JPH06325482A - Optical disk discriminating device - Google Patents

Abstract

PURPOSE:To easily and surely discriminate optical disks without receiving the influence of a variation among the optical disks and devices. CONSTITUTION:This optical disk discriminating device is provided with means 14, 15 which detect information reading signals with an envelope detector 13 and produce RF sense signals to investigate the presence or absence of RF signals. A CPU 29 which is a discrimination control means discriminates the RF signals as to whether the first optical disk or not and inverts the polarities of the RF signals, tracking error signals and focus error signals when the signals do not correspond to the first optical disk. Further, confirmation is made by the RF sense signals that the optical disk is the second optical disk. The sure discrimination is executed even in the case of the disks having, for example, a small difference in reflectivity when the polarities of the reflectivity of the first optical disk and the second optical disk vary.

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, an LD (Laser Di
sk) and phase change type W / O (Write
Once) relates to an optical disc discriminating apparatus for discriminating a plurality of types of information recording / reproducing media such as discs.

[0002]

2. Description of the Related Art Generally, there are various types of optical discs such as compact discs and video discs, which are widely used for reproduction, and write-once media that can be written to, and rewritable media that can be freely recorded and reproduced. , Several types of media have been developed according to the method application. In these media, recording of signals is performed by providing pits and recording rows on the recording surface. There are two types of pit recording, one that uses shape changes such as holes and bulges, one that uses changes in the crystalline and non-crystalline phase states, and one that uses the magneto-optical effect as seen in the rewritable type. To do. As a method of distinguishing information, a method of reading by changing the reflected light amount of the irradiated laser light such as a pit which is a signal portion and a groove which is a non-signal portion, and a polarization plane rotation of the reflected laser light are detected. There is a method using magneto-optics.

In the above optical disk recording / reproducing apparatus, the basic optical configuration is the same regardless of the writing or reading method. The writing and reading methods require the above-described highly accurate optical system and a complicated servo mechanism, and the unit cost of the pickup portion and the servo mechanism is expensive. Therefore, with the development of the various recording media described above, it is not a good idea to prepare a dedicated recording / reproducing device for each different type of disc. Therefore, in order to share the basic part of the optical system, there is an increasing demand for a so-called compatible player that can use a plurality of different types of discs in a single optical disc recording / reproducing device.

Now, in the optical disk recording / reproducing apparatus,
It is an important factor to properly grasp the reflectance of the optical disc. In the focus servo circuit and the tracking servo circuit, which are important servo mechanisms of the optical system, it is necessary to switch the input signal level of the reflected light to an appropriate gain according to the reflectance. If this goes wrong, a stable servo effect cannot be expected. However, when the recording media are different, the reflectance with respect to the laser beam is usually different.
Therefore, in the case of an optical disc recording / reproducing device that supports a plurality of types of media, an optical disc discriminating device that discriminates the type of the optical disc to be recorded / reproduced is provided, and the necessary amplification factor of the input signal can be set according to the reflectance of the optical disc. Must be set.

A conventional optical disc discriminating apparatus will be described with reference to the drawings. In the conventional example shown in FIG. 8, the optical disc 1 and the optical disc 2 having different reflectances are discriminated. In the figure, for simplicity, only the circuit portion necessary for the description is shown. In FIG. 8A, the light receiving unit 8 is a photoelectric conversion element, and is divided into four in order to perform focus servo by a known astigmatism method. R3 to R7 are resistors and C
Reference numeral 4 represents a capacitor, and 102 represents a differential amplifier. Resistor R
3 to R7, the capacitor C4, and the differential amplifier 102 are combined to form a summing amplifier and a low-pass filter. That is, the DC component of the amount of total reflected light that has entered the light receiving unit 8 appears on the output side of the differential amplifier 102. This output is adjusted to an appropriate voltage level by the VR1 level adjuster, and one of the adjusted outputs is input to the comparator 103 and compared with the threshold value Vth3 to obtain the judgment output voltage Va. The other of the adjusted outputs is input to the comparator 104 and compared with the threshold value Vth4 to obtain the judgment output voltage Vb. The threshold values Vth3 and Vth4 are calculated by the formula 1-
If the relationship of 1 is selected, the type of the optical disc can be determined based on the voltage levels of the determination output voltages Va and Vb as shown in FIG. 8B. In FIG. 8B, H indicates a high level output and L indicates a low level output.

Vd1>Vth3>Vd2> Vth4 --- (1-1) Reflected light input voltage in the comparator 103 of the optical disc 1:
Vd1 Reflected light input voltage in the comparator 104 of the optical disk 2:
Vd2 Discrimination means to which the above conventional example is applied is disclosed in, for example, Japanese Patent Laid-Open No.
-98324.

[0007]

However, in the above-mentioned conventional optical disc discriminating apparatus, there is a possibility that erroneous discriminating may be performed due to large variations in reflectance of manufactured optical discs and variations in pickups and light receiving portions. That is, in the above formula 1-1, if there is a variation in the reflectance between the optical disks that happened to be used during the adjustment, Vth
3 and Vth4 may vary greatly. In addition, if there are variations in the pickup performance or the sensitivity of the light receiving unit between the devices, even if the same optical disc is used, Vd1 and Vd
2 varies from device to device. In order to avoid the above-mentioned adverse effects, it is necessary to take measures such as performing adjustment with a standard disk for each device, providing a circuit configuration capable of readjusting the threshold voltage due to the variation of each device, and the like. There were problems such as an increase in the number of points and adjustment points and a decrease in reliability.

It is an object of the present invention to provide an optical disc discriminating apparatus which can easily and surely discriminate an optical disc without being affected by variations between optical discs and devices.

[0009]

In order to solve the above problems, the present invention provides an envelope detection output of an information reading (hereinafter referred to as RF = Radio Frequency) signal obtained when an optical disc is rotated. The following configuration is made by utilizing the fact that a very large level difference may occur in optical discs having different magnitude relationships between the reflectance of light and the reflectance of light in the non-signal portion.

That is, the above-mentioned objects are: a read signal detecting means for detecting the presence or absence of an information read signal of an optical disc to be discriminated, and a tracking error for generating a tracking error signal according to the displacement amount from the signaled portion or the non-signaled portion. It has a generation means and a signal polarity reversal function of the tracking error signal in the input stage, and when the tracking servo loop is closed, tracking servo can be performed on a signal part of an arbitrary optical disk regardless of the magnitude relation of the reflectance. An optical disc discriminating control device comprising: a tracking servo unit; and a discriminating control unit for discriminating an output result of the read signal detecting unit, and discriminating a polarity of an input stage of the tracking servo unit when there is no read signal. Achieved by

[0011]

According to the present invention, when the tracking servo is closed with the polarity of one of the optical discs, the levels of the RF signals obtained by the first optical disc and the second optical disc are greatly different from each other, and the reflectance is reduced. The optical disc can be easily and surely discriminated without being affected by the variation of the reflectance of the optical disc and the variation between the optical disc recording / reproducing devices, which have been problems in the conventional discriminating device using the size as the determination condition.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. As the recording / reproducing optical disk in this embodiment, consider an LD as the one corresponding to the first optical disk and a W / O disk as the one corresponding to the second optical disk. Therefore, the present embodiment is an optical disc discriminating apparatus in a compatible player capable of recording and reproducing both discs. (I) First Embodiment FIG. 1 shows a first embodiment of the present invention. As shown in the figure, the light receiving portion 8 is composed of photoelectric conversion elements, and is composed of light receiving elements arranged so as to be divided into four parts. This is provided for performing focus servo by the astigmatism method. Light receiving portion 8 and photoelectric conversion elements 9, 10 described later
Is provided in a pickup (not shown). The laser beam irradiated on the recording surface of the optical disc is reflected,
In the light receiving portion 8, it is converted into an electric signal by the photoelectric effect.

Outputs from a pair of light receiving elements arranged symmetrically among the above light receiving elements are connected to a differential amplifier 11 via a capacitor C1. The outputs from the remaining one pair of the light receiving elements are connected to the differential amplifier 11 via C2. This output is an RF signal that is the sum of the AC components of the electrical signal excited by the amount of total reflected light received by the light receiving unit 8.

The RF signal is amplified to an appropriate size by the differential amplifier 11 and output. The output is branched into two directions, one of which is input to the n-fold amplifier 12 and amplified to n-fold, and then the switch SW1. And the other is supplied to the switch SW1 without passing through the n-fold amplifier.

The switch SW1 is a CPU (Central Pr
ocessing Unit: Central processing unit) LD / W / from 29
By the O switching command S, the n-times amplifier 12 side and the side not passing through the amplifier are selected, and an RF signal is supplied to a video signal control system (not shown).

The other of the branched RF signal outputs of the amplifier 11 enters the envelope detector 13, is RF-detected, and is included in the RF detection output by the low-pass filter 14 formed by the resistor R1 and the capacitor C3.
The frequency component becomes an attenuated DC component and is input to the comparator 15. In the comparator 15, the DC component output from the low pass filter 14 is compared with an appropriate reference voltage Vth1 and supplied to the CPU 29 as a high level or low level output signal.

At the same time, of the four light-receiving elements of the light-receiving section 8, the outputs of a pair of light-receiving elements located at the target position are connected to the positive input (+) side of the differential amplifier 16, and the remaining other elements are connected. The outputs of the pair of light receiving elements are connected to the negative input (−) side of the differential amplifier 16.
The output sum of both signals, which is the output of the differential amplifier 16, is used to hold the objective lens 6 so that the optical disc whose position is set in the optical system and the objective lens 6 have the optimum distance relationship by the astigmatism method. Of the focus error (FE) signal.

Further, the focus error signal is branched into two, one of which is connected to the n-fold inverting amplifier 17 to switch SW2.
, And the other is supplied to the switch SW2 without passing through the n-fold inverting amplifier 17. Switch SW2
In response to the LD / W / O switching command S supplied from the CPU 29, the
The side not passing through the double inverting amplifier 17 is selected. The output of the switch SW2 is supplied to the focus servo circuit 18.

The focus servo circuit 18 receives the focus-on command from the CPU 29, closes the focus servo loop, drives the focus coil 19, drives the objective lens 6, and performs proper focus servo. When the focus servo is performed and the focus is adjusted to an appropriate position, a focus lock signal is output to the CPU 29.

On the other hand, the respective outputs of the photoelectric conversion elements 9 and 10 are supplied to the differential amplifier 20 to derive a difference signal between the two outputs, and the difference signal becomes a tracking error (TE) signal. Sub-beam reflected light from the optical disk is incident on the photoelectric conversion elements 9 and 10, and tracking servo is performed using a so-called three-beam method device. That is, two sub-beams are prepared in addition to the main beam for reading information information, and these beams are arranged so that the line connecting the optical axes thereof has a predetermined offset angle with respect to the close battle direction of the track. Thus, an error signal is generated by detecting the light amount difference between the two sub beams passing through the recorded information surface of the optical disc.

The tracking error signal is branched in two directions, one of which is inverted by the inverting amplifier 21 to be amplified by n times and supplied to the switch SW3, and the other of which is directly switched without passing through the inverting amplifier 21. It is supplied to the container SW3. The switch 3 is the LD / W / from the CPU 29.
Select either one by O disk switching command,
The output is input to the tracking servo circuit 22.

The tracking servo circuit 22 includes the CPU 2
The tracking servo loop is closed in response to the tracking-on command from 9, and the actuator 23 is driven to cause the objective lens 6 to follow the track on the optical disk in accordance with the tracking error signal generated corresponding to the eccentricity of the optical disk. A zero-cross detector (not shown) in the tracking servo circuit 22 compares an appropriate threshold value with a tracking error signal to generate a tracking zero-cross signal and supplies it to the CPU 29.

Further, the output of the tracking servo circuit 22 is supplied to a slider servo circuit 24, which receives a scan command from the CPU 29 and drives a slider motor 25 which moves the entire pickup in the radial direction of the optical disk.

The rotation of the optical disc is controlled by
The time base servo circuit 26. The time-base servo circuit 26 receives the spindle-on command supplied from the CPU 29, drives the spindle motor 27 and the tacho-generator 28, and rotates the optical disc in accordance with the target rotation speed. Further, in response to an FG servo ON command from the CPU 29, the speed of the motor 27 is adjusted.

The characteristics of the optical disk in this embodiment will be described with reference to FIG. As shown in (a), the row of ellipses in the figure is a pit row (track) for recording information, and the alternate long and short dash line is the center line of the track. The row of broken lines is a non-recording portion between tracks called a groove. (B) is the RF signal strength when the LD is the disc to be discriminated, and is the output (point D in FIG. 1) of the envelope detector 13 in FIG. It is considered that this is proportional to the total reflected light amount of the laser beam. (C) is a tracking error signal in the case of LD, which corresponds to the output (FE) of the differential amplifier 20 in FIG. Similarly, (d) is W
The RF signal strength when the / O disc is the disc to be discriminated, and (e) is the tracking error signal in the case of the W / O disc.

As can be seen from the figure, since the LD is an optical disk in which an aluminum reflecting screen is vapor-deposited on a row of concave and convex pits, the irradiated laser beam is diffracted by the pits on the track having the pits, and the amount of reflected light becomes low. Since there is no diffraction due to pits on the groove, strong reflected light returns. Also, the tracking error signal has a sum output of zero at the center line on the track (zero cross), and when the pickup is displaced bidirectionally from the track, a voltage as shown in the figure is generated due to the deviation angle of the sub beam.

On the other hand, in the W / O disk, since the pits on the track are formed in an amorphous state, the amount of reflected light increases on the pits, and on the groove it is in a crystalline state. Therefore, the amount of reflected light is diffracted by the laser beam. Is reduced.

When the LD has the same optical system and electric circuit polarity as the LD, the signal polarity of the tracking error signal is inverted as shown in the figure. That is, when the LD outputs a tracking-on command and closes the tracking servo loop, tracking control is performed at the rising timing of the tracking error signal (for example, point A), and the pickup follows the track. When the same device is used for the W / O disk with the same device, the timing of the rising edge of the tracking error signal (for example, A ′
Tracking control is performed at the point), and the pickup follows the groove where no signal is recorded.
That is, in the case of a W / O disk, tracking control cannot be performed on the track unless the polarity of the tracking error signal is inverted.

It is the n-fold inverting amplifier 21 of FIG. 1 that enables tracking control on a track even in a W / O disk. Further, since the LD and the W / O disk have different reflected light amount levels, in order to perform various servos in the same circuit, one of the signals should have an appropriate magnification (for example, n.
It is necessary to adjust it to an appropriate signal level by amplifying it by a factor of 2). This is performed by the n-fold amplifiers 12, 17, and 21 shown in FIG.

Next, the operation will be described based on the flowchart shown in FIG. First, the optical disc to be discriminated is started from a state where it is loaded in the present optical disc recording / reproducing apparatus.

As an initial condition, focus open,
That is, the CPU 29 is in the focus open state without issuing the focus on command and the focus servo is not performed, the spindle command off, the FG servo on command off, the tracking servo open, that is, the CPU 2
9 does not issue a tracking-on command, is in the tracking open state and tracking servo is not performed, and the pickup position is the innermost circumference of the optical disc, L
It is assumed that the D / W / O disk switching command is on the LD side.

In step 01, the CPU 29 supplies a scan command to the slider servo circuit 24, and the slider servo circuit 24 moves the pickup to an appropriate position on the outer peripheral side of the optical disk. This is, for example, L in this embodiment.
In the case of D and W / O discs, the radius is about 65 mm from the center of the optical disc. That is, with respect to a plurality of types of optical disks to be recorded / reproduced in the optical disk recording / reproducing apparatus, both of them surely select the corresponding position in the signal recording area. Next, the focus-on command closes the servo loop of the focus servo circuit 18 (S02). When the loop is closed, the pickup is driven toward the focal point based on the astigmatism method. When the loop converges, the focus servo circuit 18 generates a focus lock signal. Therefore, the CPU 29 monitors the focus lock signal (S03).

When this signal is not present (NO), it can be determined that the optical disc is not loaded, and the optical disc recording / reproducing apparatus enters the park mode (S0).
4).

On the other hand, the focus lock signal is sent to the CPU 29.
If YES can be confirmed (YES), the CPU 29 supplies a spindle-on command to the time base servo circuit 26 (S05), the spindle motor 27 is driven, and the rotation speed of the optical disk rises. Here, the rotation speed is, for example, 13
Increase to about 00 rpm. Then FG (Frequency Ge
nerator) Servo-on command is supplied from the CPU 29 to the time base servo circuit 26 (S06), and the spindle motor 27 is speed-controlled to the target rotation speed. For example, the number of rotations of the motor increases to about 1500 rpm.

FIG. 4 shows an output waveform of the RF signal (point C) which is photoelectrically converted in the light receiving portion 8 and is amplified by the differential amplifier 11 in the state where tracking servo is not performed at this time. (A) is an RF signal waveform when the optical disc to be discriminated is an LD, and (b) is an RF signal waveform when it is a W / O disc.

As shown in the figure, when the CPU does not output the tracking-on command and the tracking servo is not performed, the pickup does not follow the track position, so that the laser beam is eccentric to the disc recording surface. Ride on or off the existing trucks. Therefore, regardless of whether the optical disc to be discriminated is an LD or a W / O disc, the amplitude of the RF signal due to the reflected light that is input varies periodically.
The reason why the maximum value of the amplitude is different between the case of the LD and the case of the W / O disk is that the magnitude of the reflectance is different depending on the type of the optical disk to be discriminated. In this case, the tracking error signal also becomes a signal that changes in the same cycle as the envelope waveform of the RF signal (broken line in FIG. 4) for the same reason as above.

At this time, the tracking servo circuit 22
Since a tracking zero-cross signal is input to the CPU 29 from the tracking zero-cross detector existing therein in synchronism with the rotational speed of the disk, the CPU 29 checks whether or not the pulses of this tracking zero-cross signal can be counted ( S08).

The number of revolutions set in S08 (for example, 1500
(rpm) cannot be detected by the CPU 29 (N
O), it is considered that the pickup is located on the mirror surface where no track exists in the target optical disc. That is, it is considered that the pickup has moved too far to the outer peripheral side and is located outside the recording surface, so the CPU 29 sends a scan command to the slider servo circuit 24, drives the slider motor 25, and moves the pickup to the inner peripheral side ( S09).

When the CPU 29 can detect the count number of the tracking zero-cross signal as set in S08 (Y
ES), the pickup is located on the signal recording surface,
Can be judged. Next, the CPU 29 supplies a tracking-on command to the tracking servo circuit 22 to determine the type of optical disc (S10). Then CPU 29
Discriminates the disc to be discriminated by checking the RF sense signal (S11).

In the initial state, the polarity of LD is set to SW1, S
Since the switches of W2 and SW3 are switched, when the optical disc to be discriminated is an LD, the tracking error signal of the LD in FIG. 3 rises (A in FIG. 2).
Tracking servo works at the position. As for the RF signal output waveform (point C), since the servo is applied on the track, the RF signal is output as shown in FIG. Further, when this RF signal output is detected by the envelope detector 13 and the AC component is attenuated by the low pass filter 14 (point E),
The output waveform of the LD shown in FIG. If the threshold value Vth1 of the comparator 15 is set, for example, as shown in FIG. 6A, the RF sense signal becomes high level, and it can be determined that the optical disc to be discriminated is LD.

On the other hand, when the optical disc to be discriminated is a W / O disc, if each switch is switched to the LD polarity, the rising of the tracking error signal of the W / O disc in FIG. 3 (A 'in FIG. 2). The tracking servo operates at (position), the RF signal output waveform is servoed on the groove, and the RF signal is not generated as in (b) in FIG. If you pass the envelope detector in this state,
The detection output is hardly output, and W / in FIG.
It becomes the output waveform of the O disk. This is the threshold Vth
It is 1 or less, the RF sense signal becomes low level, and the optical disc to be discriminated is discriminated as a W / O disc. When the RF sense signal is at a high level (YES) In this case, as described above, it can be determined that the disc to be discriminated is the LD. Therefore, the CPU 29 moves to S12.
Outputs a spindle-on command to rotate the disk, and S
13 data checks are performed. This is the address data of the disc, and based on this, the initial search mode or the like is entered as the next step (S14). When the RF sense signal is at a low level (NO), in this case, it can be determined that the optical disc to be discriminated is a disc other than the LD including the W / O disc. Next, the CPU 29 sets the LD / W / O disk switch to W
Switch to the / O side (S15). The SW1 activates the n-fold amplifier 12 to output an n-fold multiplied RF signal to the video signal control system. Further, the SW2 activates the n-fold amplifier 17, and the focus servo circuit 18 is supplied with the n-fold focus error signal. SW3 is n
Select the double inverting amplifier 21 and select the tracking servo circuit 22.
Then, a tracking error signal whose polarity is inverted by n times is supplied. The reason why the input to each circuit is multiplied by n is that there is a difference in the amount of reflected light depending on the optical disc to be discriminated, as can be seen from the comparison of the RF signal outputs in FIG.
This is because the RF signal level also varies in proportion to it. On the other hand, since an appropriate input level is determined for each servo circuit, signal amplification is necessary to adjust the input level of the RF signal in both types of optical disks. The magnification n is the ratio of the RF signal level of the optical disc to be discriminated. The reason why the signal is inverted in addition to being multiplied by n in SW3 is as follows.

In the tracking error signal (e) in the W / O disk of FIG. 2, if the tracking servo works with this signal as it is, the servo works at point A'as described above, and R
F signal cannot be obtained. However, when the tracking error signal is inverted, the tracking servo circuit 2 similarly
2 applies servo at the rising edge of the input signal. But,
This point corresponds to the fall of the signal before inversion (point B),
It is located on the track of the W / O disk. That is, W /
Servo can be applied on tracks even with O discs. Then, in step S16, the RF sense signal is sent again to the CPU
9 examines.

If the optical disc to be discriminated is a W / O disc, the tracking servo works on the track and R
Since the F signal is detected, the envelope detection output also becomes large as shown in FIG. 6 (b). Since this output is at a level higher than the threshold value Vth1 as shown in the figure, the RF sense signal becomes high level, and the disc to be discriminated is W / O.
It can be confirmed that it is a disc (YES). When the disc determination is completed, the spindle is turned on (S12), the data is checked (S13), and the next step (S14) is entered, as in the case of the LD.

When the disc to be discriminated is neither an LD nor a W / O disc, it is considered that an appropriate RF signal is not output. In this case, the RF sense signal becomes low level,
It is determined that the disc is not a recording / reproducing target of the device, and the park mode (S17) is entered. (II) Second Embodiment A second embodiment of the optical disc discriminating apparatus of the present invention will be described with reference to FIG. In the first embodiment, the tracking zero cross count used for the counting operation of S07 in the flowchart of FIG.
Although it was obtained from the zero cross detector of
From the envelope detector 13 used to generate the sense signal,
The tracking zero-cross signal is directly obtained.

(A) is an excerpt of the RF sense signal generating portion of FIG. The RF signal at point C in the figure is in the tracking open state and is indicated by the RF signal in (b). This RF is output to the detector 13 (point D in FIG. 1).
The envelope waveform of the signal is being output. This is drawn out before the low-pass filter 14, supplied to the comparator 30, and compared with an appropriate threshold value such as Vth2 in (c). The output of the comparator 30 is the same as the tracking zero cross signal extracted from the zero cross detector in the tracking servo circuit 22 described above. If this is supplied to the CPU 29, the present invention can be implemented with the flow chart of FIG.

The second embodiment is effective when it is difficult to extract the tracking zero-cross signal from the tracking servo circuit. The present invention is not limited to the above embodiment, and various modifications can be made. For example, in each of the above-mentioned embodiments, the LD and W / O disk discriminating apparatus is used.
By appropriately selecting the magnification n of the amplifier in the embodiment, the target disk can be discriminated. Further, in each of the above-described embodiments, an example in which the three-beam method is used as a tracking method has been shown, but the present invention is not limited to this method, and a tracking servo method using a combination of other methods such as a push-pull method is also applicable. The present invention can be applied. The focus servo method can be applied to the present invention by combining other methods without depending on the astigmatism method.

[0047]

As described above, according to the present invention, discs are discriminated by utilizing the fact that the relationship between the magnitudes of the reflectances on the tracks and the grooves is different depending on the types of discs. , Discrimination of an optical disc using an optical disc discriminating device using the difference in reflectance or modulation degree seen in the conventional example can be performed without being affected by variations in optical discs and between devices, particularly discriminating of discs whose reflectances are not so different from each other. It is suitable as a device capable of performing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an RF signal strength and a tracking error signal in an LD and a W / O disk.

FIG. 3 is a flow chart diagram illustrating an operation according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an RF signal waveform in a tracking open state.

FIG. 5 is a waveform diagram showing an RF signal when tracking is closed with the LD polarity.

FIG. 6 is a waveform diagram showing the output of a low-pass filter when tracking is closed with the LD polarity.

FIG. 7 is a block diagram and a waveform diagram in the second embodiment of the present invention.

FIG. 8 is a circuit diagram of an optical disc discriminating apparatus in a conventional example and an optical disc discrimination explanatory diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser 2 ... Optical modulator 3 ... Lens 4 ... Beam splitter 5 ... Tracking mirror 6 ... Objective lens 7 ... Optical disk 8 ... Light receiving part 9, 10 ... Photoelectric conversion element 11, 16, 20, 102 ... Differential amplifier 12 , 17 ... N-fold amplifier 13 ... Envelope detector 14 ... Low-pass filter 15, 30, 103, 104 ... Comparator 18 ... Focus servo circuit 19 ... Focus coil 22 ... Tracking servo circuit 23 ... Actuator 24 ... Slider servo circuit 25 ... Slider Motor 26 ... Time base servo circuit 27 ... Spindle motor 28 ... Tacho generator 29 ... CPU C1-C3 ... Capacitor R1-R7 ... Resistor VR1 ... Variable resistor SW1-SW3 ... Switching device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Takizawa 4-2610 Hanazono, Tokorozawa-shi, Saitama Pioneer Co., Ltd. Tokorozawa factory

Claims (1)

[Claims] 1. An optical disc discriminating apparatus for discriminating a plurality of optical discs having different magnitude relationships between the light reflectance of a signal portion and the light reflectance of a non-signal portion, wherein A read signal detection means for detecting the presence / absence, a tracking error generation means for generating a tracking error signal according to the displacement amount from the signaled portion or the non-signaled portion, and a signal polarity reversal function of the tracking error signal in the input stage are provided. Then, when the tracking servo loop is closed, the tracking servo means capable of performing tracking servo on the signal part of an arbitrary optical disk regardless of the magnitude relation of the reflectance, and the output result of the read signal detection means are discriminated and read. When there is no signal, the polarity of the input stage of the tracking servo means is controlled to be inverted. Optical disc discriminating apparatus comprising: the determination control means.