JPS63206916A - Control method for tracking error detecting optical system of optical head - Google Patents

Abstract

PURPOSE:To reduce the influence of the stray light for a recording/reproducing type optical head by obtaining the ground level of a tracking error detecting optical sensor in a state where the stray light exists. CONSTITUTION:The position of a tracking error detecting optical sensor 5 is controlled in a state where only the stray light caused by the going light produced by a beam splitter 2 is made incident on the sensor 5. Then, the optical axis of an objective lens 3 is controlled through the control of the entire shift of an objective lens actuator 10 in a state where the light returned from a disk is made incident on the sensor 5. As a result, the offset of the tracking error signal is reduced against to the stray light produced by the splitter 2. Thus, it is possible to ensure the tracking control with higher sureness even in a recording state of a recording/reproducing type optical disk device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] This invention is directed to a tracking error detection round type system 11111! of an optical head. ? Regarding method E.

1 Jumei technology 1 As a method for detecting tracking errors in optical heads,
There is a one-beam method. In this one-beam method, a single optical beam emitted from a semiconductor laser returns from the disk to a two-split optical sensor, and tracking errors are detected based on the output difference between the two optical sensors of this two-split optical sensor. Then, the objective lens actuator drives the objective lens according to the tracking error signal to perform tracking control.

The conventional one-beam type optical head described above has a structure in which the actuator base that supports the objective lens holder is simply fixed to the optical head body side with screws, etc.
To adjust the tracking error detection optical system, first, each optical component except the two-split optical sensor for tracking error detection was fixed in a predetermined position, and then the position of the two-split optical sensor was finally adjusted. .

[Problem to be Solved by the Invention 1] Incidentally, normally, not only the return light reflected by the disk but also the stray light generated by the beam splitter enters the two-split optical sensor for tracking error detection. This stray light is, as shown by dashed arrows p, p2 in the ms diagram,
This is the reflected light of the forward light generated when the frimeter light from the semiconductor laser 1 side passes through the beam splitter 2.

That is, it passes through the beam splitter 2 and passes through the objective lens 3.
The return light reflected by the disk 4 is reflected by the beam splitter 2 and enters the 2-split optical sensor 5.
This is a normal light beam to the split light sensor, but in addition to this, the outgoing light is reflected at point A and enters the 2-split light sensor 5 as stray light P1, reflected at point B, and further reflected at point 0. Stray light such as stray light P2 that is reflected and enters the two-split optical sensor 5 is generated. When these stray lights P , , P 2 are incident on the two-split optical sensor, an output from the two-split optical sensor will be generated even when the return light is zero. That is, as shown in FIG. 6, the amplitude center of the output of the two-split optical sensor when the returned light is incident on the two-split optical sensor deviates from the ground level (GND). That is, an offset δ occurs in the tracking error signal (two-split optical sensor output). When such an offset occurs, tracking control cannot be performed accurately.

The effect of the above offset on the tracking error signal is
In the case of playback-only optical disk devices such as compact discs (CDs), this is not a particular problem because the laser output of the light source is relatively small, but with write-once optical disk devices (
In the case of a disk device capable of recording, such as a DRAW (DRAW) or a magneto-optical disk device (MO), the effect of the offset of the tracking error signal can be ignored because during recording, a laser beam with a more precise and larger output is emitted than during playback. There was a problem that disappeared.

The present invention was made in view of the above circumstances, and mainly includes:
An object of the present invention is to reduce the influence of stray light on a tracking error detection optical sensor in an optical head of a recordable optical disk device.

Means for Solving Problem E] The method for adjusting the tracking error detection optical system of the present invention which solves the above problem firstly allows only stray light due to forward light generated by the beam splitter to enter the optical sensor for tracking error detection. In this state, adjust the position W1 of the optical sensor for tracking error detection so that the offset output of the optical sensor for tracking error detection becomes zero, and then make the return light from the disk enter the optical sensor for tracking error detection. The optical axis of the objective lens is adjusted by adjusting the movement of the entire objective lens actuator.

[Function] According to the above adjustment method, the return light that enters the optical sensor for tracking error detection during recording and playback includes stray light generated by the beam splitter; Since the ground level of the optical sensor for tracking error detection is taken in the state, the offset of the tracking error signal due to stray light is small.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to tjS1 diagram to Ptrls diagram. FIG. 4 shows the overall configuration of the optical system of the optical head of the embodiment. This optical head is an optical head for a magneto-optical disk capable of recording, reproducing, and erasing information.

Components common to those in FIG. 5 described above will be described with the same reference numerals. 1 is the aforementioned semiconductor laser; 6 is a collimator lens that converts the laser beam into a parallel beam; 7 is a shaping prism that makes the light beam a perfect circle; 2 is the tracking error; 7 is the aforementioned beam splitter for detecting orcusing error; 8 is a beam splitter for signal detection, 9 is 45°
10 is an objective lens actuator, 3 is the aforementioned objective lens, 11 is a 1/2 wavelength plate, 12 is a condenser lens, 13 is a polarizing beam splitter, and 14.15 is a signal detection optical sensor. Further, 16 is a condenser lens, 17 is a beam splitter, 5 is the aforementioned two-split optical sensor for tracking error detection, 18 is a cylindrical lens, and 19
is a 4-split optical sensor for detecting 7 orcasing errors; 0 or more is a general configuration.

FIG. 1 shows a plan view of the objective lens actuator 10,
Fig. 2 shows the front view, and Fig. fiS3 shows the left side view. In each figure, 21 is an objective lens holder to which the objective lens 3 is attached, and 22 is an actuator base that supports the objective lens holder 21 via a goomba of the illustrated path for maintaining a neutral point. And this actuator base 22
A holding member 2 is attached to the stand 23 on the side of the optical head main body, and the holding member 2 is tightened by one screw 24 at one end in the disk circumferential direction (left and right direction in FIG. 1) and by a fixing screw 25 at the other end.
It is fixed at 6. In this way, actuator base 2
2 is rotatably adjustable about the screw 24 on the one end side by loosening the screw 24 on the one end side and the screw 25 of the holding member 26 on the other end side.

Further, on the side of the holding member 26, there is provided a seven for driving the actuator base 22 around the screw 24.
A 94% drive 8+1 structure 27 is provided.

The adjustment drive mechanism 27 of this embodiment includes a member 28 vertically fixed to the holding member side portion 22a of the actuator base 22, a member 29 vertically fixed to the stand 23 on the optical head main body side, and both of the above-mentioned members 28, 29. A tension spring 30 connecting the W! By turning the four adjustment screws 31, the actuator base 22 can be driven for adjustment around the screw 24 at one end.

A method of adjusting the tracking error detection optical system of the optical head of the above vI configuration will be explained.

Now, it is assumed that each of the optical components shown in FIG. Since the JR adjustment of the tracking error detection optical system requires the most precision, the final adjustment is performed as follows.

First, when there is no return light from the disk, stray lights P9 and P2 are generated in the beam splitter 2, as shown in FIG.
Only 2 passes through the condenser lens 16 and beam splitter 17
The split light sensor 5 is irradiated.

In this state, move and adjust the 2-split optical sensor 5 in the direction of arrow (A) so that the output of the 2-split optical sensor 5 becomes zero, and then adjust the ? f
After 4 plating, the 2-split optical sensor 5 is fixed. In this way, the tracking error signal for stray light is brought to ground level.

After that, the screw 24 on one end side of the actuator base 22 is
, and the adjustment drive mechanism 27 is operated with the screw 25 on the other end side loosened to move the entire objective lens actuator 10 and adjust the optical axis of the objective lens 3. That is,
When the adjusting screw 31 is turned, the actuator base 22 rotates around the screw 24 at one end due to the pressing force of the adjusting screw 31 or due to the tensile force of the tension spring 30. In this way, the optical axis of the objective lens 3 that moves together with the actuator base 22 is moved and adjusted so that the irradiation of the returned light onto the two-split optical sensor 5, α, is at the center position of the two-split optical sensor 5. After adjusting the optical axis of the objective lens 3, one end of the actuator base 22 is fixed by tightening the screw 24, and the other end is fixed by the holding member 26 by tightening the h-shaft 25. With the above steps, the adjustment of the tracking error detection optical system is completed.

In the optical head in which the tracking error detection optical system is adjusted as described above, the return light incident on the two-split optical sensor 5 during recording and reproduction includes stray light generated by the beam splitter 2. As described above, since the ground level of the two-split optical sensor 5 is taken in the presence of stray light, the offset of the tracking error signal with respect to stray light is small.

In addition, the 7th floor that adjusts and drives the actuator base 22!
41! The specific mechanism of the driving rock structure 27 is not limited to that of the embodiment. In short, it is only necessary to adjust the two-split optical sensor 5 against stray light and then adjust the optical axis of the objective lens 3 with high precision.

Furthermore, although the present invention is particularly effective for recording/reproducing optical heads such as those for magneto-optical disks, it can also be applied to read-only optical heads if necessary.

[Effect of the Invention 1] As explained above, according to the adjustment method of the present invention, the position of the optical sensor for tracking error detection is adjusted in a state where only the stray light due to the forward light generated by the beam splitter is incident on the optical sensor for tracking error detection. After that, with the return light from the disk incident on the optical sensor for tracking error detection, the optical axis of the objective lens is aligned by adjusting the movement of the entire objective lens actuator. The offset of the tracking error signal due to stray light generated in the splitter has been reduced.

This makes it possible to perform more reliable tracking control even during recording in a recording/reproducing optical disc device.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an optical head showing an embodiment of the present invention, Fig. 2 is a front view thereof, Fig. 3 is a left side view thereof, Fig. 54 is an overall configuration diagram of the optical system, and Fig. 5 is a stray light. An explanatory diagram about
FIG. 6 is an explanatory diagram of the influence of stray light. 2... Beam splitter, 3... Objective lens, 5...
・・2-split optical sensor (optical sensor for tracking error detection), 10 ・Objective lens actuator, 22 ・・
- Actuator base, 23... Optical head main body side stand, 24... Screw, 25... Screw, 26... Holding member, 27... Adjustment drive mechanism.

Claims (1)

[Claims] Adjust the position of the optical sensor for tracking error detection so that the offset output of the optical sensor for tracking error detection becomes zero in a state where only the stray light from the forward light generated by the beam splitter is incident on the optical sensor for tracking error detection, A tracking error detection optical system for an optical head, characterized in that the optical axis of the objective lens is adjusted by adjusting the movement of the entire objective lens actuator while the return light from the disk is incident on the optical sensor for tracking error detection. Adjustment method.