JP3923029B2 - Optical disk playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk reproducing apparatus that reproduces information recorded on an optical disk, and more particularly to a three-beam optical disk reproducing apparatus that uses three light beams of a main beam and two sub beams.
[0002]
[Prior art]
Conventionally, a three-beam type optical disk reproducing apparatus is provided with a tracking servo mechanism that performs control for causing a laser beam emitted from an optical pickup to follow a track of an optical disk. The optical pickup irradiates the main beam with the center of the track of the optical disk as a target, and irradiates two sub beams with both edges of the track as targets, receives the return light from the optical disk, and electrically transmits the return light. It is configured to convert the signal into an RF signal.
[0003]
For example, as shown in FIG. 6, the optical pickup irradiates the main beam A with the center of the track T of the optical disk as a target, and irradiates the sub beam B with one edge of the track T as a target. The sub-beam C is irradiated with the other edge as a target. The optical pickup outputs a signal obtained by converting the return light of the main beam A into an electric signal as a signal indicating information recorded on the optical disc. The optical pickup outputs a sub beam return signal b obtained by converting the return light of the sub beam B into an electric signal and a sub beam return signal c obtained by converting the return light of the sub beam C into an electric signal. The sub beam return signal b and the sub beam return signal c are used to generate a tracking error signal (tracking error signal) for the optical pickup to follow the track on the optical disc.
[0004]
FIG. 7 shows a comparator 60 included in the tracking error signal generating means. The non-inverting input terminal 61 of the comparator 60 receives the sub-beam return signal b, and the inverting input terminal 62 receives the sub-beam return signal c. Is entered. As a result, a tracking error signal (tracking error signal) that is the difference between the sub-beam return signal b and the sub-beam return signal c is output from the output terminal 63 of the comparator 60. When the main beam A irradiates the center of the track T, that is, when the sub beams B and C are applied to the track T by the same amount and return the same light amount, the tracking error signal output from the comparator 60 becomes 0V.
[0005]
When the main beam A is shifted to the right as viewed from FIG. 6 from the center of the track T, the amount of return light of the sub beam B is smaller than the amount of return light of the sub beam C. The voltage level of the sub beam return signal b input to the input terminal 61 is lower than the voltage level of the sub beam return signal c input to the input terminal 62. As a result, the voltage of the tracking error signal output from the output terminal 63 is Negative voltage.
[0006]
On the contrary, when the main beam A is shifted leftward from the center of the track T as viewed from FIG. 6, the light amount of the return light of the sub beam B becomes larger than the light amount of the return light of the sub beam C. The voltage level of the sub beam return signal b input to the input terminal 61 is higher than the voltage level of the sub beam return signal c input to the input terminal 62. As a result, the voltage of the tracking error signal output from the output terminal 63 is increased. Becomes a positive voltage.
[0007]
The tracking error signal output from the comparator 60 in this way is supplied to the servo circuit, and the position of the optical pickup is controlled so that the voltage level of the tracking error signal becomes 0V. That is, the position of the optical pickup is controlled so that the main beam A from the optical pickup irradiates the center (center) of the track T. In this way, the conventional optical disk reproducing apparatus traces the main beam A from the optical pickup so as to pass through the center of the track T, thereby reliably reading the information signal written on the optical disk with the main beam A, and performing the best reproduction. Gains ability status (playability) to minimize jitter.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-96465
[Problems to be solved by the invention]
However, in the conventional optical disk reproducing apparatus, the tracking servo is controlled so that the main beam from the optical pickup irradiates the center of the track of the optical disk so that the best reproduction capability state is possible. In order to perform such control with high accuracy, for example, as shown in FIG. 2, it is assumed that both ends of the track T are symmetrical with respect to the center H of the track T. If there is an optical disc with the center of the track shifted, for example, if there is a convex portion 31 at the edge of the track T as shown in FIG. 3, or there is a concave portion 32 at the edge of the track T as shown in FIG. Is not symmetrical, and in this case, the main beam from the optical pickup does not trace the complete center of the track T, which causes a problem that the best reproduction capability state cannot be obtained.
[0010]
Note that the optical information recording / reproducing apparatus described in Patent Document 1 forms an image of a light beam from a laser on an information track of an information recording surface as a minute light spot via a projection optical system, and from the information recording surface. The reflected light / transmitted light is guided to the first photodetector via the light receiving optical system, and information is recorded and reproduced on the information recording surface. For example, in the light path of the light projecting optical system A beam splitter that extracts a part of the light beam, and a second photodetector that is divided by at least a dividing line in the information track vertical direction in order to detect the extracted light beam.
[0011]
According to the optical information recording / reproducing apparatus having this configuration, a minute light spot is imaged on the center of the track on the track of the disk, and the symmetry of the light spot with respect to the parallel direction of the track is detected. Symmetric error signals are used as tracking error signals. However, since this optical information recording / reproducing apparatus forms only one light spot on the track, as shown in FIG. 6, the main beam A, the sub beam B, and the sub beam C are irradiated onto the track T of the optical disk. However, unlike the configuration of the three-beam type optical disk reproducing apparatus that generates the tracking error signal by the return light of the sub beam B and the return light of the sub beam C, the tracking servo accuracy is higher than that of the three-beam type optical disk reproducing apparatus. In addition, it does not solve the above-described problems described in the conventional three-beam type optical disk reproducing apparatus.
[0012]
The present invention has been made to solve the above-described problems, and provides an optical disc playback apparatus that can obtain the best playback capability state even if the tracks on the optical disc are not symmetrical. With the goal.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention irradiates the main beam with the center of the track of the optical disk as a target, and irradiates two sub beams with the two edges of the track as targets, respectively, and receives the return light from the optical disk A signal processing circuit that includes an optical pickup, changes a light amount of at least one of the two sub beams, and determines a light amount of the sub beam based on a jitter measurement result measured according to the changed light amount of the sub beam; Provided is an optical disk playback device characterized by comprising the above.
[0014]
In this configuration, if the light quantity of at least one of the two sub-beams emitted from the optical pickup is changed, the jitter also changes. Therefore, the jitter corresponding to the changed light quantity of the sub-beam is measured. For example, the jitter is minimized. Determine the light quantity of the sub beam when. By using a sub-beam whose amount of light is determined in this way, jitter can be minimized even when an optical disc whose tracks are not symmetrical is reproduced, and therefore stable performance and the best reproduction capability state (Playability) is obtained, and the reproduction accuracy is improved.
[0015]
Further, the present invention irradiates the main beam with the center of the track of the optical disk as a target, and irradiates two sub beams with the both edges of the track as targets, respectively, and returns the return light of the main beam and the return light of the two sub beams An optical pickup for receiving light, a reproducing means for reproducing recorded information on the optical disk based on the received return light of the main beam, a jitter measuring means for measuring jitter based on the returned light of the received main beam, Tracking error signal generating means for generating a tracking error signal for tracking servo based on return light of two sub beams, sub beam light quantity changing means for changing the light quantity of at least one of the two sub beams, and the sub beam Sub-beam light quantity by means of light quantity variable means To provide an optical disc reproducing apparatus being characterized in that a sub-beam light amount determining means for determining the amount of the sub-beams on the basis of the jitter measurement results measured by the jitter measuring unit in accordance with the reduction.
[0016]
In this configuration, recorded information on the optical disk is reproduced by the reproducing means based on the return light of the main beam received by the optical pickup. Further, the jitter is measured by the jitter measuring means based on the return light of the main beam received by the optical pickup. Furthermore, a tracking error signal is generated by the tracking error signal generation means based on the return lights of the two sub beams received by the optical pickup. The light quantity of at least one of the two sub-beams is changed by the sub-beam light quantity varying means, and the jitter corresponding to the changed light quantity of the sub-beam is measured by the jitter measuring means. For example, the light quantity of the sub-beam when the jitter is minimized Is determined by the sub-beam light quantity determining means. By using a sub-beam whose amount of light is determined in this way, jitter can be minimized even when an optical disc whose tracks are not symmetrical is reproduced, and therefore stable performance and the best reproduction capability state (Playability) is obtained, and the reproduction accuracy is improved.
[0017]
Preferably, when the optical disk to be reproduced changes, the light amount of the sub-beam is adjusted based on the jitter measurement result, so that a stable performance and the best reproduction ability state (playability) are always obtained regardless of the optical disk. Is possible.
[0018]
Preferably, when a predetermined condition is reached, the light amount of the sub-beam is adjusted based on the jitter measurement result, so that it is possible to always obtain stable performance and the best reproduction capability state (playability).
[0019]
Since the predetermined condition is when the jitter is deteriorated from a predetermined value, when the jitter is deteriorated, the light quantity of the sub beam is adjusted to obtain stable performance and the best reproduction ability state (playability). It becomes possible.
[0020]
Preferably, the light amount of the sub-beam determined based on the jitter measurement result is the light amount of the sub-beam when the jitter is minimized, so that the jitter can be minimized, stable performance and the best reproduction capability It becomes possible to obtain the state (playability).
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of an optical disc reproducing apparatus according to an embodiment of the present invention. In FIG. 1, this optical disk reproducing apparatus irradiates a recording surface of an optical disk 1 such as a CD (Compact Disk) or a DVD (Digital Versatile Disk) as a recording medium with laser light (a main beam and two sub beams) and an optical disk 1. An optical pickup 2 that receives the return light from the optical disk 2 and outputs a read signal, a spindle motor 3 that rotates the optical disk 1, a slide mechanism 4 that slides the optical pickup 2 in the radial direction of the optical disk 1, and the spindle motor 3 and the slide A motor driver 6 that drives the mechanism 4 and drives a mechanism that performs focusing and tracking of the optical pickup 2 with respect to the track on the optical disc 1 is provided.
[0022]
In addition, the optical disk reproducing apparatus reads the recorded information on the optical disk 1 and amplifies the RF signal output from the optical pickup 2, and inputs the RF signal from the RF amplifier 5 to perform predetermined signal processing. And a signal processing circuit 9 for performing the processing. The signal processing circuit 9 receives the RF signal from the RF amplifier 5 based on the return light of the main beam, separates the data and the synchronization signal, performs error checking by decoding the separated data, and the data If there is an error in the data, error correction is performed to create correct data, and further, reproduction means 16 is provided for decoding the correct data and outputting a video signal and an audio signal.
[0023]
Further, the signal processing circuit 9 includes a jitter measuring means 15 for measuring jitter by an RF signal from the RF amplifier 5 based on the return light of the main beam received by the optical pickup 2, and an RF based on the return light of the two sub beams. Tracking error signal generating means 13 for generating a tracking error signal for tracking servo for the optical pickup 2 from the RF signal from the amplifier 5; and focusing error signal for focusing servo for the optical pickup 2 by the RF signal from the RF amplifier 5. A focusing error signal generating means 14 for generating a light beam, a sub-beam light quantity varying means 12 for varying the light quantity of at least one of the two sub-beams, and a sub-beam light quantity varying means 12 according to a change in the light quantity of the sub-beam. And a sub-beam light amount determining means 11 for determining the amount of the sub-beams on the basis of the the jitter measurement results measured by the measuring means 15.
[0024]
In addition, this optical disk reproducing apparatus inputs an RF signal from the RF amplifier 5 and a servo signal (such as a tracking error signal or a focusing error signal) from the signal processing circuit 9, and controls the motor driver 6 according to the RF signal and the servo signal. A servo circuit 7 to be driven is provided. The optical disk reproducing apparatus also includes a control microcomputer (microcomputer) 8 that controls the servo circuit 7 and the signal processing circuit 9.
[0025]
Hereinafter, in the optical disk reproducing apparatus having such a configuration, the sub beam light amount adjusting operation, which is a feature of the present embodiment, will be described. In order to read the information recorded on the track of the optical disk 1 by the optical pickup 2, the main beam A is arranged at the center of the track T as shown in FIG. Sub-beams B and C for irradiating are arranged. In order for the main beam A emitted from the optical pickup 2 to pass through the center (center) of the track T, the amounts of return light from the sub-beams B and C are equal, and the tracking error signal (tracking error signal) is 0 ( The voltage is controlled to be 0).
[0026]
Under the condition that the tracking error signal is controlled to be 0 in this way, of the sub-beams B and C, the sub-beam light quantity varying means 12 makes the emitted light quantity of one sub-beam relative to the emitted light quantity of the other sub-beam. The jitter is measured by the jitter measuring means 15.
[0027]
For example, the amount of light emitted from the sub beam B is constant E, and the amount of light emitted from the sub beam C is αE (where α = 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1. When 3), the jitter is measured by the jitter measuring means 15. ΑE represents α × E. By the measurement, the amount of light emitted from the sub beam C when the jitter is minimized is fixed as an optimum value for tracing the center of the track T. That is, the sub-beam light quantity determining means 10 measures the measurement result (when the jitter is minimized) measured by the jitter measuring means 15 according to the change in the sub-beam light quantity (in this example, the emitted light quantity of the sub-beam C) by the sub-beam light quantity varying means 12. The amount of light emitted from the sub beam C is determined according to the measurement result.
[0028]
For example, the emitted light quantity of the sub beam B is fixed to E and the emitted light quantity of the sub beam C is fixed to 0.9E, respectively, and the tracking error signal generated by the tracking error signal generating means 13 is controlled to be zero.
[0029]
The sub beam light amount adjusting operation described above will be described with reference to the flowchart shown in FIG. First, in the optical pickup 2, the sub beam B and the sub beam C emit the same amount of light E (step S1). Then, the signal processing circuit 9 controls the optical pickup 2 via the servo circuit 7 so that the tracking error signal becomes 0 by the return light of the sub beam B and the return light of the sub beam C (step S2). Under this condition, the jitter measuring means 15 of the signal processing circuit 9 measures jitter (step S3).
[0030]
Next, the emitted light quantity of the sub beam B is set to a constant light quantity E, and the emitted light quantity αE of the sub beam C is changed with respect to this (step S4). For example, by setting α = 0.7, the amount of light emitted from the sub beam C is 0.7E, and the amount of light emitted from the sub beam B is 0.7E, and the amount of light emitted from the sub beam C is 0.7E. (Step S2), and the jitter at this time is measured (step S3). Next, by setting α = 0.8, the amount of emitted light of the sub beam C becomes 0.8E, the amount of emitted light of the sub beam B is E, and the amount of emitted light of the sub beam C is 0.8E. Control is made to be 0 (step S2), and the jitter at this time is measured (step S3).
[0031]
In this way, α = 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3 are sequentially changed (step S4), and the tracking error signal is 0. (Step S2), and the jitter at this time is measured (step S3). Then, the sub-beam C emission light amount αE at the time of minimum jitter is determined by the sub-beam light amount determination means 11 from the measured jitters, and the sub-beam B output light amount E and the sub-beam C output light amount αE are fixed (step S5). For example, if the amount of light emitted from the sub beam C at the time of minimum jitter is 0.9E, the amount of light emitted from the sub beam is fixed at 0.9E, and the tracking error signal is controlled to be zero.
[0032]
According to the optical disk reproducing apparatus described above, the edge is not symmetrical with respect to the center of the track T as shown in FIGS. 3 and 4 by applying the sub-beam light amount adjusting operation described above every time the optical disk changes. Even in the case of an optical disk, the main beam A from the optical pickup 2 always passes through the center of the track T, so that the best reproduction capability state (playability) can be obtained and jitter can be minimized. In addition to adjusting the sub-beam light amount every time the optical disk changes, when the jitter deteriorates from a predetermined value, by measuring the optimum value of the sub-beam and fixing this optimum value, always The best reproduction capacity state can be obtained and stable performance can be maintained.
[0033]
【The invention's effect】
As described above, according to the present invention, the light quantity of at least one of the two sub-beams emitted from the optical pickup is changed, and based on the jitter measurement result measured according to the changed light quantity of the sub-beam. Signal processing circuit that determines the light quantity of the sub-beam, so even when playing an optical disc whose tracks are not symmetrical, jitter can be minimized, so stable performance and the best playback capability state (Playability) is obtained, and the reproduction accuracy is improved.
[0034]
According to the present invention, the reproducing means for reproducing the recorded information of the optical disk based on the return light of the main beam, the jitter measuring means for measuring jitter based on the return light of the main beam, and the return lights of the two sub beams. Tracking error signal generating means for generating a tracking error signal for tracking servo based on the above, a sub-beam light quantity varying means for varying the light quantity of at least one of the two sub-beams, and a sub-beam by this sub-beam light quantity varying means Since it has a sub beam light quantity determining means for determining the light quantity of the sub beam based on the jitter measurement result measured by the jitter measuring means according to the change in the light quantity, even when reproducing an optical disc whose tracks are not symmetrical, Jitter can be minimized and thus reduced Performance and the best reproduction capability state (playability) is obtained, the reproduction accuracy is improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc playback apparatus according to an embodiment of the present invention.
FIG. 2 is a view for explaining a track cross section in which the track on the optical disc is uniform with respect to the center in the embodiment.
FIG. 3 is a view for explaining a cross section of the track on the optical disc having a convex portion at the edge and not uniform with respect to the center in the embodiment.
FIG. 4 is a view for explaining a cross section of a track that has a recess on an edge of a track on the optical disc and is not uniform with respect to the center in the embodiment.
FIG. 5 is a flowchart for explaining sub-beam light amount adjustment control in the embodiment;
FIG. 6 is a diagram for explaining a state of a light spot in which a track on an optical disc is irradiated with a main beam and a sub beam in the embodiment and the conventional optical disc reproducing apparatus.
7 is a diagram illustrating a comparator that generates a tracking error signal by inputting a signal obtained by converting the return light of two sub-beams described in FIG. 6 into an electrical signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical pick-up 9 Signal processing circuit 10 Sub beam light quantity measuring means 11 Sub beam light quantity determining means 12 Sub beam light quantity varying means 13 Tracking error signal generating means 15 Jitter measuring means

Claims (6)

In an optical disk reproducing apparatus for reproducing information recorded on an optical disk, a main beam is irradiated with the center of the track of the optical disk as a target, and two sub beams are irradiated with both edges of the track as targets, respectively, and the return light from the optical disk Is a signal that changes the light quantity of at least one of the two sub beams and determines the light quantity of the sub beam based on the jitter measurement result measured according to the changed light quantity of the sub beam. An optical disk reproducing apparatus comprising a processing circuit. In an optical disk reproducing apparatus for reproducing information recorded on an optical disk, a main beam is irradiated with the center of the track of the optical disk as a target, and two sub beams are irradiated with both edges of the track as targets, respectively. An optical pickup for receiving the return light of the two sub-beams, a reproducing means for reproducing the recording information of the optical disk based on the received return light of the main beam, and jitter based on the return light of the received main beam. Jitter measuring means for measuring, tracking error signal generating means for generating a tracking error signal for tracking servo based on the return light of the two sub beams, and the light quantity of at least one of the two sub beams is varied. Sub-beam light quantity variable means; An optical disk reproducing apparatus comprising: a sub-beam light amount determining unit that determines a light amount of the sub-beam based on a jitter measurement result measured by the jitter measuring unit according to a change in the sub-beam light amount by the sub-beam light amount varying unit. . 3. The optical disk reproducing apparatus according to claim 2, wherein when the optical disk to be reproduced changes, the light quantity of the sub beam is adjusted based on the jitter measurement result. The optical disk reproducing apparatus according to claim 2, wherein when a predetermined condition is reached, the light amount of the sub beam is adjusted based on the jitter measurement result. 5. The optical disk reproducing apparatus according to claim 4, wherein the predetermined condition is a time when the jitter is deteriorated from a predetermined value. 3. The optical disk reproducing apparatus according to claim 1, wherein the light amount of the sub beam determined based on the jitter measurement result is a light amount of the sub beam when the jitter is minimized.

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