JPS5987666A - Servo control circuit of information reproducer - Google Patents

Abstract

PURPOSE:To avoid a track skip or an out-of-focus state although an error signal contains noise due to a defect of a medium by limiting the amplitude of the high frequency component of an error detection signal when an output is given from a defect detecting part and having no limitation when no output is delivered from the defect detecting part respectively. CONSTITUTION:A signal S5 is set at a low level in a reading period tL of the defective part of a disk, and a switch 41 is turned on. Then the amplitude is limited for an error detection signal VA of a reproduction signal generating part 40 by a limiter consisting of a resistance 33a to a high frequency component, a diode train 33b and a voltage follower 33c. Then an error detection signal VB is supplied to a servo amplifier 34 with the noise N suppressed satisfactorily. The switch 41 is turned off in a reading period tN containing no defect, and the signal VA is supplied as it is to the amplifier 34 via a resistance 33a. Therefore a control is carried out with proper correspondence to a change of the tracking error detection signal which is produced by vibrations in case the external vibrations are applied to an information reproducer. An envelope detecting part 42 is provided.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is directed to an information reproducing device that reproduces information recorded from a recording medium such as a video disc or a digital audio disc. The present invention relates to a servo control circuit that performs control to properly maintain a tracking state and a focus state in the case of an optical device.

Background Art and Problems Information reproduction uses a disk-shaped recording medium provided with an information recording track formed by an arrangement of pits corresponding to information such as a video signal or an audio signal, and reproduces information from the recording medium. In the device, an information reproducing system scans an information recording track on a recording medium with a light beam such as a laser beam, and reproduces recorded information by detecting changes in the C beam. It is also known as a disk system, digital audio disk system, etc. In the information reproducing apparatus of such a system, when scanning the information recording track on the recording medium with a light beam, the original beam must always reach the information recording track accurately, and the information recording track must be Automatic control is required to focus the light in an appropriate manner. The intransitive beam 1 is designed to make these light beams reach the information recording track correctly, and the automatic control device 1 is used to properly focus the light beams onto the information recording track, respectively, for tracking control and focusing. This is called control, and this optical information reproducing device VC
tI″f, it has become something that is not available in town.

These controls are normally carried out when the C beam is made incident on the recording medium via the C4 optical head, modulated by the recording medium, and guided back to the photosensitive element via the above-mentioned optical head. From the obtained output 7J signal, tracking error and focus error detection signals are obtained according to the arrival status and focusing status of the light beam to the information recording track, and based on these detection signals, an optical system forming the optical head is used. (This is achieved by providing respective servo control circuits that drive and control the position of lenses, mirrors, etc.) Such a servo control circuit in an optical information reproducing device is provided. An example of the optical system is shown in Figure 1 of the drawings. In the figure, / is a disk which is a recording medium, and an information recording track is formed by an array of pits. In the laser light source, the laser light from this laser light source enters the left polarizing beam splitter via the diffraction grating plate 3 and the collimator lens <zi.The laser light that has passed through the polarizing beam splitter 5f passes through the wavelength plate B The object lens 7 enters an objective lens 7 constituting an optical head, is focused by this objective lens 7, and is made incident on the disk l.The objective lens 7 is moved, for example, in the direction across the information recording track and the recording medium by driving means g and wo. The laser beam incident on the disk is modulated and reflected by the optical recording track, enters the objective lens 7 again, and passes through the wavelength plate. It passes through Hiroshi O and enters the polarizing beam splitter S. The reflected laser beam refracted to the right in the figure by the polarizing beam splitter S reaches the photosensitive portion // via the lens system /θ. The photodetector comprising the photosensitive section detects the reflected laser light modulated by the recording medium from the objective lens 7 of the optical head, that is, the reading light, and the change is extracted as a signal. . The cutting edge signal from the photosensitive section // is supplied to the signal processing section/2 including servo control circuits for tracking control and focus control, and each of the servo control circuits in the signal processing section/2 For tracking control (1) and focus control, a drive No. 18 is formed to drive and position control the objective lens 7 constituting the optical head, and is supplied to drive means g and 9 for both tracking control and focus control. . In addition, from the No. 18 processing unit/2, the playback information No. 18
In the above-mentioned optical system, the laser beam from the laser light source is divided into three laser beams when it passes through the diffraction grating plate 3, and in FIG. Therefore, it is shown with seven lines, but after the -1 fold grating plate 3, the polarizing beam splitter,
In the i path, it passes through tk, is reflected by the disk /, is refracted by the polarizing beam splitter '3, and reaches the photosensitive section //.
There are actually three V-saput beams. 3 These three laser beams are, as shown in Figure Ω, a main beam /3 which is to track the information recording track T and reproduce the information recorded on the disc /;
This main beam/? λ auxiliary beams/9 for detecting tracking deviation with respect to the information recording track T
F and /lIF and are made incident. in this case,
Two auxiliary beams /lIE and /4'F are connected to the main beam /
3 as the center, the positions are symmetrical with respect to the direction along the information recording track T and the direction perpendicular thereto. The main beam /3 and the auxiliary beams /lIE and /gF reflected by the disk / are transmitted to the photosensitive area through a cylindrical lens for detecting the focus state, which constitutes the entire common lens system 10. // to separate photodetectors at. For this reason, the photosensitive area/
/ are adjacent to each other or photodetectors /i, /1 ., as shown in FIG. /&C and 15D, and two photodetectors /OtsuE and /OtsuF separated from these, and the main beam /3 is placed on nine photodetectors 15A to 15D.
A spot is created by the photodetector /E and /
Spots are created on F by the auxiliary beams /4'E and /llF, respectively. ) From the photodetectors /, 1 to /iD, eclipses 7] I A, l B, , ■ c and ID are obtained, respectively, according to the spot portion of the main beam /3 for each, and 5 is obtained. Outputs IE and IF corresponding to the j method of the spots of the auxiliary beams /llE and /gF are output from the detectors /E and /F, respectively.

Conventionally, the word processing unit/2 is configured as shown in FIG.
In addition to the servo control circuit for servo control and the servo control circuit for focus control, it also includes a circuit for obtaining one word of endogenous information1.The servo control circuit for tracking control is
Output signals IE and Ipff of photodetectors /OtsuE and /OtsuF
: is supplied to the subtracter /7 to obtain a detection signal of the tracking deviation, that is, tracking error, expressed as IE - IF, and this detection signal is supplied to the servo amplifier /g to output the servo The configuration is such that a driving current I is supplied to the tracking control driving means g from the output terminal of the amplifier /g.

The driving means g moves the objective lens 7 to the information recording track 'al
This is a movable coil that moves in the yellowing direction. The objective lens 7 is driven according to the current flowing through it, and the main beam/
3 and the auxiliary beams tttE and /lIF are moved in a direction perpendicular to the direction along the information recording track T. In this case, the main beam /3 and the auxiliary beams /llE and /gF
Since the mutual positional relationship with the main beam is fixed, the main beam /3
and the auxiliary beams /lIE and /4'F are moved simultaneously and in the same direction1, and the detection signal of the tracking error, denoted by IE -IF, is the main beam /3'
The polarity and level of the signal change depending on the deviation of the tracking toward the center and the outer periphery of the disk with respect to the information recording track T of the disk. The objective lens 7 is moved to perform tracking control.

The servo control circuit for focus control supplies the output signals IA and IB of the photodetectors /i and 15B to an adder /9 to obtain a sum signal IA+IB of the two, and also supplies the output signals IA and IB of the photodetectors /i and 15B to an adder /9 to obtain a sum signal IA+IB of the two. jD output signals IC and IDk
is supplied to the adder 20 to obtain a sum signal Ic+Io',
And both sum signals IA+IB and Ic+-ID
is supplied to the subtractor 2/, (IA+IB) (IC
+ID'), a detection signal of the shift of the focus state from the just focus state, that is, a focus error, is obtained, and this detection signal is sent to a servo amplifier, 2.
2. The drive current for the focus control drive means is supplied from the output ends of the servo amplifiers 2, 2 to the drive means for focus control. The driving means 9 is a movable coil for moving the objective lens 7 disposed facing the disk in a direction perpendicular to the disk. 7's distance to disk/ can be changed. Although not shown, the optical detectors /i to /jD by the main beam /3 are controlled by the lindrical lens constituting the lens system /θ depending on the state of focus of the main beam /3 on the surface of the disk /.
The shape of the upper spot changes and becomes (IA+IB)-(IC
+ID) The polarity and level of the focus error detection signal are changed. ``Then, the objective lens 7 becomes a constant distance from the disk /, and the spots on the photodetectors 15A to 15D caused by the main beam /3 become circular as a whole, and are expressed as (I A + InL (Ic + In) The focus error detection signal is set to zero, and focus control is thereby performed.

In addition, an adder! The above sum signal I A from 9 and Ω0
+ I B, I and c + I n are supplied to an adder 23, and a reproduced information signal expressed as I A + I B + I c + I o is extracted.

In an information reproducing device having an optical system equipped with a servo control circuit for tracking control and focus control as described above, for example, tracking errors occur due to disk eccentricity, external vibration, etc. Detection No. 18 VA, as shown in Fig. The gain characteristics of the servo control system are widened as shown in FIG. In order to make the gain of the system like this, the servo amplifier 1g mouth body σ
)'F+ characteristics are set such that the loop σ) amplifies a frequency even higher than the cutoff frequency fc.

By the way, when vapor deposition is performed on the surface of a disk or recording pits,
7 /L, If there is a defect such as a pinhole or scratch on the minium, the defect is caused by the auxiliary beam /lIE or /
' Optically read by IF, cr > 1
- appears in the racking error detection signal VA as a relatively large amplitude noise N; And this σ) noise N
is amplified by a servo amplifier/g and provided as a driving signal gVC to the driving means. However, as shown in Fig.
For example, in the case of a digital audio disc, several k
It becomes about H2. Therefore, due to this noise N,
So-called track skipping occurs. However, subtraction R? Tracking error detection 1-1 by inserting a rotary filter between r/7 and servo amplifier/g
It is also conceivable to remove the noise N' from the word VA.

However, if this is done, the gain characteristics of the servo control system will be expanded so that it will respond to relatively frequency σ)1 angular components in one tracking error detection word VA, as described above. It becomes impossible to set the cutoff frequency fc to the desired value.

In addition, the focus control also suffers from a four-ball phenomenon, i.e., if there is a defect on the disk surface or recording pit, noise will occur in the focus error detection signal obtained from the subtractor 2. However, the objective lens is moved beyond its control range and is completely out of focus.

Therefore, in order to solve this problem, the present applicant first proposed a servo control circuit for an information reproducing apparatus as shown in FIG.

The servo control circuit shown in FIG. 7, for example,
This is a servo control circuit in an information reproducing apparatus having the optical system shown in the figure. Here, the photosensitive section 30 is connected to the photodetectors 15A to 15D shown in FIG.
This is provided for Otsu E and /Otsu F', and this photosensitive part 3θ
The output of the error detection signal generator 3/ is supplied to the error detection signal generator 3/. The error detection signal generating section 3/ corresponds to the subtracter/7 in the circuit shown in FIG. receive,
A tracking error detection signal or a focus error detection signal is obtained at the output end. The output end of the error detection signal generator 3/ is connected to the input end of the servo amplifier 341 via the low-pass filter 32 and limiters 3 and 7, and the output ends of the three servo amplifiers are used for tracking control or focus control driving. It can be connected to the means 3S. The limiter 33 in this example includes a resistor 33a,
Each of the diode rows 3.3b includes seven or several diodes connected in parallel in opposite directions, and a voltage follower 33c.

The operation of the servo control circuit shown in FIG. 7 will be explained using the case of tracking control as an example. For example, the tracking error detection signal shown in FIG. When vA is obtained, an output voltage Vc as shown in FIG. This allows detection of tracking errors including the above-mentioned noise N.
, in the IJ transmitter 33, the low frequency component of the signal VA is added to and subtracted from the output voltage VC of the all-low pass filter 32 by the voltage drop Vbe across the diode array 33b, resulting in a voltage VC+vL (!) as shown in FIG. : Voltage V c −V
The amplitude is limited within the range of L. Therefore, only the above-mentioned noise N is suppressed as shown as noise N' in FIG. The signal is applied to the drive means 3S via the signal.

The same applies to the case of focus control in which a focus error detection signal is obtained at the output terminal of the error detection signal generator 3/, and the noise contained in the focus error detection signal is suppressed by the limiter 33 and the servo amplifier 3' lt:
It is supplied to the driving means 3S through the motor.

As mentioned above, depending on the servo control circuit described above,
Since noise caused by reading defects on the disk is sufficiently suppressed, track skipping and out-of-focus caused by noise are reduced.

However, in the servo control circuit shown in FIG. 7, the surface frequency component of the tracking error or focus error detection signal is always limited in amplitude.
When such a circuit is used, for example, there is a risk that the vibration resistance of tracking control or focus control will not be sufficient when vibrations due to external force are applied to the information reproducing device.

For example, when vibrations are applied to the information reproducing device due to an external force, the vibrations cause a change in the relative position between the disk and the optical system, especially the objective lens, and this causes the tracking obtained from the error detection signal generator 3/ to change. A relatively high-frequency human-width portion occurs in the error or focus error detection signal, but the amplitude of this portion is also limited by the limiter 33. Therefore, tracking control or focus control that appropriately responds to changes in the tracking error or focus error detection signal caused by vibrations is no longer performed, and as a result, when vibrations due to external force are applied to the information reproducing device, relatively This will easily cause track skipping and loss of focus.
That is, there is a possibility that the tracking control or the vibration resistance of the focus open side 1 will be deteriorated.

OBJECT OF THE INVENTION In view of the above, the present invention provides a tracking error detection system. 7 ≧ Even if the recording medium contains noise caused by reading defects such as disks, tracking control and focus control that can prevent track skipping and defocusing are performed, and the information is It is an object of the present invention to provide a servo control circuit for an information reproducing device that enables tracking control and focus control with excellent movement when vibrations are applied to the reproducing device due to an external force. .

Summary of the Invention A servo control circuit for an information reproducing device according to the present invention detects an error to detect a tracking error or a focus error when information is read from a recording medium such as a disk mounted on the information reproducing device. a signal generating section; a supplying section that supplies a detection signal from the error detection signal generating section to a tracking or focus control driving section; and a defect detection section that detects and produces a detection output, and when the detection output from the defect detection section is obtained, the supply section converts the relatively high frequency components of the detection signal from the error detection signal generation section to a predetermined limit level. When no detection output is obtained from the defect detection section, the supply section is configured not to apply amplitude limitation to the detection signal from the error detection signal generation section. With this configuration, when the tracking error or focus error detection signal contains noise caused by reading a defective portion of the recording medium, this noise is suppressed and track skipping is prevented. In addition, when vibrations due to external force are applied to the information reproducing apparatus, tracking control or focus control with excellent vibration resistance is performed.

Example Examples of the present invention will be described below.

FIG. g shows an example of a servo control circuit for an information reproducing apparatus according to the present invention, and this example is applied to an information reproducing apparatus having an optical system as shown in FIG. The photosensitive section 30 is similar to that in the servo control circuit shown in FIG. 7, and the photodetector/detector shown in FIG.
3A to 15D, /E and /F', and the output of this photosensitive section 30 is supplied to the reproduction first word generation section GO.

The reproduced signal generator group θ corresponds to, for example, the combination of subtracter/7 or adder/7 and 20 and subtracter 2/ in the circuit shown in FIG. It corresponds to a combination of an error detection signal generation section that receives the output and generates a tracking error or focus error detection signal, and an adder/9.20 and 23, and the photosensitive section 3
and an information signal generating section that receives an output of 0 and generates 1 word of reproduction information.

One output terminal of the reproduced one word generator θ which sends out a tracking error or focus error detection signal is connected to a resistor 33akfrL and a servo amplifier 3'l.
The output end of the servo amplifier 3'l is connected to a tracking control or focus control driving means 3S. And between both ends of the resistor 33a,
A low pass filter 3 similar to that in the servo control circuit of FIG.

Voltage follower 33c and diode string 3.3b are connected in series via switch tI/.

On the other hand, the other output end of the reproduction signal generating section G0, which sends out the reproduction information signal, is connected to the envelope detection section II2. The output terminal of the envelope detection section t1.2 is connected to the comparison input terminal of the level comparison section G3, and the reference input terminal of the level comparison section G3 is connected to q reference voltage sources. The output terminal of this level comparison section G3 is connected to the comparison input terminal of the level comparison section GUA through the diode tl left and the capacitor B forming an integrating circuit, and is connected to the reference input terminal of the level comparison section 1L-7. is connected to the reference voltage source g. The output terminal of the level comparator GUA is connected to the control terminal of the switch lI/.

Next, the operation of an example of the servo control circuit according to the present invention configured as described above will be described, taking as an example the case where it is used for tracking control.

If the disk has a defect such as a scratch, the defect on the disk is read from the output end of the raw signal generator/I0 as shown in Fig. sA. Detection of tracking errors including generated noise Nk 1
The word vA is obtained. 3 Also, from the other output terminal of the reproduction signal generating section t10 (-1:, as shown in FIG. The number S/ is obtained and supplied to the envelope detector q.1 In this case, since the defect on the disc usually spans multiple information recording tracks on the disc, the missing part d corresponds to the size of the defect. In other words, in Figure 9, tN indicates the period during which the non-defective portion of the disk is read, and tl indicates the period during which the defective portion of the disk is read. 1. From the envelope detector λ, an output signal 8.2 is obtained as shown in Figure B, which corresponds to the envelope of the endogenous information 1 word S/. This output signal 8.2 is a low level part a/-t corresponding to the missing part d of the reproduced information signal S/.
, shall have. Then, in the level comparison section lI3,
The output signal s2 is compared with a voltage at a reference level V7, which is close to zero, as shown in FIG. As shown in C, a low level tl is set corresponding to the low level part d' of the first word S.z that is lower than the reference level v7,
In other cases, a comparison output s3 having a high level hi is obtained. Note that the reference level V7 is higher than the level at the missing part d of the signal S/ obtained when a defective part of the disc is read, and is higher than the level of the signal S obtained at the missing part d when a non-defective part of the disc is read. For example, when vibration is applied to the information reproducing device during normal operation, the level of the signal Sl decreases, but the level is selected to be lower than the low level of the signal S/ that occurs in such a case. .

This comparison output SJ is integrated by the diode q left and the continuum sag B, and the signal voltage Sp as shown in Figure 9 is obtained at the capacitor O. Disk / +
[: During the period t when + changes to a low level t2 every time it turns, the level of the signal voltage Sda is set so as not to return to the high level H taken during the period tN. 1, the signal voltage S4= is the level comparator lI7, and the reference voltage source t1. The signal voltage Sda is compared with the voltage at a reference level v,2, which is slightly lower than the high level H taken during the period tN, as shown in the ninth diagram, where g is generated, and from the level comparison section q7, , period tN as shown in FIG. 9E.
The signal S5 takes a high level h'l at 1L and takes a low level t2 immediately after entering the period 1L and at the end of the period 1 at a low level t2. In this way, the period tL during which the defective part of the disc is read is equal to the low level t-tz of the signal Ss.
Therefore, the circuit from the envelope detecting section '12 to the level comparing section Gua forms a defect detecting section.

The signal S3 from the level comparator q7 is supplied to the control end of the switch tl/, and the switch tI/ is turned on at the low level t of the signal S5 and turned off at the high level h=1. When switching/ is turned on,
The resistor 33a, the diode array 33b, and the voltage follower 33o form a limiter similar to the limiter 33 in the servo controller circuit shown in FIG. ″
Further, when the switching/is turned off, the above-mentioned limiter is not turned off.

In this way, during the period tL during which the defective portion of the disc is read, the signals S and t take the low level Zi, so the switch tl/ is turned on and the reproduced signal generator 11O
Regarding one tracking error detection signal vA, as shown in FIG. SA, which is obtained at one output terminal of As shown in FIG. A detected tracking error signal vB is supplied. Therefore, in this case, the adverse effect of the noise N included in the tracking bone error detection signal vA in tracking control is significantly reduced, and track skipping etc. are prevented. In addition, during the period tNK during which the defect-free portion of the disk is read, the signal Ss takes a high level h'l, so the switcher/Irf turns off, and the tracking obtained at one output terminal of the reproduction signal generator G0.・Error detection 1 word vA increases the servo through resistor 33a*! 1 prefecture 3
Hot water is supplied to the area. Therefore, if vibration is applied to the information reproducing device due to an external force in the J41i state, the tracking control will not be performed in accordance with the change in the tracking error detection signal caused by this vibration. Tracking control with excellent 1llI-1 vibration properties is performed, which does not cause noise such as track skipping due to vibrations caused by the moon C.

Note that the example shown in FIG. 3 is used for the focus open side 1, and the focus is
The case where an error detection signal is obtained is the same as above, and during the period when the defective part of the disk is read, the resistor 3 is
3a, diode array 33b and voltage follower 33
A limiter is formed by C, and the focus/error detection signal is supplied to the servo amplifier 3 with the noise generated by reading the disc defect contained therein sufficiently suppressed. During the period when the defect-free portion is read, the reproduction signal generation MlgO
The focus error detection signal from the resistor 33af
The signal can be directly supplied to the single servo amplifier Jl via the servo amplifier Jl. As a result, focus control is performed to prevent out-of-focus effects even when a defect on the disc is read or when external imaging is applied to the information reproducing device.

FIG. 70 shows the main part of another example of the servo control circuit of the information reproducing apparatus according to the present invention. In this example, instead of providing a switching circuit in the example of FIG. 3, a voltage follower 33o and a tie-auto row 33b are connected face-to-face, and a limiter 33 as shown in the circuit of FIG. 7 is installed. A resistor 99'ff is connected in parallel to the signal path P/ formed by the low-pass filter 3.2 and the limiter 33.
: Containing signal path P2f: Provided so that each of both signal paths can be selected by switches SO and S/, and the side legs are set by the signal St from these switches SO and left/wo level comparison section 97. One with a corresponding configuration, in this case the switch SO and the left /IrJ, selects the signal path Plffi when the signal Ss takes a low level t2, and the signal S
When 5 takes a high level, signal path 82 is selected. Accordingly, during periods when the defective portion of the disc is idle, the switch s is activated.

The f word path P/ is selected by and 3/, and a tracking error or focus error detection signal from the corner generation part G0 is generated by reading a defect in the disk included in the tracking error or focus error detection signal. Noise limiter 3
3 is suppressed as a focus error detection signal vB and supplied to the servo amplifier 3.
The signal path P is selected by and /, and the tracking error or focus error detection signal from the reproduction signal generator G0 is transmitted to the resistor llq'! The signal is supplied directly to the servo amplifier 3 via r. Therefore, in this example as well, tracking control i1 or focus control similar to the example of FIG. 3 is performed.

Application Examples The servo control circuit for an information reproducing device according to the present invention can be used not only as a servo control circuit in an optical information reproducing device as described above, but also in a so-called grooveless capacitive disk reproducing device. It can also be used as a tracking servo circuit. In the case of a grooveless capacitive disk playback device, a tracking error in a playback head placed opposite a recording track formed on the disk is detected, and the playback head is driven based on the detection signal. Tracking control is performed, and a servo control circuit unit that supplies a drive signal to a drive means for tracking control for a playback head for all sets of tracking error detection signals is constituted by the servo control circuit of the information playback device according to the present invention. be able to.

Effects of the Invention As is clear from the above explanation, according to the servo control circuit of the information reproducing apparatus according to the present invention, during the period when the defective portion of the recording medium is read, the defective part of the recording medium can be easily detected. This effectively suppresses large-field noise in the tracking error or focus error detection signal, which occurs when detecting tracking errors or focus errors. It is possible to perform tracking control or focus control that prevents out-of-focus occurrences, and also prevents tracking errors and half-focus errors during the period when normal parts of the recording medium without defects are read. Since no amplitude limit is applied to the detection signal, even if vibrations are applied to the information reproducing device, an appropriate signal that follows the change in the detection signal of tracking 1 error or focus meeting error at that time can be used. Tracking control and focus control can be performed. The selection of such a state is automatically and appropriately performed, and tracking control and focus control can always be performed with great precision and high stability.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing an example of an optical system in an optical information reproducing device, Figure 2 is a diagram useful in explaining the source beam in the optical system shown in Figure 1, and Figure 3. 1 is a schematic configuration diagram showing the configuration of an example of a photosensitive section used in the optical system shown in FIG. 1, and FIG. 7 is a connection diagram showing an example of a conventional signal processing section used in conjunction with the optical system shown in FIG. 1. , S and 4 are diagrams used to explain the operation of the example shown in FIG. 7, and FIG. 7 is an example of a servo control circuit of an information reproducing apparatus previously proposed by the applicant 3 is a connection diagram showing an example of the speed control circuit of the information reproducing apparatus according to the present invention, FIG. 7 is a diagram used to explain the operation of the example in FIG. 3, and FIG. FIG. 2 is a connection diagram showing main parts of another example of the servo control circuit of the information reproducing device according to the present invention. Voltage follower, 3g is servo amplifier, 3rd left is tracking control H or focus sub side 1 drive means,
llO is a reproduction signal generator, 'l/, 30 and left/ are switches, G, 2 are envelope detectors, ri3 and /1t7
is a level comparison section, <lj is a diode, and 1 is a capacitor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 7 Figure 8 Figure 1O

Claims (1)

[Claims] An error detection signal generation section that obtains a detection signal of a tracking error or a focus error when information is read from a recording medium installed in the information reproducing device, and a detection signal from the error detection 1 word generation section that generates a tracking or focusing error detection signal. The defect detection unit includes a supply unit that supplies a supply to the control drive unit, and a defect detection unit that detects a change in a reproduced information signal obtained when a defective portion of the recording medium is read and generates a detection output. When the detection output from the error detection signal generating section is obtained, the supplying section limits the amplitude of the relatively low frequency component of the detection signal from the error detection signal generating section at a predetermined limiting level. control circuit.