JPH01258234A - Optical disk device - Google Patents

Abstract

PURPOSE:To correct a focus error by respectively calculating dislocation in the (y) direction of an optical axis, the dislocation in an (x) direction, maximum dislocation in the (x) and (y) directions, an error signal and the dislocating component of the optical axis in the error signal from the outputs of the respective dividing parts of a four-dividing optical sensor. CONSTITUTION:The outputs of the respective dividing parts of the four-dividing optical sensor are operated by adding circuits 30 and 31 and a subtracting circuit 37 and the dislocation in the (y) direction of the optical axis is calculated. Similarly, the dislocation in the (x) direction is calculated by adding circuit 32 and 33 and a subtracting circuit 38, the maximum dislocation in the (x) and (y) directions is calculated by adding circuits 34-36 and the error signal is calculated by the adding circuits 34 and 35 and a subtracting circuit 39 respectively. An arithmetic circuit 22 calculates the dislocating component of the optical axis in the error signal from the subtracting circuits 37 and 38 and adding circuit 36 and the outputs of the arithmetic circuits 22 and 39 are supplied to a subtracting circuit 23. Thus, the output signal of the subtracting circuit 23 goes to be only a true error signal component and the focus error is prevented from being generated by the dislocation of the optical axis. Then, the degradation of recording performance and reproducing performance can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc device, and more particularly to an optical disc device that performs focus servo using an astigmatism method.

Conventionally, there have been optical discs for compact disc (CD) W playback (9), and recently, writable and rewritable optical discs have been developed.

In such optical disk recording and playback devices, it is necessary to focus the radar light on the signal surface of the optical disk with high precision, and since the signal surface of the optical disk moves up and down as it rotates, focus servo control is required. is being carried out.

2. Description of the Related Art Conventionally, there has been an astigmatism method for focus servo control.

This astigmatism method takes advantage of the fact that the laser beam that passes through a cylindrical lens becomes a perfect circle at the focal point, becomes a vertically long ellipse in front of the focal point, and becomes a horizontally long ellipse behind the focal point, and divides it into four parts. There are 6 types of sensors that are detected by optical sensors.

For example, if the optical disc is too large, the shape of the light projected onto the four-divided optical sensor divisions a, b, c, and d will be as shown in Figure 8 (
It becomes an ellipse that slopes downward to the right as shown in A), and in the case of a focused point, it becomes an ellipse (
The shape of the light is a perfect circle as shown in B), and if it is too fast, it will become a perfect circle as shown in the same figure (C
), it becomes an ellipse that slopes downward to the left (the major axis is rotated 90 degrees with respect to the ellipse in FIG. 2A).

As a result, when dividing parts a to d output power proportional to the amount of received light, an error signal is obtained by subtracting the difference between the sum of the output voltages of dividing parts a and d from the sum of the output voltages of dividing parts a and c. This allows us to know whether the optical disc is in focus, too close, or too fast, and the focus servo moves the focus position based on the error signal.

Problems to be Solved by the Invention In optical disk devices, changes over time and sudden changes in temperature and humidity can cause shifts in the relative positions of the optical system and the optical sensor.
The optical axis shifts on the optical sensor. For example, Fig. 8 (D) shows a focused point with the optical axis shifted only in the x
It shows a state shifted in the yh direction.

If the optical axis deviates in the x and y force directions at the focused point as shown in FIG. 2(F), the error signal does not become zero and the focus servo moves the focus, causing a focus error, that is, a focus shift. This focus error causes the laser light energy on the signal surface of the optical disc to decrease, resulting in a problem that the recording performance and reproduction performance of the optical disc device deteriorates.

The present invention was made in view of the above points, and focuses on
It is an object of the present invention to provide an optical disc device that corrects errors and prevents deterioration of performance and playback performance.

Means for Solving the Problems The optical disk device of the present invention uses a first calculating means to calculate the y of the optical axis relative to the sensor from the output of one eighth of the four-split optical sensor.
Calculate the deviation in the h direction, calculate the deviation in the x direction of the optical axis with respect to the sensor from the output of each division part using the second calculation means
The third calculation means sifts out the seedlings with the maximum deviation of the optical axis in the X and Y directions with respect to the sensor from the output of each division part, the fourth calculation means sifts out an error signal from the output of each division part, and the fifth The calculation means calculates the optical axis deviation component in the error signal from the outputs of the first to third calculation means, and the sixth dripping means calculates the optical axis deviation component from the outputs of the fourth and fifth calculation means. The focus servo is performed using the error signal of only the focus error with the optical axis deviation component removed.

Further, the variable means varies the amount of light irradiated onto the optical disk according to the optical axis deviation component outputted from the fifth calculating means, and focus servo is performed using the error signal outputted from the fourth calculating means.

Furthermore, the seventh calculation means calculates the deviation rate of the optical axis in the y direction from the outputs of the first and third calculation means, and the eighth calculation means calculates the deviation rate of the optical axis from the outputs of the second and third calculation means. The deviation rate of the axis in the X direction is calculated, and the relative position between the sensor and the optical axis is determined by the first driving means according to the deviation rate in the y7J direction output from the seventh calculation means so that the deviation amount in the y direction is eliminated. and the second driving means moves the relative position between the sensor and the optical axis so that the deviation Φ in the X direction is eliminated according to the deviation rate in the X direction output from the eighth calculation means, and the fourth calculation means Focus servo is performed using the IfI difference signal outputted by.

Operation To explain the principle of the method of the present invention, as shown in Fig. 2, when the optical axis is shifted in the X'jZJ direction, the output levels of the divided parts a, b, c, and d of the optical sensor are , 8. C,
D, and the output levels when there is no deviation in the Xy7J direction are expressed as Ao, So, Go, and Do. In other words, Fig. 2 (A
) corresponds to the output level A, as shown in Figure (B).
The area of the hatched part corresponds to the output level Ao. here,
Deflection X in the X direction corresponding to the area of the shaded part in the same figure (C)
is expressed by the following equation.

X=(B+C)-(A+D)-(1) Furthermore, the maximum deviation ffiXM in the X direction is expressed by the following equation.

XM=A+B+C+D . . . ■Similarly, the deviation ff1Y in the y direction and its maximum value YM are expressed by the following equation.

Y = (A+8)-(C→・D)...■Y
M=A+B+C+D...G4) Using the above deviations fltX, XM, Y, YM, Figure 2 (
In D), the area Xa of the diagonally downwardly shaded portion and the area Ya of the diagonally downwardly shaded portion to the left are expressed by the following equations.

Xa = ((A+8)/2) ・(X/XM)-(
EnYa = ((A+D)/2) ・(Y/YM)
-f3) Using this, the output level A can be expressed approximately as shown in the following equation.

A=Ao −((A+8)/2) ・(X/XM)+
((A-1-D)/2)・(Y/YM)...(10)
Similarly, output levels B, C, and D are expressed as in the following equations.

B=Bo+((A+B)/2)6 (X/XM) ten [(
B→-C)/2)・(Y/YM)...(11)C=G
o + ((C+D)/2) ・(X/XM >-
((B+C)/2) ・(Y/YM)...(12
)D=Do −((C4−D)/2) ・(X/X
M) - ((A+D)/2) ・ (Y/YM)...
・(13) Here, the error signal of the focus error is (
A+C) −(B+D)r given, Koreni (1o) ~
By substituting equation (13), the following equation is obtained.

(A+C)-(B+D)=(Ao+Co)-(Booo)-(A+B
-C-D)・(X/XM) + (A-ID-B-C)・(Y/YM)...(14
) From this, the following formula is given.

(A→C)−, ([300)=(Ao +Co)−(Bo+Do)−2−X−
Y/(A+8-+-C10) (15) The first term on the right side of equation (15) is the true error signal component, and the second term is the optical axis deviation component.

In the present invention, since the focus servo is performed by correcting the focus error by obtaining the error signal obtained by removing the second term on the left side of equation (15) using the sixth calculation means, deterioration of recording performance and playback performance is avoided. Prevented.

In addition, by performing focus/speed control using the Muff signal expressed by equation (15) and varying the amount of laser light using a variable means, focus errors can be corrected, thereby preventing deterioration of recording performance and playback performance. .

In addition, the relative IQ position between the sender and the optical axis is moved to eliminate the deviation of the optical axis in the y direction and the
Errors are corrected, thereby preventing deterioration of recording performance and reproduction performance.

Example FIG. 1 shows a block diagram of a first embodiment of the system of the present invention.

In the figure, 10 is an optical disk, which is rotated by a motor 11. The laser light output from the laser diode 12 is converted into a parallel beam by a collimating lens 13, and is then converted into a parallel beam by a beam splitter 14. The light is guided through the tracking mirror 15 to the objective lens 16 and converged onto the signal surface of the optical disc 10, thereby recording and reproducing the signal. The reflected light from the optical disc 10 is reflected by the objective lens 16. Tracking mirror 15. The reflected light is guided to a beam splitter 17 through a beam splitter 14, and most of the reflected light is guided to an optical sender 18 for signal reproduction. Also, part of the reflected light is reflected by mirror 1.
9 through the cylindrical lens 29.
It is guided to a 4-split optical sensor 20 for servo.

The outputs A, B, C, and D of the divided parts a, b, c, and d of the 4-split optical sensor +J20 are supplied to an arithmetic circuit 21, and the optical axis is An error signal is obtained by removing the deviation component, and this error signal is supplied to the drive coil 25 through the amplifier 24, whereby the objective lens 16 is moved in a direction in which the laser beam is converged on the signal surface of the optical disk 10.

FIG. 3 shows a circuit diagram of the v4p circuit 21,22 described above.

In the figure, the arithmetic circuit 21 is composed of addition circuits 30-35 and subtraction circuits 36-39. The addition circuit 30 adds the output levels A and B of the divided parts a and b of the 4-divided sensor 20, and outputs a signal A+8.

The addition circuit 31 adds up the output levels C and D of the division parts c and d, and outputs a signal C+D. Similarly, point addition circuits 32 to 35
Add output levels A to D of senders a to C, respectively, and receive signals @B+C, A+D, and A+C.

Output each of B+D.

The subtraction circuit 7 subtracts the output signal A+B of the addition circuit 30 and the output signal C+O of the addition circuit 31 to obtain a signal (A+8).
−(C+D), that is, a signal Y representing the amount of deviation Y shown in equation 0
Output. The subtraction circuit 8 calculates yA from the output signals of the addition circuits 32 and 33 and outputs a signal representing the deviation ff1X shown in equation 0). Similarly, the point addition circuit 36 is connected to the addition circuit 34.
35 output signals are added to output a signal (A+B+C+D) representing the Xa1 or Yal according to equation (4) or (4). The subtraction circuit 39 subtracts the output signals of the addition/falsification circuits 34 and 35 to obtain an error signal (A+C)-(B) shown in equation (15).
+D) is output.

Here, the point addition circuits 30.31. The subtraction n circuit 37 constitutes the first arithmetic means, and the addition sieving circuit 32,33° reduction n゛ circuit 38
constitutes a second arithmetic means, and addition->circuits 34 to 36 constitute a third arithmetic means.
constitutes the @nose means, and the opening circuits 34, 35. Reduction circuit 3
9 constitutes one stage of fourth operation.

The performance circuit 22, which is the fifth @p means, is the performance reduction circuit 37.3.
8 and the output signal X of the adder circuit 36, respectively.

Y, (A+B+C+D), that is, the signal (2.
Outputs X - Y/ (A+B+C+D)). The output signals of the arithmetic circuit 22 and the arithmetic circuit 39 are connected to the terminal 40.4.
1. The reduction circuit 23 of FIG. 1, which is the sixth calculation means,
supplied to

As a result, the output signal of the aperture reduction circuit 23 becomes only the true error signal component expressed by the first term of equation (15), and it is possible to prevent focus errors due to optical axis deviation. Therefore, deterioration of the recording performance and reproduction performance of the optical disc device can be prevented.

FIG. 4 shows a block diagram of a second embodiment of the system of the present invention.

In the figure, the same parts as in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 4, the signal expressed by equation (15) output from the arithmetic circuit 21 from the terminal 41 is supplied as is to the amplifier 24 for focus/boosting.

Therefore, the same focal point shift as in the prior art occurs, but a signal representing the optical axis shift component output from the aperture circuit 22 from the terminal 40 is supplied to the laser diode drive circuit 50, which is a variable means. The laser diode driving circuit 50 increases the laser light m by using the driving current of the culm laser diode 12, which has the absolute value of the output signal of the arithmetic circuit 22, which is the optical axis deviation component, as the absolute value. As a result, the laser light energy on the signal surface of the optical disc 10 increases to compensate for the focus error, and it is possible to prevent deterioration of recording performance, playback performance, and performance.

FIG. 5 shows a block diagram of a third embodiment of the system of the present invention.

In this figure, the same parts as in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

In FIG. 5, in place of the arithmetic circuit 22, arithmetic circuits 26a and 26b, which are seventh and eighth arithmetic means, are provided. As shown in FIG. 6, the arithmetic circuit 26a generates a signal N Y / Y M representing the deviation rate in the y direction from the signal Y and the signal (A + B -1 - C -1 - D) and outputs it from the terminal 42. Then, the intoxication circuit 26 b &, is connected to the signal X and the signal (A
+B+C+D) and a signal X representing the deviation rate in the X direction.
/XM is generated and output from the terminal 43.

Signals Y/YM and X/XM respectively C first. The signal is supplied to drive coils 27a and 27b, which are second drive means, so that the mirror 19 rotates to direct the optical axis of the reflected light to the signal Y/Y.
the y direction of the four-part sensor 20 according to M, X/XM, respectively;
The optical axis is moved in each of the X directions to compensate for the deviation of the optical axis relative to +120.

Further, as a modification of this example, as shown in FIG.
YM, X/XM each 1st. It is supplied to each of the drive coils 28a and 28b which are the second drive means, and the 4-split sensor 20
It is also possible to compensate for the deviation of the optical axis with respect to the sensor 20 by moving the optical axis in both the y direction and the x direction.

Effects of the Invention As described above, according to the optical disc device of the present invention, it is possible to correct focus errors caused by misalignment of the optical axis with respect to the sensor, and prevent deterioration of recording performance and playback performance.
It is extremely useful in practice.

[Brief explanation of the drawing]

1, 4, 5, and 7 are block diagrams of each embodiment of the system of the present invention, FIG. 2 is a diagram for explaining the present invention in detail, and FIG. 3 is a diagram similar to that of FIG. 1. 6 is a circuit diagram of a partial circuit of FIG. 5, and FIG. 8 is a diagram for explaining the deviation of the optical axis. 12... Laser diode, 20... 4-split optical sensor, 21.22, 26a, 26b-... Arithmetic circuit, 23
... reduction circuit, °27a, 27b, 28a. 28b... Drive coil, 29... Cylindrical lens. Figure 2

Claims (3)

[Claims] (1) In an optical disc device that performs focus servo using an astigmatism method by projecting reflected light from an optical disc onto a four-split optical sensor through a cylindrical lens, and obtaining a focus error error signal from the output of each split part of the sensor. , a first calculating means that calculates the amount of deviation of the optical axis in the y-direction from the sensor from the output of each of the dividing sections, and a second calculation means that calculates the amount of deviation of the optical axis in the x-direction of the sensor from the output of each of the dividing sections.
a third calculating means for calculating the maximum deviation of the optical axis in the x and y directions of the optical axis with respect to the sensor from the output of each dividing section; and a third calculating means for calculating the error signal from the output of each dividing section. a fifth calculating means for calculating an optical axis deviation component in the error signal from the outputs of the first to third calculating means; and a sixth calculation means for calculating an error signal of only the focus error with the axis deviation component removed, and performing focus servo using the error signal of only the focus error with the optical axis deviation component removed. An optical disc device characterized by: (2) In an optical disc device that performs focus servo using an astigmatism method by projecting reflected light from an optical disc onto a four-split optical sensor through a cylindrical lens and obtaining a focus error error signal from the output of each split part of the sensor. , a first calculating means that calculates the amount of deviation of the optical axis in the y-direction from the sensor from the output of each of the dividing sections, and a second calculation means that calculates the amount of deviation of the optical axis in the x-direction of the sensor from the output of each of the dividing sections.
a third calculating means for calculating the maximum deviation of the optical axis in the x and y directions of the optical axis with respect to the sensor from the output of each dividing section; and a third calculating means for calculating the error signal from the output of each dividing section. 4, a fifth calculation means for calculating an optical axis deviation component in the error signal from the outputs of the first to third calculation means; and an optical axis deviation output from the fifth calculation means. An optical disc device comprising variable means for varying the amount of laser light irradiated onto the optical disc according to the component, and performing focus servo using an error signal output from the fourth calculation means. (3) In an optical disc device that performs focus servo using an astigmatism method by projecting reflected light from an optical disc onto a four-split optical sensor through a cylindrical lens, and obtaining a focus error error signal from the output of each division of the sensor. , a first calculating means that calculates the amount of deviation of the optical axis in the y-direction from the sensor from the output of each of the dividing sections, and a second calculation means that calculates the amount of deviation of the optical axis in the x-direction of the sensor from the output of each of the dividing sections.
a third calculating means for calculating the maximum deviation of the optical axis in the x and y directions of the optical axis with respect to the sensor from the output of each dividing section; and a third calculating means for calculating the error signal from the output of each dividing section. 4 calculation means; seventh calculation means for calculating the deviation rate of the optical axis in the y direction from the outputs of the first to third calculation means; Eighth step to calculate the deviation rate in the x direction of
and a first driving means for moving the relative position of the sensor and the optical axis so that the amount of deviation in the y direction is eliminated in accordance with the deviation rate in the y direction output from the seventh calculation means. , a second driving means for moving the relative position of the sensor and the optical axis so that the amount of deviation in the x direction is eliminated according to the deviation rate in the x direction outputted by the eighth calculation means, An optical disc device characterized in that focus servo is performed using an error signal output from the fourth calculation means.