JPH0554415A - Optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To prevent tracking offset from occurring without depending on wobbling of a guiding groove by radiating three converged spots at a specified interval on the information recording media whose guiding groove is wobbling. CONSTITUTION:The light beam coming from a semiconductor laser 1 is divided into zero-order diffraction beam 4 and + or - 1st order diffraction beam 5 and 6, and forms converged spots 4A, 5A and 6A on an information recording medium 10 by way of a polarizing beam splitter 7, 1/4 wave length plate 8 and an objective lens 9. The beam reflected on the medium 10 is reflected on the splitter 7 and then made to enter into a photodetector 12. At this time, the spot 4A is arranged on a guiding groove 26 and the spots 5A and 6A are arranged on the position displaced by a half of a pitch P of the groove 26 with the groove 26 in between. As a result, even if a differential push-pull method is used, occurrence of tracking offset can be prevented so as to obtain the reproductive characteristics with high quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for detecting a tracking error of an information recording medium having an information track meandering (hereinafter referred to as wobbling) in advance.

[0002]

2. Description of the Related Art Conventionally, as a tracking error detecting method used for a write-once type or rewritable type information recording medium having a guide groove, a well-known so-called push-pull method has been mainly adopted.

However, this method has a drawback that an offset is likely to occur due to, for example, the inclination of the information recording medium. Therefore, measures are taken to remove this offset.

Hereinafter, a method of removing the offset by improving the push-pull method will be described as a conventional example of the present invention described later with reference to FIGS. 1, 6 and 7.

FIG. 1 is a plan view showing an optical path system of a conventional optical recording / reproducing apparatus of the present invention, and FIG. 7 is a connection diagram of a photodetector and an electric circuit in a conventional optical recording / reproducing apparatus of the present invention described later. And these are disclosed in JP-A-61-9424.
It is disclosed as a second embodiment in Japanese Patent Laid-Open No.

The same thing is also shown on pages 127 to 132 of the proceedings of "Optical Memory Symposium '86", which is named the differential push-pull method. Therefore, this name is also referred to here. To

FIG. 6 is a plan view showing a positional relationship between an information recording medium and a focused spot in a conventional optical recording / reproducing apparatus.

First, FIG. 1 will be described. In FIG. 1, the divergent beam from the semiconductor laser 1 is incident on the collimator lens 2 and converted into a parallel beam, and then incident on the diffraction grating 3.

In this diffraction grating 3, three beams are divided into a 0th-order diffracted beam 4 (shown by a solid line), a + 1st-order diffracted beam 5 (shown by a broken line), and a -1st-order diffracted beam 6 (shown by a chain line). Is transmitted through the polarization beam splitter 7 and the quarter-wave plate 8 and is incident on the objective lens 9 to form three focused spots 4A, 5A, 6A on the surface of the information recording medium 10.
To form.

Thus, the collimator lens 2, the diffraction grating 3, the polarization beam splitter 7, the quarter wavelength plate 8 and the objective lens 9 constitute a focused spot forming means.

The reflected beam from the information recording medium 10 passes through the objective lens 9 and the quarter-wave plate 8, is reflected by the polarization beam splitter 7, is focused by the focusing lens 11, and is composed of a plurality of light receiving surfaces. It is incident on the photodetector 12.

In FIG. 6, 13 is a guide groove provided on the information recording medium 10, 14 is a flat portion (hereinafter referred to as a land portion), and the pitch of the guide groove 13 is P.

Focused spot 4A by the 0th-order diffracted beam 4
Are arranged exactly on the guide groove 13. The focused spot 5A by the + 1st-order diffracted beam 5 and the focused spot 6A by the -1st-order diffracted beam (dotted line) 6 are the focused spots 4A.
They are opposed to each other with a space between them and are displaced from each other by Q in different directions from the center of the guide groove 13. The deviation amount Q is set to about half the pitch P of the guide grooves 13.

Further, as shown in FIG. 7, the photodetector 12 is composed of three sets of light receiving elements consisting of at least two light receiving surfaces, and the 0th-order diffracted beam 4 is received by the light receiving surfaces 12A and 1A.
It is arranged so as to receive 2B, the + 1st order diffracted beam 5 is received on the light receiving surfaces 12C and 12D, and the -1st order diffracted beam 6 is received on the light receiving surfaces 12E and 12F.

The outputs from the light receiving surfaces 12A and 12B are input to the differential amplifier 15 and the push-pull signal E0 is generated.

The outputs from the light receiving surfaces 12C and 12D are input to the differential amplifier 16 to generate the push-pull signal E1.

Further, the outputs from the light receiving surfaces 12E and 12F are input to the differential amplifier 17 to generate the push-pull signal E2. The push-pull signal E2 output from the differential amplifier 17 is passed through the gain changer 18. , Adder 19
Entered in. The gain varying device 18 is for varying the gain of the push-pull signal E2.

The adder 19 inputs and adds the push-pull signal E2 output from the differential amplifier 16 and the push-pull signal E2 that has passed through the gain changer 18, and outputs the output E.
3 is input to the differential amplifier 21 through the gain varying device 20. The gain varying device 20 is for varying the gain of the output E3.

The push-pull signal E0 output from the differential amplifier 15 is also input to the differential amplifier 21, and the differential amplifier 21 receives this push-pull signal E0.
The tracking error signal TE is generated from the output E3 that has passed through the gain variable device 20.

Next, the operation will be described. The focused spots 4A, 5A and 6A are the guide grooves 13 of the information recording medium 10.
Alternatively, when the light is on the land portion 14, the light amounts on the two light receiving surfaces are equal, so that the push-pull signals E0, E1, and E2 are zero.

When a positional deviation, that is, a tracking deviation, occurs between the focused spot and the guide groove 13 or the land portion 14, each push-pull signal E0, E1, E2.
Approximately becomes a sine wave signal having the pitch P of the guide groove 13 as a cycle, but as described above, when the information recording medium 10 is inclined, a DC offset component is generated.

In the differential push-pull method, the offset is removed by an electric circuit as shown in FIG. This will be described using mathematical expressions.

Assuming that the amount of deviation between the central focusing spot 4A and the guide groove 13 is X, the output of the differential amplifier 15, that is, the push-pull signal E0 is E0 = A0.sin (2.pi.X / P) + B0 ..

However, A0 is the amplitude of the push-pull signal E0, and B0 is the offset component generated due to the inclination of the information recording medium 10.

The output of the differential amplifier 16, that is,
The push-pull signal E1 is expressed as follows. E1 = A1 · sin {2π (X + Q) / P} + B1

Further, the output of the differential amplifier 17, that is, the push-pull signal E2 is expressed by the following equation. E2 = A2 · sin {2π (X−Q) / P} + B2

However, A1 and A2 are the amplitudes of the push-pull signals E1 and E2, similar to A0, and B1 and B2 are the offset components generated by the inclination of the information recording medium 10 and the like, like the offset component B0.

The three focused spots 4A, 5A, 6
In the above signal obtained by A, the push-pull signal and the offset component have the same proportion, and therefore the following equation is always established. B0 / A0 = B1 / A1 = B2 / A2

When the gain of the gain variable device 18 is G1 and the gain of the gain variable device 20 is G2, and G1 = A1 / A2 and G2 = A0 / 2 / A1, respectively, the output E3 of the differential amplifier 19 is selected. Is expressed by the following equation. E3 = E1 + G1 · E2 = 2 {A1 · sin (2πX / P) · cos (2πQ / P) + B
1}

Further, using the above equation, the tracking error signal TE which is the output of the differential amplifier 21 is expressed by the following equation. TE = E0−G2 · E3 = A0 {1-cos (2πQ / P)} · sin (2πX / P)

As is apparent from the above equation, in the differential push-pull method, the tracking error is calculated by the above-mentioned calculation regardless of the deviation amount Q between the front and rear focused spots 5A and 6A with respect to the central focused spot 4A. The amplitude of the signal TE is Q =
It becomes maximum in the case of P / 2, which corresponds to the case where the front and rear converging spots 5A and 6A are located exactly at the center of the land portion 14 with respect to the central converging spot 4A located on the guide groove 13. ..

On the other hand, in a compact disc on which music information is recorded and a video disc on which image information is recorded, small holes corresponding to information called pits are spirally arranged to form an information track.

In these devices, means for detecting the tracking deviation of the information track to be followed in order to focus and irradiate the laser beam to correctly read out the pit signal on the information track, and a mechanism for performing the correct tracking are provided. I have it.

In the reproduction-only device as described above,
A so-called three-beam method is generally used as a means for detecting a tracking deviation, that is, a tracking error detection method, which is disclosed in JP-B-53-131.
No. 23 or Japanese Patent Publication No. 2-53853.

FIG. 10 is an optical path diagram of a conventional optical recording / reproducing apparatus disclosed in, for example, Japanese Patent Publication No. 2-53853.
In FIG. 10, the same parts as those in FIG. 1 are designated by the same reference numerals.

In FIG. 10, an outgoing beam 1a emitted from the semiconductor laser 1 is a divergent beam, and this outgoing beam 1a is a diffraction grating 3, a polarization beam splitter 7, a collimator lens 2a, a quarter wave plate 8 and an objective lens. After that, the information recording medium 10 is irradiated with light.

The semiconductor laser 1, the diffraction grating 3, the polarization beam splitter 7, the collimator lens 2a, the quarter-wave plate 8 and the objective lens 9 constitute a laser beam irradiation optical path system.

Further, 22 is a concave lens, 23 is a cylindrical lens as an astigmatism lens, 24 is a photodetector for obtaining a reproduction signal, and these are sequentially arranged to form a detection optical path system. There is.

The photodetector 24 includes a light receiving portion 24A having at least four light receiving surfaces, and light receiving portions 24B, 24 having at least one light receiving surface sandwiching the light receiving portion 24A.
It consists of C and.

Semiconductor laser 1 and polarization beam splitter 7
The diffraction grating 3 is provided between and. For this reason,
The beam 1a emitted from the semiconductor laser 1 is the diffraction grating 3
Are separated into a 0th-order diffracted beam 4 (solid line), a + 1st-order diffracted beam 5 (broken line), and a -1st-order diffracted beam 6 (dashed-dotted line). The −1st-order diffracted beam 6 is incident on the collimator lens 2a via the polarization beam splitter 7 and converted into a parallel beam.

Further, the light is incident on the objective lens 9 through the quarter-wave plate 8 to form three converging spots 4A, 5A and 6A on the information recording medium 10.

FIG. 11 is a plan view showing the positional relationship between the focused spots 4A, 5A, 6A and the pits 25 on the information recording medium 10. As shown in FIG. 11, the information track is formed as a row of pits 25, and the interval between adjacent information tracks is P.

Focusing spot 4A by the 0th-order diffracted beam 4
Is located in the center of the information track. The focused spot 5A by the + 1st-order diffracted beam 5 and the focused spot 6A by the -1st-order diffracted beam 6 face each other across the focused spot 4A,
They are arranged so as to be displaced from the center of the information track by approximately one quarter of the track pitch P, that is, approximately P / 4, in different directions.

The laser beam reflected on the surface of the information recording medium 10 is guided to the irradiation optical path system, of which the 0th-order diffracted beam 4A is detected by the light receiving section 24A and the + 1st-order diffracted beam 5 is detected.
And the -1st-order diffracted beam 6 are respectively received by the light receiving portions 24B, 2
It is detected at 4C.

Next, the operation will be described. The pit 25 recorded on the information recording medium 10 is detected by the central focused spot 4A of the 0th-order diffracted beam 4 and reproduced as an electric signal by the light receiving portion 24A of the detector 24.

The tracking error signal indicating the tracking shift of the central focused spot 4A is subtracted from the electric signals of the light receiving portion 24B which receives the + 1st order diffracted beam 5 and the light receiving portion 24C which receives the -1st order diffracted beam 6. Obtained as a signal.

As shown in FIG. 11, when there is no tracking deviation in the central focused spot 4A, the two focused spots 5A and 6A are both offset from the information track by the same distance in the opposite directions, so that the light receiving portion 24B. And the light receiving section 24C
The tracking error signal obtained as a subtraction signal of each of the electric signals is zero.

FIG. 12 is a plan view showing the positional relationship between the focused spot and the pit when the central focused spot 4A has a tracking deviation. In this case, the pit 25 is deviated below the paper surface with respect to the central focused spot 4A.

Further, the deviation between the focused spot 5A and the pit 25 becomes larger, while the deviation between the focused spot 6A and the pit 25 becomes smaller. Therefore, the light receiving unit 2
The tracking error signal obtained as a subtraction signal of each of the electrical signals of 4B and 24C is not zero, and the tracking deviation is corrected by a correction unit (not shown) for returning it to zero.

[0050]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The conventional optical recording / reproducing apparatus shown in 1 is configured as described above, and has the information recording medium 10 having the linear guide groove 13.
In the above, the differential push-pull method has been used as a method for detecting a tracking error signal in which no tracking offset occurs.

However, in recent years, in compact discs (hereinafter referred to as CDs), which are one of the information recording media,
There have been proposed media and standards that allow not only reproduction but also recording.

Specifically, there are a CD write once using a write-once type medium and a rewritable CD rewritable using a magneto-optical type medium.

In this type of medium, a guide groove is provided in advance for tracking during recording,
As in the prior art, the focused spot is recorded while following the guide groove.

However, as another important reason why the guide groove is provided, the information for controlling the rotation speed of the information recording medium and the absolute value address information are included in the guide groove in the form of a wobbling of the guide groove. It is being done.

This is described, for example, on pages 166 to 169 of the "JAS Conference '90" Proceedings. More specifically, the guide groove is wobbling with an amplitude of about 4% of the groove pitch P, and its frequency is defined as 22.05 ± 1 kilohertz.

The number of revolutions of the medium in the recordable CD is controlled so that the linear velocity becomes a constant value within the range of 1.2 to 1.4 meters per second. It is performed by controlling the rotation speed so that the reproduction is always performed at the center value of 22.05 kHz.

Further, the absolute value address information is included in the form of frequency-modulated with a deviation of 1 kilohertz with respect to 22.05 kilohertz.

In the information recording medium having the guide groove as described above, information can be recorded according to the guide groove, and the guide groove is wobbled at a constant frequency, tracking by the differential push-pull method is performed. There are the following problems in using the error detection method.

8 and 9 are views showing the positional relationship between the guide groove having the wobbling and the focused spot. In FIG. 8, the central focused spot 4A is located at the position where the guide groove 26 and the center line 27 coincide with each other. 9 shows the case where the central converging spot 4A is arranged at the position where the guide groove 26 is displaced most from the center line 27 due to the rotational movement of the information recording medium 10. There is. A center line 27 shown in both FIGS. 8 and 9 is an average center line of the guide groove 26, and 28 is a land portion.

Next, each push-pull signal E in the differential push-pull method when the guide groove has a wobbling.
Let's find the general formula of 0, E1, E2. The displacement between the central focused spot 4A and the wobbling guide groove 26 is D
If it is 0, the push-pull signal E0 obtained from the differential amplifier 15 shown in FIG. 7 is expressed by the following equation. E0 = A0 · sin {2π (X−D0) / P} + B0 (1)

When the displacement of the guide groove 26 at the position of the focused spot 5A is D1, the push-pull signal E1 obtained from the differential amplifier 16 shown in FIG. 7 is expressed by the following equation. E1 = A1 · sin {2π (X + Q-D1) / P} + B1 (2)

Similarly, when the displacement of the guide groove 26 at the position of the focused spot 6A is D2, the push-pull signal E2 obtained from the differential amplifier 17 is expressed by the following equation. E2 = A2 · sin {2π (X−Q−D2) / P} + B2 (3)

Further, the tracking error signal TE obtained from the differential amplifier 21 is given by the following equation. TE = E0-G2 · (E1 + G1 · E2) However, symbols A0, A1, A2, B0, B1, B2
P, Q, G1 and G2 are the same as those in the conventional example.

Next, problems will be described with reference to FIGS. As described above, since the linear velocity is constant in the CD, the wobbling pitch W of the guide groove 26 wobbling at 22.05 kHz is 54.4 at a linear velocity of 1.2 m / sec. The value is 6.3 microns when the linear velocity is 1.4 meters per second.

Further, L in FIG. 8 is each focused spot 4
A, 5A, 6A, and in this FIG. 8, L = W /
The case of 4 is shown. The focused spot 4A is located when the wobbling guide groove 26 is just on the centerline 23 of the wobbling, and the two focused spots 5A and 6A at the front and rear are the same as the centerline 27 with respect to the centerline 27. And are displaced by an equal distance Q in the opposite direction.

Since the focused spots 5A and 6A are located at a distance of 1/4 of the wobbling pitch W from the central focused spot 4A, the guide groove 26 is displaced most from the center line 27 of the wobbling. There is.

Therefore, assuming such a state as case 1, the tracking error signal in the differential push-pull method will be obtained. Table 1 shows the amount of displacement of the guide groove 26 due to the wobbling at each condensing spot position in the following four cases.

[0068]

[Table 1]

In Table 1, in case 1, since the guide groove 26 is not displaced at the position of the central focused spot 4A, D0 = 0 in the equation (1). Focusing spots 5A and 6 before and after the central focusing spot 4A
At the position A, the guide groove 26 is displaced most,
That direction is the opposite direction.

Therefore, in the equation (2), D1 =-
In the equations D and (3), D2 = + D. By substituting each of these and obtaining the tracking error signal TE1 in case 1 from the equation (4), the following equation is obtained. TE1 = A0 · sin (2πX / P) [1-cos {2π (Q + D) / P}] ... (5)

Similarly, FIG. 9 is referred to as case 2. At the position of the central focused spot 4A, the guide groove 26 is displaced most, and in the equation (1), D0 = + D. The guide groove 26 is not displaced at the positions of the front and rear focused spots 5A and 6A. Therefore, in equation (2), D
1 = 0, and in the equation (3), D2 = 0. By substituting these values and obtaining the tracking error signal TE2 in case 2 from the equation (4), the following equation is obtained. TE2 = A0 [sin (2πX / P) {cos (2πD / P) -cos (2πQ / P)}-OF1] (6) where OF1 = cos (2πX / P) sin (2πD / P) ... (6) 7)

As is clear from the above calculation, Case 1
In, the shift amount X of the focused spot is expressed by a sin function, and the offset component is not included. However, in case 2, the cos function for X is included as in equation (7), and this is the offset component.
Moreover, it can be seen that the offset amount depends on the displacement amount D of the guide groove 26.

To summarize the above, in the case where the guide groove 26 of the information recording medium 10 is wobbling, when the differential push-pull method is used, the intervals of the respective focused spots on the surface of the information recording medium are the guide grooves. If it is about a quarter of the wobbling pitch, the tracking offset cannot be completely removed.

Further, there is a problem that the offset amount depends on the wobbling amplitude of the guide groove, and the offset amount generated by the exchange of the information recording medium is different.

On the other hand, the information recording medium 10 having the guide groove and the focused spot 4 in the conventional example described with reference to FIGS.
The arrangement relationship with A to 6A is as shown in FIG. In FIG. 13, the same parts as those in FIGS. 8 and 9 are designated by the same reference numerals, 26 is a guide groove, 27 is a center line, and 28 is a land portion, which are flat.

Further, d is the interval between the respective focused spots 4A to 6A, and FIG. 13 shows the case of d = W / 2. The focused spot 4A is a wobbling guide groove 2
6 is located on the center line 27 of the wobbling, and the two front and rear focus spots 5A and 6A with respect to the center focus spot 4A are in opposite directions to the center line 27 as in FIG. Are offset by a distance equal to.

However, since the focused spots 5A and 6A are at a distance of half the wobbling pitch W from the central focused spot 4A, the guide groove 26 is also located on the center line 27 of the wobbling. Therefore, the tracking error signal obtained by detecting the reflected light of the two front and rear focused spots 5A and 6A as an electric signal and obtaining the subtraction signal thereof correctly corresponds to the tracking shift of the central focused spot 4A.

By the way, the information recording medium 7 is indicated by an arrow X in the figure.
Consider the case of rotation in the direction indicated by. Focus spot 4
B, 5B, and 6B respectively show the focused spots 4A, 5A, and 6A in the state where the information recording medium 10 is rotated, and although the central focused spot 4B is on the center line 27, the guide groove 26 is formed. Is shifted to the upper part of the figure due to the wobbling.

Similarly, the front and rear focused spots 5B,
6B is displaced from the center line 27 by a predetermined amount, but due to the wobbling of the guide groove 26, both of the guide grooves 26 are displaced downward in the drawing in the focused spots 5B and 6B.

Therefore, the front and rear two focused spots 5
The tracking error signal obtained by detecting the reflected light of B and 6B as an electric signal and obtaining the subtraction signal of these is detected as the guide groove 26 is similarly displaced downward in the drawing with respect to the central converging spot 4B. , Central focus spot 4
Correction control is performed to shift B downward in the figure by the same amount as the shift amount.

That is, when viewed from the converging spot 4B, the guide groove 26 is displaced further upward, and there is a problem that the recording pit 25 is defective and the reproduction signal quality is deteriorated due to an increase in tracking displacement.

The invention of claim 1 has been made to solve the above problems, and information can be recorded according to the guide groove, and the guide groove is wobbled at a constant frequency. It is an object of the present invention to provide an optical recording / reproducing device in which tracking offset does not occur even if the differential push-pull method is used.

It is an object of the inventions of claims 2 and 3 to obtain an optical recording / reproducing apparatus capable of simplifying the structure, reducing the cost and accurately detecting a tracking error.

According to the invention of claim 4, the tracking spot does not occur regardless of the wobbling of the guide groove, the central focusing spot can follow the average center line of the guide groove, and stable recording pit formation and An object of the present invention is to obtain an optical recording / reproducing device which can obtain high quality reproduction signal characteristics.

According to a fifth aspect of the present invention, in the information recording medium in which the information can be recorded according to the guide groove and the guide groove is wobbled at a constant frequency, the tracking error detection method by the three-beam method is used. It is an object to obtain an optical recording / reproducing device capable of

It is an object of the present invention to provide an optical recording / reproducing apparatus capable of simplifying the structure and reducing the cost, and capable of accurately detecting a tracking error.

It is an object of the present invention to provide an optical recording / reproducing apparatus capable of obtaining stable recording pits and reproducing signal characteristics of high quality.

[0088]

According to another aspect of the present invention, there is provided an optical recording / reproducing apparatus comprising: a laser beam generating means for generating three laser beams; and an information recording medium having guide grooves wobbled in a predetermined cycle in advance. This information recording medium is condensed and irradiated to form three condensed spots from three laser beams, and the intervals between the condensed spots are set to be an integral multiple of the half pitch of the wobbling, and the central spot A light spot is placed in the guide groove to record or reproduce information, and the other two condensing spots are changed in directions different from each other by approximately ½ of the interval between the guide grooves so that the lands existing between the guide grooves. And a condensing spot forming means arranged on the section.

An optical recording / reproducing apparatus according to the invention of claim 2
The laser beam generating means is composed of a semiconductor laser that emits one laser beam and a diffraction grating.

An optical recording / reproducing apparatus according to the invention of claim 3
The laser beam generating means is a monolithic semiconductor laser array that emits three laser beams from one oscillation region or a hybrid semiconductor laser array that emits one laser beam from each of the three oscillation regions. is there.

An optical recording / reproducing apparatus according to the invention of claim 4
The guide groove is wobbling at 22.05 ± 1 kilohertz so that the information recording medium has a constant linear velocity in the range of 1.2 to 1.4 meters per second, and the intervals between the three converging spots are the respective converging spots. Is about 24 to 35 microns, which corresponds to approximately one half of the wobbling pitch.

An optical recording / reproducing apparatus according to the invention of claim 5 is
A laser beam generating means for generating three laser beams, an information recording medium having a guide groove wobbled in a predetermined cycle in advance, and the recording medium is focused and irradiated to form three focused spots from the three laser beams. In addition, the distance between the focused spots should be an odd multiple of about a quarter of the wobbling pitch in the guide groove, and the central focused spot should be placed on the average center line of the guide groove. A condensing spot forming means is provided in which the light spots are opposed to each other with the central condensing spot sandwiched therebetween, and are arranged at positions displaced from each other by a certain distance in different directions with respect to the center line.

An optical recording / reproducing apparatus according to the invention of claim 6
The laser beam generating means is composed of a semiconductor laser that emits one laser beam and a diffraction grating.

An optical recording / reproducing apparatus according to the invention of claim 7
The laser beam generating means is a monolithic semiconductor laser array that emits three laser beams from one oscillation region or a hybrid semiconductor laser array that emits one laser beam from each of the three oscillation regions. is there.

An optical recording / reproducing apparatus according to the invention of claim 8 is
The guide groove is wobbling at 22.05 ± 1 kilohertz so that the information recording medium has a constant linear velocity in the range of 1.2 to 1.4 meters per second, and the intervals between the three converging spots are the respective converging spots. Is 11 to 18 microns, which corresponds to about a quarter of the wobbling pitch, or 33 to 54 microns, which corresponds to about a third of the wobbling pitch.

[0096]

According to the first aspect of the invention, the three converging spots are formed on the information recording medium having the guide groove in which three laser beams generated by the laser beam generating means are previously wobbled at a constant period by the condensing spot forming means. After forming and irradiating, the interval of each condensing spot is set to an integral multiple of half of the pitch of the wobbling of the guide groove, and the central condensing spot is arranged in the guide groove to record or reproduce information. ..

Further, by changing the other two focused spots in different directions by approximately one half of the spacing between the guide grooves and arranging the spots on the lands existing between the guide grooves, the wobbling of the guide grooves can be improved. Independently, the central focus spot follows the average centerline of the guide groove.

Further, the laser beam generating means in the invention of claim 2 causes one laser beam generated from the semiconductor laser to generate three laser beams by the diffraction grating.

The laser beam generating means in the invention of claim 3 is a monolithic semiconductor laser array,
Emit three laser beams from one oscillation region,
Or with a hybrid type semiconductor laser array,
One laser beam is generated from each of the three oscillation regions to obtain a total of three laser beams.

The guide groove of the information recording medium in the invention of claim 4 is wobbling at 22.05 ± 1 kHz.
Moreover, since the distance between the respective focused spots is set to 24 to 35 microns which corresponds to approximately one half of the wobbling pitch, the central focused spot follows the average center line of the guide groove.

According to the fifth aspect of the present invention, the three converging spots are formed on the information recording medium having the guide grooves, which are previously wobbled at a constant period by the converging spot forming means for the three laser beams generated from the laser beam generating means. Forming and irradiating, the interval of each condensing spot is an odd multiple of approximately one quarter of the pitch of the wobbling of the guide groove, and the central condensing spot is arranged on the average center line of the guide groove. The other two focused spots are sandwiched and face each other, and they are offset from each other by a certain distance with respect to the center line.Therefore, the central focused spot does not depend on the guide ring wobbling. Recording and playback are performed by following the exact center line.

The laser beam generating means in the invention of claim 6 causes one laser beam generated from the semiconductor laser to generate three laser beams by the diffraction grating.

The laser beam generating means in the invention of claim 7 is a monolithic semiconductor laser array,
Emit three laser beams from one oscillation region,
Alternatively, by using a hybrid type laser array, one laser beam is generated from each of the three oscillation regions,
Obtain a total of three laser beams.

The guide groove of the information recording medium in the invention of claim 8 is wobbling at 22.05 ± 1 kilohertz, and each converging spot interval is 11 to 18 μm or a wobbling pitch, which is approximately one half of the wobbling pitch. Since it is 33 to 54 microns, which corresponds to about three quarters, the central focused spot follows the average center line of the guide groove without depending on the wobbling of the guide groove.

[0105]

Embodiments of the optical recording / reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is an optical path diagram showing the configuration of the first embodiment, and the configuration has already been described in the section of “Prior Art”, and the description thereof will be omitted here.

FIGS. 2 and 3 are plan views showing the positional relationship between the information recording medium 10 and the converging spots applied to the present invention, and the interval L between the converging spots is the wobbling pitch of the guide groove 26. Approximately one half of W, that is, L = W / 2
Shows the case.

In FIG. 1, the central converging spot 4A is the guide groove 2.
6 and the center line 27 are aligned with each other. FIG. 2 shows that the guide groove 26 is displaced most from the center line 27 by the rotational movement of the information recording medium 10 and the central light is condensed. The case where the spot 4A is arranged is shown.

Next, the operation will be described. First, FIG.
Assuming that the state is case 3 in Table 1, a tracking error signal in the differential push-pull method will be obtained.

In case 3, since the guide groove 26 is not displaced at the position of the central focused spot 4A, D0 = 0 in the equation (1). Similarly, there is no displacement of the guide groove 26 even at the positions of the front and rear converging spots 5A and 6A. Therefore, in the formula (2), D1 = 0, and in the formula (3), D2 = 0 (see Table 1). ).

By substituting each of these,
From the equation (4), the tracking error signal T in case 3 is obtained.
When E3 is obtained, the following equation is obtained. TE3 = A0 · sin (2πX / P) {1-cos (2πQ / P)} (8)

Similarly, let FIG. 3 be case 4 in Table 1. The guide groove 26 is displaced most at the position of the central focused spot 4A, and in the equation (1), D0 = + D
Becomes The guide groove 26 is also displaced most greatly at the positions of the front and rear focused spots 5A and 6A, and the direction thereof is opposite to the position of the central focused spot 4A.

Therefore, in the equation (2), D1 =-
In the equations D and (3), D2 = -D (see Table 1). By substituting these values and obtaining the tracking error signal TE4 in case 4 from the equation (4), the following equation is obtained. TE4 = A0 [sin (2πX / P) {1-cos (2πQ / P)}-OF2] (9) where OF2 = cos (2πX / P) sin (2πD / P) · {1 + cos (2πQ / P) )} (10).

As is clear from the above calculation, Case 3
In, the shift amount X of the focused spot is expressed by a sin function, and the offset component is not included. Further, in case 4, the cos function for X is included as in Expression (10).

However, the front and rear converging spots 5A and 6A
If the shift amount Q with respect to the central focused spot 4A is half the guide groove pitch P, that is, Q = P / 2, then OF
2 = 0, and the signal TE4 obtained by the equation (9) eventually coincides with the signal TE3 obtained by the equation (8). Therefore, the tracking offset is removed by the differential push-pull method regardless of the wobbling of the guide groove 26.

Next, a second embodiment of the present invention will be described. In the above-described first embodiment, the case where one laser beam is divided into three by the diffraction grating 3 is illustrated, but the same effect can be obtained even if a semiconductor laser array that emits three laser beams is used.

Next, a third embodiment of the present invention will be described. In the above-mentioned first and second embodiments, the distance between the focused spots is set to be approximately one half of the wobbling pitch of the guide groove 26. However, since the wobbling is periodic, the distance between the focused spots is increased. May be an integral multiple of approximately one half of the wobbling pitch.

Next explained is the fourth embodiment of the invention. An information recording medium, such as a recordable CD, in which the guide groove 26 is wobbling at 22.05 ± 1 kilohertz so that the linear velocity is a constant value in the range of 1.2 to 1.4 meters per second is used. In the optical recording / reproducing apparatus, 24 μm to 35 μm, which is approximately one half of the wobbling pitch, is effective as a practical focus spot interval.

Next explained is the fifth embodiment of the invention. The construction of the optical recording / reproducing apparatus of the fifth embodiment is as shown in FIG. 4, and the construction of this FIG.
This is as explained as the conventional example in the section of (2), and the duplicated description here will be omitted.

FIG. 5 is an explanatory view showing the positional relationship between the information recording medium having the guide groove and the focused spots. The focused spot 4A at the center is located on the center line 27 of the wobbling. Similar to the conventional example, the two focused spots 5A and 6A are displaced from the center line 27 by the same distance in opposite directions.

In FIG. 5, the point different from the conventional example shown in FIG. 13 is that the spot distance d between the focused spots 4A, 5A and 6A is approximately one quarter of the wobbling pitch W of the guide groove 26, that is, , Approximately d = P / 4. The spot distance d can be set to an arbitrary value by designing the diffraction grating 3.

Next, the operation of the fifth embodiment will be described. First, let us consider a case where the wobbling guide groove 26 of the focused spot 4A is located exactly on the center line 27 of the wobbling. Since the front and rear focused spots 5A and 6A are located at a distance of approximately a quarter of the wobbling pitch W from the central focused spot 4A, the guide grooves 26 are opposite to each other from the center line 27 due to the wobbling. Is off.

However, the condensing spots 5A and 6A themselves are originally displaced from each other in opposite directions. Therefore,
The tracking error signals obtained by detecting the reflected lights of the two front and rear converging spots 5A and 6A as electric signals and corresponding to these arithmetic signals correctly correspond to the tracking deviation of the central converging spot 4A.

Next, the information recording medium 10 is indicated by an arrow X in FIG.
Consider the case of rotation in the direction. Focused spots 4B, 5
B and 6B respectively show the focused spots 4A, 5A and 6A in the information obtained by rotating the information recording medium 10, and although the central focused spot 4B is on the center line 27, the guide groove 16 has a wobbling ring. Because of this, it shifts to the upper part of the figure.

Similarly, the front and rear focused spots 5B,
6B is displaced from the center line 27 by a predetermined amount, but due to the wobbling of the guide groove 26, in the converging spot 5B, the guide groove 26 is displaced upward in the figure, whereas At the spot 6B, the guide groove 26 is displaced downward in the drawing. That is, the front and rear focused spots 5B, 6
In B, since the guide groove 26 is displaced in the opposite direction, the reflected light of the two front and rear focused spots 5B and 6B is detected as an electric signal, and the tracking error signal obtained as a subtraction signal thereof remains zero. Therefore, the tracking correction control for the central focused spot 4B is not performed.

In this case, the center focused spot 4B is displaced upward in the drawing due to the wobbling of the guide groove 26. However, even if the displacement originally occurs within the wobbling amplitude range, recording is performed. It does not affect the formation of the pit 25 and the quality of the reproduced signal.

Next explained is the sixth embodiment of the invention. FIG. 4 is an optical path diagram of the optical recording / reproducing apparatus of the sixth embodiment. In FIG. 6, the same parts as in FIG. 10 are denoted by the same reference numerals, and the parts different from FIG. 10 are mainly described. ..

As is apparent from comparison of FIG. 4 with FIG. 10, the diffraction grating 7, the collimator lens 2a, the quarter-wave plate 8, the objective lens 9, the information recording medium 10, and the concave lens 2 are shown.
2, the cylindrical lens 23 as an astigmatism lens, the photodetector 24, and the light receiving surfaces 24A, 24B, and 24C are the same as those in FIG. 10, and the parts described below are different from those in FIG. This is a characteristic part.

That is, 29 is three laser beams 30.
The semiconductor laser array emits (solid line), 31 (broken line), and 32 (dashed line). In the sixth embodiment, in contrast to the fifth embodiment in which one laser beam is divided into three by the diffraction grating 7, three laser beams 30, 31,
It goes without saying that the semiconductor laser array 29 that emits 32 is used, and the tracking error detection operation by the three-beam method is the same as that of the fifth embodiment.

Next explained is the seventh embodiment of the invention. In the fifth and sixth embodiments described above, the distance between the focused spots is set to approximately one fourth of the wobbling pitch of the guide groove 26. However, since the wobbling is periodic,
The distance between the respective focused spots may be an odd multiple of about a quarter of the wobbling pitch.

Further, an eighth embodiment of the present invention will be described. An information recording medium, such as a recordable CD, in which the guide groove 26 is wobbling at 22.05 ± 1 kilohertz so that the linear velocity is a constant value in the range of 1.2 to 1.4 meters per second is used. In the optical recording / reproducing apparatus, 11 to 18 μm, which corresponds to approximately a quarter of the wobbling pitch, or 33 to 54 μm, which corresponds to approximately a quarter of the wobbling pitch, is effective as the practical focus spot intervals. ..

[0131]

As described above, according to the first aspect of the present invention, the information recording medium having the guide groove formed by wobbling in a predetermined cycle in advance is irradiated with three converging spots, and at the The focused spots are placed in the guide grooves to record or reproduce information, and the distance between the focused spots is set to be an integer multiple of approximately one half of the guide groove wobbling. Regardless of the occurrence of tracking offset, the central focused spot can follow the average center line of the guide groove, stable recording pits can be formed, and high quality reproduction signal characteristics can be obtained.

According to the invention of claim 2, the laser beam generating means is constituted by the semiconductor laser emitting one laser beam and the diffraction grating, so that the constitution can be simplified, the cost can be reduced, and the accurate tracking error can be detected. Becomes

According to the third aspect of the invention, a monolithic semiconductor laser array emitting three laser beams from one oscillation region or a hybrid semiconductor array emitting one laser beam from each of the three oscillation regions is used. Since the laser beam generating means is configured, there are effects that the configuration can be simplified, the cost can be reduced, and the tracking error can be accurately detected, as in the second aspect of the invention.

According to the fourth aspect of the present invention, the guide groove of the information recording medium is wobbling at 22.05 ± 1 kilohertz, and the intervals of the three converging spots are 11 to 18 microns or 33 to 54 microns. Tracking offset does not occur regardless of the guide groove wobbling, and the central focus spot can follow the average center line of the guide groove, which enables stable formation of recording pits and high-quality reproduction signal characteristics. effective.

According to the fifth aspect of the invention, the information recording medium having the guide groove formed by wobbling in a predetermined cycle is irradiated with three converging spots, and the intervals between the converging spots are the wobbling pitch. Since it is set to an odd multiple of approximately one quarter and the central focused spot is placed on the average center line of the guide groove, the central focused spot does not depend on the guide ring wobbling, It is possible to follow the average center line, and it is possible to obtain stable recording pit formation and high-quality reproduction signal characteristics.

According to the invention of claim 6, since the laser beam generating means is composed of the semiconductor laser for emitting one laser beam and the diffraction grating, the structure can be simplified and the cost can be reduced.

According to the invention of claim 7, the laser beam generating means emits three laser beams from one oscillation region, or a monolithic semiconductor laser array, or emits one laser beam from each of the three oscillation regions. Since it is composed of a hybrid type semiconductor laser array,
A simple structure, cost reduction, and accurate tracking error detection are possible.

According to the eighth aspect of the present invention, the guide groove of the information recording medium is wobbled at 22.05 ± 1 kilohertz and the distance between the three converging spots irradiated on this information recording medium is 11 to 18 microns or Since the thickness is set to 33 to 54 μm, there are effects that stable formation of recording pits and high quality reproduction signal characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is an optical path diagram of a first embodiment of the present invention and a conventional optical recording / reproducing apparatus.

FIG. 2 is a plan view showing a state where a central focused spot is arranged at a position where a wobbling guide groove and a center line of the information recording medium applied to the first embodiment are the same.

FIG. 3 is a plan view showing a state in which a central focused spot is arranged at a position where the center line of the guide groove is displaced most by the rotational movement of the information recording medium.

FIG. 4 is an optical path diagram of an optical recording / reproducing apparatus according to another embodiment of the present invention.

FIG. 5 is a plan view showing an arrangement relationship between a guide groove and a focused spot of an information recording medium applied to another embodiment of the above.

FIG. 6 is a plan view showing a positional relationship between a guide groove and a focused spot of an information recording medium applied to a conventional optical recording / reproducing apparatus.

FIG. 7 is a block diagram showing a configuration of a photodetector and an electric system in a conventional optical recording / reproducing apparatus of the present invention.

FIG. 8 is a plan view showing a wobbling guide groove of an information recording medium applied to a conventional optical recording / reproducing apparatus and a state in which a central focused spot is aligned with a center line.

FIG. 9 is a plan view showing a state in which a central focused spot is arranged at a position where a guide groove, which is wobbled by rotation of an information recording body applied to a conventional optical recording / reproducing apparatus, is most displaced from a center line. It is a figure.

FIG. 10 is an optical path diagram of another conventional optical recording / reproducing apparatus.

11 is a plan view showing a positional relationship between a focused spot and pits on the surface of an information recording medium applied to the optical recording / reproducing apparatus of FIG.

12 is a plan view showing a positional relationship between a focused spot and a pit when a central focused spot on a surface of an information recording medium applied to the optical recording / reproducing apparatus of FIG. 10 has a tracking shift. is there.

13 is a plan view showing an arrangement relationship between a guide groove and a focused spot of an information recording medium applied to the optical recording / reproducing apparatus of FIG.

[Description of Reference Signs] 1 semiconductor laser 2 collimator lens 2a collimator lens 3 diffraction grating 4 0th order diffracted beam 4A focused spot 4B focused spot 5 1st order diffracted beam 5A focused spot 5B focused spot 6 -1st order diffracted beam 6A Focused spot 6B Focused spot 7 Polarization beam splitter 8 Quarter wave plate 9 Objective lens 10 Information recording medium 11 Focusing lens 12 Photodetector 15 Differential amplifier 16 Differential amplifier 17 Differential amplifier 19 Adder 21 Differential Amplifier 22 Concave lens 23 Cylindrical lens 24 Photodetector 25 Pit 26 Guide groove 27 Center line 28 Land part 29 Semiconductor laser array 30 Laser beam 31 Laser beam 32 Laser beam

[Procedure amendment]

[Submission date] January 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0064

[Correction method] Change

[Correction content]

Next, problems will be described with reference to FIGS. As described above, since the linear velocity is constant in the CD, the wobbling pitch W of the guide groove 26 wobbling at 22.05 kHz is 54.4 at a linear velocity of 1.2 m / sec. When the linear velocity is 1.4 meters / second, the value is 63.5 microns.

Claims (8)

[Claims] 1. An information recording medium having a laser beam generating means for generating three laser beams and a guide groove formed in a meandering shape at a predetermined cycle beforehand is condensed and irradiated to linearly collect the three laser beams. An optical spot is formed and the distance between the respective focused spots is an integral multiple of approximately one half of the meandering pitch, and the central focused spot is placed in the guide groove to record or reproduce information. Condensing spot forming means for changing the other two condensing spots in different directions by approximately ½ of the interval between the guide grooves and arranging the condensing spots on the lands existing between the guide grooves, and the information recording medium. The three two-divided photodetectors for respectively entering the respective reflected laser beams from and the tracking error detection means for detecting the tracking error from each difference output from the three two-divided photodetectors. Optical recording / reproducing device equipped. 2. The optical recording / reproducing apparatus according to claim 1, wherein the laser beam generating means comprises a semiconductor laser that emits one laser beam and a diffraction grating. 3. The laser beam generating means is a monolithic semiconductor laser array that emits three laser beams from one oscillation region or a hybrid semiconductor laser array that emits one laser beam from each of the three oscillation regions. The optical recording / reproducing apparatus according to claim 1, wherein 4. The guide groove is serpentine at 22.05 ± 1 kilohertz so that the linear velocity of the information recording medium is a constant value in the range of 1.2 to 1.4 meters per second. 2. The optical recording / reproducing apparatus according to claim 1, wherein the light spot interval is 24 to 35 microns, which corresponds to approximately one half of the meandering. 5. A laser beam generating means for generating three laser beams, and an information recording medium having a guide groove formed by meandering in a predetermined cycle beforehand are focused and radiated to three linearly focused beams. The spots are formed, and the distance between the condensing spots is an odd multiple of approximately a quarter of the meandering pitch, and the central condensing spots are arranged on the average center line of the guide groove. Recording or reproduction is performed, and the other two focused spots are made to face each other with the central focused spot sandwiched therebetween, and they are arranged at positions that are offset from each other by a certain distance in different directions with respect to the center line. Means, a photodetector for individually detecting the two focused spots reflected from the information recording medium, and a tracking error by the three-beam method from the output of the photodetector. An optical recording / reproducing apparatus comprising a tracking error detecting means for detecting. 6. The optical recording / reproducing apparatus according to claim 5, wherein the laser beam generating means comprises a semiconductor laser that emits one laser beam and a diffraction grating. 7. The laser beam generating means is a monolithic semiconductor laser array that emits three laser beams from one oscillation region or a hybrid semiconductor laser array that emits one laser beam from each of the three oscillation regions. 6. The optical recording / reproducing apparatus according to claim 5, wherein 8. The guide groove meanders at 22.05 ± 1 kilohertz so that the information recording medium has a constant linear velocity in the range of 1.2 to 1.4 meters per second, and the above three groups are combined. 6. The optical recording / reproducing according to claim 5, wherein the intervals between the light spots are 11 to 18 microns, which corresponds to about a quarter of the meandering pitch, or 33 to 54 microns, which corresponds to about a third of the meandering pitch. apparatus.