JP2571204B2 - Offset adjustment circuit for optical information recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical information recording / reproducing apparatus for recording / reproducing information on / from a disc, and more particularly to an offset adjusting circuit for canceling an offset such as a focus error.

(Prior Art) An optical information recording / reproducing apparatus which digitally records various kinds of information on a recording medium such as a disk and optically reads and reproduces this information is known.

By the way, conventionally, information is recorded on a reproducing disk by a phase difference recording structure. Therefore, when reproducing information from the disc, the focus error offset and the track error offset of the optical pickup detect a change in the level of the RF signal to obtain an error signal, thereby canceling the offset. A circuit having such a function is usually provided in an optical information recording / reproducing apparatus as an offset adjusting circuit. However,
In the case of such a conventional adjustment circuit, the level of the RF signal is similarly reduced regardless of whether the offset occurs in the positive or negative direction, and the polarity cannot be determined.

Therefore, the polarity is determined by detecting the phase difference between the vibration and the envelope of the RF signal by the so-called wobbling method in which the pickup objective lens is normally vibrated in the positive and negative directions, that is, in the direction perpendicular to the track. Was.

(Problems to be Solved by the Invention) However, since such a conventional offset adjustment circuit executes wobbling and the like in real time during information reproduction, it acts on the reproduction processing system as a disturbance, so to speak, for example, in the servo system. It is not preferable in terms of adverse effects.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an offset adjusting circuit for an optical information recording / reproducing apparatus which can cancel an offset of a focus and a track without giving any disturbance such as a wobbling and can perform a stable operation.

(Means and Actions for Solving the Problems) The present invention solves the above-described problems, and has two different structures including a phase difference recording structure forming a preformat portion and an amplitude difference recording structure forming a data portion. In an offset adjustment circuit of an optical information recording and reproducing apparatus for canceling an offset of a focus error signal or a track error signal obtained by reproducing from a disk having an information recording unit,
Offset detection means for generating, from the focus error signal or the track error signal, a signal having a linear relationship with an offset generated in a focus error signal or a track error signal obtained from a boundary area between the two information recording units during the tracking control operation. The method further comprises canceling the focus error signal or the track error signal generated in the boundary area of the recording structure based on a signal having a linear relationship with the offset generated by the offset detecting means.

(Embodiment) A preferred embodiment embodying the present invention will be described below.

First, an outline of an optical information recording / reproducing apparatus will be described with reference to FIGS. 5 to 8 in order to clarify the present invention. FIG. 5 is a schematic diagram showing a disk and a pickup, FIG. 6 is a perspective view of the disk, FIG. 7 is a longitudinal sectional view of the disk cut in a radial direction (X direction in FIG. 6), and FIG. FIG. 9 is a longitudinal sectional view of the disk before writing in the circumferential direction (Y direction in FIG. 6), and FIG. 9 is a sectional view of the disk after data writing in the circumferential direction.

In the following description, components having the same functions are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 5, the disk 50 is a center spindle motor 51.
The disk 50 is rotated at a constant speed, and an optical pickup 52 is disposed opposite the disk 50.

The recording track 60 is sequentially formed in the disk 50 in the circumferential direction, and one round of the track 60 is further formed in a pre-format section.
It is divided into a plurality of sectors 63 including 61 and a data section 62 (or a group section 64). Various information such as a synchronization signal, track address information, and a sector number are recorded in the pre-format section 61 by a phase difference recording structure having irregularities having a depth of about λ / 8, for example. The data section 62 can record digital data of several hundred bytes. This recording identifies the designated track address and sector number, and stores the ninth data in the flat group section 64 which is a non-recording section shown in FIG. As shown in the drawing, a hole is formed and irregularities are formed, thereby performing the amplitude difference recording structure. As a result, as shown in FIG.
The light beam 71 converged by the objective lens 70 provided in the pickup 52 hits the unevenness, and the recorded data can be read by the amount of reflected light.

A track guide groove formed at a depth having a phase difference of, for example, about λ / 8 with respect to the track 60 is provided on both sides of the track 60, and a track error can be detected by a so-called push-pull method.

Next, FIGS. 1 to 4 show the main components according to the present invention.
This will be specifically described with reference to the drawings. FIG. 1 is an electric circuit diagram of a servo system including an offset adjusting circuit according to the present invention.
FIG. 3 is a specific electric circuit diagram of the offset detection circuit in FIG. 1, FIG. 3 is a time chart of signals in each section in FIG. 1, and FIG. 4 is a time chart of signals in each section in FIG. .

First, in FIG. 1, reference numeral 1 denotes a four-division photodetector incorporated in the pickup 52. The light beam 71 reflected from the disk is photoelectrically converted and extracted as an electric signal proportional to the size of the light beam 71. Each of the blocks 1a, 1a, 1a, 1a constituting the photodetector 1 has an adder 2,
3, 4, 5, and 6 are connected in a predetermined combination. The outputs of the adders 2 and 3 are input to a subtractor 7, the focus error signal S is obtained at the output of the subtracter 7, and the outputs of the adders 4 and 5 are input to a subtractor 8, A track error signal St is obtained at the output of FIG. On the other hand, all blocks 1a, 1a, 1a, 1
An RF signal (Sr) containing information is obtained at the output of the adder 6 that adds the output of a. Thus, the quadrant photodetector 1
The respective error signals are obtained by performing a matrix operation on the output of.

Each error signal S and St are inverted amplifiers 9, 10 and 11,
Amplified by 12 and output terminal 1 of each servo system
3,14 give a signal S ₀ and St ₀ of Fuo Kas errors and Toratsukuera amplified to supply it to Akuchiyuta the pickup 52.

Figure 3 is such RF signals Sr, air signals S ₀ and St ₀
FIG. A shows the case of the offset occurring on the negative side,
FIG. B shows the case where the offset is zero, and FIG. C shows the case where the offset occurs on the positive side. Output level is relatively small portion S ₁ in RF signal Sr At a figure A is a waveform of the Purifuomatsuto portion 61, and the output level is relatively large portion S ₂ is the waveform of the data section 62.

By the way, as described above, the recording of the preformat unit 61 has a phase difference recording structure, and the recording of the data unit 62 has an amplitude difference recording structure. As a result, the waveform F is added to the focus error signal S ₀ and the track error signal St _0.
s appears. This waveform Fs is recorded on the disk in a form having a phase difference recording structure and an amplitude difference recording structure.
Because of the inclusion of two different information recording sections, the difference between these different structures appears as a distorted waveform proportional to the focus error signal or the like corresponding to the portion of each structure, especially the preformat section of the recording track. The level of the shake waveform Fs increases as the offset increases, and the polarity of the shake waveform Fs itself is observed as inverted from FIG. 3A and FIG.

Next, the offset adjusting circuit according to the present invention will be described more specifically. First, an offset detecting circuit 15 is connected to the output terminal 13, and this output is connected to the [+] input of the inverting amplifier 9. Further, an offset discriminating circuit 17 is formed by connecting a sample & hold control pulse generating circuit 16 to the offset detecting circuit 15.

The detection circuit 15 is configured as shown in FIG.
And 19 are switching FETs, C is a capacitor, 20 is a buffer amplifier, 21 is an amplifier, and R ₁ and R ₂ are resistors. First,
The focus error signal ₀ is input to the anode of the switching FET 18. The signal _{S 0} also in Figure 4 indicated by _{S 0.} The switching FET 18 is turned on / off by a pulse signal Ssh from the control pulse generation circuit 16.
That, and samples the pulse signal Ssh is turned ON FET18 the period T is in the tracking control operation, as shown in FIG. 4, and performs the hold OFF the FET18 a period T _2. An offset voltage Sa is detected at the output of the buffer amplifier (op-amp) 20 by this sample-and-hold operation, and this voltage Sa is further multiplied by α by the amplifier 21 [α =
It is amplified 1- (R ₂ / R _1)]. The output signal S ₀ of the amplifier 21 is input to the inverting amplifier 9, are added to the Fuo Kas error signal S to Cancel the offset in real time.

Thus, offset detection circuit 15 will determine the level and polarity of the dumped accompanying shaken waveform voltage, which generates an output signal S _0, distortion caused by waveform dumped to the output terminal 13 in the servo system Make sure no voltage appears.

In addition, the switching servo 19 turns on the focus servo system.
ON before the closed loop in the state, the buffer amplifier
The electric charge of the capacitor C is discharged by grounding the 20 [+] terminals. As a result, the offset voltage Sa output from the buffer amplifier 20 is set to zero.

As described above, in the offset discriminating circuit 17, when the relationship between the shake voltage of the shake waveform and the focus offset is non-linear, the gain is controlled in a non-linear manner so that the gain is preset by a microcomputer or the like, and α is determined. You can also change the value. When canceling the offset in this way, every time a different disc is reproduced, the offset cancel voltage is set so that a predetermined cancel operation is performed first, and the initial setting is performed during normal operation. The value may be maintained.
Further, in consideration of time-dependent temperature drift and the like, the offset cancel amount may be detected at regular intervals, and the cancel may be performed periodically.

Although the focus servo system has been described above, the other track servo system is configured in exactly the same way, 22 is an offset detection circuit, 23 is a sample and hold control pulse generation circuit, and 24 is an offset discrimination circuit. These circuits 22 and 23 function in exactly the same way as the circuits 15 and 16.

(Effects of the Invention) As described above, the offset adjustment circuit of the optical information recording / reproducing apparatus according to the present invention has two different structures including the phase difference recording structure forming the preformat section and the amplitude difference recording structure forming the data recording section. In an offset adjustment circuit of an optical information recording / reproducing apparatus for canceling an offset of a focus error signal or a track error signal obtained by reproducing data from a disc having an information recording unit, during a tracking control operation, an offset adjustment circuit is used to detect An offset detecting means for generating a signal having a relationship between an offset generated in the obtained focus error signal or track error signal and a waveform from the focus error signal or the track error signal, wherein the offset generated by the offset detecting means is linear. Recording based on the signal having the relationship Since the offset of the focus error signal or the track error signal generated in the boundary region of the structure is canceled, the offset of the focus error and the tracking error can be substantially lost in real time without giving any disturbance such as wobbling to the pickup. And a stable operation can be performed without adversely affecting the servo system and the like.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a servo system including an offset adjusting circuit according to the present invention, FIG. 2 is a specific electric circuit diagram of an offset detecting circuit in FIG. 1, and FIG. 3 is a signal in each section in FIG. FIG. 4 is a timer chart of signals at various parts in FIG. 2, FIG. 5 is a schematic diagram showing a disk and a pickup, FIG. 6 is a perspective view of the disk, and FIG. 7 is a radial direction of the disk. 8 and 9 are longitudinal sectional views of the disk cut in the circumferential direction. 15, 22… Offset detection circuit 16, 23… Sample & hold control pulse generation circuit 17, 24… Offset discrimination circuit 50… Disc 61… Preformat part 62… Data part

Claims (1)

(57) [Claims] 1. A focus error signal or a track error signal obtained by reproducing data from a disc having two different information recording sections each having a phase difference recording structure constituting a preformat section and an amplitude difference recording structure constituting a data recording section. An offset adjustment circuit of an optical information recording / reproducing apparatus for canceling an offset of a signal having a linear relationship with an offset generated in a focus error signal or a track error signal obtained from a boundary area between the two information recording sections during a tracking control operation. Offset from the focus error signal or the track error signal, and the focus generated in the boundary area of the recording structure based on a signal having a linear relationship with the offset generated by the offset detector. Error signal or track error An offset adjustment circuit for an optical information recording / reproducing apparatus, which cancels a signal offset.