JPS59152569A - Disk record reproducer - Google Patents

Abstract

PURPOSE:To apply immediately the stable and assured tracking servo even when a searching action is over by providing a DC voltage converting circuit and correcting the DC offset voltage value of a tracking error signal in response to the output signal of said voltage converting circuit. CONSTITUTION:The track jump signal K delivered from a tracking servo circuit 23 in a search mode is supplied to a DC voltage convering circuit 24 via an actuator coil 15. The current flowing to the coil 15 is converted into a voltage signal by a resistance R1 and supplied to an integration circuit to produce a mean DC voltage signal Vc. Then the signal Vc is supplied to an adder 26 via a reverse amplifier 25 in the form of a tracking error correcting signal DELTAT. This signal DELTAT is added to a tracking error signal T, and these added signals are delivered to the circuit 23. When an objective 12 is deflected toward the plus side, the correcting signal DELTAT of negative voltage is added to the signal T. Thus the offset voltage +VT1 is corrected.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a disc record corner generator suitable for, for example, a CD (optical converter disc) system DAD (digital audio disc). In particular, the present invention relates to a device that can immediately stop the movement of the pickup and apply tracking servo when the pickup finishes jumping into the truck.

[Technical background of the invention]

Recently, in the field of audio equipment, digital recording and reproducing systems using PCM (percussion code modulation) technology are being adopted in order to achieve high fidelity reproduction as much as possible. In other words, this is called digital audio, and the audio characteristics often depend on the customization of the recording medium, making it far superior to the conventional analog recording method. 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. Regardless of which method is adopted, the remanufacturing equipment that embodies it must be able to satisfy a variety of advanced control functions and performance that are not found in American equipment. There is.

In other words, if we take the CD system as an example,
Transparent birch with a diameter of 12 [1] and a thickness of 1.2 [1], f 1
A 1M disk is coated with a gold FEW film that forms bits (irregularities with different reflectivity and emissivity) corresponding to digitized (PCM) data, and is heated to approximately 500 to 200 Cr using the CL (constant linear velocity) method. .
The disc has a track pitch of 1.6 [μm], and a huge amount of information is recorded in the program area (radius 25 to 5 seconds (an), allowing for approximately one hour of stereo playback on one side. This can be easily seen from the fact that the index data is recorded in the equal-doin area (radius 23 to 25 (11π)).

By the way, in the above-mentioned CD system disc record playback device, what is particularly important is that in order to clearly read out the digitized data recorded on the disc, the light beam irradiated from the pickup is directed from the bit string of the disc. Is there a tracking error system so that it accurately traces the pit no. n (tracking servo).

FIG. 1 shows a conventional tracking servo means, in which reference numeral 10 is a disk, on one side of which a bit string lea is recorded.

A pickup 1 is provided below the disk 10 in the figure. This pickup 11 includes an actuator 13 that controls the objective lens 12, a semiconductor laser 16, a beam brick 17, a reflector 1B, 20.1
It is composed of a 74-wavelength plate 19, a photodetector 21, etc., and is movable in the radial direction of the disk 10 by a pickup feed motor (not shown). The actuator 13, which is located below the disk IO of the pickup 11 in the drawing, works with the objective lens 12 and a magnet (not shown) to move the objective lens 12 in the torrent angle direction (in the radial direction of the disk 100 (arrow 14). )) The objective lens 12 includes an actuator coil 15 and the like for moving the light beam emitted from the semiconductor laser 16 to the beam splitter J7 and the first reflecting mirror 18.1/1. The light is irradiated via a four-wavelength plate 19. Therefore, the light beam is focused (spot) on the signal recording surface of the disk 10 by the objective lens 12, and is reflected depending on the presence or absence of a bit string on the disk 10. It will be done. This reflected light travels backward through the objective lens 12 and passes through the 1/4 wavelength plate 19.
, passes straight through the beam splitter 17 via the first reflecting mirror 18, and passes straight through the beam splitter 17 via the second reflecting mirror 20 to the photodetector 21.
The light is received by the

Here, the photodetector 21 is of a so-called four-division type in which four detection areas PDa=PI')d made of, for example, photodiodes are arranged point-symmetrically. corresponds to the tracking direction of the previous station pit row 10H, and arrow B-B corresponds to the bit row tangential direction, and the photodetector 21 aligns the dividing line with these arrows A-A and B-B to detect the detection area. PDa to PDd are arranged.

These configuration regions PDa to PDd each have a detection signal P a = P having a frequency characteristic corresponding to the presence or absence of a bit.
d is output 4 to an information signal demodulation circuit, a focus servo circuit, etc. (not shown).

Then, the detection signals Pa and Pc output from the detection areas PDa and PI)c located at diagonal positions, and the detection area PD
Detection signals Pb and Pd output from Pb and PDd are added to each other via resistors Ra to Rd, respectively, and are supplied to the tracking error signal generation circuit 22. This tracking error signal generation circuit 22 converts the phase ratio υ of the two supplied signals (Pa + Pc) and (Pb + Pd) into a difference signal (Pa + Pc) - (Pb + P
d) and convert the difference signal to low/? This voltage signal is converted into a change in voltage level through a Nufilter (not shown), etc.
This is a tracking error signal T corresponding to a shift (tracking error) of the spot of the light beam in the forward and reverse directions. That is, as shown in FIG. 2, for example, this tracking error signal T becomes a signal of O [■] level when the spot of the light beam is correctly positioned on the pit row P, and the tracking error signal T becomes a signal of the O [■] level when the spot of the light beam is correctly positioned on the pit row P. Corresponding to the positional deviation in the direction, positive and negative voltage signals are output. And this tracking error signal T
The actuator coil 1 is
5 so that the spot is always correctly positioned on the bit string P.
is controlled, and tracking servo is applied here.

The tracking servo means during disc playback has been described above, but a special feature of this type of disc record angle generation device is the track jumping means, for example, from the digitized data recorded on the disc 10. In order to quickly select (search) an arbitrary data portion, a high-speed search mechanism (not shown) is provided, which moves the pickup 11 at high speed in the radial direction of the disk 1θ based on a track jump operation command given from the outside. are doing. That is, the high-speed search mechanism locates and outputs the distance information between the bit string currently being processed by the pickup port and the target bit string based on the above-mentioned truck jumping operation command, and also locates and outputs the distance information between the bit string being picked up and the target bit string. disk 10
The moving direction information indicating whether to move in the inner circumferential direction or the outer circumferential direction is calculated.

A track jumping signal Klp and a search switching signal are generated based on the distance information and moving direction information, and the track jumping signal and the search switching signal are supplied to the tracking servo circuit 23. It is.

Here, in order to receive the above-mentioned track jump signal, the pickup 1 is moved toward the outer periphery of the disk lθ, that is, the objective lens 12
When moving to the (''-) side in Figure 1, correct the positive electrode 1 and move the objective lens 12 towards the inner position, that is, the (-) side in Figure 1.
When moving to 11411, the voltage signal has negative polarity.

In addition, when the tracking servo circuit 23 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 sends the track jumping signal K to the actuator. K is supplied to the coil 15. Therefore, the objective lens 12 receives the track jumping signal K.
Accordingly, the feed motor of the pickup 11 is rotated to move the objective lens 12, which is a pickup plate, in the same direction. The target bit string is moved at high speed in a certain direction, and only spot track jumps are performed.

Here, when the pickup moon is moved in the radial direction of the disk 1o as described above, the spot crosses a plurality of bit strings, so that the tracking error signal T becomes as shown in FIG. It is output as a continuous AC waveform as shown in the figure.However, since the tracking error signal T in this AC waveform is cut off by the tracking servo circuit 23 as described in 7 above, the actuator coil 15, and is not provided to the tracking servo.In this case, the tracking emitter number T is the bit string crossed by the spot, for example, by counting the 0 [■] level crossing points. This number is used to calculate the moving distance information of the pickup.Therefore, when the moving distance information matches the above-mentioned distance 111: 111, the search operation ends, and at this time, the above-mentioned truck The generation of the jump signal and the search switching signal are stopped.
The tracking servo circuit 23 outputs the tracking error signal T to the actuator coil 15 again, and performs tracking servo.

[Problems with background technology]

However, in reality, while the pickup and the second are being moved in the radial direction, the tracking servo is turned off.
Since the track jumping signal K is supplied to the actuator coil 15, the objective lens 12 is set at (+) in FIG.
) side or (-) side. Therefore, the reflected light from the disk 10 is transmitted to the photodetector 21.
Detection areas (PDa, PDd) and (PDb) lined up in the pit row tangential direction (arrow 1'3-B).

Unbalanced irradiation to two areas of PDc)
Resoshimari. Correspondingly, when the objective lens 12 is biased towards the (+) side and (-)Ill, the tracking error signal T,'+'r,Kl is positive as shown in Fig. 3(B) and (c). or negative DC offset voltage +VTI 1-■
T2 appears, and the tracking error (g"+,
A peak level difference occurs between the positive voltage region and the negative voltage region with respect to the 0 [■] level of Tt, and one control region t, / ~ 1o is used to draw the spot to the target bit string P.
and t, ~to is the other control region t. −1,/and t
. ~t,''. Therefore, when searching for the target bit string P, the tracking servo, for example, (C
) When the special characteristic of the book shown in the figure is turned on, the spot is pulled toward the bit string P, but the acceleration energy pulls it in the opposite direction to the control region t. -1
2'' cannot be absorbed, so the target bit string PK enters the control area of the adjacent bit string Q. Then, in the bit string Q as well, one control area to'''
to is the other's control aIf11!1 area 'In'''11
Since there are so many bit strings, the control area of the bit string Q is exceeded.In the end, the spot ends up jumping into the bit string one after another, and the pickup 11 is stopped at a position far away from the target bit string P.

This makes it impossible to perform accurate search operations.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a disc record grinding system which can improve the above-mentioned drawbacks, and can immediately stop the movement of the pickup when the pickup finishes jumping into the track, and perform tracking servo.

[Summary of the invention]

In other words, the disc record recording device according to the present invention has the following features:
A DC voltage conversion circuit extracts the current flowing through the actuator coil for controlling the tracking direction of the pickup and generates an average DC voltage signal, and a DC voltage conversion circuit generates a tracking error signal based on the output signal of this DC voltage conversion circuit.
The present invention is characterized by comprising means for correcting an offset voltage component.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 4, the same parts as in FIG. 1 are designated by the same reference numerals, and only the different parts will be explained here. That is, the track jump signal outputted from the tracking servo circuit 23 during the search is supplied to the DC voltage conversion circuit 24 via the actuator coil 15 . This DC voltage conversion circuit 24 is composed of a resistor R1 and an integrating circuit consisting of a resistor R and a capacitor C, and converts the current flowing through the actuator coil 15 into a voltage signal by the resistor R1 and integrates supply the circuit,
This average curvature current ratio signal Vc, which generates the average DC voltage signal Vc, is supplied to an adder 26 via an inverting amplifier 25 as a tracking error correction signal ΔT. This adder 26 adds the tracking signal T and the tracking error correction signal ΔT and outputs the result to the tracking servo circuit 23.

Here, the tracking error correction signal ΔT will be explained. That is, as described above, the deviation of the objective lens 12 during the search operation corresponds to the track jump signal K. Therefore, the track jumping signal K is supplied to the actuator coil 15, and the current flowing through the actuator coil 15 is transferred to the DC voltage conversion circuit 24.
The voltage signal supplied to the resistor R1 and detected is a signal corresponding to the direction of deflection of the objective lens 12 and its magnitude. (The objective lens 12 is biased toward the (+) side)
, a positive voltage is generated. Similarly, when the track jump signal K has negative polarity (the objective lens 12 is (-
), a negative voltage will be generated.

The voltage signal generated by the resistor R1 is converted into an average DC voltage signal VC by the integrating circuit, and is supplied to the inverting amplifier 25, where the polarity is inverted. As a result, the tracking error correction signal ΔT has a negative polarity when the objective lens 12 is on the (+) side, and a negative polarity (-) as shown in FIG.
The DC voltage generated in the tracking error signal T has a positive polarity when the tracking error signal T
The voltage signal has a polarity opposite to the offset voltage. Therefore, when the objective lens 12 is biased toward the (→-) side, a negative voltage correction signal ΔT is added to the tracking error signal T. Therefore, the tracking error signal T1 shown in FIG. 3 ([3)K is offset voltage +■
T1 is corrected to lower the voltage level so that the peak values of the positive and negative voltages are equal. Similarly (-) 1j
111, the trunking error signal T2 shown in FIG. 3(C) is corrected by 1ifi and the voltage level is lowered by the positive voltage correction signal ΔT. , the peak values of the positive voltage and the negative voltage H2 are set to be equal.

Therefore, regardless of the position of the objective lens 12, the tracking error signal T+ΔT output to the tracking servo circuit 23 is determined between the one control area and the other control area a.
l Since the IFI range is always set equal to the IFI range, when the tracking servo is turned on within the control range of the target bit string at the end of the search operation, the target bit string is reliably set without skipping over the bit string as in the conventional method. It is possible to draw spots into the bit string.

It should be noted that the present invention is not limited to the first embodiment described above, and can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to detect the offset position and direction of the objective lens with a simple configuration and to perform level correction for the DC offset voltage of the tracking error signal, even at the end of the search operation. Stable and reliable tracking servo can be applied while reconnaissance.

Therefore, it is possible to provide an extremely good Hiko disc record reproducing apparatus that can accurately search and read any data recorded on a disc in a short time.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the tracking servo means and search means of a conventional disc record playback device.
FIG. 2 is a characteristic diagram showing the tracking error signal by the tracking servo means, FIG. 3 is a characteristic diagram illustrating changes in the tracking error signal during a search operation, and FIG. 4 is a characteristic diagram for the disc record according to the present invention. FIG. 5 is a characteristic diagram showing the characteristics of the tracking error correction signal in the above embodiment.
...Objective lens, 13...Actuator, 14...
- Tracking direction, 15... Actuator coil, 16... Semiconductor laser, 2゛1... Photodetector, 22... Tracking error signal generation circuit, 23
... Tracking servo circuit, 24 ... DC voltage conversion circuit, 25 ... Inverting amplifier, 26 ... Adder, T
...Tracking error signal, K...Track jump signal, L...Search switching signal, △T...Tracking error correction signal. Applicant's agent Patent attorney Takehiko Suzue 1o
Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A pickup traces the pit string on a disk on which digitized data obtained by encoding an information signal is recorded as a bit string, and reads out the digitized data, based on the output signal from the pickup. A tracking error signal corresponding to the deviation of the pickup in the forward and reverse directions with respect to the bit string is generated, and an actuator coil for controlling the tracking direction of the pickup is driven based on the tracking error signal, so that the pickup is shifted in the forward and reverse directions with respect to the pit string. tracking servo means for correcting the deviation of the disk; and track jumping means for receiving a track jumping command and supplying a track jumping signal to the actuator coil to move the pickup in the radial direction of the disk. In a disc record playback device, there is provided a DC voltage conversion circuit that takes out the current flowing through the actuator coil and converts it into an average DC voltage signal, and a DC offset of the tracking x error signal based on the output signal of the meandering voltage conversion circuit. 1. A disc record playback device characterized by comprising means for correcting a pressure component.