JP3766526B2 - Method for adjusting position of optical sensor in optical information recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical sensor position adjusting method in an optical information recording / reproducing apparatus.
[0002]
[Problems to be solved by the invention]
Recently, development of a magneto-optical disk apparatus having a surface recording density exceeding 10 Gbit / (inch) ² is in progress. In this apparatus, for example, the incident angle of the laser beam with respect to the objective optical system provided at the tip of a coarse motion arm that rotates, for example, in a direction intersecting the track of the magneto-optical disk is finely adjusted by a deflecting means such as a galvo mirror. It is considered that the tracking is performed accurately at a narrow track pitch level of 0.34 μm, for example. By the way, in such a device, for example, it is necessary to efficiently and accurately incorporate an optical sensor for obtaining a reproduction signal, and improvement of the position adjustment method has been desired.
[0003]
[Means for Solving the Problems]
The present invention has been made in view of the above-described background, and the invention of claim 1 is directed to the light of the light beam incident on the light receiving surface of an optical sensor for detecting the light beam of the optical information recording / reproducing apparatus. The light beam is widened during adjustment so that the light flux width in the adjustment direction of the sensor, which is at least one direction orthogonal to the axis, is equal to or greater than the width of the adjustment direction of the light receiving surface, and in this state, the optical sensor is moved in the adjustment direction. The position of the light sensor is adjusted to the center of the light receiving surface in the adjustment direction by searching for a position where the output of the optical sensor is maximized.
[0004]
DETAILED DESCRIPTION OF THE INVENTION
First, recording called near field recording (NFR) technology, which was proposed to meet the increasing demand for external storage devices, especially the demand for large storage capacity, due to recent advances in hardware and software related to computers An outline of a magneto-optical disk recording / reproducing apparatus using a reproducing method will be described with reference to FIGS.
[0005]
FIG. 1 is an overall schematic diagram of the optical disk apparatus. In the disk drive device 1, an optical disk 2 is mounted on a rotating shaft of a spindle motor (not shown). On the other hand, a rotating (coarse movement) arm 3 is attached so as to be parallel to the recording surface of the optical disc 2 in order to reproduce or record information on the optical disc 2. The rotating arm 3 can be rotated about a rotating shaft 5 by a voice coil motor 4. A floating optical head 6 on which an optical element is mounted is mounted on the tip of the rotating arm 3 facing the optical disk 2. Further, a light source module 7 including a light source unit and a light receiving unit is disposed in the vicinity of the rotation shaft 5 of the rotation arm 3, and is configured to be driven integrally with the rotation arm 3.
[0006]
2 and 3 illustrate the tip of the rotating arm 3, and in particular, the floating optical head 6 will be described in detail. The floating optical unit 6 is attached to the flexure beam 8 and is disposed to face the optical disc 2. The flexure beam 8 is fixed to the rotating arm 3 at the other end, and is pressurized in a direction in which the floating optical unit 6 at the tip is brought into contact with the optical disc 2 by the elastic force of the flexure beam 8.
[0007]
The flying type optical unit 6 includes a flying slider 9, an objective lens 10, a solid immersion lens (SIL) 11, and a magnetic coil 12, and converges a parallel laser beam 13 emitted from the light source module 7 onto the optical disk 2. To work. Further, a rising mirror 31 is fixed to the tip of the rotating arm 3 in order to guide the laser beam 13 to the floating optical unit 6. The laser beam 13 incident on the objective lens 10 by the rising mirror 31 is converged by the refraction action of the objective lens 10. A solid immersion lens (SIL) 11 is disposed in the vicinity of the condensing point, and irradiates the optical disc 2 with the convergent light as finer evanescent light 15.
[0008]
A magnetic coil 12 for recording by a magneto-optical recording system is formed around a solid immersion lens (SIL) 11 facing the optical disk 2, and a magnetic field necessary for recording is applied on the recording surface of the optical disk 2. It can be applied. The evanescent light 15 and the magnetic coil 12 enable high-density recording and reproduction on the optical disc 2. Note that the floating optical unit 6 floats by a minute amount due to the air flow caused by the rotation of the optical disc 2, and follows surface vibration of the optical disc 2. For this reason, the focus control (focus servo) of the objective lens, which was necessary in the conventional optical disc apparatus, is not required.
[0009]
Hereinafter, the light beam guided to the light source module 7 and the floating optical unit 6 mounted on the rotating arm 3 will be described in detail with reference to FIGS. The rotating arm 3 has a floating optical unit 6 mounted at the tip, and a driving coil 16 for driving the voice coil motor 4 is fixed to the other end. The drive coil 16 is a flat coil, and is inserted and disposed in a magnetic circuit (not shown) with a gap. The rotating shaft 5 and the rotating arm 3 are fastened by bearings 17 and 17 so as to be rotatable. When a current is applied to the drive coil, the rotating arm 3 is rotated about the rotating shaft 5 by the electromagnetic action with the magnetic circuit. Can be moved.
[0010]
The light source module 7 mounted on the rotating arm 3 includes a semiconductor laser 18, a laser driving circuit 19, a collimating lens 20, a composite prism assay 21, a laser power monitor sensor 22, a reflecting prism 23, a data detection sensor 24, and tracking detection. A sensor 25 is arranged. The divergent light beam emitted from the semiconductor laser 18 is converted into a parallel light beam by the collimator lens 20. The cross-sectional shape of the parallel light flux is oblong due to the characteristics of the semiconductor laser 18, and it is inconvenient to finely focus the light beam on the optical disk 2, so it is necessary to convert it into a substantially circular cross-section. Therefore, the cross-sectional shape of the parallel light beam is shaped by causing the parallel light beam having an elliptical cross section emitted from the collimator lens 20 to enter the composite prism assay 21.
[0011]
The incident surface 21a of the composite prism assay 21 forms a predetermined slope with respect to the incident optical axis, and the sectional shape of the parallel light beam can be shaped from an oval shape to a substantially circular shape by refracting the incident light. . The shaped laser beam travels through the composite prism assay 21 and enters the first half mirror surface 21b. The first half mirror surface 21b is set to guide the information obtained from the optical disc 2 to the data detection sensor 24 and the tracking detection sensor 25, but the output of the laser emitted from the semiconductor laser 18 in the forward path. It plays the role of separating the light flux to the laser power monitor sensor 22 for detecting the power.
[0012]
Since the laser power monitor sensor 22 outputs a current proportional to the intensity of the received light, the output of the semiconductor laser 18 can be stabilized by feeding back this output to a laser power control circuit (not shown). The laser beam 13 having a substantially circular cross-sectional shape emitted from the composite prism assay 21 is irradiated to the deflection mirror 26, and the traveling direction of the laser beam 13 is changed. The deflecting mirror 26 is attached to a galvano motor 27 having an axis perpendicular to the paper surface as the center of rotation, so that the laser beam 13 can be swung by a minute angle in a direction parallel to the paper surface.
[0013]
The galvano motor 27 is provided with a deflection mirror position detection sensor 28 for detecting the rotation angle of the deflection mirror 26. The laser light beam 13 reflected by the deflection mirror 26 passes through the first relay lens 29 and the second relay lens (imaging lens) 30 and is reflected by the rising mirror 31 to reach the floating optical unit 6. The first relay lens 29 and the second relay lens 30 have a conjugate relationship between the reflecting surface of the deflecting mirror 26 and the pupil plane (main plane) of the objective lens 10 arranged in the floating optical unit 6. Thus, a relay lens optical system is formed. That is, when the focused beam on the optical disc 2 slightly deviates from a predetermined track, the laser beam 13 incident on the objective lens 10 is tilted by slightly rotating the deflection mirror 26 to move the focal point on the optical disc 2. To correct. However, when the focus is corrected by this method, if the optical distance between the deflecting mirror 26 and the objective lens 10 is long, the amount of movement of the laser beam 13 incident on the objective lens 10 becomes large, and can enter the objective lens 10. It may disappear.
[0014]
In order to avoid such a phenomenon, the first relay lens 29 and the second relay lens 30 set the relationship between the reflection surface of the deflection mirror 26 and the pupil surface of the objective lens 10 to be a conjugate relationship, Even when the deflection mirror 26 rotates, the laser beam 13 incident on the objective lens 10 does not move, and accurate tracking control is possible. Note that the access operation over the inner circumference / outer circumference of the optical disk 2 is performed by rotating the rotating arm 3 by the voice coil motor 4, and only the very small tracking control is performed by rotating the deflection mirror 26.
[0015]
The return laser beam 13 that has been reflected back from the optical disk 2 travels in the opposite direction to the forward path, is reflected by the deflection mirror 26, and enters the composite prism assay 21. Thereafter, the light is reflected by the first half mirror surface 21b and travels toward the second half mirror surface 21c. The second half mirror surface 21c generates transmitted light toward the tracking detection sensor 25 and reflected light toward the data detection sensor 24, and separates the laser beam on the return path. The laser beam transmitted through the second half mirror surface 21c is irradiated to the tracking detection sensor 25, and a tracking error signal is output.
[0016]
On the other hand, the laser beam reflected by the second half mirror surface 21 c is polarized and separated by the Wollaston prism 32, converted into convergent light by the condenser lens 33, reflected by the reflecting prism 23, and irradiated on the data detection sensor 24. Is done. The data detection sensor 24 has two light receiving areas, and receives the two polarized beams separated by the Wollaston prism 32, thereby reading the data information recorded on the optical disc 2 and outputting a data signal. More precisely, the tracking error signal and the data signal are generated by a head amplifier circuit (not shown) and sent to a control circuit or an information processing circuit.
[0017]
Next, a method for adjusting the position of the sensors (tracking detection sensor 25, data detection sensor 24, etc.) of the disk drive device 1 will be described with reference to FIGS. Here, the position adjustment is the position adjustment of the sensor in the direction orthogonal to the optical axis of the light beam incident on the sensor.
FIG. 6 is a diagram showing the principle of the position adjustment method according to the present invention. In the disk drive device 1, the light beam emitted from the light source module 7 enters the objective lens (indicated by L1 in FIG. 6) as a parallel light beam, and is an information recording surface of the optical disk 2 (a surface indicated by a broken line DS in FIG. 6). ), Each element of the optical system is arranged so as to converge. The path of the light beam at this time is shown by a two-dot chain line in FIG. 6, and the light beam reflected by the information recording surface DS returns on the same optical path as the incident light beam and converges on the sensor (indicated by S1 in FIG. 6). It is like that.
[0018]
When adjusting the sensor position, the light beam converged by the objective lens L1 is moved to the objective lens side from the position where the information recording surface DS is originally located. In FIG. 6, instead of moving the information recording surface DS, the mirror 80 has its reflecting surface positioned closer to the objective lens than the convergence point of the light beam converged by the objective lens L1. By doing so, as indicated by a solid line P in FIG. 6, the light beam reflected by the mirror 80 converges after reflection and enters the objective lens L1 as divergent light. Here, since the convergence point of the light beam is on the lens side with respect to the focal position of the objective lens L1, the diverging light incident on the objective lens L1 proceeds to the sensor S1 side (right side in the figure) as diverging light. As a result, at the time of normal recording and reproduction, the convergence position of the light beam converged on the sensor S1 by the lens L2 is behind (on the right side in the drawing) from the sensor S1. That is, the light beam is irradiated onto the sensor S1 in the defocused state. By adjusting the distance between the mirror 80 and the lens L1, the size of the beam spot on the sensor S1 can be made substantially the same as that of the sensor S1.
[0019]
FIG. 7A shows a beam spot S having the same size as that of the sensor S1 irradiated on the sensor S1. When the beam spot S moves from the front side (left side in the figure) to the right side in the figure along the direction indicated by the arrow A in the figure with respect to the sensor S1, the output of the sensor S1 is shown in FIG. 7 (B). To change. When the beam spot S is smaller than the sensor S1, the sensor output signal shows a peak value while the entire beam spot is irradiated on the sensor S1, so that the beam spot irradiates the center position of the sensor. It becomes difficult to adjust the position of the sensor. However, as shown in FIGS. 7A and 7B, since the diameter of the beam spot S is the same as the width of the sensor S1, it is possible to easily know the position of the sensor that the beam spot irradiates the central position of the sensor. The position of the sensor S1 can be adjusted easily and accurately.
[0020]
The configuration shown in FIG. 6 can be easily applied to the disk drive device 1 described above, and can be applied to any position adjustment of the data detection sensor 24 and the tracking detection sensor 25.
[0021]
When only one direction of the position adjustment of the sensor S1 is required, the size of the beam spot in the direction only needs to coincide with the width of the direction of the sensor S1, and the sensor size in other directions. It does not have to be the same. Further, since the energy distribution of the beam spot on the sensor S1 is a Gaussian distribution, even when the size of the beam spot is larger than the sensor, the position where the output signal of the sensor S1 reaches a peak can be easily identified. Therefore, the position adjustment can be performed easily and accurately.
[0022]
In addition, although the said lens L1 was demonstrated as an objective lens, when not using an objective lens, the lens L1 can be substituted to the lens equivalent to an objective lens.
[0023]
【The invention's effect】
As described above, the size of the beam spot irradiated on the sensor is set to be equal to or larger than the sensor width in at least the sensor position adjustment direction, so that the relative position between the sensor and the beam spot at which the sensor output signal peaks. Can be accurately identified, and therefore the position of the sensor can be adjusted easily and accurately.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic configuration of a magneto-optical disk apparatus according to an embodiment.
FIG. 2 is a view showing a distal end portion of a rotating arm.
FIG. 3 is a cross-sectional view showing a floating optical unit.
FIG. 4 is a plan view showing a deflection mirror and a floating optical unit.
FIG. 5 is a side sectional view of a rotating arm.
FIG. 6 is a diagram showing the principle of the sensor position adjustment method of the present invention.
FIG. 7A is a diagram showing a state in which a beam spot is irradiated on the sensor, and FIG. 7B is a graph showing the intensity of the output signal of the sensor accompanying a change in the relative position between the sensor and the beam spot.
[Explanation of symbols]
2 Optical disk 3 Rotating arm 4 Voice coil motor 6 Floating optical unit 8 Flexure 26 Deflection mirror 29 First relay lens 30 Second relay lens (imaging lens)
80 Reflective surface L1 Objective lens L2 Lens S1 Sensor

Claims (1)

The light flux width in the adjustment direction of the sensor that is at least one direction orthogonal to the optical axis of the light flux incident on the light receiving surface of the optical sensor that detects the light flux of the optical information recording / reproducing apparatus is the adjustment direction of the light receiving surface. The light beam is widened at the time of adjustment so as to be equal to or larger than the width of the light sensor. A method for adjusting the position of an optical sensor in an optical information recording / reproducing apparatus, wherein the position is adjusted to the center of the direction.

Images