JPS61156538A - Optical head - Google Patents

Abstract

PURPOSE:To expand a tracking control range by holding an integral objective lens actuator by a parallel moving mechanism in a tracking direction, and also providing a linear driving mechanism for moving the integral objective lens actuator in the tracking direction in accordance with an integral output of a tracking control signal. CONSTITUTION:With respect to an integral objective lens actuator 5 for moving and controlling an objective lens in orthogonal three axial directions, a 90 deg. deflecting body for polarizing by 90 deg. an optical beam supplied to a tracking control direction and making it incident on the objective lens is fixed to the inside of the integral objective lens actuator 5, and the integral objective lens actuator 5 on which this deflecting body has been provided is moved in parallel to the tracking direction in accordance with an integral output of a tracking control signal. In such a way, the integral objective lens actuator is adjusted roughly in the tracking direction, also a fine adjustment of tracking is executed, and when it has exceeded these control ranges, a linear feed of an optical head is executed, therefore, a tracking control range is expanded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The great invention relates to an optical head used for recording information on an optical recording medium or reading recorded information, and in particular, a wide range of tracking control can be performed quickly and with high precision. The invention relates to an optical head that can be used for various purposes.

<Prior Art> In recent years, with the rapid development of optical recording and reproducing technology, various optical information recording and reproducing devices such as optical video disc players, compact disc players, and video file devices have been developed. This information optical recording/reproducing device records information by deforming or discoloring the optical recording layer by irradiating an optical recording medium such as an optical disk with a laser beam modulated according to the recorded information, In this method, optically recorded information is read by detecting changes in reflected light in an optical recording layer due to irradiation with a weak laser beam.

Here, the optical head irradiates the recording medium with a laser beam and reads the reflected light, and is an important part of the information optical recording/reproducing apparatus. and,
This optical head needs to perform focus control to focus the laser beam on the surface of the optical recording layer of the optical recording medium, radial control to make the laser beam follow the recording track, and jitter control in the rotational direction.

Here, in the optical head commonly used in the past, a tracking error signal is obtained by dividing the reflected light of the laser beam in the tracking control direction and finding the difference between the two received light signals. By supplying this tracking error signal to the tracking control system, an objective lens actuator that moves the objective lens in three orthogonal axes directions is controlled to align the laser beam along the recording track.

<Problems to be Solved by the Invention> However, in the optical head with the above configuration, since tracking control is performed by moving the objective lens by the objective lens actuator, the optical axis of the objective lens shifts, resulting in The allowable control range becomes narrow. On the other hand, if the surface runout of the optical disc becomes large.

Due to unstable tracking, larger control tolerances are required. Furthermore, if the feed pitch in the tracking direction is miniaturized to improve accuracy, there is a problem in that the speed during fast forwarding or random access decreases.

Means for Solving the Problems> Accordingly, 1. the optical head according to the present invention is capable of directing a light beam supplied in the tracking control direction to an integrated objective lens actuator that controls the movement of the objective lens in three orthogonal axes directions. A 90° deflector that deflects the beam and enters the objective lens is fixed inside an integrated objective lens actuator, and the integrated objective lens actuator equipped with this 90° deflector is tracked according to the integrated output of the tracking control signal. It moves parallel to the direction.

In the optical head configured in this way, the integrated objective lens actuator is coarsely adjusted in the tracking direction according to the integral output of the tracking control signal, and further finely adjusted by the integrated objective lens actuator. Adjustments are made, and when these control ranges are exceeded, the optical head is linearly moved, so that the tracking control range is expanded. Further, since tracking control is performed by coarse adjustment and fine adjustment, even if the feed accuracy is increased, the coarse adjustment works to increase the speed of fast forwarding and random access.

<Embodiment> FIG. 1 is a perspective view of essential parts showing an embodiment of an optical head according to the present invention, in which a fixing block 2 is provided on the surface of a base 1. A pair of leaf springs 3a and 3b are fixed to the two faces extending in the horizontal direction to form a parallel leaf spring 4. An integrated objective lens actuator 5 is fixed between the tips of this parallel plate spring 4. Here, the integrated objective lens actuator 5 moves the objective lens 6 in three orthogonal axes, that is, in the focus control direction. The structure is such that movement is controlled by a voice coil system in the tracking control direction and jitter control direction. A 90° mirror 7 is provided inside the integrated objective lens actuator 5 as a 90° deflector that deflects the laser beam supplied along the tracking direction by 90° and supplies it to the objective lens 6. There is. Further, a fixed block 8 protruding from the base 1 is provided in the direction of movement of the integrated objective lens actuator 5 by the parallel plate spring 4, and a linear A drive mechanism 9 is provided. The linear drive mechanism 9 is of a voice coil type, and as shown in FIG. 10, and a linear drive mgtii that surrounds the inside and outside of the linear drive coil 10 fixed to the fixed block 8.

Here, the linear drive magnetic pole 11 includes a cylindrical side yoke lla, a center yoke llb provided along the axis of the side yoke lla, and a side yoke lla.
and a magnet lie interposed in a part between the side yoke lla and the center yoke llb, and the linear drive coil 10 is positioned between the magnetic gap formed between the tips of the side yoke lla and the center yoke llb. become.

On the other hand, on the surface side of the base 1 and in a direction perpendicular to the tracking direction, an optical system 12 is provided to emit a laser beam, detect the reflected light, and convert it into an electrical signal. .

As generally known, this optical system 12 includes a laser diode 12a that generates a laser beam, a collimating lens 12b that converts the laser beam generated from the laser diode 12a into parallel light and supplies it to a prism beam splitter 12C, and a prism beam splitter 12C. An integrated objective lens actuator 5 & 9 is provided to deflect the laser beam supplied from the printer 12c through the single wavelength plate 12b and the lens by 90 degrees.
A 90° mirror 12e that supplies the laser beam along the tracking direction to the 0' mirror 7, and a focusing lens that focuses the returned light separated by the prism beam stabilizer 12c and supplies it to the two-split light receiving element 12f. 1
2g. In addition, 13a, 13b
is a linear slide shaft for linear feeding that passes through holes provided at both ends of the base l and guides the optical head in the tracking direction.

FIG. 3 is a circuit diagram showing an example of a control system for tracking and linear feeding of the optical head shown in FIG.

In the figure, 14 is an operational amplifier that calculates the difference in the output signal of each light receiving element a and b of the two-split light receiving element 12f, and 15 is a phase compensation port that compensates the phase of the output signal of the operational amplifier 14 and supplies it to the amplifier 16. %, 17 is a tracking coil that is provided inside the integrated objective lens actuator 5 and moves the objective lens 6 in the tracking direction by the output signal of the amplifier 16; 18 is an integration circuit that integrates the output signal of the phase compensation circuit 15; 19 is an amplifier that amplifies the output signal of the integrating circuit 18 and supplies it to the linear drive coil 10 shown in FIG. 1, which is provided inside the near drive mechanism 9 and shown in FIG. This is an integrating circuit that double-integrates a signal, and its output signal is supplied to a linear feed motor 22 via an amplifier 21.

In the optical head configured in this way, the laser beam generated from the laser diode 12a is converted into parallel light by the collimating lens 12b, and then passed through the prism beam splitter 12c and the wavelength plate 12d. 90" is supplied to the mirror 12e. By reflecting the laser beam supplied from the wavelength plate 12d, this 90@ mirror 12e is provided to the integrated objective lens actuator 5 as a laser beam along the tracking direction. is supplied to the 90° mirror 7. Then, this 90° mirror 7 is
0@ The laser beam reflected by mirror 7 is
After being further focused by the objective lens 6, it is irradiated onto the surface of an optical disk (not shown). The reflected light of the laser beam irradiated on the optical disk is again passed through the objective lens 6.90'
Input mirror 7.90” Mirror 12e and single wavelength plate 1
By returning to the prism beam spring 12c via the prism beam spring 1d, the zero-separated return light is focused by the focusing lens 12g and then supplied to the two-split light receiving element 12f.

Here, the two-split light-receiving element 12f is configured so that the light-receiving elements a and b split the returned light in the tracking direction and receive the light, as shown in FIG. 3, so tracking is not performed accurately. If so, the output signals of both light receiving elements a and b should match, and the tracking error signal output from the operational amplifier 14 should be zero.

On the other hand, if there is a shift in the trunking, a difference in the outputs of the light receiving elements a and b will occur depending on the shift, and accordingly, the operational amplifier 14 will detect the amount of tracking shift. A tracking error signal having a corresponding level and a polarity indicating the direction of the deviation is output. The tracking error signal generated in this way is
After phase compensation is performed in the phase compensation circuit 15.

The signal is supplied to the tracking coil 17 via the amplifier 16 as a tracking control signal. Here, when a tracking control signal flows through the tracking coil 17, the objective lens 6 is moved in parallel in the tracking direction indicated by the X direction by the voice coil drive method due to the action of the generated magnetic field, thereby performing tracking adjustment.

Here, when the amount of tracking deviation is small, the tracking error signal is returned to zero by control by the tracking coil 17, but in the case of a relatively large deviation, the output signal of the phase compensation circuit 15 is An output signal will be generated from the integrating circuit 18. The output signal of this integrating circuit 18 is then transmitted to an amplifier 19.
The signal is supplied to the linear drive coil 10 as a tracking control signal for coarse yJ. When a tracking control signal is supplied to the linear drive coil 10, the generated magnetic field acts on the linear drive magnetic pole 11 of the linear drive mechanism 9. A force of greater strength will come into play. As a result, the integrated objective lens actuator 5 held by the parallel leaf spring 4 is translated in parallel in the tracking direction, thereby performing rough tracking adjustment. In this case, the movement direction of the integrated objective lens actuator 5 is 90°.
@Since it is the direction of laser beam supply to mirror 7,
This movement has no effect on the laser beam.

Next, if the tracking error signal does not become a sufficiently small value even after tracking control by the linear tracking mechanism is applied, the output signal of the integrating circuit 20 that further integrates the output signal of the a branch circuit 18 is outputted via the amplifier 21. Since the linear feed motor 22 is driven, the base l is linearly moved in the tracking direction along the linear slide shirts 13a and 13b. In this way, 3
Along with the stepwise movement, adjustments will be made for all tracking deviations.

Here, the amount of tracking control by the linear drive mechanism 9 is much larger than the amount of control by the tracking coil 17, and the control operation is also fast, so that tracking control over a wide range can be performed quickly and with high precision. That will happen.

<Effect of the invention> As explained above, there is an optical head according to the present invention.

An integrated objective lens actuator that controls the movement of the objective lens in three orthogonal axes directions is held by a parallel movement mechanism in the tracking direction, and a 90" in which a light beam supplied along the tracking direction is supplied to the objective lens. The deflection body is fixed, and a linear drive mechanism is provided between the outer periphery of the integrated objective lens actuator and the fixed body to move the integrated objective lens actuator in the tracking direction according to the integral output of the tracking control signal. Therefore, by adding rough tracking adjustment using the linear drive mechanism, the tracking control range is greatly expanded, and the control can be performed quickly and with high precision.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a main part showing an embodiment of an optical head according to the present invention, FIG. 2 is a sectional view of a main part of a linear drive mechanism in FIG. 1, and FIG. 3 is an example of a tracking control system. It is a circuit diagram. DESCRIPTION OF SYMBOLS 1... Base, 4... Parallel leaf spring, 5... Integrated objective lens actuator, 6... Objective lens, 7...
・80@mirror, 9...linear drive mechanism, 12・
...Optical system, 13a, 13b...Linear slide shaft.

Claims (2)

[Claims] (1) A base that is guided by a linear slide shaft to linearly feed in the tracking direction, and an integrated objective lens actuator that moves the objective lens in three orthogonal axes directions are moved in parallel in the tracking direction on the base. a parallel movement mechanism fixed within the integrated objective lens actuator to allow the light beam to be incident on the objective lens by equalizing the tracking direction;
An optical head comprising: a deflector; and a linear drive mechanism that moves the integrated objective lens actuator in a tracking direction in accordance with an integrated output of a tracking control signal. (2) The optical head according to claim 1, wherein the parallel movement mechanism for moving the integrated objective lens actuator and the 90° deflector in parallel is constituted by a plate spring.