JPS59201233A - Focus control circuit of optical disk record reproducing device - Google Patents

Abstract

PURPOSE:To adjust a focus position so that the detection sensitivity of either tracking or RF signal is optimized preferentially by increasing the detection sensitivity of a tracking error signal according to the decrease in the amplitude level of the RF signal. CONSTITUTION:The output terminal of an RF signal generating circuit 19 is connected to the input terminal of an envelope detecting circuit 25. This detecting circuit 25 detects variation in the amplitude level of an input signal, i.e. envelope signal to generate and output a correcting voltage V4 corresponding to the envelope signal, and the output terminal of this envelope detecting circuit 25 is connected to the output terminal of a focus adjusting circuit 23 through a resistance R2. Thus, the detection sensitivity of the tracking error signal is increased and the focus position of a light beam is adjusted so that the detection sensitivity of either tracking or RF signal is optimized preferentially.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a CD (optical compact disc), for example.
The present invention relates to an optical disc record playback device suitable for a DAD (digital audio disc) system, and particularly relates to an improvement in a focus control circuit.

[Technical background of the invention]

Recently, in the field of audio equipment, PCM (Pulse Code Monolation) is being used to achieve as high fidelity reproduction as possible.
Digital recording and playback methods using technology are being adopted. Fortunately, this is called digital audio, and the audio characteristics do not depend on the characteristics of the recording medium and are much better than those using conventional analog recording and playback methods. This is because it is established in principle.

In this case, a system that uses a disk as a recording medium is called a DAD system, and optical, electrostatic, and mechanical recording and reproducing methods have been proposed. Even if this method is adopted, the playback device that embodies it is still required to be able to satisfy advanced control functions and performance that are not found in conventional devices. .

In other words, if we take the CD system as an example,
CLv is a disk made by coating a transparent resin disk with a diameter of 12 ml and a thickness of 1.2 pieces with a metal thin film that forms bits (irregularities with different reflectances) corresponding to digital (PCM) data. Approximately 500 to 20 depending on the (constant linear velocity) method
0 [rotation driven at variable rotation speed of r, p, ml,
The disc is reproduced in a linear tracking manner from the inner circumference to the outer circumference using an optical pickup containing a semiconductor laser and a photoelectric conversion element. However, a huge amount of information that can be played in stereo for about one hour is recorded in the program area (radius 25 to 58 cm), and index data etc. are stored in the lead-in area (radius 23 to 25 cm). This can be easily seen from the fact that it is included in .

By the way, in the above-mentioned CD type disc record playback device, not only is an RF signal for playback obtained based on the output signal of the above-mentioned pickup, but also a light beam is used to obtain a bit string on the surface of the disc to be played back. To accurately trace the pit row without deviation from the
Various control signals are also generated, such as a tracking error signal for a so-called dragging servo, and a focuser No. 1 for a so-called focus surfer, which ensures that the light beam is always focused on the disk surface.

That is, FIG. 1 shows such a conventional disc record reproducing apparatus of the CD type.

In FIG. 1, numeral 11 is a disk, on one side of which a row 7) is recorded. At the bottom of this disk 11 in the figure, a link assemblage 12 is provided.

This big aqua 77″l, ? is the objective lens control unit 13,
Beam sinter J4, laser emitter 15 and fu, t
17 as shown in the figure.
The disk 11 is made movable in the radial direction by a pick-up feeding mechanism. In this way, the objective lens control section 13 of the pickup 2 controls the objective lens 1.
7 and a first moving coil 18a for moving the objective lens 17 in the tracking direction (radial direction of the disk 1) in cooperation with a magnet (not shown); This is similar to the second moving coil 18b, which is used to move in the focus direction (direction perpendicular to the surface of the disk 11). The objective lens 17 receives the original beam emitted from the laser emitter 15 from the beam sinter 1.
4. Therefore, the light beam is focused by the objective lens 17 on the surface of the disk 11 as shown by the dotted line in the figure, and is reflected depending on the presence or absence of bits on the disk 11. This reflected light travels backward through the objective lens 17, is reflected at right angles by the beam sinter 14, and is received by the photodetector 16.

Here, the photodetector 16 includes four light-receiving regions PDa-, P, which are composed of, for example, photodiodes.
It is of a so-called four-division type with Dd. The four light receiving areas PDa of this photodetector 16 are
"-PDd is designed to output detection signals Pa-Pd having frequency characteristics corresponding to the presence or absence of focus, respectively, when the reflected light from the beam snoritter 14 is received. However, this detection The output level of the signal Pa=Pd changes in accordance with the light receiving area of each of the light receiving areas PDa to PDd.

The photodetector 170 has four light receiving areas P.
The respective detection signals Pa-Pd output from Da-PDd are both supplied to the RF signal generation circuit 19. This RF signal generation circuit I9 generates a signal from the detection signal Pa=Pd (Pa=Pd).
+Pb+Pc+Pd) which corresponds to the digitized data recorded on the disk 11) is generated and output. The signal is supplied to a reproduction system (not shown) via such an RF multiplied signal output terminal Op, and is subjected to known processing.

Further, the detection signal Pa=Pd is also supplied to the tracking error signal generation circuit 2θ.

This tracking error signal generation circuit 20 is composed of a phase comparator circuit, a low-pass filter, an amplification circuit, etc. (not shown), and is generated from the detection signal Pa"-Pd (Pa+
A signal Pc) - (Pb+Pd) is generated, and the signal is converted into a change in voltage level and output. In other words, this voltage signal is output as a tracking error signal T corresponding to a shift in the forward and reverse directions of the spot of the light beam with respect to the bit string of the disk 11 (tracking error). That is, as shown in FIG. 2, for example, this tracking error signal T has an O [■] level when the spot of the light beam is correctly positioned on the bit string P, and when the spot is located in the forward and reverse directions with respect to the focus string P. It has positive and negative polarity voltage levels depending on the deviation and its magnitude.

Then, such a tracking error signal T is supplied to the first moving coil 18a through a moving coil drive circuit 21 consisting of an amplifier circuit (not shown), etc., so that the spot is always correctly positioned on the bit string. The objective lens 17 is controlled to move in the tracking direction, and the tracking surf 1? will be applied. In addition, the tracking error signal T
is supplied to the bisoku-a-sozo transport motor through a not-shown feed-shimmotor drive circuit for the bi-soku-azozo 12, and controls the movement of the bisoku-azozo 12 in the radial direction so as to follow the #movement of the objective lens 17. The so-called Binokuasopsa? It is now offered to the public.

Further, the detection signal Pa=Pd is also supplied to the focus error signal generation circuit 22.

The focus error signal generation circuit 22 is composed of a phase comparator circuit, a low-speed filter, an amplification circuit, etc. (not shown), and detects the above (g from P'a to Pd to (Pa+
A signal Pb)-(Pc+Pd) is generated, and the signal (i) is converted into a change in voltage level.And,
The focus damping voltage E1 output from the focus unit circuit 23 connected to the other input terminal of the focus error number 1 raw kite circuit 22 is added to this blood pressure number 16. .

Here, the focus adjustment circuit 23 includes a constant voltage source v,
, v2, consisting of a variable resistor VR and a resistor R1,
A reference voltage v3 is output from the output end of the resistor R1. The level of this bias voltage v3 can be freely adjusted by moving the adjustment terminal of the variable resistor VR. Such a reference voltage (3) is the focus adjustment voltage El.
The value obtained by adding the focus adjustment voltage El to the voltage signal generated by the focus error signal generation circuit 22 determines whether the focus of the light beam is on the surface of the disk 11. It is set so that the level is O[V] when it is correctly aligned (in focus).

That is, the voltage signal to which the focus adjustment voltage El is added is output as a focus error signal F corresponding to a shift in the forward and reverse directions (focus error) of the focus of the light beam with respect to the focused point. That is, as shown in FIG. 3, for example, this focus error signal F has a 0 [v] level when the focus of the light beam is at the focused point Q, and when the focus is in the direction opposite to the focused point Q. It has positive and negative polarity voltage levels depending on the deviation and its magnitude.

By supplying the focus error signal F to the second moving coil 18b via a moving coil drive circuit 24 consisting of an amplifier circuit (not shown), etc., the focus of the light beam can always be correctly focused on the disk 211.
The objective lens 17 is placed in a position that matches the plane (drive control position).
is controlled to move in the focus direction, and the focus point here? will be applied.

In this way, the light beam always correctly traces the bit string on the surface of the disk 11 while being subjected to the tracking servo and focus servo, so that the disk record playback device can always retrieve good digitized data. It is now possible to

The playback operation for Disc 1 has been explained above, but in this Hinoki disk record playback device, the search cable, structure,
In other words, the pickup 12 is moved in the radial direction of the disk 1 so as to quickly select (search) an arbitrary data portion from among the digitized data recorded on the disk 11 based on a track skip operation command given from the outside. Track skipping control can be performed in such a way as to

That is, this search mechanism performs a pick-up operation based on, for example, the above-mentioned trunk jump operation command.

7''12 calculates the distance information between the bit string currently being reproduced and the target bit string, as well as movement direction information indicating whether to move the pink-up 12 towards the inner circumference or the outer circumference of the disc 1. Calculate.And,
A track skipping signal K and a search switching signal are generated based on the distance information and moving direction information, and the track jumping signal K and search switching signal are supplied to the moving coil drive circuit 21.

Here, the above-mentioned trunk skipping signal has a positive polarity when moving the big anno f12 toward the outer circumference of the disk J1 and the objective lens 17 towards the (g) side in FIG. , is a voltage signal that has a negative polarity when moving the objective lens 12 to the ←) side in FIG.

In addition, when the moving coil drive circuit 21 is supplied with the search switching signal, it cuts off the input of the tracking error signal T to turn off the tracking servo, and instead outputs the track skipping signal K. The signal is output to the first moving coil 18a. Therefore, the objective lens 17 is moved in the radial direction of the disk 11 in response to the trunk skipping signal K, and the feed motor of the pickup 12 is accordingly moved in the same direction as the objective lens 18. The pickup 12 is then moved in the direction of the desired focus row, and the spot is forced to jump over the trunk.

Here, when the big anno f12 is moved in the radial direction of the disk 11 as described above, the amplitude level of the RF signal decreases as the spot moves away from the bit string and increases as it approaches. , a continuous pull component is generated. In this case, the ripple component generated in the RF multiplied signal amplitude level is used to calculate the number of focus rows crossed by the spot by counting its cycle, and thus the movement distance information of the Shibinoku Anogu 12. It is.

Therefore, when the travel distance information calculated as described above matches the distance information, the search operation is completed, and at this time, generation of the track skip signal K and the search switching signal A is stopped. As a result, the moving coil drive circuit 21 again outputs the tracking signal T to the first moving coil 18a to perform tracking servo, and is returned to the reproducing state again. .

By the way, in an actual CD type disc record playback device, when the wavelength of the light beam and the shape of the bit on the surface of the disc 11 are constant, the tracking error, the voltage of the amplitude level of the signal T (the body in Figure 2) level) is maximum (
The focal position fKi where the RF multiplied signal amplitude level is maximum (the best detection sensitivity)
'.

are different. Therefore, the 7A-cass adjustment voltage E1 is set as follows.

That is, when the focus adjustment voltage E is changed to change the focal position on the surface of the disk 11, the amplitude level of the tracking error signal T and the RF multiplied signal amplitude level change as shown in FIG. 4, for example. do. That is, FIG. 4 shows the relationship between the focus adjustment voltage E1, the tracking error signal T, and the RF multiplied signal, and the curve shown by the solid line in the figure is the tracking error signal T.
The curve shown by the dotted line is the RF multiplied signal amplitude level characteristic.

As is clear from FIG. 4, the voltage value Va at which the amplitude level of the tracking error signal T is maximum is lower than the voltage value vb at which the RF multiplied signal amplitude level is maximum. Therefore, in the conventional disc record playback device, the tracking error signal T and RF
In order to simultaneously extract double signals in good condition, the focus adjustment voltage El is set to a voltage value Vc corresponding to the intersection of the respective amplitude level characteristic curves of the two signals.

[Problems with background technology]

However, the tracking error signal T and RF
In some cases, it may be desirable to preferentially set the detection sensitivity of one of the detection sensitivity to the best state as necessary. for example,
At the end of the search operation by the search mechanism, it is desirable that the detection sensitivity of the tracking error signal T is the best in order to quickly stop the target focus row, and during the playback operation, the detection sensitivity of the tracking error signal T is preferably the best. It is desirable that the RF multiplied signal detection sensitivity be the best because the light beam is unlikely to deviate from the bit string even if the RF signal is slightly reduced. However, the focus adjustment means of the conventional optical disk record reproducing apparatus does not have the above-mentioned applicability as described above.

[Purpose of the invention]

This invention was made in consideration of the above-mentioned circumstances, and is designed to give priority to the detection sensitivity of the tracking error signal and the R-F signal to achieve the best condition as necessary. It is an object of the present invention to provide a focus control circuit for an optical disc record playback device that can adjust the focal position of a light beam by an appropriate amount.

[Summary of the invention]

That is, the focus control circuit of the optical disc record playback device according to the present invention has an objective lens and a light receiving section for a disc on which digitized data obtained by encoding information signals has been recorded in a plurality of focus rows. The optical binoquazzo reads out the digitized data by tracing it, and generates an RF multiplied signal based on the output signal of the optical binocuazzo depending on the presence or absence of pits in the bit string, and demodulates the RF multiplied signal. means for extracting the digitized data; and generating a tracking error signal corresponding to a shift in the forward and reverse directions of the optical binoquag with respect to the bit string based on the output signal of the optical binoquag, and generating the tracking error signal based on the trunking error signal. A tracking servo means for correcting the deviation of the optical pickup in the forward and reverse directions; and a tracking servo means for generating a focus error signal based on the output signal of the optical pickup, and driving and controlling the objective lens based on the focus error signal to correct the focus error. and a focus adjustment circuit that adjusts the focus error signal to set a driving control position of the objective lens by the focus servo means, an envelope detection means for generating an envelope signal corresponding to an envelope signal having an amplitude level of Rp(g); and driving of the objective lens set by the focus adjustment means based on the envelope signal taken out by the envelope detection means. and a focus adjustment control means for variably controlling a control position, the focus adjustment control means varying the drive control position of the objective lens as the RF multiplied signal amplitude level decreases to detect the tracking error signal. The feature is that the sensitivity is increased.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. However, in FIG. 5, the same parts as in FIG. 1 are designated by the same reference numerals 7, and only the different parts will be explained here.

That is, in FIG. 5, the output end of the RF signal generation circuit 19 is connected to the input end of the envelope detection circuit 25. This enrope detection circuit 25 is connected to the input loop 8.
The envelope detection circuit 25 detects a change in the amplitude level of the signal, that is, an envelope signal, and generates and outputs a correction voltage V4 corresponding to the envelope signal.
The output terminal of is connected to the output terminal of the focus adjustment circuit 22 via a resistor R2.

The operation of the above configuration will be described below with reference to FIG. 6. That is, the RF signal generation circuit 19
As shown in Fig. 6(A), the amplitude level of the RF multiplied signal output from the RF signal is constant during the reproduction period,
Further, during the search period, the above-mentioned gluing component comes to occur at the above-mentioned amplitude level. Such a change in the amplitude level of the RF multiplied signal, that is, the envelope signal, is detected by the envelope detection circuit 25, and the envelope detection circuit 25 generates a correction voltage as shown in FIG. 6(B).
Output as 4. In this case, the level change width of the correction voltage v4 during the search period is as shown in FIG.
a, VbO is set to be equal to the voltage difference Vd (=Vb-Va).

The correction voltage v4 as described above is added to the reference voltage v3 output from the focus adjustment circuit 23. As a result, the focus adjustment voltage El becomes v3+v4 as shown in FIG. 6(c), and the level changes as the correction voltage 4 changes.

Here, by adjusting the reference voltage v3 so that the focus adjustment voltage E1 during the reproduction period is equal to the voltage value vb shown in FIG. During the search operation, the level changes according to the correction voltage v4, and the lowest level becomes the voltage value Va.
level.

During the reproduction period, the focus adjustment voltage E1 is equal to the voltage value vb shown in FIG. 4, so the RF multiplied signal amplitude level is maximized and the detection sensitivity is maintained at its best. It becomes like this. Also, during the search period, the focus adjustment voltage E1 is adjusted to a fourth level corresponding to the period of the ripple component occurring in the amplitude level of the RF information.
The voltage changes back and forth between the voltage values Va and Vb shown in the figure. That is, the focus adjustment circuit E is configured such that as the spot of the light beam moves away from the focus row, it approaches the voltage value Vb and increases the interpupillary level of the tracking error signal T9, so that the spot of the light beam becomes the most When the light beam is separated from the bit string (when the spot of the light beam is at an intermediate position between the adjacent bit string), the voltage value vb becomes equal to the amplitude level of the tracking error signal T, and the tracking error signal T is detected. Sensitivity becomes optimal.

Therefore, when the search operation is completed, even if the spot of the light beam deviates from the target bit string, the amplitude level of the tracking error signal T has increased, so that the spot can be reliably drawn into the target bit string. You will be able to do this.

However, even during the reproduction period, if the spot tends to deviate from the bit string being reproduced due to scratches on the surface of the disk 11, the RF multiplied signal amplitude level will decrease at the same time, so the above steps should not be changed. As the waste adjustment pressure El approaches the voltage value va, the detection sensitivity of the tracking error signal T increases, thereby making it possible to prevent the spot from skipping over the track.

Therefore, the focal position of the optical beam can be adjusted so that one of the tracking error signal T and the RF multiplied signal can be preferentially set in the best condition as necessary for each sensing sensitivity. It becomes like this.

Incidentally, as shown in FIG. 7, the envelope detection circuit 2
5 is added to the reference voltage v3 via a time constant circuit 26 consisting of a diode D1, a resistor R3, a capacitor C, an amplifier IC, etc., the focus adjustment voltage E1 becomes As shown in Fig. 8, the tracking sensor can be applied reliably, which is even more effective. In addition, it goes without saying that various modifications can be made without departing from the gist of the invention.

〔Effect of the invention〕

As described above, according to the present invention, the focus position of the optical beam is adjusted so as to give priority to one of the detection sensitivities of the tracking error signal and the RF multiplied signal to achieve the best state. It is possible to provide an optical disc record internal recording device that can adjust.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the RF signal generation means, tracking servo means, focus servo means, trunk skip control means, and focus adjustment means in a conventional optical disc record playback device, and FIG. 2 shows the above-mentioned tracking servo. FIG. 3 is a characteristic diagram of the focus error signal by the focus servo means, and FIG. 4 is a focus adjustment voltage by the focus adjustment means and each amplitude level of the tracking error No. 16 and the RF multiplied signal. FIG. 5 is a block configuration diagram showing an embodiment of the focus control circuit of the optical disc record playback device according to the present invention, and FIG. 6 shows the output waveforms of the main parts in the above embodiment. 7 and 8 are block diagrams and characteristic diagrams showing other embodiments of the present invention. 1Z...Disc, 12...Pickup, 13.
...Objective lens control unit, 14...Beam sinter,
J5...Laser emitter, 16...Photodetector, 17...Objective lens, 18a, 1B+...J',
, -Ping coil, 19...RF signal generation circuit, 20
...Tracking error signal generation circuit, 21.24.
. . . Moving coil drive circuit, 22 . . . Focus error signal generation circuit, 23 . . . Focus adjustment circuit,
25... Envelope detection circuit, 26... Time constant circuit, ■3... Reference voltage, ■4... Correction voltage, EI
...Focus adjustment voltage. Applicant's representative Patent attorney Takehiko Suzue Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] An optical pickup having an objective lens and a light receiving section traces the digitized data obtained by encoding an information signal onto a disk on which the digitized data is recorded in the form of a plurality of pit rows, thereby reading out the digitized data.
Generates an RF multiplied signal corresponding to the presence or absence of bits in the bit string based on the output signal of the optical pickup;
means for performing double signal demodulation processing to take out the dezocured data; and generating a tracking error signal corresponding to the deviation of the optical pickup in the forward and reverse directions with respect to the bit string based on the output signal of the optical pickup; tracking servo means for correcting forward and reverse deviations of the optical pickup based on a tracking error signal; and tracking servo means for generating a focus error signal based on the output signal of the optical pickup and controlling the objective lens based on the focus error signal. an optical disk record reproducing device comprising: a focus servo means for correcting a focus error by driving control; and a focus adjustment means for adjusting the focus error signal to set a drive control position of the objective lens by the focus servo means. an envelope detecting means for generating an envelope f1 number corresponding to an envelope of the RF multiplied signal amplitude level from the RF multiplied signal; focus adjustment control means for variably controlling the drive control position of the objective lens, the focus adjustment control means varying the drive control position of the objective lens as the RF multiplied signal amplitude level decreases; A focus control circuit for an optical disc record playback device, characterized in that the detection sensitivity of the tracking error signal is increased.