JPH09274765A - Disk kind determining device and optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a circuit parameter suited for a disk kind by determining the kind of a loaded disk during focus searching and using its result for a reproducing device used for both a CD and a DVD. SOLUTION: First and second detecting signals obtained in two focal points during focus searching by an optical head 2 are measured, and by comparing characteristics between the measured first and second detecting signals, the kind of a disk optical recording medium is determined by a microcomputer in a system controller 7. Alternatively, the kind of a disk is determined by measuring the amplitude and frequency of a detecting signal obtained in a focus during focus searching. After a parameter is set according to the result of the determination, a focus servo control device is switched ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc recording / reproducing apparatus or an optical disc reproducing apparatus for recording / reproducing a signal on / from a disc-shaped recording medium, and particularly discriminating with a disc type discriminating apparatus used in such a device Further, the present invention relates to an optical disc reproducing apparatus capable of changing operating conditions according to the disc type.

[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. 1 as a DVD with a 1.2 mm thick CD and two 0.6 mm thick layers bonded together
It has been proposed to use a bifocal type optical head in order to construct a layer type, two layer type, and phase change type reproducing apparatus for recording and reproducing.

[0003]

When such a bifocal type optical head is used, by so-called focus search,
The disc type cannot be discriminated unless the proper focus position is found and the focus servo control is turned on. In the dual-use playback device, each parameter of the signal processing circuit is appropriately selected and set according to the type of the disc, so that the disc data cannot be reproduced until the disc type is determined. It took a considerable amount of time to start playback.

Therefore, the present invention provides a disc type discriminating apparatus capable of discriminating the type of a disc in a short time so as to be suitable for a dual-use CD / DVD reproducing apparatus using a bifocal optical head. The purpose of 1. Further, the disc type discriminating apparatus capable of discriminating the disc type in a short time can be used to set the circuit parameter according to the disc thus discriminated. Therefore, the optical disc reproducing apparatus has a short time until the reproduction is started. The second purpose is to provide

[0005]

In order to achieve the above first object, the present invention provides a first focus obtained by a two-focus optical head during movement by a focus search means.
And the second detection signal are measured, and the type of the disc-shaped optical recording medium is discriminated using the measured first and second detection signals. Further, in order to achieve the above-mentioned second object, in the present invention, when the focus search means moves,
The first and second detection signals obtained at two focal points with the focus type optical head are measured, and the type of the disc-shaped optical recording medium is discriminated using the measured first and second detection signals, The circuit parameter is set according to the determination result.

That is, according to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium with a laser beam focused on two focal points through an optical system and detecting the reflected light. In a disc type discriminating apparatus used in an optical disc reproducing device, which comprises a focus search means for performing a focus search by moving the optical head or its optical system in a focus direction, and a signal processing means responsive to an output signal from the optical head. Measuring means for measuring properties of a first detection signal and a second detection signal, which are output signals from the optical head obtained at the two focal points during the focus search, and the first measuring signal measured by the measuring means. Discriminating means for discriminating the type of the optical recording medium by comparing the properties of the first detection signal and the second detection signal. Disc type discriminating device is provided that.

Further, according to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disc-shaped optical recording medium so that a laser beam is condensed to two focal points through an optical system and detecting reflected light thereof. In a disc type discriminating apparatus used in an optical disc reproducing device, which comprises a focus search means for performing a focus search by moving the optical head or its optical system in a focus direction, and a signal processing means responsive to an output signal from the optical head. Measuring means for measuring the amplitude and frequency components of the first detection signal and the second detection signal, which are output signals from the optical head obtained at the two focal points during the focus search, and are measured by the measuring means. And a discriminating means for discriminating the kind of the optical recording medium by comparing the amplitude and frequency components of the first detection signal and the second detection signal. Disc type discriminating apparatus, characterized in that it comprises is provided.

Further, according to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is condensed to two focal points through an optical system and detecting reflected light thereof. A focus search means for performing a focus search by moving the optical head or its optical system in a focus direction; a signal processing means responsive to an output signal from the optical head; and an output signal from the signal processing means. In an optical disk reproducing apparatus having servo control means for servo-controlling the optical head, the characteristics of the first detection signal and the second detection signal which are output signals from the optical head obtained at the two focal points during the focus search. The optical recording medium from the comparison of the characteristics of the first detection signal and the second detection signal measured by the measuring means for measuring And a setting means for setting parameters in the signal processing means according to a determination result by the determination means, and a servo-on means for turning on the focus servo control in the servo control means. There is provided an optical disk reproducing device characterized by:

Further, according to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disc-shaped optical recording medium so that a laser beam is condensed to two focal points through an optical system and detecting reflected light thereof. A focus search means for performing a focus search by moving the optical head or its optical system in a focus direction; a signal processing means responsive to an output signal from the optical head; and an output signal from the signal processing means. In an optical disc reproducing apparatus having servo control means for servo-controlling the optical head, amplitudes of a first detection signal and a second detection signal which are output signals from the optical head obtained at the two focal points during the focus search. And measuring means for measuring frequency components, and amplitude and frequency components of the first detection signal and the second detection signal measured by the measuring means. Comparing means for determining the type of the optical recording medium, setting means for setting parameters in the signal processing means in accordance with the determination result by the determining means, and focus servo control in the servo control means. An optical disk reproducing apparatus is provided, which comprises: servo-on means.

According to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting the reflected light is provided. In the disc type discriminating device, the optical head or an optical system thereof is moved in the focus direction to perform a focus search, and a focus error signal generating means responsive to an output signal from the optical head. A differentiating means for measuring the tilt of the focus error signal during the search, and a distinguishing means for distinguishing the type of the optical recording medium by using the tilt of the focus error signal obtained by the differentiating means. A characteristic disc type discriminating apparatus is provided.

Further, according to the present invention, an optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof. A focus search means for performing a focus search by moving the optical head or its optical system in a focus direction; a focus error signal generating means for responding to an output signal from the optical head; and a response for an output signal from the optical head. In order to measure the inclination of the focus error signal during the focus search in an optical disc reproducing apparatus having a signal processing means for controlling the optical head in response to an output signal of the signal processing means. Type of the optical recording medium using the differentiating means and the inclination of the focus error signal obtained by the differentiating means. A discriminating means for discriminating, a setting means for setting a parameter in the signal processing means according to a discrimination result by the discriminating means, and a servo-on means for turning on the focus servo control in the servo control means. There is provided an optical disc reproducing apparatus that does.

[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) that responds to an output signal from the optical pickup (PU). An example of a circuit for selecting one of the error signals is shown.

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. The output signal of the subtractor 20 is given to a well-known focus servo control system so as to be used as the focus error signal FE. 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. Note that the sum signal SA may be output via an LPF (not shown) in order to remove high-frequency components that may be included in the sum signal SA. 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 system controller 7 discriminates the disc type by the operation of a microcomputer (not shown) which will be described later. It should be noted that by switching between two types of tracking error signals according to the result of disc type discrimination according to the present invention, the 3-beam method and the phase difference method can be used separately for a CD having a low recording density and a disc having a high recording density. The microcomputer in the controller 7 generates the control signal CONT according to the type of the disk 1.
That is, when it is determined that the CD has a low recording density,
In order to select the tracking error signal of the 3-beam method, the switch 30 of FIG. 1 is connected to the 0 side and the output signal of the subtractor 18 is output. On the other hand, when it is determined that the disc has a high recording density, the switch 30 is connected to the 1 side to output the output signal of the LPF 28 in order to select the tracking error signal of the phase difference method.

Next, the optical pickup 2 is 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 = 0.38 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. 3 is a diagram showing a state of focusing a laser beam on the disk 1 in such a bifocal type optical pickup. 1-a is a disk with t1 = 1.2 mm, 1-b is t2 =
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. 3, α, β, γ, δ
Shows respective states in which the objective lens of the optical pickup 2 has moved in the focus direction. FIG. 4 shows various signal waveforms obtained from an output signal when a focus search is performed by the optical pickup 2 corresponding to FIG. That is, the vertical axis of FIG. 4 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. 4 are on the disk 1-a in FIG. 3, 2-e to 2-h are on the disk 1-b in FIG. 3, and 2-i.
~ 2-l corresponds to the disk 1-c in Fig. 3, 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 performed 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 in FIG. 4, the peak on the left side in the figure is obtained in the state of α of the disk 1-a in FIG. 3, and the peak on the right side is obtained in the state of β similarly. Thus, the peaks in FIG. 4 correspond to α and β in FIG.
The four peaks at -i to 2-l correspond to α, β, γ and δ of the disc 1-c in FIG. FIG. 5 is a waveform diagram showing a focus search in a dual-layer disc.
The case where the servo control is turned on in the second layer of the 6 mm disk is shown. 3-a is a voltage applied to the focus coil, and 3-b to 3-e are, for example, 2-i to 2-l in FIG.
Is a waveform corresponding to.

FIG. 6 shows the first embodiment of the present invention shown in FIG.
6 is a flowchart showing an operation procedure of a microcomputer for determining the type of disc by the focus search shown in FIG. The operation procedure of the microcomputer for controlling the switch 30 of FIG. 1 to select one of the tracking error signals of the 3-beam method and the phase difference method using the disc type judgment result is shown in the flowchart of FIG. See below. In FIG. 6, 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. Initialization such as clearing predetermined contents of a memory (not shown) or a buffer (not shown) is performed in step S1, and then the focus search is started in step S15 to set the peak voltages V1, V2, V.
The contents of the registers storing 3 are set to 0 and the timer is started. Then, in step S16, the sum signal SA
The digital values obtained by A / D converting the voltage of are sequentially read, sequentially stored in a predetermined A / D conversion register, and compared with the previous value sequentially. In step S17, step S1
As a result of the sequential comparison of 6, it is determined whether or not the peak value is detected. If YES, the peak value is stored in the V1 register in step S18, and if NO, the process returns to step S16.

After step S17 is completed, 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
In 28, each peak value V1, V2, V obtained so far
A comparison operation is performed using 3.

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, predetermined parameter settings are performed in step S40, and then focus servo control is turned on in step S31. on the other hand,
If NO in step S30, V2 / V in step S32
It is judged whether or not 1> Q4 (Q4 is, for example, 70% of the ratio of V2 and V1 which is normally obtained with a disc having a thickness of 0.6 mm.
A predetermined value of the degree value).

If YES in step S32, it is determined that the current disc has a thickness of 0.6 mm, and step S4
1 to set the predetermined parameters, then step S3
In 3, the predetermined focus servo control is turned on. on the other hand,
If NO in step S32, V3> V in step S36
It is determined whether 1 (when V3 is measured) and V3> V2. If YES in step S36,
In step S42, predetermined parameters are set, and then in step S37, the focus servo control is turned on at a time point SC (see waveform 3-e) when the signal indicated by 3-C in FIG. 5 becomes the center value. Although not shown, steps S31 and S3
The operation of turning on the focus servo control of No. 3 can detect the type of the disk during one focus search.
The focus servo control can be turned on immediately after the detection of the peak voltage V2 in step 1, 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 flowchart of FIG. 6, 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. The setting of the predetermined parameters in steps S40, S41, and S42 is performed by the laser power of the optical head, the gain of the circuit that generates the focus error signal and the tracking error signal in the preamplifier 5, and the offset, depending on the disc type that is determined. Parameters such as balance, switching of equalizer characteristics to be described later in the preamplifier 5 or DSV6, delay amount of the unit delay element of the transversal filter in the preamplifier 5 or DSV6, tap gain setting, etc. Is. Here, the equalizer and the transversal filter are the preamplifier 5 or the DSV.
It is assumed to be included in any of the blocks of 6. Although the amplitude of the sum signal SA is measured here, the zero-cross timing of the focus error signal FE may be used when measuring the peak value, or the signal 2-b, 2 which is the focus error signal FE. The same applies when the voltage values of the S curves of -f and 2-j (symmetrical voltage values on one side or both sides) are measured.

FIG. 7 shows an operation procedure of a microcomputer for disc discrimination similar to that of FIG. 6 when another method (second embodiment) different from the example of FIG. 6 is used for disc type determination by focus search. It is a flowchart showing. Figure 7
In the above example, instead of the peak voltages V1, V2, and V3 in FIG. 6, the time width of a predetermined threshold value of the portion corresponding to the peak is measured, and the disc type is determined by comparing them. The process up to step S1 is similar to that of FIG.
Focus search starts at A, and time width T of each peak
Set the contents of the registers that store 1, T2, and T3 to 0
And start the timer. Then in step S16
The 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, it is determined whether or not a peak value is detected as a result of the sequential comparison in step S16. If YES, step S18
The time width is stored in the T1 register at A, and 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 S28A, and if not, the process proceeds to step S25. Steps S25 and S26 have the same contents as steps S16 and 17, respectively, and the time width is stored in the T3 register in step S27A. In step S28A, the respective 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, predetermined parameter setting is performed in step S40, and then predetermined focus servo control is turned on in step S31. On the other hand, step S
If NO in 30A, T2 / T1> Q in step S32A
It is judged whether or not it is 4 (Q4 is a predetermined value, for example, a value of about 70% of the ratio of T2 and T1 which is usually obtained with a disc having a thickness of 0.6 mm).

If YES in step S32A, it is determined that the current disc has a thickness of 0.6 mm, and step S32A is performed.
41, the predetermined parameter setting is performed, and then step S
At 33, a predetermined focus servo control is turned on. On the other hand, if NO in step S32, T in step S36A.
3> T1 (if T3 is measured) and T
It is determined whether or not 3> T2. If YES in step S36A, predetermined parameter setting is performed in step S42, and then, in step S37, the focus servo control is turned on at the peak center point of the waveform shown in 3-C of FIG. 5 (time point SC in waveform 3-e). .

Although the time width T4 is not used in the flow chart of FIG. 7, if the time width T4 is judged to be a two-layer disc by detecting T3 and comparing it with T1 and T2, T4 is used.
This is because the search time can be shortened by turning on the servo control at time T3 before the detection of. Steps S40, S41, and S42 are the same as those in FIG. 6, and the parameter setting is performed according to the disc determined. In addition, here, signals 2-c, 2-
The time width of g, 2-k was measured, but the signal 2-b, 2-f, 2-j which is the focus error signal FE was shaped 2-d, 2
The same applies to the case where the total time of T1, T2, T3, or the minimum value section, the intermediate value section, and the maximum value section of the 3-h signal of -h, 2-l is measured.

FIG. 8 is a flow chart showing a procedure for controlling the switch 30 of FIG. 1 to select the tracking error signal in accordance with the disc type discrimination result of FIG. 6 or 7. When the focus servo control is turned on in step S31, the tracking error signal by the three-beam method is selected in the next step S4. On the other hand, when the focus servo control is turned on in step S33 or step S37, the process proceeds to the next step S5 and the phase difference method is selected. After steps S4 and S5, step S
At 6, the reproduction process is executed. When the tracking error signal of the 3-beam method is selected, the switch 30 of FIG. 1 is connected to the 0 side and the output signal of the subtractor 18 is output. On the other hand, when the tracking error signal of the phase difference method is selected, the switch 30 is connected to the 1 side and the output signal of the LPF 28 is output.

In the first and second embodiments, when comparing the voltage values showing the two peaks or the durations of the two peaks, not the difference between the values but the ratio is used, so that the light quantity of the two focal points is 1 :. This method is suitable not only for the case of 1, but also for the case where the light amounts of the two focal spots are different. Next, 2
3rd suitable especially when the light quantity of the light spot of a focus differs
An example and a fourth example will be described. FIG. 9 is a waveform diagram showing a case where the light amounts of the two focal spots are different. Each waveform 6-a to 6-l corresponds to each waveform 2-a to 2-l in FIG. The third embodiment is a modification of the first embodiment shown in FIG. 6, and the fourth embodiment is a modification of the second embodiment shown in FIG.

In the third embodiment, step S30 and subsequent steps in the flow chart of FIG. 6 are changed as shown in the flow chart of FIG. Also, the fourth embodiment is similar to FIG.
In the flowchart of FIG. 11, step S30A and the subsequent steps are modified as shown in the flowchart of FIG. FIG.
0, if step S30 is YES, the focus search in the direction opposite to the focus search direction in step S15 is started in step S45, and the contents of the registers storing the peak voltages V1, V2, and V3 are set to 0. And start the timer. Next, step S4
In step 6, 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 S47, it is determined whether or not the peak value is detected as a result of the sequential comparison in step S46. If YES, step S4
In step 8, the peak value is stored in the V1 register, and if NO, the process returns to step S46. After the end of step S47, the A / D conversion register is reset in step S49, and steps S50 and S51 similar to steps S46 and S47 described above are performed.
When the peak value is obtained in step S51, the parameter is set in step S52, and then the focus servo control is turned on in step S53.

FIG. 11 showing the fourth embodiment uses peak duration instead of voltage value for peak comparison. In FIG. 11, if step S30A is YES, step S55 is followed by the previous step. The focus search in the direction opposite to the focus search direction in S15A is started, the contents of the registers storing the peak durations T1, T2, and T3 are set to 0, and the timer is started. Next, in step S56, the voltage of the sum signal SA is set to A / D.
Sequentially read the digital values obtained by conversion,
Sequentially stored in the / D conversion register, and sequentially compared with the previous value. In step S57, it is determined whether or not the peak value is detected as a result of the sequential comparison in step S56. YE
If S, it is stored in the peak duration T1 register in step S58, and if NO, the process returns to step S56. After the end of step S57, the A / D conversion register is reset in step S59, steps S60 and S61 similar to steps S56 and S57 are executed, and step S6 is executed.
When the peak value is 1 and the parameter is set in step S62, the focus servo control is turned on in step S63.

FIG. 13 is a waveform diagram for explaining the operation of the third and fourth embodiments. The types of signals in the waveform diagrams 7-a to 7-e are the waveforms 3-a to 3- of FIG. Corresponds to e. However,
A case is shown where a focus search in both directions is performed and a servo control is turned on with a 1.2 mm disk. That is, the current 7-a for driving the objective lens of the optical head gradually increases, and after the objective lens approaches the disk (forward focus search), this time the current decreases and the backward focus search is performed. Done. The timing SC in the waveform 7-e shows the time when the focus servo control is turned on. In addition, 0.6 mm in the third and fourth embodiments
When the servo control is turned on in the second layer of the disk, the waveform is the same as that in FIG. 5 in the first and second embodiments.

Step S5 in the third and fourth embodiments
2 or in the parameter setting of step S62, the laser power of the optical head is changed depending on the disc type that is discriminated.
Parameters such as gain, offset, and balance of the circuit that generates the focus error signal and the tracking error signal in the preamplifier 5 or the preamplifier 5 or D
Switching of the equalizer characteristics described later in SV6,
Similarly, necessary parameters are set in the items such as the delay amount of the unit delay element of the transversal filter in the preamplifier 5 or the DSV 6 and the tap gain setting.

The transversal filter built in the preamplifier 5 or the DSV 6 has a structure as shown in FIG. The delay time T and the tap gains G0 to G4 of the unit delay elements constituting the transversal filter can be controlled by using the data stored in advance in the program ROM of the controller (not shown) according to the type of the disk. As an example of T, in the case of a 1.2 mm CD, T =
In the case of a DVD of 440 ns and 0.6 mm, two of T = 80 ns can be switched. As an example of G0 to G4, in the case of a 1.2 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, G4 = 0.02, G2 = 1 in order to remove the frequency characteristic at the time of focus search, and the others are set to 0.
And keep it.

Next, a fifth embodiment of the present invention will be described. FIG. 16 is a block diagram showing an arithmetic circuit (a part of the preamplifier in FIG. 2) used in the fifth embodiment. Note that the circuit of FIG. 1 can also be used to generate the tracking error signal. The circuit shown in FIG. 16 is disclosed in JP-A-57-7483.
It utilizes what is shown in FIG. 4 of Japanese Patent Laid-Open No. 7-70, and the same reference numerals as those in FIG. 1 indicate the same things. Explaining the points different from FIG. 1, the adder 1
The gate circuits 36 and 40 controlled by the output signals of the falling pulse generating circuit 32 and the rising pulse generating circuit 34 in response to the output signal of 4 gate the output signal of the subtractor 16 and hold circuits 38 and 42, respectively. Is given to. 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 the subtractor 44 is given to the 1-side terminal of the switch 30. The output signal of the adder 14 is output as a sum signal (SA), an EFM signal, or an EFM plus signal via the LPF 28 and the equalizer (EQ) 46, respectively.

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 in which the peak-to-peak value of the difference signal is added with a sign according to the direction of deviation of the beam spot from the track (see FIG. 5 of the publication). ).

FIG. 14 corresponds to FIG. 4, and the portion where the thin lines are dense in the figure shows the high frequency component HF. In FIG. 15, 9-a is the focus coil applied voltage, 9-b is the sum signal SA, 9-c is the focus error signal, 9-d is the signal obtained by comparing the sum signal SA with the threshold, 9 -e is a signal obtained by comparing the focus error signal 9-C with a predetermined threshold, and 9-f is an EFM.
A signal obtained by comparing the signal with the reference value Ref by the comparator 50, 9-g is HFDET (output signal of the D-FF 56) in FIG. The timing SC in the waveform 9-e shows the time when the focus servo control is turned on.

FIG. 17 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 signal after comparison of the EFM signals is shown as 9-f in FIG. The D-FFs 52 to 56 count the pulses of the output signal of the comparator 50 only when the signal 9-d formed by waveform shaping the sum signal SA is H (high level). The output signal HFDET 9-g of the -FF 56 becomes H. When 3 counts cannot be made within this section, the counter composed of the D-FFs 52 to 56 is reset by the sum signal SA or the like. In this example, 3 counts are used, but the count number can be set to a predetermined number as appropriate.

FIG. 18 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. 18 extracts the high frequency component HF of the EFM signal and compares it with the reference value Ref to latch the signal obtained. Other than the circuits of FIGS. 17 and 18, other configurations can be used as long as they detect high-frequency components. For example, an HPF may be provided in the input section of the counter section of FIG. You can also

As the circuit example of the equalizer 46 of FIG. 16, the configuration of the transversal filter shown in FIG. 12 can be used. The delay time T and the tap gains G0 to G4 of the unit delay elements constituting this filter are program RO of a controller (not shown) according to the type of disk.
It is possible to control using the data stored in M in advance. As an example of T, in the case of a 1.2 mm CD, T = 44
In the case of a DVD of 0 ns and 0.6 mm, two of T = 80 ns can be switched. As an example of G0 to G4,
For a 1.2 mm CD G2 = 1, G1 = G3 = 0.1
2, G0 = G4 = 0, and for a 0.6 mm DVD G
0 = 0.02, G1 = 0.2, G2 = 1, G3 = 0.
2, G4 = 0.02, G2 = 1 for removing frequency characteristics during focus search, and 0 for others.

The operation of the combination of FIGS. 16 and 17 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 voltage applied to the focus coil is gradually increased as shown in 9-a of FIG. 15, the sum signal SA is A / D converted and taken into the microcomputer, and the sum signal SA
(9-b in FIG. 15) is read, and at the same time, the output signal HFDET (9-g in FIG. 15) in FIG. 17 is monitored.

The sum signal SA exceeds a predetermined value and the signal HF
DET goes high and the focus error signal (9 in FIG.
-c) and the signal 9-e obtained by comparison with a 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.

The operation of the fifth embodiment is shown in FIG.
It will be described together with the flowchart of. After initializing in step S1, focus search is started in step S15B. In step S16A, the voltage of the sum signal SA is read, stored in the register, and compared with a predetermined value. In the next step S63, it is determined whether or not the sum signal SA is larger than a predetermined value Q5, and if YES, a step S64
Then, it is determined whether or not the edge of the sum signal SA is detected.
If NO in step S63, the process returns to step S16A.
When the edge of the sum signal SA is detected in step S64, the count C of the counter is incremented by 1 in step S65, and the process returns to step S16A. On the other hand, when the edge of the sum signal SA is not detected in step S64, it is determined in step S66 whether HFDET is H or not. If NO, return to step S16A, YES
Then, in step S67, it is determined whether the edge of the focus error signal FE is detected.

When the edge of the focus error signal FE is detected, it is determined in step S68 whether or not the count C is 1, and if it is 1, it is determined that the loaded disc is a CD, which is suitable for a CD. Parameters are set in step S69, and then focus servo control is turned on in step S31. If C = 1 is not satisfied, it is determined in step S70 whether C = 2. If it is 2, it is determined that the disc is a DVD single-layer disc, parameters suitable for it are set in step S71, and then step S33. To turn on the focus servo control. If not C = 2, it is determined in step S72 whether or not C = 3. If it is 3, it is determined that the disc is the first layer of a two-layer DVD, and parameters suitable for it are set in step S73. Then, in step S37, the focus servo control is turned on. The disc type can be determined by the number of counts C in FIG.
This is because the relationship between the number of peaks of the sum signal SA obtained during the focus search and the detection timing of the high frequency component in the EFM signal is constant depending on the type of the disc as shown in FIG.

Similar operation can be obtained by combining FIG. 16 and FIG. 18 instead of the structure combining FIG. 16 and FIG. In each of the above configurations, by preparing a plurality of thresholds of a comparator for binarizing the sum signal SA, 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. It can be detected. The above explanation is for a read-only CD and a single-layer D
This is the case when applied to VD.

Next, a sixth embodiment of the disc type discriminating apparatus and the optical disc reproducing apparatus of the present invention will be explained. This embodiment uses the circuit of FIG. 1 or FIG.
First, the operation principle will be described with reference to FIG. Now
It is assumed that the light focusing state on the optical disc 1 by the bifocal type optical pickup is as shown in FIG. 3 described above. Corresponding to this state, a signal detected when the objective lens is moved to approach the optical disk and the focus search is performed is shown in FIG. In the signal waveform of FIG. 20,
Signals 10-a to 10-d are sent to the disk 1-a in FIG.
~ 10-h corresponds to the disk 1-b in Fig. 3, respectively. Also, α of 1-a in FIG. 3 is va of 10-a in FIG.
The point and β correspond to the vc point. A point vb in FIG. 20 is a signal by the pseudo focus of the bifocal pickup. Similarly, FIG.
Α of 1-b corresponds to the va point of 10-e in FIG. 20, and β corresponds to the vc point. A point vb in FIG. 20 is a signal by the pseudo focus of the bifocal pickup. The sum signal SA of FIG. 1 or 16 is 10-a, 10-e of FIG. 20, and the signals obtained by comparing the sum signal SA with a predetermined reference value are 10-b, 10-f.
Focus error signals FE are 10-c and 10-g, and signals obtained by differentiating them are 10-d and 10-h. It should be noted that these waveforms are shown schematically and are not limited to these waveforms.

Here, for two focal points, 1 in FIG.
With 0-abcd, focus servo control should be turned on (hereinafter simply referred to as servo-on) with a 1.2 mm disc 10-a
It can be seen that, with respect to the point p, the amplitude of 10-a is larger in vc, whereas the amplitude v1 of 10-d which is the slope of the S curve of the focus error signal FE is the largest. At the same time, although not clarified in this figure, the vertical symmetry of the S curve at the point va of 10-c is the most symmetrical, and the points vb and vc are not so symmetrical. Therefore, in addition to v1, v1a,
By comparing the level of v1b and the level of v1 with other vb and vc, the disc type can be more clearly discriminated.

In 10-efgh of FIG. 20, with respect to the p point of 10-e where the servo should be turned on with a 0.6 mm disk, 10-e
Vc has a larger amplitude, and the focus error signal F
The amplitude v3 of 10-h, which is the slope of the S curve of E, is also the largest. At the same time, although not shown in this figure, the vertical symmetry of the S curve at the vc point of 10-g is the most symmetric, and
The points a and vb are not so symmetrical. Therefore, in addition to v3, by comparing the levels of v3a and v3b and the level of v3 with other va and vb, the disc type can be more clearly discriminated. The reason for this is that it can be seen that the pseudo spot is in a blurred state due to aberrations and other factors with respect to the original spot.

A transversal filter (equalizer in FIG. 16) built in the preamplifier 5 in FIG. 2 (T of the unit delay element is 440 ns, 0.6 for a 1.2 mm CD)
In the case of a DVD of 80 mm, two taps of 80 ns can be switched).
For example, when the gain of G2 is 1, G1, G3 = 0.12,
If G0 and G4 are set to 0 and a 0.6 mm disk is used, for example, G0 = 0.02, G1 = 0.2, G2 = 1, G3 =
0.2, G4 = 0.02, G2 = 1 in order to remove the frequency characteristic at the time of focus search, and 0 for others, so that the program ROM of the controller is set in advance.
To memorize it.

The specific operation of the sixth embodiment will be described with reference to FIG. The signal waveform 11-bcde in FIG. 21 is 10-abcd in FIG. 20, and 11-ghij in FIG. 21 is 10-abcd in FIG.
It corresponds to each efgh. In addition, 11-a, 1 in FIG.
1-f shows the change in the voltage supplied to the focus coil. In the whole block of FIG. 2, the sum signal SA generated by the preamplifier 5 and indicated by 11-b and 11-g in FIG.
And 11-d and 11-i of FIG. 21 generated by the preamplifier 5.
The focus error signal FE indicated by
It is sampled by the D converter and taken into the CPU of the system controller 7 as a digital signal. When the sum signal SA exceeds the predetermined threshold from the time when the focus search is started by increasing the voltage supplied to the focus coil (see 11-a, 11-f) (11-c, 11-h in FIG. 21). 21-d, 11-i of FIG. 21 are sampled in the H level section of FIG. 21 and the amplitude of the signal showing the difference from the previously sampled value, that is, the differential signal, 11-e, 11-j Remember. Since the sum signals 11-b and 11-g are actually A / D converted and processed as digital signals, the signals 11-c and 11-
h is a schematic timing signal that is not output as a signal, and signals 11-e and 11-j are also schematic signals that differentiate the A / D conversion value and are not output as a signal.

After storing the amplitudes of the signals 11-e, 11-j, v1, v2, v3 (or v1v1av1b, v2) in the H level section of the three peaks va, vb, vc during the search.
v2av2b, v3v3av3b) is the maximum signal, and if the result is v1, it is determined to be CD, and if it is v3, it is determined to be DVD, and the focus search is performed in the reverse direction to the target va or vc. When the focus error signal FE of 11-d and 11-i reaches the reference voltage, the servo-on process is performed. Note that each parameter (gain in preamplifier, laser power, offset, balance, delay amount of unit delay element of transversal filter, tap gain value, depending on the disc type discriminated together with or before servo-on processing Etc.) is set in a servo block (not shown), and reproduction processing after the focus servo is turned on is performed.

Next, according to the flowchart of FIG.
The actual operation of the embodiment will be described. First, the registers are reset by initialization (step S1), and the voltage supplied to the focus coil is increased to start the forward focus search (step S82). When the focus search is started, the sum signal SA and the focus error signal FE are sampled for A / D conversion (step S83). Next, the sum signal SA is compared with a predetermined value to determine whether it has become H (high) (step S84),
If it is H, the minimum value of the focus error signal FE minus the current value of the focus error signal FE = FED is stored in the memory as v1 (step S85). If not H, the process returns to step S83.

The following steps S86 to S88 and steps S89 to S91 subsequent to step S88 are the same operations as steps S83 to S85, and each FED = F.
The minimum value of the previous value of E-the current value of FE is stored as v2 and v3, respectively. Thus, the three minimum values v1, v
After 2 and v3 are stored, the minimum value among these three minimum values v1, v2 and v3 is determined in step S92. The minimum value is, for example, v1 for 11-abcde in FIG. 21 and v3 for 11-fghij in FIG. After this determination, the supply voltage to the focus coil is reduced and the focus search in the reverse direction is started (step S93). In step S94, the counting of the number n of times when the sum signal SA becomes H is started. Here, if the minimum value is v1, n = 3, and if the minimum value is v3, n = 1. Go to step S96. If these conditions are not met, step S94.
Return to

In step S96, the focus error signal FE is measured, and the focus servo control is turned on when the reference voltage (center value) is reached after passing through the lower peak.
In the next step S97, the count of the SA counter that counts the number of times SA = H is checked, and if n = 3, it is determined that v1 is the minimum value and the loaded disc is a CD. If n = 1, v3 is the minimum value, and it is determined that the loaded disc is a DVD, and parameters (preamplifier gain, laser power, offset, balance, transversal filter The delay amount of the unit delay element, the tap gain value, etc.) are set in a servo block (not shown).

Since the count is 3 in the example of the waveform 11-abcde in FIG. 21, a transversal filter (T of the unit delay element is 80 nS for a DVD of 0.6 mm) is used, and the tap gain is a value for a 0.6 mm disc. , For example, G0
= 0.02, G1 = 0.2, G2 = 1, G3 = 0.
2, G4 = 0.02 is set. Step S
After setting the parameters in 97, the normal reproduction process after the focus servo is turned on is performed.

In the sixth embodiment, the differential signals 11-e, 11-
j is obtained as the difference between the focus error signal FE and the digital signal after A / D conversion. The focus error signal FE signal before A / D conversion is differentiated through an analog differentiating circuit, and the differentiated signal is A / D converted. It may be an embodiment (seventh embodiment) configured to perform conversion.

Further, in the sixth embodiment, the voltages v1, v2, v3 are
Only, that is, only the peak values below the 0 level (negative peak values) were compared with each other, but the positive voltage v1
By including a, v1b, that is, a peak above the 0 level as a comparison target, it is possible to determine whether the symmetry of the S curve is good or bad. The detection accuracy can be improved by such a method. In the eighth embodiment as an example, v1 + v1
a + v1b, v2 + v2a + v2b, v3 + v3a + v
3b are compared with each other. In this case, for example, v1a and v1
Only when both b exceed a certain threshold level, the level of v1 is determined. For example, when either v3a or v3b does not exceed a certain threshold value, it is different from the original spot.
3 = 0. Thereby, erroneous detection can be prevented.

In the sixth to eighth embodiments, the voltages v1, v2 and v3 showing the slopes of the respective peaks are detected, but the waveform 3
It is also possible to use a predetermined voltage threshold above or below -e, 3-j and measure the time when the predetermined voltage threshold is exceeded. Such a changing mode is referred to as a ninth embodiment. That is,
Since the focus error signal FE of the original spot has a steeper slope as compared with the pseudo signal, there is a property that the time for exceeding the threshold value is shorter than the corresponding time for the pseudo signal. By utilizing this property, the original light spot can be measured accurately and stably.

In each of the above-mentioned embodiments, the processing of the pseudo signal detected by other than the two light spots of the two focal points is omitted as described in JP-A-7-98431. However, for example, the waveforms 2-a and 2-e in FIG. 4 and the waveforms 6-a, 6-e and FIG.
Waveform 7-a in FIG. 3, waveforms 8-a and 8-e in FIG. 14 when a signal having an intermediate level between V1 and V2 exists between peak values V1 and V2, or waveform 2-i in FIG. Waveform 3- in Figure 5
b, waveform 6-i in FIG. 9, waveform 7-a in FIG. 13, waveform in FIG.
8-i, when there is a signal of a level intermediate between V2 and V3 between the peak values V2 and V3 in the waveform 9-b of FIG. 15, the peak levels of the peaks of 2 to 4 in the first to fourth embodiments. Alternatively, although the time width is measured, it is also possible to measure the pseudo signal in the same manner and compare the level ratio and the time width ratio including this measured value. In this case, the calculation becomes slightly complicated, but the disc identification accuracy may be improved in some cases. Further, in the fifth embodiment, the disc type is discriminated by using the number of signal peaks and the detection timing of the high frequency component, but in the case of the pseudo signal, the peak level can be detected but the high frequency component is not included. The count value determination criterion may be changed by appropriately changing the flowchart of 19.

[0065]

As described above, according to the present invention, C
The disc type and the layer type can be discriminated during the focus search so as to be suitable for a D / DVD dual-purpose reproducing apparatus. The focus servo control can be turned on after properly setting the parameters and the like necessary for reproduction using this determination result. Further, the tracking error signal generated by the 3-beam method and the tracking error signal generated by the phase difference method can be appropriately switched and selected according to the determination result. According to the present invention, the disc type can be quickly discriminated, so that it is possible to provide an optical disc reproducing apparatus in which the time required for starting reproduction is short.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an embodiment of an optical disk reproducing apparatus (including a disk type discriminating apparatus) of the present invention.

FIG. 3 is a diagram showing how a laser beam is focused on a disc by a bifocal optical pickup.

FIG. 4 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed by an optical pickup corresponding to FIG.

FIG. 5 is a waveform diagram showing a focus search in a dual-layer disc.

6 is a processing procedure (first embodiment) for discriminating a disk type in the operation of a microcomputer used in the system controller shown in FIG. 2;
It is a flowchart which shows.

7 is a processing procedure (second embodiment) for discriminating a disk type in the operation of a microcomputer used in the system controller shown in FIG. 2;
It is a flowchart which shows.

FIG. 8 is a microcomputer for determining the disc type by focus search and controlling the switch 30 of FIG. 1 using the determination 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 the other example of an operation procedure.

FIG. 9 is a waveform diagram showing a case where the light amounts of the light spots of two focal points are different.

10 is a diagram showing the operation of a microcomputer used in the system controller shown in FIG.
It is a flowchart which shows a part of processing procedure (3rd Example) for discriminating a disk type.

FIG. 11 is a view showing the operation of the microcomputer used in the system controller in FIG.
It is a flowchart which shows a part of processing procedure (4th Example) for discriminating a disk type.

12 is a block diagram showing a configuration of a transversal filter included in the preamplifier or DSV of FIG.
17 is also a block diagram showing the configuration of a transversal filter as an example of the circuit of the equalizer of FIG.

FIG. 13 is a waveform diagram when focus search is performed in the forward direction and the reverse direction in the third and fourth embodiments.

FIG. 14 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed by an optical pickup corresponding to FIG.

FIG. 15 is a waveform diagram showing various signal waveforms obtained from an output signal when a focus search is performed in the fifth embodiment of the present invention.

16 is a block diagram showing an arithmetic circuit (a part of the preamplifier in FIG. 2) used in place of FIG. 1 in the fifth embodiment of the present invention.

17 is a sum signal SA and E of 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.

FIG. 18 is a block diagram showing another example of a circuit for detecting a high frequency component HF using an EFM signal in the output signal of the circuit of FIG. 16.

FIG. 19 is a block diagram showing the operation of a microcomputer used in the system controller shown in FIG.
It is a flowchart which shows a part of processing procedure (5th Example) for discriminating a disk type.

FIG. 20 is a waveform diagram showing various signal waveforms obtained from the output signal when a focus search is performed by the optical pickup corresponding to FIG. 3.

FIG. 21 is a waveform diagram showing focus searches on two types of discs.

22 is a diagram showing the operation of the microcomputer used in the system controller shown in FIG.
It is a flow chart which shows a processing procedure (sixth example) for discriminating a disc type.

[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) , And a signal processing means together with the DSV 6) 6 digital servo (DSV) control circuit (constituting servo-on means together with the system controller) 7 system controller (measuring means, discriminating means, setting means together with other circuits which operate as control means) 10, 12, 14, 22 adder 16, 18, 20, 44 subtractor 24 delay circuit 26 multiplier 28 LPF (low-pass filter) 30 switch 32, 34 pulse generation circuit 36, 40 gate circuit 38, 42 E Circuit 46 equalizer 50, 60 comparator 52, 54, 56, 62 D-FF 58 HPF (high-pass filter) A, B, C, D four-division optical sensor portion used for phase difference method E, F used for 3 beam method Two sensor parts

Claims (8)

[Claims] 1. An optical head having a plurality of optical sensor portions for irradiating a disc-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof, and the optical head or In a disc type discriminating apparatus used in an optical disc reproducing apparatus having a focus search means for moving the optical system in the focus direction to perform a focus search and a signal processing means for responding to an output signal from the optical head, Measuring means for measuring the properties of the first detection signal and the second detection signal which are output signals from the optical head respectively obtained at the two focal points; and the first detection signal and the first detection signal measured by the measuring means. Two
A disc type discriminating apparatus comprising: discriminating means for discriminating the type of the optical recording medium based on comparison of properties of detection signals. 2. The measuring means measures the voltage of the first detection signal and the second detection signal, or the time when the voltage of the first detection signal and the second detection signal is a predetermined value or more. The disc type discriminating apparatus according to claim 1, which is for measuring. 3. An optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof; In a disc type discriminating apparatus used in an optical disc reproducing apparatus having a focus search means for moving the optical system in the focus direction to perform a focus search and a signal processing means for responding to an output signal from the optical head, Measuring means for measuring the amplitude and frequency components of the first detection signal and the second detection signal, which are the output signals from the optical head respectively obtained at the two focal points, and the first detection measured by the measuring means. Signal and second
A disc type discriminating apparatus comprising: discriminating means for discriminating the type of the optical recording medium from the comparison of the amplitude and frequency components of the detection signal. 4. An optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof, and the optical head or In a disc type discriminating apparatus having a focus search means for performing a focus search by moving the optical system in the focus direction, and a focus error signal generating means for responding to an output signal from the optical head, the focus is searched during the focus search. Disc type characterized by comprising differentiating means for measuring the inclination of the error signal, and discriminating means for discriminating the type of the optical recording medium using the inclination of the focus error signal obtained by the differentiating means. Discriminator. 5. An optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof, and the optical head or Focus search means for performing a focus search by moving the optical system in the focus direction, signal processing means responsive to an output signal from the optical head, and servoing the optical head in response to an output signal from the signal processing means. An optical disk reproducing apparatus having a servo control means for controlling, a measuring means for measuring properties of a first detection signal and a second detection signal which are output signals from the optical head obtained at the two focal points during the focus search. And the first detection signal and the second detection signal measured by the measuring means.
Discriminating means for discriminating the type of the optical recording medium based on comparison of properties of detection signals, setting means for setting parameters in the signal processing means according to the discrimination result by the discriminating means, and focus servo control in the servo control means. An optical disc reproducing apparatus, comprising: a servo-on means for turning on. 6. The measuring means measures the voltage of the first detection signal and the second detection signal, or the time when the voltage of the first detection signal and the second detection signal is a predetermined value or more. The optical disk reproducing apparatus according to claim 5, which is for measuring. 7. An optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof, and the optical head or Focus search means for performing a focus search by moving the optical system in the focus direction, signal processing means responsive to an output signal from the optical head, and servoing the optical head in response to an output signal from the signal processing means. In an optical disk reproducing apparatus having a servo control means for controlling, the amplitude and frequency components of the first detection signal and the second detection signal which are output signals from the optical head obtained at the two focal points during the focus search are measured. Measuring means, and the first detection signal and the second detection signal measured by the measuring means.
Discriminating means for discriminating the type of the optical recording medium from the comparison of the amplitude and frequency components of the detection signal, setting means for setting parameters in the signal processing means according to the discrimination result by the discriminating means, and the servo control means. An optical disk reproducing apparatus comprising: a servo-on means for turning on focus servo control. 8. An optical head having a plurality of optical sensor portions for irradiating a disk-shaped optical recording medium so that a laser beam is focused on two focal points through an optical system and detecting reflected light thereof, and the optical head or Focus search means for performing a focus search by moving the optical system in the focus direction, focus error signal generation means for responding to an output signal from the optical head, and signal processing means for responding to an output signal from the optical head. An optical disc reproducing apparatus having servo control means for servo-controlling the optical head in response to an output signal of the signal processing means, a differentiating means for measuring an inclination of the focus error signal during the focus search, Discriminating means for discriminating the type of the optical recording medium using the inclination of the focus error signal obtained by the differentiating means The setting means for setting a parameter in the signal processing means in accordance with the discrimination result by the discrimination unit, an optical disk reproducing apparatus, characterized in that the servo-on means, with which the focus servo control and ON in said servo control means.