JPH01206209A - Checking apparatus of optical information storage medium - Google Patents

Abstract

PURPOSE:To enable the continuous checking of an acceleration of an optical information storage medium, by a method wherein an information on the amount of displacement of the optical information storage medium is subjected to an analytical processing at a high speed by using an algorithm of Fourier transform. CONSTITUTION:A measuring device 49 has a control circuit element for moving an optical head 9 in a proper amount so that a laser light be focused exactly on a prescribed spot of an optical disk in relation to the plane vibration, warp and others of the optical disk 1, and a displacement amount detecting circuit element. The measuring device 49 transmits various informations on the amount of displacement of the optical disk 1 to an arithmetic processing device 51. A frequency analyzer 57 determines, for each frequency, a value of the maximum acceleration out of values of accelerations for each frequency of the amount of displacement of the optical disk 1, and delivers this information to a comparator 59. The comparator 59 compares a reference value of accelerations for each frequency set beforehand with said value corresponding to each frequency, and delivers the result of this comparison to a computation display element 55. In the computation display element 55, the result of the comparison is displayed in a graph.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention relates to an inspection device for inspecting optical information storage media such as optical disks, and in particular, to an inspection device for inspecting optical information storage media such as optical disks, and in particular to an inspection device for inspecting optical information storage media by using a Fourier transform algorithm. The present invention relates to an optical information storage medium inspection device that analyzes the amount of displacement of the medium at high speed.

(Prior Art) In recent years, optical information storage media such as optical disks have been widely used in image information storage and retrieval devices, music or video playback devices, and the like. This optical disk is subjected to various quality inspections at the final stage of the manufacturing process using an optical information storage medium inspection device or the like, for example, inspection regarding physical characteristics such as surface runout and warpage.

Such a conventional optical information storage medium inspection device is equipped with a spindle motor that rotates an optical disk, which is an optical information storage medium, at a constant speed, and further performs tracking servo control and focusing servo control to control the rotation of this optical disk. The optical head section is provided with an optical head section that is displaceable to follow accompanying displacements such as surface blurring, and is movable in the radial direction of the optical disk by a moving means such as a feed motor.

When measuring the physical characteristics of an optical disk, such as surface blur or warping, the moving means is driven to position the optical head section at a specific measurement point in the radial direction of the optical disk, and the optical head is moved to this specific measurement point. The optical disc is rotated with the part positioned in the position, and the amount of displacement accompanying the rotation of the optical disc is measured. When the measurement of the amount of displacement at this specific measurement point is completed, the moving means is driven to move the optical head to the next measurement point, and the optical disk is moved with the optical head positioned at the next measurement point. Measure the amount of displacement associated with rotation.

Similarly, the optical head section is sequentially moved to specific measurement points set in the radial direction of the optical disk, and the amount of displacement of the rotating optical disk is measured with the optical head section positioned at this specific measurement point. Physical properties were being examined.

(Problem to be Solved by the Invention) In the conventional inspection of optical information storage media, for example, 2048 measurement points are set, and the 2048
Because information on the amount of displacement corresponding to each measurement point was processed using a microcomputer, etc., when calculating the amount of displacement such as surface runout of an optical information storage medium and the acceleration of these displacements. For example, it takes about 5 to 10 minutes to perform the inspection, and when the above inspection is performed during the production process, the inspection time is long and it is not practical.

The present invention has been made in view of the above, and it is possible to quickly analyze and process the amount of displacement such as surface runout of an optical information storage medium and the physical characteristics such as the acceleration of this amount of displacement, thereby reducing the inspection time of the optical information storage medium. An object of the present invention is to provide an optical information storage medium inspection device that can shorten the time required.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention measures the physical characteristics of an optical information storage medium based on the displacement detected from the optical information storage medium. The present invention is characterized in that the testing device is equipped with an analysis processing means that performs testing processing based on a Fourier transform algorithm when testing the physical characteristics.

(Operation) The optical information storage medium inspection device of the present invention first detects displacement of the optical information storage medium. When calculating various physical characteristics from the amount of displacement of the optical information storage medium, by using an analysis processing means based on the Fourier transform algorithm, the amount of displacement such as surface blur of the optical information storage medium and the amount of this displacement are calculated. The acceleration and the like of the optical information storage medium are quickly processed to quickly test the physical characteristics of the optical information storage medium.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

First, a schematic configuration of an optical information storage medium inspection apparatus to which the present invention is applied will be described with reference to FIG.

An optical disk 1, which is an optical information storage medium to be inspected, is placed on a spindle motor 3, and the spindle motor 3 is driven to rotate at a constant speed, for example, 600 rpm, thereby rotating the optical disk 1 at a constant speed. .

On the other hand, an optical head 9 and various optical systems are arranged on a base 7 that is movable by a feed motor 5. The laser head 11 outputs a laser beam for displacement measurement, for example, a parallel beam of He-Ne laser beam. When the beam splitter 13 receives the laser beam from the laser head 11, it equally distributes it in two directions and outputs it. One of the laser beams split by this beam splitter 13 is sent to an interferometer 15. Lens 17. The light is applied to the optical head 9 via total reflection prisms 19a and 19b. The incident light P1 that has entered the optical head 9 in this way is as shown in FIG.
A total reflection mirror 23 attached to a predetermined position of the optical head 9
reflected.

The reflected light reflected by this total reflection mirror 23 passes through the total reflection prisms 19b and 19a lenses 17 again to the interferometer 1.
Proceed to step 5. In the interferometer 15, the reflected light reflected by the total reflection mirror 23 and the laser light from the laser head 11 which is incident via the beam splitter 13 are caused to interfere with each other. The light receiver 25 receives the interference light from the interferometer 15 and outputs a displacement signal of the optical head 9, that is, a signal corresponding to the eccentric displacement of the optical disk 1 in the radial direction.

The other laser beam distributed by the beam splitter 13 passes through a total reflection mirror 33. Interferometer 35. The light is applied to the optical head 9 via the lens 37 and the total reflection prism 19C.

As shown in FIG. 3, the incident light P2 that has entered the optical head 9 in this manner is vertically raised by a total reflection blob 41 disposed at a predetermined position of the optical head 9, and then further reflected by a total reflection mirror 43. reflected. The reflected light reflected by the total reflection mirror 43 passes through the total reflection prisms 41 and 19C and the lens 37 again and travels to the interferometer 35. Interferometer 3
5, the reflected light reflected by the total reflection mirror 43 and the laser light from the laser head 11 which is incident via the total reflection mirror 33 and the beam splitter 13 are caused to interfere with each other. The light receiver 45 receives the interference light from the interferometer 35 and outputs a displacement signal of the optical head 9, that is, a signal corresponding to the displacement of the surface runout in the direction of the rotation axis of the optical disk 1. Further, the resolution of the interferometer 35 and the interferometer 15 is set to, for example, about 1/64 or 1/128 of the wavelength of light, respectively.

Next, referring to FIG. 1, an inspection method according to the present invention will be explained together with an optical information storage medium inspection apparatus.

As shown in FIG. 1, an optical disk 1 placed on a spindle motor 3 is formed into a disk shape with a diameter of 130 mm. Further, this optical disc 1 has spiral grooves formed on both the front and back sides of the optical disc 1. The depth of this groove is a value that is sufficiently smaller than the amount of displacement such as deformation or warpage of the optical disc 1 to be measured. Further, the spindle motor 3 rotates at a constant rotation speed within the range of 300 to 3600 rpm, thereby rotating the optical disc 1 at a constant speed. Further, the feed motor 5 moves the optical head 9 by moving the base 7 at a constant speed within the range of, for example, o, oi to 101RIl for one second.
is moved in the radial direction of the optical disc 1 at a constant speed.

The amount of movement of the optical head 9 by this feed motor 5 is, for example, up to 2 to cover the information area of the optical disc 1.
It is set to a value of 00+1111.

The measuring device 49 includes a control circuit unit for moving the optical head 9 by an appropriate amount so that the laser beam is accurately focused on a predetermined location on the optical disc 1 in the event of surface blurring or warping of the optical disc 1, It has various built-in circuit sections for making measurements related to the amount of displacement. Specifically, there is a focus servo control circuit that controls the distance between the objective lens of the optical head 9 and the track surface of the optical disc 1 to be kept constant, and a focus servo control circuit that controls the distance between the objective lens of the optical head 9 and the track surface of the optical disc 1, and a focus servo control circuit that controls the distance between the objective lens of the optical head 9 and the track surface of the optical disc 1, and a focus servo control circuit that controls the distance between the objective lens of the optical head 9 and the track surface of the optical disc 1. A tracking servo control circuit for controlling movement in the radial direction and tracking control of the optical disc 1 based on displacement signals from the optical receivers 25 and 45 shown in FIG.
It incorporates various circuit sections for outputting information regarding the amount of displacement of the optical disk 1, such as the amount of displacement 1 such as surface runout in the direction of the rotation axis. This measuring device 49 is connected to the arithmetic processing unit V4@51, and the measuring device 49 transmits various information regarding the amount of displacement of the optical disc 1 to the arithmetic processing unit 51.

Next, the internal configuration of the arithmetic processing unit 51 will be explained in detail.

The memory 53 stores various information transmitted from the measuring device 49,
For example, information regarding the amount of radial displacement of the optical disc 1,
Various types of information such as information regarding displacement such as surface runout in the direction of the rotational axis of the optical disc 1, information regarding the distance from the position where the optical head 9 exists, that is, the center point of the optical disc 1 to the optical head 9, information regarding the rotation angle of the optical disc 1, etc. information is stored.

The calculation display unit 55 calculates the amount of displacement of the optical disc 1 in the radial direction and the displacement in the direction of the rotation axis of the optical disc 1 based on various information stored in the memory 53, and displays the calculated displacement range. Display it as a graph.

Fast Fourier transform (hereinafter abbreviated as FFT) analysis equipment @57
is a plurality of pieces of information stored in the memory 53, for example 2048
A value related to the physical characteristics of the optical disc 1, for example, the acceleration of the displacement amount with respect to the frequency, is calculated at high speed based on the data. For example, when calculating acceleration based on 1024 pieces of data, the calculation process is performed at high speed in a short time of 110111 seconds or less. The frequency analyzer 57 is, for example, a high-speed FFT analyzer, DSPP-9 manufactured by Toshiba.
Hardware such as 506 that can perform FFT operations exclusively is used. Further, the FFT analyzer 57 obtains the maximum acceleration value for each frequency from among the plurality of acceleration values of the calculation results, that is, the acceleration values for each frequency of the displacement amount of the optical disk 1, and also calculates the maximum acceleration value for each frequency. Information regarding the maximum value of acceleration is sent to comparator 59. Reference values of acceleration for each frequency are set in advance in the comparator 59, and these reference values and the maximum value of acceleration for each frequency obtained from the FFT analyzer 157 are compared for each frequency. Then, the result of this comparison is sent to the calculation display section 55. The calculation display unit 55 displays a graph based on the comparison result information from the comparator 59.

Next, the effect will be explained.

First, a case will be described in which the acceleration of the displacement amount of the optical disk 10 in the radial direction is calculated.

By rotating the spindle motor 3 at a constant speed, the optical disc 1 is rotated at a constant speed, for example, 60 Orp.
Rotate with m. Next, the feed motor 5 is driven to position the optical head 9 at a preset measurement point. By positioning the optical head 9 at a predetermined measurement point with respect to the rotating optical disk 1 in this manner, information regarding the amount of radial displacement of the optical disk 1 at this measurement point is sampled. Information regarding the amount of radial displacement of the optical disc 1 sampled in this way is stored in the memory 53. The FFT analysis device 57 executes analysis processing based on a plurality of pieces of information regarding the amount of radial displacement of the optical disk 1 stored in the memory 53.

To specifically explain the analysis processing in this FFT analyzer 57, the frequency of the radial displacement of the optical disc 1 is set on the horizontal axis, and the power spectrum for each frequency of the radial displacement of the optical disc 1 is set vertically. Set it on the axis and analyze it. Once the spectrum of the radial displacement of the optical disc 1 for each frequency is determined in this manner, the acceleration of the radial displacement of the optical disc 1 for each frequency is calculated based on this spectrum. Furthermore, the frequency analyzer 57 determines the maximum value of acceleration for each frequency from among the plurality of calculated acceleration values.

Information on the maximum value of acceleration for each frequency thus obtained is sent to the comparator 59. The comparator 59 compares the preset reference value for each frequency with the maximum value of acceleration sent out from the FFT analyzer M57 for each frequency, and sends information on the results of this comparison to the arithmetic processing section 55. Send. The calculation display section 55 displays the comparison result based on the information from the comparator 59.

Next, the feed motor 5 is driven to move the optical head 9 to the next measurement point, and information regarding the amount of radial displacement of the optical disk 1 at this new measurement point is sampled. Thereafter, similarly, the acceleration of the radial displacement amount of the optical disc 1 is calculated based on the information obtained by sampling at the new measurement point.

Next, a case will be described in which the displacement acceleration such as surface runout in the direction of the rotation axis of the optical disc 1 is calculated.

As described above, by rotating the spindle motor 3, the optical disc 1 is rotated at a constant speed. Further, the optical head 9 is positioned at a predetermined measurement point by driving the feed motor 5. With the optical head 9 positioned at a predetermined measurement point in this manner, information regarding the amount of displacement such as surface runout in the direction of the rotation axis of the optical disk 1 is sampled. Information regarding the amount of displacement such as surface runout in the direction of the rotation axis of the optical disc 1 sampled in this way is stored in the memory 53. The FFT analysis device 57 quickly calculates the acceleration based on a plurality of pieces of information stored in the memory 53 regarding the amount of displacement such as surface blur in the direction of the rotation axis of the optical disc 1. That is,
In the FFT analysis device 57, the frequency between displacements such as surface runout in the direction of the rotation axis of the optical disk 1 is set on the horizontal axis, and the power spectrum for each of these frequencies is set on the vertical axis. Once such a power spectrum is determined, the displacement acceleration of the optical disc 1 in the direction of the rotational axis for each frequency is calculated for each frequency based on this power spectrum. Further, the FFT analyzer 57 determines the maximum acceleration for each frequency from among the plurality of acceleration values, and sends information regarding the determined maximum acceleration value for each frequency to the comparator 59. The comparator 59 compares the preset acceleration reference value for each frequency with the maximum acceleration value transmitted from the FFT analyzer 57 for each frequency, and displays information on the results of this comparison on the calculation display section. 55. The calculation display section 55 displays the comparison result based on the information from the comparator 59.

As mentioned above, in this example, the analysis process related to physical characteristics is performed using hardware dedicated to FFT calculation, so the analysis process is fast and stable, and can be performed in the conventional manufacturing process. It is possible to perform inspection items that are difficult to perform, such as acceleration, in real time during the process, and also enables various inspections such as modal analysis using frequency analysis.

In addition, in the above-mentioned embodiment, the case where the amount of displacement of an optical disk is optically measured using a laser beam is shown as an example.
The present invention is not limited to this. (The amount of displacement of the optical disk can be measured using an appropriate sensor. For example, by executing focus servo control and tracking servo control, the respective focus coils and track coils can be measured.) It can be configured to measure the amount of displacement of the optical disc according to the value of the flowing current.

[Effects of the Invention] As explained above, according to the present invention, information regarding the amount of displacement of an optical information storage medium is analyzed and processed at high speed using a Fourier transform algorithm. The amount of displacement, for example acceleration, can be quickly calculated.

In addition, since physical characteristics such as acceleration of displacement of optical information storage media can be processed quickly and in a short time, it is no longer necessary to continuously test the acceleration of optical information storage media during the manufacturing process. be effective.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment to which the present invention is applied;
FIG. 2(A) is a plan view of an optical information storage medium inspection apparatus to which the embodiment shown in FIG. 1 is applied, and FIG.
FIG. 3 is an explanatory view showing the main part of FIG. 2. 1... Optical disk 9... Optical head 57... FFT analysis equipment

Claims (1)

[Scope of Claims] An apparatus for inspecting physical characteristics of an optical information storage medium based on displacement detected from the optical information storage medium, wherein when inspecting the physical characteristics, Fourier transform is performed. 1. An inspection device for an optical information storage medium, comprising an analysis processing means that performs inspection processing based on an algorithm.