JP2008210489A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid collision in playback of any optical disk in a BD/DVD playback apparatus. <P>SOLUTION: The optical disk drive includes: two types of optical beams for playing back a first optical disk and a second optical disk less dense than the first optical disk 100; an optical pickup with focus actuator 203 capable of moving an optical beam spot; and a focus failure detecting section that performs focus control using an electrical signal generated by the optical pickup, compares a signal amplitude obtained by a signal playback section of the first and second optical disks with a predetermined detection level, and detects a failure of the focus control by a decrease in the signal amplitude than the level. The predetermined detection level set in the focus failure detecting section is switched between the first optical disk and the second optical disk. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus for reproducing data recorded on a disc-shaped information carrier (hereinafter referred to as “optical disc”). In particular, the present invention relates to an optical disc apparatus that can set an appropriate defocus detection level and avoid a collision between an objective lens and an optical disc in an optical disc selected from a plurality of types of optical recording discs having different information recording densities. Yes.

  As a conventional optical disk device, when returning from the out-of-focus state, it prevents the objective lens from colliding with the surface of the optical disk and damaging the optical disk, and pulling the focus (the focal position of the light beam from the information recording layer other than the optical disk information It is known to perform control quickly and accurately (focusing on a recording layer) (see Patent Document 1).

  The conventional optical disc apparatus applies an avoidance signal to the focus coil so as to force the objective lens away from the optical disc surface when the focus control is lost when the focal length is shortened, and further returns the focus control. At this time, by setting an avoidance signal based on the detected amount of reflected light, the difference in the loaded optical disk is absorbed.

  The conventional optical disc apparatus applies an avoidance drive signal to the actuator and moves the objective lens in a direction away from the surface of the optical disc, then cancels the application of the avoidance drive signal, and the laser light from the optical disc information recording layer immediately after the release is released. The amount of reflected light (AS signal) is detected. The avoidance drive signal is increased by one step until the detected peak value of the reflected light amount is equal to or less than a predetermined value, and the avoidance drive signal when the peak value is equal to or less than the predetermined value is set as the optimum avoidance drive signal amount. When the focus servo is off, the set avoidance drive signal is applied to the actuator to move the objective lens in a direction away from the optical disc surface, thereby avoiding the objective lens from colliding with the optical disc surface.

  Conventionally, optical disks such as DVD (Digital Versatile Disc) -ROM, DVD-RAM, DVD-RW, DVD-R, DVD + RW, and DVD + R have been put to practical use as high-density and large-capacity optical disks. Also, CD (Compact Disc) is still popular. Currently, development and commercialization of next-generation optical discs such as Blu-ray Discs (hereinafter referred to as BDs) with higher density and larger capacity than these optical discs are being promoted.

  These optical discs have various cross-sectional structures that differ depending on the type. For example, the physical structure of the track, the track pitch, the depth of the information recording layer (the distance from the light incident side surface of the optical disc to the information recording layer), and the like are different. In order to appropriately read or write data from a plurality of types of optical discs having different physical structures in this way, an appropriate wavelength is used by using an optical system having a numerical aperture (NA) corresponding to the type of the optical disc. It is necessary to irradiate the information recording layer of the optical disc with (λ) laser light.

It is known that the recording density of an optical disc is proportional to the square of (NA / λ), and NA and λ are determined according to the recording density of the optical disc. Further, the depth of the information recording layer is determined according to NA and λ. These optical disks have different working recording distances (WD; distance between the objective lens and the optical disk surface) because the depth and NA of the information recording layer differ depending on the type.
JP 2006-24251 A

  However, when trying to reproduce BD and DVD with one optical pickup, the WD when the DVD is loaded into the apparatus is not necessarily wide, but the depth of focus remains deep. In some cases, detection of defocusing is delayed and the optical disk collides.

  For example, in the case of a two-lens configuration as shown in FIG. 6, even when a DVD is played back, the WD is determined by the objective lens 201 on the BD side, and the WD is less than half that of the DVD player (0.5 mm). ). Alternatively, in the single lens configuration as shown in FIG. 7, the focal position of the BD is 0.1 mm from the surface of the optical disk, but in the case of DVD, it is necessary to focus on the position of 0.6 mm from the optical disk surface. An optical element such as the phase ring element 25 intentionally generates aberrations or refracts the DVD-side beam, diverges the light beam to the outside, and then enters the objective lens 20. Therefore, it is necessary to physically bring the objective lens 20 close. Therefore, the WD of the DVD in this case may be narrower than the BD (for example, the DVD is 0.3 mm and the BD is 0.5 mm).

  In either case, the BD / DVD player has a smaller WD than the conventional DVD player, so when the focus control is lost due to external vibration or impact in an in-vehicle environment or the like, the conventional objective lens Detection in time until the 20 and the optical disk collide will not be in time, the collision will occur, the DVD disk without hard coat will be scratched, or the objective lens protector (not shown) made of resin compound will be worn or damaged Thus, there is a problem of scratching the objective lens itself.

  An object of the present invention is to provide an optical disc apparatus capable of detecting out-of-focus promptly and reliably avoiding a collision between the objective lens 20 and the optical disc when reproducing BD and DVD with one optical pickup. It is in.

  An optical disk apparatus according to the present invention includes a light source that emits a light beam to an information recording layer of an optical disk loaded in the apparatus, an objective lens that focuses the light beam, and the objective lens that moves in a direction perpendicular to the disk surface of the optical disk. And an optical pickup that generates an electrical signal based on reflected light from the information recording layer, and is capable of reproducing at least two types of optical discs having different formats. A focus control unit that controls the operation of the focus actuator based on the above, an avoidance pulse output unit that controls the operation of the focus actuator so that the objective lens moves away from the surface of the optical disc, and the amplitude of the electric signal Out of focus from the comparison result between Switching for switching between the focus actuator operation control by the focus control unit and the focus actuator operation control by the avoidance pulse output unit in accordance with the detection result of the defocus detection unit for detecting occurrence and the defocus detection unit And the value of the detection level is changed in accordance with the difference in the format of the optical disc to be reproduced.

  Here, the format refers to the types of optical disks including DVD-ROM, DVD-RAM, DVD-RW, DVD-R, DVD + RW, DVD + R, and BD that realizes higher data density and larger capacity, These optical discs have different recording densities, information recording layer depths, and the like. Further, “out of focus” refers to a state where the focal point of the light beam emitted from the light source is not determined on the information recording layer of the optical disc to such an extent that an electric signal cannot be generated by the optical pickup.

  With this configuration, it is possible to optimally detect out-of-focus when playing back any optical disk with an optical disk playback apparatus that can play back optical disks of different formats.

  In the optical disc apparatus of the present invention, the at least two types of optical discs having different formats include a first optical disc and a second optical disc having different recording densities, and the light source corresponds to the format of the first optical disc. A first light source that emits one light beam and a second light source that emits a second light beam corresponding to the format of the second optical disc, and the detection level of the out-of-focus detection unit is the first detection level. Including a first detection level for detecting defocusing of the optical disc and a second detection level for detecting defocusing of the second optical disc, and the first optical disc is loaded when the first optical disc is loaded. When the second light source and the first detection level are set and the second optical disc is loaded, the second light source and the second detection level are set. Bets are configured to be set.

  With this configuration, it is possible to optimally detect out-of-focus even when the optical disc reproducing apparatus capable of reproducing optical discs having different formats reproduces the first optical disc and the second optical disc having different recording densities. it can.

  The optical disc apparatus according to the present invention further includes a disc discriminating unit for discriminating which optical disc of the different format is the optical disc loaded in the optical disc device, and the focus control is performed when the optical disc apparatus is started up. The detection level is initially set when the operation of the unit is stopped, and the detection level is reset when the focus control unit is operating after disc determination by the determination unit.

  Here, when starting up, the control data recorded on the inner periphery of the optical disk is read from the state in which the optical disk enters the optical disk device and is fixed on the turntable, and then the necessary information is obtained. This refers to the time until standby at a predetermined position.

  With this configuration, it is possible to detect out-of-focus immediately after the start of the focus control operation at the time of activation of the optical disc apparatus, and to detect out-of-focus as accurately as possible even in the recording or reproduction state after the completion of activation.

  In the optical disc device of the present invention, when the disc discriminating unit discriminates that the first optical disc is loaded in the optical disc device, the first light source emits a light beam and the initial setting is executed. When the disc discriminating unit discriminates that the second optical disc is loaded in the optical disc apparatus, the second light source emits a light beam and the initial setting is executed.

  Here, the loading refers to a state in which the optical disk has entered the apparatus and is fixed on the turntable.

  With this configuration, in an optical disc reproducing apparatus capable of reproducing the first optical disc and the second optical disc having different formats, it is possible to reliably detect out-of-focus on any of the optical discs immediately after the start of the focus control operation at startup. it can.

  Further, the optical disc apparatus of the present invention is configured such that the detection level of the out-of-focus detection unit is defined by a decrease rate of the amplitude of the electric signal.

  Here, the rate of decrease in amplitude refers to a ratio representing how much the amount of decrease in electrical signal amplitude is reduced with respect to the peak value, with the peak value of electrical signal amplitude being 100%.

  With this configuration, it is possible to set an optimum detection level without being affected by the peak value of the electric signal amplitude that is different for each optical disc.

  Further, in the optical disc apparatus of the present invention, the detection level is the working distance of the objective lens, the time from when the focus actuator control is released until the defocus detection unit operates, and the acceleration of the objective lens when approaching the optical disc And it was set as the structure set according to the said objective lens acceleration when moving away from the said optical disk.

  With this configuration, it is possible to extremely reduce extra avoidance movement due to erroneous detection of defocusing.

  Further, in the optical disc apparatus of the present invention, the initially set detection level is set based on the electric signal obtained in a state where the rotation operation of the optical disc is stopped, and the reset detection level is the rotation operation of the optical disc. It was set as the structure set based on the said electric signal obtained in the state in which is performed.

  With this configuration, it is possible to detect out-of-focus immediately after the start of the focus control operation at the start without changing the start-up processing procedure, and to accurately detect out-of-focus even in the playback state after the start-up. .

  The optical disc apparatus according to the present invention has a function of quickly generating an avoidance signal and avoiding a collision based on an electrical signal (for example, an RF signal) generated by an optical pickup, even when focus control is lost due to an external impact or the like. When reproducing BD and DVD with one optical pickup, any optical disc can be realized, and a highly reliable optical disc apparatus can be provided.

  FIG. 1 is a perspective view schematically showing the optical disc 100. For reference, FIG. 1 shows an objective lens (focusing lens) 20 and a laser beam 22 focused by the objective lens 10. The laser beam 22 is applied to the information recording layer from the light incident surface of the optical disc 100 to form a light beam spot on the information recording layer.

  The data recorded on the optical disc is reproduced by irradiating the rotating optical disc with a light beam having a relatively weak constant light amount and detecting the reflected light reflected by the optical disc.

  In a reproduction-only optical disc, information by pits is previously recorded in a spiral shape at the manufacturing stage of the optical disc. On the other hand, in a rewritable optical disk, a recording material film capable of optically recording / reproducing data is deposited on the surface of a substrate on which a track having spiral lands or grooves is formed by a method such as vapor deposition. Has been. When data is recorded on a rewritable optical disc, the optical disc is irradiated with a light beam whose amount of light is modulated in accordance with the data to be recorded, thereby changing the characteristics of the recording material film locally to write the data. Do.

The pit depth, track depth, and recording material film thickness are smaller than the thickness of the optical disk substrate. For this reason, the portion of the optical disc where data is recorded constitutes a two-dimensional surface and may be referred to as an “information recording surface”. In the following description, in consideration of the fact that such an information recording surface also has a physical size in the depth direction, instead of using the phrase “information recording surface”, the “information recording layer” Use words. The optical disc has at least one such information recording layer. One information recording layer may actually include a plurality of layers such as a phase change material layer and a reflective layer.

  When data is recorded on a recordable optical disk or when data recorded on such an optical disk is reproduced, the light beam must always be in a predetermined focused state on the target track in the information recording layer. For this purpose, “focus control” and “tracking control” are required. In “focus control”, the position of the objective lens 20 is referred to as the normal direction of the information recording layer (hereinafter referred to as “the depth direction of the substrate”) so that the focal position of the light beam is always located on the information recording layer. Is to control. On the other hand, the tracking control is to control the position of the objective lens 20 in the radial direction of the optical disc (hereinafter referred to as “disc radial direction”) so that the spot of the light beam is located on a predetermined track.

  FIGS. 2A, 2B, and 2C schematically show cross sections of CD, DVD, and BD, respectively. Each optical disk shown in FIG. 2 has a front surface (light incident side surface) 100a and a back surface (label surface) 100b, and has at least one information recording layer 14 between them. On the back surface 100b of the optical disc, a label layer 18 including titles and graphics prints is provided. Each optical disc has a total thickness of 1.2 mm and a diameter of 12 cm. For the sake of simplicity, the concavo-convex structure such as pits and grooves is not shown in the drawing, and the description of the reflective layer is also omitted.

  As shown in FIG. 2A, the information recording layer 14 of the CD is located at a depth of about 1.1 mm from the surface 100a. In order to read data from the information recording layer 14 of the CD, it is necessary to control the near-infrared laser (wavelength: 785 nm) so that the focal point is located on the information recording layer 14. The numerical aperture (NA) of the objective lens used for focusing the laser light is about 0.5.

  As shown in FIG. 2B, the information recording layer 14 of the DVD is located at a depth of about 0.6 mm from the surface 100a. In an actual DVD, two substrates having a thickness of about 0.6 mm are bonded together via an adhesive layer. In the case of an optical disc having two information recording layers 14, the distances from the surface 100a to the information recording layer 14 are about 0.57 mm and about 0.63 mm, respectively, and are close to each other. Therefore, only one information recording layer 14 is shown in the drawing regardless of the number of information recording layers 14. In order to read data from and write data to the information recording layer 14 of the DVD, it is necessary to control the red laser (wavelength: 660 nm) so that the focal point is located on the information recording layer 14. The numerical aperture (NA) of the objective lens used for focusing the laser light is about 0.6.

  As shown in FIG. 2C, the BD is provided with a thin cover layer (transparent layer) 16 having a thickness of 100 μm on the surface 100a side, and the information recording layer 14 is about 0.1 mm from the surface 100a. Located at depth. In order to read data from the information recording layer 14 of the BD, it is necessary to control the blue-violet laser (wavelength: 405 nm) so that the focal point is located on the information recording layer 14. The numerical aperture (NA) of the objective lens used for focusing the laser light is 0.85.

  In such a situation where various optical discs are distributed, it is required that a single optical disc apparatus can record / reproduce many types of optical discs. In order to realize this, the optical disc apparatus needs to have a light source and an optical system that can handle a plurality of types of optical discs, and not all the optical discs loaded in the optical disc apparatus are protected by a hard coat. The collision between the objective lens and the optical disk must be avoided as much as possible.

  FIGS. 3A and 3B are waveform diagrams showing RF signals, which are information signals on an optical disc, in BD and DVD, respectively. This figure shows a state in which the focus control is lost due to an external impact applied to the BD and DVD at point A, but the BD has a large NA of the objective lens 201 as shown in FIG. 0.85) Since the WD is narrow, the depth of focus e is shallow. On the contrary, DVD has a smaller NA (0.6) and wider WD than the BD, and therefore has a deep focus depth f as shown in FIG. 4B. As a result, when the RF signal amplitude characteristic Y with respect to the focus position X is measured as shown in FIG. 5, the amplitude of the BD significantly varies with respect to the defocus as compared with the DVD. Therefore, once the focus control is deviated from the in-focus position, if the same 35% lowering position is set as the detection level, BD can be detected at a high speed of about 0.8 ms, but DVD is 3 ms and its detection time. Becomes longer.

  Therefore, in a single BD / DVD machine, a BD with a narrow WD can be detected quickly and collision can be avoided in front of the optical disc, and a DVD has a slow detection but a wide WD, so the timing of avoidance can be achieved in time. be able to.

  FIG. 8 shows a schematic configuration of the optical disc apparatus of the present invention.

  The optical disc apparatus of the present invention can read data from a plurality of types of optical discs having different information recording densities by generating and irradiating a light beam with objective lenses having different NAs.

  These optical discs have a structure in which data can be recorded and / or reproduced by being irradiated with laser light from the surface side of the optical disc.

  The optical disk apparatus of the present invention is provided with a drive mechanism such as a spindle motor for rotating the loaded optical disk, similarly to an optical disk apparatus such as a known DVD player.

  When one optical disc arbitrarily selected by the user from the above-mentioned plural types of optical discs is loaded into the drive mechanism, the operation described later is executed, and after discriminating the optical disc, focus control and tracking control are performed. It starts in a state where the information signal on the optical disc can be read.

  An optical disc apparatus 1 according to the present invention includes an optical pickup 103 including a semiconductor laser, a light receiving element, an objective lens, a beam splitter combining a semitransparent half mirror and a prism, and a servo control unit 106 that controls the operation of the optical pickup 103. And a reproducing unit 110 that reproduces a signal obtained by reading and converting information recorded on the optical disc 100 with the optical pickup 103.

  The optical pickup 103 irradiates a focused laser beam onto the optical disc 100 loaded on the disc motor 101, and generates an electrical signal based on the amount of light reflected from the optical disc.

  The servo control unit 106 drives the optical pickup 103 with respect to the optical disc 100 loaded in the disc motor 101 to perform focus control and tracking control.

  The reproduction unit 110 converts the electrical signal converted by the optical pickup 103 into a digital signal to be transferred to the host PC or the video / audio unit. The binarization unit 112, the PLL unit 113, the demodulation unit 114, and error correction Part 115.

The electrical signal generated by the optical pickup 103 is equalized by the waveform equalizer 111 to generate an analog reproduction signal. The generated analog reproduction signal is converted into a digital signal by the binarization unit 112 (or after binarization), and the digital signal (or binarization signal) is input to the PLL unit 113. Data is extracted in synchronization with the read clock (reference clock), and is passed through the demodulator 114 and the error corrector 115, and the ECC block is fixed according to the optical disc standard (for example, 182 bytes for DVD-ROM and 155 bytes for BD-ROM). Error correction is performed every time. Thereafter, the data is transferred to the host via the I / F unit 120.

  FIG. 9 shows in more detail the configuration of the servo controller and its peripheral parts in the optical disk apparatus of FIG. Next, it demonstrates in detail using FIG.

  The optical pickup 103 includes a BD NA objective lens 201 for BD, a DVD NA objective lens 202 and two objective lenses, and the two objective lenses 201 and 202 are paired with a focus. The actuator 203 and the tracking actuator 204 are driven.

  The light beam emitted from the blue-violet laser diode 219 passes through the collimator lens 210 and is incident on the deflecting beam splitter 207, the optical path is changed by the deflecting beam splitter 207, and the incident light is incident on the objective lens 201. The light is focused on the information recording layer of the optical disc 100 by 201.

  The reflected light reflected from the optical disc 100 passes through the deflecting beam splitter 207, is narrowed by the detection lens 209 so that the irradiation area becomes a predetermined size, and reaches the quadrant detector 211. Then, it is converted into an electric signal whose magnitude changes in accordance with the amount of irradiation light in each ABCD area of the quadrant detector 211, and this electric signal is amplified by the preamplifiers 222a, 222b, 222c, and 222d, respectively. The amplified electrical signal is processed by adders 223 and 224 and a differential amplifier 225 to generate a focus error signal (FE signal). Simultaneously with the generation of the FE signal, the amplified electrical signal is processed by the adders 223, 224, and 226 to generate an RF signal (RadioFrequency signal). Further, the amplified electrical signal is processed by the adders 223 and 224, the comparators 227 and 228, the phase comparator 229, and the differential amplifier 230 to generate a phase difference tracking error signal (TE signal).

  The FE signal is output via an A / D converter 231 to a focus control unit 301 including a delay device, an amplifier, and an adder in a DSP (Digital Signal Processor) 300. The focus control unit 301 digitally calculates the input signal, converts it into PWM, outputs it to the drive unit 233, amplifies the current in the drive unit 233, drives the focus actuator 203, and the light beam is focused on the information recording layer of the optical disc. Control is performed so that

  Similarly, the TE signal is output via the AD converter 232 to the tracking control unit 302 including a delay device, an amplifier, and an adder in the DSP 300. The tracking control unit 302 performs digital calculation on the input signal, converts it into PWM, outputs it to the drive unit 234, performs current amplification by the drive unit 234, drives the tracking actuator 204, and controls the light beam to scan the track correctly. I do.

  Next, defocus detection and collision avoidance, which are main parts of the present invention, will be described.

  The RF signal output from the adder 226 is input to the DSP 300 via the low pass filter (LPF) 105 and the shaping unit 235.

  Further, the signal is input to the out-of-focus detection unit 304. The out-of-focus detection unit 304 detects out-of-focus by comparing the amplitude value of the input RF signal with a predetermined detection level, and immediately after the detection. In addition to outputting a signal to the avoidance pulse unit 305, a signal is also output to the changeover switch 303, and the connection point is switched so that the contacts AC are connected.

  When receiving a signal from the defocus detection unit 304 as described above, the avoidance pulse unit 305 outputs a square wave pulse having a predetermined voltage and time width to the drive unit via the changeover switch. Then, the focus actuator 203 is driven so that the objective lenses 201 and 202 move in a direction in which the objective lenses 201 and 202 are separated from the optical disc 100.

  FIG. 10 shows a model of this operation. FIG. 10B is a schematic diagram showing the positions of the objective lens and the optical disc in time series, and FIG. 10C is a diagram showing the RF signal at the timing corresponding to FIG. 10B. 10 (d) is a diagram showing a focus drive signal at a timing corresponding to FIG. 10 (b).

  As shown in FIG. 10, in the playback state, when focus control is lost due to an impact from the outside at timing tx, the focus loop remains closed. A driving voltage of a triangular wave T is generated, and the objective lens approaches the optical disc as shown at timings t1 to t2 in FIG.

  Since the focus shifts at this time, the RF amplitude decreases as shown in FIG.

  By detecting this decrease in RF amplitude, out-of-focus is detected. More specifically, out of focus is detected by comparing the amplitude value of the RF signal with a predetermined detection level.

  Here, for example, in the case of a BD, if it is set to detect out-of-focus at a decrease of 35% with respect to the amplitude in the reproduction state and output an avoidance pulse P, the objective lens can be avoided without colliding with the optical disc. Similarly, in DVD, when the out-of-focus detection is performed with a decrease of 35% in the amplitude of the reproduction state, the collision between the objective lens and the optical disk occurs at the detection delay timing t3.

  Therefore, in the case of a DVD, by switching the setting so that defocusing is detected and an avoidance pulse is output when the playback state drops to 55%, defocus detection can be accelerated and collision between the objective lens and the optical disk can be avoided. . FIG. 10A is shown for comparison. Specifically, FIG. 10 (a) also schematically shows the positional relationship between the objective lens and the optical disc in time series, but FIG. 10 (a) shows a case where the control of the present invention is not applied. That is, it shows the positional relationship when the avoidance pulse is not output with good timing, and shows a state in which the objective lens 20 collides with the surface 100a of the optical disc between timings t3 and t4.

  FIG. 11 is a characteristic diagram in which the acceleration at the time of defocusing is measured by the inventor's experiment, and the actual time and distance of the objective lens when defocusing is calculated. The thick solid line indicates the characteristics when the avoidance pulse is not generated, the natural arrival is achieved, the thin solid line indicates the avoidance pulse by the BD to avoid the collision, and the thin dotted line indicates the characteristic when the avoidance pulse is output by the DVD and the collision is avoided. .

When a BD disc is loaded, the blue-violet semiconductor laser 219 emits light, a light beam for BD is formed, focus and tracking control is turned on, and information on the BD disc is reproduced. When the information on the BD disc can be played back, if the detection level of the defocus detection unit 304 (RF signal amplitude reduction rate) is set to level B (about 35% of playback), the detection time is 0.8 ms.

  At this time, as shown in FIG. 11, since the objective lens can be lowered from the position of −0.075 mm or less at the worst with respect to the optical disk surface, it does not collide.

  When a DVD disk is loaded, the red semiconductor laser 205 emits light, a DVD light beam is formed, focus and tracking control is turned on, and information on the DVD disk is reproduced.

  When the information on the DVD disc can be reproduced, the detection level of the out-of-focus detection unit 304 (RF signal amplitude reduction rate) is set to level D (about 55% during reproduction), and the detection time is 1.6 ms. At this time, as shown in FIG. 11, since the objective lens can descend from the position of −0.1 mm or less at the worst with respect to the optical disk surface, it does not collide in the same manner.

  Therefore, in the present embodiment, detection switching is performed between DVD and BD as follows. FIG. 12 is a flowchart showing a start-up process including a process of switching the defocus detection level between BD and DVD in the optical disc apparatus of the present invention.

  When the optical disk is inserted into the apparatus, the blue-violet laser is emitted (S1) and the red laser is emitted sequentially (S3) with the rotation of the optical disk stopped, and converted by the four-division detector 211 at that time. The amplitude value of the signal (hereinafter referred to as AS level) and the amplitude value of the RF signal are detected, and the presence / absence of the optical disk and the discrimination of BD or DVD are performed (S2, S4).

  At this time, the detected RF peak level or AS peak level is held, and based on the BD and DVD discrimination results, in the case of BD, the value is 35% of the peak value, or in the case of DVD, from the peak value. A value of 55% is set as a detection level (S11, S21).

  Thereafter, the optical disk is rotated (S12, S22), a laser matching the loaded optical disk is emitted (S13, S23), and the focus is drawn (S14, S24). After further tracking (S15, S25), after each servo learning (focus position learning, spherical aberration learning, loop gain learning) is performed (S16, S26), the RF or AS amplitude level is measured again (S17). , S27), 35% of the remeasured value in the case of BD, and 55% of the remeasured value in the case of DVD are reset in the out-of-focus detection unit (S18, S28).

  Thereafter, the control data on the inner periphery is read to acquire necessary information, and then the standby is completed at a predetermined position on the inner periphery to complete the activation (S19, S29).

  As described above, once the disc is discriminated, the RF peak is held, the out-of-focus detection level is temporarily set, and when the focus position and other adjustments are completed and the RF amplitude reaches the predetermined amplitude, the measurement is performed again. With this setting, collision can be avoided even when focus control is lost during startup such as immediately after the focus is turned on, and when the playback state is reached, it is possible to detect out-of-focus as accurately as possible. Extra avoidance movement due to detection can be extremely reduced.

In the present embodiment, the detection level in the case of BD is set to 35%, and in the case of DVD to 55%. However, this level is appropriately determined according to the modulation rate of the optical disc signal, the reproduction power, or the WD of each of BD and DVD. What is necessary is just to calculate and set an optimal value.

  That is, the WD differs depending on the type of optical disk, such as BD or DVD, and even for the same BD, the WD varies depending on the configuration of the optical components of the optical pickup. The amount of decrease in the RF signal amplitude with respect to the distance that the light beam deviates from the in-focus position differs depending on the BD, DVD, and optical pickup. Therefore, within a certain WD range, when the objective lens is accelerated, a certain acceleration in the direction away from the optical disk is applied to the objective lens from the state approaching the optical disk surface, and the objective lens can be moved away without colliding with the optical disk surface. It is mainly determined by “WD”, “time from when the focus control is lost to when the defocus detection unit operates”, “objective lens acceleration when approaching the optical disk”, and “objective lens acceleration when moving away from the optical disk”.

  The “time from when focus control is lost to when the defocus detection unit operates” detects defocusing at the rate of decrease in the RF signal amplitude, so “objective lens acceleration when approaching the optical disk” and “light It is determined by “a decrease amount of the RF signal amplitude with respect to a distance that the beam is deviated from the in-focus position” and “how much when the RF signal amplitude is decreased is to be detected as out of focus”. From these, a value that can be avoided without causing the objective lens to collide with the optical disk is calculated, and the “time from when the focus control is lost until the defocus detection unit operates” may be set.

  In this embodiment, the detection level is set by reducing the amplitude of the RF signal, but the focus is not caused by the decrease of the total light amount signal of the photodetector or the arrival of the focus error signal at a predetermined level, instead of the RF signal. It is also possible to detect disconnection, and this configuration can be applied not only to a reproduction-only device but also to a recording device that records a signal on an optical disc such as a recordable BD-RE, DVD-RW, or RAM. Is possible.

  Further, the present embodiment has been described by taking an example of an apparatus for reproducing a BD disc and a DVD disc. However, in an apparatus for reproducing or recording a CD in addition to the BD and DVD mounted with an infrared laser, the BD and DVD are also provided. , A detection level of defocusing corresponding to each WD and focal depth or focus range may be set in advance on the CD. Even in such a case, the effect of the present invention is the same.

  There are provided an optical disc apparatus capable of reproducing various optical discs such as CDs, DVDs, and BDs manufactured based on various standards and a driving method thereof. The optical disk apparatus of the present invention is equipped with an optical pickup with a narrow working distance (WD) equipped with an objective lens having a large NA, particularly for reproducing BD, and is capable of focus control by external vibration and impact in an in-vehicle environment. Even if the lens comes off, it exerts a remarkable effect on the collision and scratches of the objective lens, which greatly contributes to the spread of the next generation optical disc.

A perspective view schematically showing the optical disc 100 (A) Cross-sectional view schematically showing the cross-section of the CD (b) Cross-sectional view schematically showing the cross-section of the DVD (c) Cross-sectional view schematically showing the cross-section of the BD (A) Diagram showing RF waveform when focus control is lost during BD playback (b) Diagram showing RF waveform when focus control is lost during DVD playback (A) Cross-sectional view schematically showing an objective lens and light beam for explaining NA, WD, and depth of focus in BD (b) Objective lens and light beam for explaining NA, WD, and depth of focus in DVD Cross-sectional view schematically Characteristic diagram showing RF amplitude change with respect to the focus position of BD and DVD Sectional view schematically showing a two-lens method in a BD and DVD playback compatible machine (A) Cross-sectional view schematically showing a single lens system in a BD playback compatible machine (b) Cross-sectional view schematically showing a single lens system in a DVD playback compatible machine 1 is a block diagram showing a configuration of an optical disc apparatus according to an embodiment of the present invention. 1 is a detailed block diagram showing a configuration of a servo control unit and its periphery of an optical disc apparatus according to an embodiment of the present invention In the embodiment of the present invention, the timing diagram showing the positional relationship between the objective lens and the optical disc and the corresponding RF signal and focus drive signal In the embodiment of the present invention, the characteristic diagram which calculated the time and distance of the actual objective lens when defocusing The figure which shows the starting process in embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 10 Objective lens 12 Laser beam 14 Information recording layer 16 Cover layer (transparent layer)
18 Label layer 25 Phase ring element 100 Optical disc 101 Disc motor 102 Drive unit 103 Optical pickup 105 Low pass filter (LPF)
106 Servo Control Unit 110 Reproduction Unit 111 Waveform Equalizer 112 Binarization Unit 113 PLL Unit 114 Demodulation Unit 115 Error Correction Unit 120 I / F Units 201 and 202 Objective Lens 203 Focus Actuator 204 Tracking Actuator 205 Blue Purple Laser Diode 206 Collimator Lens 207 Deflection beam splitter 208 Detection lens 211 Quadrant detector 222 Preamplifier 223, 224, 226 Adder 225, 230 Differential amplifier 227, 228 Comparator 229 Phase comparator 231, 232 AD converter 233, 234 Drive unit 235 Shaping unit 300 DSP
301 Focus Control Unit 302 Tracking Control Unit 303 Changeover Switch 304 Defocus Detection Unit 305 Avoidance Pulse Unit

Claims (7)

A light source that emits a light beam to an information recording layer of an optical disc loaded in the apparatus, an objective lens that focuses the light beam, and a focus actuator that moves the objective lens in a direction perpendicular to the disc surface of the optical disc An optical disc apparatus comprising an optical pickup that generates an electrical signal based on reflected light from the information recording layer, and capable of reproducing at least two types of optical discs having different formats,
A focus control unit that controls the operation of the focus actuator based on the electrical signal;
An avoidance pulse output unit for controlling the operation of the focus actuator so that the objective lens moves in a direction away from the surface of the optical disc;
An out-of-focus detection unit that detects that out-of-focus has occurred based on a comparison result between the amplitude of the electrical signal and a predetermined detection level, and the operation of the focus actuator by the focus control unit according to the detection result of the out-of-focus detection unit A switching unit that switches between control and operation control of the focus actuator by the avoidance pulse output unit,
An optical disc apparatus characterized in that the value of the detection level is changed according to a difference in the format of an optical disc to be reproduced.   The at least two types of optical discs having different formats include a first optical disc and a second optical disc having different recording densities, and the light source emits a first light beam corresponding to the format of the first optical disc. The detection level of the defocus detection unit detects a defocus of the first optical disc, and a second light source that emits a second light beam corresponding to the format of the second optical disc. A first detection level and a second detection level for detecting defocusing of the second optical disc, and when the first optical disc is loaded, the first light source and the first detection level. And when the second optical disk is loaded, the second light source and the second detection level are set. The optical disk apparatus according to Motomeko 1.   A disc discriminating unit for discriminating which optical disc of the different format is an optical disc loaded in the optical disc apparatus, and when the operation of the focus control unit is stopped at the start of the optical disc apparatus, 2. The optical disc apparatus according to claim 1, wherein initial setting is performed and the detection level is reset after the discriminating unit discriminates and the focus control unit operates.   When the disc discriminating unit discriminates that the first optical disc is loaded in the optical disc apparatus, the first light source emits a light beam and initial setting is performed, and the disc discriminating unit sends the optical disc unit to the optical disc unit. 4. The optical disc apparatus according to claim 3, wherein when it is determined that a second optical disc is loaded, the second light source emits a light beam and the initial setting is executed.   The optical disc apparatus according to any one of claims 1 to 4, wherein the detection level of the defocus detection unit is defined by a decrease rate of an amplitude of the electric signal.   The detection level includes a working distance of the objective lens, a time from when the focus actuator control is released to when the defocus detection unit operates, an acceleration of the objective lens when approaching the optical disc, and the objective when moving away from the optical disc. 6. The optical disk apparatus according to claim 5, wherein the optical disk apparatus is set according to lens acceleration. The initially set detection level is set based on the electrical signal obtained when the optical disc rotation operation is stopped, and the reset detection level is obtained when the optical disc rotation operation is being executed. The optical disk apparatus according to claim 6, wherein the optical disk apparatus is set based on the electrical signal.

Images