JPH09185833A - Tracking error generating device, disk type discriminating device, and optical disk reproducing device - Google Patents

Tracking error generating device, disk type discriminating device, and optical disk reproducing device

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Publication number
JPH09185833A
JPH09185833A JP35391295A JP35391295A JPH09185833A JP H09185833 A JPH09185833 A JP H09185833A JP 35391295 A JP35391295 A JP 35391295A JP 35391295 A JP35391295 A JP 35391295A JP H09185833 A JPH09185833 A JP H09185833A
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Japan
Prior art keywords
means
disc
signal
recording medium
optical
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JP35391295A
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Japanese (ja)
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JP3284437B2 (en
Inventor
Yasuhiro Ueki
泰弘 植木
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Victor Co Of Japan Ltd
日本ビクター株式会社
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Abstract

PROBLEM TO BE SOLVED: To automatically discriminate type of disk for changing over a signal by making a tracking error signal generated by three-beam method and a track ing error signal. generated by a phase-difference method to be selective by changing over properly, in order to be suitable for a reproducing device served as DVD(Digital Versatile Disk) as well as CD(Compact Disc). SOLUTION: By providing a selection means 30 for selecting a tracking error signal by means of properly changing over two kinds of tracking error signals from one to the other, measuring a first and a second detected signals obtained respectively during focus searching, and discriminating a type of a disk-shaped optical recording medium by using the first and second measured detected signals, the selection means 30 is controlled according to the type of disk discriminated. Further, by measuring an amplitude and a frequency of the detected signals obtained at one focus during focus searching and discriminating a type of disk by using the measurement result, a timing for turning a servo control ON is controlled depending on a status adaptable to a lens disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus or an optical disk reproducing apparatus for recording / reproducing a signal to / from a disk-shaped recording medium, and more particularly to a tracking error signal generating apparatus and disk type used in such an apparatus. The present invention relates to a discriminating device, and further to an optical disc reproducing device having a two-lens type optical head.

[0002]

2. Description of the Related Art Generally, in this type of information recording / reproducing apparatus, tracking control and focus control of an optical head are performed so that data can be accurately written and read during recording and reproduction. Such control is performed by controlling the optical head by a so-called servo control circuit. A three-beam method and a phase difference method (phase difference detection method: DPD method) are generally used as a method of generating a tracking error signal used for tracking control of an optical head. These methods include, for example, "Compact Disc Reader" pp134-138 (Showa 57) issued by Ohm Co.
-230637, etc. Although various types of disc-shaped optical recording media have been developed,
As a disc having a diameter of 12 cm, in addition to a so-called CD (compact disc), a CD-ROM, a video CD, a DVD
Multiple types such as (Digital Versatile Disc) have been put to practical use. These discs have various data formats, compression methods, data recording densities, etc. of recorded information, but all have a diameter of 12 cm and data can be read by an optical head (optical pickup). A playback device that can be used for a plurality of types of discs has been developed. Further, as an optical head for such a combined reproducing apparatus, a two-lens type optical pickup capable of switching and using two lenses having different NAs has been developed.

[0003]

The thickness is now 1.2 mm.
When a dual-use reproducing apparatus for a CD and a DVD having a thickness of 0.6 mm is examined, the three-beam method is the most suitable method for generating a tracking error signal for a CD. Especially, in the case of a dual-layer DVD, a signal from a layer other than the target leaks, which is a problem. Further, in the 3-beam method, crosstalk from adjacent tracks poses a problem in land-groove recording in which high density recording is performed on a phase change medium. Further, although the phase difference method is suitable for DVD, when applied to CD, the waveform of the tracking error signal does not become a sine wave when the light spot is small, which may cause a problem at track crossing. Further, in the phase difference method, the quality of the tracking error signal may vary depending on the pit depth. Further, when using a two-lens type optical pickup, unless the focus servo control is turned on and the signal is read from the disc, the disc type cannot be discriminated and it takes a considerable time to start the reproduction. .

Therefore, according to the present invention, the tracking error signal generated by the three-beam method and the tracking error signal generated by the phase difference method can be appropriately switched and selected so as to be suitable for a combined reproducing apparatus for CD and DVD. First, to provide a tracking error signal generator capable of
The purpose of. Further, if the disc type can be automatically determined for the switching of the tracking error signal, the switching can be automated. Therefore, a second object of the present invention is to provide a disc type discriminating apparatus capable of discriminating a disc type automatically and a tracking error signal generating apparatus capable of selecting a tracking error signal based on the discriminating result. And A third object of the present invention is to provide a disc type discriminating apparatus capable of promptly discriminating the disc type and an optical disc reproducing apparatus which takes a short time to start reproducing when a two-lens type optical pickup is used.

[0005]

In order to achieve the first object, in the present invention, the tracking error signal generated by the three-beam method and the tracking error signal generated by the phase difference method are appropriately switched and selected. The selection means for this is provided. Further, in order to achieve the above-mentioned second object, in the present invention, the first and second detection signals respectively obtained at the two focal points of the two-focal type optical head during the movement by the focus search means are measured and measured. The type of the disc-shaped optical recording medium is discriminated using the first and second detection signals, and the selection means is controlled according to the disc type discriminated. When a two-lens type optical pickup is used, in order to achieve the third object, the amplitude and frequency of the detection signal obtained at one focus during the movement by the focus search means are measured, and the measurement result is used. Disc type, the servo control is turned on when the currently selected objective lens is compatible with the loaded disc, and when it is not compatible, another objective lens is selected. After controlling the actuator of the optical pickup to switch to the lens, turn on the servo control,
Further, the circuit parameter to be set according to the type of disk is set according to the determined type.

That is, according to the present invention, a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, that is, two optical sensor portions used in the three-beam method, An optical head having a four-division optical sensor portion used for the phase difference method, and 2 used for the three-beam method.
First computing means responsive to output signals from one photosensor portion, a sum signal of output signals of two sensor portions on a diagonal line of the four-division photosensor portion used for the phase difference method, and two signals on another diagonal line. Second computing means for obtaining a difference signal between the output signal of the sensor portion and the sum signal, third computing means for obtaining a sum signal of the output signals from the four-division optical sensor portion, the second computing means and the third A fourth arithmetic means responsive to the output signal of the arithmetic means, a low-pass filter responsive to the output signal of the fourth arithmetic means, an output signal of the first arithmetic means and an output signal of the low-pass filter are selected. A tracking error signal generation device having a selection means is provided.

According to the present invention, a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, which are two optical sensor portions used in the three-beam method, An optical head having a 4-division optical sensor portion used for the phase difference method, a first calculation means responsive to output signals from the two photosensor portions used for the 3-beam method, and a 4-division light used for the phase difference method. Second computing means for obtaining a difference signal between a sum signal of output signals of two sensor portions on a diagonal line of the sensor portion and a sum signal of output signals of two sensor portions on another diagonal line, and the four-division optical sensor portion Calculating means for obtaining the sum signal of the output signals from the second calculating means, the fourth calculating means responsive to the output signals of the second calculating means and the third calculating means, and the low-pass responding to the output signals of the fourth calculating means. Filter and the first Selection means for selecting either the output signal of the calculation means or the output signal of the low-pass filter, means for determining the type of the disk-shaped optical recording medium, and determination as to whether or not the optical head is on-track. At least one of the means, and when the recording density of the disc-shaped optical recording medium is lower than a predetermined value, or when the disc-shaped optical recording medium is a single-layer disc, or a read-only disc, further, When the optical head is off-track, the output signal of the first computing means is selected, and when the recording density of the disc-shaped optical recording medium is equal to or higher than the predetermined value, or when the disc-shaped optical recording medium is a multi-layer disc. In some cases, when the disc is a recordable disc, and when the optical head is on-track, the output signal of the low pass filter is selected. And control means for controlling said selection means to the tracking error signal generation device having is provided.

According to the present invention, a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, which are two optical sensor portions used in the three-beam method, A two-focus optical head having a four-division optical sensor portion used for the phase difference method, a first calculation means responsive to output signals from the two optical sensor portions used for the three beam method, and used for the phase difference method. Second computing means for obtaining a difference signal between a sum signal of output signals of two sensor portions on a diagonal line of the four-division optical sensor portion and a sum signal of output signals of two sensor portions on another diagonal line; Third computing means for obtaining a sum signal of output signals from the optical sensor portion, and the second computing means
A fourth means responsive to the output signals of the calculating means and the third calculating means
Computing means, a low-pass filter responsive to the output signal of the fourth computing means, selecting means for selecting one of the output signal of the first computing means and the output signal of the low-pass filter, the optical head or its optical Focus search means for moving the system in the focus direction; measuring means for measuring first and second detection signals respectively obtained by the third computing means at two focal points during movement by the focus search means; A discriminating means for discriminating the type of the disc-shaped optical recording medium using the first and second detection signals measured by the means, and a disc-shaped optical recording medium discriminated by the discriminating means. Accordingly, there is provided a tracking error signal generation device having a control means for controlling the selection means.

Further, according to the present invention, a laser for generating a laser beam for reproducing information from the disk-shaped optical recording medium, two objective lenses having different NAs, and the two objective lenses are selectively used. An actuator arranged in the optical path of the laser beam, an optical head having a plurality of optical sensor portions for detecting reflected light of the laser beam, an operation means responsive to output signals from the plurality of optical sensor portions, and Focus search means for moving the optical head or its optical system in the focus direction, and measuring means for measuring the amplitude and frequency of the detection signal obtained by the computing means at one focus during movement by the focus search means, A discriminating means for discriminating the type of the disc-shaped optical recording medium using the measurement result by the measuring means,
There is provided a disc type discriminating device having the same.

Further, according to the present invention, a driving means for rotating the disc-shaped optical recording medium, a laser for generating a laser beam for reproducing information from the disc-shaped optical recording medium, and two different NAs. An optical head having an objective lens, an actuator for selectively arranging the two objective lenses in the optical path of the laser beam, and a plurality of optical sensor portions for detecting reflected light of the laser beam,
Computation means responsive to output signals from the plurality of optical sensor portions, servo control means for servo-controlling the optical head according to output signals from the computation means, and output signals from the plurality of optical sensor portions A signal reproducing means for generating a reproduced signal, a focus search means for moving the optical head or its optical system in the focus direction, and a detection signal obtained by the arithmetic means at one focus during movement by the focus search means. The measuring means for measuring the amplitude and the frequency, the judging means for judging the type of the disc-shaped optical recording medium by using the measurement result by the measuring means, and the objective lens currently selected by the judging means When it corresponds to the disc-shaped optical recording medium, the servo control of the servo control means is turned on,
On the other hand, if not compatible, after controlling the actuator to switch to another objective lens, the servo control of the servo control means is turned on, and further, it should be set according to the type of the disc-shaped optical recording medium. The control means for setting the circuit parameter according to the determined type,
An optical disk reproducing apparatus having the same is provided.

Further, according to the present invention, a driving means for rotating the disc-shaped optical recording medium, a laser for generating a laser beam for reproducing information from the disc-shaped optical recording medium, and two different NAs. An optical head having an objective lens, an actuator for selectively arranging the two objective lenses in the optical path of the laser beam, and a plurality of optical sensor portions for detecting reflected light of the laser beam,
Computation means responsive to output signals from the plurality of optical sensor portions, servo control means for servo-controlling the optical head according to output signals from the computation means, and output signals from the plurality of optical sensor portions A signal reproducing means for generating a reproduced signal, a focus search means for moving the optical head or its optical system in the focus direction, and a single focus obtained by the arithmetic means while the focus search means is moving in the predetermined direction. Measuring means for measuring the amplitude and frequency of the detected signal, discriminating means for discriminating the type of the disk-shaped optical recording medium using the measurement result by the measuring means, and currently discriminated by the discriminating means. If the objective lens is compatible with the disc-shaped optical recording medium, the servo control of the servo control means is turned on, and If not compatible, after controlling the actuator to switch to another objective lens, the focus search means moves in the direction opposite to the predetermined direction to turn on the servo control of the servo control means. Further, there is provided an optical disk reproducing device having a control means for setting a circuit parameter to be set according to the type of the disc-shaped optical recording medium according to the determined type.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described with reference to the accompanying drawings with reference to the accompanying drawings. FIG. 2 is a block diagram showing an embodiment of an optical disc reproducing apparatus according to the present invention. This optical disc reproducing apparatus reproduces information from a reproduction-only type CD and DVD.
D includes a reproduction-only two-layer type, a write-once type, and a recording / reproducing type. FIG. 1 is a circuit diagram showing an optical pickup (PU) in FIG. 2 and an arithmetic unit (a part of the preamplifier in FIG. 2) responsive to an output signal thereof. 3 to 5 are processing procedures for switching between two types of tracking error signals according to the type of disc and the operation mode in the operation of the microcomputer used in the system controller in FIG. 3 are three flowcharts showing. For generation of the tracking error signal, the circuit of FIG. 15 described later can be used instead of the circuit of FIG.

In FIG. 2, the motor driver / tracking focus control circuit 4 controls the disk 1 to be rotated at a CLV (constant linear velocity) by the spindle (SP) motor 3. The signal read from the disc 1 by the optical pickup (optical head) 2 is supplied to the preamplifier 5, and the output signal thereof is given to the digital servo control circuit 6. The system controller 7 sends and receives signals to and from the preamplifier section 5 and the digital servo control circuit 6 to control the entire optical disk reproducing apparatus. The output signal of the digital servo control circuit (DSV) 6 is supplied to the motor driver / tracking / focus control circuit 4,
Rotation control of the spindle motor 3, tracking servo control and focus servo control of the optical pickup are performed.
The DSV 6 includes a variable speed controller / memory controller / EFM demodulation circuit / error correction circuit in addition to the servo control circuit, and also has a function of sending a reproduction signal by using a memory (not shown). The optical pickup 2 can be moved in the radial direction of the disk 1 by a traverse motor (not shown), and the objective lens can be moved in the focus direction, that is, the direction along the optical path by a focus servo control mechanism (not shown).

The optical pickup 2 also has a laser diode for irradiating the disc 1 with a laser beam, and outputs a signal obtained by reproducing the optical information recorded on the disc 1 based on the reflected light thereof. As shown, signals A to D for detecting the focus error signal FE by the astigmatism method and also for detecting the tracking error signal by the phase difference method, and two types of tracking error signal detection signals E and F of the three-beam method. Is output. These signals are supplied to the preamplifier 5 to perform necessary calculations.

FIG. 1 shows a four-division photosensor portion A, B, C, D.
2 schematically shows an optical pickup 1 having optical sensor portions E and F used in the three-beam method, and also shows an arithmetic unit responsive to output signals from those optical sensor portions.
Reference numerals A to F indicate both of these photosensor parts and their output signals. The adder 10 adds the output signals of the photosensor portions A and C on the diagonal to each other and outputs the result, and the adder 12 adds the output signals of the photosensor portions B and D on the other diagonal to each other. Is output. Adder 1
Reference numerals 4 and 22 both add the output signals of the adders 10 and 12, and subtractors 16 and 20 both subtract the output signal of the adder 12 from the output signal of the adder 10. The subtractor 18 subtracts the output signal of the optical sensor portion F from the output signal of the optical sensor portion E. The output signal of the adder 14 is passed through the delay circuit 24 to the multiplier (×)
26, and the output signal of the subtractor 16 is directly applied to the other input terminal of the multiplier 26. The output signal of the multiplier 26 is given to one input terminal (1 side) of the switch 30 via the LPF 28, and the subtractor 1
The output signal of 8 is the other input terminal of switch 30 (0 side)
Given to. The selected tracking error signal TE is output from the output terminal of the switch 30.

A control signal CON supplied to the switch 30.
T controls the switch 30 to select one of the two input signals, and is generated by the microcomputer of the system controller 7 as described later. Note that the switch 30 can be manually controlled as needed. Subtractor 20
The output signal of is supplied to a known focus servo control system so as to be used as the focus error signal FE.
The output signal of the adder 22 is output as a sum signal (sum-all (SA) signal) of the 4-division photosensor portion. The sum signal SA is a main signal for reading the recorded information on the disc and also a measurement target signal for disc type discrimination described later. The focus error signal FE is used for well-known focus servo control. The delay time of the delay circuit 24 is set to a time corresponding to 1/4 of the cycle at the DVD reproduction frequency.

The microcomputer in the system controller 7 is
The control signal CONT is generated as follows according to the type of the disc 1. As one of the methods for detecting the type of the disc 1, a detection hole provided in the cartridge of the disc 1 can be detected by a detector (not shown). The relationship between the type of disc to be detected and the corresponding tracking error signal generation method can be one of the two cases shown in the following table.

[0018]

Table 1 Three-beam method Phase difference method (1) CD with low recording density DVD disk with high recording density (2) Single-layer DVD Multi-layer DVD

FIG. 3 is a processing procedure for discriminating a disc type and switching between two types of tracking error signals according to the discrimination in the operation of the microcomputer used in the system controller 7 in FIG. It is a flowchart showing. This flowchart shows the processing for selectively using the three-beam method and the phase difference method for the CD having a low recording density and the disk having a high recording density of (1) in Table 1 above. The case can be processed in the same manner. In FIG. 3, it is assumed that this flow starts when the power of the reproducing apparatus is turned on, the disc is exchanged, or the data reproduction of other layers is required in the multi-layer type disc, and first, it is connected to the microcomputer. Initialization such as clearing predetermined contents of a memory (not shown) or a buffer (not shown) is performed in step S1, and then necessary data is read in step S2.

Here, it is assumed that the disc is loaded in the reproducing apparatus in a state where the disc is housed in a predetermined disc cartridge, and the detection hole indicating the type of the disc is provided in the disc cartridge. It is assumed that the CD is read, and it is determined from the data in step S3 whether the CD has a low recording density. If YES, the switch 30 of FIG. 1 is connected to the 0 side to output the output signal of the subtractor 18 in order to select the tracking error signal of the three-beam method in step S4. On the other hand, if step S3 is NO, the switch 30 is connected to the 1 side to select the tracking error signal of the phase difference method in step S5, and the LPF2 is selected.
The output signal of 8 is output.

FIG. 4 is a flow chart showing a processing procedure for discriminating the operation mode of the reproducing apparatus in the operation of the microcomputer and switching the two kinds of tracking error signals according to the result. Although the steps up to step S1 are the same as those in FIG. 3, in step S2 in FIG. 4, the operation mode input to the operation unit for receiving an instruction from the user not shown in FIG. 2 is read. Next, in step S7, it is determined whether or not the mode is the reproduction mode. If YES, the phase difference method is selected in step S5, and the reproduction process is performed in step S8.

On the other hand, if NO in step S7, it is determined in step S9 whether or not the search mode is set. If YES, the three-beam method is selected in step S4, and step S1 is selected.
Search processing is performed with 0. The "search" here is not the focus search described above, but a series of well-known operations including an operation of moving the optical pickup in the radial direction of the disc in order to search the disc for the data or program that the user wants to read. Refers to operation. Next, in step S11, it is determined whether or not the search is completed. If the search is not completed, the process returns to step S10, and if it is completed, the process proceeds to step S5.

FIG. 5 shows the operation of the microcomputer to determine whether or not the optical spot of the optical pickup is located at the center of the track in the reproducing mode of the reproducing apparatus, and switch two kinds of tracking error signals according to the result. 6 is a flowchart showing a processing procedure for the above. Step S1
The above is the same as that of FIG. 3, but in step S2 of FIG. 5, a signal indicating whether or not the light spot from the detector, which is not shown in FIG. 2, is located at the center of the track is read.
Next, in step S12, it is determined whether or not the track is on-track (the light spot is located at the center of the track), and YE
If it is S, the phase difference method is selected in step S5, and the reproducing process is performed in step S8.

On the other hand, if NO in step S12, the three-beam method is selected in step S4, and on-track processing (control for positioning the light spot at the center of the track) is performed in step S13. Next, in step S14, it is determined whether or not the on-track processing is completed. If it is not completed, the procedure returns to step S13, and if it is completed, the step S is completed.
Go to 5.

Next, the optical pickup 2 is of a bifocal type, that is, the objective lens is provided with two converging points as shown in JP-A-7-65407 and JP-A-7-98431, and the thickness is set. A method for discriminating the type of the disc by using a disc that can be used for different discs will be described. The optical pickup 2 has NA = 0.45 mm
And a spot of NA = 0.6 mm, two types of discs, that is, a CD with a plate thickness t1 = 1.2 mm and a t2 = 0.
Information is read from a 6 mm DVD. The distance between the two focal points is 0.3 mm. If images are simultaneously formed on the disc surface and the signal surface, the disc surface influences the modulation and offset at low frequencies, so the distance between the two focal points cannot be set in the same manner as the disc thickness.

FIG. 6 is a diagram showing how the laser beam is focused on the disk 1 in such a bifocal optical pickup. 1-a is a disk with t1 = 1.2 mm, 1-b is t1 =
A 0.6 mm disc, 1-c shows a state of focusing on a double-layer disc (interlayer distance t3 = 40 μm) with one layer being 0.6 mm, the beam on the front upper side is for 1.2 mm, The side beam is for 0.6 mm. In FIG. 6, α, β, γ, δ
Shows respective states in which the objective lens of the optical pickup 2 has moved in the focus direction. FIG. 7 shows various signal waveforms obtained from the output signal when the focus search is performed by the optical pickup 2 corresponding to FIG. That is, the vertical axis of FIG. 7 is voltage, the horizontal axis is time, and p
Indicates a peak. Since the bifocal type optical pickup is composed of a hologram lens, it is disclosed in JP-A-7-9843.
Signals other than the two spots with two focal points are detected as in Japanese Patent No. 1, but signals other than the two focal point detection signals are omitted here.

2-a to 2-d in FIG. 7 are on the disk 1-a in FIG. 6, 2-e to 2-h are on the disk 1-b in FIG. 6, and 2-i.
~ 2-l corresponds to the disk 1-c in Fig. 6, respectively. In addition, the sum signal SA of FIG. 1 corresponds to 2-a, 2-e, 2-i of FIG.
And the focus error signal FE is 2-b, 2-f,
2-j, and the signal obtained as a result of comparing the sum signal SA with the threshold shown by the dotted line is 2-c, 2-g, 2 in FIG.
-k, and the signal obtained as a result of comparing the focus error signal FE with the threshold shown by the dotted line is shown in FIG.
2-d, 2-h, 2-l.

The focus search is carried out by increasing or decreasing the voltage applied to the focus coil of the optical pickup 2 to move the objective lens, which is a part of the optical system of the optical pickup 2, along the optical path. In the waveform 2-a of FIG. 7, the peak on the left side in the figure is obtained in the state A of the disk 1-a in FIG. 6, and the peak on the right side is also obtained in the state B. Thus, the peaks in FIG. 7 correspond to α and β in FIG. 6, and the waveform 2
The four peaks at -i to 2-l correspond to α, β, γ, and δ of the disc 1-c in FIG. FIG. 8 is a waveform diagram showing a focus search in a dual-layer disc. Three
-a is the voltage applied to the focus coil, 3-B ~
3e is a waveform corresponding to, for example, 2-i to 2-l in FIG.

In FIG. 9, the disc type is judged by the focus search shown in FIGS. 6 and 7, and the switch 30 of FIG. 1 is controlled by using the judgment result to control the tracking error of the 3-beam method and the phase difference method. 7 is a flowchart showing an operation procedure of a microcomputer for selecting one of the signals. Up to step S1, the process is the same as in FIG.
The focus search is started at, and the peak voltages V1, V2,
The contents of the registers storing V3 are set to 0 and the timer is started. Then, in step S16, the sum signal S
Digital values obtained by A / D converting the voltage of A are sequentially read, sequentially stored in a predetermined A / D conversion register, and sequentially compared with the previous value. In step S17, step S
As a result of 16 sequential comparisons, it is determined whether or not a peak value is detected. If YES, the peak value is stored in the V1 register in step S18, and if NO, step S16.
Return to

After the end of step S17, step S1
9. Reset the A / D conversion register in step 9, and perform the above step S
Steps S20 and S21 similar to steps S16 and S17 are executed, the next peak value is stored in the V2 register in step S22, and the A / D conversion register is reset in step S23. In the next step S24, it is determined whether or not the time measured by the timer exceeds the set value (overflow), and if it exceeds, the process proceeds to step S28, and if not, the process proceeds to step S25. Steps S25 and S26 have the same contents as steps S16 and 17, respectively.
At 27, the peak value is stored in the V3 register. Step S
At S28, the peak values V1, V2,
A comparison operation is performed using V3.

In the next step S29, V1 is a predetermined value Q1.
It is determined whether it is smaller than V2 or smaller than the predetermined value Q2. If YES, the process proceeds to the abnormality processing routine of step S34. These predetermined values Q1 and Q2 are values sufficiently smaller than the peak value obtained by the focus search on a normal disc. If NO in step S29,
In step S30, it is determined whether or not V1 / V2> Q3 (where Q3 is V that is normally obtained with a disc having a thickness of 1.2 mm).
A predetermined value of a value of, for example, about 70% of the ratio of 1 to V2: This value fluctuates depending on the design of the reproducing device and is
And V2 can be reversed, and so can other similar comparison steps). If YES in step S30, it is determined that the current disc has a thickness of 1.2 mm, a predetermined focus servo control is turned on in step S31, and a tracking error signal by the three-beam method is selected in step S4. On the other hand, if NO in step S30, it is determined in step S32 whether V2 / V1> Q4 (Q
4 is a predetermined value of, for example, a value of about 70% of the ratio of V2 and V1 that is usually obtained with a disc having a thickness of 0.6 mm.

If YES in step S32, it is determined that the current disc has a thickness of 0.6 mm, and step S3
In 3 the predetermined focus servo control is turned on, and in the next step S5 a tracking error signal by the phase difference method is selected. On the other hand, if NO in step S32, step S
At 36, it is determined whether V3> V1 (when V3 is measured) and V2> V1. Step S36
If YES, then in step S37, the focus servo control is turned on at the peak center point C of the waveform shown in 3-C of FIG.
Going to step S5, the phase difference method is selected. Step S
After S4 and S5, the reproduction process is executed in step S6. Although not shown, the operation of turning on the focus servo control in steps S31 and S33 can also detect the disc type during one focus search. Therefore, during focus search, for example, the peak voltage of waveform 2-e The focus servo control can be turned on immediately after the detection of V2, and the focus servo control can be turned on even in the reverse focus search.

Although the peak value V4 is not used in the flow chart of FIG. 9, this is the detection of V3 and its V1, V2.
If it is determined that the disc is a dual layer disc by comparison with
This is because the search time can be shortened by turning on the servo control at the time of V3 before detecting 4. Although not specifically shown in the flowchart of FIG. 9, parameters such as the gain of the circuit for generating the laser power of the optical head, the focus error signal, and the tracking error signal, the offset, and the balance are set according to the disc type that is determined. Alternatively, the characteristics of the equalizer in FIG. 18 described later are appropriately switched and set. Although the amplitude of the sum signal SA is measured here, the voltage value of the S curve of the signals 2-b, 2-f, 2-j, which are the focus error signals FE (symmetrical voltage values on one side or both sides), is measured. The same is true.

FIG. 10 shows one of the tracking error signals of the three-beam method and the phase difference method similar to FIG. 9 in the case where the disc type determination by the focus search uses another method different from the example of FIG. 9 described above. 4 is a flowchart showing an operation procedure of a microcomputer for performing the operation. In the example of FIG. 10, instead of the peak voltages V1, V2, and V3 of FIG. 9, the time width of the portion corresponding to the peak is measured, and the disc type is determined by comparing them. Similar to FIG. 3 up to step S1, the focus search is started in step S15A, the contents of the registers storing the time widths T1, T2, and T3 of each peak are set to 0, and the timer is started. Next, in step S16, digital values obtained by A / D converting the voltage of the sum signal SA are sequentially read, sequentially stored in a predetermined A / D conversion register, and sequentially compared with the previous value. In step S17, as a result of the sequential comparison in step S16,
It is determined whether the peak value is detected. If YES, the time width is stored in the T1 register in step S18A,
If NO, the process returns to step S16.

After the end of step S17, step S1
9. Reset the A / D conversion register in step 9, and perform the above step S
Steps S20 and S21 similar to steps S16 and S17 are executed, the next time width is stored in the T2 register in step S22A, and the A / D conversion register is reset in step S23. In the next step S24, it is determined whether or not the time measured by the timer exceeds the set value (overflow), and if it exceeds, the process proceeds to step S28, and if not, the process proceeds to step S25. Steps S25 and S26 have the same contents as steps S16 and 17, respectively.
The time width is stored in the T3 register at 27A. Step S
In S28A, the time widths T1, T2, obtained so far,
A comparison operation is performed using T3.

In the next step S29A, T1 is a predetermined value Q.
It is determined whether it is smaller than 1 or T2 is smaller than a predetermined value Q2, and if YES, the routine proceeds to the abnormality processing routine of step S34. These predetermined values Q1 and Q2 are values that are sufficiently smaller than the time width obtained by the focus search on a normal disc. If NO in step S29A, it is determined in step S30A whether or not T1 / T2> Q3 (where Q3 is a value of, for example, about 70% of the ratio of T1 and T2 normally obtained with a disc having a thickness of 1.2 mm. Predetermined value).
If YES in step S30A, the current disc is 1.
It is determined that the thickness is 2 mm, the predetermined focus servo control is turned on in step S31, and the tracking error signal by the three-beam method is selected in step S4.
On the other hand, if NO in step S30A, step S32A
To determine whether T2 / T1> Q4 (Q4 is 0.6 m
A predetermined value of, for example, a value of about 70% of the ratio of T2 and T1 that is usually obtained with a disc having a thickness of m).

If YES in step S32A, it is determined that the current disc has a thickness of 0.6 mm, and step S32A is performed.
In 33, a predetermined focus servo control is turned on, and in the next step S5, a tracking error signal by the phase difference method is selected. On the other hand, if NO in step S32, it is determined in step S36A whether T3> T1 (when T3 is measured) and T2> T1. If YES in step S36A, 3-C in FIG. 8 in step S37.
The focus servo control is turned on at the peak center point C of the waveform shown in, and the process goes to step S5 to select the phase difference method. After steps S4 and S5, a reproduction process is executed in step S6.

Although the time width T4 is not used in the flow chart of FIG. 10, this is the detection of T3 and its T1, T2.
If it is judged that the disc is a dual layer disc by comparison with
This is because the search time can be shortened by turning on the servo control at time T3 before detecting 4. Although not particularly shown in the flowchart of FIG. 10, the laser power of the optical head, the focus error signal,
Parameters such as gain, offset, and balance of the circuit that generates the tracking error signal, and FIG.
The characteristics of the equalizer are appropriately switched and set. Here, the time width of the signals 2-c, 2-g, 2-k obtained by shaping the sum signal SA was measured.
2-b, 2-f, 2-j shaped signal 2-d, 2-h, 2-l total time width T1, T2, T3 or minimum value section of ternary signal, middle value section, The same applies when the total time in the maximum value section is measured.

Next, an example using a two-lens type optical pickup (optical head) in which two types of lenses are switched by an actuator so that a DVD and a CD can be reproduced by a single optical pickup will be described. As such an optical pickup, for example, there is a twin-lens optical pickup (exhibited at International Optoelectronics Show '95 <Makuhari Messe International Exhibition Center> on July 11 to 14, 1995) by Mitsubishi Electric Corporation. This optical pickup has two objective lenses, one for DVD and the other for CD. These lenses are attached to a rotatable lens holder, and the lens holder is rotated about an axis by an electromagnetic actuator. A desired lens can be arranged in the optical path.

FIG. 11 is a diagram showing a state of converging a light beam on each disk when the two-lens type optical pickup is used as the optical pickup 2 of FIG. 4-a is t1 =
1.2mm disc, 4-b disc with t1 = 0.6mm, 4-c shows the condensing state on a two-layer disc with one layer of 0.6mm (interlayer distance t3 = 40μm). Narrow beam is for 1.2mm, wide angle beam is 0.6m
It is for m. 12 to 14 show various signal waveforms obtained from the output signals when the focus search is performed by the two-lens type optical pickup 2. That is, FIG.
In FIG. 14, the vertical axis represents voltage, the horizontal axis represents time, and p represents a peak.

In the two-lens type optical pickup, if a lens corresponding to the thickness of the disc is not selected, it cannot be focused on one point due to spherical aberration, and the recording signal of the disc cannot be read. Only 4-aα, 4-bβ, 4-cγ and 4-cδ, which are vertical and horizontal reference symbols, can reproduce signals in FIG. 11. In other cases, the signal cannot be read out,
A certain amount of reflected light returns. FIG. 15 is a block diagram showing an arithmetic circuit (a part of the preamplifier in FIG. 2) used in place of FIG. 1 when a two-lens type optical pickup is used. Regarding the generation of the tracking error signal,
The circuit of FIG. 1 can also be used.

The circuit of FIG. 15 utilizes the circuit shown in FIG. 4 of Japanese Patent Laid-Open No. 57-74837, and the same reference numerals as those in FIG. 1 indicate the same elements. There is. Explaining the points different from FIG. 1, the adder 14
Gate circuits 36 and 40, which are controlled by the output signals of the falling pulse generating circuit 32 and the rising pulse generating circuit 34 in response to the output signals of the respective gates, gate the output signals of the subtracter 16 to hold circuits 38 and 42, respectively. Has been given. The output signals of the hold circuits 38 and 42 are given to the + and-input terminals of the subtractor 44, respectively, and
The output signal of No. 4 is given to the one side terminal of the switch 30. The output signal of the adder 14 is passed through the LPF 28 and the equalizer (EQ) 46, respectively, and the sum signal (S
A), an EFM signal or an EFM plus signal is output.

Therefore, the control signal CO from the microcomputer
When the 0 side of the switch 30 is selected by the NT, the tracking error signal of the three-beam method is output as in FIG. 1, and when the 1 side is selected, the above-mentioned JP-A-57-74 is used.
A tracking error signal similar to that shown in FIG. 4 of Japanese Patent No. 837 is selected. This tracking error signal is a difference signal (output signal of subtractor 16) at both edges (output signal of falling pulse generation circuit 32 and rising pulse generation circuit 34) of the sum signal (output signal of adder 14).
Is sampled to obtain a value obtained by adding a sign corresponding to the direction of deviation of the beam spot from the track to the peak-to-peak value of the difference signal (see FIG. 5 of the same publication).

In FIG. 12, 5-a is the focus coil applied voltage, 5-b is the sum signal SA, 5-c is the focus error signal, and 5-d is obtained by comparing the sum signal SA with the threshold value. Signal, 5-e is an EFM signal when the characteristics of the equalizer 46 are flat, 5-f is a signal obtained by comparing the focus error signal 5-d with a predetermined threshold, and 5-g is an EFM signal comparator. Reference value Re at 50
The signal obtained by comparison with f, 5h is HFDE of FIG.
T (the output signal of the D-FF 56). 13 and 14
Is almost the same as in FIG. The signals 6-i and 7-i in FIGS. 13 and 14 will be described later.

FIG. 16 is a block diagram showing an example of a circuit for detecting the high frequency component HF using the sum signal SA and the EFM signal in the output signals of the circuit of FIG. The EFM signal is given to the comparator 50 and compared with the reference signal Ref. The sum signal SA is given to the D input of the D-FF (flip-flop) 52, its Q output is given to the D input of the D-FF 54 of the next stage, and its Q output is the D of the D-FF 56 of the next stage.
It is given to the input and its Q output is output as the detection signal HFDET. The output signal of the comparator 50 is the D-FF 52.
~ 56 clocks. Reset is each D
-Reset signal of FFs 52 to 56.

The output signal of the comparator 50 in the circuit of FIG.
That is, the signals after comparison of the EFM signals are shown in FIGS.
Shown as 5-g, 6-g, 7-g. D-FF52 ~
56 is a signal 5-d, 6- which is formed by waveform shaping the sum signal SA
Only when D, 7-d is H (high level), the pulse of the output signal of the comparator 50 is counted. In this example, when 3 is counted, the output signal HFDET 5h, 6h, 7h of the D-FF 56 is counted.
-H becomes H. If 3 counts cannot be made within this section, the counter composed of the D-FFs 52 to 56 outputs the sum signal SA.
It is reset by. In this example, 3 counts are used, but the count number can be set to a predetermined number as appropriate.

FIG. 17 shows EF in the output signal of the circuit of FIG.
It is a block diagram which shows the other example of the circuit which detects the high frequency component HF using M signal. The EFM signal is given to the comparator 60 via the HPF 58 and compared with the reference signal Ref. The output of the comparator 60 is given as the clock of the D-FF 62, and its Q output is output as the detection signal HFDET. A predetermined value is constantly given to the D input of the D-FF 62. Reset is a reset signal for the D-FF 62. The circuit of FIG. 17 extracts the high frequency component HF of the EFM signal and latches the signal obtained by comparing this with the reference value Ref. 5-g, 6-g, 7 of FIGS.
-g waveform does not become, but similar waveforms 5-h, 6-h, 7-h
Is obtained. Other than the circuits shown in FIGS. 16 and 17, other configurations can be used as long as they can detect high-frequency components. For example, the input section of the counter section in FIG.
It is also possible to provide a PF.

FIG. 18 is a block diagram showing the structure of a transversal filter as a circuit example of the equalizer 46 shown in FIG. The delay time T and the tap gains G0 to G4 of the unit delay element forming this filter can be controlled by using data stored in advance in a program ROM of a controller (not shown) according to the type of disk. T
As an example, in the case of a 1.2 mm CD, T = 440n
In the case of a DVD of s and 0.6 mm, two of T = 80 ns can be switched. Examples of G0 to G4 are 1.
For a 2 mm CD G2 = 1, G1 = G3 = 0.12,
G0 = G4 = 0, and for a 0.6 mm DVD G0 =
0.02, G1 = 0.2, G2 = 1, G3 = 0.2, G
4 = 0.02, G2 = 1 for removing the frequency characteristic during focus search, and 0 for the others.

The operation of the combination of FIG. 15 and FIG. 16 will be described. Now, as an example, it is assumed that a CD is loaded and a CD lens is selected, or a DVD is loaded and a DVD lens is selected. After turning on the playback device,
The spindle (SP) motor 3 is activated to start the focus search. That is, the voltage applied to the focus coil is gradually increased as shown by 5-a in FIG. 12, the sum signal SA is A / D converted and taken into the microcomputer, and the sum signal SA (5-b in FIG. 12) is obtained. At the same time as reading, the output signal HFDET of FIG. 16 (5-h of FIG. 12) is monitored.

The sum signal SA exceeds a predetermined value, and the signal HF
DET goes high and the focus error signal (5 in FIG.
-c) and monitor the signal 5-f obtained by comparing it with the predetermined value,
The focus servo control is turned on at the time t when this changes from H to L (low level) (corresponding to a so-called almost zero cross point of the so-called S curve in focus search). Further, various parameters of the reproducing apparatus due to the difference in reflectance of each disk, for example, laser power of the optical head, focus error signal, gain of the circuit that generates the tracking error signal, offset, balance, delay time of the unit delay element,
Set tap gain etc. and execute playback process.

In the above configuration, by preparing a plurality of thresholds of the comparator for binarizing the sum signal SA, the write-once type and the recording / reproducing type in which the level of the sum signal SA is different due to the difference in reflectance. It is also possible to detect a disk.
The above description of operation applies to a reproduction-only CD and a single-layer DVD.

Next, the case opposite to the above example, that is, CD
The case where the DVD is loaded and the DVD lens is selected, or the DVD is loaded and the CD lens is selected will be described. After turning on the power of the reproducing apparatus, the spindle (SP) motor 3 is activated to start the focus search. That is, the applied voltage to the focus coil is gradually increased as shown in 6-a of FIG. 13, the sum signal SA is A / D converted and taken into the microcomputer, and the sum signal SA (6-b of FIG. 13) is obtained. At the same time as reading, the output signal HFDET of FIG. 16 (6-h of FIG.
Monitor). However, since the currently selected lens does not match the type of disc, the EFM signal does not include a high frequency component even if the sum signal SA exceeds the predetermined value, and therefore the signal HFDET does not become H. Sum signal SA
The shaping signal 6-d of (6-b) is a signal HFDE during the period of H.
When T does not become H, it is judged that the lens selection is incorrect, and the actuator is controlled to switch the lens to the other. Signal 6-i is for this control. The actuator is controlled by the current supplied to the tracking coil, and the lens is switched when a large current flows.

When the lens switching is completed, the voltage applied to the focus coil is reduced as shown in 6-a,
The objective lens is moved in the opposite direction to the above. In the section where the signal 6-i is H, the lens is switched,
Accurate measurement may be difficult due to unnecessary movement in the focus direction, so the signal HFDET or the like is not monitored. When the lens is switched to be compatible with the disc, the sum signal SA exceeds a predetermined value and the signal HFDET becomes H, and the focus error signal (6-c in FIG. 13) is waveform-shaped, as in the above-mentioned example. The three-valued signal 7-f thus obtained is monitored, and the focus servo control is turned on at a time point t (corresponding to a so-called almost zero-cross point of the so-called S curve in the focus search) when the value becomes the intermediate value from the minimum value. Further, various parameters of the reproducing apparatus depending on the difference in reflectance of each disk, for example, the laser power of the optical head, the gain of the circuit that generates the focus error signal and the tracking error signal, the offset, the balance, the delay time of the unit delay element, and the tap gain. Etc. are set and the playback process is executed.

A modified example of the previous example described with reference to FIG. 12, that is, a modified example of the operation example when the objective lens suitable for the type of the disk is selected from the beginning will be described with reference to FIG. After turning on the power of the playback device, A / D the sum signal SA
The converted data is taken into the microcomputer, the spindle (SP) motor 3 is activated, and the focus search is started. That is, the applied voltage of the focus coil is gradually increased as shown in 7-a of FIG. 14, and the sum signal SA (7-b of FIG.
) Is read, and at the same time, the output signal HFDET of FIG. 16 is read.
(7-h in FIG. 14) is monitored. Even if the sum signal SA exceeds a predetermined value and the signal HFDET becomes H, the focus servo is not turned on here and the applied voltage to the focus coil is gradually decreased as shown in 7-a of FIG.
The sum signal SA is read.

The sum signal SA exceeds a predetermined value, and the signal HF
DET goes high and the focus error signal (7 in FIG.
-c) waveform shaped 3 value signal 7-f obtained by monitoring,
Time t when this becomes the intermediate value from the minimum value (corresponding to almost zero cross point of so-called S curve in focus search)
To turn on the focus servo control. Further, various parameters of the reproducing apparatus depending on the difference in reflectance of each disk, for example, the laser power of the optical head, the gain of the circuit that generates the focus error signal and the tracking error signal, the offset, the balance, the delay time of the unit delay element, and the tap gain. Etc. are set and the playback process is executed. Note that signal 7-i
Is a signal for lens switching corresponding to the signal 6-i in FIG. 13, but in this example it is always L because lens switching during focus search is unnecessary.

Compared with the operation example of FIG. 12, the operation example of FIG. 14 has a higher detection accuracy of the signal HFDET, can further stabilize the mechanical operation, and can simplify the circuit configuration and software of the control system. It is advantageous. Also in the operation described with reference to FIGS. 13 and 14, the sum signal S as described above is used.
By preparing a plurality of thresholds of the comparator for binarizing A, it becomes possible to detect a write-once type disc or a recording / reproducing type disc in which the level of the sum signal SA is different due to the difference in reflectance. Here, FIGS. 12 to 14 show a state in which the amplitude of the sum signal SA is measured, but the same applies when the amplitude of one side or both sides of the focus error signal FE is measured.

In the example using the above-mentioned two-lens type optical pickup, when the lens that does not fit the disc is selected from the two conventional lenses, the focus servo is turned on once and the signal is read even if it is read out. It is possible to determine the disc type by detecting high frequency components during the focus search compared to the method of switching the lens and starting over from the focus search again when it is known that the lens does not match the focus. Since the lens can be switched during the search and the focus servo can be turned on by the search in the reverse direction, the time required to start the reproduction can be greatly shortened.

[0058]

As described above, according to the present invention, C
Provided is a tracking error signal generation device capable of appropriately switching and selecting a tracking error signal generated by a three-beam method and a tracking error signal generated by a phase difference method so as to be suitable for a dual-purpose reproducing device for D and DVD. To be done. Further, there are provided a disc type discriminating device capable of automatically discriminating a disc type for switching the tracking error signal, and a tracking error signal generating device capable of selecting a tracking error signal based on the discrimination result. To be done. In addition, 2
When the lens type optical head is used, it is possible to provide a disc type discriminating apparatus capable of promptly discriminating the disc type and an optical disc reproducing apparatus having a short time until the reproduction is started.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an optical pickup and an arithmetic unit (a part of the preamplifier shown in FIG. 2) that responds to an output signal of the optical pickup in an embodiment of an optical disc reproducing apparatus of the present invention.

FIG. 2 is a block diagram showing an embodiment of an optical disc reproducing apparatus of the present invention.

FIG. 3 is a flowchart showing a processing procedure for discriminating a disc type and switching between two types of tracking error signals according to the discriminating result in the operation of a microcomputer used in the system controller in FIG. Is.

4 is a flowchart showing an example of a processing procedure for switching between two types of tracking error signals in accordance with an operation mode in the operation of a microcomputer used in the system controller in FIG. is there.

5 is another example of a processing procedure for switching between two types of tracking error signals depending on whether the track is on-track in the operation of the microcomputer used in the system controller in FIG. It is a flowchart showing.

FIG. 6 is a diagram showing how a laser beam is focused on a disc by a bifocal optical pickup.

FIG. 7 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed by the optical pickup 2 corresponding to FIG.

FIG. 8 is a waveform diagram showing a focus search in a dual-layer disc.

FIG. 9 shows a microcomputer for discriminating a disc type by a focus search and controlling the switch 30 shown in FIG. 1 by using the discrimination result to select one of the tracking error signals of the 3-beam method and the phase difference method. It is a flowchart which shows an example of an operation procedure.

10 is a diagram illustrating a switch 30 of FIG. 1 that determines a disc type by a focus search and uses the determination result.
6 is a flow chart showing another example of the operation procedure of the microcomputer for controlling one of the three-beam method and the phase difference method tracking error signal by controlling the.

FIG. 11 is a diagram showing how a light beam is condensed on each disk when a two-lens type optical pickup is used.

FIG. 12 is a waveform diagram showing various signal waveforms obtained from output signals when a focus search is performed by a two-lens type optical pickup.

FIG. 13 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed by a two-lens type optical pickup.

FIG. 14 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed by a two-lens type optical pickup.

15 is a block diagram showing an arithmetic circuit (a part of the preamplifier in FIG. 2) used in place of FIG. 1 when a two-lens type optical pickup is used.

16] Sum signals SA and E in the output signals of the circuit of FIG.
It is a block diagram which shows an example of the circuit which detects the high frequency component HF using an FM signal.

17 is a block diagram showing another example of a circuit for detecting a high frequency component HF by using an EFM signal in the output signal of the circuit of FIG.

18 is a block diagram showing a configuration of a transversal filter as a circuit example of the equalizer of FIG.

[Explanation of symbols]

1 Optical Disc 2 Optical Pickup (Optical Head) 3 Spindle Motor 4 Motor Driver / Tracking Focus Control Circuit (Servo Control Means Comprises DSV6 and Focus Search Means Together with System Controller 7) 5 Preamplifier (Including Each Computation Means) , DSV 6 constitutes a signal reproducing means together with 6) DSV (digital servo control circuit) 7 system controller (acts as a controlling means and constitutes a measuring means and a judging means together with other circuits) 10, 12 adder 14 adder ( 16 Subtractor (constitutes second arithmetic means) 18 Subtractor (first arithmetic means) 20 Subtractor 22 Adder 44 Subtractor 24 Delay circuit 26 Multiplier (with delay circuit 24 4 Comprising arithmetic means) 28 LPF (low-pass filter) 30 switch (selection means) 32, 34 pulse generation circuit 36, 40 gate circuit 38, 42 hold circuit 46 equalizer 50, 60 comparator 52, 54, 56, 62 D-FF 58 HPF A, B, C, D phase difference 4-split optical sensor part used in the method E, F 2 two sensor parts used in the beam method

Claims (8)

[Claims]
1. A plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, which are used for the three-beam method and two optical sensor portions and for the phase difference method. An optical head having a four-division optical sensor portion, a first calculation means responsive to output signals from two optical sensor portions used in the three-beam method, and a diagonal line of the four-division optical sensor portion used in the phase difference method. Second calculation means for obtaining a difference signal between the sum signal of the output signals of the two sensor portions and the sum signal of the output signals of the other two diagonal sensor portions; Third computing means for obtaining a sum signal, fourth computing means responsive to the output signals of the second computing means and the third computing means, a low-pass filter responsive to output signals of the fourth computing means, and Output of 1 calculation means A tracking error signal generation device, comprising: a signal and a selection unit that selects one of the output signals of the low-pass filter.
2. A plurality of optical sensor parts for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, the two optical sensor parts used for the three-beam method and the phase difference method. An optical head having a four-division optical sensor portion, a first calculation means responsive to output signals from two optical sensor portions used in the three-beam method, and a diagonal line of the four-division optical sensor portion used in the phase difference method. Second calculation means for obtaining a difference signal between the sum signal of the output signals of the two sensor portions and the sum signal of the output signals of the other two diagonal sensor portions; Third computing means for obtaining a sum signal, fourth computing means responsive to the output signals of the second computing means and the third computing means, a low-pass filter responsive to output signals of the fourth computing means, and Output of 1 calculation means At least one of a selecting means for selecting either a signal or an output signal of the low-pass filter, a means for determining the type of the disk-shaped optical recording medium, and a means for determining whether or not the optical head is on-track. And when the recording density of the disc-shaped optical recording medium is lower than a predetermined value, or when the disc-shaped optical recording medium is a single-layer disc, or when it is a read-only disc,
Further, when the optical head is off-track, the output signal of the first computing means is selected, and when the recording density of the disc-shaped optical recording medium is equal to or higher than the predetermined value, or when the disc-shaped optical recording medium is plural. A layered disc, a recordable disc, and a control means for controlling the selecting means so as to select the output signal of the low-pass filter when the optical head is on-track. apparatus.
3. A plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam and detecting the reflected light, the two optical sensor portions used for the three-beam method and the phase difference method. A bifocal type optical head having a 4-division optical sensor portion, a first calculation means responsive to output signals from the two photosensor portions used in the 3-beam method, and a 4-division optical sensor portion used in the phase difference method. A second computing means for obtaining a difference signal between the sum signal of the output signals of the two sensor portions on the diagonal line and the sum signal of the output signals of the two sensor portions on the other diagonal line; Third computing means for obtaining a sum signal of output signals, fourth computing means responsive to the output signals of the second computing means and the third computing means, and a low-pass filter responsive to output signals of the fourth computing means , The first operator Selection means for selecting one of the output signal of the stage and the output signal of the low-pass filter, focus search means for moving the optical head or its optical system in the focus direction, and two focus points during movement by the focus search means. Measuring means for measuring the first and second detection signals respectively obtained by the third calculating means, and the disc-shaped optical recording using the first and second detection signals measured by the measuring means. A tracking error signal generation device comprising: a discriminating unit that discriminates a type of medium; and a control unit that controls the selecting unit according to the disc type of the optical recording medium discriminated by the discriminating unit.
4. The measuring means measures the voltage of the output signal of the third calculating means, or the time when the voltage of the output signal of the third calculating means is equal to or more than a predetermined value. The tracking error signal generator according to claim 3.
5. When the recording density of the disc-shaped optical recording medium is lower than a predetermined value, or when the disc-shaped optical recording medium is a single-layer disc, according to the discrimination result by the discriminating unit. , Or if it is a read-only disc, select the output signal of the first computing means,
When the recording density of the disc-shaped optical recording medium is equal to or higher than the predetermined value, or when the disc-shaped optical recording medium is a multi-layer disc or a recordable disc, the output signal of the low-pass filter is selected. 5. The tracking error signal generating device according to claim 3, wherein the tracking error signal generating device is configured to control the selecting means.
6. A laser for generating a laser beam for reproducing information from the disc-shaped optical recording medium, and an NA.
An optical head having two different objective lenses, an actuator for selectively arranging the two objective lenses in the optical path of the laser beam, and a plurality of optical sensor portions for detecting reflected light of the laser beam, An arithmetic means responsive to output signals from a plurality of optical sensor portions, a focus search means for moving the optical head or its optical system in a focus direction, and an arithmetic means with one focus during movement by the focus search means. A disc type discriminating apparatus comprising: a measuring unit that measures the amplitude and frequency of the detection signal obtained by the above; and a discriminating unit that discriminates the type of the disc-shaped optical recording medium using the measurement result of the measuring unit.
7. A driving unit for rotating a disc-shaped optical recording medium, a laser for generating a laser beam for reproducing information from the disc-shaped optical recording medium, two objective lenses having different NAs, An actuator for selectively arranging two objective lenses in the optical path of the laser beam, an optical head having a plurality of optical sensor portions for detecting reflected light of the laser beam, and an output signal from the plurality of optical sensor portions. And a servo control means for performing servo control of the optical head according to an output signal of the calculation means, a signal reproduction means for generating a reproduction signal from output signals from the plurality of optical sensor parts, Focus search means for moving the optical head or its optical system in the focus direction; Measuring means for measuring the amplitude and frequency of the detection signal obtained by the calculating means at the focus; a judging means for judging the type of the disc-shaped optical recording medium using the measurement result by the measuring means; When the objective lens currently selected by the determination by the means corresponds to the disc-shaped optical recording medium, the servo control of the servo control means is turned on, while when it does not correspond, After controlling the actuator to switch to another objective lens, the servo control of the servo control means is turned on, and the circuit parameter to be set according to the type of the disc-shaped optical recording medium is determined according to the determined type. An optical disc reproducing apparatus having:
8. A drive unit for rotating a disc-shaped optical recording medium, a laser for generating a laser beam for reproducing information from the disc-shaped optical recording medium, two objective lenses having different NAs, An actuator for selectively arranging two objective lenses in the optical path of the laser beam, an optical head having a plurality of optical sensor portions for detecting reflected light of the laser beam, and an output signal from the plurality of optical sensor portions. And a servo control means for performing servo control of the optical head according to an output signal of the calculation means, a signal reproduction means for generating a reproduction signal from output signals from the plurality of optical sensor parts, Focus search means for moving the optical head or its optical system in the focus direction, and movement in a predetermined direction by the focus search means. Measuring means for measuring the amplitude and frequency of the detection signal obtained by the calculating means at one focus during movement, and a discrimination for discriminating the kind of the disc-shaped optical recording medium using the measurement result by the measuring means. Means and the objective lens currently selected in the discrimination by the discriminating means corresponds to the disc-shaped optical recording medium, the servo control of the servo control means is turned on, while the corresponding If not, after controlling the actuator to switch to another objective lens, the focus search means moves in the direction opposite to the predetermined direction to turn on the servo control of the servo control means, and further, An optical disc comprising: a control unit that sets a circuit parameter to be set according to the type of disc-shaped optical recording medium according to the determined type. Raw devices.
JP35391295A 1995-12-29 1995-12-29 Disc type discriminating apparatus, disc type discriminating method, optical disc reproducing apparatus, optical disc reproducing method Expired - Lifetime JP3284437B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6738326B1 (en) 1999-07-07 2004-05-18 Matsushita Electric Industrial Co., Ltd. Apparatus and method for reproducing information from two types of optical disks having discrimination marks formed along tracks thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6738326B1 (en) 1999-07-07 2004-05-18 Matsushita Electric Industrial Co., Ltd. Apparatus and method for reproducing information from two types of optical disks having discrimination marks formed along tracks thereof
US7057994B2 (en) 1999-07-07 2006-06-06 Matsushita Electric Industrial Co., Ltd. Apparatus and method for reproducing information from two types of optical disks having discrimination marks formed along tracks thereof

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