JP3684003B2 - Optical scanner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small optical scanner that reflects light from a light source and scans the reflected light in one or two dimensions.
[0002]
[Prior art]
Also, as an example of a small optical scanner, there is known an optical deflector that uses a silicon substrate (semiconductor substrate) and a torsion spring, and that scans light by swinging a reflecting mirror by electromagnetic force. Yes.
[0003]
Such an optical scanner is disclosed, for example, in the document “TECHNICAL DIGESTOF THE SENSOR SYMPISOUM, 1995.pp17-20”.
[0004]
FIG. 9 is a diagram showing the configuration of the optical scanner disclosed in this document. In this optical scanner, a reflecting mirror 34, a torsion spring 33, and a fixed frame 50 that supports these are integrally formed on a semiconductor substrate 31 made of silicon as an optical deflector.
[0005]
A planar coil 35 is laid on the peripheral edge of the reflecting mirror 34, and the planar coil 35 is electrically connected to the electrode 36 formed on the fixed frame 50 through the torsion spring 33. .
[0006]
In addition, the circular permanent magnet 38 is disposed at a location where the magnetization direction is parallel to the reflecting mirror 34 and about 45 degrees with the axial direction of the torsion spring 33 via the spacer insulating substrate 40. .
[0007]
A Lorentz force is generated in the planar coil 35 to which an alternating current is applied by an interaction with the magnetic field generated by the permanent magnet 38. By this Lorentz force, the reflecting mirror 34 swings in the torsion direction of the torsion spring 33.
[0008]
When a current having the same frequency as the resonance frequency defined by the elastic characteristics of the torsion spring 33 and the mass and center of gravity of the reflecting mirror 34 is applied to the planar coil 35, the maximum amplitude of the current value can be obtained.
[0009]
Here, the damping coefficient is reduced by vacuum-sealing the reflecting mirror 34. In FIG. 9, reference numeral 39 is a gas adsorbent, 41 is a front cover insulating substrate, and 42 is a back insulating substrate.
[0010]
[Problems to be solved by the invention]
However, the above-described prior art shown in FIG. 9 does not describe the viewpoints of durability and protection from the atmosphere of electrical elements such as the wiring of an optical scanner that vibrates with a large deflection angle.
[0011]
Accordingly, the present invention pays attention to such a point, and an object of the present invention is to provide an optical scanner having an electric element exhibiting high durability in an optical scanner that vibrates with a large deflection angle.
[0012]
[Means for Solving the Problems]
The present invention includes a support for fixing to an arbitrary member, a movable plate having at least one surface reflecting light, and two elastic members connecting the support and the movable plate; A drive coil formed on the movable plate and a permanent magnet disposed in the vicinity of the movable plate so as to have a predetermined interval between the movable plate and applying an alternating current to the drive coil in, in the optical scanner for performing the movable plate torsional vibration as the torsion spring elastic member, the elastic member is made of only insulating organic elastic layer to have a electric element therein, the support and the movable plate above It is formed to reach the body.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
<First Embodiment> FIGS. 1 to 5 are views showing a first embodiment of an optical scanner according to the present invention.
[0015]
The optical scanner according to the first embodiment can perform one-dimensional light scanning. FIG. 1 is a perspective view of the optical scanner, and FIGS. 2 and 3 are respectively shown in FIG. It is AA 'sectional drawing of a perspective view, and BB' sectional drawing. FIG. 4 shows a drive coil used in the optical scanner, and FIGS. 5A to 5J are diagrams showing a manufacturing process of the optical scanner.
[0016]
The first embodiment is configured as follows. This optical scanner includes a movable plate 101, an elastic member 102, a support body 103, and a permanent magnet 104. The movable plate 101 is formed with a reflection surface 105 for reflecting light, and the back surface of the movable plate 101 in FIG. It is desired that the main material used for the movable plate 101 does not deform the reflecting surface during vibration. Here, single crystal silicon, which is a highly rigid material, is used as the main material of the movable plate 101. In addition to the single crystal silicon, the movable plate 101 is made of silicon nitride, aluminum, or a polyimide material.
[0017]
Silicon nitride is used as a mask material when manufacturing an optical scanner, but is used as a residue for insulation from silicon, and aluminum is used as a wiring for the drive coil 106 and a contact pad 107 at the start and end of the drive coil. Is used as a mirror material for the reflecting surface 105. The polyimide is formed so as to sandwich the drive coil 106 from above and below, so that the electrical elements including the insulation between the coil wirings and the contact pads 107 are not exposed to the atmosphere.
[0018]
The elastic member 102 has a polyimide film extending from the movable plate 101 as a main material, and a wiring 108 extending from the contact pad 107 toward the support body 103 is formed therein. The wiring 108 is also formed of aluminum. The support 103 is used as an adhesive portion for fixing the optical scanner to die cast or the like, and a bonding pad 109 for supplying electric power from the outside to the drive coil 106 through the wiring 108 is formed.
[0019]
This support 103 uses single crystal silicon as a main material. Since single crystal silicon has high rigidity, it is convenient for fixing to die cast or the like. In addition, the support 103 is prevented from being exposed to the atmosphere by sandwiching silicon nitride as a mask material for manufacturing an optical scanner, aluminum for forming the bonding pad 109 and the wiring 108, and the wiring 108 from above and below. For this purpose, a polyimide film or the like is used. As the polyimide film, a polyimide film extending from the movable plate 101 and the elastic member 102 is used. The single crystal silicon of the support 103 and the single crystal silicon used in the movable plate 101 are formed from the same substrate.
[0020]
As shown in FIG. 4, the drive coil 106 changes the line width of the wiring and the distance between the wirings on each side. That is, the wiring of the drive coil 106 formed in the vicinity of the permanent magnet 104 and parallel to the width direction is shorter than the wiring formed in other places, and the distance between the wirings is also shortened. . However, the thickness of the drive coil 106 is made uniform.
[0021]
Regarding the position of the permanent magnet 104, this optical scanner can be driven sufficiently by placing one permanent magnet in the vicinity of one side wall of the movable plate, but in the vicinity of two opposing side walls of the movable plate, respectively. Permanent magnets are arranged one by one, and the magnetization direction is aligned with the thickness direction of the movable plate 101, and the lower portion of the permanent magnet 104 is on an extension line of about 45 degrees above or below the drive coil 106 at the tip of the movable plate 101. Alternatively, the driving force can be further increased by disposing the upper end at a position where the upper ends meet.
[0022]
Next, a method for manufacturing the optical scanner of this embodiment will be described. This optical scanner can be manufactured by semiconductor manufacturing technology. FIG. 5 shows a method for manufacturing the optical scanner. There are only four types of materials used: single crystal silicon substrate, silicon nitride, polyimide and aluminum.
[0023]
First, the silicon substrate 110 is cleaned, and a silicon nitride film 111 is formed using a low-pressure CVD apparatus [FIG. 5 (a)]. The silicon nitride films 111 formed on both surfaces of the silicon substrate 110 are used as a mask material when the movable plate 101 and the support 103 are separated. Therefore, the silicon nitride film 111 on the back surface is patterned by removing the silicon by fluorine-based dry etching [FIG. 5 (b)]. A first polyimide layer 112 is formed on the silicon nitride film 111 opposite to the patterned surface [FIG. 5 (c)].
[0024]
As a formation method, a liquid polyimide solution is applied onto the silicon nitride film 111, uniformly formed by a printing method or a spin coating method, and sintered. By etching the sputtered aluminum on the first polyimide layer 112, the drive coil 106, the contact pad 107, and the bonding pad 109 are formed [FIG. 5 (d)]. Similarly to the first polyimide layer 112, the second polyimide layer 113 is coated with a liquid polyimide solution on the first polyimide layer 112, uniformly formed by a printing method or a spin coating method, and then sintered [FIG. )].
[0025]
At this time, the polyimide on the contact pad 107 and the bonding pad 109 is removed. The wiring 108 is formed by etching the aluminum sputtered on the second polyimide layer 113 [FIG. 5 (f)]. The third polyimide layer 114 is formed for the purpose of determining the rigidity of the elastic member 102 and for the purpose of protecting the contact pad from the atmosphere. After film formation, the polyimide on the bonding pad 109 is removed by photolithography and dry etching [FIG. 5 (g)]. In order to improve the bonding characteristics of the bonding pad 109, the sputtered aluminum 121 is further laminated [FIG. 5 (h)]. In order to manufacture the movable plate 101 and the support 103 from the silicon substrate 110, anisotropic etching of silicon is performed from the back surface of the substrate using an alkaline solution [FIG. 5 (i)].
[0026]
At this time, there is a silicon nitride film 111 under the first polyimide layer 112 that becomes the elastic member 102, and it becomes a protective layer for protecting the first polyimide layer 112 when the silicon substrate 110 is etched through. The silicon nitride film 111 exposed on the back surface of the elastic member 102, the movable plate 101, and the support 103 after the silicon through etching is removed by dry etching [FIG. 5 (j)].
[0027]
Thereafter, although not shown in FIG. 5, in order to remove the first polyimide layer 112 other than the portion forming the elastic member 102 from the back surface, oxygen-based dry etching is also performed, and light is reflected as necessary. An optical scanner is completed by forming a reflective surface with high reflectivity by sputtering aluminum on the surface.
[0028]
Next, the operation of this embodiment will be described. By applying an alternating current from the bonding pad 109, a Lorentz force is generated in the drive coil 106 that circulates at the tip of the movable plate 101 by interaction with a permanent magnet. The vector direction of this force is determined by the positional relationship between the permanent magnet 104 and the drive coil 106. In this case, a force is generated in the thickness direction of the movable plate 101. This optical scanner is formed so that the support 103 surrounds the movable plate 101. The elastic member 102 is formed so as to be connected to the support body 103 from two opposing sides of the movable portion 101.
[0029]
Therefore, the movable plate 101 can only perform torsional vibration with the central axis in the longitudinal direction of the two elastic members 102 as the rotation axis. Torsional vibration is determined by the product of the Lorentz force generated in the coil wiring 106 near the permanent magnet 104 and the distance from the central axis in the longitudinal direction of the two elastic members 102 to the coil wiring near the permanent magnet 104. The Lorentz force is determined by the performance and size of the permanent magnet 104, the number of turns of the drive coil 106, the wiring length, the amount of current applied to the drive coil 106, and the distance from the permanent magnet 104 to the drive coil 106. The reason why the drive coil 106 is formed to go around the outermost periphery of the movable plate is to increase the amount of generated force as much as possible.
[0030]
By fixing the support 103 to a die cast or the like and applying a current to the drive coil 106, the movable plate 101 starts to vibrate with the boundary between the support 103 and the elastic member 102 as a fixed end. By applying an alternating current at a frequency similar to the resonance frequency uniquely determined by the shape and material of the movable plate 101 and the elastic member 102, the movable plate 101 starts to vibrate with the maximum amplitude in the current value.
[0031]
Therefore, there are the following effects. The optical scanner in this embodiment can perform one-dimensional optical scanning. In this optical scanner, since the elastic member 102 rotates as a torsion spring, unlike the optical scanner using bending vibration, the reflection point of the reflecting surface 105 formed on the movable plate 101 does not move, and the optical design is improved. It is easy and the constant speed of the light scanning speed can be improved.
[0032]
In addition, since polyimide, which is an organic film, is used for the elastic member 102, brittle fracture is less likely to occur compared to the case where silicon as shown in the above-described prior art is used for the vibration member, and the necessary minimum A large deflection angle can be obtained while maintaining strength, and the electrical elements such as the drive coil 106, the wiring 108, and the contact pad 107 are formed inside the polyimide film, so that the electrical elements are hardly deteriorated by moisture. By providing the driving coil 106 inside the polyimide film, the insulation between the wirings of the driving coil 106 is also stabilized.
[0033]
The driving coil 106 shown in this embodiment has a shape devised to obtain a large driving force while suppressing power consumption and heat generated when a current is applied to the coil as much as possible.
[0034]
Here, the relationship between the driving force generated in the coil, the current value, the power consumption, and the amount of generated heat can be obtained by the following equations (1) to (3). The driving force F of the coil is
F = ni · B (1)
Where n is the number of turns of the coil, i is the amount of current flowing through the coil, and B is the average magnetic flux density on the wiring portion of the drive coil 106 formed close to the permanent magnet 104.
[0035]
Further, the power consumption P of the coil section and the heat generation amount J are
P = i ² · R (2)
J = i ² · R · t (3)
Can be expressed as Here, i is a current value, R is an electric resistance value of the coil, and t is a time during which the current flows.
[0036]
From equation (1), it can be seen that in order to increase the driving force F, at least one of the current amount i, the number n of turns, and the magnetic flux density B should be increased. In order to increase the number of turns and the magnetic flux density, it is necessary to change the structure, but increasing the amount of current is easy to realize.
[0037]
However, as can be seen from the equations (2) and (3), when the current value i flowing through the coil is increased, both the power consumption P and the heat generation amount J increase in proportion to the square of the current value i. This is not preferable.
[0038]
Therefore, it is conceivable to increase the average magnetic flux density B by increasing the number n of turns of the drive coil 106 or shortening the line width and wiring interval of the drive coil 106 so that the distance between the permanent magnet and the drive coil is shortened. In any case, the resistance value R of the drive coil 106 is increased, the power consumption is increased, and the heat generation amount is increased.
[0039]
That is, although the driving force F, power consumption P, and generated heat amount J are in a trade-off relationship, in order to suppress the power consumption P and generated heat amount J as much as possible and increase the driving force F, in this embodiment, As shown in FIG. 2, the line width is shortened only for the wiring that contributes to the driving force, and the distance between the wirings is also shortened so that the entire wiring is concentrated in the vicinity of the permanent magnet 104. Here, the reason why the wiring interval of the drive coil 106 that does not contribute to the drive force is increased in order to improve the production yield of the drive coil 106 and reduce the electrical resistance of the drive coil 106.
[0040]
In this embodiment, the optical scanner can be integrally formed, and there is almost no assembly work, and the productivity of the ultra-compact optical scanner can be improved. Further, since the semiconductor manufacturing technology is applied, the dimensional accuracy of the ultra-miniaturized optical scanner is high, and the vibration of the optical scanner does not become unstable due to individual parts or assembly problems.
[0041]
Of course, each configuration of this embodiment can be variously modified and changed. As a modification of the first embodiment, permanent magnets 104 at both ends may be connected to the yoke 120 as shown in FIG. 7 and 8 show the AA ′ and BB ′ cross sections in FIG. 6, respectively.
[0042]
At this time, the permanent magnets 104 at both ends have the magnetization direction parallel to the width direction of the elastic member 102 as shown in FIG. The permanent magnets 104 arranged at both ends through the yoke can unify the magnetic flux generated in the space between the permanent magnets 104 in a direction parallel to the width direction of the elastic member 102. Further, by using the yoke, the magnetic circuit becomes a closed loop circuit, and the energy of the magnetic field can be efficiently converted into the driving force as compared with the open loop as shown in FIG. Power consumption can also be reduced.
[0043]
In the first embodiment, the movable plate 101 scans light only in a one-dimensional direction because of the oscillating motion about the elastic member 102. For example, the movable plate 101 is different from the conventional technique shown in FIG. Similarly, the permanent magnet is provided separately from the support body 103, the elastic member and the drive coil are provided in duplicate, and the inner elastic member and the outer elastic member are provided so as to be orthogonal to the support body. Thus, it becomes possible to scan light in a two-dimensional direction.
[0044]
In the embodiments as described above, the present invention includes the following inventions.
[0045]
(1) A support for fixing to an arbitrary member, a movable plate whose at least one surface is a reflective surface that reflects light, an elastic member that connects the support and the movable plate, and at least one side is movable A drive coil formed on a plate and a permanent magnet arranged in the vicinity of the movable plate so as to have a predetermined interval between the movable plate, and by applying an alternating current to the drive coil, In the optical scanner in which the movable plate performs torsional vibration using the elastic member as a torsion spring, the elastic member has an electric element inside and is made of an insulating elastic film that reaches the movable plate and the support. An optical scanner characterized by that.
[0046]
(Corresponding Embodiment of the Invention) The embodiment relating to this invention corresponds to the first embodiment.
[0047]
As shown in the first embodiment, the drive coil according to claim 1 is a coil that generates a force that causes the movable plate to vibrate by interaction with a permanent magnet when an alternating current is applied. A planar coil is used.
[0048]
The electric element in claim 1 generically refers to a drive coil, a detection coil, an electric wiring, an electrode pad, and the like.
[0049]
(Operation and Effect) This optical scanner is a one-dimensional optical scanner that can be torsionally vibrated, has a simple configuration, and is easy to manufacture. By using an insulating elastic film for the leaf spring portion, brittle fracture is less likely to occur than when silicon is used for the vibration member, and a large deflection angle can be obtained while maintaining the necessary minimum strength. Further, since the electric element is formed inside the insulating elastic film, the electric element hardly deteriorates due to moisture, and the elastic film can be used for insulation between the electric elements.
[0050]
(2) The optical scanner according to claim 1, wherein the permanent magnet is composed of at least two permanent magnets respectively disposed in the vicinity of opposing side wall surfaces of the movable plate.
[0051]
(Corresponding Embodiment of the Invention) The embodiment relating to this invention corresponds to the first embodiment.
[0052]
(Operation and Effect) A larger deflection angle can be realized by arranging magnets in the vicinity of both side wall surfaces of the movable plate.
[0053]
(3) The optical scanner according to claim 2, wherein the at least two permanent magnets are connected by a yoke.
[0054]
(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to a modification of the first embodiment.
[0055]
(Function, Effect) This optical scanner connects the two magnets arranged near the wall surfaces on both sides with a yoke, thereby making the magnetic field distribution in the vicinity of the drive coil affecting the drive force generated in the drive coil ideal. Unlike the case where no yoke is used, the magnetic field concentrates in the vicinity of the drive coil, so that the drive force can be efficiently converted.
[0056]
(4) The optical scanner according to claim 1, wherein the insulating elastic film is made of an organic film.
[0057]
(Corresponding Embodiment of the Invention) The embodiment relating to this invention corresponds to the first embodiment.
[0058]
(Effect) By using an organic film for the leaf spring portion, brittle fracture is less likely to occur than when silicon or the like is used for the vibration member, and a large deflection angle can be obtained while maintaining the necessary minimum strength.
[0059]
(5) The drive coil is formed so that the width of the wiring of the drive coil and the interval between the wirings are minimized in the vicinity of the permanent magnet. The optical scanner described.
[0060]
(Corresponding Embodiment of the Invention) The embodiment relating to this invention corresponds to the first embodiment.
[0061]
(Function and effect) The coil wiring near the permanent magnet can be brought closer to the permanent magnet by narrowing the interval of the coil wiring that contributes to generation of the force formed in the vicinity of the permanent magnet and narrowing the width of the wiring. A generative force larger than that of the coil can be obtained. The problem of heat generated by narrowing the coil wiring width can be minimized by sufficiently taking the width of the coil wiring in a portion that does not contribute to the generation of force. In addition, the yield in manufacturing can be improved by increasing the distance between the coil wirings in the portion that does not contribute to the generation of force.
[0062]
【The invention's effect】
As described above in detail, according to the present invention, an optical scanner having an electrical element exhibiting high durability can be provided in an optical scanner that vibrates with a large deflection angle.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an optical scanner according to a first embodiment of the present invention.
2 is a cross-sectional view taken along the line AA ′ in the perspective view of the first embodiment shown in FIG. 1. FIG.
3 is a cross-sectional view taken along the line BB ′ of the perspective view in the first embodiment shown in FIG. 1. FIG.
FIG. 4 is a plan view showing a configuration of a drive coil in the first embodiment.
FIG. 5 is a cross-sectional view showing a manufacturing process of the optical scanner according to the first embodiment.
FIG. 6 is a perspective view showing a configuration of a modification of the optical scanner according to the first embodiment.
7 is a cross-sectional view taken along the line AA ′ of the perspective view of a modification of the first embodiment shown in FIG. 6. FIG.
FIG. 8 is a cross-sectional view taken along the line BB ′ of the perspective view of the modification of the first embodiment shown in FIG.
FIG. 9 is a diagram showing a configuration of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Movable plate 102 Elastic member 103 Support body 104 Permanent magnet 105 Reflecting surface 106 Driving coil 107 Contact pad 108 Wiring 109 Bonding pad 110 Silicon substrate 111 Silicon nitride film 112 First polyimide layer 113 Second polyimide layer 114 Third polyimide layer 120 York

Claims (5)

A support for fixing to an arbitrary member;
A movable plate, at least one of which is a reflecting surface that reflects light;
Two elastic members connecting the support and the movable plate;
A drive coil formed on the movable plate;
It consists of a permanent magnet arranged in the vicinity of the movable plate so as to have a predetermined interval between the movable plate,
In the optical scanner in which the movable plate vibrates torsionally with the elastic member as a torsion spring by applying an alternating current to the drive coil.
The elastic member is made of only insulating organic elastic layer to have a electric element therein, an optical scanner, characterized by being formed so as to reach over the support and the movable plate above.   The optical scanner according to claim 1, wherein the organic elastic film is formed to extend on the movable plate, and the drive coil is formed inside the organic elastic film. The permanent magnet, the optical scanner according to claim 1 or claim 2, characterized in that it consists of at least two permanent magnets arranged respectively on opposite side walls near the surface of the movable plate. The optical scanner according to claim 3 , wherein the permanent magnet is connected by a yoke. The optical scanner according to any one of claims 1 to 4, characterized in that the distance between the width and the wiring of the wiring of the drive coil in the vicinity of the permanent magnet is formed to be minimized.

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