Patent Application
20130155824
The present application claims priority from Japanese applications JP2011-272916 filed on Dec. 14 2011, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention pertains to an optical disc device that, using a laser, plays back information from an optical disc or records information on an optical disc, and a method of recording onto an optical disc.
2. Description of the Related Art
In recent years, as far as optical discs of the Bluray Disc™ Standard are concerned, there have been developed optical discs having three or four recording layers in order to increase the recording capacity. From now on, it is considered to carry out recording and playback on optical discs having a higher number of recording layers as a method of implementing further increases in capacity.
E.g., in JP-A-2008-97694, there is disclosed an optical disc (below referred to as a “grooveless optical disc”) according to a scheme in which a layer (below referred to as a “guide layer”) having a physical groove structure for carrying out tracking servo control is provided and multiple recording layers are stacked without creating a land/groove structure in the layers carrying out recording and playback (below referred to as “recording layers”), manufacturing thereof being taken to be easy even in the case where multiple recording layers are stacked.
Also in the case of carrying out recording using a guide layer and a recording layer, there are JP-A-2010-40093 and JP-A-2009-140552 as methods of providing an area e.g. called a guard track with respect to the existing recording track and carrying out additional data recordings. Specifically, in JP-A-2010-40093 and JP-A-2009-140552, in the case of carrying out recording using a guide layer and a recording layer, a previous recording area and an additional recording area are separated and overwriting is prevented by providing an area called e.g. a “guard track” with respect to the previous recording track.
As one problem arising on the occasion of recording and playing back a grooveless disc such as mentioned above, there can be cited the problem that a positional misalignment is produced between the guide layer and the recording layer if there occurs a tilt in the optical disc, E.g., as shown in
E.g., in the aforementioned reference JP-A-2009-140552, since the guard track part is in an unrecorded state, tracking control is temporarily turned off before the guard track in the case of attempting to continuously generating a previously recorded area and an additional recording area, and the light spot is moved by just the distance corresponding to the guard track, so there is a need, all over again, to turn on tracking control, play back the addresses, and effectuate repositioning. If, at this point, the scope of the previously recorded area of the destination of movement is narrow, it becomes difficult to reposition the light spot. On the occasion of jumping across the guard tracks to move the light spot, it is necessary to move the optical system by means of an actuator such as a stepping motor, but the accuracy thereof is on the order of hundred microns. As against this, in the case of the Blu-ray Disc™ Standard, the track pitch is 0.32 microns, and if only some one hundred tracks are recorded, the width of the previously recorded area works out to 32 microns, so light spot positioning based on a stepping motor becomes difficult, Also, since there is a misalignment (eccentricity), in the optical disc, between the axis of rotation and the optical disc center, positioning to a narrow previously recorded area becomes even more difficult.
The present invention has for an object to furnish an optical disc device that, for a grooveless disc, safely positions light spots with respect to a recorded area recorded on account of an addition of data.
The aforementioned problem is improved upon by the invention according to the patent claims. As an example, it is e.g. attained, in an optical disc device having a first optical system that, with respect to an optical disc formed by being provided with a guide layer having a physical groove structure for carrying out tracking servo control and stacking recording layers carrying out recording and playback, focuses a light beam on the guide layer and detects reflected light therefrom; and a second optical system that focuses a light beam on a recording layer and detects reflected light therefrom. there being a recorded area and an unrecorded area in the recording layer, by taking an additional data recording by the second optical system to be possible to implement in the case where the recording capacity of the unrecorded area is equal to or greater than a prescribed threshold value, and taking an additional data recording with respect to the concerned recording layer to be impossible to implement when it is less than the threshold value.
According to the present invention, it becomes possible to safely position light spots with respect to a recording area in which data have been recorded additionally, for a grooveless disc.
Other objects, features, and advantages of the present invention will become apparent from the following description of embodiments of the present invention provided in relation to the accompanying drawings.
Hereinafter, an embodiment o he present invention will be described based on the drawings.
The structure of optical disc 102 is illustrated by example in
In
Optical pickup 203 comprises two optical systems with different wavelengths such as e.g. 405 nm and 650 nm. First, a description will be given regarding the 405 nm optical system during playback. A laser driver 301 is controlled by controller 201 and outputs a current driving a laser diode 302. As for this drive current, a radio frequency weighting of several hundred MHz is impressed in order to suppress the laser noise. Laser diode 302 emits laser light with a wavelength of 405 nm having a waveform corresponding to the drive current. The emitted laser light becomes parallel light in a collimator lens 303, a part thereof being reflected in a beam splitter 304 and condensed in a power monitor 306 by means of a condensing lens 305. Power monitor 306 feeds back a current or voltage, corresponding to the intensity of the laser light, to controller 201. In this way, the intensity of the laser light collected on the recording layers of optical disc 102 is maintained at a desired value, such as e.g. 2 mW, On the other hand, the laser light transmitted through beam splitter 304 is reflected in a polarizing beam splitter 307 and convergence and divergence are controlled by means of spherical aberration compensation element 309 driven by an error signal compensation drive unit 206. The laser light transmitted through spherical aberration compensation element 309, after being transmitted through a dichroic mirror 308, becomes circularly polarized light in a quarter-wave plate 310 and is collected on the recording layers of optical disc 102 by means of an objective lens 311. This dichroic mirror 308 is an optical element that reflects light having a specified wavelength and transmits light having other wavelengths. Here, it is taken to be one that transmits light with a wavelength of 405 nm and reflects 650-nm light. Objective lens 311 is positionally controlled by means of actuator 312. The laser light reflected by optical disc 102 is modulated in intensity in response to information recorded in optical disc 102. It becomes linearly polarized light in quarter-wave plate 310 and is transmitted, via dichroic mirror 308 and spherical aberration compensation element 309, through polarizing beam splitter 307. The transmitted laser light is collected on a detector 314 by means of a condensing lens 313. Detector 314 detects the intensity of the laser light and outputs a signal corresponding hereto to signal processing part 202. Signal processing part 202 carries out processing such as amplification, equalization, and decoding with respect to the playback signal output from detector 314 and outputs the decoded data to controller 201. Controller 201 outputs the data to host 103.
Also, a focus error signal generation unit 211 generates a focus error signal with respect to the recording layers, from the signal output from detector 314. By means of a command signal from controller 201, a focus control unit 212 outputs a focus drive signal corresponding to the focus error signal to a focus drive unit 213. The focus drive unit 213, in response to the focus drive signal, drives actuator 312 in a direction perpendicular to the disc surface. As mentioned above, due to the fact that the focus control unit 212 and the focus drive unit 213 operate, focus control is carried out so that the laser spot irradiated on a recording layer of optical disc 102 is continually focused on the recording layer.
On the occasion of carrying out recording, recording data are input from host 103 to controller 201. Controller 201 outputs a recording waveform corresponding to the input data to laser driver 301. Laser driver 301 outputs a drive current corresponding to the recording waveform to laser diode 302 and recording is carried out in a recording layer of optical disc 102 by irradiating laser light with a waveform handled by laser diode 302.
Next, there will be given a description regarding the 650-nm optical system. Regarding the present optical system, there is no difference in operation during recording and during playback. In the same way as the 405-nm optical system, laser driver 301 drives a laser diode 315 and laser diode 315 irradiates laser tight with a wavelength of 650 nm. A part of the laser light passes through a collimator lens 316, a beam splitter 317, and a condensing lens 318, the power being monitored in a power monitor 319. By feeding back the monitored power to controller 201, the intensity of the laser light collected in the guide layer of optical disc 102 is maintained at a desired power, such as e.g. 3 mW. The laser light transmitted through beam splitter 317 is transmitted through a polarizing beam splitter 320, the control of convergence/divergence and position being carried out in a relay lens 321. The laser light having passed through relay lens 321 is reflected in dichroic mirror 308. passes through quarter-wave plate 310 and is collected in the guide layer of optical disc 102 by means of objective lens 311. The laser light reflected in optical disc 102 is reflected in polarizing beam splitter 320 and is collected in a detector 323 with a condensing lens 322.
Relay lens error signal generation unit 217 generates, from the signal output from detector 323, a relay lens error signal which is an error signal for the focus direction and tracking direction with respect to the guide layer of optical disc 102. Relay lens control unit 218 generates a relay lens drive signal in response to the relay lens error signal by means of a command signal from controller 201. Relay lens drive unit 219 drives relay lens 321 in response to the relay lens drive signal and positions the laser spot on the guide layer.
Also, as for slider drive unit 205, aberration compensation drive unit 206, and spindle control unit 209 as well, there is operation by means of a command signal from controller 201.
Further, the same laser driver 301 was used here for driving laser diode 302 and laser diode 315, but it is also acceptable to provide individual laser drivers for the respective laser diodes. Also, spherical aberration compensation element 309 may be arranged in a position that has an influence on both the 405-nm optical system and the 650-nm optical system and may e.g. be arranged between quarter-wave plate 310 and dichroic mirror 308.
Next, there will be given a description regarding the tracking control. In the 405-nm optical system, tracking error signal generation unit 214 generates, from the signal output by detector 314, a tracking error signal with respect to a recording layer of optical disc 102. Also, in the 650-nm optical system, tracking error signal generation unit 214 generates, from the signal output from detector 323, a tracking error signal with respect to the guide layer of optical disc 102. Tracking control unit 215 selects a tracking error signal generated in the 405-nm optical system or the 650-nm optical system and generates a tracking drive signal corresponding to the error signal by means of a command signal from controller 201. Tracking drive unit 216 drives actuator 312 in the radial direction of the disc in response to the tracking drive signal. Further, since actuator 312 is jointly used by the 405-nm optical system and the 650-nm optical system, even in the case of controlling actuator 312 with a tracking error signal generated by one of the optical systems, the laser spot of the other optical system moves in a radial direction of optical disc 102.
Also, a relay lens drive signal corresponding to the error signal is generated from the command signal from controller 201 by relay lens control unit 218 by means of the tracking error signal generated by the 650-nm optical system. Relay lens drive unit 219 drives relay lens 321 in response to the relay lens drive signal to control the movement of the laser spot in a radial direction of the disc. In this case, the relay lens 321, since it is arranged in the 650-nm optical system, has the possibility of carrying out tracking control independently of the 405-nm optical system.
Next, a description will be given, by means of
It is judged by the following method whether an additional recording is carried out after previous recording track 1. In the case where the capacity of the unrecorded area after previous recording track 1 is equal to or less than the required capacity to generate a guard track, an additional recording is taken to be impossible to implement because the guard track cannot be generated.
Also, if the number of guard tracks is taken to be n, the track pitch is taken to be Tp, the amount of optical disc eccentricity is taken to be d, the recording capacity per unit recording width of a radial position in the proximity of the unrecorded area is taken to be A, and the recording capacity of the unrecorded area is taken to be R, in the case where
R<A×(n·Tp+d)
is satisfied, additional recording is taken to be impossible to implement even if the capacity of the unrecorded area is greater than the capacity required to generate a guard track, since the radial direction width of previous recording track 2 is narrow. E. g., when
R=A×(n·Tp+d),
even if the additional recording is carried out on all of the unrecorded area after the guard track, the width in the radial direction of a previous recording track 2 to be generated becomes d. Since the optical disc rotates having an eccentricity amount d, even if the optical pickup is fixed, the result is that the light spot on the optical disc, due to rotation, traverses previous recording track 2 from end to end. If, further, the width of previous recording track 2 becomes less than d. then there will necessarily arise, during rotation of the optical disc, a range in which the light spot will deviate from previous recording track 2. Accordingly, since it is not possible to ensure sufficient recording area width, it is taken to be impossible to implement an additional recording.
In addition, in the case where a stepping motor is used as the slider motor for optical pickup movements, if the movement quantity per pulse of the stepping motor is taken to be c, even in the case where
R<A×(n·Tp+d+c)
is satisfied, additional recording is taken to be impossible to implement, since the radial direction width of previous recording track 2 is narrow. Since the stepping motor rotates in a step-like manner by unit pulse, the movement of optical pickup also becomes step-like. Because of this, in the case of using a stepping motor, the accuracy of positioning is insufficient with a previous recording track 2 width of d, so a width of (d+c) taking into account the movement quantity c per pulse becomes necessary. As for the aforementioned eccentricity amount d, there may be used a value actually measured for each optical disc, but if the maximum allowable value of the specification value defined in the concerned optical disc system is used, handling with respect to eccentricity can be effectuated easily. Further, in the case where it is impossible to implement recording onto the concerned recording layer, and in the case where there is a recording area that can be recorded in another recording layer, recording may be continued in the other layer.
Further, the present invention is not one limited to the aforementioned embodiment, different variations being included therein. E.g., the aforementioned embodiment is one described in detail to explain the present invention in an easily comprehensible way, but it is not necessarily one comprising the entire described configuration.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-272916 | Dec 2011 | JP | national |
