JP4132034B2 - Optical head and optical disk apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical head and an optical disc apparatus for performing recording or reproduction on a rotating disk-shaped information carrier (hereinafter referred to as “optical disc”), and in particular, when performing recording or reproduction, The present invention relates to an optical head and an optical disc apparatus that perform a focus pull-in operation without colliding with a lens that collects a light beam.
[0002]
[Prior art]
In a conventional optical disk apparatus, when reproducing a signal, a light beam having a relatively weak constant light amount is irradiated on the optical disk, and reflected light that is strongly or weakly modulated by the optical disk is detected. Further, in the signal recording, information is written on the recording material film on the optical disk by modulating the intensity of the light beam in accordance with the signal to be recorded. This is described in, for example, Patent Document 1.
[0003]
In a reproduction-only optical disc, information by pits is recorded in a spiral shape in advance. An optical disc that can be recorded and reproduced is manufactured by forming a material film that can be optically recorded and reproduced on a surface of a substrate having a spiral concavo-convex track by a technique such as vapor deposition. In order to record information on the optical disc or to reproduce the recorded information, the normal direction of the surface of the optical disc (hereinafter referred to as “focus direction”) so that the light beam is always in a predetermined convergence state on the recording material film Focus control to be controlled at () is required.
[0004]
A conventional optical disc control operation will be described with reference to FIG. The optical head 10 includes a semiconductor laser 11, a coupling lens 12, a polarizing beam splitter 13, a quarter-wave plate 14, a condenser lens 15, a focus actuator (hereinafter referred to as “Fc actuator”) 16 as a focus moving unit, and tracking. An actuator (hereinafter referred to as “Tk actuator”) 17, a detection lens 18, a cylindrical lens 19, and a photodetector 20 are attached.
[0005]
The light beam generated from the semiconductor laser 11 is collimated by the coupling lens 12, passes through the polarization beam splitter 13 and the ¼ wavelength plate 14, and is condensed on the disc-shaped optical disk 1 by the condenser lens 15. . The reflected light beam passes through the condenser lens 15 and the quarter wavelength plate 14 again, is reflected by the polarization beam splitter 13, passes through the detection lens 18 and the cylindrical lens 19, and passes through the light receiving unit divided into four parts. The light detector 20 is irradiated. The condensing lens 15 is supported by an elastic body such as a spring. When a current is passed through the Fc actuator 16, the condensing lens 15 moves in a direction (focus direction) substantially perpendicular to the optical disk 1 by electromagnetic force. The photodetector 20 having the light receiving unit divided into four sends each detected light amount signal to the focus error generator 30 (hereinafter referred to as “FE generator 30”).
[0006]
The FE generator 30 uses each light amount signal from the photodetector 20 having a light receiving section divided into four, and an error signal (hereinafter referred to as “FE signal”) indicating the convergence state of the light beam on the information surface of the optical disc 1. Is sent to the Fc actuator 16 via the focus control filter 31 (hereinafter referred to as “Fc filter”), the drive selector 32 and the focus driver 33 (hereinafter referred to as “Fc driver”). The FE generator 30 sends an FE signal to the pull-in signal generator 71.
[0007]
FIG. 17B is a diagram illustrating a light receiving unit of the photodetector 20. As shown in the figure, the photodetector has four light receiving portions 201a to 201d. Since astigmatism is generated by the cylindrical lens, if the condensing lens 15 changes in the direction approaching the optical disc 1 with respect to the position of the condensing lens 15 in the focused state, the light on the photodetector 20 The focal point of the beam is an ellipse extending in the direction of the light receiving unit 201a and the light receiving unit 201c. When the condensing lens 15 changes in the direction away from the optical disc 1 with respect to the focal point, the focal point of the light beam on the photodetector 20 becomes an ellipse extending in the direction of the light receiving unit 201b and the light receiving unit 201d. The FE generator 30 generates the FE signal by calculating the difference between the light amount sum in the light receiving unit 201a and the light receiving unit 201c and the light amount sum in the light receiving unit 201b and the light receiving unit 201d. This method is called astigmatism method. The Fc actuator 16 drives the condenser lens 15 in the focus direction so that the light beam converges on the information surface of the optical disc 1 in a predetermined state. This is focus control.
[0008]
A search drive generator 64 as search drive generation means generates a drive signal for driving the Fc actuator 16 in the approaching direction or the separation direction at a constant speed. The search drive generator 64 sends a signal to the Fc actuator 16 via the drive selector 32 and the Fc driver 33. A signal from the photodetector 20 is sent to the reflected light amount detector 70. The reflected light amount detector 70 calculates the sum signal from all the light receiving parts of the photodetector 20 and sends it to the lead-in signal generator 71. The pull-in signal generator 71 drives the low-level signal until the signal from the reflected light amount detector 70 is equal to or higher than the predetermined level L1 and the FE signal from the FE generator 30 passes the reference level from positive to negative. Send to 32. Thereafter, a high level signal is sent to the drive selector 32. When the signal from the pull-in signal generator 71 is at a high level, the drive selector 32 sends a signal from the Fc filter 31 that is a focus control driving means to the Fc driver 33, and the signal from the pull-in signal generator 71 is at a low level. At this time, a signal from the search drive generator 64 is sent to the Fc driver 33. The Fc driver 33 drives the Fc actuator 16 based on the signal selected by the drive selector 32.
[0009]
The FE signal from the FE generator 30 and the signal from the reflected light amount detector 70 as detection signals will be described with reference to FIG. FIG. 18A is a diagram illustrating an example of the output of the FE signal from the FE generator 30, and FIG. 18B is a diagram illustrating an example of the output of the signal from the reflected light amount detector 70. The horizontal axis of FIG. 18 is the relative position of the optical disc 1 and the condenser lens 15 in the focus direction, and is the approach direction from the left side to the right side in the figure. The vertical axis in FIG. 18 indicates the level of each signal. As shown in FIG. 18A, the FE signal from the FE generator 30 becomes a positive signal in the direction away from the focal point and a negative signal in the approach direction. As shown in FIG. 18B, the signal from the reflected light amount detector 70 becomes a mountain-shaped signal in the same detection range as the FE signal.
[0010]
The focus pull-in operation will be described with reference to FIG. 19A shows an example of the output of the FE signal from the FE generator 30, FIG. 19B shows an example of the output of the signal from the reflected light amount detector 70, and FIG. FIG. 19D is a diagram showing an example of signal output from the drive selector 32, and FIG. 19D is a diagram showing an example of signal output from the pull-in signal generator 71. In FIG. 19, the horizontal axis represents time, and the vertical axis represents the level of each signal. The polarity of the signal from the drive selector 32 necessary for the condenser lens 15 to move in the direction approaching the optical disc 1 is the positive direction in FIG. As shown in FIG. 19D, when the focus pull-in starts, the signal from the pull-in signal generator 71 is at a low level, so the drive selector 32 sends the signal from the search drive generator 64 to the Fc driver 33. From a state in which the optical disc 1 and the condensing lens 15 are sufficiently separated from each other, the search drive generator 64 generates driving in a direction in which the condensing lens 15 approaches the optical disc 1 as shown in FIG. When the focal point of the light beam approaches the information focusing focal point of the optical disc 1, the FE signal from the FE generator 30 and the signal from the reflected light amount detector 70 are changed as shown in FIGS. 19 (a) and 19 (b). Appears.
[0011]
The pull-in signal generator 71 sets the signal to the drive selector 32 to a high level when the signal level from the reflected light amount detector 70 exceeds L1 and the FE signal from the FE generator 30 passes the reference level from positive to negative. To. Thereafter, the signal from the Fc filter 31 is selected by the drive selector 32, and the focus control is activated.
[0012]
[Patent Document 1]
JP 52-80802 A
[0013]
[Problems to be solved by the invention]
In the recordable optical disc 1, the recording operation is performed by absorbing the light beam irradiated on the information surface of the optical disc, that is, by changing the phase of the recording material by heat accumulation due to the absorption. Therefore, it is necessary to increase the absorptance of the information surface of the optical disc 1 in order to improve the recording speed, and in such a case, the reflectance decreases. Further, in order to improve the recording capacity, an optical disc having a plurality of information surfaces needs to irradiate a light beam to the information surface on the back side when viewed from the condensing lens 15. It is also necessary to increase the transmittance of the information surface. That is, the reflectance of the information surface of the optical disk tends to decrease as the recording capacity and recording speed are improved. Further, the reflected signal of the light beam is generated not only from the information surface of the optical disc but also from the surface of the optical disc. When the reflectance on the information surface of the optical disc 1 is reduced to the same as the reflectance on the surface of the optical disc, the FE signal from the FE generator 30 and the signal from the reflected light amount detector 70 are the same on the surface of the optical disc 1 and the information surface. Since it has a waveform, it cannot be distinguished during the focus pull-in operation, and focus control is performed on the surface of the optical disc 1. As a result, there is a problem that the time for irradiating the target address with the light beam becomes long.
[0014]
Furthermore, in order to improve the recording density of the optical disc 1, it is necessary to reduce the focal point of the light beam. Therefore, in general, when a small focal point is realized by shortening the focal length of the condensing lens 15, the distance from the information focusing point to the collision position is shortened, and the possibility of collision between the condensing lens 15 and the optical disc 1 is increased. . Therefore, for the problem that the reflectance on the information surface and the surface of the optical disk is equivalent, the focus of the light beam is moved after moving the condenser lens 15 so that the focus of the light beam is closer to the optical disk 1 side than the information surface of the optical disk 1. However, there has been proposed a solution for performing the focus pull-in operation while keeping the camera away from the optical disc 1. However, when the distance from the focal point of the information surface to the collision position is smaller than the surface blur of the optical disc 1, it is not possible to make the condensing lens 15 approach the optical disc 1 from the focal point of the information surface without colliding. There was a big problem that 1 was damaged.
[0015]
The present invention has been made to solve the above-described problems. When information is reproduced or recorded, the focal point of the light beam and the surface of the optical disk are very close, or the reflectance of the information surface is reduced. Providing a highly reliable optical head and optical disk device by avoiding collision between the condensing lens and the optical disk and preventing the condensing lens and the optical disk from being damaged even when the surface reflectance is equivalent. The purpose is to do.
[0016]
[Means for Solving the Problems]
The optical disc apparatus of the present invention has a light receiving region divided into substantially concentric circles of a light beam, receives light reflected from an information carrier, and uses light detection means for outputting a signal corresponding to the amount of reflected light. The amount of light reflected from the carrier is detected. On the basis of the signal from such a light detection means, a detection signal is obtained which continuously changes so as to have one maximum point while the focus of the light beam is from the surface of the information carrier to the information surface. Therefore, by observing such a detection signal, the positional relationship between the focal point of the light beam and the surface or information surface of the information carrier can be known. For example, the inclination (change rate) of such a detection signal is detected, and when the inclination becomes negative, it can be determined that the focal point of the light beam is close to the information surface of the information carrier. Further, since the focal point of the light beam corresponds to the position of the condensing lens, the signal level of such a detection signal is compared with a predetermined level, and when the signal level of the detection signal exceeds the predetermined level, the condensing lens It can be determined that it is in the vicinity of the surface of the information carrier. By using the determination result as described above, it is possible to avoid the collision prevention between the condenser lens and the information carrier with high accuracy.
[0017]
A first optical disc apparatus according to the present invention includes a converging means for converging and irradiating a rotating information carrier with a light beam, a focus moving means for moving the converging means in the normal direction of the information surface of the information carrier, A light detection means having a light receiving area divided concentrically, receiving reflected light from the information carrier and outputting a signal corresponding to the amount of reflected light, and the focus of the light beam based on the signal from the light detection means A near-surface detection means for generating a continuously changing signal having one maximum point from the surface of the carrier to the information surface, and a drive signal for moving the focal point of the light beam toward or away from the information carrier A search driving means for generating a signal, a focus deviation signal detecting means for generating a signal corresponding to the positional deviation of the focal point of the light beam with respect to the information surface or surface of the information carrier, and an optical beacon according to the signal of the focus deviation signal detecting means. A focus control driving means for generating a signal for driving the focus moving means so that the focal point of the image follows the information surface of the information carrier, and a signal from the surface vicinity detecting means and a signal from the focus deviation signal detecting means. Based on the information surface discriminating means for discriminating whether or not the focal position of the light beam is in the vicinity of the information surface of the information carrier, and the signal from the focus control driving means and the search drive according to the signal from the information surface discriminating means And a focus pull-in means for selecting one of the signals from the means and supplying the selected signal to the focus moving means. The size of the light receiving area of the light detection means is the amount of light reflected from the surface of the information carrier detected by the light detection means and the information on the information carrier at the center between the surface of the information carrier and the information surface closest to the surface of the information carrier. The width is such that the sum of the amount of reflected light from the surface is larger than the amount of reflected light detected on the surface of the information carrier or the information surface of the information carrier. .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an optical disc apparatus according to the present invention will be described below with reference to the accompanying drawings.
[0022]
(Embodiment 1)
FIG. 1 is a block diagram of an optical disc apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram for explaining a photodetector 21 which is a reflected light amount detection means in the optical disc apparatus of the present embodiment.
[0023]
In FIG. 1, the same components as those in FIG. The optical disc apparatus of this embodiment includes an optical head 10, an FE generator 30, an Fc filter 31, a drive selector 32, and an Fc driver 33. Further, the optical disc apparatus includes a near-surface detector 61, an information surface detector 62, a pull-in signal generator 63, and a search drive generator 64. The pull-in signal generator 63, the drive selector 32, and the Fc driver 33 function as focus pull-in means.
[0024]
The optical head 10 of the present embodiment has a photodetector 21 as shown in FIG. While the photodetector 20 in the prior art shown in FIG. 16B is configured only by the light receiving portions 210a to 210d, the photodetector 21 of the present embodiment has four light receiving portions 210a to 210d in the center. In addition, a square-shaped light receiving portion 210e is provided so as to surround the outer periphery of these light receiving portions 210a to 210d. The light receiving units 210a to 210d receive light at the inner periphery of the light beam, and the light receiving unit 210e receives light at the outer periphery of the light beam. Accordingly, the light beams can be divided substantially concentrically by the light receiving units 210a to 210d and the light receiving unit 210e, and the amount of the light can be detected. It can receive light. The photodetector having such a configuration is also disclosed in the application of Japanese Patent Application No. 2000-319008 of the present applicant.
[0025]
When generating the FE signal and reproducing the recording signal in the FE generator 30, a signal based on the light received by the light receiving units 210a to 210d located inside is used. A signal from the photodetector 21 is sent to an FE generator 30 that is a focus deviation detection unit and a near-surface detector 61 that is a near-surface detection unit.
[0026]
The near-surface detector 61 sends the sum signal of the signals from all the light receiving units 210a to 210e of the photodetector 21 to the information surface detector 62 that is information surface discrimination means. The information surface detector 62 differentiates the signal of the near-surface detector 61, for example, determines the increase or decrease of the signal level of the near-surface detector 61 according to the polarity of the differentiated signal level, and the focal point of the light beam is the information surface. It is determined whether or not it is in the vicinity. The information surface detector 62 sends a high-level signal to the pull-in signal generator 63 when the signal level from the near-surface detector 61 decreases, and a low-level signal otherwise. The pull-in signal generator 63 drives the low-level signal until the gate signal from the information surface detector 62 is at a high level and the FE signal from the FE generator 30 passes through the reference level from positive to negative. Thereafter, a high level signal is sent to the drive selector 32.
[0027]
FIG. 3 shows the structure of the optical disc 1 accessed by the optical disc apparatus of this embodiment. FIG. 3A shows the structure of an optical disc having one recording layer 91 (hereinafter referred to as “single-layer optical disc”), and FIG. 3B shows an optical disc having two recording layers 91a and 91b (hereinafter “single-layer optical disc”). The structure of a “two-layer optical disc” is shown. The reflectivity of the optical disk is 12% to 24% in the case of a single layer, and 4% to 8% in the case of a double layer. Note that this value is a case where recording has not been performed, and in the case where recording has been performed, the value is reduced by about 70% compared to when recording is not performed. In a single-layer optical disc, the distance from the surface to the information surface is 100 ± 5 μm. In a two-layer optical disc, the distance from the surface to the information surface closer to the surface is 75 ± 5 μm, and the distance between the information surfaces is 30 ± 5 μm.
[0028]
A signal waveform from the near-surface detector 61 in the present embodiment will be described with reference to FIGS. FIG. 4 shows a waveform from the optical disc 1 having a single recording layer, and FIG. 5 shows a waveform from an optical disc having two recording layers. More specifically, FIG. 4A shows an example of the output of the FE signal from the FE generator 30 when the optical disc 1 has a single layer, and FIG. 4B shows the optical disc 1 with a single layer. FIG. 4C is a diagram showing an example of an output signal from the near-surface detector 61 when the optical disc 1 is a single layer. 5A shows an example of the output of the FE signal from the FE generator 30 when the optical disc 1 has two layers, and FIG. 5B shows the amount of reflected light when the optical disc 1 has two layers. FIG. 5C is a diagram showing an example of an output signal from the detector 70. FIG. 5C is a diagram showing an example of an output signal from the near-surface detector 61 when the optical disc 1 has two layers.
[0029]
4 and 5, the horizontal axis represents the relative position in the focus direction between the optical disc 1 and the condensing lens 15 as a converging means, and the condensing lens 15 approaches the optical disc 1 from the left side to the right side in the figure. Direction. Moreover, the vertical axis | shaft of FIG. 4, 5 shows the level of each signal. As shown in FIGS. 4 (a), 4 (b), 5 (a), and 5 (b), if the reflectances on the surface and the information surface are equal, from the FE signal from the FE generator 30 and the reflected light amount detector 70, There is no difference in the signals of and cannot be distinguished. On the other hand, the near-surface detector 61 shown in FIGS. 4C and 5C detects all the signals from the light detector 21 having a light detection area wider than that of the conventional light detector 20 for detection. The range becomes wider, and as shown in FIGS. 4C and 5C, a waveform extending over the surface of the optical disc 1 and the information surface is obtained.
[0030]
As shown in FIG. 4 (c) and FIG. 5 (c) From the near-surface detector 61 Since the signal has a different tilt when the light beam is focused on the surface and when it is near the information surface, if the difference in tilt is detected, the state where the focus of the light beam is located near the surface and the information surface A state located in the vicinity can be distinguished.
[0031]
A focus pull-in operation in the optical disc apparatus according to the present embodiment will be described with reference to FIGS. 6A is a diagram illustrating an example of the output of the FE signal from the FE generator 30, FIG. 6B is a diagram illustrating an example of the output of the signal from the near-surface detector 61, and FIG. FIG. 6D shows an example of signal output from the information surface detector 62, FIG. 6D shows an example of signal output from the drive selector 32, and FIG. 6E shows a signal from the pull-in signal generator 63. FIG. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the level of each signal. FIG. 7 is a flowchart showing this sequence.
[0032]
The polarity of the signal from the drive selector 32 necessary for the condenser lens 15 to move in the direction approaching the optical disc 1 is the positive direction in FIG. As shown in FIG. 6E, when the focus pull-in starts, the signal from the pull-in signal generator 63 is at a low level, so the drive selector 32 sends the signal from the search drive generator 64 to the Fc driver 33. From the state where the optical disc 1 and the condensing lens 15 are sufficiently separated from each other, the search drive generator 64 generates driving in the direction in which the condensing lens 15 approaches the optical disc 1 as shown in FIG. S11). As shown in FIG. 6B, when the focal point of the light beam approaches the surface of the optical disc 1, a signal in the positive direction from the near-surface detector 61 is generated. While monitoring the signal level from the near-surface detector 61, the condenser lens 15 is moved closer to the optical disc 1 until the signal level from the near-surface detector 61 exceeds the maximum point (step S12). As a result, the focal point of the light beam keeps approaching the optical disc 1.
[0033]
Thereafter, when the focal point of the light beam passes through the surface of the optical disk 1 and the signal level from the near-surface detector 61 exceeds the maximum point, the signal from the information surface detector 62 is low as shown in FIG. Change from level to high level. Then, it waits for the FE signal from the FE generator 30 to change from positive to negative with the reference level set to 0 (step S13). As a result, the focal point of the light beam continues to approach the optical disc 1 further. When the FE signal from the FE generator 30 changes from positive to negative on the information surface as shown in FIG. 6A, the signal to the drive selector 32 is changed from low level to high as shown in FIG. The level is changed to the level, thereby bringing the focus control into an operating state (step S14).
[0034]
Thereafter, as shown in FIG. 6D, the drive selector 32 uses a signal from the Fc filter 31 instead of a signal from the search drive generator 64 as a signal to be sent to the Fc driver 33.
[0035]
In this way, according to the present embodiment, the focal position is obtained by using the sum signal of the output signals from the photodetector 21 shown in FIG. 2 having the waveform shown in FIG. 4C or 5C. Can be detected between the disk surface and the information surface, so that the focus pull-in operation can be more reliably performed on the information surface of the optical disk 1.
[0036]
In the present embodiment, the near-surface detector 61 sends the full addition signal of the photodetector 21, but only the signal from the light receiving unit 210e shown in FIG. 2 may be used.
[0037]
Further, in the present embodiment, the information surface detector 62 detects the information surface from the inclination of the signal from the surface vicinity detector 61, but the FE signal from the FE generator 30 is the maximum from the surface vicinity detector 61 when it is maximum. If the signal level is stored and the stored level is small as a result of comparing the signal level from the near-surface detector 61 when the FE signal from the FE generator 30 passes the reference level, The information surface detector 62 may detect that the focal point of the light beam is in the vicinity of the information surface.
[0038]
In the present embodiment, a dedicated light receiving unit for detecting the light applied to the outer peripheral portion of the photodetector 21 is provided. However, the positional error between the track and the focal point of the light beam is calculated using the DPP method or three beams. A sub-beam light-receiving unit used when generating by a method may be used.
[0039]
Further, the near-surface detector 61 and the information surface detector 62 may be provided in the optical head 10.
[0040]
(Embodiment 2)
As described in the prior art, in the optical disc apparatus, the condenser lens is supported by an elastic body such as a spring. Therefore, there is a risk of collision between the condensing lens and the optical disc if the condensing lens vibrates up and down due to surface shake or external vibrations in a situation where focus control or the like is not performed on the condensing lens. is there. Therefore, in the present embodiment, an optical disc apparatus that prevents such a collision in a non-control state with respect to the condenser lens will be described.
[0041]
FIG. 8 shows a block diagram of the optical disc apparatus in the second embodiment. In FIG. 8, the same components as those in FIG.
[0042]
The optical disc apparatus of this embodiment includes an optical head 10, an FE generator 30, an Fc filter 31, a drive selector 32, and an Fc driver 33. The optical disc apparatus further includes a near-surface detector 61, a separation drive generator 65, and an Fc control switch 66. The separation drive generator 65 and the Fc driver 33 function as avoidance drive generation means. The configuration of the photodetector 21 is as described in FIG.
[0043]
When generating the FE signal and reproducing the recording signal in the FE generator 30, a signal based on the light received by the light receiving units 210a to 210d located inside is used. A signal from the photodetector 21 is sent to the FE generator 30 and the near-surface detector 61. The near-surface detector 61 sends the sum signal of all the light receiving parts of the photodetector 21 to the separation drive generator 65. The separation drive generator 65 moves the condenser lens 15 from the optical disc 1 when the signal level from the near-surface detector 61 is equal to or higher than a predetermined level L2 set by a drive level setting means (not shown) provided therein. A fixed value drive signal for the Fc actuator 16 for separation is generated and sent to the drive selector 32. The separation drive generator 65 sends “0” to the drive selector 32 when the signal level from the near-surface detector 61 is lower than the predetermined level L2. A focus control switch (hereinafter referred to as “Fc control switch”) 66 sends a low level signal to the drive selector 32 when, for example, the focus control is inactivated, and is high when the focus control is activated. Is sent to the drive selector 32.
[0044]
A collision avoidance operation in the optical disk apparatus according to the present embodiment will be described with reference to FIGS. 9A shows an example of the output of the FE signal from the FE generator 30, FIG. 9B shows an example of the output signal from the near-surface detector 61, and FIG. 9C shows the separation. It is a figure which shows an example of the output signal from the drive generator 65. FIG. In FIG. 9, the horizontal axis represents the relative position of the optical disc 1 and the condenser lens 15 in the focus direction, and is the approach direction from the left side to the right side in the figure. The vertical axis in FIG. 9 indicates the level of each signal. FIG. 10 is a flowchart showing this sequence.
[0045]
Referring to FIG. 10, a zero level signal is sent from the separated drive generator 65 to the Fc actuator 16 via the drive selector 32 and the Fc driver 33 (step S21). Thereby, the condensing lens 15 stays in a natural position determined by a support member such as a spring.
[0046]
And it is detected whether the signal from the surface vicinity detector 61 became larger than the predetermined level L2 (step S22). When the condensing lens vibrates up and down due to the surface shake caused by the rotation of the optical disc 1 or external vibration, and the condensing lens 15 and the optical disc 1 approach abnormally, the signal from the near-surface detector 61 becomes lower than the level L2. growing.
[0047]
When the signal from the near-surface detector 61 becomes larger than the level L2, as shown in FIG. 9C, the separation drive generator 65 drives the signal (negative level) for driving the condenser lens 15 away from the optical disc 1. Is sent to the drive selector 32 (step S23). At this time, since the focus control is inactive, a low level signal is sent from the Fc control switch 66 to the drive selector 32, and the drive selector 32 selects the signal from the separated drive generator 65, and the Fc driver Send to 33. As a result, the condenser lens 15 is separated from the optical disc 1.
[0048]
When the condensing lens 15 further approaches the optical disc 1 from the position where the focal point of the light beam is focused on the information surface, the optical disc 1 and the condensing lens 15 collide at the collision position shown in FIG. Since the signal from the near-surface detector 61 can be detected in a wide range and the position where the condenser lens 15 and the optical disc 1 collide is close to the position of the condenser lens 15 at the focal point, as shown in FIG. Even if the focal point of the light beam moves in the approaching direction and reaches the collision position, the signal level from the near-surface detector 61 does not attenuate to zero level. Therefore, it is possible to detect that the distance between the optical disc 1 and the condenser lens 15 is within a predetermined value by comparing the signal level from the near-surface detector 61 with a predetermined level L2, and avoid collision based on the detection result. The action can be performed.
[0049]
After the separation driving, the system waits until the signal from the near-surface detector 61 becomes smaller than the level L2 (step S24). As a result, a signal for the separation drive is continuously generated from the separation drive generator 65, and the condenser lens 15 remains at a position away from the optical disc 1.
[0050]
Eventually, when the signal from the near-surface detector 61 becomes smaller than the level L2, it means that the distance between the condenser lens 15 and the optical disk 1 is sufficiently large, so that the signal from the separation drive generator 65 is set to 0 level. (Step S25). Thereby, the condensing lens 15 remains in a natural position again.
[0051]
Note that when the high-level signal is sent from the Fc control switch 66 to the drive selector 32 and the focus control is in the operating state, the drive selector 32 selects the signal from the Fc filter 31, and thus the separated drive generator 65. The signal from does not affect the focus control.
[0052]
According to the present embodiment, every time the condensing lens 15 approaches the optical disc 1 under the non-control of the condensing lens, the driving that separates the condensing lens 15 occurs. Collisions can be avoided.
[0053]
In the present embodiment, the near-surface detector 61 sends the full addition signal of the photodetector 21, but only the signal from the light receiving unit 210e shown in FIG. 2 may be used.
[0054]
In the present embodiment, the separation drive generator 65 switches between two types of driving based on the comparison result between the distance between the optical disc 1 and the condenser lens 15 and a predetermined distance, and the Fc is switched via the drive selector 32 and the Fc driver 33. The condensing lens 15 is separated from the optical disk 1 by being sent to the actuator 16, but a signal obtained by multiplying the signal from the near-surface detector 61 by the gain and inverting the sign is sent to the Fc actuator 16. Also good.
[0055]
In the present embodiment, a dedicated light receiving unit for detecting the light applied to the outer peripheral portion of the photodetector 21 is provided. However, the positional error between the track and the focal point of the light beam is calculated using the DPP method or three beams. A sub-beam light-receiving unit used when generating by a method may be used.
[0056]
(Embodiment 3)
FIG. 11 shows a block diagram of the optical disc apparatus in the third embodiment. In FIG. 11, the same components as those in FIG. The optical disk apparatus according to the present embodiment includes an optical head 10, an FE generator 30, an Fc filter 31, a drive selector 32, and an Fc driver 33, and further includes a rotational phase detector 51, a drive storage device 68, an adder 69, and a pull-in signal. A generator 67 and a search drive generator 64 are provided.
[0057]
The pull-in signal generator 67, the drive selector 32, and the Fc driver 33 function as focus pull-in means.
[0058]
The search drive generator 64 sends a high-level signal to the pull-in signal generator 67 when the drive signal to be generated is in the direction of separation, and the low-level signal when the drive signal to be generated is in the direction of approach. Send to 67.
[0059]
The pull-in signal generator 67 sends a low level signal to the drive selector 32 until the signal from the search drive generator 64 is at a high level and the FE signal from the FE generator 30 passes from the negative to the positive reference level. Thereafter, a high level signal is sent to the drive selector 32.
[0060]
The motor 50 rotates the optical disc 1 and sends 1000 encoder pulses per rotation to the rotation phase detector 51. The rotation phase detector 51 counts the rising edge of the encoder pulse from the motor 50 and clears the count value to 0 when 1000 pulses corresponding to one rotation are counted. The rotational phase detector 51 sends the count value to the drive storage device 68 which is a surface shake storage means.
[0061]
The drive memory 68 stores the drive signal from the Fc filter 31 at the storage address based on the count value from the rotation phase detector 51 when the signal from the pull-in signal generator 67 is at a high level, and the surface blur signal applying means. 0 level is sent to the adder 69. Further, the drive memory 68 does not update the stored information when the signal from the pull-in signal generator 67 is at a low level, and the storage information of the storage address based on the count value from the rotational phase detector 51 is not added to the adder 69. Send. The adder 69 adds the signal from the search drive generator 64 and the signal from the drive memory 68 and sends the result to the drive selector 32.
[0062]
The operation of the drive memory 68 will be described with reference to FIG. FIG. 12A is a diagram illustrating an example of signal output from the rotational phase detector 51, and FIG. 12B is a diagram illustrating an example of signal output from the Fc filter 31. In FIG. 12, the horizontal axis indicates time, and the vertical axis indicates the level of each signal. FIG. 12 shows waveforms when the focus control is in an operating state. Accordingly, the pull-in signal generator 57 sends a high level signal to the drive memory 68 and the drive selector 32. The drive selector 32 sends the signal from the Fc filter 31 to the Fc driver 33 because the signal from the pull-in signal generator 67 is at a high level.
[0063]
As shown in FIG. 12A, the signal from the rotation phase detector 51 becomes a sawtooth wave having the same cycle as the rotation cycle of the motor 50, and the level indicates the rotation phase information of the motor 50. When the optical disc 1 has a runout due to rotation, the focusing lens 15 follows the runout due to focus control, so the Fc filter 31 outputs a signal synchronized with the rotation period of the motor 50 as shown in FIG. send. Using this periodicity, the drive storage device 68 stores the signal level from the Fc filter 31 while changing the storage address in accordance with the rotational phase information from the rotational phase detector 51. If the motor 50 is stored for a period of one rotation, the stored information can be used repeatedly, so that one cycle of information is sufficient information.
[0064]
When the focus control is in the non-operating state, the drive memory 68 does not perform the memory operation because the signal from the pull-in signal generator 67 is at a low level, and the storage address based on the rotational phase information from the rotational phase detector 51 The stored drive value is obtained from, and sent to the adder 69.
[0065]
Here, the drive signal from the Fc filter 31 when the focus control is in an operating state corresponds to the surface shake of the optical disc 1 in order to make the focus of the light beam follow the information surface. The drive memory 68 stores this drive signal in correspondence with the rotation phase information of the optical disk from the rotation phase detector 51. Therefore, even when the focus control is in a non-operating state, an operation that reduces the surface shake of the optical disc 1 can be performed by using a signal from the drive storage device 68.
[0066]
The focus pull-in operation in the present embodiment will be described with reference to FIGS. 13A shows an example of the output of the FE signal from the FE generator 30, FIG. 13B shows an example of the output of the signal from the search drive generator 64 to the adder 69, and FIG. FIG. 13C shows an example of signal output from the drive selector 32, FIG. 13D shows an example of signal output from the search drive generator 64 to the pull-in signal generator 67, and FIG. ) Is a diagram illustrating an example of a signal output from the pull-in signal generator 67. In FIG. 13, the horizontal axis indicates time, and the vertical axis indicates the level of each signal. The polarity of the signal from the drive selector 32 necessary for the condenser lens 15 to move in the direction approaching the optical disc 1 is the positive direction in FIGS. 13B and 13C. FIG. 14 is a flowchart showing this sequence.
[0067]
In order to operate this sequence, it is a precondition that the focus control is in an operating state. As described above, the drive storage device 68 stores a drive signal corresponding to the surface shake of the optical disc 1 (step S31). The focus control is deactivated (step S32). The driver unit 68 sends a signal for suppressing the influence of the surface blur based on the rotational phase information from the rotational phase detector 51 to the Fc actuator 16 via the adder 69, the drive selector 32, and the Fc driver 33 ( Step S33). Thereby, the position of the condensing lens, that is, the focal point of the light beam changes substantially following the surface vibration of the optical disc 1.
[0068]
The search drive generator 64 outputs to the adder 69 a signal for driving to bring the focal point of the light beam closer to the optical disc 1 as shown in FIG. 13B (step S34). Thereby, a waveform as shown in FIG. 13C is obtained from the drive selector 32. Although this waveform seems to perform a complicated operation at first glance, it is added to the signal from the drive storage device 68 and follows the surface shake of the optical disc 1, so that the relative relationship between the optical disc 1 and the condenser lens 15 is relatively high. The distance decreases at an approximately constant speed.
[0069]
When the signal from the search drive generator 64 to the adder 69 is in the direction in which the condenser lens 15 and the optical disk 1 are approached, as shown in FIG. The signal to becomes low level. Since the signal from the search drive generator 64 is at a low level, the pull-in signal generator 67 always sends a low level signal to the drive selector 32 as shown in FIG. In the drive selector 32, since the signal from the pull-in signal generator 67 is always at a low level, the focus control is always inactive, and the signal from the adder 69 is continuously sent to the Fc actuator via the Fc driver 33.
[0070]
The search drive generator 64 waits until the signal level to the adder 69 reaches L3 (step S35). Therefore, the focal point of the light beam keeps approaching the optical disc 1. As shown in FIG. 13B, when the signal level to the adder 69 reaches the level L3, the search drive generator 64 changes the drive from approach to separation (step S36). The value of the level L3 is set to a value that reliably indicates the state where the focal point of the light beam is located behind the information surface. For this reason, a search is performed from the level L3 to the information surface on which focus control is performed by driving in the separation direction. In addition, since the drive corresponding to the surface shake of the optical disk 1 is output by the output from the drive storage device 68, the condenser lens 15 and the optical disk 1 do not collide due to the influence of the surface shake of the optical disk 1. Further, as shown in FIG. 13D, the signal from the search drive generator 64 to the pull-in signal generator 67 becomes high level.
[0071]
Since the signal from the search drive generator 64 is at a high level, the pull-in signal generator 67 is until the FE signal from the FE generator 30 passes through the reference level from negative to positive as shown in FIG. Wait (step S37). Therefore, the focal point of the light beam continues to be away from the optical disc 1. When the FE signal from the FE generator 30 passes the reference level from negative to positive, a high level signal is sent to the drive selector 32 as shown in FIG. 13E (step S38). When the signal from the pull-in signal generator 67 becomes high level, the drive selector 32 sends the signal from the Fc filter 31 to the Fc driver 33. In this way, focus control can be brought into an operating state.
[0072]
Once the in-focus point is passed and the focus pull-in operation is performed from above the in-focus position, the first appearing FE signal always becomes the information surface, so the reflectance of the surface and the reflectance of the information surface are equivalent. However, the focus is not accidentally drawn into the surface of the optical disc 1. Further, even when the distance from the focal point to the collision position is short, the influence of the surface blur of the optical disk 1 is reduced by the operation of the drive storage unit 68, so that the limit value L 3 of the search drive generator 64 is used to The focus of the light beam passes through the focal point without colliding with the condenser lens 15, and the focus pull-in operation can be performed from a position closer to the disk surface.
[0073]
(Embodiment 4)
FIG. 15 is a block diagram of the optical disk apparatus according to the fourth embodiment. The optical disk apparatus according to the present embodiment includes a surface vicinity detector 61 and an information surface detector 62 in addition to the configuration of the optical disk apparatus according to the third embodiment shown in FIG. The optical disk apparatus includes a photodetector 21 having a wide light detection region shown in FIG. 2 instead of the photodetector 20 shown in FIG.
[0074]
FIG. 16 shows output signal waveforms of main blocks of the optical disc apparatus of the present embodiment. 16A shows an example of the output of the FE signal from the FE generator 30, FIG. 16B shows an example of the output signal from the near-surface detector 61, and FIG. 16C shows the information. FIG. 16D is a diagram showing an example of an output signal from the drive selector 32, and FIG. 16E is an example of an output signal from the pull-in signal generator 63. FIG.
[0075]
In the optical disk device of the present embodiment, when the maximum point of the output signal from the near-surface detector 61 is detected, the signal from the information surface detector 62 changes from low level to high level (see FIG. 16C). ). Thereafter, when the FE signal changes from positive to negative, the signal from the search drive generator 64 to the drive selector 32 is changed from low level to high level, thereby bringing the focus control into the operating state (FIG. 16 (e)). )reference). The above operation is the same as that of the optical disc apparatus of the first embodiment.
[0076]
Here, the optical disk apparatus according to the present embodiment performs driving to bring the condenser lens 15 closer to the optical disk 1 while following the surface blur as shown in the third embodiment. Therefore, the drive selector 32 outputs a signal as shown in FIG. This control is as described in the third embodiment.
[0077]
According to the optical disc of the present embodiment, it is possible to more reliably perform the focus pull-in operation on the information surface of the optical disc 1 while avoiding the collision more reliably.
[0078]
【The invention's effect】
According to the present invention, when the density of an optical disk is increased, the focal point of the light beam and the surface of the optical disk are very close to each other when information is reproduced or recorded, or the reflectance of the information surface is reduced to reduce the surface reflectance. To provide a reliable optical disc apparatus that prevents the condensing lens and the optical disc from colliding, prevents the condensing lens and the optical disc from being damaged, and performs the focus pull-in with high reliability. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc device according to a first embodiment of the present invention.
FIG. 2 is a detailed configuration diagram of a light receiving unit of the photodetector in the first embodiment of the present invention.
3A is a cross-sectional view of an optical disc having a single information recording layer, and FIG. 3B is a cross-sectional view of an optical disc having two information recording layers.
4A is a diagram showing an example of an output of a signal from an FE generator in the first embodiment to a single-layer optical disc, and FIG. 4B is an example of an output of a signal from a reflected light amount detector in the first embodiment. (C) The figure which shows an example of the output of the signal of the near surface detector in Embodiment 1
5A is a diagram showing an example of an output of a signal from an FE generator in the first embodiment, and FIG. 5B is an example of an output of a signal from a reflected light amount detector in the first embodiment. FIG. (C) The figure which shows an example of the output of the signal of the near surface detector in Embodiment 1
6A is a diagram illustrating an example of an output of a signal from an FE generator during a focus pull-in operation in Embodiment 1, and FIG. 6B is an example of an output of a signal from a near-surface detector in Embodiment 1. FIG. 3C is a diagram showing an example of signal output from the information surface detector according to the first embodiment. FIG. 4D is a diagram showing an example of signal output from the drive selector according to the first embodiment. FIG. Showing an example of the output of the signal of the pull-in signal generator in FIG.
FIG. 7 is a flowchart showing the operation of the optical disc apparatus according to the first embodiment.
FIG. 8 is a block diagram showing a configuration of an optical disc device according to a second embodiment of the present invention.
9A is a diagram illustrating an example of signal output from an FE generator in Embodiment 2, FIG. 9B is a diagram illustrating an example of signal output from a near-surface detector in Embodiment 2, and FIG. The figure which shows an example of the output of the internal signal of the separation drive generator in Embodiment 2
FIG. 10 is a flowchart showing the operation of the optical disc apparatus according to the second embodiment.
FIG. 11 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the present invention.
12A is a diagram illustrating an example of a signal output of a rotational phase detector in the third embodiment, and FIG. 12B is a diagram illustrating an example of an output of an Fc filter signal in the third embodiment.
13A is a diagram illustrating an example of an output of a signal of an FE generator during a focus pull-in operation in Embodiment 3, and FIG. 13B is an example of an output of a drive signal of a search drive generator in Embodiment 3. (C) A diagram showing an example of a signal output of the drive selector in the third embodiment, (d) a diagram showing an example of a signal output of the search drive generator in the third embodiment, (e) The figure which shows an example of the output of the signal of the drawing signal generator in the form 3
FIG. 14 is a flowchart showing the operation of the optical disc apparatus according to the third embodiment.
FIG. 15 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the present invention.
FIGS. 16A and 16B are diagrams illustrating an example of an output of an FE generator signal during a focus pull-in operation in Embodiment 4, and FIGS. 16B are diagrams illustrating an example of an output of a near-surface detector signal in Embodiment 4. FIGS. FIG. 4C is a diagram showing an example of signal output from the information surface detector in the fourth embodiment, FIG. 4D is a diagram showing an example of signal output from the drive selector in the fourth embodiment, and FIG. The figure which shows an example of the output of the signal of the drawing signal generator in 4
17A is a block diagram showing a configuration of a conventional optical disc apparatus, and FIG. 17B is a detailed diagram of a light receiving unit of a photodetector in the conventional optical disc apparatus.
18A is a diagram illustrating an example of an output of a signal from an FE generator in a conventional apparatus, and FIG. 18B is a diagram illustrating an example of an output of a signal from a reflected light amount detector in the conventional apparatus.
19A is a diagram illustrating an example of an output of a signal from an FE generator during a focus pull-in operation in a conventional apparatus, and FIG. 19B is a diagram illustrating an example of an output of a signal from a reflected light amount detector in the conventional apparatus. (C) The figure which shows an example of the output of the signal of the drive selector in the conventional apparatus, (d) The figure which shows an example of the output of the signal of the drawing signal generator in the conventional apparatus
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk, 10 Optical head, 11 Laser, 12 Coupling lens, 13 Polarization beam splitter, 14 1/4 wavelength plate, 15 Condensing lens, 16 Fc actuator, 17 Tk actuator, 18 Detection lens, 19 Cylindrical lens, 20, 21 photo detector, 30 FE generator, 31 Fc filter, 32 drive selector, 33 Fc driver, 50 motor, 51 rotational phase detector, 61 surface vicinity detector, 62 information surface detector, 63 pull-in signal generator, 64 Search drive generator, 65 spaced drive generator, 66 Fc control switch, 67 pull-in signal generator, 68 drive memory, 69 adder, 70 reflected light amount detector, 71 pull-in signal generator.

Claims (4)

A converging means for converging and irradiating a light beam toward the rotating information carrier;
Focus moving means for moving the convergence means in the normal direction of the information surface of the information carrier;
A light detecting means having a light receiving region divided substantially concentrically, receiving reflected light from the information carrier, and outputting a signal corresponding to the amount of reflected light;
Based on a signal from the light detection means, a surface vicinity detection means for generating a signal that continuously changes with one maximum point while the focal point of the light beam reaches the information surface from the surface of the information carrier;
Search drive means for generating a drive signal for moving the focal point of the light beam toward or away from the information carrier;
A focus shift signal detection means for generating a signal corresponding to a position shift of the focus of the light beam with respect to the information surface or surface of the information carrier;
A focus control driving means for generating a signal for driving the focus moving means so that the focus of the light beam follows the information surface of the information carrier according to the signal of the focus deviation signal detecting means;
An information surface discriminating means for discriminating whether or not the focal position of the light beam is in the vicinity of the information surface of the information carrier based on the signal from the surface vicinity detecting means and the signal from the focus deviation signal detecting means; ,
A focus pull-in means for selecting one of the signal from the focus control driving means and the signal from the search driving means and supplying the selected signal to the focus moving means in response to a signal from the information surface discrimination means; e,
The width of the light receiving area of the light detection means is the amount of light reflected from the surface of the information carrier detected by the light detection means at the center between the surface of the information carrier and the information surface closest to the surface of the information carrier. And the amount of reflected light from the information surface of the information carrier is larger than the amount of reflected light detected on the surface of the information carrier or the information surface of the information carrier. An optical disc device characterized.   2. The optical disc apparatus according to claim 1, wherein the information surface discriminating unit determines that the focal point of the light beam is in the vicinity of the information surface when the level of the signal from the surface vicinity detecting unit is decreasing. .   The information surface discriminating unit differentiates a signal from the surface vicinity detecting unit, and determines that the focal point of the light beam is in the vicinity of the information surface when the differentiated signal level is negative. 2. The optical disc device according to 2. The light receiving area of the light detecting means is divided into the inside and outside with a predetermined diameter as a boundary, and the surface vicinity detecting means is the sum of the light quantity received by the light receiving area inside the light detecting means and the light quantity received by the outside light receiving area. Configured to detect signals equivalent to
The optical disk apparatus according to claim 1, wherein:

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