JPH01307610A - Inspecting device for disk surface waviness shape - Google Patents

Abstract

PURPOSE:To detect a disk surface waviness shape with a high resolution by using a semiconductor laser light source as a light source of a light beam for irradiating a disk which is rotating and drawing an irradiation timing of light, comparing with a rotation period of the disk. CONSTITUTION:A disk 1 which is rotating is irradiated by a light beam from a semiconductor laser light source 13, and a reflected light of the light beam is received by a photodetector 5. An irradiation light control part 14 draws a timing of a driving signal which is applied pulsatively, comparing with a rotation period of the disk 1, and whenever the disk 1 rotates, different positions are irradiated successively and intermittently by the light beam and the disk 1 rotates plural times, and thereafter, all data are obtained. In such a way, a waviness shape in the direction going along the periphery of an equal distance from the rotation center of the disk can be detected with a high resolution.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an apparatus for inspecting the surface waviness shape of a disk rotating at high speed, and is capable of inspecting the waviness shape of a disk rotating at high speed with high lateral resolution using a simple configuration. The purpose of the present invention is to provide a device that inspects the waviness shape of the disk surface by receiving the reflected light of a light beam irradiated on a rotating disk by a light receiving element, in which the light source of the light beam is a semiconductor laser light source. Further, the laser light source is provided with an irradiation light control section, and the control section is configured to extend the light irradiation timing relative to the disk rotation period.

[Industrial Field of Application] The present invention relates to an apparatus for inspecting the surface waviness of a disk rotating at high speed.

Conventionally, it was intended to inspect the waviness shape of a magnetic disk rotating at high speed using a four-part photo sensor, but
Capacitive sensors have the drawback of not being able to follow the faster-rotating disks, and of insufficient lateral resolution. Therefore, there was a need to develop an inspection device with a simple configuration and higher resolution.

[Prior Art] A disk, such as a magnetic disk that rotates at 3,600 revolutions per minute, which is supposed to be a flat plate in a stationary state, may cause "waviness" due to temperature during manufacturing, processing distortion, etc.

FIG. 4 is a schematic diagram showing a conventional waviness inspection device. In Fig. 4, 1 is a disk, IA is a broken line showing a disk tilted by an angle θ, 2 is an axis for rotating the disk, and 3
4 indicates a laser light source, 4 a beam splitter, and 5 a four-divided light receiving element sensor. The disk is stopped at a position indicated by 2 around a rotating shaft 2 and rotated at high speed. Therefore, when the disk is in a stopped position, for example, the circumference is bent below the horizontal line, and during high-speed rotation, the disk receives rotational torque in the circumferential direction on a horizontal plane, or conversely rises above the horizontal plane. . In a magnetic disk, a magnetic head is provided close to the disk surface, so if the rotating disk collides with the head, there is a risk that both will be destroyed. Therefore, it is necessary to examine the deflection and waviness of the disk surface when rotating at high speeds such as 3,600 revolutions per minute. Laser light from the laser light source 3 is irradiated onto one surface of the disk, and the reflected light can be investigated using the light receiving element sensor 5 as described below. FIG. 5 is a view of the light-receiving element sensor 5 viewed from the front (disc reflected light incident side), and four light-receiving elements 5A to 5D are provided almost in contact with each other in the upper, lower, left, and right directions. Light emitted from the laser light source 3 to a predetermined position P1 on the horizontal plane on the stopped disk 1 after passing through the beam splitter 4 is reflected directly above and is bent at a right angle by the beam splitter 4, thereby striking the center of the light receiving element 5, i.e. , is incident on the contacting portions of elements 58 to 5D as indicated by the circle. Next, assume that the disk 1 rotates at high speed and reaches the state indicated by the broken line IA. The laser beam is incident on the surface of the light-receiving element sensor 5 at a position marked ◎. If the distance between ○ and ◎ is S, and the distance between the beam splitter 4 and the disk 1 surface is L, then 5=2Lθ is calculated.

Therefore, if light is irradiated from a predetermined position P1 on the disk surface rotating at high speed to another position P2 and the value of S is measured, it can be determined whether there is a change in the value of θ between Pl and 82 (S). In other words, the undulation shape of the disk surface can be sequentially measured on the disk surface. In addition, in order to obtain the positional change of ◎, the amount of light received by each of the elements 5A to 5D is calculated.

For example, regarding the amount of light received by each element (5A + 5B) and (5C
+50), and then calculate the difference value for each term. If a calibration curve is obtained and stored in advance, the value of S can be determined directly from the difference value of the amount of received light.

[Problems to be Solved by the Invention] In the configuration shown in FIG. 4, the laser beam from the light source 3 is
For example, the diameter of the surface is narrowed down to 50 μm. Disc 1 has a diameter of 5.25 inches and its outermost circumference is pitch 2.
It is necessary to measure at 0 μm and inspect the waviness shape, and the amount of data is approximately 84, and the disk speed is 60 m/sec.
Since it also rotates, the data rate is approximately 5M data/s. Therefore, a light receiving element using a photodiode with a frequency band of about 100 kHz cannot perform measurement at all.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide an apparatus that can inspect the undulation shape of a disk rotating at high speed with a high resolution in the lateral direction with a simple configuration.

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In FIG. 1, 1 is a disk, 4 is a light beam splitter, 5 is a light receiving element, 13 is a semiconductor light source, and 14 is an irradiation light controller.

The present invention has the following configuration in an apparatus for inspecting the shape of waviness on the surface of a disk (1) by receiving reflected light of a light beam irradiated onto a rotating disk (1) by a light receiving element (5). That is, the light source of the light beam is a semiconductor laser light source (13), and the cough laser light source is equipped with an irradiation light control section (14), and the control section (14) controls the irradiation of light in proportion to the rotation period of the disk (1). This is because the timing is extended.

[Operation] In the configuration shown in FIG. 1, since the light source of the light beam is a semiconductor laser light source, pulsed laser light can be obtained by applying a pulsed drive signal when controlling laser emission. Therefore, if the timing of applying the drive signal is extended compared to the rotation period of the disk 1, and the light beam is controlled to be irradiated intermittently to specific positions each time the disk 1 rotates, the disk 1 can be rotated multiple times. All data can be retrieved after rotation.

[Example] FIG. 2 is a diagram showing the configuration of an embodiment of the present invention.

In FIG. 2, an irradiation light control section indicated as 14 is composed of a laser pulse drive circuit 15 and a control circuit 18. 1
6 is a disk rotation motor, 17 is a low encoder that outputs a disk rotational position signal, 19 is a central processing unit CPU, 20 is a memory for storing test data, 21 is a test signal processing section, and 22 is a data collection section. ing. A reference position signal regarding the rotation of the disk 1 is received by the rotary encoder 17, and a signal for driving the semiconductor laser light source 13 is obtained from the control circuit 18 in response to the reference pulse.
The voltage is applied to the drive circuit 15. For example, when performing laser light irradiation M times on the outermost circumference of the disk L, the M+1 irradiation is set to irradiate the second irradiation point side more than the first irradiation, and the irradiation is performed a total of N times. irradiate the entire circumference of the disc. FIG. 3 shows an operation timing chart of FIG. 2. FIG. 3A shows the output of the low-resolution encoder, and the period is T. This period corresponds to one rotation time of the disk. When data is collected through N rounds as described above, the semiconductor laser is driven with a delay of T/N time from T as shown in FIG. 3B.

The light reflected from the surface of the disk 1 is received by the light receiving element 5, and an output signal shown in FIG. 3C is obtained.

FIG. 3C shows the output of one element of the light-receiving element 5. As described above, the position of incidence on the light receiving element changes depending on the surface shape of the disk. The sensor output shown in FIG. 3C is obtained by converting the photocurrent into voltage in the scanning signal processing section 21, performing calculations on the output of each element, and outputting it to the data collection section 22. In the data acquisition unit 22, peak detection or integral type analog-to-digital conversion is started by a start trigger signal (signal corresponding to the laser pulse drive circuit output) from the control circuit 18,
Store the conversion output in a buffer. At the same time as restarting processing for the next signal by the next start trigger signal,
The buffered data is stored in the test data storage memory 20. At this time, the central processing unit 19 can appropriately command the memory storage location. After the inspection is completed, the central processing unit 19 reads the data from the memory 20 and calculates the surface waviness shape.

The object to be measured to which the present invention is applied is not limited to a magnetic disk, but the surface shape of the same object that moves at high speed can be inspected.

[Effects of the Invention] As described above, according to the present invention, although it takes a rather long time, a light-receiving element sensor in a normal frequency band is used to measure the surface of a disk in the circumferential direction (
The undulation shape can be inspected with high resolution in the direction along the circumference equidistant from the center of rotation).

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the invention, and Fig. 3 is a diagram showing the configuration of the embodiment of the present invention.
4 is a diagram showing the configuration of a conventional inspection device, and FIG. 5 is a diagram showing a light receiving element in FIG. 4. 1 - Disk 3 - Laser light source 4 - Beam splitter 5... Photodetector sensor 13 - Semiconductor light source 14 - Irradiation light control unit Patent applicant Fujitsu Ltd. Representative Patent attorney Eisuke Suzuki Favorite E 1 ◇ Four mouths 1st figure

Claims (1)

[Scope of Claims] An apparatus for inspecting the shape of waviness on the surface of a disk (1) by receiving reflected light of a light beam irradiated onto a rotating disk (1) by a light receiving element (5), comprising: a light source for the light beam; is a semiconductor laser light source (13), and the laser light source is equipped with an irradiation light control section (14), and the control section (14) is configured to extend the light irradiation timing relative to the rotation period of the disk (1). This is an inspection device for the shape of waviness on a disk surface.