JPH0644569A - Optical disk device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an amplifying circuit which amplifies the output signals of a photodetector in an optical disk device which generates tracking error signals using side beams and records a desired information in a DRAW type optical disk. CONSTITUTION:Output signals SE to SH of photodetectors 28 and 30, which receive reflected light of side beams, are bandwidth limited through a low pass filter circuit 54, signal levels are compensated by a light quantity detection result S3 and a side beam push-pull signal SPP is generated.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 3) Problem to be Solved by the Invention (FIG. 4) Means for Solving the Problem (FIGS. 1 and 2) Action (FIGS. 1 and 2) Example (1) Configuration of Embodiment (FIGS. 1 and 2) (2) Effect of Embodiment (3) Other Embodiment Effect of Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device,
In particular, it is suitable for application to an optical disk device that records desired information using a write-once optical disk.

[0003]

2. Description of the Related Art Heretofore, in this type of optical disk device, there is an optical disk device capable of recording desired information by using a so-called write-once optical disk.

That is, in the write-once type optical disc device, desired information can be recorded only once by irradiating an organic dye-based thin film with a light beam to form a pit. Further, by forming the pits in this way, an optical disc of this kind can be reproduced by an ordinary compact disc player, and therefore, in this optical disc device, a stamper can be applied for small-volume production. It is possible to create an optical disk that can be reproduced by a compact disk player without creating it.

Therefore, in this kind of optical disk,
By forming a pre-groove along the pit forming position and performing tracking control based on this pre-groove, the pit can be surely formed.

That is, in FIG. 3, reference numeral 1 denotes an optical disk device as a whole, and desired information is recorded on a write-once optical disk 2.

In the optical disc device 1, the spindle motor 4 is driven to rotationally drive the optical disc 2 at a predetermined rotation speed, and in this state, the optical pickup 6 is driven to record and reproduce desired information. That is, in the optical pickup 6, the laser diode 10 is driven based on the drive signal output from the laser driver 8, and the light beam L1 of this laser diode 10 is converted into parallel rays by the lens 12.

Further, in the optical pickup 6, the light beam L1 is guided to the objective lens 16 via the beam splitter 14, and is condensed on the optical disk 2 by the objective lens 16. Thus, in the optical disc device 1, the light beam L1 of the laser diode 10 is focused on the optical disc 2 so that desired information can be recorded and reproduced.

That is, in the reproduction mode, the optical disc device 1 emits the light beam L1 with a reduced amount of light (hereinafter, this amount of light is referred to as read power), while at the time of information recording, as shown in FIG. The light beam L1 is emitted by switching the light amount between the light amount required for formation (hereinafter referred to as write power) and the read power (FIG. 4A). At the time of this information recording, in the optical disc device 1, the timing generation circuit 17 controls the timing of light amount switching according to the recording information EFM, and thereby the desired information is recorded.

Further, in the optical pickup 6, the reflected light L2 of the optical disc 2 is received by the objective lens 16 and reflected by the beam splitter 14, and the reflected light L2 is incident on the cylindrical lens 22 and collected by the light receiving element 24. Glow.
Here, in the light receiving element 24, the light receiving surfaces A to D are arranged in the radial direction of the optical disk 2 via the optical system of the optical pickup 6.
Is divided into two, and each of the light receiving surfaces A to D is further divided into two in a direction orthogonal to this direction.

Accordingly, in the optical disc device 1,
While recording information, the pit forming state can be monitored based on the output signals SA to SD of the light receiving element 24, while recording information can be reproduced during reproduction. That is, in the optical disc 2, the pits are formed when the temperature of the optical disc L1 is started after the irradiation of the optical beam L1 is started. Therefore, in the reflected light L2, the light amount immediately after the light beam L1 is switched to the light power is rapidly increased. , When the pits start to form, it falls to a certain value (Fig. 4
(B)).

Further, in the reflected light L2, when the light beam L1 is subsequently switched to the lead power, the light quantity is reduced, whereby the light receiving surfaces A to D in the optical disc device 1 are reduced.
Output signals SA to SD of sum signal SA + SB + SC
By obtaining + SD, the pit formation state can be monitored, and the recorded information can be reproduced during reproduction.

On the other hand, in the light receiving element 24, by receiving the reflected light L2 through the cylindrical lens 22, the output signals SA, SC and SB are received between the light receiving surfaces A and C, B and D arranged in the diagonal direction. And SD sum signal S
A + SC, SB + SD are obtained, and this sum signal SA + SC, S
The focus error signal FE can be obtained by obtaining the difference signal of B + SD.

At the time of reproduction, in the optical disc device 1, the sum signals SA + SD and SB + SC are obtained between the light receiving surfaces A and D, B and C arranged in the pit formation direction of the optical disc 2, and the sum signals SA + SD and SB + SC are obtained. By obtaining the difference signal, it is possible to detect the tracking error as in the case of the compact disc player.

However, since no pits are formed at the time of recording, a tracking error cannot be detected by this method, and in the optical disc device 1 of this type, the optical disc 2 and the both ends of the light receiving element 24 are eventually detected. The pre-grooves of the optical disc 2 are detected by the light receiving elements 28 and 30 arranged in the radial direction, and a tracking error signal is generated thereby.

That is, in the light pickup 6, a grating 32 is inserted between the lens 12 and the beam splitter 14, and the diffracted light of the light beam L1 is formed here. Further, in the optical pickup 6, together with the direct light (hereinafter referred to as center beam) that passes through the grating 32, the ± first-order light (hereinafter referred to as side beam) of this diffracted light is focused on the optical disk 2 by the objective lens 16. To do.

Accordingly, in the optical disc device 1,
This side beam is condensed on the pre-groove, and the reflected light L2 is received by the light receiving elements 28 and 30.

At this time, in the light receiving elements 28 and 30, the light receiving surface is divided into two in the radial direction of the optical disk 2, so that in the optical disk device 1, one of the light receiving surfaces E to H of the optical disk 2 is divided. Output signals SE, SG, SF between the outer and inner light-receiving surfaces E, G, F, H
And SH sum signals SE + SG and SF + SH are obtained, and a difference signal (SE + SG) is obtained between the sum signals SE + SG and SF + SH.
By obtaining − (SF + SH), the irradiation position of the center beam with respect to the pre-groove is detected.

However, in practice, the light receiving elements 28 and 3 are
With respect to the incident light of 0, since the light amount largely changes following the light amount change of the light beam L1 at the time of information recording (FIG. 3C), in the optical disc device 1, the light receiving element 28 is generated at the timing of the lid power. The output signals of 30 and 30 are sample-held so that a tracking error signal can be detected during information recording and reproduction.

That is, in the optical disc device 1, the output signals SA to AH of the respective light receiving elements 24, 28 and 30 are output to the sample hold circuit (S / H) 34, and the sampling output from the timing generation circuit 34 is performed here. The sample is held by the pulse SP (the sampling timing is indicated by an arrow in FIG. 4). Further, in the optical disk device 1, the sampled and held output signals SA to SH are output to the matrix circuit 36, and the addition / subtraction processing is executed between the output signals SA to SD to generate the focus error signal FE. , This focus error signal E
F is output to the phase compensation circuit 38.

Accordingly, the phase compensation circuit 38 drives the focus actuator 40 so that the focus error signal becomes 0 level, and controls the focus.

Further, in the matrix circuit 36, the sum signals SA + SD, SB + are received between the light-receiving surfaces A and D, B and C of the light-receiving element 24 which are arranged in the pit forming direction of the optical disk 2.
SC is obtained, and the difference signal between the sum signals SA + SD and SB + SC (hereinafter referred to as center beam push-pull signal) CPP
To generate.

Further, the matrix circuit 36 receives the light-receiving elements 28 and 30 based on the sample and hold results obtained during the read power period, and receives the light-receiving surfaces E, G and F on the outer and inner circumference sides of the optical disk 2, respectively. Between H and H, the sum signal SE + of the output signals SE and SG, SF and SH +
SG, SF + SH are obtained, and the sum signals SE + SG, SF + are obtained.
A difference signal (hereinafter referred to as side beam push-pull signal) SPP ((SE + SG)-(SF + SH)) is obtained between SH, and the center beam push-pull signal CPP and the side beam push-pull signal SPP are subtracted by the subtraction circuit 42. And a tracking error signal TE is generated.

Therefore, in the optical disc device 1, the tracking actuator 4 is used by the phase compensation circuit 44 so that the tracking error signal TE becomes 0 level.
6 is driven so that tracking control can be reliably performed even at the time of recording information.

[0025]

By the way, in this side beam, since the light amount is as small as 1/9 as compared with the center beam, in the optical disc device 1, the output signals SE to SH of the light receiving elements 28 and 30 are received. Must be amplified by an amplifier circuit having a large amplification factor. At this time, when the band of the amplifier circuit is narrow, the waveforms of the output signals SE to SH deteriorate as shown by the broken line in FIG.
In the optical disk device 1, the correct signal level cannot be sampled and held, so that the tracking error signal TE
Cannot be detected correctly.

Further, when the output signals SE to SH are amplified with such a large amplification factor, the DC level may fluctuate, and the tracking error signal cannot be stably detected in the spectral disk device 1.

Therefore, in the conventional optical disk device 1 using the side beam, there is a problem that the structure of the amplifier circuit for amplifying the output signals SE to SH becomes complicated, and this amplifier circuit is arranged in the vicinity of the optical pickup. By doing so, there is a problem that the access time becomes long.

The present invention has been made in consideration of the above points, and the structure of the amplifier circuit for amplifying the output signal of the light receiving element can be simplified even when tracking control is performed using the side beam. It is intended to propose a disk device.

[0029]

In order to solve the above problems, in the present invention, the optical disc 2 having pregrooves is irradiated with a center beam and a side beam so that desired information is provided to the optical disc 2. In the optical disc device 50 for recording, the center beam and the side beam are applied to the optical disc 2, and the reflected light L2 of the optical disc 2 is emitted.
Of the center beam received by the optical system 10-22 by dividing the light receiving surface in the radial direction of the optical disk 2 into the first and second light receiving surfaces A, D and B, C. A center beam light receiving element 24 for receiving the reflected light L2, and adjacent to the center beam light receiving element 24 are arranged on both sides of the center beam light receiving element 24 in the radial direction of the optical disk 2.
The light receiving surface is divided in the radial direction of the optical disk 2, and the optical system 10
First and second side beam light receiving elements 28 and 30 for receiving the reflected light L2 of the side beams received at
The first and second light receiving surfaces A of the center beam light receiving element 24,
Output signals SA + SD and SB + for D, B, and C
A first for generating a center beam push-pull signal CPP by detecting the SC difference signal (SA + SD)-(SB + SC)
The push-pull signal generating means 52 and the light quantity detecting means 56, 5 for detecting the light quantity of the reflected light L2 of the side beams incident on the first and second side beam light receiving elements 28 and 30.
8, 62 and the first and second side beam light receiving elements 28
, 30 between the first and second sum signals S on the inner and outer light receiving surfaces E, G, F, and H of the optical disk 2, respectively.
E + SG and SF + SH are obtained and the first and second sum signals S
E + SG and SF + SH difference signal (SE + SG)-(S
F + SH) to detect the side beam push-pull signal S
Second push-pull signal generating means 56 for generating PP,
58 and 60, and a signal level correction means 6 for correcting and outputting the signal levels of the side beam push-pull signal SPP based on the detection result S3 of the light amount detection means 56, 58 and 62.
4 and a subtracting means 42 for subtracting the output signal STE of the signal level correcting means 64 from the center beam push-pull signal CPP to generate a tracking error signal TE.

Further, in the present invention, the second push-pull signal generating means 56, 58, 60 output signals output from the first and second side beam receiving elements 28, 30 via the predetermined low-pass filter circuit 54. SE to SH
Of the first and second sum signals SE + SG after suppressing the band of
And SF + SH are detected, and the light amount detecting means 56, 58, 6 are detected.
2 detects the light quantity of the reflected light L2 of the side beam by adding the output signals SE to SH of the first and second side beam light receiving elements 28 and 30 output via the low-pass filter circuit 54, Signal level correction means 64
Corrects the side beam push-pull signal SPP by dividing the side beam push-pull signal SPP by the detection result S3 of the light amount detecting means 56, 58, 62.

Further, in the present invention, the subtracting means 66 is
At the time of seeking, instead of the output signal STE of the signal level correction means 64, second push-pull signal generation means 56, 58, 6
Side beam push-pull signal SPP output from 0
Is subtracted from the center beam push-pull signal CPP to generate a traverse signal TB.

[0032]

After the signal level of the side beam push-pull signal SPP is corrected based on the detection result S3 of the light amount detecting means 56, 58, 62, the center beam push-pull signal C
If the tracking error signal TE is generated by subtracting from PP, the correct tracking error signal TE can be generated even if the light amount of the side beam changes.

Further, the first and second side beam receiving elements 28 and 3 are connected via a predetermined low-pass filter circuit 54.
After suppressing the band of the output signals SE to SH of 0, the sum signal S
It is possible to narrow the band of the amplifier circuit by detecting the light amounts of E + SG and SF + SH and the reflected light L2.

Further, at the time of seek, the signal level correction means 64
Side beam push-pull signal SP instead of the output signal of
The correct traverse signal TB can be generated by subtracting P from the center beam push-pull signal CPP to detect the traverse signal TB.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Configuration of the Embodiment In FIG. 1 in which parts corresponding to those in FIG. 3 are designated by the same reference numerals, 50 denotes an optical disk device as a whole, and sample-holds output signals SA to AD of the light receiving element 24. Circuit (S
/ H) 52.

The sample and hold circuit 52 samples and holds the output signals SA to AD at the same timing as the sample and hold circuit 34 (FIG. 4), and then performs addition and subtraction processing, whereby the focus error signal FE and the center beam. A push-pull signal CPP is generated and output.

On the other hand, a low-pass filter circuit (LP
F) 54 has a cut-off frequency selected to be approximately the lowest drive frequency of the laser diode 10, whereby the high frequency components of the output signals SE to SH of the light receiving elements 28 and 30 whose signal levels change due to repetition of read power and write power. After suppressing, it is amplified with a sufficient amplification factor and output.

The adder circuits 56 and 58 of the light-receiving surfaces E to H of the light-receiving elements 28 and 30, respectively, are the optical disks 2 respectively.
The output signals of the low-pass filter circuit 54 are added to the light-receiving surfaces E and G, F, and H on the inner and outer peripheries of the output signal and output. Further, the subtracting circuit 60 detects a difference signal between the output signals S1 and S2 of the adding circuits 56 and 58 to generate a side beam push-pull signal SPP in which high frequency components are suppressed.

The adder circuit 62 receives the adder circuits 56 and 5 from each other.
With respect to the output signals S1 and S2 of No. 8, the incident light amount of the light receiving elements 28 and 30 is detected by generating the addition signal S3. Therefore, in the optical disc device 50,
The side beam push-pull signal SPP obtained by dividing the side beam push-pull signal SPP by the output signal S3 of the adder circuit 62 in the division circuit 64 to suppress the high frequency component.
The signal level of P is corrected by the amount of incident light on the light receiving elements 28 and 30.

That is, in the output signals of the light receiving elements 28 and 30, when the high frequency component is suppressed by changing the signal level due to the repetition of the read power and the write power, the entire signal level is incident on the light receiving elements 28 and 30. It changes according to the amount of light. Thus, as in this embodiment, if the signal level is corrected by the detection result of the incident light amount, the high frequency component is suppressed and the side beam push-pull signal SPP is suppressed.
Even when the signal is generated, it is possible to obtain the side beam push-pull signal SPP in which the signal level correctly changes according to the tracking error.

As a result, in the optical disk device 50, the output signal STE of the division circuit 64 is output to the subtraction circuit 42 via the switch circuit 66, where it is subtracted from the center beam push-pull signal CPP to cause a tracking error. Generate signal TE.

At this time, in the optical disk device 50,
By suppressing the high frequency component by the low pass filter circuit 54 and amplifying the output signals SE to SD, it is possible to easily amplify the output signals SE to SD with a high gain by using a narrow band amplifier circuit, thereby simplifying the configuration of this amplifier circuit. Can be converted. Further, in such a narrow band amplifier circuit, fluctuations in DC level can be easily suppressed, so that a tracking error signal can be stably detected, and the overall shape can be made smaller, so that the access time can be shortened. Can be shortened.

By the way, the output signal of the low-pass filter circuit 54 is almost DC level, and it is difficult to visually confirm the actual tracking error signal generation operation by the signal waveform diagram. Therefore, as shown in FIG. 2, the light quantity of the laser diode is switched to traverse the optical pickup 6.
As a result, it was confirmed by the signal waveform that the output signal STE of the division circuit 64 is maintained at a constant amplitude even when the light amount of the light beam L1 changes.

In this case, the optical disc 2 before the formation of the pits is used, and the output signals S1 and S2 (FIGS. 2A and 2B) of the adder circuits 56 and 58 due to the traverse are compared with the repetition frequency of the read power and the write power. Even when pulsating at a low frequency, the light amount detection result S3 (Fig. 2 (C))
, The signal level changes as the light amount is switched, and the side beam push-pull signal SPP (see FIG.
It was possible to correct (D)) with this light amount detection result and hold the amplitude at a constant value (FIG. 2 (E)).

Further, in this embodiment, in the optical disk device 50, by switching the contact of the switch circuit 66 at the time of seek, the side beam push-pull signal SPP is sent to the subtraction circuit 42 instead of the output signal of the division circuit 64. Then, the traverse signal TB is generated.

That is, in this type of optical disc device, the optical pickup 6 may be moved so as to cross the recording track. In this case, since the change in the reflected light L2 is different from that during normal recording / reproduction, the adder circuit 62 is used. The output signal S3 of 1 may pulsate following this movement. In this case, in the output signal STE of the division circuit 64,
There is a possibility that the signal level will not change in a cycle that traverses the recording track correctly, and in this embodiment, the contact point of the switch circuit 66 is switched so that the correct traverse signal TB can be detected.

Accordingly, in the optical disc device 1,
At the time of seeking, a correct traverse signal TB whose signal level changes every time it crosses the groove can be detected, so that the target track can be surely sought.

(2) Effects of the Embodiments According to the above configuration, after amplifying the output signal of the light receiving element via the low-pass filter circuit, the light amount of the side beam is detected, and the side beam push-pull is detected based on the light amount detection result. By correcting the signal level of the signal SPP, the band of the amplifier circuit can be narrowed to reliably generate the tracking error signal, and thus the configuration of the amplifier circuit can be simplified.

(3) Other Embodiments In the above-described embodiment, the selection circuit 66 at the time of seeking.
However, the present invention is not limited to this, and the contacts may be switched between recording and reproducing.

Furthermore, in the above-mentioned embodiments, the case of recording / reproducing an optical disk has been described, but the present invention is not limited to this, but can be widely applied to an optical disk device dedicated to recording.

[0052]

As described above, according to the present invention, regarding the output signal of the light receiving element that receives the reflected light of the side beam,
By correcting the signal level based on the light intensity detection result and generating a side beam push-pull signal, the output signal of the light receiving element can be band-limited and processed, thereby narrowing the band of the amplifier circuit that amplifies this output signal. The gain can be increased, the structure of the amplifier circuit can be simplified accordingly, and the tracking error signal can be reliably generated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical disk device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation.

FIG. 3 is a block diagram showing a conventional optical disk device.

FIG. 4 is a signal waveform diagram for explaining the operation.

[Explanation of symbols]

1, 50 ... Optical disk device, 2 ... Optical disk, 10
... laser diode, 24, 28, 30 ... light receiving element, 34, 52 ... sample hold circuit, 36 ... matrix circuit, 42, 60 ... subtraction circuit, 54 ... low-pass filter circuit, 56, 58, 62 ...... Adding circuit,
64: division circuit, 66: switch circuit.

Claims (3)

[Claims] 1. An optical disc device for irradiating an optical disc having a pre-groove with a center beam and a side beam to record desired information on the optical disc, wherein the center beam and the side beam are An optical system for irradiating the optical disk and receiving the reflected light of the optical disk, and a light receiving surface divided into a first and a second light receiving surface in the radial direction of the optical disk, and the center received by the optical system. A center beam light receiving element for receiving the reflected light of the beam, and adjacent to the center beam light receiving element, are arranged on both sides of the center beam light receiving element in the radial direction of the optical disk, and receive light in the radial direction of the optical disk. First and second side beam light receiving elements that divide the surface and receive the reflected light of the side beam received by the optical system, and the center beam First push-pull signal generating means for generating a center beam push-pull signal by detecting a difference signal between output signals on the first and second light-receiving surfaces of the light-receiving element, and the first and second side-beam receiving portions. Between the light amount detecting means for detecting the light amount of the reflected light of the side beam incident on the element and the first and second side beam light receiving elements, the light receiving surfaces on the inner peripheral side and the outer peripheral side of the optical disk respectively have Second push-pull signal generation means for generating a side beam push-pull signal by detecting a difference signal between the first and second sum signals, and a side beam push-pull A signal level correcting means for correcting and outputting the signal level of the signal based on the detection result of the light quantity detecting means; and an output signal of the signal level correcting means for the center beam push-pull signal. An optical disk device comprising: subtraction means for subtracting from the above to generate a tracking error signal. 2. The second push-pull signal generating means comprises:
The above first and second through a predetermined low-pass filter circuit.
After suppressing the band of the output signal output from the side beam light receiving element, the light amount detecting means detects the first and second sum signals, and the light amount detecting means outputs the first signal output via the low-pass filter circuit. And the output signals of the second side beam light receiving element are added to detect the light quantity of the reflected light of the side beam, and the signal level correcting means detects the side beam push-pull signal by the light quantity detecting means. The optical disk device according to claim 1, wherein the side beam push-pull signal is corrected by division by a result. 3. The subtracting means replaces the output signal of the signal level correcting means with the side beam push-pull signal output from the second push-pull signal generating means when seeking, and the center beam push-pull signal. The optical disc device according to claim 1, wherein the optical disc device is configured to be subtracted from a signal to generate a traverse signal.