JPS60263343A - Optical information processor - Google Patents

Abstract

PURPOSE:To attain the assured tracking with no effect of minute flaws, etc. by forming the images of a recording medium on two photosensors with different beams of a light source to form a stripe pattern having a pitch different slightly from a track pitch. CONSTITUTION:The track pitch of a disk 12 is slightly different from a stripe pattern of a grid 30, and the moire patterns are produced on sensors 24 and 26 with the beams of a light source 20. A light quantity distribution has a waveform having a cycle, and this cycle is decided by the difference between space frequencies of both pitches. The light quantity distributions of both sensors 24 and 26 are shown by solid lines in the figure when the coincidence is obtained at the center part between the pitch phases of a recording track and the stripe pattern and then shown by dotted lines when no coincidence is obtained. Thus the difference is detected by a differential amplifier 32 between output signals of both sensors 24 and 26 to obtain a signal showing a position shift. Based on this signal, an objective lens 10 is driven to set the light spot of a laser 2 at a prescribed track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information processing apparatus.) The present invention relates to an optical information processing apparatus that performs tracking using moiré fringes.

[Prior art]

In general, in recording media such as optical disks, recording and reproduction are performed on high-density recording tracks with a pitch of about 2 μm. Therefore, during recording and reproduction, the position of the track is optically detected, and a light beam is made to follow the track according to the detection signal. A tracker needs to do this.

At this time, as driving methods for making the light beam follow the track, there are a method of driving an optical head consisting of a laser, a lens, a detection system, etc., a method of driving only the lens, a method of using a movable mirror, etc.

As a method for optically detecting the position of a track, the so-called three-beam method, wobbling method, push-pull method, etc. are known.

However, these detection methods have the following drawbacks. First, since a minute light spot is used for detection, the light beam may not follow the track due to minute scratches on the disk. Therefore, the tracks on the disk are required to be of extremely high quality, which increases the cost of the disk.

Second, on writable disks, if the power of the light beam is kept low during playback, writing may be performed by the tracking signal beam; for this reason, the tracking detection signal becomes extremely small. This makes it difficult to ensure a sufficient ratio.

〔the purpose〕

Therefore, an object of the present invention is to provide an optical information system capable of reliably tracking even if there are minute scratches on the disk and at the same time ensuring a detection signal for tracking with a good S/N ratio. The purpose of this invention is to provide a processing device.

〔composition〕

In order to achieve the above object, the present invention provides an optical information processing apparatus that irradiates light emitted from a first light source onto a recording medium and detects reflected light or transmitted light from the recording medium;
A light source is provided, and a pattern forming means for forming a striped light pattern by forming an image of the recording medium on a light detecting means consisting of at least two light sensors using light emitted from the second light source; The striped light pattern is provided in front of the recording medium, and the striped light pattern is parallel to the recording tracks on the recording medium and has a pitch slightly different from the pitch of the recording tracks.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a diagram showing the principle of construction of an optical information processing device according to a first embodiment of the present invention. Collimator lens, 6 is a first beam splitter, 8 is a second beam splitter, 10 is an objective lens, 12 is a disk serving as a recording medium, 14° is an imaging lens, 16 is a third beam splitter, 18° is an RF It is a sensor.

The light emitted from the radar 2 is made into a parallel beam by the collimator lens 4, passes through the first beam snoritter 6, passes through the second beam snoritter 8, and the objective lens 10, and then is reflected by the disk 12. It is reflected again by the second beam slittor 8, passes through the imaging lens 14, is reflected by the third beam slittor 16, and is irradiated onto the RF sensor 18.
The F sensor 18 detects information on the disk 12. The R
The F7 sensor 18 is a powerful device for detecting information, and by providing a cylindrical lens or knife in the optical path and dividing the RF sensor into 2 or 4, the signal for autofocus A-cus can be detected. .

Further, 20 il-K 2 light sources, 22 condenser lenses, 24 a first optical sensor, and 26 a second optical sensor, the first and second optical sensors 24 and 26 constitute a light detection means 28, A grating 30 having a pitch slightly smaller than the track pitch of the disk 12 and serving as a mother turn forming means for forming striped light turns is provided on the front surface of the light detecting means 28.

The first and second optical sensors 24 and 26 each have a differential amplifier 32.
connected to. Second light source 2 irradiating the disk 12 surface
The reflected light (5) for detecting the track position emitted from 0 passes through the objective lens 1o, passes through the second beam splitter 8, and the imaging lens 14, and condenses on the first optical sensor 24 and the second optical sensor 26. Image. The size of the image at the position of the grating 30 is determined by the ratio of the focal length of the objective lens 1° and the imaging lens 14, and if the focal length of the imaging lens 14 is made longer than the objective lens 1o, then The grid 3o can be made relatively large and is easy to manufacture. The grating 3o can be provided separately from the first optical sensor 24 and the second optical sensor 26, or can be provided in close contact with the surfaces of the first optical sensor 24 and the second optical sensor 26.

Next, the operation of this embodiment will be explained. As mentioned above, the striped nozzles formed on the track pitch grid 30 of the disk 12. Since the pitch is slightly different from the pitch of the turn, a so-called moiré pattern is generated on the first optical sensor 24 and the second optical sensor 26 due to the light from the second light source 2o.
The light amount distribution in the first and second optical sensors 24 and 26 has a waveform with a large period. This period is determined by the difference in spatial frequency between the pitch of the (6) stripes of the grating 3o and the track pitch of the disk 12. Therefore, the light quantity distribution at the first and second optical sensors 24 and 26 becomes as shown in FIG.

Here, as shown in FIG.
(near the optical axis of the light source 200), the first and second
The light quantity distribution of the optical sensors 24 and 26 is exactly as shown by the solid line in FIG. 3, but if it deviates slightly, it becomes as shown by the dotted line. Therefore, by detecting the difference between the output signals of the first optical sensor 24 and the second optical sensor 26 with the differential amplifier 32, a signal representing the positional deviation can be obtained. By taking the ratio of the two, a more accurate signal can be obtained regardless of fluctuations in the amount of light, but the circuit becomes complicated. In general, taking the difference 2 is sufficient.

By driving the objective lens 10 left and right by an objective lens drive system (not shown) in accordance with the signals obtained as described above, the light spot of the laser 2 is aligned with a predetermined track.

Furthermore, the effective reflectance of the recording track and the projected smooth stripe i'? If the brightness and darkness of the turns are reversed at the center, the curve shown in Figure 3 will appear, but if they are arranged so that they match at the center, the curve will be higher at the center. In this case as well, by taking the difference between the signals of the first optical sensor 24 and the second optical sensor 26, a signal representing the positional deviation can be obtained. In this case, the polarity of the signal is opposite to that in the above case.Also, when the focus state on the disk 12 changes slightly, the size of the strijino 9 turns on the disk 12 may change, but the focus Even if the position signal cannot be obtained when the condition of the sensor is poor, there is a practical problem. Further, as shown in FIG. 1, if a lens 34 is provided at the rear focal position of the objective lens 12 and a so-called telecenter (IJ Sock system) is used, the size of the stripe pattern will not change.

In addition, in this embodiment, the pitch of the stripes and mother turns of the grating was formed to be slightly different from the track pitch at all positions, but as shown in Fig. 4, the pitch was different only in the center part). Alternatively, the pitches may be formed to be equal. In this case, the light intensity distribution received by the first and second optical sensors 24 and 26 is different from that when the phases match at the center as shown in FIG. It changes like the dotted line.

Note that the second light source 20 is used to project the stripe pattern.
The light source may be a laser, or may be another light source such as an LED, a discharge tube, or an incandescent light bulb. However, in order to reduce the influence of chromatic aberration of the optical system, it is desirable to use a relatively monochromatic light source.

If the projection magnification of the image onto the photodetector 16 is designed to be relatively large, the mounting accuracy may not be very high.

Tracks on a recording medium can be formed by changing the reflectance by changing the material, or by rotating the plane of polarization due to the magnetic Kerr effect, etc. But it's okay. However, if the polarization plane is rotated, it is necessary to make the incident light linearly polarized and to provide a polarizing element in the optical path leading to the light receiving element.

(9) The track on the recording medium may be created in advance on the recording medium separately from the recording data, or may be formed by the bit string of the recording data itself.

In the above example, the recording medium is described as a disk, but this can be done similarly even if it is in other shapes such as a tape shape or a card shape.

Furthermore, the light that irradiates the recording medium does not necessarily need to be irradiated through the objective lens, but rather to the side of the objective lens.

A light source may be provided on the recording medium, or if the recording medium is transparent, the light may be irradiated from the back side of the recording medium.

〔effect〕

As described above in detail and concretely, according to the present invention, the detection signal for tracking is obtained by averagely observing the recording track of the entire projected portion of the stripe pattern, so minute scratches, track defects, etc. has almost no effect. Therefore, reliable tracking can be performed.

Furthermore, the light irradiated (10) onto the recording medium for track position detection does not form a light beam that forms a minute spot, but forms a large stripe. Therefore, the area irradiated with light is approximately tens of thousands to several million times larger than a conventional spot where a laser beam is focused. However, even if a large light source with optical energy several hundred times that of a laser beam is used, the density of energy on the medium surface is extremely small, so tracking signals may cause negative effects on the medium, such as imprinting. There's nothing wrong with that. Furthermore, since a light source with large optical energy can be used, a good detection signal can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration principle of an optical information processing device according to an embodiment of the present invention, FIG. Graphs showing the light leakage distribution on the sensor, FIGS. 4 and 5, relate to another embodiment of the present invention and correspond to FIGS. 2 and 3, respectively. In the figure, 2...laser, 12...disk, 2
0... Second light source, 24... First light sensor, 26...
- Second optical sensor, 28...light detection means, 30... grating. 2 ■ Fig. 3 IM 4 Fig. 5

Claims (1)

[Claims] (1) In an optical information processing device that irradiates light emitted from a first light source onto a recording medium and detects reflected light or transmitted light from the recording medium; a second light source is provided; The image of the recording medium is formed on a light detection means consisting of at least two light sensors to form a striped light pattern. Turn forming means is provided in front of the light detecting means, and the stripe-shaped light/mother turn is parallel to the recording track on the recording medium and has a pitch slightly different from the pitch of the recording track. Optical information processing device.