OPTICAL SCANNER HAVING MIRROR SELF-ANGLE ADJUSTMENT FUNCTION, AND MIRROR ANGLE ADJUSTMENT METHOD THEREOF

This application relates to an optical scanner having a mirror self-angle adjustment function, and a mirror angle adjustment method thereof. In one aspect, the optical scanner includes a mirror that reflects light and an electrostatic driver that pivots the mirror. The electrostatic driver includes a fixed electrode part having a plurality of driving electrodes, which are connected to the mirror and arranged in rows, and a plurality of fixed electrodes arranged in rows alternately with the plurality of driving electrodes and pivoting the mirror via an applied driving voltage. The plurality of fixed electrodes include a plurality of main electrodes to which the driving voltage is applied, and a plurality of additional electrodes. The plurality of additional electrodes are electrically isolated from the plurality of main electrodes, and the driving voltage is selectively applied to the plurality of additional electrodes.

BACKGROUND

Technical Field

The present disclosure relates to an optical scanner. More particularly, the present disclosure relates to an optical scanner having a self-angle adjustment function of a mirror manufactured through a micro electro mechanical systems (MEMS) process and to a method for adjusting a mirror angle.

Description of Related Technology

Recently, in various technical fields such as display, printing apparatus, precision measurement, and precision processing, research on micro electro mechanical systems (MEMS) devices manufactured by semiconductor process technology has been actively carried out. Particularly, in the display field in which an image is realized by scanning light emitted from a light source into a screen area, or in the scanning field in which image information is read by scanning light to a screen area and receiving reflected light, a micro-structured optical scanner is attracting attention. That is, because the optical scanner can modulate reflected light and has fast, accurate operation and response speed, and low power consumption, it can be applied to optical communication devices such as a variable optical attenuator (VOA), a 1×N switch, a wavelength selective switch (WSS), a tunable laser, and the like. In addition, the optical scanner can be applied to various fields such as optical coherence tomography (OCT), pico projector, smart headlight, LiDAR, skin care machine, and the like.

SUMMARY

Accordingly, it is an object of the present disclosure to provide an optical scanner, and a mirror angle adjustment method thereof, having a mirror self-angle adjustment function capable of compensating and adjusting attenuation characteristics without adding an external controller.

Another object of the present disclosure is to provide an optical scanner, and a mirror angle adjustment method thereof, having a mirror self-angle adjustment function capable of improving a manufacturing yield by performing the mirror self-angle adjustment in a module alignment step.

In order to solve the above problems, the present disclosure provides an optical scanner comprising a mirror reflecting light, and an electrostatic actuator pivoting the mirror by an applied driving voltage.

The electrostatic actuator includes a plurality of driving electrodes connected to the mirror and arranged in rows, and a fixed electrode unit including a plurality of fixed electrodes arranged in alternating rows with the plurality of driving electrodes and pivoting the mirror by an applied driving voltage.

The plurality of fixed electrodes include a plurality of main electrodes to which the driving voltage is applied, and a plurality of additional electrodes electrically isolated from the plurality of main electrodes, wherein the driving voltage is selectively applied to the plurality of additional electrodes.

Among the plurality of additional electrodes, the number of the additional electrodes to which the driving voltage is applied is proportional to an angular size of the mirror to be adjusted.

In the plurality of fixed electrodes, the plurality of main electrodes may be centrally arranged, and the plurality of additional electrodes may be arranged on both sides of the plurality of main electrodes.

The fixed electrode unit includes a main electrode part including the plurality of main electrodes and a main electrode plate to which the plurality of main electrodes are connected and supported, and an additional electrode part disposed adjacent to the main electrode part, electrically isolated from the main electrode part, and including the plurality of additional electrodes and a plurality of additional electrode plates connected to the plurality of additional electrodes.

The plurality of additional electrodes arranged on each of both sides of the plurality of main electrodes are connected to at least one additional electrode plate.

The optical scanner according to the present disclosure further comprises a power terminal for applying the driving voltage to the main electrode plate and the plurality of additional electrode plates; a main bonding wire electrically connecting the main electrode plate and the power terminal; and an additional bonding wire electrically connecting the power terminal and an additional electrode plate, among the plurality of additional electrode plates, connected to an additional electrode to which the driving voltage is to be applied.

The optical scanner according to the present disclosure may further comprise a bonding wire electrically connecting the main electrode plate and an additional electrode plate, among the plurality of additional electrode plates, connected to an additional electrode to which the driving voltage is to be applied.

The optical scanner according to the present disclosure may further comprise a tilt unit applying a physical force to the fixed electrode unit to shift the plurality of driving electrodes and the plurality of fixed electrodes from each other.

The optical scanner according to the present disclosure may be a variable optical attenuator (VOA) or a switch.

In addition, the present disclosure provides a method for adjusting an angle of a mirror of the optical scanner, the method comprising measuring an angle of light reflected depending on rotation of the mirror by applying a driving voltage only to the plurality of main electrodes; determining the number of additional electrodes to be connected, based on the measured angle of light and a predetermined amount of attenuation; and electrically connecting the determined number of additional electrodes to a power terminal for applying a driving voltage to the plurality of main electrodes by wire bonding.

The optical scanner according to the present disclosure includes the main electrodes and the additional electrodes in the fixed electrode unit, and the attenuation characteristics can be compensated and adjusted without adding an external controller by adjusting the number of the additional electrodes to which the driving voltage will be applied. That is, the angle of light reflected depending on the rotation of the mirror is measured by applying the driving voltage to the main electrodes. Based on the measured angle of light and a predetermined amount of attenuation, the number of additional electrodes to be connected is determined. In order to apply power to the determined number of additional electrodes, the power terminal is electrically connected to the determined number of additional electrodes via wire bonding. Therefore, it is possible to adjust the angle of the mirror in consideration of the attenuation characteristics of the optical scanner under the same driving voltage.

As such, performing the self-angle adjustment of the mirror in the module alignment step can optimize the performance of the module by minimizing the angular deviation of the mirrors when manufacturing the module including the plurality of optical scanners according to the present disclosure, and can also improve the manufacturing yield of the optical scanner.

DETAILED DESCRIPTION

Generally, the optical scanner refers to a structure in which a mirror for reflecting light and an electrostatic actuator for pivoting the mirror are formed in a single chip by using MEMS process technology.

The electrostatic actuator has a structure in which driving electrodes are formed in a direction parallel to a plane of a moving stage or moving structure, and fixed electrodes corresponding to the driving electrodes are disposed at fixed positions alternately with the driving electrodes and formed, like the driving electrodes, parallel to the plane direction of the stage. The electrostatic actuator has a difference in height or inclination between the driving electrode and the fixed electrode in order to rotate by electrostatic force.

In the optical scanner, the number of driving electrodes and fixed electrodes is determined in consideration of an applied voltage depending on driving conditions of the optical scanner in the MEMS design and manufacturing step.

The optical scanner may need to fine-tune a mirror angle depending on usage environments. For example, the VOA is a case of compensating and adjusting the attenuation characteristics. That is, the VOA is an important component used to control the output of an optical signal in a wavelength division multiplexing (WDM) optical transmission system composed of an optical amplifier, an optical add/drop multiplexer (OADM), and the like. The VOA using the optical scanner provides fast response time and high performance, and has many advantages in terms of product yield and price as it can be mass-produced.

However, the VOA using the optical scanner has difficulty in ensuring a desired amount of attenuation after final assembly due to a MEMS process error and an assembly error with a collimator. That is, because the number of driving electrodes and fixed electrodes is determined in the manufacturing step of the optical scanner, it is impossible to fine-tune the mirror angle in the manufactured optical scanner.

In order to solve this problem, research on a method for reducing the above-mentioned errors in the assembly step is being conducted. For example, U.S. patent Ser. No. 07/450,812 (date of patent: Nov. 11, 2018) discloses a system and method for adjusting the attenuation amount using an external controller. However, the VOA disclosed in U.S. patent Ser. No. 07/450,812 requires an external controller to compensate and adjust the attenuation characteristics and thus has a disadvantage of requiring additional parts.

In the following, only parts necessary for understanding embodiments of the present disclosure will be described, and descriptions of other parts will be omitted in the scope not disturbing the subject matter of the present disclosure.

The terms and words used herein should not be construed as limited to ordinary or dictionary definition, and should be construed in light of the meanings and concepts consistent with the subject matter of the present disclosure on the basis of the principle that the inventor can properly define his own invention as the concept of the term to describe it in the best way. It is therefore to be understood that embodiments disclosed herein are merely exemplary and various equivalents or modifications thereof are possible.

FIG. 1is a plan view illustrating an optical scanner having a self-angle adjustment function of a mirror, in a state before wire bonding, according to an embodiment of the present disclosure.FIG. 2is a plan view illustrating the optical scanner ofFIG. 1after wire bonding.FIG. 3is a cross-sectional view taken along line3-3ofFIG. 2.

Referring toFIGS. 1 to 3, an optical scanner100according to this embodiment is an optical scanner having a self-angle adjustment function of a mirror10, and may be manufactured through a MEMS process based on a silicon on insulator (SOI) substrate and a wafer.

The optical scanner100according to this embodiment includes the mirror10that reflects light, and an electrostatic actuator30that pivots the mirror10. The electrostatic actuator30includes a plurality of driving electrodes40and a fixed electrode unit50including a plurality of fixed electrodes60. The plurality of driving electrodes40are connected to the mirror10and arranged in rows. The fixed electrode unit50includes the plurality of fixed electrodes60that are arranged in alternating rows with the plurality of driving electrodes40and pivot the mirror10by an applied driving voltage. The plurality of fixed electrodes60include a plurality of main electrodes61and63to which the driving voltage is applied, and a plurality of additional electrodes65and67. The plurality of additional electrodes65and67are electrically isolated from the plurality of main electrodes61and63, and the driving voltage is selectively applied to the plurality of additional electrodes65and67. In addition, the optical scanner100according to this embodiment may further include connecting shafts21and23and a tilt unit80.

The respective parts of the optical scanner100according to this embodiment will be described hereinafter in detail.

The mirror10reflects the incident light. The mirror10reflects the incident light while pivoting in a predetermined angular range in response to the intensity of the driving voltage applied to the fixed electrode unit50.

The connecting shafts21and23include first and second connecting shafts21and23connected to opposite sides of the mirror10. The first and second connecting shafts21and23enable rotation (tilting) of the mirror10in a predetermined angular range by the driving voltage applied to the fixed electrode unit50. When applying the driving voltage to the fixed electrode unit50is stopped, the first and second connecting shafts21and23rotate the mirror10oppositely by the elastic force accumulated by the rotation to return it to its original position. At the other end of each of the first and second connecting shafts21and23opposite to one end to which the mirror10is connected, each of first and second ground pads25and27are formed.

The fixed electrode unit50includes the plurality of fixed electrodes60and a fixed electrode plate70to which the plurality of fixed electrodes60are connected. The fixed electrode plate70includes main electrode plates71and73to which the plurality of main electrodes61and63are connected together, and a plurality of additional electrode plates75and77to which the plurality of additional electrodes65and67are connected. The fixed electrode plate70is rotatably installed via a pair of fixed shafts55. The pair of fixed shafts55may be formed parallel to the connecting shafts21and23.

The fixed electrode unit50includes a main electrode part51and an additional electrode part53. The main electrode part51includes the plurality of main electrodes61and63and the main electrode plates71and73to which the plurality of main electrodes61and63are connected and supported. The additional electrode part53is disposed adjacent to the main electrode part51and is electrically isolated from the main electrode part51. The additional electrode part53includes the plurality of additional electrodes65and67and the plurality of additional electrode plates75and77connected to the plurality of additional electrodes65and67.

The additional electrode plates75and77are formed to be wider than the connected additional electrodes65and67so that bonding wires95and96can be stably bonded. Although in this embodiment the plurality of additional electrodes65and67are exemplarily shown as being connected to the additional electrode plates75and77, the present disclosure is not limited thereto. That is, at least one additional electrode may be connected to the additional electrode plate.

In the plurality of fixed electrodes60, the plurality of main electrodes61and63are centrally arranged, and the plurality of additional electrodes65and67are arranged on both sides of the plurality of main electrodes61and63. In the plurality of additional electrodes65and67, the additional electrodes65and67to which the driving voltage is applied may be selected from the additional electrodes65and67adjacent to the plurality of main electrodes61and63.

The number of the plurality of additional electrodes65and67is smaller than the number of the plurality of main electrodes61and63. That is, the main electrodes61and63occupying a majority of the fixed electrodes60determine a main rotation angle of the mirror10. Through the number of the additional electrodes65and67to which the driving voltage is applied, the main rotation angle is finely adjusted under applying of the same driving voltage. Among the plurality of additional electrodes65and67, the number of the additional electrodes65and67to which the driving voltage is applied is proportional to an angular size of the mirror10to be adjusted. That is, as the angular size of the mirror10to be adjusted increases, the number of additional electrodes65and67also increases. Alternatively, as the amount of attenuation to be adjusted increases, the number of additional electrodes65and67also increases.

Bonding wires91,92,93,94,95, and96apply the driving voltage necessary for the pivoting of the mirror10to the electrostatic actuator30from a power supply unit. As the bonding wires91,92,93,94,95, and96, a material having good electrical conductivity such as gold, copper, aluminum, or the like may be used.

For applying the driving voltage to the electrostatic actuator30, ground terminals110and120and power terminals130and140are disposed around the electrostatic actuator30. The ground terminals110and120are disposed close to the connected first and second ground pads25and27, respectively. The power terminals130and140are disposed close to the connected main electrode plates71and73, respectively. The ground terminals110and120include a first ground terminal110and a second ground terminal120. The power terminals130and140include a positive power terminal130and a negative power terminal140.

The bonding wires91,92,93,94,95, and96include first to fourth bonding wires91,92,93, and94, and first and second additional bonding wires95and96.

The first bonding wire91electrically connects the first ground pad25and the first ground terminal110.

The second bonding wire92electrically connects the second ground pad27and the second ground terminal120.

The third bonding wire93electrically connects the positive power terminal130and the main electrode plates71and73to which the positive power is to be applied.

The fourth bonding wire94electrically connects the negative power terminal140and the main electrode plates71and73to which the negative power is to be applied.

The first and second additional bonding wires95and96electrically connect the power terminals130and140and the additional electrode plate75to which the driving voltage is to be applied. By the first and second additional bonding wires95and96, the additional electrode plate75is electrically connected to the power terminals130and140to which the main electrode plates71and73of the side on which the additional electrode plate75is disposed are connected. Disclosed in this embodiment is an example in which the additional electrode plate75disposed on both sides of the main electrode plates71and73to which the positive power is applied is electrically connected by the first and second additional bonding wires95and96to the positive power terminal130. Conversely, the additional electrode plate75disposed on both sides of the main electrode plates71and73to which the negative power is applied may be electrically connected by the first and second additional bonding wires to the negative power terminal140.

The number of the additional electrodes65and67connected by the first and second additional bonding wires95and96is determined in consideration of a predetermined amount of attenuation and an angle of light reflected depending on the rotation of the mirror10in a state where the driving voltage is applied only to the main electrode part51.

In order for the mirror10to be stably rotated through connection of the additional electrodes65and67, the same number of additional electrodes65and67to be connected may be selected vertically or horizontally around the mirror10.

On the other hand, if the target rotation angle of the mirror10can be ensured with the driving voltage applied to the main electrodes61and63, there is no need to apply the driving voltage to the additional electrodes65and67. That is, as shown inFIG. 1, the first and second additional bonding wires95and96may be omitted. The first and second additional bonding wires95and96are used only when connection of the additional electrodes65and67is required.

In this embodiment, in order to apply the driving voltage to the additional electrodes65and67, an example of connecting the additional electrodes65and67and the positive power terminal130through the first and second bonding wires95and96is described, but the invention is not limited thereto. For example, the additional electrodes65and67to which the driving voltage is to be applied may be electrically connected to the adjacent main electrode plates71and73through additional bonding wires.

In addition, the tilt unit80applies a physical force to the fixed electrode plate70of the fixed electrode unit50to shift the plurality of driving electrodes40and the plurality of fixed electrodes60from each other. In this embodiment, an example in which the tilt unit80lifts an outer portion of the fixed electrode plate70around the pair of fixed shafts55so that the plurality of fixed electrodes60are tilted down below the plurality of driving electrodes40is disclosed, but the invention is not limited thereto. For example, when the tilt unit80lifts an inner portion of the fixed electrode plate70around the pair of fixed shafts55, the plurality of fixed electrodes60may be tilted up above the plurality of driving electrodes40.

Although in this embodiment an example in which the tilt unit80lifts the fixed electrode plate70under the fixed electrode unit50to shift the plurality of fixed electrodes60with respect to the plurality of driving electrodes40, the invention is not limited thereto. For example, the tilt unit may shift the plurality of fixed electrodes with respect to the plurality of driving electrodes by pressing the fixed electrode plate above the fixed electrode unit. That is, the tilt unit80shifts the plurality of fixed electrodes60to have a certain angle with respect to the plurality of driving electrodes40maintaining a horizontal state.

The optical scanner100according to this embodiment may be applied to a variable optical attenuator (VOA) or a switch, but it is not limited thereto.

In the optical scanner100according to this embodiment, the plurality of driving electrodes40are formed on each of the first and second connecting shafts21and23.

The plurality of driving electrodes40includes a plurality of first driving electrodes41formed on both sides of the first connecting shaft21, and a plurality of second driving electrodes43formed on both sides of the second connecting shaft23.

The plurality of fixed electrodes60includes a plurality of first fixed electrodes61and65arranged in alternating rows with the plurality of first driving electrodes41, and a plurality of second fixed electrodes63and67arranged in alternating rows with the plurality of second driving electrodes43.

The plurality of first fixed electrodes61and65include a plurality of first main electrodes61arranged and formed from a starting portion of the first connecting shaft21extending from the mirror10, and a plurality of first additional electrodes65arranged and formed outside the plurality of first main electrodes61.

The plurality of first main electrodes61are collectively connected to the first main electrode plate71. The plurality of first additional electrodes65are connected to a plurality of first additional electrode plates75. In this embodiment, an example in which two first additional electrodes65are connected to one first additional electrode plate75is disclosed.

In addition, the plurality of second fixed electrodes63and67include a plurality of second main electrodes63arranged and formed from a starting portion of the second connecting shaft23extending from the mirror10, and a plurality of second additional electrodes67arranged and formed outside the plurality of second main electrode63.

The plurality of second main electrodes63are collectively connected to the second main electrode plate73. The plurality of second additional electrodes67are connected to a plurality of second additional electrode plates77. In this embodiment, an example in which two second additional electrodes67are connected to one second additional electrode plate77is disclosed.

The first and second main electrode plates71and73formed on each of both sides of the first and second connecting shafts21and23may be integrally formed. That is, the plurality of driving electrodes60and the fixed electrode unit50are formed symmetrically left and right about the first and second connecting shafts21and23.

In this embodiment, although an example in which the additional electrode parts53are respectively formed in the fixed electrode units50formed on both sides of the first and second connecting shafts21and23is disclosed, it is not limited thereto. For example, the additional electrode part53may be formed in only one of the fixed electrode units50of both sides.

Meanwhile, although the present embodiment discloses an example in which the plurality of driving electrodes40are formed from the connecting shafts21and23connected to the mirror10, the invention is not limited thereto. For example, a plurality of driving electrodes may be formed on one side or opposite sides of a mirror mounting plate onto which the mirror is attached.

In the optical scanner100according to the present embodiment, the mirror10rotates clockwise or counterclockwise at a certain angle around the first and second connecting shafts21and23as a rotation axis due to a potential difference occurring between the plurality of fixed electrodes60positioned on both sides of the plurality of driving electrodes40. When the power applied to the fixed electrode unit50is cut off, the mirror10rotates and returns to its original position by the elastic force accumulated on the first and second connecting shafts21and23.

In addition, by adjusting the number of the additional electrodes65and67connected to the main electrode part51, the rotation angle of the mirror10can be easily fine-adjusted under the same applied voltage.

Hereinafter, a method for adjusting a mirror angle of the optical scanner100according to this embodiment will be described with reference toFIGS. 1 to 4.FIG. 4is a flow diagram illustrating a method for adjusting a mirror angle of an optical scanner100according to an embodiment of the present disclosure.

First, at step S10, a driving voltage is applied only to the plurality of main electrodes61and63as shown inFIG. 1, and the angle of light reflected depending on the rotation of the mirror10is measured. This step S10is performed while the electrostatic actuator30is electrically connected via the first to fourth bonding wires91,92,93, and94. That is, the first bonding wire91electrically connects the first ground pad25and the first ground terminal110. The second bonding wire92electrically connects the second ground pad27and the second ground terminal120. The third bonding wire93electrically connects the positive power terminal130and the main electrode plates71and73to which the positive power is to be applied. The fourth bonding wire94electrically connects the negative power terminal140and the main electrode plates71and73to which the negative power is to be applied. The step S10is performed in a state where the additional electrodes65and67are not electrically connected to the power terminals130and140.

Next, at step S20, the number of additional electrodes65and67to be connected is determined based on the measured angle of light and a predetermined amount of attenuation. Here, the predetermined amount of attenuation is determined based on a predetermined light angle. A difference value between the measured light angle and the predetermined light angle is calculated, and the number of additional electrodes65and67corresponding to the angle of the mirror10to be adjusted is determined based on the calculated difference value.

Next, at step S30, the determined number of additional electrodes65and67are connected to the power terminal130as shown inFIG. 2to apply power to the determined number of additional electrodes65and67. That is, the first and second additional bonding wires95and96electrically connect the power terminal130and the additional electrode plate75to which the determined number of additional electrodes65and67are connected.

As such, applying the driving voltage to the additional electrodes65and67allows obtaining the optimally corrected rotation angle of the mirror10.

Meanwhile, after the wire bonding of the step S30, a step of applying the driving voltage having applied to the main electrode part51to the wire-bonded additional electrodes65and67and thereby verifying whether the mirror10rotates at the corrected rotation angle may be further performed.

As described hereinbefore, the optical scanner100according to the present embodiment includes the main electrodes61and63and the additional electrodes65and67in the fixed electrode unit50, and the attenuation characteristics can be compensated and adjusted without adding an external controller by adjusting the number of the additional electrodes65and67to which the driving voltage will be applied. That is, the angle of light reflected depending on the rotation of the mirror10is measured by applying the driving voltage to the main electrodes61and63. Based on the measured angle of light and a predetermined amount of attenuation, the number of additional electrodes65and67to be connected is determined. In order to apply power to the determined number of additional electrodes65and67, the power terminal130is electrically connected to the determined number of additional electrodes65and67via wire bonding. Therefore, it is possible to adjust the angle of the mirror10in consideration of the attenuation characteristics of the optical scanner100under the same driving voltage.

As such, performing the self-angle adjustment of the mirror10in the module alignment step can optimize the performance of the module by minimizing the angular deviation of the mirrors10when manufacturing the module including the plurality of optical scanners100according to the present embodiment, and can also improve the manufacturing yield of the optical scanner100.

In addition, the optical scanner100according to the present embodiment allows adjusting the angle of the mirror10through a simple process such as wire bonding in the module alignment step.

Meanwhile, the embodiments disclosed in the description and drawings are merely presented as specific examples to aid understanding and are not intended to limit the scope of the present disclosure. It is apparent to those of ordinary skill in the art to which the present disclosure pertains that other modifications based on the technical contents of the present disclosure can be implemented in addition to the embodiments disclosed herein.