JP2788141B2 - Error detection device for optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error detecting apparatus for an optical disk apparatus that generates a tracking error signal, a focus error signal, and the like in accordance with an output from a plurality of divided light receiving units, and more particularly to a return light from a disk. The present invention relates to an error detection device which is capable of electrically correcting the amount of positional deviation between the spot and the light receiving section when the positional deviation occurs.

[0002]

2. Description of the Related Art FIG. 5 is a component layout diagram showing an optical system of a magneto-optical disk drive. The apparatus shown in FIG. 5 is a so-called separation optical system, and is divided into a fixed optical system 1 and a movable optical system 2. The moving optical system 2 is mounted on an optical head, and is driven in a radial direction along a recording surface of the disk by a linear motor indicated by reference numeral M.
The moving optical system 2 has an objective lens 21 facing the recording surface of the magneto-optical disk and a total reflection prism 22 located immediately below the optical axis.

A semiconductor laser 1 provided in a fixed optical system 1
The laser light emitted from 1 passes through the collimator lens 12 to become a parallel light flux, is reflected by the beam splitter 13, is further reflected by the mirror 14 of the galvanometer mirror device, and is sent to the total reflection prism 22 of the moving optical system 2. . Then, the light is reflected by the total reflection prism 22 and condensed on the recording surface of the disk by the objective lens 21 to form a minute spot. The return light from the recording surface of the disc passes through the beam splitter 13 through the objective lens 21, the total reflection prism 22, and the mirror 14. The transmitted light is converged by the condenser lens 15 and separated into three lights B0, B1, and B2 by the polarization splitter 16.

[0004] The polarization separator 16 is composed of, for example, a Wollaston prism, and converts the return light from the disk into lights B1 and B2 for detecting polarization by the Kerr rotation angle.
The light is separated into light B0 for detecting a focus and tracking error signal. The separated light is received by the pin photodiode 17. The pin photodiode 17 has a four-divided light receiving portion 17a and light receiving portions 17b and 17c arranged on both sides thereof. The light B0 separated by the polarization separator 16 is received by a four-part light receiving unit 17a, and a tracking error and a focus error are detected by the light receiving unit 17a. Although not shown in the figure, a member for generating astigmatism such as a cylindrical lens is provided between the beam splitter 13 and the polarization splitter 16 in order to obtain a focus error signal by the astigmatism method. Lights B1 and B2 separated into different polarization components (P-wave component and S-wave component) for detecting a reproduction signal (MO signal) are received by light receiving units 17b and 17c, respectively.

FIG. 6 shows a circuit configuration for detecting a reproduction signal (MO signal) and a tracking error signal.
The arithmetic unit 25 calculates the difference between the amounts of light received by the two light receiving units 17b and 17c, thereby obtaining an MO reproduction signal corresponding to the angular direction of the Kerr rotation angle.

In a tracking error signal detection method called a push-pull method, arithmetic units 26, 27, and 28 respectively receive light outputs Ia1, Ib1 from light-receiving sections 17a of four divided a, b, c, and d. , Ic1, Id1 with (I
a1 + Id1)-(Ib1 + Ic1). FIG. 7 shows the recording surface of the magneto-optical disk. In the MO signal recording area (a), a land 30 as a signal recording surface and grooves 31 formed on both sides of the land 30 are formed. Are formed. 7A shows a state where there is no tracking error in which the spot of the laser beam follows the land 30. FIGS. 7B and 7C show a case where a part of the spot is applied to the groove 31 and a tracking error occurs. It is in the state that it is. As shown in FIG. 6, reflected light from a spot formed on the recording surface of the disc forms an image on the four-divided light receiving portion 17a, and a light receiving spot S is formed. As shown by (b) or (c) in FIG. 7, when the spot is on the groove 31, the shadow S is placed on one of the left and right edges of the light receiving spot S on the light receiving section 17a.
a occurs. Since the output from the arithmetic unit 28 can detect which side the decrease in the amount of received light due to the shadow is,
As a result, a tracking error signal is obtained.

On the basis of the detection of the tracking error signal, the mirror 14 is driven by the galvanometer mirror drive unit 18 about the virtual axis indicated by O in FIG. 5, and the detection light is directed to the recording surface of the disk in the RAD direction ( (T direction in FIG. 5) to correct the tracking error.

The focus error can be detected by the astigmatism method. This is due to the function of the above-mentioned cylindrical lens (not shown). That is, when the spot is focused on the land 30, the four-divided light receiving section 17
Although a substantially circular image (light receiving spot S) is formed on a,
When the focal position is at a deep position or a shallow position with respect to the land 30, the light receiving spot of the light receiving unit 17a has a substantially elliptical shape shown at S1 or S2. Therefore, an arithmetic operation unit different from the arithmetic operation unit shown in FIG.
By performing the operation of (Ic1)-(Ib1 + Id1),
A focus error signal can be detected. Based on the detection of the focus error signal, the moving optical system 2
The objective lens 21 is moved in the direction of the optical axis, and the focus error is corrected.

[0009]

As described above, in an optical disc apparatus in which the tracking error signal and the focus error signal are detected by the four-divided light receiving portion 17a, the positional deviation between the light receiving portion 17a and the light receiving spot S is not changed. This has a great effect on the detection accuracy of the error signal.

[0010] For example, due to the displacement of components constituting the optical system or the inclination of the mirror 14 of the movable mirror device in an unnecessary direction, the distance between the center of the light receiving section 17a and the center of the light receiving spot S in FIG. May occur in the directions shown in FIG. This shift direction corresponds to a shift in the tangential (TAN) direction of the disk recording surface. If there is such a displacement amount δ, the calculation result of the received light amount of each part of the four-divided light receiving unit 17a will be out of order, and the tracking error signal will crosstalk with the focus error signal. As a result, the correction of the focus error caused by moving the objective lens 21 cannot be performed accurately.

The crosstalk will be described using mathematical expressions. As described above, the tracking error signal Te is obtained by (Ia1 + Id1)-(Ib1 + Ic1), and the focus error signal Fe is (Ia1 + Ic1)-(Ib1 + I
d1). Here, assuming that no focus error and no tracking error occur in a state where the light receiving spot S is shifted by δ in the tangential direction as shown in FIG. 8, there is no shadow Sa and the light receiving spot S has a perfect circular shape. . As described above, the tracking error signal Te and the focus error signal Fe at this time are Te = (Ia1 + Id1)-(Ib1 + Ic1) Fe = (Ia1 + Ic1)-(Ib1 + Id1). However, since Ia1 = Ib1 and Ic1 = Id1, both error signals Te and Fe become 0.

Next, no focus error occurs when the light receiving spot S is shifted by δ in the tangential direction, and at this time, a shadow S
It is assumed that a is formed and the light reception output of the left half is reduced by α from the light reception output of the right half. Assuming that the light receiving output of the right half simply increases by α in order to simplify the calculation, the tracking error output Te is as follows: Te = (Ia1 + Id1) (1 + α) − (Ib1 + Ic1) Since Ia1 = Ib1 and Ic1 = Id1, Te = (Ia1 + Id1) .α, which indicates the tracking error amount. However, when the focus error signal Fe is obtained, the following equation is obtained: Fe = {Ia1 (1 + α) + Ic1} − {Ib1 + Id1 (1 + α)} = (Ia1−Id1) · α , And crosstalk occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an error detection device in an optical disk device capable of electrically correcting a shift between a light receiving spot and a light receiving portion as needed.

[0014]

SUMMARY OF THE INVENTION An optical disk error detecting apparatus according to the present invention is a device for detecting an error of detection light applied to a disk.
Morphism return light is detected by the plurality of light receiving portions are focused
In the optical de <br/> disk device to be obtained and the error signal and the tracking error signal, when the detection Hikarisu pot reaches the mirror surface of the disc, the detection light spot based on the received light output from the light receiving portion tangential Detects deviation in direction
Detection section and the detection light spot run on the recording surface of the disc.
When inspecting, the amount of deviation in the tangential direction and
Canceling signal generating means for generating a canceling signal based on the tracking error signal detected by the light receiving unit; and a detection light spot deviating in the tangential direction from the focus error signal based on the canceling signal. To that
And a crosstalk canceling means for canceling the amount of crosstalk caused by the crosstalk.

[0015]

According to the present invention, when the detection light returns from the disk and the light receiving spot of the returning light is deviated from the center of the light receiving portion,
The focus is on the fact that a certain mathematical relationship is established between the shift amount and the crosstalk amount to the focus error signal. In other words, the direction of the return light spot and how much the return light spot is displaced are detected based on the received light output when the spot of the detection light is moved to the mirror surface on the disk, and this displacement amount is calculated by a certain arithmetic expression to cancel out. Calculate the amount. Then, the crosstalk amount included in the focus error signal is canceled by canceling the cancellation amount from the focus error signal, and the focus correction driving device is operated based on the canceled focus error signal.

[0016]

Embodiments of the present invention will be described below. FIG. 1 is a circuit block diagram of an error detection device according to the present invention. The structure of the optical system of the optical disk device is the same as that shown in FIG. The tracking error signal (TE), the shift amount (TAN) of the light receiving spot in the tangential direction, and the focus error signal are obtained by the error signal generating unit 42 using the light receiving output from the four-divided light receiving unit 17a of the pin photodiode 17 in FIG. (FE) is calculated.

FIG. 2 shows a specific circuit configuration of the error signal generator 42. Each of the light receiving portions a, b, c, and d of the four-divided light receiving portion 17a is amplified as a voltage value by a current-voltage conversion circuit and an amplifier circuit (none of which is shown). Is calculated by The output is as follows:

Output from the calculating unit 53 (tracking error signal) TE = (Ia + Id)-(Ib + Ic) Output from the calculating unit 56 (deviation in the tangential direction) TAN = (Ic + Id)-(Ia + Ib) From the calculating unit 59 Output (focus error signal) FE = (Ia + Ic)-(Ib + Id)

The mirror surface detector 43 shown in FIG. 1 detects whether the spot of the detection light has reached the mirror surface of the disk. On the recording surface of the magneto-optical disk shown in FIG. 7, the area is divided into a plurality of parts in the rotational direction, and a recording area (a) for the MO signal is formed in the divided sector. There is a region (b) of the mirror surface without the groove 31. When a spot is located on this mirror surface, the light receiving spot S formed on the light receiving portion 17a
Since there is no shadow due to the groove 31, when the spot moves to this mirror surface, the amount of return light becomes maximum. The mirror surface detection unit 43 calculates the sum of the amount of light received by the light receiving unit 17b and the amount of light received by the light receiving unit 17c for obtaining the MO signal, for example, by a computing unit. This output shows a high value at the position of the mirror surface. Therefore, if the output from the arithmetic unit is detected at a predetermined threshold level, it can be detected that the spot has moved to the mirror surface.

When the mirror surface detector 43 detects that the spot of the detection light has reached the mirror surface of the disk, the cancellation signal generator 44 outputs the output from the arithmetic units 53 and 56 at that time. A cancellation signal for canceling crosstalk is generated based on TE and TAN.

FIG. 3A shows a specific configuration of the canceling signal generator 44. Here, the output from the cancellation signal generation unit 44 is obtained when the detection signal is output from the mirror surface detection unit 43, that is, when the spot of the detection light reaches the mirror surface. Output TE from operation unit 53
Calculates the difference between the left and right of the return light in the four-divided light receiving unit 17a shown in FIG. 4, so that TE when the spot of the detection light reaches the mirror surface is the deviation of the center Os of the light receiving spot S in the tracking direction. It becomes a value corresponding to the quantity y. Similarly, when the spot of the detection light reaches the mirror surface, TAN is the displacement x in the tangential direction of the center Os of the light receiving spot S.
It becomes a value according to. Therefore, the output TE when the spot of the detection light reaches the mirror surface is represented by (y), and the output TAN
Is represented by (x).

In the canceling signal generator 44, the product (x · y) of x and y is obtained by the integrating circuit 61, and a constant A4 is multiplied by a combination of resistors in the constant setting section 62, and A4.x.y) is obtained. Further, the constant x is set to a constant A by the constant setting unit 63.
Multiplied by 6 gives (A6.x). (A4.x.y)
And (A6.x) are sent to the hold circuits 65a and 65b by the ON operation of the analog switches 64a and 64b when the detection output from the mirror surface detection unit 43 is received.
Those values are held. That is, (A4.x
The values of (y) and (A6.x) are updated each time the mirror surface is detected and held by the hold circuits 65a and 65b, or updated and held at a timing such as once for a predetermined rotation of the disk. It is held in the circuits 65a and 65b.

When the detection light spot on the recording surface of the disk is not on the mirror surface, that is, during a normal reproduction operation, the tracking error signal TE obtained at that time by the integration circuit 65 and the hold circuit 65a. The held value of (A6 · x) is integrated,
The value of (A6.x.TE) is calculated. And operation unit 6
6 cancel signal CFE = (A4.x.y) + (A6.
x.TE) is obtained.

Further, in the crosstalk canceling unit 45 shown in FIG. 1, the focus error signal FE at that time is output.
The above-mentioned cancellation signal CFE is subtracted from the above to obtain a corrected focus error signal Fe in which the crosstalk amount has been canceled.

FIG. 3B shows an example of the circuit configuration of the crosstalk canceling unit 45. The subtraction unit 67 subtracts the cancellation signal CFE from the focus error signal FE, and the corrected focus error signal Fe = FE−
CFE is obtained. Further, in the control circuit 46 shown in FIG. 1, the focus error correction control is performed by the corrected focus error signal Fe, and the error signal generation unit 42
The tracking error correction control is performed based on the tracking error signal TE obtained from.

Here, the correction signal CFE = (A4 ·
The procedure for deriving (x.y) + (A6.x.TE) will be described. As shown in FIG. 4, when there are deviation amounts (x) and (y) between the center of the light receiving spot S and the four-divided light receiving unit 17a,
The amount of crosstalk to the focus error signal, that is, the cancellation signal CFE, can be expressed by the following higher-order equation using the deviation amounts (x) and (y) and the tracking error signal TE as variables. CFE = F (x, y, TE) Here, since the shift amounts (x) and (y) are such that the higher-order terms can be ignored, the above equation can be simplified, and CFE = A1 + A2.x + A3.y + A4・ X ・ y + (A5
+ A6.x + A7.y + A8.x.y) .TE.

Each coefficient of this equation will be described. In FIG. 4, when the center of the light receiving spot S is located at the center of the quadrant light receiving portion 17a, that is, when x = 0 and y = 0, CFE = A1 + A5.TE. In this state, no crosstalk occurs even if the tracking error signal TE occurs. That is, since CFE = 0, A1 = A5 = 0.

When the light receiving spot S is in the RAD direction, that is, when x = 0, y ≠ 0, CFE = A1 + A3 ・ y + A7 ・ y ・ TE. In this state, crosstalk does not occur in the same manner as described above, so that A1 = A3 = A7 = 0.

Furthermore, in the CFE = A2 · x + A4 · x · y + (A6 · x + A8 · x · y) · TE, when calculating each coefficient by ^{simulation, A2 = 8.7 × 10 - 3} A4 = -21 A6 = a ^{1 0 - 0.51 A8 = -3.9 ×} 10. Here, since A2 and A8 have smaller values than A4 and A6, these coefficients are omitted. That is, the cancellation amount (the amount corresponding to the crosstalk amount) CFE is CFE = A4.x.y + A6.x.TE.

In the above embodiment, this value is used as a correction amount, and this value is subtracted from the focus error signal, so that the center Os of the light receiving spot S is located at the light receiving portion 17a as shown in FIG.
, The crosstalk to the focus error signal in the case of deviating from the center is canceled out. Therefore, in an actual apparatus, for example, in FIG. 5, the focus actuator operates based on the focus error signal Fe after canceling the crosstalk amount, the objective lens 21 is driven in the optical axis direction, and the focus error correction operation is performed. Is performed.

In the above embodiment, the canceling amount CFE is set by the integrating circuit 61 and the constant setting units 62 and 63 in FIG. 3, but the canceling amount may be obtained by another calculation.

The present invention is not limited to the above embodiment. For example, the means for detecting the mirror surface does not have to be performed based on the amount of light received by the light receiving units 17b and 17c. If an output is obtained by adding all the received light outputs of a, b, c, and d of the light receiving section 17a, the output becomes maximum on the mirror surface, and a mirror surface detection signal can be generated from this output. Further, the time from when the spot passes through the address area to when the spot passes through the mirror surface may be calculated, and the time when the spot passes through the mirror surface may be calculated to be a mirror surface detection signal.

[0033]

As described above, according to the present invention, even if there is a positional shift between the light receiving section and the light receiving spot, this shift can be electrically corrected at any time, and the tracking error signal becomes the focus error signal. No crosstalk will occur. Therefore, it is possible to accurately correct a focus error by moving the objective lens.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an error detection device of an optical disk device according to the present invention;

FIG. 2 is a circuit block diagram showing an example of a specific configuration of an error signal generation unit in the device of FIG. 1;

FIG. 3A is a specific configuration of a cancellation signal generation unit;
(B) is a circuit block diagram illustrating an example of a crosstalk canceling unit,

FIG. 4 is an explanatory diagram showing a positional shift between a light receiving spot and a light receiving unit;

FIG. 5 is an arrangement perspective view showing a configuration of an optical system of the magneto-optical disk device;

FIG. 6 is a circuit block diagram illustrating a configuration of a light receiving unit of the magneto-optical disk device.

FIG. 7 is a plan view showing the structure of the recording surface of the magneto-optical disk;

FIG. 8 is an explanatory view of a light receiving surface of a four-division light receiving unit for describing a conventional problem;

[Explanation of symbols]

 Reference Signs List 17 Pin photodiode 17a Quadrant light receiving unit 41 PD output detecting unit 42 Error signal generating unit 43 Mirror surface detecting unit 44 Canceling signal generating unit 45 Crosstalk amount canceling unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/08-7/095 G11B 21/08-21/10

Claims (1)

(57) [Claims] A plurality of light receiving units detecting a reflected return light of the detection light applied to the disk to detect a focus error;
In the optical disk apparatus where the signal and the tracking error signal is obtained, when the detection Hikarisu pot reaches the mirror surface of the disk, detected based on the received light output from the light receiving portions
A detection method for detecting the amount of displacement of the light spot in the tangential direction.
And the detection light spot scans the recording surface of the disc.
The displacement amount in the tangential direction and the
Canceling signal generating means for generating a canceling signal based on the tracking error signal detected by the optical unit; and detecting light from the focus error signal based on the canceling signal.
An error detecting device for an optical disk device, comprising: a crosstalk amount canceling unit for canceling a crosstalk amount due to a shift of a spot in a tangential direction .