JP2805064B2 - Optical recording / reproducing device - Google Patents

Description

The present invention relates to a method for deflecting and scanning a laser beam by an acousto-optic deflecting element to write information on an optical recording medium and read information recorded on the optical recording medium. The present invention relates to an optical recording / reproducing apparatus capable of performing the above.

[Summary of the Invention]

The optical recording / reproducing apparatus of the present invention forms a laser beam output from a semiconductor laser or the like into a predetermined laser beam light, and then enters a first acousto-optic deflecting element forming a sub-scanning deflection system, Next, since the laser beam is incident on the second acousto-optic deflecting element forming the deflecting system for main scanning, the laser beam output from the second acousto-optic deflecting element is 2.
A pseudo multi-beam that scans the next surface can be used, thereby improving the recording / reproducing transfer speed and facilitating tracking servo during reproduction.

[Related Art] Irradiating an optical recording medium with a light beam, particularly a laser beam,
An apparatus for recording information or an apparatus for reproducing pit information recorded on an optical recording medium (hereinafter referred to as an optical recording / reproducing apparatus) can achieve an extremely high recording surface density. The one using a rotating body as a recording medium has been widely put into practical use as a CD player, a VD player, and a data filing system.

[Problems to be solved by the invention]

However, in the case of using a rotating disk as an optical recording medium, the size is physically limited, so that the recording information is limited and at the same time, a single laser beam is irradiated on the recording medium, For recording / playback,
Since the driving speed of the recording medium is mechanically limited, the transmission speed of information is also limited.

Therefore, a multi-channel recording / reproducing method using a multi-beam semiconductor laser has been proposed. However, when a multi-laser array is used, the modulation system and optical system of each laser beam become complicated, and the laser There is a problem that it is also difficult to accurately operate various servo mechanisms for controlling the beam.

[Means for solving the problem]

The present invention has been made in view of such a problem, and a first acousto-optic deflecting element capable of deflecting a laser beam output from a laser emission source at a relatively high speed in a predetermined direction in a first direction. A second acousto-optic deflecting element capable of outputting a laser beam scanned in this first direction at a relatively large deflection angle. Scanning is performed in a second direction substantially orthogonal to the optical deflecting element.

Then, by irradiating the two-dimensional scanning beam onto an optical recording medium in the form of a tape via an objective lens, information can be recorded or reproduced.

[Action]

Since the laser beam applied to the optical recording medium can be scanned in a two-dimensional direction, the recording track is configured in units of planes, and the conventional optical recording / scanning using a single laser beam is performed. It is possible to increase the transmission speed and the recording surface density higher than the reproducing apparatus.

Further, since the recording track by the main scanning is formed by the track of the short sub-scanning laser beam, the tracking control can be performed by the electric control, and the servo system is simplified.

〔Example〕

FIG. 1 shows an embodiment of an optical recording / reproducing apparatus according to the present invention, in which 10 is a semiconductor laser outputting laser light,
11 indicates a laser beam output from the semiconductor laser,
In the case of an optical recording apparatus, the laser beam 11 is modulated based on recording information applied to the semiconductor laser 10.

Numeral 12 denotes a collimator having a predetermined spot diameter 13 for the laser beam. The collimator 12 includes an optical element for polarizing the plane of polarization of the laser beam as necessary.

Reference numeral 14 denotes a first acousto-optic deflecting element, as shown in FIG. 2, comprising a medium 14C that transmits light, a piezoelectric element 14A that generates ultrasonic waves, and a sound absorbing material 14B.

As is well known, this acousto-optic deflecting element applies an ultrasonic signal to the piezoelectric element 14A to form an ultrasonic compression wave in a medium, and a predetermined pressure is applied from a direction substantially orthogonal to the direction in which the compression wave travels. The laser beam is deflected by irradiating the laser beam 11A at an angle of. The deflection angle (Bragg angle) θ is determined by the frequency of the applied ultrasonic signal (wavelength of compressional wave Λ) and the laser beam. Beam wavelength (λ)
Is set by

An optical element 15 converges the divergence angle of the laser beam 11B deflected by the acousto-optic deflecting element 14 and, if necessary, polarizes the plane of polarization of the output laser beam 11B. The first acousto-optic deflection element 14
Are arranged in a direction (X-axis direction) in which this deflection direction is orthogonal. And the first acousto-optic deflecting element
Similarly to 14, an ultrasonic signal is also applied to the electrode of the piezoelectric element 16A, and the output beam scans in the X-axis direction.

17 is a cylindrical lens, 18 is a collimation lens that makes the output beam deflected by the second acousto-optic deflecting element a parallel light beam, 19 is a deflecting beam splitter for separating the reproduction laser light reflected from the recording surface, and 20 is Tape-shaped recording medium
An objective lens for irradiating a laser beam focused on 21 is shown. By this objective lens 20, for example, a recording medium 21
A laser spot of about 1 μm is formed on the recording surface, and the return light reflected by the recording medium 21 is effectively picked up to read the recorded information.

An optical system 30 irradiates the return light separated by the deflection beam splitter 19 to an optical detector 31 having several light receiving surfaces with a predetermined beam diameter, and converts a laser beam incident on the optical detector 31 into an electric signal. Then, the recording data is read from the electric signal, and various servo error signals can be detected by an electric operation process.

Here, 32 is a modulation signal source of the semiconductor laser 10, 33 is a first ultrasonic frequency sweep signal source applied to the first acousto-optic deflecting element 14, 34 is a power amplifier, 35 is a second acousto-optic deflecting element. A second ultrasonic frequency sweep signal source applied to 16, 36 indicates its power amplifier.

Since the optical recording / reproducing method of the present invention is configured as described above, when used as a recording device, the output power of the semiconductor laser 10 is set high, and the intermittent control is performed by data supplied from the modulation signal 32. Is done. Then, the first acousto-optic deflecting element 14 is irradiated via the collimator 12.

As shown in FIG. 3, the first acousto-optic deflector 14 has
Since a signal S _{Y in} which the ultrasonic frequency continuously changes from f _1Y to f _2Y at a predetermined cycle T _y is applied, the output laser beam has a deflection angle θ (Bragg angle) corresponding to the sweep frequency. changes, will be swept in the Y-axis direction with a period T _y. Then, the laser beam scanned in the Y-axis direction is incident on the second acousto-optic deflecting element 16 via the optical element 15, and is deflected in the X-axis direction by the second acousto-optic deflecting element 16. Will be done.

The ultrasonic signal S _X applied to the second acousto-optic deflection element 16
Is the period T _x from f _1X to f _{2X as} shown in FIG.
, And the period T _x is the first
Longer than the period T _y of acousto-optic deflector incoming sweep signal. Therefore, when the laser beam is deflected by the second acousto-optic deflecting element, the sub-scanning beam of the scanning width is relatively small but fast period T _y further, the scanning width is increased, the period T _x is relatively slow will be deflected by the main scanning beam, the recording medium 21, the period T _y a plurality of sub-tracks engraved by _{X 1, X 2, X 3} ...... was set collection trucks 21
A is formed by one scan of the second acousto-optic deflection element.

When the recording medium 21 is moving at a predetermined speed v, as shown in FIG. 3, an aggregate track 21A in which a plurality of sub-tracks are aggregated is defined as Z ₁ , Z ₂ , Z _3. Are sequentially formed in the traveling direction.

The sweep signal applied to the first and second acousto-optic deflecting elements 14 and 16 is set to be Y _Y × N Y _{X where the} number of tracks of the sub-scanning beam is N, and the period T of the main scanning beam is set. _x and CTL signal 2 recorded on tape-shaped recording medium 21
The tape speed is set so that the period of 1B matches.

First acousto-optic deflecting element 14 for forming a sub-scanning beam
Is required to respond to a relatively fast cycle with a small sweeping distance.For example, it is preferable to use an isotropic acousto-optic deflecting element in which the sound velocity of the medium is fast, but the The second acousto-optic deflecting element 16 is preferably an anisotropic Bragg-type acousto-optic deflecting element having a large deflection Bragg angle in order to increase the scanning width although the scanning speed is low.

Since the optical recording / reproducing apparatus of the present invention is configured as described above, the relative speed between the recording medium 21 and the laser spot can be increased, and the transmission speed can be increased. In addition, since most of the scanning of the recording track is performed by the deflection control of the optical system, it is easy to perform the tracking control.

That is, tracking can be performed by controlling the phases of the sweep signals S _Y and S _X applied to the first and second acousto-optic deflecting elements 14 and 16 based on the tracking error information. Except for the system or the card driving system, the mechanical servo mechanism can be almost unnecessary.

In the above embodiment, a sweep signal having a continuously changing frequency is applied to the first acousto-optic deflector 14 from the outside. However, as a second embodiment, the first acousto-optic deflector 14 is applied to the first acousto-optic deflector 14. When a single frequency that changes according to the tracking error information is given, it is possible to easily track a single track formed in an oblique direction on the recording medium 21 during reproduction.

That is, the phase of the sweep signal S _X which is applied to the second acousto-optic deflector 16, and detects a tracking error signal by comparing the phase of the CTL signal 21B which is formed on the recording medium 21, the tracking A signal that controls the scanning beam in the Y-axis direction by an error signal
It is possible to control the scanning locus of the laser beam being scanned in the X-axis direction by controlling the frequency of the S _Y, it is possible to perform a dynamic tracking control.

Note that the deflection beam splitter 19, the optical system 30, and the light detector 31 for detecting the return light are not limited to those in the above-described embodiment. For example, the first and second acousto-optic deflection elements 1
You may make it arrange | position in the middle part of 4,16.

〔The invention's effect〕

As described above, in the optical recording / reproducing apparatus of the present invention, the first acousto-optic deflecting element capable of deflecting in the first direction and the laser beam changed by the first acousto-optic deflecting element are used. Since the second acousto-optic element that deflects in a direction substantially orthogonal to the first direction is provided to scan the semiconductor laser beam in two dimensions, the relative speed between the optical recording medium and the scanning laser beam increases. This makes it possible to record or reproduce a large amount of information on one main track, thereby increasing the recording surface density and improving the data transmission speed.

Further, by applying a tracking control signal to the deflection element forming the sub-scan, the tracking servo of the laser beam can be optically constructed, and the servo mechanism of the recording / reproducing apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the principle of an optical recording / reproducing apparatus according to the present invention, FIG. 2 is an explanatory view for explaining the structure and operation of an acousto-optic deflecting element, and FIG. FIG. 3 is an explanatory diagram of an applied ultrasonic signal and a track formed on a recording surface. In the figure, 10 is a semiconductor laser, 12 is a collimator, 14 is a first acousto-optic deflecting element, 15 is an optical element, 16 is a second acousto-optic deflecting element, and 21 is a recording medium.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-133050 (JP, A) JP 2-576500 (JP, B2) JP 4-51892 (JP, B2) JP-B 2- 53852 (JP, B2) JP 3-5566 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) G11B 7/135

Claims (1)

(57) [Claims] An acousto-optic deflecting element on which a laser beam output from the laser emission source is incident, and a scanning signal which is scanned in a first direction by a sweep signal applied to the acousto-optic deflection element. An optical recording / reproducing apparatus for irradiating the optical recording medium with the laser beam through a beam splitter and an objective lens, wherein the laser beam is applied to the optical recording medium between the laser emission source and the acousto-optic deflecting element. An optical recording / reproducing apparatus, comprising: a sub-scanning acousto-optical element to which a sweep signal for deflecting and scanning in a second direction substantially orthogonal to the first direction is supplied.