JPH0656661B2 - Spot alignment method and optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention is a method for accurately aligning two spots on the same track in an optical disc device for performing error check immediately after recording and recording / reproducing / erasing with two spots. And equipment.

[Background of the Invention]

Conventionally, there has been considered a method of realizing an error function immediately after recording and a recording / reproducing / erasing function by using two spots having different wavelengths in an optical disk device. In the former, the first recording spot and the second reproducing spot are arranged close to each other on the same track, and immediately after the data is recorded by the first recording spot, the recorded data is reproduced by the second reproducing spot and an error occurs. It is a check. The latter uses a chalcogenide-based recording material, which is used for the first recording / reproducing in an optical disk for recording / reproducing / erasing information by crystallizing or amorphizing the material by irradiation of laser light. A circular spot and a second erasing oval spot are arranged in proximity to each other on the same track, and the first recording / reproducing spot is irradiated with short pulse light to rapidly heat and quench the material to make it amorphous. After recording, the second erasing spot is irradiated with a comparatively long pulse light to gradually heat and cool the material to crystallize and erase.

However, in the optical disk device using these two spots, it is necessary to dispose the two spots on the same track so as to be close to each other, so that it is necessary to incline the light beams from the two light sources by a very small angle and make them enter the focusing lens. Therefore, there arises a problem that it is difficult to adjust a minute angle, and the positional relationship is displaced due to temperature and vibration, which makes it difficult to perform accurate error check and recording / reproducing / erasing.

[Object of the Invention]

The object of the present invention is to install an adjusting track in the disk to be used in order to facilitate the two-spot alignment.
Another object of the present invention is to provide a stable spot position aligning method and device by installing photodetectors capable of detecting information and a track shift signal in both of the two spots.

[Outline of Invention]

In the present invention, the adjustment track is divided into blocks, and the blocks are recorded at equal intervals. The number of the dots is sequentially changed by the tracks, and the two photodetectors receive light. The relative number of track deviations is confirmed from the number of pits in the signal, and the amount of deviation on the track is confirmed from the number of pits, and the two spots are aligned based on this.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Here, two laser light sources with different wavelengths (Ar laser, He
A case of forming two spots by using a (Ne laser, a semiconductor laser) will be described. The laser light source 1 having the first wavelength λ ₁ is used to form a recording / reproducing spot, and the light emitted from the laser light source 1 is collimated by the condenser lens 2 and passes through the wavelength separation filter 3 to be polarized. Prism 4, 1/4
It is bent by the wave plate 5 and the galvanometer mirror 6, and further narrowed down as a spot 9 on the track of the disk 8 by the narrowing lens 7. Further, the laser light source 10 of the second wavelength λ ₂ is a low power laser in the case of an error check,
Use a high-power laser for erasing. Light emitted from the laser light source 10 is a condenser lens 11 and a galvanometer mirror 1.
After passing through the wavelength separating filter 3 and passing through 2, the light from the first laser light source 1 passes through almost the same optical path and is narrowed down by the focusing lens 7 in the vicinity of the recording / reproducing spot 9 on the same track for reproducing or erasing. It is narrowed down as a spot 13 for use. The distance d between the two spots is d = if the focal length of the focusing lens 7 is f and the angle θ between the optical path of the first laser light source and the optical path of the second laser light source is perpendicular to the paper surface.
It can be expressed as fθ. For example, if f = 4.5 mm and d = 20 μm, θ = 4.4 mrad, and the optical path of the second laser light source 2 with respect to the optical path of the first laser light source 1 becomes the laser light source 2 itself.
It suffices that the galvano mirror 12, the wavelength separation filter 3 and the like are incident on the aperture lens 7 with a tilt of 4.4 mrad in the direction perpendicular to the paper surface. Further, in order to position the two spots on the same track, the information recorded on the track at each spot may be recognized by reading and comparing it, but the alignment accuracy is 0.1% for the allowable track deviation amount. If it is μm, a high accuracy of θ = 0.0022 mrad is obtained from d = f · θ. Therefore, there is a possibility that the track and the track may be displaced vertically due to temperature and vibration. This embodiment provides a method for easily aligning two spots on the same track by using a disk having an adjustment track, and further, for the second laser light source 10, a track deviation detecting circuit and a track deviation correcting galvano mirror. By providing the device, a device that is not affected by temperature or vibration is provided.

First, the adjusting track 50 provided on the disk 8 will be described with reference to FIG. The adjusting track 50 is preferably provided on the innermost circumference or the outermost circumference of the disk 8. The adjustment track 50 is divided into n blocks 51 on the circumference, for example, in a digital optical disk for a computer, it is divided into 32 or 64 sectors, so that n = 32,
Select 64 (Fig. 2 (a)). In the block, the pits 53 are recorded on the group 52 in the form of unevenness or dark and light pits which are larger than the diameters of the two spots and are arranged at equal intervals, and the number of pits is different for each track.
It may continuously increase or decrease monotonically,
The increase and decrease may be repeated (FIG. 2 (b)).
In FIG. 2B, assuming that the recording / reproducing spot 9 and the error checking or erasing spot 13 have the positional relationship shown in the figure at the time of adjustment, the photodetector provided for each spot is A reproduced signal as shown in FIG. 2 (c) is obtained. That is, the output I is the signal from the spot 9 (the output of 23) and the output II is the signal from the spot 13 (the output of 30). As a result, the second spot 13 is at a position displaced by two tracks with respect to the first spot 9, and is further delayed by 2 pits in time.
If the pit interval is 10 μm, it means that the pits are displaced in the circumferential direction of 20 μm. Therefore, the spot 13 is moved by two tracks in the vertical direction of the track so that the reproduced signal becomes 5 pits in the block, and if it is 20 μm in the circumferential direction, it remains as it is. The movement of the beam in the vertical direction of the track can be known by looking at the number of pits for each movement, because the number of pits varies sequentially for each track.

The detection system will be described below with reference to FIG. 1 again. The spots 9 and 13 reflected by the disk 8 pass through the aperture lens 7, galvano mirror 6 and quarter wavelength plate 5 again, and the optical path is separated by the polarizing prism 4. After being separated, the wavelength separation filter 14 having the same characteristics as the wavelength separation filter 3 transmits the luminous flux of the spot 9 of the first laser light source 1 of the wavelength λ ₁ and transmits the spot of the second laser light source 10 of the wavelength λ ₂ . Thirteen
Is reflected. The transmitted light flux is further divided into two equal parts by the half prism 15, and the reflected light flux is reflected by the lens 1.
The light flux that has entered the photodetector 17 for detecting the track shift signal and the information signal through 6 and has passed through the lens 18
The light passes through the cylindrical lens 19 and enters the defocus signal detection photodetector 20. The photodetector 17 is usually divided into two, and the respective outputs are differentiated by the differential amplifier 21 to become a tracking signal, and the galvanomirror 6 is driven through the servo circuit 22 to track the track according to the eccentricity of the disk 8. Do. Further, the respective outputs are added by the adder 23 to form an information signal, which is used for signal reproduction. The photodetector 20 is usually divided into four parts, and after each output is calculated, it becomes a defocus signal in the differential amplifier 24, and the voice coil to which the focusing lens 7 is attached is driven through the servo circuit 25. Automatic focus tracking is performed according to the vertical movement of the disk 8. Also,
The light flux of the spot 13 reflected by the wavelength separation filter 14 passes through the lens 26 and enters the two-split photodetector 27.
Each output from the photodetector 27 is differentiated by the differential amplifier 28 to become a track shift signal of the spot 13, and by driving the galvanometer mirror 12 through the servo circuit 29, the temperature after the two spot positions are adjusted by the adjustment track, and the like. Corrects minute deviation due to vibration. Also the photodetector 27
The respective outputs from 1 to 3 are added by the adder 30 to form the information signal of the spot 13, which is used at the time of two spot alignment by the adjustment track.

〔The invention's effect〕

As described above, according to the present invention, two spot positions can be easily aligned by providing the adjustment track on the disk, and the micro-deviation due to temperature and vibration can be corrected by providing the photodetector on each of the two spots. Therefore, it is possible to provide an information processing apparatus using a stable two spot for performing error check and recording / reproducing / erasing.

[Brief description of drawings]

FIG. 1 is a block diagram showing the first embodiment, and FIG. 2 is a conceptual diagram illustrating an adjustment track. 1 ... First laser light source, 3, 14 ... Wavelength separation filter, 9 ... First laser light source spot, 10 ... Second
Laser light source, 12 ... Galvanometer mirror, 13 ... Second
Laser light source spots, 17, 27 ... 2-split photodetector, 20 ... 4-split photodetector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Miyamura 1-280, Higashi Koigakubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-58-102343 (JP, A)

Claims (4)

[Claims] 1. A spot alignment method for an optical disc apparatus, wherein two spots are formed so as to be located back and forth along a track on a disc surface, and information is recorded / reproduced in the disc. An adjustment track for adjustment is provided, and the adjustment track is recorded with pits in which the number of pits is sequentially different for each track and the pit intervals are equalized between the tracks. A spot alignment method, wherein the two spots are aligned by detecting the reflected light from each of the two spots and comparing the detected signals. 2. The spot alignment method according to claim 1, wherein the adjustment track is arranged on the outermost or innermost circumference of the disc. 3. The spot alignment method according to claim 1, wherein the adjustment track is divided into a plurality of blocks in the circumferential direction. 4. An optical disc device for forming information on a disc surface, wherein two spots are formed so as to be located in front and back along a track on the disc surface, and light for detecting reflected light from each of the two spots. A detector, a means for producing a track position deviation signal of each spot from the output of the photodetector, and a means for moving the positions of the two spots in the radial direction of the disk based on the respective track position deviation signals. An optical disk device characterized by having.