JPS60170035A - Control signal production method for optical information reproducer - Google Patents

Abstract

PURPOSE:To correct a shift signal contained in a tracking error signal and to improve the feed servo accuracy of an optical pickup head, by correcting the shift component of the tracking error signal after producing the differential signal at a non-pit part of an information track and also controlling the shift of an optical reproduction head with said shift component. CONSTITUTION:The information on an information recording carrier such as an optical disk 1, etc. is detected by an optical reproduction head 2. Some of these detection signals extract output signals via a tracking error detecting circuit 3; while other detection signals extract output signals via a shift detecting circuit 40 respectively. The servo feed control signals are extracted via a phase compensation circuit 42 and an amplifier circuit 43 and drive a head feed mechanism 8. The output signal of the circuit 40 is equal to a differential signal of the signal at a non-pit part of the information track of the disk 1. This differential signal compensates the shift component of the tracking error signal and at the same time is used as a control signal for shift of the head 2. Thus the shift signal produced from each output signal on a photodetecting surface is approximately proportional to a shift amount as far as the shift amount is small. Thus it is possible to always actuate an objective lens at a place near a neutral point by driving with control the mechanism 8 so as to set the tracking error signal at 0.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to the control of an apparatus for reproducing recorded information by irradiating a light beam onto an optically readable information recording carrier.
・Transfer of the optical reproducing head that follows and scans the IH information track Optical information reproducing 1 to obtain the tilJH signal (Regarding the control of residue 1g generation method.

[Prior art and its problems]

In general, 1N information of audio/video and 6 types of data is recorded in optical form, that is, in the form of pits or not.
I! record on a carrier, and eject the original beam onto it with a minute spot.
(An optical information reproducing (recording) device is known as a device that reads 1n information recorded by six shots.

Examples of such V2 ft include original discs known as compact discs and video discs. In the original academic information system M such as this), one of the conditions for correctly reading the information on the writing quadruply is that the light beam is set on the information track (pit). example)
The irradiation position of the light beam is set to 1 so that the center of the
lJulII+, so-called automatic track scanning control 1
It is necessary to perform tracking servo III (hereinafter referred to as tracking servo). The track pitch of this 4th gear is approximately 1.6
It is extremely narrow, µm, and a set meal precision of about 0.1 µm is required. However, the fixed range of such a tracking servo (:c, for example, approximately 1 in the case of a video disc)
In the case of a compact disc, approximately 35 mm is required. Therefore, conventionally, as a tracking servo means, a method has been used in which a first means for scanning an area within a minute 411) area is combined with a second middle stage for scanning over a wide range. Generally, the first means is included in an optical unit, referred to as an optical pickup head or an optical reproducing head, and the second means includes a method for transporting this entire head. A method shown in FIG. 1 is known as an example of such tracking servo. That is, information on an information recording carrier such as an optical disk (1) is detected by an optical reproducing head (2), and this detection signal is sent to a tracking error detection circuit (3), a phase compensation circuit (4), and a tracking error detection circuit (3).
A part of this output signal is used as the tracking control number 1g of the optical reproducing head +21, and the other part is further sent to the phase compensation circuit (6) and the amplifier circuit (single/1ψ This output signal is used as a servo feed tt control signal to drive the head feed mechanism 18).

In this case, the control signal of the second means is obtained by detecting the drive signal (drive voltage or drive current) of the first means. The first means and second means will be explained below with reference to FIG. 2 as well as FIG. 1. This is the first means of driving@J mechanism (
Utilizing the fact that the amount of displacement of lO) has a correlation with the drive signal, the low-frequency component of this drive signal is used as a control signal for the second means to drive the drive mechanism (81. That is, @1
The driving mechanism (10) of the first means always moves the optical reproducing head (2) in which the first means is carried out in the direction in which it operates at its mechanical neutral point. This prevents the drive mechanism (10) from deviating from its one-motion range. In this case, the optical system is such that the original beam emitted from the light source (11) is made into a parallel beam by the collimation lens (12), passes through the beam splitter (13), is focused by the objective lens (14), and is focused onto the original disk +11. Furthermore, the reflected light reflected from the original disk (11) passes through the objective lens (14) again, is reflected by the beam splitter (13), and is guided to the photodetector (15). However, in such a conventional tracking servo, the drive signal applied to the drive mechanism (l) of the first means is connected to the control signal, that is, the track center and the irradiation light beam. It is the tracking error signal that indicates the positional deviation of the drive mechanism (10) plus compensation for the frequency characteristics of the phase and gain of the drive mechanism (10).Therefore, in the second means, the tracking error signal of the drive mechanism (3) in this second means is added. In addition to compensating the frequency characteristics, the compensation characteristics of the first means must also be compensated, and therefore the servo band of the second means is suppressed to a low frequency range where the influence of compensation is small.As a result, the above-mentioned conventional In this method, a problem arises in terms of accuracy in that a phase lag occurs and it is not possible to perform i?1IJll11 for minute shifts.

Furthermore, conventionally, a tracking error signal has been used as the flilJ M signal of the first means, which is the basis of the control signal of the second means, but a method for obtaining this tracking error signal is as shown in FIG. The light receiving surface (30a) is divided into two by (3'ObJ), and the photodetector (31
) is known as the Pu5h-Pull method. However, the tracking error signal by the conventional Pu5h-Pul I method requires the drive mechanism of the first means (
10) includes a shift (error) signal due to the displacement. For example, in the case of a pick-up knob head in an optical system as shown in FIG.
The original beam (32) on a) and (30b) shifts as shown in FIG. 3 in proportion to the displacement of the objective lens (14). Therefore, even if the track of the optical disk (1) and the irradiation light beam match, if the objective lens (14) is displaced, the tracking error signal will not become zero, and the track of the optical disk (1) and the illumination source beam will appear to be There is a problem that the control signal of the second means becomes incorrect, including a shift (error) signal. .

[Purpose of the invention]

An object of the present invention is to provide a control signal generation method for an optical information reproducing apparatus that corrects the shift number 1g included in the tracking error signal due to Pu5h-Pull p and adjusts the stacking of the feed servo of the original pickup head Il and Ii. It is about providing.

[Summary of the invention]

The present invention detects the reflected light of the light irradiated onto the information recording carrier with a photodetector having a light-receiving surface divided into two in the tangential direction of the information track of the information recording carrier. A control signal that generates a differential signal of the signal of the non-pitted portion of the information track out of the two output signals, and uses this difference @ signal to move the optical reproducing head that follows and scans the information track in a direction across the information track. The present invention provides a method for generating a side-turning signal for an optical information reproducing device.

〔Effect of the invention〕

According to the present invention, the tracking AUml is generated by generating a differential signal, that is, a shift signal, for the non-pitted portion of the information track.
By correcting the shift component of No. iii and controlling the movement of the optical reproducing head using this shift component, it is only necessary to compensate the frequency characteristics of the head feed control-j system, and therefore the servo band of the head feed mechanism can be sufficiently It is possible to perform good tracking servo of 4:Rl1ffl.

[Practice of invention? IJ) Hereinafter, a method for generating a 1lilJMl* number according to the present invention will be explained with reference to FIGS. 4 to 6. /A4 diagram is
FIG. 1 is a system diagram showing an embodiment of the present invention. That is,
The information on the information recording carrier such as the original disk (11, etc.) is detected by the optical reproducing head (2), and part of this detection signal is sent to the tracking error detection circuit (31), and the other part is sent to the shift detection circuit (31).
40] respectively, and the output circular tracking error detection circuit ゛f3 of the shift detection circuit (40) is taken out.
) is input to the shift correction circuit (41), then taken out via the phase compensation circuit (4) and the amplifier circuit (5), and this output signal is used as a tracking control signal for the optical reproducing head (2). ing. On the other hand, the other part of the output of the shifted output circuit (40), that is, the shift (error) signal, is outputted via the phase compensation circuit (42) and the amplifier circuit (43), and this output signal is used as the servo feed control signal. It drives the head feeding mechanism (8).

In this case, the output No. 18 of the shift detection circuit (40) is the non-pied signal in the information track of the original disk il+.
This differential 4fb signal is used as a control signal to compensate for the shift component of the tracking error signal and to move the optical reproducing head (2) to the transport side. As a method of extracting the signal from the non-pitted part of the information trunk, the light receiving surface (30a
), (30b) each output signal IA shown in FIG. 5 1b+,
It is preferable to use IB as a peak detection circuit as shown in FIG. 5 (cl) using the circuit shown in FIG. 5 (1b+).

Also, the information signal Io obtained from each output signal IA, IB
= IA + IB (RF signal), as shown in Fig. 6 ial, a non-pit portion is detected and a pulse signal corresponding to the non-bit portion is extracted, and the difference signal I of each output signal shown in Fig. 5 1b+ is obtained.
p-IA-In (Pu5h-Pul l signal) is sampled and held using the circuit shown in Fig. 6 (cl) and the above pulse signal, and shifted as shown in Fig. 6 jdJ (
, VAa)iM number may be generated. Since the shift (error) signal generated in this way is approximately proportional to the shift amount when the shift amount is small, the head feeding mechanism (8) is driven and controlled so that the troughing error 1g becomes zero. For example, the objective lens can always be operated near the neutral point.

Furthermore, this shift ('error) signal is not compensated for the frequency characteristics for the first means as in the prior art, and therefore, in the phase compensation circuit (42) of the head feed control system, the head feed mechanism (8) All you need to do is compensate for the frequency characteristics of
Accurate servo characteristics can be obtained by making the most of the custom-made structure.

Next, compensation for the shift component of the Pu5h-Pull signal Ip will be explained. Generally, the conventional Pu5h-Pull signal Ip includes a true tracking error signal, that is, a difference signal IT=IA-IB component when the objective lens is not shifted, and a shift signal Is, and a shift signal Is when the shift amount is small. Ip, Is are 2k.

Ip=---sin 2φhsinφr+β(1+co
s”φh ) ・=111π I 8=2β ・・・・・・・・・・・・・・・(2)
Here, φh is a phase constant of pit depth, Ir is a phase constant of tracking error, and β is a value proportional to the shift amount. 111 Equation 1)) The first term is a tracking error component, and the second term is a shift component. Therefore, (
By subtracting Is which is 72 times α=(1+cos''φh) from ip shown in equation 1), Ir becomes only the true tracking error component, and stable and highly compensated tracking servo can be performed.

Note that although the above-mentioned tracking is performed by driving the objective lens, the present invention is not limited to this.
Any method that can shift the light beam on the light receiving surface of the photodetector may be used, such as by inserting a rotating mirror in the optical path or shifting the light source. Regarding the division of the light-receiving surface of the photodetector, for example, divisions necessary for focus error detection may be added, and the shape of the light-receiving surface can be modified as desired.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining the conventional method, and Figure 4 is a diagram for explaining the conventional method.
6 to 6 are diagrams for explaining one embodiment of the present invention. 1°° Original disk, 2... Optical Niyu head, 3...
- Tracking g4 difference detection circuit, 4, 42... Phase compensation circuit, 5, 43... Amplifying circuit, 8... Head feeding mechanism, 40... Shift habituation circuit, 41... Shift correction circuit . Representative Patent Attorney Norihiro Chikagi (I5 (and 1 other person)
figure

Claims (1)

[Scope of Claims] (1) The original reflected light irradiated onto the information recording carrier is detected by a photodetector having a light-receiving surface divided into two in the tangential direction of the information track of the information recording carrier; Of the two output signals obtained from the bisected light-receiving surface, a differential signal of the signal of the non-pitted portion of the information track is generated, and an optical reproducing head that follows and scans the information track using the differential signal is used to transmit the information to the optical reproducing head. 1. A method for generating an nlJ control signal for an optical information reproducing device, characterized in that the control signal is a control signal for controlling movement in a direction across a track. (21) The control signal generation method for an optical information reproducing apparatus according to claim 1, wherein the signal of the pit-free portion is a signal obtained by detecting each peak of the two output signals. (3) None The method for generating a control signal for an optical information reproducing apparatus according to claim 1, wherein the signal of the pit section is a signal obtained by envelope detection of each of the two output signals. (4) Pitt-free section The signal difference vth is a signal obtained by detecting the pit-free portion from the information signal of the track obtained from the two output signals and sampling and holding the signal of the pit-free portion of the differential signal of the two output signals. A control signal generation method for an optical information reproducing apparatus according to claim 1, characterized in that: (5) a difference signal between a differential signal of two output signals and a differential signal of a signal of the pitless portion; A control signal generation method for an optical information reproducing apparatus according to claim 1, characterized in that: is a tracking error signal when the optical reproducing head follows and scans the information track. 17) A control signal generation method for an optical information reproducing device according to claim 1, characterized in that the carrier is a four-optical disc. 17) A light source of light irradiated onto the information recording carrier is a semiconductor laser. 1llJ control signal generation method for optical information reproduction/reading as claimed in claim 1.