JP2000082222A - Optical pickup inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup inspection method improving precision in the characteristic inspection of an optical pickup by stabilizing the detection of a measuring signal. SOLUTION: In this method, by imparting a drive current to a tracking coil driving an objective lens 21 along the radial direction Tr1 of an optical disk, a tracking servo is performed for a track formed on the optical disk, a regenerative signal is detected and the inspection of an optical pickup inspecting the on-track characteristic of the optical pickup 20 is performed based on the regenerative signal. In such a case, the prescribed drive current is sent to the tracking coil, only the objective lens 21 is finely moved in the radial direction Tr1 of the optical disk, the regenerative signal is detected and the on-track characteristic of the optical pickup 20 is inspected based on the regenerative signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical pickup inspection method, and more particularly, to an optical pickup inspection method capable of inspecting an optical pickup with high accuracy.

[0002]

2. Description of the Related Art An optical pickup is used for reproducing an optical disk such as a compact disk and a digital video disk. This optical pickup reads information by irradiating a recording surface of an optical disk with laser light and detecting return light reflected from the recording surface of the optical disk. FIG. 6 is a schematic diagram showing a recording surface of a general optical disk. An optical disk D has a recording track which is a set of recording pits as shown in FIG. In some cases, tracks as shown in FIG. 6B are formed concentrically on the recording surface.

FIG. 7 is a schematic diagram showing an example of a portion around an optical pickup in a general optical disk device.
The optical disk inspection device 1 will be described with reference to FIG. 7 includes an optical pickup 2, a turntable 3, a signal processing unit 4, and a thread mechanism 5.
The optical pickup 2 has an objective lens 6,
It has a biaxial actuator 7 and the like. The turntable 3 holds the optical disk D so as to be rotatable in the direction of arrow R1, and the turntable 3 is mechanically connected to a spindle motor (not shown). Recording surface D1 of optical disk D
An optical pickup 2 is arranged on the side. The optical pickup 2 is held by a sled mechanism 5 and moves in the tracking direction Tr (radial direction of the optical disc) when the sled mechanism 5 operates.

The optical pickup 2 irradiates the recording surface D1 with laser light, and the laser light emitted from a light source (not shown) is condensed by the objective lens 6 and irradiated on the recording surface D1. The objective lens 6 is held by a biaxial actuator 7. The objective lens 7 is held by the biaxial actuator 7 so as to be finely movable in a tracking direction Tr and a focus direction Fr which is a direction along an optical axis orthogonal to the tracking direction Tr. I have.

[0005] FIG. 8 is a schematic diagram showing a state in which the optical pickup 2 is inspected. A conventional optical pickup inspection method will be described with reference to FIGS. 7 and 8. First, FIG.
Is disposed on the turntable 3 and rotates in the direction of the arrow R1. Then, the optical pickup 2 performs tracking servo from the inner circumferential surface side of the recording surface D1 to the outer circumferential surface side (in the direction of the arrow Tr1) to reproduce information recorded on the optical disc D. Then, the on-track performance of the optical pickup 2 is inspected based on the obtained reproduction signal.

More specifically, first, as shown in FIG. 8A, the optical pickup 2 is positioned on the inner peripheral surface side of the optical disk D by the sled mechanism 5. Then, the optical pickup 2 irradiates the recording surface D1 of the optical disk D with laser light to obtain a reproduction signal of the recording surface P1. And FIG.
As shown in (B), the operation of the biaxial actuator 7 causes the objective lens 6 to slightly move in the tracking direction Tr1,
A reproduction signal on the recording surface P2 is obtained.

[0008] Thereafter, as shown in FIG. 8 (C), the objective lens 6 is further finely moved in the tracking direction Tr 1 by the biaxial actuator 7 to acquire a reproduction signal at the position P 3 of the recording surface D 1. Then, as shown in FIG.
The operation of the thread mechanism 5 causes the optical pickup 2 to move in the track direction Tr1, and at the same time, the objective lens 6
It slightly moves in the r2 direction and returns to the original position. By repeating this operation, a reproduced signal is detected while following a track formed in a spiral or concentric shape. Then, the on-track characteristic of the optical pickup 2 is inspected based on the reproduced signal.

FIG. 9 shows the driving current V2 supplied to the biaxial actuator 7 and the driving current V supplied to the sled mechanism 5.
FIG. In FIG. 9, when the track jump is performed by the biaxial actuator 7, the drive current V2 is not supplied to the sled mechanism 5. When the drive current V2 is supplied to the sled mechanism 5, the drive current V1 supplied to the biaxial actuator 7
Decreases. The timing at which the drive current V1 is supplied to the sled mechanism 5 is, for example, 50 tracks to 10 tracks.
Track jump of 0 track is biaxial actuator 7
After that, it is supplied to the thread mechanism 5.

[0009]

As shown in FIG. 8D, when the optical pickup 2 is moving in the track direction Tr1 by the sled mechanism 5, the biaxial actuator 7 moves the objective lens 6 in the direction of the arrow Tr2. It is moving.
That is, the sled mechanism 5 is driven at the same time as the two-axis actuator 7 is driven. At this time, the thread mechanism 5
In some cases, the sled mechanism 5 may be delayed due to an error in the mechanical movement distance, electric offset, or the like. For this reason,
Data may be measured in a state where the objective lens 6 is shifted (shifted) from the optical axis of the light source by 100 tracks or more. Therefore, the measured reproduction signal becomes unstable, and there is a problem that it is not possible to perform a characteristic test of the optical pickup with high accuracy.

That is, when the sled mechanism 5 moves the optical pickup 2 for positioning, the sled mechanism 5 sometimes moves too far or sometimes delays. The error of the thread mechanism 5 is absorbed by moving the objective lens 6 by the biaxial actuator 7. However, when the objective lens 6 moves, the objective lens 6 is deviated from the optical axis of the light source, and there is a problem that quantitative evaluation cannot be performed. Further, strictly speaking, the level and jitter of the signal recorded on the optical disc D vary depending on the position. For this reason, there is a problem that the track position of the optical disc D read by the optical pickup 2 is different for each measurement, resulting in a variation in evaluation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical pickup inspection method capable of solving the above-mentioned problems and stabilizing the detection of a measurement signal, thereby improving the accuracy in the characteristic inspection of the optical pickup. .

[0012]

According to the first aspect of the present invention, a drive current is applied to a tracking coil for driving an objective lens along a radial direction of an optical disk, thereby forming the optical disk on the optical disk. A tracking servo is performed on a track to detect a reproduction signal, and based on the reproduction signal, an optical pickup inspection method for inspecting an on-track characteristic of the optical pickup, wherein a predetermined drive current is sent to the tracking coil, By finely moving only the objective lens in the radial direction of the optical disc,
This is achieved by an optical pickup inspection method for detecting a reproduction signal and inspecting the on-track characteristics of the optical pickup based on the reproduction signal.

According to the first aspect of the present invention, when detecting a reproduction signal, the optical pickup is not moved, and only the objective lens is slightly moved in the tracking direction to perform tracking servo. As a result, the displacement of the optical disk and the displacement of the optical pickup caused by the movement of the optical pickup are eliminated, the optical displacement is eliminated, and a stable inspection of the optical pickup becomes possible.

According to a second aspect of the present invention, the above object is attained by an optical pickup inspection method in which the plurality of tracks are ten tracks. According to the configuration of the second aspect, by performing the measurement in units of ten tracks, fluctuations in the level and jitter of the reproduction signal due to deviation from the optical axis of the light source of the objective lens are eliminated, and quantitative evaluation can be reliably performed. it can.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 is a diagram showing an example of the configuration of an optical disk device inspected by the optical pickup inspection method of the present invention. The optical disk device 10 will be briefly described with reference to FIG. In FIG. 1, an optical disk device 10 includes:
The optical disc D includes a spindle motor 12 as a rotation driving unit for driving the optical disc D to rotate, an optical pickup 20 and the like. The spindle motor 12 is connected to a turntable 12a, and when the spindle motor 12 operates, the turntable 12a rotates. The optical disk D is held on the turntable 12a, and the optical disk D rotates in synchronization with the rotation of the turntable 12a.

The optical pickup 13 irradiates a laser beam onto the signal recording surface of the rotating optical disk 11 to record a signal, or detects a return light from the signal recording surface to detect a signal. A reproduction signal RF based on the return light is output to the device 15. Thus, the reproduction signal RF demodulated by the signal demodulator 15 is output to the error correction circuit 1
The error is corrected through the interface 6 and transmitted to an external computer or the like via the interface 17. The external computer or the like converts the signal recorded on the optical disc D into a reproduction signal RF.
You can receive as.

FIG. 2 is a schematic perspective view of the optical disk device 10, and the thread mechanism 18 will be described in detail with reference to FIG. The thread mechanism 18 of FIG.
And the gear 32, and the rack 31 and the gear 32 are engaged with each other. The rack 31 is arranged to extend along the radial direction of the optical disc D. The optical pickup 20 is fixed to the rack 31, and the optical pickup 20 moves in the direction of the arrow Tr together with the rack 31. When the gear 32 rotates, the rack 31 moves in the direction of the arrow Tr, and the optical pickup 20 can be moved to a position where the track jumps.

FIG. 3 is a schematic view showing a portion around the optical pickup 20 of FIG. 2. The optical pickup 20 will be described in detail with reference to FIG. The optical pickup 20 in FIG. 3 includes an objective lens 21, a biaxial actuator 22 having a tracking coil, and the like. The objective lens 21 transmits the laser beam emitted from the light source to the optical disc D
At a predetermined position. The objective lens 21 is held by a biaxial actuator 22, and the operation of the biaxial actuator 22 causes the objective lens 21 to move in the focusing direction Fr and the tracking direction T.
Move to r. The two-axis actuator 22 includes, for example, a tracking coil and a magnet. When a drive current is applied to the tracking coil, a magnetic field is generated from the coil. The objective lens 21 can move in the focusing direction Fr and the tracking direction Tr by the magnetic field generated by the tracking coil and the magnetic field of the magnet.

FIG. 4 is a flow chart for inspecting the characteristics of the optical pickup 20 of the optical disk device 10. Referring to FIGS.
The inspection method will be described in detail. First, the optical pickup 20 of FIG. 3 is previously positioned at a predetermined position of the optical disk D, for example, at the inner peripheral surface side. Then, the biaxial actuator 22 is operated by the predetermined drive current V11, and the objective lens 21 is fed in the direction of the arrow Tr1 until the track number n becomes, for example, 10 tracks (S2). The number n of tracks can be detected from a reproduction signal RF or a tracking error signal described later. The number of tracks n is set to 10 for the following reason.

For example, when the optical disk D is a compact disk, the track pitch of the tracks formed on the recording surface D1 is 1.6 μm, so that the length of 10 tracks is about 16 μm. If it is about 16 μm, an unstable element in measuring the reproduction signal RF caused by the optical axis shift of the laser beam can be eliminated, and the measured value of the reproduction signal RF can be stabilized. That is, the optical axis shift of the objective lens 21 is eliminated, and the on-track performance of the optical pickup 20 can be accurately inspected.

Thereafter, by performing tracking servo on a predetermined track (S3), a reproduction signal RF is detected (S4). By measuring the jitter and signal level of the reproduced signal RF, the on-track characteristics of the optical pickup 20 are inspected (S5). When a reproduction signal RF in a predetermined track is detected, the objective lens 2
1 stops the tracking servo (S6), and returns to the original position by performing a track jump (S7). Thus, the inspection of the on-track characteristics of the optical pickup 20 is completed. Here, the track jump means moving the track position reproduced by the optical pickup 2 in the direction of the arrow Tr2.

Then, the above-described inspection of the same optical disk D is performed on another optical pickup 20. When inspecting this other optical pickup 20, for example, 1
The tracking servo is performed only by driving the objective lens 21 for the zero track to check the on-track characteristics. As a result, since the same track is surely reproduced as a track reproduced when inspecting the plurality of optical pickups 20, it is possible to eliminate a variation in evaluation and perform an inspection with high reproducibility.

FIG. 5 is a graph showing the waveforms of the driving current V11 for driving the biaxial actuator 22 and the reproduction signal RF. In FIG. 5A, the drive current V11 is formed in a saw-tooth waveform, and its cycle T is set to a size that enables tracking servo for, for example, 10 tracks. The drive current V11 causes 2
The axis actuator 22 is driven to perform tracking servo. The reproduced signal RF detected by the tracking servo is shown in FIG.

In FIG. 5B, the reproduction signal RF is composed of a capture area and a mute area. The capture area is operated while the drive current V11 of FIG. 5A is supplied, that is, the tracking servo operates. Is the area while you are. On the other hand, the mute area means a signal area acquired when the objective lens 21 is performing a track jump, that is, when the detection of the reproduction signal is stopped.

According to the above embodiment, the tracking servo is performed only by the operation of the biaxial actuator 22 to stop the detection of the reproduction signal RF, so that the characteristic inspection of the optical pickup 20 can be accurately performed. That is, it is possible to perform quantitative and highly reproducible evaluation by eliminating factors of unstable characteristics due to the position of the optical disk to be evaluated and the deviation of the optical axis. In addition, tracking servo is performed, for example, for only 10 tracks, and thereafter, the objective lens 21 returns to the original position. If the number of tracks is approximately 10, the optical axis shift of the objective lens 21 is not at a problematic level. Will be possible.

The present invention is not limited to the above embodiment. The tracking servo is performed, for example, in units of 10 tracks. The number n of tracks is determined from the track pitch of the optical disk D and the optical axis shift characteristics of the optical pickup 10, and varies depending on the optical pickup to be inspected. . Although the thread mechanism 22 in FIG. 2 includes the rack 31 and the gear 32, the thread mechanism 22 may include a linear motor using a magnet and a coil. In addition, this optical pickup inspection method,
For example, an optical pickup for a magneto-optical disk or a DVD
The present invention can be applied to the inspection of an optical pickup for a high-density recording optical disk such as a (digital video disk) and an optical pickup capable of recording and reproducing.

[0028]

As described above, according to the present invention,
By stabilizing the detection of the reproduction signal, it is possible to improve the accuracy in the characteristic inspection of the optical pickup.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of an optical disk device inspected by an optical pickup inspection method of the present invention.

FIG. 2 is a schematic perspective view showing an example of an optical disk device inspected by the optical pickup inspection method of the present invention.

FIG. 3 is a schematic diagram showing an example of an optical pickup in an optical disk device inspected by the optical pickup inspection method of the present invention.

FIG. 4 is a flowchart showing a preferred embodiment of the optical pickup inspection method of the present invention.

FIG. 5 is a graph showing a waveform of a reproduced signal or the like in the optical pickup inspection method of the present invention.

FIG. 6 is a schematic diagram showing a state in which tracks are formed on a recording surface of a general optical disk.

FIG. 7 is a schematic view showing a peripheral portion of a conventional optical pickup.

FIG. 8 is a schematic view showing a state where a conventional optical pickup inspects an optical disk.

FIG. 9 is a graph showing a waveform of a drive current supplied in a conventional optical pickup inspection method.

[Explanation of symbols]

10 ... optical disk device, 18 ... thread mechanism,
20: Optical pickup, 21: Objective lens,
22: two-axis actuator, D: optical disk,
D1: recording surface, RF: reproduction signal.

Claims (2)

[Claims] 1. A drive signal is supplied to a tracking coil for driving an objective lens along a radial direction of an optical disk, a tracking servo is performed on a track formed on the optical disk, and a reproduction signal is detected. In an optical pickup inspection method for inspecting an on-track characteristic of an optical pickup based on a signal, a predetermined drive current is sent to the tracking coil, and only the objective lens is slightly moved in a radial direction of the optical disc, and a reproduction signal is obtained. An optical pickup inspection method comprising: detecting and detecting an on-track characteristic of an optical pickup based on the reproduced signal. 2. The optical pickup inspection method according to claim 1, wherein a feed amount of the objective lens for finely moving the objective lens is approximately 10 tracks.