JPH0714334A - Head flying height measuring device for hard disk - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to measure the flying height of the head with high accuracy by eliminating the change in the light amount due to the shift of the interference light. [Structure] The reflected light from the hard disk 1 and the reflected light from the head 2 that reads and writes information from the hard disk 1 are guided to separate points on different optical paths to cause interference, and the intensity change of the interference light is measured, Hard disk 1 of head 2
In a flying height measuring apparatus for a hard disk head, which measures the flying height of the reflected light A and B, at least one of the optical path of the reflected light A from the hard disk 1 and the optical path of the reflected light B from the head 2 is measured. An optical system is provided for expanding the bundle of reflected light so that one bundle of rays falls within the other bundle of rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flying height measuring device for a hard disk head for measuring the flying height of a head for reading and writing information from a hard disk used in a computer such as a personal computer.

[0002]

2. Description of the Related Art As shown in FIG. 4, a head 52 reads / writes information from / in a hard disk 51 used as a storage device in a computer such as a personal computer. In this case, by rotating the hard disk 51 at high speed ,. As shown in FIGS. 4B and 4C, the head 52 floats, and a gap (flying height) is formed between the hard disk 51 and the head 52. The smaller the flying height, the larger the storage capacity of the hard disk 51. However, since there are minute protrusions on the surface of the hard disk 51, if the flying height is made too small, the head 52 and the protrusion will contact, and the head 52 will crash. Therefore, it is necessary to develop a hard disk 51 with few protrusions.

To develop a hard disk 51 with few protrusions and a small flying height (developing a hard disk having a stable surface so that the flying height does not change depending on the position of the hard disk when the hard disk rotates at a constant speed) It is necessary to measure the distance (flying height) between the hard disk 51 and the head 52. As a flying height measuring device for measuring the flying height of the head 52 as described above, there is one using the interference light of a laser.

FIG. 5 shows a conventional flying height measuring apparatus for a hard disk head of this type. A laser 53 irradiates the hard disk 51 and the head 52 with laser light. Since the head 52 is equipped with a quarter-wave plate 59 and the incident surface thereof is coated with a half mirror film, half of the laser light is reflected by the half mirror surface and becomes reflected light from the head 52. The other half is transmitted through the half mirror and the quarter wavelength plate 59, reaches the surface of the disk 51, and is reflected. The reflected light from the disk 51 exits from the quarter-wave plate 59 along the same path as when it was incident.
Due to the action of the quarter-wave plate, the polarization plane is rotated by 45 degrees twice while reciprocating in the interior thereof, and the light is shifted by 90 degrees with respect to the polarization plane before incidence. Therefore, the reflected light from the disk 51 does not interfere with the reflected light from the head 52 even if they overlap at this point, and the optical paths can be easily separated by utilizing the difference in polarization angle. The polarization beam splitter 54 sends the laser light reflected by the hard disk 51 toward the beam splitter 56, and the beam splitter 55 sends the laser light reflected by the head 52 toward the polarization beam splitter 57. The reflected light from the hard disk 51 and the reflected light from the head 52, which are split by the polarization beam splitters 54 and 55, have their optical axes adjusted in different optical paths, are guided to a beam splitter 57, and are superimposed. After the beam splitter 57, a quarter wave plate 60
Are arranged so that the optical axis thereof is 45 degrees with respect to the polarization angle of each reflected ray bundle, and thus these two ray bundles are immediately after passing through the quarter-wave plate 60. They are converted into circularly polarized lights that rotate in opposite directions, and immediately interfere with each other.
The photodetector 58 measures the intensity change of the interference light to convert the flying height of the head 52.

[0005]

However, in the conventional flying height measuring apparatus for a hard disk head, as shown in FIG. 6, the reflected light A from the hard disk 51 and the reflected light B from the head 52 are stopped by the hard disk 51. Even if the heads 52 are floated by the rotation of the hard disk 51 as shown in FIGS. 4 (b) and 4 (c) even if the heads 52 are perfectly matched and interfere with each other, in principle, the hard disk may be replaced as shown in FIG. A large deviation occurs at the interference point between the reflected light A from 51 and the reflected light B from the head 52. Therefore, there is a problem that the change in the light amount due to the change in the flying amount of the head 52 and the change in the light amount due to the shift of the interference light are mixed, and the measurement accuracy of the flying amount of the head 52 is impaired.

In view of the above problems, the present invention makes it possible to measure the flying height of the head with high accuracy by eliminating the change in the light amount due to the shift of the interference light.

[0007]

The technical means of the present invention for solving this technical problem is to provide the reflected light from the hard disk 1 and the reflected light from the head 2 for reading / writing information to / from the hard disk 1. In a flying height measuring device for a head for a hard disk, the flying height of the head 2 with respect to the hard disk 1 is measured by measuring the change in the intensity of the interference light by guiding them to different points on different optical paths to cause interference. Path of reflected light A and head 2
An optical system that expands the bundle of reflected light rays so that one bundle of reflected light rays A and B falls within the other bundle of rays is provided on at least one of the optical paths of the reflected light rays B from. In point.

[0008]

Even if the head 2 floats due to the rotation of the hard disk 1, the reflected light A from the hard disk 1 and the reflected light B from the head 2 are moved in one light beam bundle and the other light beam bundle as shown in FIG. Only to do. Therefore, the area of the overlapping portion of the reflected light A from the hard disk 1 and the reflected light B from the head 2 is constant, and it is possible to cancel the light amount change due to the shift of the interference light.

[0009]

The present invention will be described below with reference to the illustrated embodiments. In FIG. 1, reference numeral 1 is a hard disk, 2 is a head for reading and writing information from the hard disk 1, and a 1/4 wavelength plate having a half mirror film is mounted for measuring the flying height. A laser 3 irradiates the hard disk 1 and the head 2 with laser light. However, this laser light is a light flux that has been processed so that the intensity distribution in the cross section of the light flux is uniform in advance, or is considered to be uniform in practice.

Reference numerals 4 and 7 denote polarization beam splitters, and 6 and 5 denote beam splitters. The polarization beam splitter 4 sends the laser light reflected by the hard disk 1 toward the beam splitter 6, and the beam splitter 5 reflects it by the head 2. The laser beam is sent to the polarization beam splitter 7. Further, the hard disk 2 divided by the polarization beam splitter and the beam splitters 4 and 5
The reflected light from the head and the reflected light from the head 2 are guided to the interference points of the beam splitter 7 and the quarter-wave plate 10 through separate optical paths to interfere with each other.

Reference numeral 8 is a photodetector, which is a quarter-wave plate 1
The flying height of the head 2 is converted by measuring the intensity change of the interference light transmitted from 0. A beam expander 11 is provided on the optical path of the reflected light A from the hard disk 1 between the polarization beam splitter 4 and the beam splitter 6. The beam expander 11 converts the reflected light A from the hard disk 1 from a thin parallel light flux to a thick parallel light flux, and as shown in FIG.
The thin parallel light beam bundle of is contained in the thick parallel light beam bundle of the reflected light A from the hard disk 1. As a result, even if the head 2 floats due to the rotation of the hard disk 1, the reflected light B from the head 2 only moves within the reflected light A from the hard disk 1 as shown in FIG. The thin parallel light flux of B is kept within the thick parallel light flux of the reflected light A from the hard disk 1.

FIG. 3 shows another embodiment. Like the above embodiment, a beam expander 11 is provided in the optical path of the reflected light A from the hard disk 1 between the polarization beam splitter 4 and the beam splitter 6, and the beam expander 11 is provided. A condenser lens 12 is provided in the optical path of the reflected light B from the head 2 between the splitter 5 and the polarization beam splitter 7. In this case, the beam expander 11 is the hard disk 1
The reflected light A from is converted into a thin parallel light bundle by converting the thin parallel light bundle into a thick parallel light bundle, and the condenser lens 12 converts the reflected light B from the head 2 into a thinner parallel light bundle, and the reflected light B from the head 2 is thin. The bundle of parallel rays falls within the thick bundle of parallel rays of the reflected light A from the hard disk 1. The other points are the same as those of the above-mentioned embodiment.

In the above embodiment, the hard disk 1
The beam expander 11 is provided in the optical path of the reflected light A from the head, or the beam expander 11 is provided in the optical path of the reflected light A from the hard disk 1 together with the head 2
Although the condenser lens 12 is provided in the optical path of the reflected light B from the head, instead of this, only the beam expander 11 may be provided in the optical path of the reflected light B from the head 2, or from the hard disk 1. The condensing lens 12 may be provided in the optical path of the reflected light A and the beam expander 11 may be provided in the optical path of the reflected light B from the head 2. By doing so, the reflected light A from the hard disk 1 The bundle of rays comes to fall within the bundle of rays of the reflected light B from the head 2.

[0014]

According to the present invention, in at least one of the optical path of the reflected light A from the hard disk 1 and the optical path of the reflected light B from the head 2, one light beam bundle of the reflected light A and the other light beam of the reflected light B is provided. Since the optical system for converging the light beam bundle of the reflected light so as to be contained in the light beam bundle is provided, even if the head 2 floats due to the rotation of the hard disk 1, the reflected light B from the head 2 and the hard disk 1 With the reflected light A, the other light beam bundle only moves within the one light beam bundle, and the other light beam bundle is maintained within the one light beam bundle. The area of the overlapping portion of the reflected light A and the reflected light B from the head 2 is constant, so that the light quantity does not change due to the deviation of the interference light, and the flying height of the head 2 can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining operational effects.

FIG. 3 is a configuration diagram showing another embodiment.

FIG. 4 is a sectional view for explaining a conventional example.

FIG. 5 is a configuration diagram showing a conventional example.

FIG. 6 is an explanatory diagram for explaining a conventional problem.

FIG. 7 is an explanatory diagram for explaining a conventional problem.

[Explanation of symbols]

 1 Hard Disk 2 Head 3 Laser 4 Polarization Beam Splitter 5 Beam Splitter 6 Beam Splitter 7 Polarization Beam Splitter 8 Photodetector 11 Beam Expander 12 Condenser Lens

Claims (1)

[Claims] 1. Reflected light from a hard disk (1) and reflected light from a head (2) for reading / writing information from / to the hard disk (1) are guided to different points to interfere with each other, and the interference light is generated. Of the reflected light (A) from the hard disk (1) in a flying height measuring device for a hard disk head, in which the flying height of the head (2) with respect to the hard disk (1) is measured. The ray bundle of the reflected light is so arranged that at least one of the ray bundles of the reflected rays (A) and (B) falls within the other ray bundle in at least one of the optical paths of the reflected ray (B) from the head (2). A flying height measuring device for a hard disk head, which is provided with an optical system for expanding.