JP2539433B2 - Beam position controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical disk storage, and more specifically, to increase recording power by combining two laser beams and by parallel recording with two laser beams. The present invention relates to a beam position control device for the purpose of improving the data transfer rate of optical disk storage.

[Prior Art] In a conventional optical disk storage device, a high-power semiconductor laser is required in order to improve the data transfer rate. Further, in order to realize parallel recording or simultaneous recording / reproduction using two laser beams, in order to always keep the positions of the two laser beams at constant intervals, an optical system such as a lens or a half mirror is assembled with high accuracy. Was necessary. Then, when the positional deviation occurs due to temperature, aging, etc., the positions of these optical systems are readjusted.

[Problems to be Solved by the Invention] However, in order to improve the data transfer rate, a high output semiconductor laser is required, and thus there is a problem that the data transfer rate is limited by the output of the semiconductor laser. It was Further, in order to realize parallel recording or simultaneous recording / reproducing using two laser beams, it is necessary to improve the assembly accuracy of the optical system, and it is troublesome to readjust the position of the optical system. It was

The present invention has been made in view of such circumstances, and an object thereof is to improve the data transfer rate,
While increasing the recording power by combining two beams,
It is an object of the present invention to provide a beam position control device that realizes two-beam parallel recording and the like without requiring high precision and adjusting the position of an optical system with respect to temperature and aging.

[Means for Solving Problems] A beam position control device of the present invention includes two laser light sources having different wavelengths, a movable mirror for two-dimensionally changing the direction of a laser beam emitted from the laser light source, and two laser light sources. An optical system for condensing the laser beam on the medium surface, a filter for wavelength-separating the laser beam reflected on the medium surface, and two filters on the medium surface from the two wavelength-separated laser beams.
A positional deviation detection circuit for detecting positional deviations of the two laser beams in the radial direction and the circumferential direction, and a mirror direction control circuit for controlling the direction of the movable mirror based on a detection signal of the positional deviation detection circuit. Is characterized by.

[Operation] The beam position control device of the present invention controls the focus position of the laser beam on the disk surface by using the movable mirror that can control the direction of the laser beam two-dimensionally. The recording power is increased by matching the condensing positions, and parallel recording or simultaneous recording / reproducing is realized by maintaining the condensing positions of the two laser beams at a constant interval.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a basic block configuration diagram. In FIG. 1, 1 and 2 are laser light sources having different wavelengths (λ1, λ2). The beam of one laser light source 1 is a half mirror 3,
The waveform shaping lens 4 and the beam splitter 5 focus the light on the disk medium 6. The beam of the other laser light source 2 is reflected by the movable mirror 7, and then focused on the disk medium 6 by the half mirror 3, the waveform shaping lens 4, and the beam splitter 5. The movable mirror 7 is two-dimensionally changed in direction of the beam of the laser light source 2 by being controlled by the mirror driving unit 8. In the case of this embodiment, the two beams from the laser light sources 1 and 2 are adapted to be coincident with each other on the disk medium 6.

The two beams reflected from the disk medium 6 pass through the wavelength separation filter 9 as a combined laser beam, and are separated into two beams B1 and B2 having different wavelengths (λ1, λ2). The beam B1 having the wavelength λ1 is the optical signal detectors 11a and 11b.
Is focused on. The optical signal detector 11a detects the RF signal and the focus signal from the beam B1, and the optical signal detector 11b detects the track error signal from the beam B1. On the other hand, the beam B2 of wavelength λ2 is the optical signal detector 12
It is focused on a and 12b. Optical signal detector 12a is from beam B2 to RF
The signal and focus signal are detected, and the optical signal detector 12b is for detecting a track error signal from the beam B2.

The detection signals S1a, S1b, S2a, S2b from the respective optical signal detectors 11a, 11b, 12a, 12b are input to the beam position deviation detection circuit 13, which detects the radial direction and the circumference of the two beams. Detects positional misalignment. The detection method will be described later. The detection signals S3 and S4 from the detection circuit 13 are input to the mirror drive control circuit 14, and this control circuit 14 controls the movable mirror 7 so that the positional deviation of the two beams on the disk medium 6 becomes zero. Outputs a mirror control signal. Then, the mirror drive section 8 automatically controls the movable mirror 7 based on the mirror control signal.

FIG. 2 is a specific configuration example. In the case of this example, 2
Waveform shaping lenses 4a and 4b and two beam splitters 5
It has a configuration including a and 5b and two wavelength separation filters 9a and 9b. Basically, it is the same as FIG. 1 described above.

Next, the beam position deviation detection circuit 13 will be described (see FIGS. 3 and 4).

The detection circuit 13 obtains the difference between the track error signals S1b and S2b for the beams B1 and B2 by the track error signal difference detection circuit 13a, and outputs a radial displacement signal S3. On the other hand, the positional deviation signal S4 in the circumferential direction is the address portion 6a written in advance on the disk medium 6 (FIG. 4).
It is obtained by using the phase difference of the VFO signal S5 obtained from That is, in the address section 6a, signals such as sector marks and VFOs have already been written, and the RF signals from the optical signal detectors 11a and 12a are band-pass filters 13b and 13c.
Extract the VFO signal by passing it through. Then, the phase difference detection circuit 13d obtains and outputs a shift signal S4 in the circumferential direction of the two laser beams on the disk medium 6 from the phase difference between the VFO signals.

Thus, the radial position shift signal S3 and the circumferential position shift signal S4 output from the beam position shift detection circuit 13 are input to the mirror drive control circuit 14, and the control circuit 14 controls the disk medium. A mirror control signal for controlling the movable mirror 7 is output so that the positional deviation between the two beams on 6 is zero. Therefore, the mirror drive unit 8
Controls the movable mirror 7 based on the mirror control signal to automatically match the positions of the two laser beams on the disk medium 6.

By the way, as another method of obtaining the positional deviation signal S4 in the circumferential direction, the phase difference of the clock output of the PLL system obtained from the optical signal processing circuit can be used (see FIG. 5). That is, in the optical disc device, one optical reproduction signal 1 is used in order to synchronize the reference clock signal of the signal encoding / decoding circuit with the clock signal obtained from the synchronization preformat mark previously embedded on the optical disc. The reference clock 2 is passed through the sync signal discrimination circuit 21a and the frequency division / clock generation circuit 22a, and then in the phase comparator 23.
A phase difference signal S6 from the clock signal of 4 is obtained. In the case of the present embodiment, a clock signal obtained from the other optical reproduction signal 2 by adding a synchronization signal discriminating circuit 21b and a frequency dividing / clock generating circuit 22b to the signal processing system of the other optical reproduction signal 2. And the clock signal obtained from the one optical reproduction signal 1 described above are compared by the phase comparator 25, and the circumferential position shift signal S4 is obtained from the phase difference between them and output.

In the above-described embodiment, the movable mirror 7 is controlled on the disk medium 6 so that the positions of the two laser beams coincide with each other, but the positions of the two laser beams are held at a constant interval. It is also possible to control the movable mirror 7 as described above.

[Effect] As described above, according to the present invention, the recording power can be increased and the data transfer rate can be improved by matching the two beam positions. Also,
By controlling the distance between the two laser beams to be constant, parallel recording or simultaneous recording / reproduction can be performed, and the data transfer speed and the function can be improved.

Also, by using this beam position control device, even if the position of the optical system such as laser light source, optical signal detector, half mirror, etc. is shifted due to the influence of temperature, aging, etc., the position shift is automatically compensated. be able to.

[Brief description of drawings]

FIG. 1 is a basic block configuration diagram of the present invention, FIG. 2 is a specific configuration example of an optical system, FIG. 3 is a configuration example of a beam position deviation detection circuit, and FIG. 4 is a circumference of two beams. FIG. 5 is a diagram for explaining the procedure for detecting the positional deviation in the direction, and FIG. 5 is an explanatory diagram of another embodiment for detecting the positional deviation in the circumferential direction. 1,2 ... Laser light source, 3 ... Half mirror, 4 ... Waveform shaping lens, 5 ... Beam splitter, 6 ... Disk medium, 7 ... Movable mirror, 8 ... Mirror drive unit, 9 ... Wavelength Separation filter, 11a, 11b, 12a, 12b ... Optical signal detector, 13 ... Beam position deviation detection circuit, 14 ... Mirror drive control circuit.

Front Page Continuation (72) Inventor Tatsuda Ritsu 3-9-11 Midoricho, Musashino City Nippon Telegraph and Telephone Corporation Electronic Engineering Laboratory (56) References JP-A-61-220154 (JP, A) JP-A-62 -212941 (JP, A) JP-A-61-133045 (JP, A)

Claims (2)

(57) [Claims] 1. A laser light source having different wavelengths, a movable mirror for two-dimensionally changing the direction of a laser beam emitted from the laser light source, an optical system for converging the two laser beams on a medium surface, and a medium. A filter for wavelength-separating the laser beam reflected by the surface, a positional deviation detection circuit for detecting positional deviations of the two laser beams on the medium surface in the radial direction and the circumferential direction from the two wavelength-separated laser beams, and A beam position control device comprising: a mirror direction control circuit that controls the direction of the movable mirror based on a detection signal of a position shift detection circuit. 2. A position shift detecting circuit for detecting a position shift in the circumferential direction based on a phase difference between VFO signals obtained from an address section, as a position shift detecting circuit in the circumferential direction between two laser beams on a medium surface. The beam position control device according to claim 1, wherein: