JP2002251777A - Method of inspecting characteristic of optical head and method of correcting variation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect the characters of an optical head and the correct the variations in the characteristics of the optical pickup among the devices. SOLUTION: The RF signals of a reference ROM disk 20 having bit patterns for spot measurement are read out and these RF signals are analyzed, by which the light intensity distribution, spot diameter, etc., of an optical pickup 11 are digitized and the characteristics of the optical pickup 11 are recognized. In addition, the variations in the characteristics of the optical pickup among the devices are corrected based on the digitized light intensity distribution, spot diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head characteristic inspection method and a variation correction method.

[0002]

2. Description of the Related Art Conventionally, there is an optical disk inspection apparatus as an apparatus for evaluating various characteristics (reflectance, signal intensity, error rate, recording sensitivity, etc.) of an optical disk.

Generally, an optical disk inspection apparatus irradiates a laser beam from an optical head onto an optical disk to record and record signals.
By performing reproduction, the characteristics of the optical disk are inspected. Then, only optical disks that pass this inspection are shipped.

[0004]

However, in this optical disk inspection apparatus, there is a problem in the performance of the optical head mounted on the optical disk inspection apparatus.

In particular, if the light intensity distribution and the spot diameter of the laser light emitted from the optical head vary, the measurement results such as the recording sensitivity and the reflectance of the optical disk cannot be correct.

In a normal optical disk recording / reproducing apparatus, the spot diameter and light intensity of a beam spot formed on an optical disk by a laser beam due to a difference in the characteristics of the mounted optical head (such as the state of attachment to the optical system and the apparatus). When the distribution varies, the recording characteristics and reproduction characteristics of the optical disk recording / reproducing apparatus vary.

It is an object of the present invention to provide a method of inspecting characteristics of an optical head and correcting the variations, which can individually grasp the quality of laser light emitted from the optical head and correct variations between the optical heads. Aim.

[0008]

In order to achieve the above-mentioned object, a method for inspecting characteristics of an optical head according to the present invention is provided for an optical information recording / reproducing apparatus for irradiating an optical information recording medium with laser light. In the characteristic inspection method, the spot diameter and the light intensity distribution of the laser light are quantified, and the quantified spot diameter and the light intensity distribution are compared with a preset reference value. If it is within a predetermined margin including the reference value,
The optical system of the optical head and the state of attachment of the optical head to the optical information recording / reproducing apparatus are determined to be properly adjusted.

According to such a configuration, the optical system of the optical head and the mounting state thereof can be inspected and grasped while the optical head is mounted on the optical information recording / reproducing apparatus.

[0010] Here, the optical information recording / reproducing apparatus includes an optical recording medium inspection apparatus.

The method of correcting variations in an optical head according to the present invention is a method for correcting variations in the characteristics of an optical head mounted on an optical information recording / reproducing apparatus and irradiating an optical information recording medium with laser light. In, the spot diameter and light intensity distribution of the laser light are digitized,
The digitized spot diameter and light intensity distribution are compared with a preset reference value, and if the digitized spot diameter and light intensity distribution fall within a predetermined margin including the reference value, the optical head It is determined that the state of attachment of the optical system and the optical head to the optical information recording / reproducing apparatus has been properly adjusted, and the digitized spot diameter and light intensity distribution are stored for each optical head. 1 remembered
Two optical heads as a reference, a spot diameter and a light intensity distribution in the well-adjusted state of the optical head with the reference as a reference value, a spot diameter in the well-adjusted state of another optical head and It is characterized in that the light intensity distribution is corrected.

According to such a configuration, variations in the characteristics of the optical head mounted on the optical information recording / reproducing device, that is, variations in the recording characteristics or reproducing characteristics between the optical information recording / reproducing devices can be easily grasped. It becomes possible to correct.

Incidentally, recording compensation or reproduction compensation can be used for the correction.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for inspecting characteristics of an optical head and correcting a variation according to the present invention will be described below in detail with reference to the accompanying drawings.

An example in which the method for inspecting the characteristics of an optical head and the method for correcting variations according to the present invention are applied to an optical disk inspection apparatus will be described.

FIG. 1 is a block diagram showing a partial configuration of an optical disk inspection apparatus according to the present invention.

In FIG. 1, when an optical disc 20 is inserted from a disc insertion slot (not shown), the optical disc inspection apparatus rotates the optical disc 20 at a constant linear velocity by a spindle motor 18 and reproduces information on the optical disc 20 by an optical pickup 11. I do.

The rotation speed of the optical disk 20, that is, the rotation speed of the spindle motor 18 is detected by a frequency signal generator (FG) 19 and managed by the controller 10.

The signal read from the optical disk 20 is
The focus error (FE) signal and the tracking error (TE) signal, which are amplified by the head amplifier 12, are input to a focus / tracking control circuit 14 and used for focus control and tracking control of the optical pickup 11.

Further, the read signal amplified by the head amplifier 12 is input to a read signal processing circuit 13, which reads absolute time information ATIP (AT) as recording position data from the input read signal. Is extracted.

The absolute time information ATIP extracted by the read signal processing circuit 13 is a CLV (Constant Linear Velocit).
y) The signal is input to the control circuit 16, and the CLV control circuit 16
The rotation of the spindle motor 18 is controlled at a constant linear speed based on the input absolute time information ATIP.

The optical pickup 11 has a focus control function and a tracking control function. The focus control function and the tracking control function are controlled by a focus / tracking control circuit 14.

The optical pickup 11 is configured to be movable in the radial direction of the optical disk 20 by a feed motor 17.
Is controlled by

FIG. 2 is a flowchart for explaining an example of the operation of measuring the light intensity distribution and spot diameter of the laser light emitted from the optical pickup 11 in the optical disk inspection apparatus shown in FIG.

When the reference ROM disk 20 is inserted into the optical disk inspection device, the feed control circuit 15
7 to move the optical pickup 11 to just below a predetermined position of the reference ROM disk 20 (step 10).
1).

The reference ROM disk may be an optical disk having a clear characteristic, for example, in which the size and arrangement of pits formed on the disk are specified, and therefore, an optical disk having the same specifications as a normal CD-ROM or the like. Can be used.

Next, under the control of the focus / tracking control circuit 14, the optical pickup 11
The laser beam is appropriately focused on the head of the spot measurement pit pattern recorded on the M disk 20 to start reading the RF signal (step 10).
2).

Here, the spot measurement pit pattern is a pit pattern in which pits longer than the expected spot diameter of the laser beam are formed at intervals longer than the expected spot diameter, and the pit pattern is a reference ROM disk. 20 may be recorded in a predetermined area in advance, or if this condition is satisfied, the reference ROM disk 2
It is also possible to use a pit recorded on an arbitrary recording track of 0.

The RF signal corresponding to the spot measurement pit pattern read from the reference ROM disk 20 is:
The signal is input to the head amplifier 12 and also directly to the controller 10.

The controller 10 first receives the input R
A differentiated waveform is generated by differentiating the F signal (step 10).
3) Extract a differential waveform corresponding to the edge waveform of the RF signal from the generated differential waveform (step 104).

Here, since two differential waveforms corresponding to the front edge and the rear edge are extracted from the RF signal corresponding to one pit, the number of differential waveforms is twice the number of pits of the entire spot measurement pit pattern. Is extracted, thus
The extracted differential waveform is averaged and used for the next processing.

As a method of averaging the differential waveform,
The following three methods are applicable.

1) Only the differential waveform corresponding to the leading edge is averaged.

2) Only the differential waveform corresponding to the trailing edge is averaged.

3) Averaging is performed using both the differentiated waveform corresponding to the leading edge and the differentiated waveform corresponding to the trailing edge.

Since the polarity of the differentiated waveform corresponding to the trailing edge is reversed, the waveform of the absolute value is averaged.

Next, the controller 10 detects, for example, two points having a value of 1 / e2 of the peak value of the differential waveform, obtains the time between the detected two points, and calculates the time between the two points. The effective spot diameter of the laser beam emitted from the optical pickup 11 is calculated based on the rotation speed of the reference ROM disk 20 obtained from the FG 19. Further, from the differential waveform, not only the effective spot diameter of the laser beam but also the light intensity distribution of the laser beam can be obtained (step 1).
05).

According to the present invention, the characteristics of the optical pickup (mainly, spot quality such as the spot diameter and light intensity distribution of the emitted laser beam) are grasped for each optical disc inspection apparatus.
Further, it is possible to perform a fair optical disk inspection by correcting variations in characteristics of the optical pickup between the optical disk inspection devices.

First, a method of inspecting the characteristics of the optical pickup for each optical disk inspection apparatus will be described.

FIG. 3 is a flowchart illustrating a method for inspecting and grasping the characteristics of the optical pickup according to the present invention.

When the reference ROM disk 20 is mounted on the optical disk inspection apparatus, the optical pickup 11 emits a laser beam, irradiates the reference ROM disk 20, and reads out an RF signal (step 201).

The read RF signal is analyzed by the above-described method, and the spot diameter and light intensity distribution of the laser beam are digitized from the analysis result (step 202).

If the digitized spot diameter and light intensity distribution are within a predetermined margin by comparing with a preset reference value (YES in step 203), the optical pickup 11 is adjusted well. Judge that
The spot diameter and the light intensity distribution are determined by the optical pickup 11.
Are stored in a predetermined storage area of the optical disk inspection apparatus (step 204).

On the other hand, if the digitized spot diameter and light intensity distribution do not fall within a predetermined margin as compared with a preset reference value (NO in step 203), the optical pickup is insufficiently adjusted. And an instruction for readjustment is issued (step 205).

The adjustment of the optical pickup includes various factors such as adjustment of an optical system including an objective lens and the like, and adjustment of an attachment angle to an optical disk inspection device. If it is optimal, the spot diameter of the emitted laser beam becomes minimum, and its light intensity distribution becomes a concentric intensity distribution with a peak at the center.

Next, a method of correcting variations in the characteristics of the optical pickup between the optical disk inspection apparatuses will be described.

Normally, a plurality of inspection devices are used for inspection of an optical disk such as a CD-ROM. However, if there is a variation among the inspection devices, it is difficult to perform a constant evaluation. Therefore, by grasping the characteristics of the optical pickup for each inspection device by the above-described method, quantifying the variation in the characteristics of the optical pickup between the inspection devices, and applying a correction by a strategy adjustment, an equalizer, or the like, the same condition can be obtained. Inspection of the optical disk can be performed fairly.

FIG. 4 is a flow chart for explaining a method for correcting variations in the characteristics of the optical pickup according to the present invention.

First, a plurality of optical disk inspection devices A, B,
The characteristic unique to the optical pickup of each of the optical pickups C is quantified by the above method (step 301).

Next, for example, using the characteristics of the optical pickup of the inspection device A as a reference value, the characteristics are compared with the characteristics of the optical pickups of the inspection devices B and C (step 302), and the variation is quantified (step 303).

Based on the quantified variation, the recording compensation amount and the reproduction compensation amount in the inspection devices B and C are determined so that the conditions are equal to those of the inspection device A (step 3).
04, 305).

The inspection apparatuses B and C control the optical pickup based on the determined recording compensation amount and reproduction compensation amount, so that the three inspection apparatuses A, B and C can perform the same evaluation with correlation. Will be possible.

The method of inspecting the characteristics of the optical pickup and the method of correcting the variation according to the present invention have been described above by taking the optical disk inspection apparatus as an example.
The present invention can also be applied to a general optical disk recording / reproducing device.

Further, in the present invention, the method for specifying the spot diameter and light intensity distribution of the laser beam performed when inspecting the characteristics of the optical pickup is not limited to the above method.

[0055]

As described above, according to the present invention, it is possible to control the optical pickup appropriately for each device by grasping the characteristics of the optical pickup.
By grasping and correcting the variation in the characteristics among the devices, there is an effect that the recording / reproducing and the inspection of the optical disk can be performed under the same condition regardless of the individual difference.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an optical disk inspection apparatus according to the present invention.

FIG. 2 is a flowchart illustrating an example of a method for measuring a laser beam spot diameter and light intensity distribution.

FIG. 3 is a flowchart showing an optical pickup characteristic inspection method according to the present invention.

FIG. 4 is a flowchart showing a method for correcting variations in characteristics of an optical pickup between inspection apparatuses according to the present invention.

[Explanation of symbols]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Isao Matsuda 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. (72) Inventor Shino Sekiguchi 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. F-term (reference) 5D117 AA02 CC07 KK03 KK04 KK18 5D119 AA50 BA01 PA05

Claims (2)

[Claims] 1. A method for inspecting characteristics of an optical head mounted on an optical information recording / reproducing apparatus and irradiating an optical information recording medium with laser light, wherein the spot diameter and light intensity distribution of the laser light are digitized, The spot diameter and the light intensity distribution are compared with a preset reference value, and if the digitized spot diameter and the light intensity distribution fall within a predetermined margin including the reference value, the optical system of the optical head and the optical system A method for inspecting characteristics of an optical head, characterized in that it is determined that an attachment state of the optical head to the optical information recording / reproducing apparatus has been adjusted properly. 2. A method for correcting variations in characteristics of an optical head mounted on an optical information recording / reproducing apparatus and irradiating an optical information recording medium with laser light, comprising: a spot diameter and a light intensity of the laser light. Numericalize the distribution, compare the digitized spot diameter and light intensity distribution with a preset reference value, and if the digitized spot diameter and light intensity distribution fall within a predetermined margin including the reference value The optical system of the optical head and the state of attachment of the optical head to the optical information recording / reproducing apparatus are determined to be properly adjusted, and the digitized spot diameter and light intensity distribution correspond to each optical head. A spot diameter and a light intensity distribution in the well-adjusted state of the reference optical head based on the stored one optical head. As a reference value, variation correction method of optical head and correcting the spot diameter and light intensity distribution in the well-adjusted state of the other optical head.