JPH06162520A - Optical pickup device - Google Patents

Abstract

PURPOSE:To eliminate focusing errors by providing a means for detecting focusing errors, which are caused by tilting a deflecting means for tracking control, and thereby controlling a focus adjusting means. CONSTITUTION:The deflecting means 30 is arranged being fixed between an optical block 20 and an uniaxial actuator 40. By a galvanomirror 31 constituting the deflecting means 30, the optical path of a laser beam is changed at an angle of 90 deg. and guided to the uniaxial actuator 40 ; and the galvanomirror is rotatable left and right over a prescribed range + or -theta around the bottom center part of the galvanomirror 31 which is erected so as to perform tracking adjustments. Also, in this case, a focus adjusting circuit 70 is constructed as illustrated, thereby the focus adjusting means 60 is deflected in the direction of either up or clown and the focusing error is cancelled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device using a uniaxial actuator.

[0002]

2. Description of the Related Art In an optical disc device such as a compact disc or a magneto-optical disc, an optical pickup device usually has a biaxial actuator structure. The biaxial actuator is configured so that the two axes of tracking and focus can be adjusted independently of each other.However, since the structure of this biaxial configuration is complicated, it is heavy and the response characteristics are not so good, so high speed is achieved. It is not suitable for computer use that requires a search.

In recent years, an optical disk device using a uniaxial actuator has been developed as a device for realizing high-speed search. The uniaxial actuator slides this in the radial direction (radial direction) of the optical disk to perform rough adjustment of tracking. The fine adjustment of tracking is performed by the deflecting means for changing the optical path. The deflecting means has a separate structure from the uniaxial actuator, and a galvanometer mirror or the like is generally used as the deflecting means. The uniaxial actuator includes means for focus adjustment.

When the actuator has a single-axis structure as described above, the actuator itself can be made small and lightweight, which is suitable for high-speed retrieval.

[0005]

In order to move the uniaxial actuator in the radial direction, the uniaxial actuator is usually provided with a plurality of bearings, for example, ball bearings. Since the uniaxial actuator is a mechanism that moves along the slide rod, there are problems that not only the frequency characteristics at the time of high speed search can be made too fast, but also the wear of the ball bearing becomes severe at the time of high speed search.

In order to improve this, it is conceivable to control the deflection rotation angle of the deflection means so as to largely swing and reduce the slide amount of the uniaxial actuator accordingly.

However, this causes a new problem that the defocus phenomenon becomes conspicuous due to the deflection rotation angle and the data on the optical disk cannot be reproduced accurately. FIG.
Is a characteristic diagram showing the relationship between the deflection rotation angle (rotation angle) θ of the galvano mirror which is the deflection means and the defocus,
A curve 81 shows the relationship between the rotation angle θ and the defocus when the light receiving element functioning as a photodetector arranged on the return path of the beam light is correctly attached at a predetermined position. When the light receiving element is mounted in the correct position, even if the galvano mirror is rotated to the maximum range, defocusing does not occur much.

If the light receiving element is slightly deviated from the specified position, defocus occurs as cannot be ignored as shown by a curve 82. The figure is a characteristic diagram when it is arranged with a deviation of 5 μm from the specified position.

When the galvanometer mirror rotates when the optical disk has surface deviation, the objective lens cannot follow the surface deviation due to the focus error signal. FIG. 14 shows such a situation. A curve 83 shows the amount of focus error with respect to the surface deviation of the disc when the rotation angle θ of the galvano mirror is 0, and a curve 84 shows the amount of the focus error of the disc when the carbano mirror is rotated by θa. It shows the amount of focus error for surface blur. That is, as shown by the curve 83, the rotation angle θ of the galvanometer mirror
When is 0, the surface deviation can be reduced to 0 μm by controlling the focus error to 0 V.
When the galvano mirror rotates by θa as shown in 4, even if the focus error is controlled to be 0 V, the surface runout is 0
It cannot be made to be μm, resulting in surface deviation of x μm.

Therefore, the present invention has solved the above-mentioned conventional problems, and it is possible to eliminate the defocus that occurs when the galvanomirror is rotationally driven, and to minimize the movement amount of the uniaxial actuator. The present invention proposes an optical disk device in which the consumption of the uniaxial actuator is reduced.

[0011]

In order to solve the above-mentioned problems, in the present invention, the light from the light emitting means is guided into the objective lens provided in the uniaxial actuator by changing its optical path by the deflecting means. In an optical disc apparatus which reproduces at least data while irradiating the optical disc with light from an objective lens, a focus error detecting unit which is generated by tilting the deflecting unit for tracking control is provided. The focus error is removed by controlling the focus adjusting means to which the objective lens is attached by the output of the means.

[0012]

In the example shown in FIG. 1, the photodetector 27 is used as the focus error detecting means. Photo detector 27
Is also a photodetector for obtaining a reproduction signal from the optical disk, and normally, the signals obtained in the four divided light receiving elements a to d are appropriately calculated to reproduce the signal from the optical disk, or a focus error signal. Are generated.

In order to cancel the focus error generated by rotating the galvanometer mirror as shown in FIG. 14, this focus error component FB may be returned to the focus adjusting means 60 (FIG. 1) as a focus bias signal.

The radial push-pull signal, which is a signal obtained by changing the calculation contents of the signals of the light receiving elements a to d, is obtained as a signal proportional to the rotation angle of the galvano mirror as shown in FIG. The push-pull signal is also associated with the focus error component FB.

Therefore, the defocus state caused by the rotation of the galvanometer mirror can be completely removed by simply selecting the input / output relationship of the radial push-pull signal and feeding it back to the focus adjusting means 60.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of an optical disk device according to the present invention will be described in detail with reference to the drawings.

First, an outline of an optical disk device using a uniaxial actuator to which the present invention can be applied will be described in detail with reference to FIG.

The optical disk device 10 shown in FIG. 3 is a case where a laser is used for writing and reading data to and from the optical disk 1. Therefore, the optical disk device 10 has an optical block 20, a galvanometer mirror 31 as a deflecting means 30, and It is composed of a uniaxial actuator 40. 2 is a spindle motor.

The optical block 20 contains a semiconductor laser (LD) 21 as a light emitting means, and the laser light emitted from this is sent out of the block through a collimator lens 22 and a beam splitter 23. A light receiving element 27 functioning as a light detecting means (light receiving means PD) is provided in the light block, and laser light returned through the beam splitter 23 (light having undergone the magneto-optical Kerr effect by the optical disk 1).
Is received by the Wollaston prism 25, the convex lens 28 and the cylindrical lens 26.

The deflecting means 30 is fixedly arranged between the optical block 20 and the uniaxial actuator 40. The galvanometer mirror 31 that constitutes the deflecting means 30 changes the optical path of the laser light by 90 ° and guides it to the uniaxial actuator 40.
The galvano mirror 31 is erected so that tracking adjustment (including fine adjustment) can be performed.

The galvano mirror 31 has a rotating configuration.
A leaf spring 32 is attached to the plate spring 32, and the leaf spring 32 is biased in a predetermined direction by an electromagnetic biasing means (not shown) to impart rotation to the galvanometer mirror 31.

The uniaxial actuator 40 has a pair of plate-shaped yokes 41, 42 arranged at a predetermined distance, and slide rods 44, 45 are attached to predetermined positions inside the yoke pieces 41a, 42a facing inward. Fixed.

A slider 50, which is the basic construction of the uniaxial actuator 40, is arranged between the pair of yoke pieces 41a, 42a. As shown in FIG. 4, the slider 50 has a frame body 50A having a rectangular cross section, and in this example, four slide bars 44 and 45 are sandwiched between the frame bodies 50A on the upper surface side as shown in FIG. The ball bearing 51 is attached with two ball bearings 52 on the lower surface side. With this configuration, the slider 50 itself is slidably attached to the yokes 41 and 42.

A focus adjusting means 60 is arranged on one end side of the slider 50. As shown in FIG. 5, an objective lens 61 is attached to the central portion of the upper surface of a hollow rectangular parallelepiped 66 that serves as a frame, and a triangular mirror raising mirror 62 is fixed inside the rectangular parallelepiped 66 directly below the objective lens 61.

The drive coils 63 are wound around the left and right ends on the outer side of the rectangular parallelepiped 66, and the pair of leaf springs 6 are provided at the upper and lower central portions.
4,65 are attached. The pair of leaf springs 64 and 65 are fixed to one end of the slider 50 shown in FIG. Depending on the amount and direction of energization of the drive coil 63, the leaf spring 64,
65 is biased in either the upper or lower direction. The upward bias is a direction toward the optical disc 1.

As shown in FIGS. 3 and 4, the slider 50 has a loop passing between the yoke pieces 41a and 42a and the gap 46 so as to rotate around the outside of the frame 50A and the driving coil 5a.
5 is wrapped around. A plate-shaped magnet 47 is provided inside the gap 46 and inside the other yoke pieces 41b and 42b.
Has been attached.

When the drive coil 55 is energized with the above-mentioned structure, the slider 50 is moved to the slide rod 4.
Move along 4,45. Although one of the bearings 52 is supported by a leaf spring (not shown), the slider 5
0 is in contact with the slide rods 44 and 45 with proper pressure contact force without play.

FIG. 6 is a diagram showing how the beam light deviates and returns according to the rotation angle θ of the galvano mirror 31, and the distance from the galvano mirror 31 to the objective lens 61 is l and the focal length of the objective lens 61 is When f is set,
The returning beam light is incident with a shift of approximately Δ = 2 (lf) θ.

As a result, the incident spot position on the photodetector 27 is displaced by δ as shown in FIG. That is, when the photodetector 27 is mounted at the proper position, the position shown in FIG.
On the other hand, when the beam spot is located at the beam spot position, the beam spot is also displaced by p as shown in FIG. When the galvanometer mirror 31 rotates in this state, the beam spot is further shifted by δ as shown in FIG. Therefore, if this deviation δ can be detected, the rotation angle θ of the galvanometer mirror 31
Has been detected.

Since the photodetector 27 is divided into four parts as shown in FIG. 8, it is possible to obtain a signal suitable for the purpose by appropriately combining the detection signals of the light receiving elements a to d. For example, it is well known that the focus error signal FE can be obtained by the calculation of FE = (a + d)-(b + c) by the astigmatism method.

Originally, the variation in the axial direction of the optical disk 1 appears as the variation in the vertical direction shown in FIG.
When the cylindrical lens 26 is placed in the optical block 20 shown in FIG. 1, fluctuations in the radial direction appear as fluctuations in the radial direction. Therefore, the push-pull signal RPP in the radial direction becomes RPP = (a + c)-(b + d).

It has been confirmed that the relationship between the push-pull signal RPP and the rotation angle θ of the galvanometer mirror 31 is as shown in FIG. As is clear from FIG. 2, the push-pull signal RPP changes depending on the rotation angle θ.

Further, it is confirmed from FIG. 13 that defocusing due to the rotation angle θ occurs, and it can be estimated from FIG. 13 that the defocus amount, that is, the focus error amount is proportional to the rotation angle θ. θa
When the focus error at the time is the curve 84 of FIG. 14, a conversion system that obtains the focus bias signal FBa shown in FIG. 14 by the push-pull signal RPPa at this time is placed, and the focus bias signal FB is focused. When supplied to the adjusting means 60, the focus adjusting means 60 operates so as to eliminate the focus error. That is, as shown in FIG. 13, the rotation angle and defocus are substantially proportional, and as shown in FIG. 15, since the rotation angle and push-pull signal RPP are proportional, the push-pull signal RPP and defocus are proportional. There is. Therefore, the push-pull signal RPP [(a + b)-
A focus bias signal is obtained as a value obtained by multiplying (c + d)] by a constant k, and thereby focus adjustment is performed.

Therefore, in the present invention, the focus adjusting circuit 70 is constructed as shown in FIG. The detection signals a to d from the common photodetector 27 are the first signal detector 7
A focus error signal FE is generated from this signal and is subjected to appropriate gain adjustment by an operational amplifier (op amp) 73, and then is supplied to the focus adjusting means 60 via the phase compensator 74 and the driver 75. Specifically, it is supplied to the drive coil 63 shown in FIG.

As a result, the focus adjusting means 60 is biased to either the upper or lower direction, and the focus error is canceled.

In the present invention, a second signal detector 71 is further provided for this control system, and the push-pull signal RPP described above is generated here. Second signal detector 71
Incorporates the level conversion system described above, and push-pull signal R
PP is generated, and its level is converted so as to satisfy the above-mentioned relation, and then input to the other terminal of the operational amplifier 73. Therefore, this push-pull signal RP
The focus bias signal FB corresponding to P is also adjusted so as to eliminate the focus error.

Since the focus error is canceled even when the galvanometer mirror 31 is rotated, the rotation angle θ of the galvanometer mirror 31 can be made larger than in the conventional case.
As a result, tracking adjustment can be performed quickly even if the movement amount of the uniaxial actuator 40 is reduced, and as a result, high-speed search can be performed.

FIG. 9 and subsequent figures show other examples of the present invention. In the above-described embodiment, the rotation angle of the galvanometer mirror 31 is set to the photodetector 2.
It is detected by the push-pull signal RPP output from the No. 7, but in the examples described in FIG. 9 and thereafter, the angle sensor is provided and the rotation angle θ of the galvano mirror 31 is directly detected.

Therefore, as shown in FIG. 10, an angle sensor 90 is provided at a predetermined position on the front side of the galvanometer mirror 31. The angle sensor 90 includes a light emitting element 91 and a light receiving element 92 as shown in FIG. 11, and the light emitting element 91 and the light receiving element 92 are embedded in a transparent resin 93.

A laser diode, an LED or the like is used as the light emitting element 91, and the light receiving element 92 using a photodiode or the like is divided into two as shown in FIG.
The position of the beam spot incident on each of the light receiving elements e and f is located at the center when the rotation angle θ of the galvanometer mirror 31 is zero (A in the same figure), but when it is swung to either one, the B or B in the figure is used. As in C, the incident light is shifted from the center.

As a result, it is possible to detect the magnitude of the rotation angle of the galvanometer mirror 31 from the magnitude and polarity of the difference between the detection signals of the light receiving elements e and f.

Therefore, as shown in FIG. 9, a focus adjusting circuit 70 is constructed. The structure is basically the same as the structure shown in FIG. In this example, the output of the light receiving element 92 is supplied to the third signal detector 93, the same conversion processing as that of the second signal detector 71 of FIG. 1 is performed, and the output thereof is used as the focus bias signal FB as the operational amplifier 73. The focus error generated by the rotation of the galvanometer mirror 31 can be canceled by this configuration as in FIG.

[0043]

As described above, according to the present invention, the optical disc apparatus having the uniaxial actuator is provided with the focus error detecting means generated by tilting the deflecting means for tracking control, and the objective lens is output from the focus error detecting means. The focus error is removed by controlling the focus adjusting means to which is attached.

According to this, it is possible to cancel the focus error due to the driving of the galvano mirror while making the most of the characteristics of the uniaxial actuator. Therefore, the rotation angle of the galvanometer mirror can be made larger than in the conventional case, and the movement amount of the uniaxial actuator can be reduced accordingly. As a result, there is no concern about bearing wear, and in addition to extending the life of the uniaxial actuator, tracking adjustment can be performed quickly, resulting in high-speed search. .

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a focus adjustment circuit used in an optical disk device according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between rotation of a galvanometer mirror and a radial push-pull signal.

FIG. 3 is a plan view of an optical disk device to which the invention is applied.

FIG. 4 is a sectional view of a slider.

FIG. 5 is a perspective view of focus adjusting means.

FIG. 6 is a diagram showing a rotation of a galvanometer mirror and a deviation of a return beam.

FIG. 7 is a diagram showing the rotation of the galvanometer mirror and the deviation of the return beam.

FIG. 8 is an explanatory diagram of a photodetector.

FIG. 9 is a system diagram showing another example of focus adjusting means adopted by the present invention.

FIG. 10 is a plan view of an optical disk device showing another embodiment adopted by the present invention.

FIG. 11 is a diagram of an angle sensor.

FIG. 12 is a diagram showing a relationship between a light receiving element and a beam spot.

FIG. 13 is a diagram showing the relationship between galvanometer mirror rotation and defocus.

FIG. 14 is a diagram showing a relationship between surface deviation of an optical disc and a focus error.

FIG. 15 is a diagram showing a relationship between a mirror rotation angle and a push-pull signal.

[Explanation of symbols]

 1 Optical Disc 10 Optical Disc Device 20 Optical Block 21 Laser Diode 27 Photodiode 30 Deflection Means 31 Galvano Mirror 40 Uniaxial Actuator 50 Slider 60 Focus Adjusting Means 61 Objective Lens

Claims (4)

[Claims] 1. The light from the light emitting means is guided into an objective lens provided on a uniaxial actuator by changing its optical path by a deflecting means, and at least data is reproduced while irradiating the light from the objective lens onto an optical disk. In the optical disc device configured to perform the above, a focus error detection unit that is generated by tilting the deflection unit for tracking control is provided, and the focus adjustment unit equipped with the objective lens is controlled by the output of the focus error detection unit. An optical disk device characterized in that a focus error is removed by means of. 2. The optical disk device according to claim 1, wherein a galvano mirror is used as the deflecting means. 3. A light detecting means for detecting return light is used as the focus error detecting means, and the focus adjusting means is controlled by a light detection output according to a deflection rotation angle of the deflecting means. The optical disk device according to claim 1, wherein: 4. The focus error detecting means,
An angle sensor for detecting a deflection rotation angle of the deflection means is used, and the focus adjustment means is controlled by a photodetection output corresponding to the deflection rotation angle obtained from the angle sensor. Item 1. The optical disk device according to item 1.