CN1328324A - Acoustooptical Bragg diffraction type multi-beam optical R/W head - Google Patents

Abstract

An acoustooptical bragg diffraction type multi-beam optical R/W head features that an ccoustooptical Bragg diffraction element is arranged between the collimator and splitter of traditional optical R/W head and a control unit is used to provide electric signal to trigger acoustooptical action. As a result, a laser device with single light source can genrate multiple light beams, which are focused by an object lens to form multiple R/W light spots, so increasing the data access speed.

Description

Acoustooptical Bragg diffraction type multi-beam optical R/W head

The present invention relates to a kind of Acoustooptical Bragg diffraction type multi-beam optical R/W head, and be particularly related to a kind of read-write head device that can produce a plurality of read-write luminous points simultaneously.

The developing direction of optical record medium wishes can store more highdensity data information in identical disc size at present, to store the demand of coal body in response to high capacity on the market.And know mostly only to design in the optical read/write head single light beam (Single Beam) is arranged in order to reading/writing document, need look the rotating speed of CD-ROM device and its restriction is arranged though the speed of its read-write becomes, make that the speed of read-write defective material can't be in response to demand in the market, hereat using multiple beam (Multi-beam) data that reads while write has been optical read/write head development in future trend.

At present known read/write head produces the method for multiple beam and mainly divides into two kinds:

1. utilize laser two volume arrays, directly produce a plurality of read-write light beams, be difficult for but the cost of the method is higher and optics is corresponding.

2. utilize the technology of phase grating (Phase Grating) diffraction beam split, produce 0 rank, ± 1, ± 2 rank, ± 3 rank ... Deng diffracted beam, and focus on as the required many luminous points of read-write; But the brightness of luminous point that these light beams produce, can descend fast with the work exponent number, the program that needs to increase by a signal Processing is in addition adjusted, its spendable number of spots but, still can be restricted, moreover each position system that reads and writes luminous point is decided by the expired of grating, must remember that the track of green medium cooperates by opinion optics, the aligning opinion of optics is proofreaied and correct and is become more difficult.

In addition, in No. 4459690 patent of the U.S., disclosed the device that a kind of employing acousto-optic element (Acoustic-Optic Device) produces multiple beam, but the complex structure of its optical system, optical interface are many, light is superimposed easily and produce noise, therefore it is by light beam that acousto-optic element produced, tightly can be used for the tracking that optics is remembered green mediator track, and not be suitable for the read-write of data.

In view of this, purpose of the present invention is a kind of read/write head that produces a plurality of read-write luminous points of design, and the opinion brightness of the number of its luminous point, position all can accurately be controlled.

Another object of the present invention makes optical read/write head can produce a plurality of read-write luminous points for a kind of simple structure of design and the low structure of cost.

Purpose according to the invention described above, a kind of Acoustooptical Bragg diffraction type multi-beam optical R/W head is provided, the laser beam that laser diode is launched, elder generation handles via a collimating apparatus and light beam is become the bigger directional light of scope, then through an acousto-optic Bradley diffraction element, the electric signal that comprises at least one radiofrequency signal (Radio Frequency) is provided by a control module, and excite the acousto-optic interaction of acousto-optic Bragg diffraction element, and then to produce several light beam and assemble via object lens be several read-write luminous points.

Because the present invention can discuss the size of power via the number of control radio frequency signal frequency, the height of frequency, decide number, position and the brightness of read-write luminous point, therefore brightness is even between luminous point, and can significantly increase the number of luminous point and make data access speed more quick.

For allowing above-mentioned and other purposes of the present invention, feature and the advantage can be clearer and more definite understandable, following historical relic be lifted a preferred embodiment, and conjunction with figs., is described in detail below.

Fig. 1 has shown the effect synoptic diagram of Bragg diffraction element among the present invention;

Fig. 2 shows the structural representation of specific embodiments of the invention.

The disclosed technology according to the present invention is in the optical system of known optical read/write head, utilizes the Bragg diffraction phenomenon and reaches the purpose that produces a plurality of read-write luminous points.Bragg diffraction is basically but for a kind of diffraction phenomena that utilizes periodic structure to produce, please refer to Fig. 1, and Bragg diffraction element 30 of the present invention, produce the diffraction element of several luminous points for a kind of interaction that utilizes the sound wave light wave, its operation principles is: utilize a control module 40 to provide Bragg diffraction element 30 required electric signal, therefore and excite sound waves allow Bragg diffraction element 30, because sound wave is a kind of dilatational wave, therefore can make medium form a plurality of one and dredge a close state, as the periodicity diffraction element that offers several cracks, therefore can make the light wave that passes through produce required diffraction phenomena.

Because acousto-optic Bragg diffraction phenomenon is followed following formula: $2{\mathrm{\θ}}_{\mathrm{Bi}}=\frac{\mathrm{\λ}}{\mathrm{nv}}{f}_i,i=\mathrm{1,2,3},\·\·\·$

Wherein, θ _BiBe Prague deflection angle

λ is an optical wavelength

ν is a wave length of sound

N is a medium refraction index

Fi be electric wave with frequency, that is radio frequency signal frequency (Radio Frequency)

So by learning in the formula: under the situation that light wave opinion wave length of sound is fixed, in same medium, be added on the number and height of the radio frequency signal frequency (fi) of Bragg diffraction element 30, can determine Prague angle of deviation (θ _Bi) quantity and size.Please referring again to Fig. 1, that is to say the laser beam that is sent when laser disome 10, after a collimating mirror 20 arrives the Bragg diffraction element,, then have two road light and behind diffraction, depart from 2 θ respectively according to formula if control module 40 provides the electric signal that contains the number of reading of two kinds of frequency radio frequencies _BiOpinion 2 θ _BiAngle, add the light beam that keeps original light path, then after object lens 60 are assembled, can on optics is remembered the surface of green medium 70, form three read-write luminous points, be respectively the 0th read-write luminous point 71, the first read-write luminous point 72 and the second read-write luminous point 73.

Adding the present invention more can be by the power of control radiofrequency signal, and adjust the brightness of various read-write luminous points, make it even, when therefore the present invention increases luminous point quantity, do not have in the method for known use phase type grating the anxious problem of point brilliance to descending, therefore the number of read-write luminous point can also increase significantly, thereby improve Information Access speed significantly, and aspect optical alignment, also can make light spot position control easily by adjusting Prague deflection angle; Wherein be noted that: the frequency that the present invention needs radiofrequency signal approximately between tens of MHz between hundreds of MHz, with the carrying out of auxiliary Bragg diffraction phenomenon.

Please refer to Fig. 2, structural representation for the specific embodiment of the invention, propose in the most preferred embodiment in the present invention, Bragg diffraction element 30 is disposed on the light path between collimating mirror 20 and the spectroscope 50, because after laser beam penetrates in by laser diode 10, need through a collimating apparatus 20 laser beam is treated to the bigger parallel beam of scope earlier, when making light beam through coin glug diffraction element 30, the interaction range of sound wave and light wave is bigger, and obtains diffraction efficiency preferably; And the bragg element 30 that is adopted among the present invention can be uniform dielectric acousto-optic Prague any one in element (Isotropic Acoustic-optic Bragg Diffraction Cell), birefringence acousto-optic Bragg diffraction element (Bi-refrangent Acoustic-optic Bragg DiffractionCell) or the acousto-optic Bragg diffraction element of surface wave (Surface Wave Acoustic-opticBragg Diffraction Cell).

After parallel beam is through Bragg diffraction element 30, can form several incident beam, as previously mentioned, its quantity is decided on the number of the radio frequency signal frequency that control module 40 is provided, incident light by two road different light paths shown in Fig. 2 it seems that control module only provides a kind of radiofrequency signal of frequency this moment as can be known; Can remember the light beam that green medium 70 reflect in order to separate earlier through a spectroscope 50 after aforementioned several incident beam, assemble through object lens 60 again, and remember generation the 0th read-write luminous point 71 and the first read-write luminous point 72 on the green medium 70 at optics from optics.

Simultaneously, the folded light beam of this two read-writes luminous point 71,72, same through object lens 60, spectroscope 50, and be gathered on the detector 90 by a cylindrical mirror 80, being converted to electric signal from the reflected light signal of this two read-writes luminous point 71,72, and this detector 90 can be a kind of linear detector (Linear Detector), and its type can cooperate the folded light beam of aforesaid read-write luminous point with position system.

The present invention ties up between the collimating apparatus and spectroscope in the traditional optical read/write head, more increase by an acousto-optic Bragg diffraction element, make single laser beam produce several different incident beams because of diffraction phenomena, because the present invention can be by the size of height with the power of the number of the radio frequency signal frequency (RadioFrequency) of control in the electric signal, frequency, decide number, position and the brightness of several read-write luminous points, therefore brightness is even between luminous point, and can significantly increase the number of luminous point and make data access speed more quick.

Though the present invention discloses as above with a preferred embodiment, right its is not in order to qualification the present invention, any those skilled in the art, under the premise without departing from the spirit and scope of the present invention, can do a little change and retouching, therefore assurance scope of the present invention is determined by appended claims.

Claims (12)

1, a kind of Acoustooptical Bragg diffraction type multi-beam optical R/W head is used for remembering that at optics green media surface produces a plurality of read-write luminous points, comprising:

One laser diode is remembered the laser beam that green medium are required in order to produce access optics;

One collimating mirror is in order to be treated to a parallel beam with this laser beam;

One Bragg diffraction element is in order to be divided into several incident beam with this parallel beam;

One control module, it provides an electric signal and makes and this Bragg diffraction element excite sound waves makes this parallel beam be divided into this several incident beam by acousto-optic interaction;

One object lens, in order to described several light beam Jiao in the surface of this optical record medium, and form several the read-write luminous point;

And a detecting device, in order to being converted to electric signal from several folded light beam of this several read-write luminous point.

2, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein further bag is inserted with an optical splitter, is positioned on the light path between this Bragg diffraction element and this object lens, is used for this several folded light beam of several incident beam and this is separated.

3, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 2 wherein further includes a cylindrical mirror, is positioned on the light path between this spectroscope and this detector, is used for this several reflected light is gathered in this detector.

4, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein this Bragg diffraction element acousto-optic Bragg diffraction element (IsotropicAcoustic-optic Bragg Diffraction Cell) that is uniform dielectric.

5, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein this Bragg diffraction element is birefringence acousto-optic Bragg diffraction element (Bi-refrangentAcoustic-optic Bragg Diffraction Cell).

6, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein this Bragg diffraction element is surface wave acousto-optic Bragg diffraction element (Surface WaveAcoustic-optic Bragg Diffraction Cell).

7, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein the electric signal that this control module produced comprises the radiofrequency signal (RadioFrequency) of at least one frequency.

8, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 7, wherein the number of this radio frequency signal frequency is used to determine the number of this read-write luminous point.

9, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 7, wherein the height of this radio frequency signal frequency can determine the position of the read-write luminous point of its correspondence.

10, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 7, wherein the watt level of this radiofrequency signal can determine the brightness of these a plurality of read-write luminous points.

11, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 7, wherein this frequency of penetrating radiofrequency signal between tens of MHz between hundreds of MHz.

12, Acoustooptical Bragg diffraction type multi-beam optical R/W head as claimed in claim 1, wherein this detector is a kind of linear detector (Linear Detector).

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