JPS63157324A - Optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To prevent the trace of guide tracks for erasing and producing/ reproducing beams by having comparison between the reproduction signals received from both erasing and recording/reproducing spots, and controlling operation mode according to the comparison result. CONSTITUTION:The signal of a long wavelength that can read the signal recorded at the preamble of a preformat part in a sector even with an erasing light spot stopped down to an ellipse is recorded on a guide track T1. The wavelength, the phase, the modulation pattern, etc., of said signal to be recorded are changed against adjacent tracks. The reproduction signal S5 read out of the erasing light spot and received from the preamble is compared with the reproduction signal S6 read out of a recording/reproducing light spot and received from the preamble. When the coincidence is obtained between both signals S5 and S6, the erasing and recording actions are carried out. These actions are inhibited if no coincidence is obtained between both signals. In this case, the erasing light spot is moved to trace the same desired guide track as the recording/reproducing beam. Then an erasing action and a new recording action are carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention focuses two laser beams onto an optical recording medium (for example, an optical disk) using a lens or the like into two minute optical spots, and focuses the beams into a circular shape. An optical system that records and reproduces signals using one optical spot that is narrowed in the direction of the track, and erases the signal using the other optical spot that is narrowed into an elongated shape in the track direction, thereby recording and reproducing erasable digital signals that can repeatedly record and reproduce signals. The present invention relates to an optical recording and reproducing device having a plurality of optical spots, such as an optical recording and reproducing device.

2. Description of the Related Art An optical recording/reproducing apparatus having a plurality of optical spots is described, for example, in Japanese Patent Application No. 125906/1983. This is an example of an erasable optical recording/reproducing device that uses the thermal energy of laser light to reversibly change the transmittance or reflectance of the recording thin film of an optical disk. Dislocations between states and crystalline states, or dislocations between one amorphous state and another stable amorphous state, etc. are repeatedly utilized.

The device as described above has a plurality (two) of light spots. An example of its configuration is shown in FIG. FIG. 4 is an enlarged view of a part of a disk-shaped optical recording medium (hereinafter referred to as an optical disk), T1 is a guide track provided on the optical disk, and a circular first light spot L is placed on the guide track T1. and a second oval light spot M elongated in the track direction, the first circular light spot L records and reproduces the signal, and the second oval light spot M erases the signal. It has become. Usually, in these devices, the length of the second light spot M in the track direction is several times longer than the length of the first light spot L in the track direction.

In the device using two optical spots as described above, since the width of the guide track T1 is generally very small, about 0.5 μm, the width of the first optical spot (hereinafter referred to as the recording/reproducing optical spot) is ) L and the second optical spot (hereinafter referred to as the erasing optical spot) M in the direction perpendicular to the track must be kept highly accurate and stable. For this reason, the above-mentioned device has a structure that prevents the relative positional deviation of the two light spots, and the structure is shown in FIG.

In FIG. 6, the part surrounded by a dashed line indicates an optical head, and a light beam l shown by a solid line is emitted from a semiconductor laser 2 that generates light with a wavelength λ1, and a light beam l shown by a solid line is emitted by a condenser lens 3. The output light is condensed into a substantially parallel light beam. 4 is an optical filter that transmits light of wavelength λ1 and reflects light of wavelength λ2, which will be described later; 6 is an optical filter of wavelength λ1. λ
Polarizing beam splitter effective for light 2, 6 is wavelength λ1
% wavelength plate for light.

The light beam l emitted from the semiconductor laser 2 passes through these optical elements and enters the aperture lens 7.

The aperture lens 7 narrows down the incident light beam L to create a substantially circular recording/reproducing light spot L on the guide track T1.

8 is a wavelength λ different from the wavelength λ of the light beam l.
2 is a semiconductor laser that generates a light beam m, and 9 indicates a condenser lens. Reference numeral 10 denotes a reflecting mirror, which is configured to be rotatable. Reference numeral 11 denotes a wavelength plate that corresponds to the wavelength λ2, and the optical filter 2 has a function of transmitting the light of the wavelength λ2 and reflecting the light of the wavelength λ2. The light beam m shown by the broken line emitted from the semiconductor laser 8 is reflected by the reflecting mirror 10 . After being reflected by the polarizing beam splitter 5 and passing through the wave plate 11, it is reflected by the optical filter 2 and passing through the wave plate 11 again. This time, the polarized beam passes through the polarization gripper 6, passes through the K wavelength plate 6, and then the diaphragm lens 7 forms an elliptical erasing light spot on the same guide track T1 as the light spot L, with its major axis direction coinciding with the direction of the guide track. Form M.

In order to arrange the light spots L and M on the guide track as shown in FIG. This can be achieved by having .

The reflected light from the optical disk of the light beam l is passed through the aperture lens 7.
+X wave plate 6. Polarizing beam splitter 6° wave plate 11
．． The light passes through an optical filter 12 and is guided to a photodetector 14 via a lens 13 for obtaining control signals for focusing and tracking. The photodetector 14 is composed of photodiodes divided into four parts, and reproduces signals from the outputs thereof using a known method.

A control signal for focusing and tracking of the optical spot L for recording and reproduction is obtained.

On the other hand, the reflected light of the light beam m from the optical disk passes through the aperture lens 7 and the wavelength plate 6. Here, for example, the wavelength λ
By using a semiconductor laser with wavelength 1 of 780 nm and wavelength λ2 of 830 nm, most of the light transmitted through the % wavelength plate 6 is reflected by the polarizing beam splitter 6 toward the semiconductor laser 2, and further reflected by the optical filter 4. A tracking control signal for the erasing light spot M is obtained from the differential output of the reflected and two-split photodetector 16. Aperture lens γ is aperture lens driving element 1
6, the optical axis direction for focusing and the radial direction of the optical disk perpendicular to the track for tracking.
It is held movably in the axial direction.

Therefore, the recording/reproducing light spot L and the erasing light spot M are moved simultaneously and by the same amount in the direction perpendicular to the track by the aperture lens drive element 16. This diaphragm lens driving element 16 may be a known voice coil type two-axis actuator, and can perform focus control of the recording/reproducing light spot L in response to surface runout of the optical disk and tracking control in response to track eccentricity and distortion using known technology. .

At this time, the erasing light spot M also moves in the same manner as described above. However, since a rotatable reflecting mirror 10 is provided in the optical path of the erasing light spot M, the erasing light spot M becomes independent from the recording/reproducing light spot L by rotating the reflecting mirror 1o. can be moved vertically to the track. This is because the angle of incidence of the light beam m incident on the aperture lens 7 in the direction perpendicular to the track changes.

As mentioned above, the tracking control signal of the erasing light spot M is obtained from the photodetector 16 which is composed of a two-split photodiode, but the tracking control signal of the erasing light spot M is obtained by using a known technique.
Tracking control of the erasing light spot M can be performed by rotationally driving the .

As described above, the first driving means moves the two light spots together in a direction substantially perpendicular to the track, and the second driving means moves the erasing light spot independently of the recording/reproducing light spot. In an optical recording/reproducing device having a plurality of optical spots, even if a relative positional deviation occurs in the track vertical direction of the two optical spots for some reason, the first and second driving By applying tracking control using the means, it becomes possible to accurately track the guide track, and it is possible to prevent relative positional deviation between the two light spots.

In addition, with the advancement of digital signal processing technology, these optical recording and reproducing devices record two audio images, image information, or computer programs and data as binary digital data on an optical disk. A device for reproducing this has been put into practical use. Generally, when recording these digital data, one round of the track is divided into n parts (n is an integer of 1 or more), and these divided parts are called sectors, and this sector is the minimum unit for recording and reproducing data. It is carried out. As shown in FIG. 6, this sector consists of a preformatted area filled with diagonal lines, and a non-preformatted area consisting of gaps and data recording areas.

The preformat section serves as a preamble for drawing in a phase synchronization control circuit (hereinafter referred to as PLL) in a reproduction circuit when reproducing a sector address, which will be described later, a sector address in which a sector address is written, and a buffer area. It consists of postamble etc. This preamble or postamble usually includes the signal with the shortest wavelength among the modulated signals (signal modulated with the minimum inversion interval).
is written for about several dozen wavelengths. Since the signal written at this minimum reversal interval has a short wavelength, it can be read by the circular recording/reproducing optical spot L, but cannot be read by the oval erasing optical spot M. I can't.

In the non-preformatted area, a data recording area where data is recorded and reproduced and a buffer gap are provided at both ends thereof.

Furthermore, in the non-preformatted area, guide tracks as shown in FIG. The necessary information is recorded by providing a height difference (unevenness) in the depth direction of a guide track, as is done on a read-only optical disc, and modulating the interval between the height differences. This preformatted information cannot be optically rewritten.

Problems to be Solved by the Invention There are various well-known methods for detecting the tracking signal in the above configuration, but when the track pitch TP is about 1.6 μm, the tracking control signal is generally As shown in the figure, the multivalued function (repetitive waveform) has a sine wave shape or a waveform close to it, with one period equal to the track pitch TP. Therefore, the guide track T in the same figure,
Even if the light spot is located at the center of the adjacent guide track T
. Even if the tracking control signal is located at the center of , the tracking control signal will be zero, and there will be many stable tracking points. Therefore, when tracking the two light spots respectively, the recording and reproducing light spot L as shown in FIG. 7 is located at the center of the desired guide track T1, and the erasing light spot M is located at a different guide track. Located at the center of 0,
Each may follow a different guide track.

When such a situation occurs, even if an attempt is made to rewrite data on the desired guide track T1, the erasing light spot M is on a different guide track T. Therefore, the data on the guide trunk T1 is erased, and the previously recorded data D in the desired guide trunk T1. Since the newly recorded data D1 is directly written on top of the D1, overwriting of data occurs, and both Dl and D0 data are destroyed, and even if this part is played back, accurate data playback cannot be performed. ing. Particularly when recording and reproducing computer programs and data, it can be fatal if signals recorded on undesired tracks are destroyed due to erasure, or data is destroyed due to overwriting on desired tracks. This is a serious drawback and must be avoided at all costs. Also, the allowable value for the relative positional deviation of two light spots on the same guide track is 0.
A very small value of 1 μm or less is required. For example, if the reflecting mirror 10 is fixed, even if the two light spots can be kept within the above-mentioned tolerance, the optical components and mounting may be damaged due to temperature changes. Distortion caused by contraction and expansion of the pedestal, or vibrations generated during transportation, storage, use, etc., can also distort the relative positional relationship of the optical components and cause the relative positional relationship of the light spots to shift. It becomes more difficult to keep the relative positional variation between the two beams within the permissible value of 0.1 μm, and this becomes impractical.

In view of the above, an object of the present invention is to provide an optical recording/reproducing device having a plurality of light spots, which has a simple configuration and can track two light spots on the same guide track.

Means for Solving the Problems The present invention records a signal recorded in a preamble of a preformat part in a sector as a long wavelength signal that can be read by the erasing optical spot M narrowed into an ellipse, Then, the wavelength 9 phase or modulation pattern of the signal recorded in this preamble is changed at least between both adjacent tracks, and the reproduced signal from the preamble read from the erasing optical spot M and the recording/reproducing optical spot L are changed. The reproduced signals from the read preambles are compared, and when they match, erasing and recording are performed, and when they do not match, erasing and recording operations are prohibited, and the erasing optical spot M is moved to record and reproduce. This is an optical recording/reproducing apparatus configured to perform erasing and new recording after tracing the same desired guide track as the optical beam L.

By configuring the present invention as described above, it is possible to prevent the erasing beam and the recording/reproducing beam from tracking different guide tracks.

Embodiment FIG. 1 is a block diagram of an optical recording/reproducing apparatus showing an embodiment of the present invention. In the optical system shown in the same figure, the same symbols are used for the same components as those shown in the conventional example shown in FIG. 4, and the portion surrounded by a dashed line as in FIG. 4 indicates an optical head.

In an optical recording and reproducing device for recording and reproducing digital signals as described in the present invention, it is generally necessary to write data in a specified sector, and a search is performed to find the track containing the specified sector. The optical head is moved to read the sector address written in the preformat section, and after this sector address matches a predetermined sector, recording is performed.

Now, in FIG. 1, the reflected light from the optical disk of the light beam L used for recording and reproduction is guided to the photodetector 14, which is composed of four-divided photodiodes, as in FIG. is obtained, and the recording/reproducing light spot L is focused.

A control signal for tracking is obtained, and focus control and tracking control are performed. The reproduced signal S1 is subjected to analog signal processing such as amplification and waveform equalization, and then converted into a waveform-shaped and binarized digital signal, which is then sent to the demodulation circuit 1.
Added to 6. The demodulation circuit 16 demodulates the reproduced signal from the light beam 1 to obtain a signal S2 as its output signal. Signal S2 is applied to detection circuit 17 and also to preamble detection circuit 18. The preamble detection circuit 18 detects the period during which the preamble of the preformat portion is reproduced, and receives a control signal S3, which will be described later, for causing the detection circuit 17 to store only the signal during the preamble reproduction period in the signal S2. A control signal S4 for causing the detection circuit 1 to store only the signal during the preamble reproduction period in the signal S7 is generated and supplied to the detection circuit 17.

On the other hand, the reflected light from the optical disk of the light beam m for erasing is also guided to a photodetector 16 composed of a two-split photodiode, similar to the conventional example shown in FIG. 4, to obtain a tracking control signal S6 of the light spot M for erasing. Along with the photodetector 1
The sum of the signals detected from the two-split photodiodes composing the light spot M is calculated, and this sum signal S8 is used as a reproduction signal of the optical spot M. Similar to the signal S1, this signal S is subjected to analog signal processing such as amplification and waveform equalization, then converted into a waveform-shaped and binarized digital signal, and then applied to the demodulation circuit 19. In the demodulation circuit 19, the optical spot M
demodulates the reproduced signal from S and outputs the signal S.
7 is obtained, and the signal S7 is applied to the detection circuit 17.

Now, as shown in FIG. 4, the optical spora l-L and M are irradiated at different positions in the track direction, and in order to perform erasing first, the optical spot M is in the earlier position, and the recording/reproducing The light spot L that performs this is arranged in such a manner that it follows the light spot L that performs this.

Also, these light spots are light spots M during recording.
Increase the irradiation intensity and perform erasing with strong light to create a light spot L.
creates a binary state in which a section is irradiated with strong light and a section in which no light is irradiated or is irradiated with weak light, and modulates and records this binary state based on a signal that records it.

During playback, the optical spot M reads the signal and does not destroy the signal recorded on the guide track in order to maintain a tracking controlled state and smoothly pull in the tracking when transitioning to recording. As is well known, the other light spot L is irradiated with a weak light that does not destroy the recorded signal to read the signal.

In the configuration described above, there is a difference in the time it takes for the light spots L and M to pass through the preamble section and read the signals written there. In other words, since the erasing light spot M is in the lead, the signal is read first, and the reproduced signal read from the subsequent recording and reproducing light spot M is delayed. The time difference ΔT of this delay depends on the distance ΔX in the track direction between the two M light spots and the linear velocity V for reproducing the guide track, and becomes ΔT:ΔX/V.

Therefore, in order to compare the preamble signals read from the light spots L and M in the detection circuit 17, it is necessary to correct only the time difference ΔT. Since the detection circuit 17 captures and compares data only when the light spots L and M reproduce the preamble section, the preamble detection circuit 18 uses two signals S3. S4 is created and added to the detection circuit 17, and the configuration is such that the signal S that controls the capture of the signal S7 operates first, and the signal S3 that controls the capture of the signal S2 operates subsequently. ing.

A specific example of the configuration of this detection circuit 17 is shown in FIG. 2, and a waveform diagram of each part is shown in FIG. In FIG. 2, the detection circuit 17 includes a first shift register 20. Second shift register 21.
The demodulated signal S2. S7 are applied to the data input terminals of the first shift register 20 and the second shift register 21, respectively, while the control signals S5°S6 are applied to the data input terminals of the first shift register 20 and the second shift register 21, respectively.
and the clock terminal (data read terminal) of the second shift register 21.

As mentioned above, the erasing optical spot M is several times longer than the recording/reproducing optical spot L in the track direction, so the signal recorded in the preamble is also a shorter optical spot than the signal written in other parts. The data is modulated and recorded with a wavelength several times longer than the length of the data, so that it can be read even by the erasing light beam M. Now, the reproduced signal from the erasing light beam M cannot read the signals recorded in the part other than the preamble, and therefore the demodulated signal S
is not in an unstable state as shown at 87 in FIG. 3, and an accurate demodulated signal can be obtained only during the preamble reproduction period.

On the other hand, the reproduced signal from the recording/reproducing light beam L can also be obtained from the preamble section and other regions modulated with a short wavelength, and as shown at 82 in FIG. 3, the time difference ΔT Playback of the preamplule starts after a delay of 100 min, and a demodulated version of the signal recorded in the preamble section is obtained.

Now, the control signal S6 is a control signal for writing the data of the demodulated signal S7 during the preamble reproduction period of the erasing light spot M into the second shift register 21, and is erased as shown at 56 in FIG. During the preamble reproduction period of the optical spot M, the preamble is reproduced at a rate matching the data reproduction speed of the demodulated signal S7, that is, at a rate at which one clock pulse is generated for every one bit of demodulated data. This signal generates the same number of pulse trains as the number of data in focus. With this configuration, only data during the preamble reproduction period is written into the second shift register 21. This data then becomes the output signal S of the second shift register 21. This signal S9 is applied to the arithmetic circuit 22 as a parallel bit signal as shown in FIG. 3, for example.

On the other hand, the control signal S6 also outputs the data of the demodulated signal S2 during the preamble reproduction period of the optical spot L for recording and reproduction.
As shown in 86 in FIG. 3, this is a control signal for writing to the system register 2o, and is equivalent to the signal S6 delayed by the time difference ΔT, so that the optical spot L for recording and reproduction is
During the preamble reproduction period, the signal is made to match the reproduction speed of the demodulated signal S2, and generates a pulse train of the same number as the focus on the number of data reproduced from the preamble. With this configuration, data during the preamble reproduction period is also written to the first shift register 2o, and this data is applied to the arithmetic circuit 22 as the output signal S8 of the first 77 register 20.

This signal S8 is a parallel bit signal as shown in FIG. 388, and is generated with a delay from the signal S9 by the time difference ΔT.

Now, the reflecting mirror 10 is rotatable for tracking control, but its movable range is between the light beams L and M when the tracking control system of the erasing light spot M is stopped. It is sufficient that the displacement exceeds the deviation Δr in the track vertical direction, and there is no need to provide a larger movable range.

As a result of experiments under various conditions, it is difficult to guarantee that this Δr is less than the above-mentioned deviation tolerance value of 0.1 μm when an appropriate optical head is designed by practical means, but the track pitch TP ( TP=approximately 1.6 μm) or less. Therefore, the movable range is ±TP
(approximately ±1.6 μm), that is, it is sufficient to be able to move slightly more than TP on both sides from the neutral position, and a stopper mechanism is provided to restrict the movable range so that the reflecting mirror 1o does not move any further. . As a result, when tracking control is performed for two systems of light beams L and M,
Even if for some reason the two light beams track different guide tracks, the guide track 1 tracked by the light beam L will be the same as the guide track 1 tracked by the other light beam M. It doesn't deviate more than a book. In other words, even though the guide tracks tracked by the light beam M may be located on both sides of the guide track 1, they will not be further away from each other because they are regulated by the stopper mechanism.

Therefore, the guide track tracked by the light spot M matches the guide track 1;

■ Located on the inside adjacent track.

■ Located on the outer adjacent track.

It is only necessary to be able to determine which of the three states it is in,
The signal to be recorded in the preamble may be frequency modulation, two-phase modulation, a combination thereof, or three or more types of j+1 modulated based on various digital modulation methods.
The signals Sa0 to Saj of different types (i is an integer of 2 or more) are configured, the same signal is written on the same guide track, and the signals are written sequentially from the inner circumference to the outer circumference or from the outer circumference to the inner circumference for each guide track from Sa0 → Sa1 →・The signals are recorded in the preambles on all the guide tracks by repeating the sequence . . .→Saj.

Further, the arithmetic circuit 22 calculates the difference between the signals S8 and S9, and outputs a write inhibit control signal S1o and a track jump pulse signal S11 in accordance with the difference. As shown in FIG. 1, the recording prohibition control signal S1° is
The track jump pulse signal "11" is added to the adder circuit 26 together with the output signal S12 of the tracking control circuit 26, and the mixture of both becomes a signal "13" which is added to the drive circuit 27. It will be done.

Further, the tracking control circuit 26 controls the control signal S based on the tracking control signal S6 from the photodetector 16.
12 is output and supplied to the drive circuit 27 via the adder circuit 26 to control the rotation of the reflection mirror 1o, and the erasing light beam M
The system performs tracking control to track the guide trunk.

Now, when the erasing optical spot M and the recording/reproducing optical spot L are on the same guide track, the signal S8. S9 matches, the calculation result of the calculation circuit 22 becomes zero, and the write prohibition control signal S1° cancels the write prohibition for the first and second semiconductor laser drive circuits, and the above-described erasing and recording operations are performed. becomes possible. At this time, the track jump pulse signal S11 is not generated, the output signal S of the tracking control circuit 26 becomes equal to the signal S13, and tracking control is performed such that the erasing light beam M directly tracks the guide track currently being tracked. will be held.

Further, when the optical spoilers L and M are not on the same guide track, the signal S8. S9 is also different from each other, and the arithmetic circuit 2
2 is this signal S8. Based on S9, the recording prohibition control signal S1o is set to a recording prohibited state, and erasing and recording operations of the first and second semiconductor laser drive circuits 23 and 24 are prohibited, and the positional relationship between the two party spots is calculated, and the position is determined. A track jump pulse signal S11 corresponding to the relationship is applied to the adder circuit 26, and a signal "13" obtained by superimposing the track jump pulse signal S11 on the control signal S1□ is applied to the drive circuit 27 to cause the optical spot M to jump on the track. , the tracked guide track is changed so that the light spot L is positioned on the same guide track.

Effects of the Invention By having the above configuration, according to the present invention, in an optical recording/reproducing apparatus having a plurality of light beams including a long oval light beam with respect to the longitudinal direction of the track, it is possible to perform recording in units of sectors. Since the positions of the two light beams can be confirmed, it is possible to quickly and reliably check whether the two light beams are tracking on the same guide track, even if they are not tracking the same guide track. Since it is possible to correct by making the erasing light beam M track jump, it is possible to erase undesired guide tracks by the erasing light beam M as described above,
A highly reliable optical recording/reproducing device can be realized without data destruction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a specific example of the detection circuit shown in FIG. 1.
Fig. 3 is a waveform diagram of the numbered part in the second drawing, Fig. 4 is a perspective view showing the arrangement of the optical disc and the optical spot, Fig. 6 is a plan view showing the previously proposed device, and Fig. 6 is the inside of the sector of the optical disc. Fig. 7 is a perspective view showing the arrangement of the optical disc and the optical spots when the guide tracks tracked by two optical spots are different, and Fig. 8 is an explanatory diagram showing an example of the format of the optical disc. FIG. 3 is a relationship diagram of tracking control when moving. L... Light spot for recording and reproduction, M...
Erasing light spot, 1...Guiding track followed by the recording/reproducing light spot, 16, 19...
・Demodulation circuit, 17...Detection circuit, 18...
・・Preamble detection circuit, 20・・First shift register, 21・A・・Second shift register, 22・
... Arithmetic circuit, 23 .... First semiconductor laser drive circuit, 24 .... Second semiconductor laser drive circuit, 26 .... Tracking control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 6 Figure 7

Claims (1)

[Claims] Using two semiconductor lasers with different wavelengths and the same aperture lens, we combine the light beams emitted from these two semiconductor lasers into two beams on a straight line approximately parallel to the information track of an optical recording medium. an optical means configured to form a spot, and to form a leading light spot M in an oval shape elongated in the track direction, and to form a subsequent light spot L in a substantially circular shape, and a direction substantially perpendicular to the information track; a first driving means for moving the two light spots L, M together;
, M for moving one of the optical spots in a direction substantially perpendicular to the information track; A long-wavelength preamble that can be read by the optical spot M is added before the sector address, and a signal that is the same on the same information track but different on at least adjacent information tracks is written to this preamble. The optical recording medium is connected to the light spot L.
. Based on the difference signal, one of the light spots is moved using the second driving means to create two light spots L and M.
an optical recording/reproducing device comprising: means for track jumping so that the information tracks tracked by the optical discs are the same;