is focused on the objective lens side from the information recording surface of the optical disc. It is possible. In this case, the focus error signal calculated by the second focus error calculation circuit 56 can be formed to have a plurality of focus positions as shown in FIG. In this case, in the focus pull-in operation, the pull-in operation is performed first to the in-focus position, and then the final focus position is jumped to the in-focus position which is the focus position of the second focus error detection system. It is possible to perform accurate focus positioning on a target information recording surface. Also, by adopting such a configuration at the same time, even if the focus error signal of the second focus error detection system may not be detected due to the surface condition of the optical disk, the focus is gradually moved away from the optical disk surface to the in-focus position. Because of the control, it is possible to avoid collision of the objective lens.

The above configuration is also effective when performing focus control on an optical disc having a plurality of information recording layers. In general, when an optical disc on which information is recorded / reproduced by a high NA optical system has a plurality of information recording layers, the interlayer distance between the information recording layers needs to be narrow. Specifically, it is preferable that the thickness be about 30 μm to 50 μm or less. This is because the reflection layer is formed of a metal film such as aluminum on the back layer, and a stable focus error signal can be expected even when the NA is low. On the other hand, however, with this configuration, the focus error detection of the first information recording layer formed on the front side of the objective lens and the focus error detection of the second information recording layer formed on the back side do not interfere with each other. Therefore, the detection range of the focus error becomes very narrow. Specifically, an error detection system in a range of about ± 3 μm is configured. In such a case, the second focus error calculation circuit includes a third focus error signal detected by the third focus error detection circuit and a second focus error signal detected by the second focus error detection circuit. To calculate a focus error signal to obtain a focus error signal that realizes stable focus control. In this case, it is preferable that the third focus error detection circuit is provided so as to detect the third focus error using the return light from the information recording layer at the back.

In the above-described configuration, the pull-in operation, the fine adjustment operation, and the jump operation of the focus control are the same as those in the first embodiment, and will not be described here.

Further, in the above configuration, the focus pull-in control can be stably performed according to the property of the third focus error signal, and therefore, it is not necessary to perform the surface shake learning by the first optical system having the low NA. .

According to the present invention as described above, the following effects can be obtained.

If there is a low NA optical system and a high NA optical system, each with a different objective lens actuator, first focus control by the first objective lens actuator that holds the first objective lens of the low NA optical system To learn the amount of surface deviation of the target optical disc. Thereafter, when it is determined that the target optical disk is for recording / reproducing information by the high NA optical system, the second optical system of the high NA optical system is referred to based on the learned surface shake phase. The second objective lens actuator that holds the two objective lenses performs the focus pull-in operation at an optimal timing, and makes it possible to stably shift to the focus control.

Also in the high NA optical system, the low NA focus error detection was performed using the light near the optical axis center, and the two focus error signals obtained by the high NA focus error detection and the low NA focus error detection were added. The signal is used as a focus error signal for focus positioning of the objective lens. With this configuration, the focal point of the low NA focus error detection system is provided slightly closer to the disk surface than the focal point of the high NA focus error detection system, and defocused in the direction in which the objective lens collides with the disk. In this case, a driving force that becomes a large repulsive force can be generated. Furthermore, by adopting such a configuration, the spot error on the disk surface can be made larger with a low-NA focus error detection system than with a high-NA focus error detection system. It is possible to obtain a strong focus error signal. Therefore, for example, even when the signal of the high NA focus error detection system becomes small due to scratches or dust, the focus servo will not break down and the objective lens will not collide with the disk, and the servo must always move away from the disk. Can be realized.

The invention of the present application is not limited to the above-described embodiment, and can be variously modified in an implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combinations as much as possible, in which case the combined effects can be obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effects described in the column of the effect of the invention can be solved. Is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

FIG. 2 is a diagram illustrating a periphery of an objective lens actuator of the optical disc device according to the first embodiment of the present invention. FIG. 2 is an enlarged view around an objective lens actuator of the optical disc device according to the first embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of a main part related to focus control of the optical disc device according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining signals during focus pull-in control of the optical disc device according to the first embodiment of the present invention. FIG. 2 is a first block diagram illustrating a schematic configuration of a main part of a focus fine adjustment system of the optical disc device according to the first embodiment of the present invention. 5 is a flowchart showing a reproducing process and a recording process by an objective lens having a different NA of the optical disc device according to the first embodiment of the present invention. FIG. 2 is a second block diagram illustrating a schematic configuration of a main part of a focus fine adjustment system of the optical disc device according to the first embodiment of the present invention. It is a block diagram showing a schematic structure of a main part of a focus error detection system of an optical disc device concerning a second embodiment of the present invention. FIG. 9 is a diagram illustrating a configuration of an objective lens of a high NA optical system of an optical disc device according to a second embodiment of the present invention. FIG. 10 is a diagram illustrating signals of a focus error detection system of the optical disc device according to the second embodiment of the present invention. FIG. 9 is a diagram illustrating an example of a calculated focus error signal. FIG. 9 is a diagram illustrating an example of a calculated focus error signal. FIG. 3 is a diagram for explaining a focus error detection method. FIG. 9 is a diagram for explaining a storage operation of synchronizing and storing rotation angle information from a rotation angle detection circuit of a spindle motor and a control output of a first focus control circuit. FIG. 9 is a diagram for explaining a case where the second actuator does not retract during recording and reproduction by the first optical system. FIG. 9 is a diagram for explaining a case where the second actuator has retracted during recording and reproduction by the first optical system. FIG. 8 is a diagram illustrating a state at the time of recording and reproduction by the second optical system. It is a figure showing signs that a 2nd actuator is restrained mechanically. It is an enlarged view showing signs that a 2nd actuator is restrained mechanically. It is a figure showing signs that a 2nd actuator is restrained electromagnetically.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Disk motor 3 ... Stepping motor 4 ... Carriage 5 ... 1st objective lens actuator 6 ... 2nd objective lens actuator 7 ... 1st objective Lens 8 Second objective lens 9 First rising mirror 10 Second rising mirror 11 First beam splitter 12 Second beam splitter 13 ..First condenser lens 14 Second condenser lens 15 First objective lens support wire 16 Second objective lens support wire 21 First PD
22 first focus error detection circuit 23 first focus control circuit 24 surface shake phase estimation circuit 25 rotation angle detection circuit 26 second PD
27 second focus error detection circuit 28 second focus control circuit 29 pull-in pulse generation circuit 30 spherical aberration correction system (relay lens system)
31 second return light detection circuit 32 spherical aberration correction system control circuit 51 phase converter 52 deflection beam splitter 53 condensing lens 54 third PD
55 third focus error detection circuit 56 second focus error detection circuit 57 second focus error calculation circuit 61 second component lens 62 first configuration Lens 70: Optical disk surface 71: Information recording surface of the optical disk (corresponding to the first optical system)
72 ··· Information recording surface of optical disk (corresponding to second optical system)
73 ... mechanical restraint projection 74 ... motor 75 ... rotor 76 ... electromagnetic coil 77 ... projection

Claims (7)

An objective lens,
Holding the objective lens, an optical axis direction of the objective lens, and an objective lens holder supported so as to be drivable in one direction perpendicular to the optical axis,
A focusing actuator for driving the objective lens holder in the optical axis direction,
Among the light beams condensed by the objective lens, the displacement in the optical axis direction is detected based on the reflected light of the light beam condensed at the first numerical aperture, and the light beam is transmitted to the information recording surface of the optical disc. First focus detection means for performing focusing of
Of the light beams condensed by the objective lens, the displacement in the optical axis direction is detected based on the reflected light of the light beam condensed at a second numerical aperture lower than the first numerical aperture, and Second focus detection means for focusing the light beam on the information recording surface;
Addition means for adding a focus error signal detected by the second focus detection means to a focus error signal detected by the first focus detection means;
Drive control means for driving the focusing actuator according to the output of the addition means;
An optical disk device comprising: The first focus detection unit focuses the light beam based on reflected light of the light beam that is separated from the center of the optical axis by a predetermined range in a direction orthogonal to the optical axis, of the light beam incident on the objective lens;
The second focus detection unit focuses the light beam on the basis of the reflected light of the light beam in a predetermined range in a direction orthogonal to the optical axis from the optical axis center among the light beams incident on the objective lens.
The optical disk device according to claim 1, wherein: 2. The optical disc according to claim 1, wherein a focal point of the second focus detection means is located closer to the objective lens than an information recording surface of the optical disc than a focus point of the first focus detection means. apparatus. By electrically adding an offset to a focus error signal indicating the displacement in the optical axis direction detected by the second focus detection means, the focal point of the second focus detection means is recorded on the optical disk. 4. The optical disk device according to claim 3, wherein the optical disk device is displaced from a surface toward the objective lens. When performing focus control on the information recording surface provided on the optical disc, after focusing on the focal point of the second focus detecting means, focus jump is performed to the focal point of the first focus detecting means. 5. The optical disk device according to claim 1, further comprising a drive control unit that controls driving of the objective lens holder so as to focus. A first optical system having a first objective lens having a first numerical aperture and a second optical system having a second objective lens having a numerical aperture higher than the first numerical aperture; A first step of irradiating a predetermined optical disc being rotated with a light beam through the first objective lens of the optical system to execute a focus pull-in process;
A second step of determining an optical system suitable for the recording and reproduction processing of the optical disc;
When the optical system suitable for the recording / reproducing process of the optical disc is the first optical system, the optical disc is irradiated with a light beam through the first objective lens of the first optical system, A third step of processing the optical disc;
When the optical system suitable for the recording and reproduction processing of the optical disc is the second optical system, the optical disc is irradiated with a light beam through the second objective lens of the second optical system, A fourth step of processing the optical disc;
An optical disk processing method comprising: The first step is
In a state where the second objective lens of the second optical system is retracted at a predetermined distance or more from the optical disc, the optical disc is moved to the optical disc via the first objective lens of the first optical system. Irradiate a light beam and execute focus pull-in processing;
7. The optical disk processing method according to claim 6, wherein:

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