JPH0411332A - Optical disk device - Google Patents

Abstract

PURPOSE:To realize a device having a high reliability and the read after write function by detecting the positional deviation between two beams by an optical disk device using a two-beam laser light source. CONSTITUTION:Laser light 3 from a laser array 1 is converged on a disk medium 13 by an objective lens 7, and the reflected light from a disk medium 13 passes the objective lens 4 and a lambda/4 wave plate 6 again and is reflected by a deflecting prism 5 and passes a 4-divided prism 11 and a lens 10 and is received by a 6-divided sense array 12 to obtain an information signal and a servo signal. An off-track two-beam signal is obtained from the servo signal through an amplifying operation circuit 16 by an off-track two-beam detecting circuit 17 and is sent to a control circuit 21. If the off-track two-beam signal has an abnormal value larger than a set value, the control circuit 21 sends an alarm signal to a host device to stop the optical disk device. Thus, the high-speed disk device having a high reliability and the read after write function is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc device using a two-beam optical head.

[Conventional technology]

In recent years, optical disks have been developed as large-capacity and inexpensive storage devices, and are beginning to be put into practical use as sofile memory image memories for office automation.

However, although optical disks are superior in terms of large capacity compared to conventionally widely used magnetic disks, on the other hand, data transfer speeds and access speeds are slow, which is a problem.

As a method to achieve such high speed optical discs,
Conventionally, efforts have been made to increase the rotation speed of optical disks and to make them multi-beam.

[Problem to be solved by the invention]

As a method for increasing the speed of optical discs by using multiple beams, an optical disc using an optical head using a laser array has been proposed.

One method is to irradiate multiple light beams onto different tracks on the disk, recording and recording multiple tracks at the same time.
There is a parallel recording/playback method for playback. Another method is to irradiate the same track with two or more light beams, record with one light beam, and perform playback with the other light beam, instead of the conventional method of rotating the disk twice. There is also a read-after-write (RAW) method that allows recording and confirmation processing to be completed in one revolution.

The read-after-write method is expected to have future potential as it can be applied to conventional optical disk devices to increase speed without major system changes.

In a laser array, it is necessary to monitor the focusing state of each laser beam on a disk, and in particular, the mutual positional relationship between the tracks on the disk and each laser beam is important. In actual equipment, if the laser light source or optical system is misaligned for some reason, when one laser beam is aligned with the track center, other laser beams are shifted from the track center, which is called off-trunk. There are things to do.

However, in the conventional technology, the only countermeasure against such off-track problems is to mechanically align the positional relationship between the track and each laser beam in advance, and there is no known means for detecting the occurrence of an abnormality. .

The present invention aims to solve the problems of the prior art, and makes it possible to detect the positional deviation of two beams in an optical disk device using a two-beam laser light source, thereby improving the signal trajectory. The purpose is to realize a high-speed optical disk device with high read-after-write functionality.

[Means for Solving the Problems] The present invention includes a laser light source including a laser array having a first laser and a second laser, and a method for transmitting the first laser light and the second laser light onto a medium. The optical system has an optical system that focuses light on different positions of the laser beam and focuses reflected light based on each laser beam on different two divided sensors of the divided sensor array.

Further, a laser driving device sequentially causes the first laser beam and the second laser beam to emit light using read power, and a two-split sensor receives the reflected light from the track by the first laser beam and the second laser beam, respectively. The apparatus includes an amplification calculation circuit that obtains a first tracking error signal and a second tracking error signal based on the difference output when the tracking error is performed.

The configuration further includes an off-track two-beam detection circuit that generates an off-track error signal when the difference between the signals obtained by sampling and holding the first tracking error signal and the second tracking error signal is a set value or more. I'm taking it. This aims to achieve the above-mentioned purpose.

[For production]

The first laser beam and the second laser beam of the laser light source are focused on different positions on the medium 13, and the reflected light based on each laser beam is focused on different two divided sensors of the divided sensor array by an optical system. so that the light is focused on

The first laser and the second laser are made to emit light sequentially using read power, and the difference output when the reflected light from the track by the first laser beam and the second laser beam is received by the two-split sensor is used to generate a second laser beam. The first tracking error signal and the second tracking error signal are obtained, and when the difference between the signals obtained by sampling and holding the first tracking error signal and the second tracking error signal respectively is equal to or greater than a set value, an off-track error signal is obtained. occurs.

Therefore, the inclination of the two beams from the track can be detected at all times, and a warning can be issued when an abnormality occurs.

〔Example〕

FIG. 1 shows an embodiment of an optical disc device according to the present invention.

The optical disc apparatus shown in FIG. optical systems 4 to 7.10.11 which condense reflected light based on each laser beam onto different two divided sensors of the divided sensor array 12;
and a second laser sequentially emit light using read power.

Further, the first tracking error signal 42 and the second tracking error signal 41 are generated by the difference output when the reflected light from the track 14 by the first laser beam and the second laser beam is received by the two-split sensor, respectively. The off-track two beam has an amplification calculation circuit 16 to obtain an off-track error signal and generates an off-track error signal when the difference between the signals obtained by sampling and holding the first tracking error signal 42 and the second tracking error signal 41 is greater than or equal to a set value. A circuit 49 is provided.

The laser array 1 has two laser light sources driven by a laser drive device 15. The laser beam 3 from this laser array 1 is transmitted to a collimator 4. Polarizing prism (
PBS)5. After passing through the λ/4 wavelength plate 6, the objective lens 7
is focused onto the disk medium 13 by. In this state, the light beam is separated into a first laser beam and a second laser beam, which are focused on different points on the same track.

The reflected light from the disk medium 13 is again passed through the objective lens 4.
It passes through the λ/4 wavelength plate 6, is reflected by the polarizing prism 5, and is reflected by the 4-split prism 11. Lens 10. An information signal and a servo signal are obtained by receiving the light by the six-divided sensor array 12.

Further, the servo signal is passed through the amplification calculation circuit 16, and is then sent to the off-track 2 beam detection circuit 17.
A beam signal is obtained and sent to the control circuit 21.

When the off-track 2 beam signal reaches an abnormal value greater than the set value, the control circuit 21 sends an alarm signal to the host device, thereby stopping the optical disk device.

In FIG. 1, a signal indicating the amount of light emitted from the laser array 1, which is detected by the monitor 2, amplified and inputted through the amplifier circuit 18, is fed back to the laser drive circuit 15 via the control circuit 21. As a result, control is performed to stabilize the intensity of laser light in the laser array 1.

FIG. 2 shows details of the signal detection system in the embodiment of FIG. 1.

The disk reflected light 30 enters the four-split prism 11,
The transmitted light is focused by the lens 10 onto the six-divided sensor array 12, but the four-divided prism 11 is diagonally divided into four surfaces, and each surface is set to have a different width.

The light that has passed through the surface a is incident on one of the two-divided sensors for detecting a focus error signal located at the center of the six-divided sensor array 12. Further, the light that has passed through the facing surface similarly enters the other two-divided sensor for detecting the focus error signal in the six-divided sensor array 12. Depending on whether the disc reflected light 30 is convergent light or diverging light, the amount of light received by these two-split sensors becomes asymmetrical due to the Knifezi effect, and a difference signal is extracted as a focusing error signal 43.

Further, the light transmitted through the surface C2 and the surface d passes through the lens 10 and passes through the lens 6.
The light is incident on a single sensor on both sides of the divided sensor array 12, respectively. A difference signal between the amounts of light received thereby becomes a tracking error signal.

Since the disc reflected light 30 is reflected light from two laser light sources, after passing through the lens 10, it is separated into a first laser light 37 and a second laser light 36, as shown in FIG. On the six-divided sensor array 12, the light is focused on different six-divided sensors located at different positions up and down. Therefore,
A first tracking error signal 42 is obtained from the first laser beam 37, and a second tracking error signal 41 and a focusing error signal 4 are obtained from the second laser beam 36.
3 is obtained. Furthermore, the information signal 44 is obtained by summing the signals of the two-split sensor described above.

The first tracking error signal 42 and the second tracking error signal 41 are transmitted to the off-track two beam detection circuit 1.
7, an off-track two-beam signal 48 is obtained. The off-track two-beam detection circuit 17 is composed of sample and hold circuits 45 and 46 and a summer processing circuit 47.

FIG. 3 shows signal processing in the off-track two-beam detection circuit 17.

When loading a disc, each laser light source is made to emit light with read power. When the first laser emits light by the first laser driving pulse shown in (2), the first tracking error signal at time t is sampled and held. When the second laser emits light by the second laser drive pulse, the second tracking error signal at time t2 is sampled and held. If the difference between these tracking error signals is determined at time t, an off-track two-beam signal 48 is obtained.

By obtaining this off-track 2-beam signal at any time and comparing it with a set value, it is possible to constantly detect the inclination of the 2-beam from the track, and to issue a warning in the event of an abnormal order.

In the above embodiments, an optical system using a 4-split prism was explained as a servo optical system, but the invention is not limited to this. It is also possible to implement the configuration of the present invention in the same manner.

〔Effect of the invention〕

As explained above, according to the present invention, since the positional deviation of two beams is detected in an optical disk device using a two-beam laser light source, highly reliable read-after
A high-speed optical disc device having a write function can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an optical disc device according to the present invention, FIG. 2 is a diagram showing details of a signal detection system in the embodiment of FIG. 1, and FIG. 3 is a diagram showing signal processing in an off-trunk two-beam detection circuit. FIG. 1-Laser array, 4-7, 10.11-Optical system, 12
-6-divided sensor array, 13-medium, 14...-track, 15...laser drive device, 17--off track 2 beam detection circuit, 41.42...-tracking error signal. Figure 1 (V sword key 14 lines) (Tenzu 7 points) Applicant Japan Electric Co., Ltd. Agent Patent attorney Isamu Takahashi (Dan'PCC) 74 points

Claims (1)

[Claims] (1) A laser light source consisting of a laser array having a first laser and a second laser;
an optical system that focuses the laser beams on different positions on the medium, and focuses reflected light based on the respective laser beams on different two divided sensors of the divided sensor array; and a laser driving device that sequentially emits light from a laser using a read power, and a second laser beam is generated based on a difference output when the reflected light from the track by the first laser beam and the second laser beam is received by the two-split sensor, respectively. Equipped with an amplification calculation circuit that obtains the first tracking error signal and the second tracking error signal, the difference between the signals obtained by sampling and holding the first tracking error signal and the second tracking error signal is greater than or equal to a set value. An optical disc device comprising an off-track two-beam detection circuit that generates an off-track error signal when the off-track error occurs.