JP2002230808A - Information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording and reproducing device which has a simple and inexpensive circuit constitution, properly controls the speed of revolution of a spindle motor, and effectively prevent the deterioration of characteristics of the recording and reproducing. SOLUTION: The information recording and reproducing device has first detection means 12 and 35 which detect tracking error signals including an offset signal component corresponding to the shift from a prescribed position in the tracking direction of an objective 5 on the basis of the return light from a disk type recording medium 1, and second detection means 15 and 37 which detect only the offset signal on the basis of the return light from the disk type recording medium 1, a tracking error signal, in which the offset signal is removed by a differential arithmetic operation of the outputs from the first and the second detection means, is detected and the driving of the tracking actuator 32 is controlled on the basis of the tracking error signal, and the speed of revolution of the spindle motor 2 is controlled on the basis of the offset signal from the second detection means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for recording and / or reproducing information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art In this type of information recording / reproducing apparatus,
A disk-shaped recording medium (hereinafter, also simply referred to as a disk) is chucked to a spindle of a spindle motor, and the disk is driven to rotate by the spindle motor. In this state, a light beam is applied to the disk from an optical pickup via an objective lens. , Or record or reproduce information.

In such an information recording / reproducing apparatus,
When a disk is rotated by a spindle motor, in addition to the amount of eccentricity of the disk itself, the amount of eccentricity of the disk fluctuates due to a chucking error of the disk with respect to the spindle.
If the amount of eccentricity is large, rotating the disk at high speed increases the frequency of the tracking error signal,
There is a problem that the tracking error of the tracking actuator that drives the objective lens in the tracking direction increases, and the recording / reproducing characteristics deteriorate.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. H11-126419 discloses a focus servo that drives an objective lens in a focus direction so that a light beam is focused on a recording surface of a disk. In the state,
An eccentricity is measured based on a tracking error signal, and when the eccentricity is larger than a predetermined reference value, the rotation speed of the spindle motor is reduced to reduce the amplitude of the tracking error signal. ing.

[0005]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. H11-126419, the amount of eccentricity is measured based on the tracking error signal.
In order to measure the amount of eccentricity accurately,
There is a problem that a large-scale and complicated circuit configuration using a clock per rotation is required, resulting in an increase in cost.

In order to achieve particularly high-speed access, the objective lens is provided on a movable portion movable in the seek direction, and another optical system including a light source and a photodetector for signal detection is provided on a fixed portion. In an information recording / reproducing apparatus that employs an optical system, the movable part is generally driven by a voice coil motor. In this case, however, it is difficult to fix the movable part, and therefore, the amount of eccentricity must be detected with high accuracy. As a result, the rotation speed of the spindle motor cannot be properly controlled, resulting in deterioration of recording / reproducing characteristics.

Accordingly, an object of the present invention made in view of the above point is that a simple and inexpensive circuit configuration can be used to appropriately control the number of revolutions of a spindle motor and effectively prevent deterioration of recording and reproducing characteristics. It is to provide a device.

[0008]

According to the first aspect of the present invention, there is provided an objective lens, and a supporting means for supporting the objective lens so as to be displaceable in a tracking direction across a track of a disk-shaped recording medium; An optical pickup having a tracking actuator that drives the objective lens in a tracking direction; and a spindle motor that rotationally drives the disk-shaped recording medium, wherein the objective lens is rotated while rotating the disk-shaped recording medium with the spindle motor. In the information recording / reproducing apparatus for irradiating the disc-shaped recording medium with a light beam to record or reproduce information, a predetermined position in the tracking direction of the objective lens based on the return light from the disc-shaped recording medium Tracking with offset signal component corresponding to shift from First detection means for detecting an error signal, and second detection means for detecting only the offset signal based on the return light from the disk-shaped recording medium, wherein the first and second detection means Detecting the tracking error signal from which the output of the means is differentially operated and removing the offset signal, controlling the driving of the tracking actuator based on the tracking error signal, and detecting the offset signal from the second detecting means. , The number of rotations of the spindle motor is controlled based on the above.

According to a second aspect of the present invention, in the information recording / reproducing apparatus according to the first aspect, the second detecting means includes a light beam separating means for separating the return light into at least three light beams; In order to receive the at least three light beams separated by the light beam separating means, the light beam is divided by a dividing line parallel to the track direction of the disk-shaped recording medium with a width of about 1/4 of the beam diameter. At least 2
A light detector having two light receiving regions, wherein the at least three light beams are shifted by approximately half a beam in a direction orthogonal to the direction of the track, and are arranged so as to intersect the division line. It is characterized in that it is configured to be incident on the photodetector.

According to a third aspect of the present invention, in the information recording / reproducing apparatus according to the first aspect, the second detecting means adjusts the track direction of the disc-shaped recording medium so as to receive the return light. It has six light receiving regions divided by a parallel dividing line in a direction orthogonal to the direction of the track, and at least the four light receiving regions at the center each have approximately 1/4 width of the beam diameter, In the absence of the shift, the return light is made to enter such that its outline is almost in contact with the dividing lines on both sides of the central four light receiving regions,
It is characterized in that only the offset signal is detected based on the difference between the sum of the outputs of the odd-numbered outputs of the six light receiving regions and the sum of the outputs of the even-numbered outputs.

According to a fourth aspect of the present invention, in the information recording / reproducing apparatus according to the first aspect, the second detecting means includes a dividing line parallel to a track direction of the disk-shaped recording medium and a direction of the track. It has four light receiving areas divided in a direction orthogonal to each other with a width of about 1/4 of the diameter of the return light, and the return light is divided into four light receiving areas without the shift. The light-receiving region is made to be incident so as to be almost in contact with the dividing lines on both sides of the light-receiving region. It is characterized in that it is configured to detect only a signal.

According to a fifth aspect of the present invention, in the information recording / reproducing apparatus according to the first aspect, the disc-shaped recording medium is irradiated with three light beams in a predetermined positional relationship, and
Is provided with photodetectors for respectively receiving return lights of at least two of the three light beams, and each of the photodetectors is separated by a dividing line parallel to the track direction. It is characterized by comprising two divided light receiving regions, and detecting only the offset signal based on the sum of the output differences of the two divided light receiving regions of each photodetector.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an information recording / reproducing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an overall schematic configuration of an information recording / reproducing apparatus as a first embodiment. This information recording / reproducing apparatus employs a separation optical system, and a voice coil motor (VCM) 31 covers a wide area in a radial direction of the disk 1 below a disk 1 which is driven to rotate by a spindle motor (SPM) 2. The movable part 3 is disposed so as to be movable across the movable part. The movable portion 3 includes a reflecting member 4 that reflects light from a fixed portion, which will be described later, an objective lens 5 that condenses the light reflected by the reflecting member 4 on the disk 1, and a microscopic lens in the radial direction. A tracking actuator (TrACT) 32 that drives over the range and a focus actuator 33 that drives the objective lens 5 in the optical axis (focus) direction are provided, and the entire movable section 3 and / or the objective lens 5 are moved in the radial direction of the disk 1. To perform tracking servo by moving to
Focus servo is performed by moving the objective lens 5 in the focus direction. The objective lens 5 is supported by the movable portion 3 via a known elastic support means (not shown) so as to be displaceable in the tracking direction and the focus direction.

On the other hand, a laser diode 7 as a light source,
Collimator lens 8, first beam splitter 9, second
Beam splitter 10, critical angle prism 11, first photodetector 12, grating 13, condenser lens 14,
And a second photodetector 15.

In the information recording / reproducing apparatus shown in FIG. 1, a light beam emitted from a laser diode 7 is converted into a parallel light beam by a collimator lens 8, and then passes through a first beam splitter 9 to be incident on a movable section 3. , The movable part 3
Then, the light is reflected by the reflecting member 4 and focused on the recording layer of the disk 1 by the objective lens 5.

The light reflected by the disc 1 is incident on the first beam splitter 9 of the fixed part 6 via the objective lens 5 and the reflecting member 4, where it is partially reflected and separated from the outward path.

The return light from the disk 1 that has been separated from the outward path by the first beam splitter 9 is incident on a second beam splitter 10 and split in two directions, and one of the split light beams is converted to a critical angle. The light is reflected by the prism surface of the prism 11 and received by the first photodetector 12. The first photodetector 12 has a light receiving area divided into four sections, and detects a focus error signal and a tracking error signal based on the outputs of the first and second photodetectors by a known method.

On the other hand, the other light beam split by the second beam splitter 10 is diffracted by the grating 13 and then condensed by the condensing lens 14 to be condensed by the second light detector 15.
To receive light. The grating 13 includes the second photodetector 1
5 are arranged such that the ± 1st order light is shifted by a half spot in the radial direction of the disc 1 with respect to the 0th order light. Note that the grating 13 is used for the second beam splitter 10.
May be formed directly, or may be formed independently and affixed to the second beam splitter 10.

Here, the zero-order light and the ± first-order light from the grating 13 cause an asymmetrical change in the radial direction as the light beam incident on the disk 1 crosses the groove formed on the disk 1. I have. Therefore, if the spot intensities of the zero-order light and the ± first-order light are made substantially equal, and the second photodetector 15 receives the ± first-order light by half a spot shifted in the radial direction with respect to the zero-order light, As described later, the AC component of the tracking error signal can be substantially canceled.

FIG. 2 is a diagram showing a configuration of the second photodetector 15 shown in FIG. As shown in FIG. 2, the second photodetector 15 has a width of about 1/4 of the spot diameter and
The light receiving regions 15a and 15b are divided into two in the radial direction by dividing lines parallel to the track direction, and a zero-order light spot from the grating 13 (see FIG. 1), +1
The spot of the next light and the spot of the -1st light are shifted by half a spot in the radial direction and are incident so as to intersect with the dividing line of the light receiving regions 15a and 15b. Therefore,
If the difference signal between the outputs of the light receiving areas 15a and 15b is detected,
Only an offset signal generated when the objective lens 5 is shifted from a predetermined position according to the eccentricity of the disk 1 can be detected.

That is, the first photodetector 12 detects a tracking error signal including an offset signal component, and the second photodetector 15 does not detect a tracking error signal. Only the offset signal due to the shift of the lens 5 is detected, and the difference signal between the outputs of the photodetectors is obtained, thereby obtaining a tracking error signal from which the offset signal component has been removed. Note that the condenser lens 14 is not always necessary.

FIG. 3 is a block diagram showing the configuration of the signal processing circuit. As described above, the first photodetector 12 has four
Since the light receiving area is composed of divided light receiving areas, the sum A of the outputs of the two light receiving areas on one side and the output of the two light receiving areas on the other side bordering on a dividing line parallel to the tangential direction. The difference from the sum B is calculated by the differential amplifier 35 to obtain a tracking error signal including an offset signal component due to the shift of the objective lens 5, and the signal is supplied to one input terminal of the differential amplifier 36.

The outputs A 'and B' of the two-divided light receiving areas 15a and 15b of the second photodetector 15 are subjected to differential operation by the differential amplifier 37 to obtain only the offset signal due to the shift of the objective lens 5. And the offset signal is
The gain is adjusted by the GC circuit 38 and supplied to the other input terminal of the differential amplifier 36.

In the differential amplifier 36, a tracking error signal including an offset signal from the differential amplifier 35,
By performing a differential operation on the offset signal from the differential amplifier 37 whose gain has been adjusted by the AGC circuit 38, a tracking error signal from which the offset signal has been removed is obtained, and this tracking error signal is supplied to the TrACT driver 39 so that the TrACT 32 is controlled. Drive, thereby performing tracking servo. For the focus servo, a focus error signal is detected by a known method based on the output of the first photodetector 12, in this case, the critical angle method, and the focus actuator 33 is driven based on the focus error signal. Do it.

The offset signal from the differential amplifier 37 whose gain has been adjusted by the AGC circuit 38 is supplied to the CPU 41. The CPU 41 detects the shift amount of the objective lens 5 from a predetermined position in the tracking direction, that is, the eccentric amount of the disk 1 based on the amplitude of the offset signal, and compares the detected eccentric amount with a preset reference value. ,
The rotational speed of the SPM 2 is controlled via the SPM controller 42 and the SPM driver 43 based on the comparison result. The rotation speed of the SPM 2 is detected by the rotation detector 44 using a clock obtained from a Hall element provided in the SPM 2, for example, and the detected rotation speed is supplied to the SPM controller 42 for feedback control.

FIG. 4 is a flowchart for explaining the rotation speed control operation of the SPM 2 according to the present embodiment. Here, for convenience of explanation, it is assumed that two predetermined rotations, LOW rotation and HIGH rotation, are prepared in advance as the rotation speed of the SPM 2, and one of them is selected to drive the disk 1 by CAV.

First, at the start of driving of the SPM2, C
The PU 41 instructs the SPM controller 42 to perform a LOW rotation to control the SPM 2 to rotate at a predetermined LOW rotation speed (step S1). In this state, a focus error signal is detected and the focus servo is turned ON. The tracking servo is turned on by detecting the tracking error signal from which the offset signal has been removed.
(Step S2).

Thereafter, the CPU 41 detects the amount of eccentricity based on the offset signal (step S3), and compares the detected amount of eccentricity with a preset reference value (step S4). Here, when the amount of eccentricity is less than the reference value, C
The PU 41 instructs the SPM controller 42 to perform a HIGH rotation (step S5).
3 to control the SPM 2 to rotate at a predetermined HIGH rotation speed (step S6). On the other hand, when the eccentric amount is equal to or larger than the reference value in step S4, the LOW rotation is maintained.

According to the present embodiment, for example, TrACT
When the cutoff frequency of 32 is an estimated value of 3.5 KHz and the tracking error is suppressed within 0.1 μm, 160 Hz (9600 rpm) until the eccentric amount is equivalent to 24 μm.
It is possible to increase the rotation speed up to that. In addition, 113 Hz (678) until the eccentric amount exceeds 24 μm and corresponds to 48 μm.
0 rpm) by reducing the rotation speed to 0.1 μm.
tracking error within m.

In the above description, the rotational speed of the SPM 2 is controlled in two stages. However, it is also possible to set a plurality of reference values and control in multiple stages. When the disk 1 is driven by CLV or ZCAV, the innermost circumference of the disk has the highest number of revolutions. Therefore, for example, the disk area is divided into three large areas and the number of rotations increases as the disk area approaches the inner circumference side. You only need to raise it.

Further, the allowable value of the tracking error is 0.
The thickness is not limited to 1 μm and can be changed according to the application. For example, even in the case of a ROM disk or a recording / playback disk,
As shown in FIG. 3, when a read-only command is input from the upper level to the CPU 41, the CPU 41 increases the allowable value of the tracking error from 0.1 μm to 0.2 μm to correspond to the tracking error of 0.2 μm. A high-speed rotation instruction to the SPM controller 42 can be given to rotate the SPM 2 at a higher speed. When a write instruction is input to the CPU 41, the allowable value of the tracking error is reduced from 0.2 μm to 0.1 μm, and control is performed as described above.

Also, when the temperature inside the apparatus rises and the recording conditions deteriorate, the temperature inside the apparatus is detected by a temperature sensor, and when the detected temperature reaches a predetermined reference value, the tracking error is detected in the same manner as described above. Can be dealt with by reducing the rotational speed of the SPM2 by making the allowable value of SPM strict. Similarly, when the track pitch of the disk 1 is narrow and the recording density is high, the tolerance of the tracking error can be made strict and the rotation speed of the SPM 2 can be reduced.

FIGS. 5A and 5B are diagrams showing two modified examples of the second photodetector 15 used in the first embodiment shown in FIG. In the first embodiment shown in FIG. 1, a tracking error signal including an offset signal component is obtained from the output of the first photodetector 12, but as shown in FIG. The light receiving areas 15a and 15b are arranged next to the light receiving areas 15a and 15b so as to receive the left half and the right half of the spots of the ± 1 order light on the photodetector 15 of FIG.
The tracking error signal including the offset signal component can also be obtained by arranging the signals c and 15d and calculating the difference between the outputs of the light receiving regions 15c and 15d.

As shown in FIG. 5B, light receiving areas 15e and 15f are arranged beside the center of the light receiving areas 15a and 15b of the second photodetector 15 where the zero-order light spot is formed. Then, the left and right ends of the zero-order light spot may be received, and the difference between the outputs of the light receiving regions 15e and 15f may be calculated to obtain a tracking error signal including an offset signal component.

FIG. 6 is a diagram for explaining a second embodiment of the information recording / reproducing apparatus according to the present invention. In the second embodiment, a hologram is formed on the second beam splitter 10 instead of the grating 13 in the first embodiment shown in FIG.

As shown in FIG. 6, the second photodetector 15 has six light receiving areas 15g to 15l, and ± first-order lights are arranged and incident on the light receiving areas 15i and 15l, and the zero-order light is received. It arrange | positions so that it may enter over area | regions 15g, 15h, 15j, and 15k.

According to this embodiment, since the offset signal of the objective lens 5 in the tracking direction is obtained by calculating (g + h + i)-(j + k + 1), this offset signal is converted into the CPU 41 as in the first embodiment. To supply S
While controlling the rotation speed of PM2, this offset signal is subtracted from the tracking error signal including the offset signal component obtained based on the output of the first photodetector 12 to obtain a tracking error signal from which the offset signal component has been removed. , Whereby T is transmitted through the TrACT driver 39.
The tracking servo is performed by driving the rACT 32.

Incidentally, instead of forming the hologram on the second beam splitter 10, the condensing lens 14 may have the same hologram effect.

FIG. 7 is a diagram for explaining a third embodiment of the information recording / reproducing apparatus according to the present invention. In the present embodiment, the grating 13 shown in FIG. 1 is removed, and as shown in FIG. 7A, a light receiving portion divided into six in the radial direction by a dividing line parallel to the track direction of the disk is used as a second photodetector as shown in FIG. Using the photodetector 16 having the regions a to f and returning the return light in a state where the objective lens is not shifted, the outer shape line is divided into four dividing lines on both sides of the central four light receiving regions a, b, d, and e;
That is, the dividing lines of the light receiving areas b and c and the light receiving areas e and f
The light is incident so as to be almost in contact with the dividing line.

The principle of detecting a tracking error signal in the present embodiment is as follows. FIG. 7B shows a configuration in which the light receiving regions 15a and 15b of the second photodetector shown in FIG. 5A are each divided into three in the track direction. That is, the light receiving areas 15a and 15b of the second photodetector 15 shown in FIG. 5A have six light receiving areas a, b, c, d, e, and
f, and these areas correspond to the six light receiving areas a, b, c, d, e, and f of the photodetector 16 shown in FIG.

In the photodetector shown in FIG. 7B, the sum of the outputs of the light receiving areas 15b, ie, the light receiving areas a, c, e, is subtracted from the sum of the outputs of the light receiving areas 15a, ie, the light receiving areas b, d, f. Thus, an offset signal is obtained. FIG.
The same calculation is performed in the photodetector 16 shown in FIG.
An offset signal can be obtained by calculating the difference (b + d + f)-(a + c + e) between the sum of the outputs of the odd-numbered light-receiving regions and the sum of the outputs of the even-numbered light-receiving regions. Therefore, the photodetector 16 shown in FIG.
(B) or the photodetector shown in FIG. 5 (a) is functionally equivalent.

Here, since the tracking error signal including the offset signal component is obtained by calculating (a + b + c)-(d + e + f), the above-mentioned offset signal is gain-adjusted and subtracted from this signal to obtain the offset. A tracking error signal from which the signal has been removed can be obtained.

According to the third embodiment, an offset signal and a tracking error signal obtained by removing the offset signal can be obtained from one return light spot without using a beam diffraction means such as the grating 13. Therefore,
The number of parts and the number of adjustment steps can be reduced, the cost can be reduced, and the size can be reduced. Further, since the configuration is simplified, the combination with the focus error signal detection system can be easily performed.

FIG. 8 is a diagram for explaining a fourth embodiment of the information recording / reproducing apparatus according to the present invention. In the present embodiment, instead of the photodetector 16 of FIG. 7A used in the third embodiment, the four-division light detection as shown in FIG. The offset signal is obtained by calculating (b + d)-(a + e) using the device 17. Further, the tracking error signal including the offset signal component is detected based on the output of the first photodetector 12 shown in FIG. 1, as in the first embodiment. The division width of each light receiving region of the photodetector 16 shown in FIG. 7 or the photodetector 17 shown in FIG. 8 may be approximately １ ／ of the diameter of the beam spot, and is not strictly defined.

FIG. 9 is a diagram for explaining a fifth embodiment of the information recording / reproducing apparatus according to the present invention. In the present embodiment, the photodetector 16 in the third embodiment includes a pattern 18a having light receiving regions b, d, and f and a pattern 18b having light receiving regions a, c, and e,
The offset signal is detected by calculating the difference between the outputs of the patterns 18a and 18b. In addition,
The tracking error signal including the offset signal component is
As in the first embodiment, the first photodetector 1 shown in FIG.
2 based on the output.

According to the present embodiment, the offset signal can be obtained by calculating the difference between the outputs of the patterns 18a and 18b, and it is necessary to perform the addition calculation of each light receiving area as in the third embodiment. Since it disappears, quick control becomes possible.

FIG. 10 is a diagram for explaining a sixth embodiment of the information recording / reproducing apparatus according to the present invention. In the present embodiment, the astigmatism is given to the return light from the disk, and FIG.
The optical signal is received by the photodetector 19 shown in FIG. 1, and an offset signal, a tracking error signal from which the offset signal has been removed, and a focus error signal are detected based on the output.

The photodetector 19 has a light receiving area a to an upper half.
f, and the lower half is divided into two light receiving areas g and h. Thus, (gh) / (g + h) or {(a + b + c + g)-(d + e + f + h)} / (a +
b + c + d + e + f + g + h) to detect a tracking error signal including an offset signal component, and {(b + d + f)-(a + c + e)} / (a + b + c +
d + e + f + g + h) to calculate an offset signal, and subtract the offset signal from the tracking error signal including the offset signal component to obtain a tracking error signal from which the offset signal has been removed. The focus error signal is calculated by the astigmatism method as {(a + b + c + h)-(d + e + f + g)} / (a +
b + c + d + e + f + g + h).

FIG. 11 is a diagram for explaining a seventh embodiment of the information recording / reproducing apparatus according to the present invention. In this embodiment, the return light from the disk is converged and divided into two, and one converged light is located in front of the focal plane and the other converged light is located behind the focal plane. 1,20-
2 and an offset signal based on those outputs,
A tracking error signal from which an offset signal component has been removed and a focus error signal are detected.

Each of the photodetectors 20-1 and 20-2 is divided into three by a dividing line orthogonal to the track direction, and a light receiving area at the center of the photodetector 20-2 is received by a dividing line parallel to the track direction. It is divided into six regions a to f. Here, the light receiving areas above and below the photodetector 20-2 are g and h,
The three divided light receiving areas of 1 are i, j, and k.

Thus, {(a + b + c)-(d + e + f)} / (a + b + c +
d + e + f) to detect a tracking error signal including an offset signal component, and {(b + d + f)-(a + c + e)} / (a + b + c +
d + e + f) is calculated to detect an offset signal, and this offset signal is subtracted from the tracking error signal including the offset signal component to obtain a tracking error signal from which the offset signal has been removed. The focus error signal is obtained by the following method using the beam size method: ｛(j + g + h) − (i + k + a + b + c + d + e +
f)｝ / (a + b + c + d + e + f + g + h + i + j +
k) is calculated and detected.

FIG. 12 is a diagram for explaining an eighth embodiment of the information recording / reproducing apparatus according to the present invention. In the present embodiment, the return light from the disk is converged, and half of the converged light is shielded by a knife edge.
1, an offset signal, a tracking error signal from which an offset signal component has been removed, and a focus error signal are detected based on the output.

The photodetector 21 is divided into two by a dividing line parallel to the chord of the spot of the incident convergent light, and the upper half is further divided into six light receiving areas a to f.

Thus, {(a + b + c)-(d + e + f)} / (a + b + c +
d + e + f) to detect a tracking error signal including an offset signal component, and {(b + d + f)-(a + c + e)} / (a + b + c +
d + e + f) is calculated to detect an offset signal, and this offset signal is subtracted from the tracking error signal including the offset signal component to obtain a tracking error signal from which the offset signal has been removed. The focus error signal is calculated by the knife edge method as {(a + b + c + d + e + f) -g} / (a + b + c +
d + e + f + g).

According to the sixth to eighth embodiments described with reference to FIGS. 10 to 12, the first photodetector 12 shown in FIG. 1 becomes unnecessary, so that the number of parts and the number of adjustment steps can be further reduced. Can be done easily and cheaply.

The present invention can be effectively applied not only to the above-mentioned separated type information recording / reproducing apparatus but also to an integrated type information recording / reproducing apparatus. In the case of this integral type, for example, as disclosed in Japanese Patent Application Laid-Open No. 61-94246, three beams having one main beam and two sub beams are formed on a disk-shaped recording medium, The present invention can also be effectively applied to a case where irradiation is performed so as to have a track pitch interval and the interval between the main beam and the sub beam has a half track pitch. In this case, the return light of each beam is received by a photodetector having a light receiving area divided into two by a dividing line parallel to the track direction, and at least one of the sub-beams is received by a photodetector that receives at least one sub-beam. The signal obtained by adjusting the output difference and the output difference signal of the two-part light receiving area of the photodetector that receives the main beam are added to detect only the offset signal, and the SPM rotation speed is controlled based on the offset signal. At the same time, the offset signal is subtracted from the tracking error signal including the offset signal component obtained by the three-beam method to obtain a tracking error signal from which the offset signal component has been removed, and the tracking servo is performed.

Further, as disclosed in Japanese Patent Application Laid-Open No. 7-320287, three beams having one main beam and two sub beams are formed on a disc-shaped recording medium, and the sub beams are arranged at a half track pitch. The present invention can be effectively applied to the case where irradiation is performed at intervals. In this case, the return light of each sub beam is received by a photodetector having a light receiving area divided into two in the same manner as described above, and the output difference of the light receiving area divided into two by each photodetector is added, so that only the offset signal is obtained. Is detected, and the offset signal is used to control the rotational speed of the SPM and perform the tracking servo in the same manner as described above.

[0059]

As described above, according to the present invention, the offset signal due to the shift of the objective lens is detected by using the return light from the disk-shaped recording medium, and the rotation speed of the spindle motor is determined based on the offset signal. Control, the simple and inexpensive circuit configuration enables proper control of the rotation speed of the spindle motor even when the separation optical system is adopted, and the eccentricity of the disk-shaped recording medium itself and the chucking error to the spindle motor The tracking error caused by the eccentricity can be suppressed, and the deterioration of the recording / reproducing characteristics can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall schematic configuration of a first embodiment of an optical pickup device according to the present invention.

FIG. 2 is a diagram showing a configuration of a second photodetector shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of a signal processing circuit according to the first embodiment.

FIG. 4 is a flowchart for explaining the operation.

FIG. 5 is a diagram showing two modified examples of the second photodetector used in the first embodiment.

FIG. 6 is a diagram for explaining a second embodiment of the information recording / reproducing apparatus according to the present invention.

FIG. 7 is a diagram for explaining a third embodiment.

FIG. 8 is a diagram for explaining a fourth embodiment.

FIG. 9 is a diagram for explaining a fifth embodiment.

FIG. 10 is a diagram for explaining a sixth embodiment.

FIG. 11 is a diagram for explaining a seventh embodiment.

FIG. 12 is a view for explaining an eighth embodiment in the same manner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc 2 Spindle motor (SPM) 3 Movable part 4 Reflection member 5 Objective lens 6 Fixed part 7 Laser diode 8 Collimator lens 9 First beam splitter 10 Second beam splitter 11 Critical angle prism 12 First photodetector 13 Grating 14 Condenser lens 15 Second photodetector 31 Voice coil motor (VCM) 32 Tracking actuator (TrACT) 33 Focus actuator 35, 36, 37 Differential amplifier 38 AGC circuit 39 TrACT driver 41 CPU 42 SPM controller 43 SPM driver

Claims (5)

[Claims] 1. An optical pickup comprising: an objective lens; support means for supporting the objective lens so as to be displaceable in a tracking direction across a track of a disk-shaped recording medium; and a tracking actuator for driving the objective lens in the tracking direction. A spindle motor that rotationally drives the disk-shaped recording medium, and irradiates the disk-shaped recording medium with a light beam through the objective lens while rotating the disk-shaped recording medium with the spindle motor, thereby obtaining information. In an information recording / reproducing apparatus for performing recording or reproduction, a tracking error signal including an offset signal component corresponding to a shift from a predetermined position in a tracking direction of the objective lens is detected based on return light from the disk-shaped recording medium. First detecting means, and the disk shape A second detection unit for detecting only the offset signal based on the return light from the recording medium, wherein the offset signal is removed by performing a differential operation on the outputs of the first and second detection units Detecting a tracking error signal and controlling the driving of the tracking actuator based on the tracking error signal;
An information recording / reproducing apparatus configured to control the rotation speed of the spindle motor based on the offset signal from the detecting means. 2. The second detecting means includes: a light beam separating means for separating the return light into at least three light beams; and receiving the at least three light beams separated by the light beam separating means. A photodetector having at least two light receiving areas divided by a dividing line parallel to a track direction of the disk-shaped recording medium with a width of about 1/4 of a beam diameter, The light beam of the present invention is configured to be incident on the photodetector so as to be shifted by approximately half a beam in a direction orthogonal to the direction of the track and to intersect with the division line. Item 2. An information recording / reproducing apparatus according to Item 1. 3. The second detecting means includes: a plurality of six divided by a dividing line parallel to a track direction of the disk-shaped recording medium in a direction orthogonal to the track direction so as to receive the return light; And at least the central four light receiving areas each have a width of about 1/4 of the beam diameter. In the absence of the shift, the return light is shaped such that The light is incident so as to be almost in contact with the dividing lines on both sides of the four light receiving regions, and based on the difference between the sum of the odd-numbered outputs and the sum of the even-numbered outputs of the six light receiving regions. 2. The information recording / reproducing apparatus according to claim 1, wherein the apparatus is configured to detect only the offset signal. 4. The method according to claim 1, wherein the second detecting means divides the disk-shaped recording medium by a dividing line parallel to the track direction and in a direction orthogonal to the track direction with a width of about １ ／ of the diameter of the return light. In this state, the return light is made to enter such that the outer diameter line is almost in contact with the dividing lines on both sides of the four light receiving regions without the shift. 2. The apparatus according to claim 1, wherein only the offset signal is detected based on the difference between the sum of the outputs of the odd-numbered outputs of the four light receiving regions and the sum of the outputs of the even-numbered outputs. Information recording and reproducing device. 5. The disc-shaped recording medium is irradiated with three light beams in a predetermined positional relationship, and the second detecting means is provided with at least two light beams of the three light beams. And a photodetector for receiving the return light of each of the photodetectors. Each of the photodetectors is constituted by a divided light receiving area divided by a dividing line parallel to the track direction. 2. The information recording / reproducing apparatus according to claim 1, wherein only the offset signal is detected based on the sum of the output differences.