TWI279582B - A torsional micromirror with a large torsional angle - Google Patents

Abstract

This patent discloses a torsional micromirror which comprises at least a supporting frame with a hollow part in the middle, a mirror plate suspended in the hollow part of the so-called supporting frame, one or more torsional beams which connect the so-called mirror plate to the so-called supporting frame and conducting coils on the so-called mirror plate and supporting frame. The so-called torsional beam is composed with straight portions and curved portions in order to release the effective torsional coefficient. Thus, a large torsional angle can be achieved without changing the material or increasing the dimension of the micromirror, the magnetic field or the magnitude of the current. Among a proper arrangement of the magnetic field and the direction of the current on the so-called conducting coil, the micromirror can be vibrated or twisted back and forth in one- or two-dimensional.

Description

1279582 玖, the invention relates to the technical field of the invention: The present invention relates to a torsional micromirror, and in particular to a micro-mirror structure having a large torsion angle, the micro-mirror structure according to the present invention A twist angle greater than 10 degrees can be produced using currents and magnetic fields that are much smaller than those required for conventional structures. Prior Art: In optical systems such as laser printers or bar code readers, the main components can be roughly divided into three parts: laser light source, light source scanning mechanism and reflective light source decoding device. The most important components are the design, manufacturing and control technology of the light source scanning mechanism. The traditional light source scanning mechanism is a combination of a polygon mirror (P 〇1 yg 〇η Mirror) and a rotating polygon mirror motor. . In the manufacturing process of the polygon mirror, the flatness of the mirror is the biggest factor. As for the motor of the rotating polygon mirror, it depends on the control technology to stabilize the rotation speed to achieve high resolution. Mirrors and motors that have traditionally been manufactured using precision machining are not only bulky, but also expensive to manufacture. At this stage, a galvanometer is used instead of a conventional polygon mirror for 5 1279582 scanning. At present, a variety of galvanometers have been proposed, such as driving by way of classification, which can be mainly divided into a heat-driven galvanometer, an electrostatic force-driven galvanometer, and an electromagnetic force-driven galvanometer. Thermally driven galvanometers, which operate in high temperature environments (usually above 400 °C), affect the life and reliability of the galvanometer components. For electrostatically driven galvanometers (as disclosed in U.S. Patent No. 4 3 1 7 6 1 1), it is difficult to achieve a large angle due to the limitation between the mirror surface and the plates. Torsing; in addition, in order to make the galvanometer twist, a high voltage (usually higher than 100 volts) is required to generate a high electrostatic field, and the generation of a high voltage is not easily integrated for the current integrated circuit. The electromagnetic force-driven galvanometer mirrors the mirror surface of the galvanometer by the action of the coil current and the magnetic field. Therefore, it is not necessary to rotate at a large angle as the lower electrode plate of the static electricity driven galvanometer. The conventional electromagnetic force driven galvanometer structure is as shown in the first figure. The structure includes a mirror plate 10, two torsional transmission rods 12a and 12b (torsional beam), a supporting frame 13 and a mirror. The conductive coil 14 on the panel 10 is composed of. The galvanometer uses an electromagnetic force (or Lorentz force) to generate the torsion. However, this structure is not easy when the current is less than 1 mA or the magnetic field is less than 30,000 Gauss. Produces a twist angle of more than 1 degree. Especially when the galvanometer is manufactured using microsystem technology (M i c r 〇 S y s t e m Technologies), because of its manufacture 6 1279582

It is mostly used as a semiconductor material, such as polycrystalline or single crystal (sing 1 ecrysta 1 ), and its young's modulus is similar to steel (~ΙΟΟχΙΟ9 P a ), which is difficult to be applied. The micro-electromagnetic force is reversed. In order to have a large torsion angle of the mirror panel 10 made of semiconductor material, it is conventionally required to place the galvanometer in a high magnetic field (greater than 6000 gauss) or high current (greater than 200 mA). . However, in addition to energy consumption, the electromagnetic interference extended in this high magnetic field environment also brings reliability problems to the surrounding integrated circuits. Summary of the invention:

In view of the above-mentioned drawbacks of the conventional electromagnetic force-driven galvanometer structure: as the conventional galvanometer structure is difficult to be twisted because its Young's coefficient is similar to steel, and in order to achieve the required torsion angle, a south magnetic field is usually applied or The south current is on the galvanometer structure, which has the disadvantages of high energy consumption and high electromagnetic interference. Therefore, the main object of the present invention is to provide a galvanometer structure made of a flat plate with a large torsional sensitivity of the torsion transmission rod under the same applied current, in view of the above disadvantages; The transmission rod, the electrode plate and the electric coil are arranged so that the galvanometer operates at a frequency that does not require resonance 1279582, providing one or two or two-dimensional vibration modes. The galvanometer structure according to the present invention comprises a bracket having a hollow portion, a mirror panel is placed on the hollow portion, and is connected to the bracket via an or an array of torsion transmission rods, wherein any of the torsion transmission rods are singular or The straight portion and the curved portion are formed. Another or an array of conductive coils is placed on the mirror panel and the torsion drive rod.

Implementation method:

Without limiting the spirit and scope of the present invention, the following is a description of the embodiments of the present invention; those skilled in the art, after understanding the spirit of the present invention, can apply the galvanometer structure of the present invention to Among the various reflecting devices, the structure of the present invention allows the torsion transmission rod to have greater torsional sensitivity at the same current and lower the equivalent spring constant. The application of the present invention is not limited to the preferred embodiments described below. Referring to the second figure, a schematic diagram of a galvanometer structure after completion according to the present invention includes a bracket 20 having a hollow portion 25, a mirror panel 21 is placed on the hollow portion 25, and via two transmission rods 2 2 and 2 3 is connected to the bracket 20, wherein the transmission rod 22 is formed by the straight portions 2 2 a and 2 2 b and the curved portion 2 2 c, and the transmission rod 23 is composed of the straight portions 2 3 a and 2 3 b Formed by a curved portion 1279582 curved portion 2 3 c , a conductive coil 24 is placed on the mirror panel 2 1 and the two transmission rods 2 2 and 2 3 , and the mirror panel 21 is used to reflect the incident light. In the prior art of the first figure, the torsion angle can be determined by the torsion transmission rods 12a and 12b, and the torque required to twist the two torsion transmission rods 12a and 1 2 b is as shown in the following formula (1): 3>

Gwbtb 16 τ .3« ·θ = Κβ·θ

Wherein "to reverse the length of the transmission rods 12a and 12b, W & is the width of the torsion transmission rods 12a and 12b, h is the thickness of the torsion transmission rods 1 2 a and 1 2 b, and G is the shear modulus of the material (shear Modulus can be expressed by the following formula (2): 2 (1+v)

The fifth is the Young's coefficient ^ v is the Poisson's ratio, which is called the torsional constant in the formula (1), and its size can be determined by the material properties of the torsion transmission rods 1 2 a and 1 2 b. The appearance shape (/ & length, width and h thickness) determines that equation (1) describes the relationship between torque Γ e and torsion angle 0. However, since the Young's modulus of the semiconductor material is large, the shear modulus is also increased, so that the final torsion constant becomes large. The large torsion constant will make the mirror 9 1279582 mirror rotation difficult; even if it is manufactured by micro-system technology, the torsion transmission rods 1 2 a and 1 2 b are miniaturized, and the applied electromagnetic force is also miniaturized under the same current and magnetic field, such as Torsional transmission rods 1 2 a and 1 2 b are still difficult to produce large torsion angles without new materials and new structural applications. Accordingly, the present invention proposes a new structure of a torsion transmission rod which can be lowered by adding curved portions 2 2 c and 23c without changing the material used originally. The torsion constant therefore produces a large torsion angle of zero at the same torque. Wherein, the magnitude of the torsion constant ruler ^ is reduced by a proportional value/equivalent, and the formula (1) can be described by the following formula: Κ·κβ·θ (3) where the ratio of the torsion constant ruler e is reduced/size It relates to the geometry of the torsion transmission rods 2 2 and 2 3 curved portions 2 2 c and 2 3 c. In the following, an embodiment will be described to explain the fact that the torsion constant rods can be effectively reduced by the structure of the torsion transmission rods 22 and 23 which are joined to the curved portions 22c and 23c. If the galvanometer structure as shown in the first figure is used, it is assumed that the galvanometer structure uses a single crystal germanium material having a thickness of 2 μm, wherein the area of the mirror panel 10 is 250 x 250 μπι, and the length of the torsion transmission rods 12a and 12b is 250. μ m, width 10 μm, in this case, single crystal stone material 10 1279582

The Young's coefficient is 1 3 Ο X 1 0 9 P a, and the wave-to-loose ratio is 0 · 2 8. After the calculation of the formula (1.), the torsion constant ruler is 1 · 3 1 3 X 1 0 " 7 Nt-m/rado

At this time, if the current transmitted through the conductive coil 14 is 1 m A, the magnetic field generated at this time will be 1000 Gauss, and the galvanometer structure itself will generate a torque of 7% of about 5 x 1 (K8 Nt-m). This torque is generated by a Lorentz force, a torque Γ, and a torsion constant. After the calculation of the formula (1), the torsion angle Θ is about 0.0027 after the calculation as in the first figure. Increasing the current or magnetic field by about 50,000 times, the galvanometer has a rotation angle greater than 10. The above radiant mirror structure, as shown in the second figure, is used to twist the transmission rods 2 2 and 2 3 The structure, the curved portions 2 2 c and 2 3 c are added, and the structures of the curved portions 2 2 c and 2 3 c have the same thickness as the mirror panel 21 as shown in the third drawing.

2 μπι, the width of the curved portions 22c and 23c, as shown in FIG. 3A, 31 is 10 μπι; the height is as shown in FIG. 3A, 33 is 250 μm; the spacing is as shown in FIG. 3A, 32 is 2 μ m 〇 As shown in the second figure, the left side of the curved portion 2 2 c is connected to the bracket 20 by the straight portion 22a, and the right side is connected to the mirror panel 21 by the straight portion 2 2 b. The right side of the other curved portion 2 3 c is connected to the bracket 20 by the straight portion 2 3 a , and the left side π 1279582 is connected to the mirror panel 21 by the straight portion 2 3 b. Each of the straight portions 22a, 22b, 23a, and 23b has a length of 108 μm, a width of 10 μm, and a thickness of 2 μm, so that the total length of the torsion transmission rods 2 2 and 2 3 is also 250 μm. The examples in the first figure are the same. By the simulation method, such as using the Finite Element Method, the torsion constant is 5. 5 4 4 X 1 0 · 9 Nt - m / rad; and in the formula (3), the torsion angle e is lowered The size ratio value / is 〇 2 4 2, that is, by adding the torsion transmission rods 2 2 and 2 3 to the curved portion, the torsion constant 夂e of the conventional straight torsion transmission rod of the same length can be reduced by a proportional value /. Therefore, the galvanometer structure of the present invention can use a relatively small torque 即可 to produce the same torsion angle as the conventional structure. Under the same operating conditions as in the previous example, 0 · 1 2 9 can be generated. The twist angle is reduced by 4 7 times. It is necessary to increase the current or magnetic field by about 50,000 times, and the galvanometer is greater than 10 0. In the case of the above corners, it is only necessary to increase the current or the magnetic field by about 100 times; if the applied current is 100 m A, the galvanometer can be made larger than 1 0 in the magnetic field environment of 1000 gauss. Above the corner. As can be seen from the above example, the torsion transmission rod structure of the present invention can effectively reduce the effective torsion constant ruler e and increase the torsion angle 在 without changing the material and increasing the total length of the torsion transmission rod. 12 1279582 It is worth noting that there are several vibration modes of the galvanometer structure. Generally speaking, the two vibration modes are located at a low frequency. The first one is to twist the transmission rod as a torsion axis and to oscillate back and forth along the axis. The second type is to bend up and down along the vertical axis of the mirror to vibrate back and forth. The mirror panel vibrates up and down. For a galvanometer structure having a straight twisting transmission rod, as disclosed in U.S. Patent No. 5,629,790, the resonance frequency difference of the above two vibration modes can be as high as 20%. However, since the present invention adds the torsion transmission rods 2 2 and 2 3 to the curved portions 2 2 c and 2 3 c, respectively, the torsion constant scale and the equivalent elastic modulus can be simultaneously reduced, that is, the torsion transmission rods 2 2 and 2 3 The twisting and bending are more likely to occur, so that the resonance frequencies of the above two types are close to each other, that is, less than 20%, and the present invention is different from the patent. Further, when the bending moment of the torsion transmission rods 2 2 and 2 3 is smaller than the torsional moment, the first vibration mode is a vibration mode of up and down bending, and the second vibration mode is a vibration mode of left and right torsion. The curved portions 2 2 c and 2 3 c of the torsion transmission rods 2 2 and 2 3 of the present invention may also be as shown in the third B and third C drawings, that is, a plurality of curved portions are used to constitute the torsion transmission rod of the present invention. . Figure 4 is a design of another curved portion that can also be applied to the torsion transmission rod of the present invention. The galvanometer conventionally designed, as shown in the first figure, has two conductive coils 14 on the mirror panel 10, so that the galvanometer has 13 1279582 different modes of vibration (such as left and right vibration or up and down vibration), usually applied A current or a magnetic field having the same frequency and oscillating mirror resonance frequency drives the galvanometer to operate the galvanometer in different vibration modes to generate vibrations of different modes. In order to prevent the galvanometer from being used at the resonant frequency, vibrations of different forms can also be obtained, and the present invention provides an easy method. Referring to the fifth figure, if the electrode connecting the conductive coil 24 is divided into two pairs of electrodes, 34a and 34b and 35a and 35b, respectively, wherein the electrode pairs 3 4 a and 3 4 b constitute a current path 34, and the other pair of electrodes 3 5 a and 3 5 b constitute another current path 35. By controlling the flow direction of the current in the current path, the mirror panel vibration mode can be determined in the case of a constant magnetic field direction. 6A to 6D are respectively a cross-sectional view taken from AA' of the fifth figure, wherein the magnetic field directions are left to right in the sixth A and sixth B, and the current path 34 is The direction of current in 35 is to point out the paper surface, and the other is to point to the paper surface. At this time, the vibration mode generated by the current and the magnetic field causes the mirror panel to be twisted left and right. On the other hand, as shown in the sixth C diagram and the sixth diagram D, wherein the magnetic field direction is also from left to right, and the current directions in the current paths 34 and 35 are both indicating the paper surface as shown in the sixth C diagram. Or both point to the paper surface as shown in the sixth D picture. At this time, the vibration mode generated by the action of the current and the magnetic field causes the mirror panel to vibrate up and down. Therefore, in the case of the fixed magnetic field 14 1279582, by arranging the current directions of the two sets of electric coils, even if the applied current frequency is not at the resonant frequency of the galvanometer structure, there may be different vibration forms of up and down vibration and left and right twist. By twisting the curved portion of the transmission rod, the torsion constant and the equivalent spring constant of the torsion transmission rod can be reduced and easily twisted. Therefore, through the arrangement as shown in the seventh figure, the single-dimensional galvanometer can have two-dimensional vibration. As shown in the seventh embodiment, the galvanometers are connected to the torsion transmission rods 73a, 73b, 73c, and 73d on the four sides of the mirror surface 74, and on the mirror surface 74 and the four sets of torsion transmission rods 73a, 73b, 73c, and 73d. The two sets of coils 7 1 and 7 2 are respectively located in different layers and the two sets of coils are not connected to each other. A magnetic field 75 has an X component 75a and a y component 7 5 b on the xy axis, respectively. When the coil 7 1 applies a current such as a direction 76, the mirror will be twisted along the X axis; meanwhile, as the coil 7 2 is applied as a direction 7 7 At the current, the mirror will twist along the y-axis. Such a mirror that is twisted along the X-axis and the y-axis will synthesize a galvanometer with a two-dimensional scanning mechanism. For example, the two current coils 7 1 and 7 2 of the seventh figure are divided into two groups as shown in the fifth figure, and a total of four sets of current coils and eight electrode plates are used. If combined in a suitable current direction, it is possible to remove the two-dimensional scanning along the X-y axis and to cause the mirror to vibrate along the surface of the paper. As shown in Figure 8A, the two-layer current coil is divided into eight electrode plates, 81a, 81b, 81c, 81d, 82a, 82b, 82c 15 1279582 and 8 2 d, respectively located in the χ direction and the y direction, by the eighth The X-direction currents 7 6 and y 7 7 shown in Figure A can be divided into two-dimensional scans along the χ-y-axis direction to cause the mirror to vibrate down the plane of the paper. Figure 8B shows a layer of current coil divided into four applications as shown in Figure 8B, the χ direction current I x 8 and the y direction current I y 8 6 b, 8 6 d can be divided by χ - bis In addition to the dimensional scanning, the mirror surface can be made along the same direction - the two-dimensional scanning in the y-axis direction plus the turning along the paper surface. Note that the galvanometer structure of the present invention has four twisting transmissions as shown in the figure. The mirror panel and the bracket can be connected by a plurality of twists. The present invention has been disclosed in a preferred embodiment, and is not intended to limit the scope of the present invention. The definition of the application is subject to the definition. It can be grouped by applying currents such as directional. The y action can be achieved by the 6 a, 8 6 c y-axis direction. It is worth noting that the lever is not only a common stick, but also lacks the position, and does not take off the move and the application. Patent No. 1279582 The following is a brief description to make the above and other objects, features and advantages of the present invention more obvious and easy to understand. Several preferred embodiments, together with the drawings, are described in detail as follows:

The first figure shows a schematic diagram of a conventional galvanometer structure. The second figure shows the galvanometer structure after completion in accordance with a preferred embodiment of the present invention. The third to third C diagrams show various design structures of the torsion transmission rod bending portion. The fourth figure shows the design of the other curved part of the torsion transmission rod.

Figure 5 is a schematic view showing the structure of a galvanometer after completion in accordance with a preferred embodiment of the present invention. 6A to 6D are cross-sectional views taken from AA' of the fifth figure, respectively. The seventh figure shows the galvanometer structure not completed in accordance with another preferred embodiment of the present invention. Figs. 8A and 8B are schematic views showing the structure of a galvanometer using eight electrode plates. 17 1279582 Schematic description 1 〇 mirror panel 1 2 a and 1 2 b torsion transmission rod 13 bracket 1 4 conductive coil 2 0 bracket 2 1 mirror panels 73a, 73b, 73c, 73d, 83a, 83b, 83c, 83d, 2 2 and 2 3 torsion transmission rods 22a, 22b, 23a and 23b straight portions 2 2 c and 2 3 c curved portions 2 4 conductive coils 2 5 hollow portions 3 1 width 3 2 pitch 3 3 heights 3 4 and 3 5 current paths 34a , 34b, 35a, 35b, 71, 72, 81a, 81b, 81c, 81d, 82a, 82b, 82c and 82d electrodes 76, 77, 86a, 86b, 86c and 86d currents 7 5 and 8 5 magnetic field directions 75a, 75b, 85a and 85b magnetic field on the xy axis component 18

Claims (1)

1279582 X. Patent application scope 1. A galvanometer device comprising at least: a bracket with a hollow portion; a mirror device located at the hollow portion; One or a plurality of torsion transmission rods having a curved portion on a side of the mirror device for connecting the mirror device and the bracket; and one or a plurality of arrays of conductive coils respectively located on the mirror device and the opposite torsion transmission rod The galvanometer device of claim 1, wherein the mirror device is located in the hollowing out, and the galvanometer device generates a motion of the galvanometer device. Part of it. % 3 _ As in the galvanometer device described in claim 1, the curved portion is of the "S" type structure. The galvanometer device of claim 1, wherein the torsion transmission rod is connectable at a symmetrical or asymmetrical position on the side of the mirror device. 19