KR100301844B1 - micro-mirror device driving electrostatically and optical pick-up system using the same - Google Patents

Abstract

An electrostatically-driven micro-mirror element capable of finely adjusting input light for recording / reproducing optical data storage, and an optical pickup device using the same, comprising: a substrate and a plurality of grooves formed on the substrate; And a fixed electrode portion having a projecting portion that reciprocates up and down the corresponding groove in accordance with an externally applied voltage, and a driving electrode portion positioned above the fixed electrode portion, and a mirror formed on the driving electrode portion. In this case, the driving electrode part includes anchors formed at both edges of the substrate, an elastic suspension fixed to the anchors, a mirror plate supported by the elastic suspension, and one side of the mirror plate. A plurality of electrodes are formed to protrude and correspond to grooves of the fixed electrode part, respectively, and are partially inserted and moved into the grooves according to an externally applied voltage. As described above, the present invention is configured to use an electrostatic driving actuator, thereby improving position control accuracy of input light, lowering power consumption, and integrating and integrating a mirror and a driver, thereby miniaturizing and reducing the size of the optical system.

Description

Electrostatically-driven micro-mirror elements and optical pick-up devices using the same {micro-mirror device driving electrostatically and optical pick-up system using the same}

The present invention relates to an electrostatically-driven micro-mirror element capable of finely adjusting input light for recording / reproducing optical data storage and an optical pickup device using the same.

Recently, the development of computer and communication technology, an information related technology, has been made possible through the development of an information storage device capable of storing, recording and reproducing a large amount of information.

Moreover, the proliferation of multimedia environments that require the processing of various types of data in real-time requires further improvements in capacity and processing speed of existing information storage devices.

In the case of the conventional magnetic storage method, it is known that it is very difficult to realize more than 10 gigabytes per square inch due to the physical limitation of the recording density.

On the other hand, the information storage device using the optical system has advantages such as optical response speed, non-contact pickup and easy portability, and above all, the data density can be increased to the wavelength range of the laser light source for recording / reproducing. There is this.

However, higher data density means that the track pitch, which is the interval between data bits or the interval between data tracks, should be reduced by the wavelength range of the light source for recording / reproducing.

Therefore, an optical system capable of adjusting the position of the laser beam to accurately irradiate the recording / reproducing laser beam to the position of the track pitch becomes a key to the high density optical information storage device.

On the other hand, the emergence of an ultra-fine optical system using micromachining technology is expected to be a technology capable of realizing the displacement control of the ultra-precision laser beam mentioned above.

In addition, not only the area of the optical information storage device, but also an example of the DMD (Digital Mirror Dispaly) of Texas Instrument, a new concept image display, applies a micro-mirror array, which is a micro optical device. One example.

And, a study on a laser beam scanner for a bar code reader using polycrystalline silicon surface micromachining (J. Microelectromech. Syst. Vol. 7, no. 1, pp. 27-37 , 1998) is also reported that the application field of the ultra-fine optical system implemented by micromachining is expanding.

However, the microscopic optical system of the prior art enumerated above is a method of adjusting the position of the input light by changing the reflection angle of the mirror by driving the mirror non-parallel as shown in FIG.

In this case, the angle change of the mirror due to the driving and the position of the laser beam have a nonlinear relationship, and the driving precision also has the disadvantage of being inversely proportional to the distance between the mirror and the optical disk.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatically driven micro-mirror element and an optical pickup apparatus using the same that can improve the position control accuracy of input light and reduce power consumption by using an electrostatically driven actuator.

Another object of the present invention is to provide an electrostatically-driven micro-mirror element and an optical pickup apparatus using the same that can reduce and reduce the size of an optical system by integrating and integrating a mirror and a driver.

1 shows reflection of a laser beam by an electrostatically driven micro-mirror element according to the invention.

2 shows an optical pickup apparatus using an electrostatically driven micro-mirror element according to the present invention.

3 is a view showing the optical axis change of the recording / reproduction laser beam by the electrostatically driven micro-mirror element according to the present invention;

4 and 5 is a view comparing the principle of the position control of the laser beam by the driving of the electrostatically-driven micro-mirror device according to the prior art and the present invention

6A is a perspective view showing an electrostatic parallel drive micro-mirror element having a comb-shaped electrode according to the present invention.

6B is a perspective view showing an electrostatic parallel drive micro-mirror element having a coaxial rod-like electrode according to the present invention.

Figures 7a and 7b show the principle of parallel drive of the micro-mirror device of the present invention by the electrostatic method

Explanation of symbols for main parts of the drawings

1 substrate 2 insulation layer

11 light source 12 collimating lens

13: light splitter 14,16,18: focusing lens

15: 45 ° submount 17: disc

19: light sensing element 30: micro-mirror element

31: mirror plate 32, 33: upper electrode

34,35: lower electrode 36: lower common electrode

37: support spring 38: fixed part

71 disc substrate 72 recording layer

73,74 bits

The electrostatically-driven micro-mirror device according to the present invention has a fixed electrode portion having a substrate, a fixed electrode portion formed on the substrate and having a plurality of grooves, and a protrusion for vertically reciprocating the inside of the groove corresponding to the externally applied voltage. It consists of a drive electrode part located in the upper part, and the mirror formed on a drive electrode part.

Here, the grooves of the fixed electrode portion may be in the form of a stripe arranged in one direction or in the form of dots arranged at regular intervals, and the protrusions of the driving electrode portion correspond to the grooves of the fixed electrode portion, and portions are inserted therein.

The driving electrode unit may include anchors formed at both edges of the substrate, an elastic suspension fixed to the anchors, a mirror plate supported by the elastic suspension, and one side of the mirror plate. A plurality of electrodes are formed to protrude and correspond to grooves of the fixed electrode part, respectively, and are partially inserted and moved into the grooves according to an externally applied voltage.

In this case, the elastic suspension may be formed at a predetermined distance from the surface of the substrate, and the electrodes inserted into the grooves are spaced apart from the inner surface of the grooves.

In addition, the electrodes may have a stripe shape arranged in one direction or a dot shape arranged at regular intervals, and the cross section of the electrode and the groove may be formed in any one of a polygon, a circle, and an oval.

The optical pickup device using the electrostatically-driven micro-mirror element configured as described above includes a light source module for generating light, a focusing unit for focusing light generated from the light source module on the surface of the optical recording medium, and reflection by the optical recording medium. A light detecting unit for converting the converted light into an electrical signal, and located between the light source module and the focusing unit to transmit the light generated from the light source module to the focusing unit, and to be reflected by the optical recording medium to transmit the light passing through the focusing unit to the light detecting unit. And a micro-mirror element positioned between the optical separation unit and the focusing unit and the optical separation unit to reflect incident light and finely adjust a path of the reflected light.

Here, the electrostatically driven micro-mirror element is located on the 45 degree inclined surface of the submount.

As described above, the present invention configured can fine-tune data tracking by adjusting the position of the input light irradiated to the optical information medium for recording and reproduction with an electrostatic parallel drive micro-mirror element.

In addition, since the present invention uses an electrostatic driving actuator, the position adjustment accuracy of the input light can be improved, power consumption can be reduced, and the size of the optical system can be reduced in size and weight by integrating and integrating the mirror and the driver.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Referring to the accompanying drawings, preferred embodiments of the present invention having the features as described above are as follows.

1 is a view showing reflection of a laser beam by an electrostatically-driven micro-mirror device according to the present invention. As shown in FIG. 1, the micro-mirror device 30 may be formed by a semiconductor integrated process and micromachining techniques. It is fabricated and has a degree of freedom in the axial direction in a direction perpendicular to the substrate.

This micro-driven micro-mirror element 30 is coupled on a 45 ° submount 15 to redirect the input laser beam so that it can be irradiated onto the information storage optical disk surface.

The micro-mirror element 30 coupled to the 45 ° submount 15 finely drives the micromirror to finely position the laser beam emitted from the fixed input light source to irradiate the data position on the magneto-optical disk. Be sure to

Such a parallel drive type micro-mirror element maintains the positioning accuracy of the laser beam irrespective of the distance between the mirror and the optical disk, and changes the position of the laser beam in direct proportion to the displacement of the driven mirror. Control characteristics can be obtained to stably control the position of the laser beam.

In addition, the electrostatically-driven micro-mirror device of the present invention is manufactured in a very small size using micromachining technology, so that it is possible to realize miniaturization and light weight of the optical pickup device, and to improve driving resolution to a nanometer level. Will have

In addition, since the electrostatically driven micro-mirror device of the present invention is driven by an electrostatic driving method driven by an electric field by an applied voltage, there is an advantage in that it can be driven at low power because there is no consumption of current.

The present invention driven as described above can increase the spatial resolution of the beam position adjustment as compared to the tilting mirror used in the DMD or the beam scanner, and due to the improvement of the resolution, It can be utilized for pickup of optical information storage media.

An optical pickup apparatus employing the electrostatically-driven micro-mirror element of the present invention having such an advantage is as follows.

FIG. 2 is a view showing an optical pickup apparatus using an electrostatically-driven micro-mirror element according to the present invention, and as shown in FIG. 2, a spread angle output from an input light source 11 for recording / reproducing an optical signal ( The laser beam having a spreading angle is converted into parallel light through a collimating lens 12 or the like, and then passes through a beam splitter 13 and is focused on a 45 ° sub-mount 15 by the focusing lens 14. Focused on an electrostatic parallel drive micro-mirror element (30) coupled thereto.

Then, the laser beam is reflected by this mirror so that the optical path is changed to be perpendicular to the surface of the magneto-optical disk 17.

At this time, the optical system reaching the micro-mirror element 30 is assembled to a slider for the optical pickup, the optical path is through the free space on the slider, or optical fiber, optical waveguide It can also be configured by way of a wave guide or the like.

Subsequently, the laser beam reflected by the micro-mirror element 30 is focused onto the recording layer of the magneto-optical disk through another focusing lens 16 or the like, and fine actuation of the micro-mirror element 30 is performed. ) The laser beam moves to the position to be recorded / played back by the displacement.

On the other hand, for the reproduction of information, the input laser beam reflected at the data bit position of the magneto-optical disk to be reproduced travels the optical path so that the focusing lens 16, the micro-mirror element 30, the focusing lens 14, and the optical splitter ( 13) and the like, through another focusing lens 18, it is focused on the optical sensing element 19 using a photodiode or the like and can read 1-bit data recorded on the disk.

In the case of recording information, the temperature of the data bit position to be recorded is locally raised by adjusting the time of incidence of a laser having a higher power than the above-described reproducing laser or by adjusting the time that the recording / reproducing laser beam stays at a specific position. Digital information by changing the optical properties of the recording material on the disc by applying a phase change and a magnetic field focused on a magnetic field generating device mounted on the magneto-optical pickup head to a specific data location. Both magnetic and optical methods for recording are possible.

Here, the optical information recording / reproducing method by the electrostatically-driven micro-mirror element of the present invention will be described in more detail as follows.

3 is a view showing a change in the optical axis of the recording / reproducing laser beam by the electrostatically-driven micro-mirror device according to the present invention, as shown in Figure 3 the input laser beam is a parallel drive of the micro-mirror device 30 The position at which the high density magneto-optical disk 17 is incident by the displacement h is finely adjusted by d.

As such, when the micro-mirror element 30 finely adjusts the input laser beam to record the information bits 73 and 74 in the recording layer 72 of the magneto-optical disk 17 at high density, each information bit 73, 74, the optical properties such as reflectivity, phase difference, refractive index and so on with respect to the input laser beam.

Therefore, in order to reproduce the recorded information bits, the micro-mirror element 30 is driven in parallel to move the laser beam to the information bit position to be reproduced, and to the bit 73 having the optical property defined as 1 and to 0. The recorded information can be reproduced by sensing the laser beams reflected from the bits 74 having defined optical properties.

4 is a view showing a principle of position control of a laser beam by driving an electrostatically driven micro-mirror device according to the present invention. As shown in FIG. , Adjust the position of the laser beam.

This electrostatic drive method will be described later.

Here, when the driving distance of the parallel driving micro-mirror element is h, the position of the laser beam reflected by the micromirror plate 31 mounted on the sub-mount 15 making 45 ° with the input laser beam is d. Will change as much.

At this time, the relationship between d and h is shown in Equation 1 below.

Therefore, the displacement of the mirror plate is finely adjusted by the parallel driving of the micro-mirror elements, thereby making it possible to adjust the position of the input laser beam.

This parallel drive micro-mirror element has an arrangement of upper electrodes 32 and 33 coupled to the mirror plate 31 and lower electrodes 34 and 35 formed on the substrate 1 of the element, as shown in FIG. When a control voltage is applied between the arrays to generate an electrostatic force, the mirror plates 31 connected to the anchors 38 through the support springs 37 are connected to the lower electrodes 34 and 35. And the displacement h of the mirror plate 31 is determined at a position at which the electrostatic force corresponding to the applied voltage is equal to the restoring force of the support spring 37.

Here, the upper electrodes 32 and 33 may be comb-shaped electrodes or coaxial rod-shaped electrodes, and the lower electrodes 34 and 35 may be comb-shaped electrodes or coaxial shields ( shield) electrode.

In addition, the support spring 37 is formed at a predetermined distance from the surface of the substrate 1 for the elastic force, and between the substrate 1 made of silicon or the like and the upper / lower electrodes 32, 33, 34, 35 for driving. It is preferable to form the insulating layer 2 for insulation.

Conventional laser beam positioning device, as shown in Figure 5, unlike the parallel drive micro-mirror device of the present invention uses a tilting method in which the mirror rotates slightly.

However, in this case, since the displacement of the reflected laser beam is compounded by the rotation angle θ of the mirror and the parallel displacement of the mirror, it is difficult to control the linear position, and the laser beam displacement varies depending on the distance from the mirror to the magneto-optical disk. This makes it difficult to control the laser beam position.

Referring to the structure of the electrostatic-driven micro-mirror device of the present invention in more detail as follows.

FIG. 6A is an electrostatic parallel drive micro-mirror element with comb-shaped electrodes, and FIG. 6B is an electrostatic parallel drive micro-mirror element with coaxial rod-shaped electrodes.

Here, although the parallel displacement mirror of the simple plate capacitor structure is not shown, the structure is also included in the scope of the present invention.

FIG. 6A is a parallel drive micro-mirror whose drive unit is a comb electrode formed in a direction perpendicular to the substrate 1.

As shown in FIG. 6A, the upper comb electrode 32 is arranged on the mirror plate 31 to which the mirror is attached, and the lower comb electrode 34 has a gap between the upper comb electrode 32 and a predetermined free space. ) Is arranged, and a common lower electrode 36 is formed below the lower comb electrode 34 to electrically connect the lower comb electrode 34.

Here, the lower comb electrode 34 is electrically separated from the substrate 1 by the insulating layer 2, and the support spring 37 and the support spring 37 supporting the mirror plate 31 described above. The fixing part 38 for fixing the is omitted.

FIG. 6B is a parallel drive micro-mirror element whose drive unit is a coaxial rod-shaped electrode formed in a direction perpendicular to the substrate 1 unlike FIG. 6A.

The driving unit has an advantage of lowering driving power as compared to the driving unit using the comb electrode.

As shown in FIG. 6B, in the micro-mirror element using the coaxial rod electrode, the mirror plate 31 having a mirror is connected to the upper coaxial rod electrode 33, similarly to the micro-mirror element using the comb electrode. The coaxial rod electrode 33 is displaced by a potential difference with the lower coaxial shield electrode 35 fixed to the substrate 1.

Here, the upper coaxial bar electrode 33 and the lower coaxial shield electrode 35 are separated by a gap in the free space, and the lower shield electrode 35 is electrically connected to the common electrode 36.

In addition, the substrate 1 and the lower coaxial shield electrode 35 are separated by the insulating layer 2 so as to prevent leakage current, noise, mixing, cross-talk, and the like.

6B, the support spring 37 for supporting the mirror plate 31 and the fixing portion 38 for fixing the support spring 37 are omitted.

6A and 6B are only an example, and in some cases, the shape of the mirror element such as the number and shape of the upper electrodes, the shape of the support spring, the clearance of the free space, etc. may vary depending on the driving distance and the input voltage. It can be designed in various ways.

That is, the shape of the groove of the lower electrode corresponding to the upper electrode may be in the form of a stripe arranged in one direction or in the form of a dot arranged at regular intervals. It may be formed in various shapes such as elliptical.

In addition, in the design of the present invention, it should be noted that the protrusions of the upper electrode correspond to each of the grooves of the lower electrode so that a part thereof is inserted.

That is, when the upper and lower electrodes are in the form of a comb, portions of the upper and lower electrodes are formed to overlap each other, and in the case of the coaxial rod, the protrusions of the upper electrode are formed so that the portions of the upper and lower electrodes overlap in the grooves of the lower electrode.

The driving principle of the electrostatic drive type micro-mirror device of the present invention having such a structure is as follows.

7A and 7B are diagrams showing the principle of parallel driving of the micro-mirror device of the present invention by the electrostatic method.

FIG. 7A illustrates a standby state in which no voltage is applied between the driving upper electrodes 32 and 33 and the fixing lower electrodes 34 and 35.

Here, the driving upper electrodes 32 and 33 and the fixing lower electrodes 34 and 35 overlap by l .

Subsequently, when the driving voltage V ₂ is applied to the upper and lower electrodes as shown in FIG. 7B, the free space gaps a and c between the driving upper electrodes 32 and 33 and the fixing lower electrodes 34 and 35 are performed. , An electric field is formed in Ww, and an electrostatic force is generated in proportion to the electric field formed.

By this electrostatic force, the upper electrodes 32, 33 are attracted to the lower electrodes 34, 35 by h.

At this time, the mirror plates attached to the upper electrodes 32 and 33 are also moved by the same distance, and the moving distance h is a position where the restoring force proportional to the electrostatic force by the applied voltage and the spring constant k of the support spring 37 is balanced. Is determined.

That is, referring to the relation shown in FIG. 7B, the displacement of the micro-mirror device according to the driving voltage may be obtained.

In particular, the electrode arrangement of the comb structure or the coaxial rod structure has a more linear change in capacitance C due to displacement, thereby enabling linear parallel driving of the mirror.

Also, the linearity of the drive is shown in FIGS. 7A and 7B. The smaller the gap value of the side wall surface is given by the smaller the a and c values of the gap between the upper and lower electrodes parallel to the substrate direction.

In the electrostatically driven micro-mirror element and the optical pickup device using the same according to the present invention, the following effects are obtained.

First, by integrating / integrating the micro-optic component mirror and the light beam position controller, the size of the optical system can be miniaturized / lightened, and the linear position of the light beam can be adjusted by driving the mirror in a direction perpendicular to the substrate. do.

Second, the position control of the light beam can be controlled to the nanometer level by using the parallel driving micro-mirror element, and the power consumption can be lowered by integrating and using the electrostatic driver.

Third, the electrostatic drive type driver having a linear driving characteristic in a direction perpendicular to the substrate not only makes it possible to realize a pickup device of a high density optical information storage device, but also can be applied as a fine beam position adjusting device such as a high precision optical scanner. Can be.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (11)

Board; A fixed electrode part formed on the substrate and having a plurality of grooves; A driving electrode part having a protrusion which reciprocates up and down the corresponding groove in accordance with an externally applied voltage, and is located above the fixed electrode part; And, The electrostatically-driven micro-mirror device, characterized in that composed of a mirror formed on the drive electrode. The electrostatically-driven micro-mirror device according to claim 1, wherein the groove of the fixed electrode part is in the form of a strip arranged in one direction or a dot arranged at a predetermined interval. The electrostatically-driven micro-mirror device according to claim 1, wherein the protrusions of the driving electrode parts are respectively inserted into corresponding grooves of the fixed electrode parts. The method of claim 1, wherein the driving electrode portion Anchors respectively formed at both edges of the substrate; An elastic suspension fixed to the anchors; A mirror plate supported by the elastic suspension; And, It is formed to protrude on one side of the mirror plate, a portion corresponding to each of the grooves of the fixed electrode portion is inserted, characterized in that it further comprises a plurality of electrodes to be moved into the groove according to the external applied voltage Electrostatically driven micro-mirror elements. The electrostatically-driven micro-mirror device according to claim 4, wherein the elastic suspension is formed at a predetermined distance from the surface of the substrate. The electrostatically-driven micro-mirror device according to claim 4, wherein the electrodes inserted in the grooves are spaced apart from the inner surface of the grooves. The electrostatically-driven micro-mirror device according to claim 4, wherein the electrodes have a stripe shape arranged in one direction or a dot shape arranged at regular intervals. The electrostatically-driven micro-mirror device according to claim 4, wherein the cross section of the electrode and the groove is formed in any one of a polygon, a circle, and an oval. The electrostatically driven micro-mirror device according to claim 1, wherein an insulating film is formed on the surface of the substrate. Electrostatic driving micro-mirror consisting of a fixed electrode having a plurality of grooves, a driving electrode having a projection for reciprocating up and down the corresponding grooves in accordance with the external applied voltage, and a mirror formed on the driving electrode In the optical pickup device using the element, A light source module for generating light; A focusing unit focusing the light generated from the light source module on the surface of the optical recording medium; A photodetector for converting light reflected by the optical recording medium into an electrical signal; An optical separation unit positioned between the light source module and the focusing unit to transmit light generated from the light source module to the focusing unit, and to be reflected by the optical recording medium and to transmit light passing through the focusing unit to the light detecting unit; An optical pickup apparatus using an electrostatically-driven micro-mirror element, wherein the micro-mirror element is disposed between the focusing unit and the light splitting unit to reflect incident light and finely adjust the path of the reflected light. . 11. The optical pickup apparatus of claim 10, wherein the micro-mirror element is located on a 45 degree inclined surface of the submount.