JPH03260923A - Optical head and optical disk driving device formed by using this head - Google Patents

Abstract

PURPOSE:To obtain the optical head which is excellent in recording and reproducing characteristics, such as CN and crosstalks, and is suitable for high-density recording by positioning an optical base plate and an objective lens actuator in the plane direction with substantially no change in the main constitution of the head. CONSTITUTION:A position pin 25 is provided near the principal point position of the objective lens 7 provided on the objective lens actuator 24 is provided on the base plate 23 and a fitting hole 26 provided in the base part of the actuator 24 is fitted onto this pin, by which the plate 23 and the actuator 24 are positioned in the plane direction thereof. The optical axis of the reflected light of a perpendicular reflection mirror 6 and the optical axis of the objective lens 7 are subjected to angle adjustment so as to minimize a coma aberration. The fulcrum is fastened to a screw hole 27 provided in the base part of the objective lens actuator 24 via a swing and tilt spring 13. The height of the fulcrum is varied by turning the screw member 28, by which the objective lens is positioned in the height direction of the principal point of the objective lens. The base plate 23 and the actuator 24 are positioned in the plane direction in such a manner with the substantially no change in the main constitution of the head.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in compact discs, laser discs, image document file devices, external storage devices for computers, etc., and reproduces information using a light beam of a semiconductor laser. and optical recording for recording and erasing;
The present invention relates to an optical head used in a playback device and an optical disk drive device using this optical head.

BACKGROUND OF THE INVENTION In recent years, optical memory devices have attracted attention as external storage devices for computers due to their features of high density, large capacity, and non-contact. Among them, the development of rewritable magneto-optical recording systems is most anticipated. In principle, a light beam emitted from a semiconductor laser is irradiated onto an information recording medium located at the bottom of a tank from an amorphous perpendicularly magnetized film with perpendicular anisotropy, and when the temperature is raised to near the cue point, magnetization occurs. It is recorded by being magnetized in the opposite direction by an external magnetic bias. During reproduction, the information signal is extracted by rotating the vibration direction of the light by 0.3 to 0.5 degrees in the left-right direction depending on the magnetization direction of the information recording medium due to the magneto-optic effect on the surface of the information recording medium. During erasing, the information recording medium is irradiated with a light beam emitted from a semiconductor laser in the same way as during recording, and an external magnetic bias is applied in the opposite direction to that during recording.

In addition, in order to achieve the compact size and large capacity that is a feature of optical recording and reproducing devices, it is essential to make the beam focused on the information recording medium small in diameter and uniform. - In order to reduce the beam diameter for boat fishing, it is necessary to shorten the wavelength of the semiconductor laser or increase the numerical aperture NA of the objective lens. Wavefront aberration has a large effect. Since it takes a considerable amount of time to develop a short wavelength laser and a high NA objective lens, it is important to first make the intensity distribution of the objective lens uniform.

The conventional optical head of this type of magneto-optical disk device has a fourth
A tank bottom as shown in Fig. 5 and Fig. 5 was common.

Below is that tI! Explain the precepts.

As shown in the figure, a semiconductor laser 1 emits a light beam,
The light beam emitted from this semiconductor laser 1 is a divergent and elliptical beam. Therefore, this diverging beam is converted into a parallel beam by the collimating lens 2. In addition, since this parallel beam is an elliptical beam, in order to convert it into a circular beam, the collimated emitted light is directed to the reflecting mirror 4 so that it has a constant incident angle with respect to the shaping prism 3.
It is reflected by After being converted into a circular beam by the shaping prism 3, the beam passes through the non-deflecting beam brick 5, and the optical axis is bent at right angles by the right angle reflection mirror 6. The light beam bent at right angles enters the objective lens 7 and is focused on the information recording medium 8 surface. At this time, if the light beam incident on the objective lens 7 is made larger than the effective diameter of the objective lens 7, the light beam focused by the objective lens 7 exhibits an Airy disk distribution due to the diffraction effect, and the beam The diameter can be reduced. Also, if you try to make the narrowed beam uniform in diameter in the radial and circumferential directions,
The diameter of the parallel beam incident on the objective lens 7 is a circular beam, and it is necessary to make the light quantity distribution uniform in the radial direction and the circumferential direction. Furthermore, if there is an angular misalignment between the optical axis of the light beam reflected by the right-angle reflecting mirror 6 and the optical axis of the objective lens 7, coma aberration will occur, which will have a negative effect on recording and reproducing characteristics such as the CN ratio and crosstalk characteristics. It turns out. therefore,
In order to reduce angular deviation, two screw holes 10 are provided in the base of the objective lens actuator 9 as shown in FIG. 5, and a support ball 11 is attached to the optical base 12 near the principal point of the objective lens 7. The optical axis of the reflected light of the right-angle reflecting mirror 6 and the optical axis of the objective lens 7 are angularly adjusted so that the coma aberration is minimized by fastening the screw member 14 to the screw hole IO via the tilting spring 13. ing.

The light beam irradiated onto the information recording medium 8 is reflected and enters the objective lens 7 again to become a parallel beam. In addition, this parallel beam enters the non-polarizing beam splitter 5 again, and the amount of light corresponding to the reflectances Rp and Rs of the P-polarized light and S-polarized light is reflected, passes through the % wavelength plate 15, and enters the polarized beam splitter 16. , the beam is separated into P-polarized light and S-polarized light. Of the separated light beams, the transmitted P-polarized light beam is imaged by a tracking detection lens 17 onto a two-split photodetection element 18, and a tracking error signal is detected. In addition, the S-polarized light beam reflected by the polarized beam splinter 6 is transmitted through the claw detection lens 19.
The light beam is focused by , separated into two beams by a two-split mirror 20, and focused on a four-split light detection element 21 provided at the midpoint between the focal lengths of the two light beams, thereby detecting a focus error signal.

Due to these focus error signals and tracking error signals, the information recording medium 8 may be deflected by ±1 μm in the focusing direction and ±1 μm in the tracking direction even if there is some degree of eccentricity.
Positioning control of 0.1 μm or less is achieved by driving the objective lens 7 with the objective lens drive coil 22.

Problems to be Solved by the Invention In such conventional optical heads, the optical axis tilt of the semiconductor laser 1 with respect to the reference plane and the optical axis position of the objective lens 7 are held by rubber dampers, making it difficult to perform highly accurate positioning during assembly. As a result, the light intensity distribution of the incident light with respect to the optical axis of the objective lens 7 is non-uniform and has large variations, resulting in large wavefront aberrations and adversely affecting recording and reproducing characteristics such as CN ratio and crosstalk. Therefore, in order to make the light intensity distribution of the incident light uniform with respect to the optical axis of the objective lens 7, the holding member that holds the semiconductor laser 1 and the collimating lens 2 is separated, and
By being movable in the vertical direction, the center of the optical axis of the objective lens 7 and the center of the light intensity distribution of the incident light are positioned with high precision. Therefore, the optical axis of the objective lens 7 is reflected at right angles.
If the positional deviation from the center of lens 6 is large, collimating lens 2
The parallel beam emitted from the mirror 4, the shaping prism 3, the non-polarizing beam splitter 5, and the right-angle reflecting mirror 6 are deviated from the usable effective portions, so that the light intensity distribution of the light incident on the objective lens 7 becomes uneven. There have been problems in that the intensity of the light beam that is imaged on the eight surfaces of the information recording medium is deteriorated. Another problem is that the optical head mounting is a composite part with a height dimension from the reference position to the principal point position of the objective lens 7 at the neutral position of the objective lens 7.
Due to assembly tolerances and angular shift adjustment of the objective lens actuator 9, variations and dimensional tolerances become large. If the other dimensional tolerances become large, the neutral upper end surface of the objective lens 7 and the information recording medium when the optical head is attached to the traverse mechanism section and the information recording medium 8 is attached to the flange section fastened to the spindle motor. If the distance to the bottom surface of the lens 8 varies widely, including variations in dimensional tolerance due to mounting, and the distance exceeds the usable effective movable range of the objective lens 7 when the focus servo is applied, the focus servo control of the objective lens 7 will not be applied. It disappears. Therefore, there is a method of absorbing the size variation by increasing the effective movable range of the objective lens actuator 9 in which the objective lens can be used. This contradicts weight reduction. For this reason, the structure was designed so that the height of the flange surface could be adjusted when mounting the drive, but there were problems in terms of reliability and cost.

The present invention is intended to solve the above problems, and its first object is to obtain an optical head that has excellent recording and reproducing characteristics such as CN ratio and crosstalk, and is suitable for high-density recording. A second purpose is to reduce the usable variable range of the objective lens to make it thinner. Furthermore, a third object of the present invention is to provide an optical disc drive device that does not require a height adjustment mechanism for a flange surface on which an information recording medium is attached.

Means for Solving Problem 1 In order to achieve the above-mentioned first object, the optical head of the present invention has a first problem in that the optical base table and the objective lens actuator section are provided with means for positioning in a plane direction. It is used as a solution. Also, in order to achieve the second purpose,
In addition to the first problem-solving means, a single-flow problem-solving means is provided with a variable height adjustment mechanism for positioning the principal point of the objective lens in the height direction. Further, in order to achieve the third object, the optical disc drive device of the present invention is provided with an optical head according to the first and second problem solving means described above.

Effects of the optical head of the present invention, due to the above-mentioned first problem-solving means, the parallel beam light emitted from the collimating lens is not significantly eclipsed by the right angle reflection ξ, so that the laser power on the information recording medium is reduced. It also disappears. In addition, since a light beam with a uniform intensity distribution is incident on the objective lens, the beam focused on the information recording medium has small wavefront aberration and is narrowed down to a small spot shape. Good reproduction characteristics can also be obtained. In addition, the second problem solving means 1. By precisely positioning the height from the optical base mounting reference plane to the top surface of the lens when the objective lens is neutral, variations in the distance between the top surface of the objective lens and the bottom surface of the information recording medium when the drive is installed can be reduced. Even when focus servo is applied, stable focus servo can be applied without exceeding the usable effective movable range of the objective lens, and the movable range of the objective lens can be reduced, and the objective lens actuator can be made thinner. Further, the optical disc drive device of the present invention has good recording and reproducing characteristics such as CN ratio and crosstalk due to the above problem solving means, and an adjustment mechanism for adjusting the height of the flange surface on which the information recording medium is attached can be omitted. can.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG. Note that components having the same configuration as those of the conventional example are given the same reference numerals, and description thereof will be omitted.

As shown in the figure, the optical Heath stand 23 includes the semiconductor laser 1,
Non-polarized beam splinter 5.2 split light detection element 18.4
This optical base 2 holds the divided light detection element 21, etc.
3 is provided with a positioning bean 25 near the principal point position of the objective lens 7 provided in the objective lens actuator 24, and a fitting hole 2 provided in the heel portion of the objective lens actuator 24.
6, positioning of the optical base 23 and the objective lens actuator 24 in the plane direction is performed. The optical axis of the reflected light from the right-angle reflection mirror 1 6 and the optical axis of the objective lens 7 are angularly adjusted so that the coma aberration is minimized. The screw member 2 fastened to the screw hole 27 provided in the
8 is used, and the height of the fulcrum can be varied by turning the screw member 28, making it possible to position the objective lens principal point in the height direction. The angle adjustment method is performed by fastening the screw member 29 to the screw hole 27 of the head of the objective lens actuator 24 via the tilting spring 13, as in the conventional example.

Next, another embodiment of the present invention will be described with reference to FIG. Components having the same configuration as those in the above embodiment are given the same reference numerals and explanations will be omitted.

As shown in the figure, the optical base 30 has a reference guide surface 31
is provided and positioned with respect to the reference plane of the objective lens actuator 24, so that the positioning of the optical Heess stand 30 and the objective lens actuator 24 in the plane direction can be ensured.

By positioning the optical Haas stand 23 or 30 and the objective lens actuator 24 with the above configuration, the principal point of the objective lens 7 can also be positioned in the height direction.

Next, an embodiment of an optical disk drive device using the optical head having the above structure will be described with reference to FIG. 3.

As shown in the figure, the optical head 32 is of the above-mentioned type, and is controlled by an optical head control circuit 33 to irradiate a light beam onto an information recording medium 34 to record information, and also receives reflected light to generate electrical signals. and input it to the signal processing circuit 35. The spindle motor 36 is driven by a rotation control circuit 37 to drive the information recording medium 34 . The coarse motor 38 moves the optical head 32 in the radial direction of the information recording medium 34, and is controlled by a coarse motor control circuit 39. Optical head control circuit 33, rotation control circuit 37
The coarse motor control circuit 39 is controlled by a drive controller 40.

To explain the operation in the above configuration, the optical head 3 is attached to the information recording medium 34 driven by the spindle motor 35.
2 emits a light beam to record information on the information recording medium 34, and during reproduction, the reflected light from the information recording medium 34 is received and converted into an electrical signal. At this time, since the optical head 32 has the above-mentioned configuration, the recording and reproducing characteristics such as CN ratio and crosstalk are good, and the dimensional accuracy of the height from the optical head mounting reference surface to the objective lens principal point position can be reduced. Therefore, an adjustment mechanism for adjusting the height of the flange surface on which the information recording medium 34 is attached can be omitted. Note that examples of the optical disc drive device include an optical reproduction-only drive device, a recordable write-once optical disc device, and a rewritable rewritable optical disc device.

Effects of the Invention As is clear from the above embodiments, according to the optical head of the present invention, the main configuration of the optical head is hardly changed, and by positioning the optical Hess stand and the objective lens actuator in the plane direction, An optical head with excellent recording and reproducing characteristics such as CN ratio and crosstalk, suitable for high-density recording, can be obtained.In addition, by positioning the height of the principal point of the objective lens, the usable movable range of the objective lens can be improved. can be made smaller, resulting in a thinner optical head.

Furthermore, according to the optical disk drive device of the present invention, by using the above optical head, a highly reliable optical reproduction-only drive device that is small in size and has a large capacity and eliminates the height adjustment mechanism of the flange surface on which the information recording medium is attached. Optical disk drive devices such as write-once optical disk devices and rewritable optical disk devices can be provided.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of an optical head according to an embodiment of the present invention;
FIG. 2 is an exploded perspective view of an optical head according to another embodiment of the present invention, FIG. 3 is a schematic configuration diagram of an optical disk drive device according to an embodiment of the present invention, and FIG. 4 is an optical diagram of a conventional optical head. FIG. 5 is an exploded perspective view of the same optical head. 1... Semiconductor laser, 5... Non-polarizing beam splitter (beam splitter), 7...
Objective lens, 18... 2-split light detection element (light detection element), 21... 4-split light detection element (light detection element), 23... To optics 5 - stand, 24...objective lens actuator,
25...Positioning bin (positioning means),
26... Fitting hole (positioning means).

Claims (7)

[Claims] (1) An optical base that holds a semiconductor laser as a radiation means that emits a light beam, a beam splitter that separates the light beam, and a photodetector that receives reflected light from an information recording medium and converts it into an electrical signal. and an objective lens actuator for driving an objective lens that focuses a light beam on the information recording medium, and means for positioning the objective lens actuator on the optical base. (2) The optical head according to claim 1, wherein the positioning means includes a fitting portion on the optical base stand and the objective lens actuator, and positions the optical head in a planar direction. (3) The optical head according to claim 2, wherein the positioning means is configured such that a positioning pin provided on the optical base is fitted into a fitting hole provided on the objective lens actuator. (4) The optical head according to claim 1, wherein the positioning means comprises a guide reference surface on the optical base and positions the optical head in a planar direction. (5) The optical head according to claim (1), further comprising a positioning adjustment mechanism that can vertically vary the height of the objective lens principal point position. (6) A claim in which the objective lens actuator is provided with at least two screw holes, and the height can be adjusted by fastening the screw member to the screw hole of the objective lens actuator via a spring material on the optical base. (5) The optical head described. (7) The optical head according to any one of claims (1), (2), (3), (4), (5), and (6), an information recording medium, a spindle motor that drives the information recording medium, and the a coarse motor that sends the optical head in the radial direction of the information recording medium;
An optical disk drive device comprising: a signal processing circuit that processes an output signal of the optical head.