JP2009258511A - Optical element and optical device - Google Patents

Optical element and optical device Download PDF

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Publication number
JP2009258511A
JP2009258511A JP2008109400A JP2008109400A JP2009258511A JP 2009258511 A JP2009258511 A JP 2009258511A JP 2008109400 A JP2008109400 A JP 2008109400A JP 2008109400 A JP2008109400 A JP 2008109400A JP 2009258511 A JP2009258511 A JP 2009258511A
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cantilever
optical element
substrate
optical
film
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JP2008109400A
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Japanese (ja)
Inventor
Tokuo Fujitsuka
Kanae Murata
Keiichi Shimaoka
敬一 島岡
香苗 村田
徳夫 藤塚
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Toyota Central R&D Labs Inc
株式会社豊田中央研究所
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Priority to JP2008109400A priority Critical patent/JP2009258511A/en
Publication of JP2009258511A publication Critical patent/JP2009258511A/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element and an optical device provided with a cantilever beam having a mirror and high in durability. <P>SOLUTION: The optical device 2 includes optical elements 4 and 6. The optical element 4 includes a substrate 10, a close fitting film 18 and a cantilever beam 30. The cantilever beam 30 has an aluminum film 26 (reflecting surface) formed on a side opposite to the close fitting film 18. The cantilever beam 30 has a bent shape largely separated from the close fitting film 18 by internal stress when no external force acts thereon. When an external force acts between the cantilever beam 30 and the close fitting film 18, a close fitting surface 28 of the cantilever beam 30 can be closely fitted to a close fitting reference plane 20 of the close fitting film 18. The optical element 4 can be switched in advancing direction of optical beam by changing the shape by use of external force. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical element capable of switching the traveling direction of a light beam. The present invention also provides an optical device that provides an image using a plurality of the optical elements.

  Patent Document 1 discloses an optical element that emits and emits a light beam and can switch the traveling direction of the light beam. Furthermore, an optical device (expressed as a two-stable deformable mirror device (DMD device)) in which a plurality of optical elements are arranged is disclosed. The optical element includes a mirror that reflects the light beam (expressed as beam 200), a torsion beam that supports the mirror (expressed as hinge 401), and is installed on the surface of the mirror and is connected to the torsion beam. Thus, a support column (represented as a beam support post 201) for rotatably supporting the mirror and an actuator (represented as electrodes 404 and 405) for switching the direction of the mirror are provided. In this optical element, the traveling direction of the light beam is switched by switching the directivity angle of the mirror by an actuator.

JP-A-5-196880

The optical element and the DMD device are used in, for example, a dark field projection optical device (so-called projector) and a high-definition television device (HDTV). Although the above optical element and DMD apparatus are extremely useful, it has been found that there is a problem in durability.
There is a strong demand to obtain a bright image, and in order to obtain a bright image, it is necessary to use an imaging lens having a large aperture. In order to switch between a state in which a light beam is incident on a large-diameter imaging lens and a state in which the light beam is not incident, it is necessary to largely change the traveling direction of the light beam by an optical element. That is, in order to obtain a bright image, it is necessary to rotate the mirror greatly. In order to rotate the mirror greatly, it is necessary to largely twist the torsion beam that supports the mirror. When the DMD apparatus is used, the torsion beam repeatedly deforms greatly, so that the torsion beam is fatigued and easily deformed. The optical element and optical device of Patent Document 1 are still unsatisfactory in durability.

  The present invention provides a highly durable optical element and optical device.

The present invention provides an optical element that switches the traveling direction of a light beam. The optical element of the present invention includes a substrate, a cantilever beam, and an actuator. The substrate has an adhesion reference surface with which the cantilever can be adhered. The cantilever has the following properties. That is, it has a plate shape, one end of the plate shape is fixed to the substrate, and the surface opposite to the substrate is a reflection surface that reflects the light beam. In a state where no external force is applied to the cantilever, the bent shape is bent at two or more locations in a direction far away from the contact reference surface as the cantilever is moved away from one end fixed to the substrate. In addition, when an external force is applied, the cantilever is flexible enough to come into close contact with the reference surface for contact. The actuator is installed between the substrate and the cantilever. The actuator generates a suction force that brings the cantilever into close contact with the reference surface for contact between the substrate and the cantilever.
The cantilever is only required to be bent at at least two places, and the bending points may be continuously distributed. That is, the cantilever may be smoothly curved.

According to the optical element described above, the shape of the cantilever can be switched by the actuator. In other words, it is possible to switch between a reference shape that closely contacts the reference surface for contact and a bent shape that is bent away from the reference surface for contact. As a result, the reflective surface of the cantilever can be switched between a reference shape that closely contacts the reference surface for contact and a bent shape that is separated from the reference surface for contact, and the directivity direction of the reflective surface can be switched. The reflection direction of the light beam can be switched.
The cantilever of the present invention is bent at at least two locations. The cantilever of the present invention changes the directivity direction of the reflecting surface by being deformed at two or more locations. Even if the amount of deformation at each bending point is small, the result of accumulation of the small amount of deformation becomes the amount of change in the directivity direction of the reflecting surface. The directivity direction of the reflecting surface can be greatly changed while avoiding local large deformation.
The optical element of the present invention can greatly change the directivity direction of the reflecting surface while being a small amount of deformation when observed in the portion of the constituent member. The durability of the optical element that greatly changes the traveling direction of the light beam is enhanced.

In order to greatly deform the cantilever beam with a small driving force, it is preferable that the flexibility in the vicinity of one end (base portion) fixed to the substrate is high.
Therefore, the width of the cantilever measured in the direction perpendicular to the direction in which the cantilever is extended is narrow near one end (base) fixed to the substrate, and the remaining part of the cantilever (tip) Then, it is preferable that it is wide.

In this case, since the base portion is narrow and flexible, the cantilever is greatly deformed with a small driving force.
When the cantilever is brought into close contact with the reference surface for contact, the cantilever is brought into close contact with the reference surface for contact one after another from the vicinity of one end (base portion) fixed to the substrate. In this case, the distance from the contact reference surface to the cantilever at the next contact portion with the contact reference surface is short. That is, it is only necessary to generate a suction force that sucks a cantilever beam located at a very close position. The suction force required to suck a nearby object may be smaller than the suction force required to suck a remote object. The optical element of the present invention can be operated with a small driving force. If the base portion is narrow and flexible, the power for driving the optical element can be further reduced.

When a cantilever beam bent at two or more locations is brought into close contact with the reference surface for contact, the direction of the reflective surface changes greatly at the part away from the support point of the cantilever beam, whereas the support of the cantilever beam is supported. In the vicinity of the point, the change angle of the directivity direction of the reflecting surface is small.
For example, an application in which a light receiving element is placed on the optical path of a light beam that is reflected while the cantilever is in close contact with the reference surface for contact, and the optical element actuator switches whether the light receiving element receives the light beam or not. Suppose. In this case, although the cantilever has a bent shape, the amount of light received by the light receiving element becomes noise. In order to reduce the noise, it is advantageous to reduce the amount of light received by the light receiving element even though the cantilever has a bent shape.
If the width of the cantilever in the vicinity of one end (base) where the cantilever is fixed to the substrate is narrow, the amount of light that becomes noise, that is, the amount of light reflected at the base of the cantilever with a small angle change It can also be reduced.

In order to reduce noise, in addition to narrowing the width of the base of the cantilever, the reflective surface of the cantilever is within the range excluding the vicinity of one end where the cantilever is fixed to the substrate. It is advantageous to form a high reflectivity film.
In this case, the portion where the directivity direction of the reflecting surface changes greatly is selected to form a high reflectivity film, and the amount of light reflected at the base of the cantilever beam with a small posture change is relatively reduced. Can do.

  When the cantilever and the reference surface for contact are in close contact with each other, there is a concern that the surfaces stick to each other even if the external force is released. That is, even if the actuator is turned off and the external force is stopped, the cantilever may not return to the bent shape.

Therefore, it is effective to form a projection group on at least one of the surfaces that are in close contact with each other. In this case, a projection group may be formed on the side of the substrate that is in close contact with the reference surface. Or you may form a projection group in the surface of the side of the cantilever closely_contact | adhered to the reference surface for contact | adherence. Or you may form a projection group in both surfaces.
When the projection group is formed, it is possible to prevent the substrate and the cantilever from sticking to each other in close contact with each other.

It is also useful to adjust the positional relationship between the light source and the optical element in order to reduce the amount of light that is reflected at the base portion where the change angle of the directivity direction of the reflecting surface is small and becomes noise. In other words, if the light source and the optical element are arranged in such a positional relationship that the light beam reflected near one end (base portion) of the bent cantilever is reflected again at the tip end side of the cantilever. The amount of light that is reflected at the base and becomes noise can be reduced.
Alternatively, it is also effective to fix a plane mirror on the tip side of the cantilever. In this case, the change angle at the tip end of the cantilever where the directing direction greatly changes can be obtained over the entire plane mirror. The whole light beam reflected by the plane mirror is greatly changed all at once.
This reflector can be fixed so as to protrude beyond the tip of the cantilever, so that the light beam does not reach the base of the adjacent cantilever. Therefore, it is possible to reduce the amount of light that is reflected by the base portion of the adjacent cantilever with a small angle change and becomes noise.

The present invention also provides an optical device using the above optical element. In this optical apparatus, a plurality of optical elements are arranged one-dimensionally or two-dimensionally. Furthermore, the actuators of the individual optical elements can be controlled independently of the adjacent actuators. According to this, the reflection direction of the light beam can be controlled for each optical element. For example, it is possible to control whether or not the reflected light is incident on the imaging lens for each optical element, and the image appearing in the image can be controlled.
The optical device described above can be used for the imaging optical system as described above. In this case, the reflected light from the cantilever that is in close contact with the contact reference surface is incident on the imaging system lens, and the reflected light from the cantilever that is bent away from the contact reference surface is reflected into the imaging system lens. So that it is not incident on. Then, an image in which only the reflected light from the cantilever beam that is in close contact with the reference surface for contact is formed is provided. Controlling the image that appears in the image by selecting the optical element that makes the cantilever closely contact the reference surface for contact and the optical element that makes the cantilever separate from the reference surface for contact. Can do.

  In the above optical device, it is preferable that the area of the reflecting surface per unit area is large and noise is small. If the area of the reflecting surface per unit area is large, the amount of light incident on the optical device can be used effectively, and if the noise is small, an image with high contrast can be obtained.

In the case of an optical device in which a plurality of optical elements are arranged along the direction in which the cantilever is extended, the vicinity of one end where the cantilever is fixed to the substrate is divided into two pieces extending in parallel with an interval. It is preferable that the cantilever beam of the optical element adjacent to the interval between the two pieces penetrates.
According to this configuration, the base portion that causes noise is narrowed by the interval, and the amount of reflected light that causes noise is reduced. In addition, the interval becomes a reflective surface of another cantilever beam whose direction of directivity changes greatly. It is possible to suppress the reduction of the reflection area while reducing the noise by reducing the width of the reflection surface at the base portion that causes noise.

According to the present invention, the reflection direction of the light beam is switched by bringing the cantilever bent in at least two places in the natural shape into close contact with the reference surface for contact. Even if the amount of deformation at each inflection point is small, the accumulated direction can greatly change the directivity direction of the reflecting surface. Since the deformation amount of each point is small, the durability is high, and the reflection direction can be greatly changed.
When a suction force acts on the cantilever, the cantilever is brought into close contact with the substrate from the base. If a suction force sufficient to suck an object located at a very close position is generated, the cantilever beam comes into close contact with the substrate, so that a very small driving force is required for switching the reflection direction. Power consumption can be kept low.
Further, the cantilever can be easily manufactured and can be manufactured at low cost.
The optical elements of the present invention can be arranged with high density, and provide an optical device with high light reflection efficiency.
In addition, it is easy to take measures to reduce noise.

The main features of the embodiment described below are organized.
(Feature 1) A plurality of optical elements can be simultaneously manufactured using a silicon substrate.
(Feature 2) An optical device in which a plurality of optical elements are arranged using a silicon substrate can be manufactured.
(Characteristic 3) The cantilever has a curved shape in a direction away from the contact reference surface due to internal stress when no external force is applied. In the manufacturing process of the cantilever, a condition that generates an internal stress that curves in the above direction is adopted. Specifically, an amorphous silicon layer is formed on the single crystal silicon layer, the amorphous silicon layer is changed to a polycrystalline silicon layer, and then the single crystal silicon layer is removed. Then, the polycrystalline silicon layer is curved.
(Characteristic 4) An electrode is installed on each of the cantilever and the contact substrate, and both are brought into close contact with each other by applying a voltage.

(First embodiment)
FIG. 1 shows a longitudinal sectional view of a part of the optical device 2 of the first embodiment. The optical apparatus 2 is configured by two-dimensionally arranging a plurality of optical elements. FIG. 1 is a cross-sectional view of a portion where two optical elements 4 and 6 are arranged. FIG. 2 shows a plan view of the same portion as FIG. The optical elements 4 and 6 have the same configuration. Below, the structure of the optical element 4 is demonstrated.
The optical element 4 includes a substrate 10, a cantilever 30, and an actuator 60.
The optical elements 4 and 6 are formed on the silicon substrate 11. The silicon substrate 11 is covered with a silicon oxide film 12. An adhesion film 18 is formed on the surface of the silicon oxide film 12. The adhesion film 18 includes a polysilicon film 14 fixed to the silicon substrate 11 through the silicon oxide film 12 and a silicon oxide film 16 covering the periphery of the polysilicon film 14. A polysilicon film 22a extending vertically upward from the surface of the silicon oxide film 12 is formed, and connected to a polysilicon film 22b extending from the upper end of the polysilicon film 22a toward the upper right in the drawing. The surfaces of the polysilicon film 22a and the polysilicon film 22b are covered with silicon oxide films 24a and 24b. An aluminum film 26 is formed on the upper surface of the silicon oxide film 24b.
FIG. 1 shows a state in which no external force acts on the polysilicon film 22b, and the polysilicon film 22b is bent in a direction far away from the adhesion film 18 as it moves away from one end fixed to the polysilicon film 22a. ing.
The substrate 10 of the optical element 4 includes a silicon substrate 11, a silicon oxide film 12, a polysilicon film 22a, and a silicon oxide film 24a. An adhesion film 18 composed of the polysilicon film 14 and the silicon oxide film 16 also constitutes a part of the substrate 10.
The cantilever 30 of the optical element 4 is formed of a polysilicon film 22b, a silicon oxide film 24b, and an aluminum film 26. The cantilever 30 has a thin plate shape, and one end of the plate is fixed to the substrate 10 (in FIG. 1, the boundary where the cantilever 30 and the substrate 10 are fixed is indicated by line A). The upper surface of the cantilever 30, that is, the surface opposite to the substrate 10 is a highly reflective aluminum surface, which is a reflective surface that reflects a light beam to be described later.
The actuator 60 of the optical element 4 is formed of the polysilicon film 14 on the substrate 10 side and the aluminum film 26 on the cantilever 30 side, and when a positive / negative potential difference is given between the polysilicon film 14 and the aluminum film 26. The cantilever 30 is sucked toward the substrate 10 so that the cantilever 30 is in close contact with the adhesion film 18. The upper surface of the silicon oxide film 16 of the adhesion film 18 is a flat surface, and constitutes an adhesion reference plane 20. The actuator 60 is provided between the substrate 10 and the cantilever 30, and a suction force for bringing the lower surface 28 of the cantilever 30 into close contact with the contact reference plane 20 is provided between the substrate 10 and the cantilever 30. To generate.
The adhesion film 18 and the cantilever 30 are insulated.

  When no external force is applied, the cantilever beam 30 has a curved shape that is largely separated from the adhesion film 18 as the distance from the fixing portion A fixed to the substrate 10 increases. The cantilever 30 has a curved shape due to the internal stress of the polysilicon film 22b. The reason why the internal stress occurs will be described in detail later. On the other hand, when an external force such as electrostatic attraction is applied between the cantilever 30 and the adhesion film 18, the adhesion surface 28 of the cantilever 30 is brought into close contact with the adhesion reference plane 20 of the adhesion film 18. be able to. The cantilever 30 is flexible enough to be extended from a curved shape to a planar shape that is in close contact with the reference plane 20 for close contact.

  Since the polysilicon film 14 is covered with the silicon oxide film 16, it is insulated from the aluminum film 26. The polysilicon film 14 is conductive and can be used for one of the electrodes. Further, the aluminum film 26 formed on the upper portion of the cantilever 30 can be used for the other electrode. For example, when a positive voltage is applied to the polysilicon film 14 and a negative voltage is applied to the aluminum film 26, electrostatic attraction acts between them, and the cantilever 30 is attracted to the adhesion film 18. 4 shows a case where a positive voltage is applied to the polysilicon film 14 of the optical element 4 and a negative voltage is applied to the aluminum film 26. The cantilever 30 is attracted to the polysilicon film 14. It is in close contact with the reference plane 20 for close contact.

Further, when the cantilever 30 is brought into close contact with the adhesion film 18, the cantilever 30 is deformed in the order shown in FIG. Initially, as shown in (1), the points 34 and 36 are in close contact. The distance between the point 34 and the point 36 in the natural shape is smaller than the distance between the front end point, for example, the point 32 and the point 38. The suction force required to suck a cantilever beam at a short distance may be smaller than the suction force required to suck a cantilever beam at a far distance.
When the point 34 and the point 36 are in close contact with each other, the adsorption proceeds at the right side portion thereafter. The right side part to be newly adsorbed is sufficiently close when the points 34 and 36 are adsorbed, and is adsorbed with a small suction force. If the suction force required to change from (1) to (2) is small, the suction force required to change from (2) to (3) can be small.
The cantilever 30 has a sufficiently small force so that the suction point advances from the root to the tip. The optical element 4 can be changed from a state in which the cantilever 30 has a natural shape to a shape in close contact with the reference plane for contact 20 with a small suction force. The power consumption of the optical element 4 can be suppressed.
The cantilever 30 naturally returns to a curved shape due to internal stress when the external force is released. That is, it is not necessary to apply an external force when deforming from a state stretched to a planar shape to a curved shape. This can also reduce power consumption.
Further, when FIG. 1 is compared with FIG. 4, the inclination angle at the tip of the aluminum film 26 changes by θ. The value of θ is sufficiently large, and the traveling direction of the light beam can be changed greatly. However, in this optical element 4, somewhere is greatly deformed locally and a large rotation angle θ is not realized. A large rotation angle θ is realized by accumulating a phenomenon in which the cantilever beam 30 that is gently curved over the entire length gradually deforms over the entire length. Observing the partial parts, the amount of deformation in each part is small. There is no part that is greatly distorted when switching the reflection direction of the light beam, and the rate at which fatigue accumulates due to repeated strain is slow. The durability of the optical element 4 is high.
In the above description, an infinite number of inflection points are described, but the number of inflection points may be two or more. When a cantilever beam having a polygonal line shape that is bent at two or more locations is used when observed in a longitudinal section, it is possible to obtain a phenomenon in which deformation at each bending point is accumulated and the tip is greatly deformed.

  The base of the cantilever 30 is preferably more flexible than the rest. When the base portion is deformed with a small suction force, the driving force required to change the cantilever 30 from the natural shape to the shape closely contacting the contact reference plane 20 can be further reduced, and the power consumption of the optical element 4 can be further reduced. Can be suppressed.

  In FIG. 2, the figure which looked at the cantilever 30 from the top is shown. The base portion 42 of the cantilever 30 is divided into two pieces, and an interval M is formed between them. When measured along the direction B perpendicular to the direction C in which the cantilever 30 extends, the width (W1 + W2) at the base portion 42 is larger than the width W3 at the tip portion 40 by the distance M is formed. It is narrower. The base portion 42 having a narrow width is extremely flexible and can be greatly deformed with a small suction force. In the optical element 4, since the base portion 42 of the cantilever 30 is flexible, a large angle change can be realized in the distal end portion 40 with a small suction force. Another effect of the structure of FIG. 2 will be described later.

FIG. 4 shows an optical path when the light beams 100 and 120 are incident on the optical elements 4 and 6.
In the optical element 4, a positive voltage is applied to the polysilicon film 14 and a negative voltage is applied to the aluminum film 26, and the tip 40 of the cantilever 30 is in close contact with the adhesion film 18 and is stretched to a planar shape. The reflecting surface of the aluminum film 26 becomes a plane mirror, and the light beam 100 is reflected by the plane mirror. The light beam 100 reflected by the plane mirror enters the imaging lens 102 and becomes a bright point at the position 108 of the screen 104. Here, the position 108 is a position on the screen corresponding to the optical element 4.

  On the other hand, in the optical element 6, no voltage is applied between the polysilicon film 14 and the aluminum film 26, and the cantilever 30 is curved away from the adhesion film 18. The reflecting surface of the aluminum film 26 is a curved mirror, and is directed to the upper left. For this reason, the light beam 120 reflected by the aluminum film 26 of the optical element 6 does not enter the imaging lens 102. For this reason, it becomes a dark spot at the position 106 of the screen 104. Here, the position 106 is a position on the screen corresponding to the optical element 6.

  In the optical device 2, the actuators of the individual optical elements can be controlled independently from the actuators of the adjacent optical elements. Specifically, when a voltage is applied to the optical element 4, the voltage can be applied to the optical element 6 or not. Thereby, the optical device 2 can freely control the image appearing on the screen 104.

  In this specification, the ON state and OFF state of the optical element 4 are defined as follows. The ON state means a state in which an image is formed on a screen when a light beam is reflected by the optical element 4. The OFF state refers to a state in which when the light beam is reflected by the optical element 4, the optical path is shifted from the imaging lens 102 and an image cannot be formed. In this embodiment, the state in which the cantilever 30 is brought into close contact with the contact film 18 by applying an external force is the ON state. Moreover, the state where the cantilever 30 is curved without applying an external force is the OFF state.

  Here, noise that occurs during image formation will be described. The noise is a state in which a part of light enters the imaging lens 102 and an unintended bright point is imaged on the screen 104 even though the cantilever 30 is in the OFF state. FIG. 5 illustrates the reason why noise occurs. FIG. 5A shows the optical element 4 in the ON state. FIG. 5B shows the optical element 4 in the OFF state. In FIG. 5A, the light beams 100, 120, and 130 are reflected by an aluminum surface having a shape close to a planar shape (near point 60) or an aluminum surface having a planar shape (near points 62 and 64). The light enters the imaging lens 102 and forms an image. This is an ideal optical path in the ON state.

  On the other hand, in FIG. 5B, since the angle change is small at the base of the cantilever 30 even though it is in the OFF state, the light is reflected in the vicinity of the base (near points 66 and 68). The light beams 100 and 120 are incident on the imaging lens 102. That is, noise is generated. On the other hand, the light beam 130 reflected at the tip (near the point 69) does not enter the imaging lens 102. If more light beams can be reflected at the tip with a large angle change, noise can be reduced and a bright image can be obtained.

As shown in FIG. 2, in the optical element 4, the width of the base portion 42 of the cantilever 30 is narrow. As a result, the following two effects can be obtained.
(1) Since the area of the base portion 42 is small, reflection of the light beam at the base portion can be reduced. In other words, noise can be reduced because more light beams can be reflected by the tip 40 having a large angle change.
(2) The base portion 42 is divided into two pieces, and when a plurality of optical elements are arranged, the tip portions of adjacent optical elements are inserted into the interval M between the base portions 42 as in the embodiments described later. Can be arranged as follows. By arranging the optical elements at a high density, the occupied area ratio of the distal end portion 40 can be increased and a bright image can be obtained.
If the area of the base 42 is reduced, the aluminum film 26 may be formed on the entire surface of the cantilever 30. By simply reducing the area of the base portion 42, the amount of reflection of the light beam at the base portion can be reduced. However, as shown in FIG. 2, it is preferable not to form the aluminum film 26 at the base of the cantilever 30. In that case, the amount of reflection of the light beam at the base can be further reduced.
When the aluminum film 26 is not formed on the base of the cantilever 30, it is not always necessary to reduce the area of the base 42. Even if the area of the base portion 42 is not reduced, noise can be reduced.

6 to 16 show a manufacturing process of the optical elements 4 and 6.
FIG. 6 shows a stage where the silicon substrate 11 is prepared.
FIG. 7 shows a stage in which the silicon substrate 11 is thermally oxidized to form a silicon oxide film 12.
FIG. 8 shows a stage in which the polysilicon film 14 is patterned after the polysilicon film 14 is formed and ions are implanted to impart conductivity.
FIG. 9 shows a stage where the silicon oxide film 16 is formed. The polysilicon film 14 on which the silicon oxide film 16 is formed is used as an adhesion film 18.
FIG. 10 shows a stage where the silicon sacrificial layer 17 is formed and patterned. At this time, the silicon sacrificial layer 17 is patterned so as to cover the adhesion film 18 and to be longer than the tip of the cantilever 30 to be manufactured in a later step.
FIG. 11 shows a stage where the silicon oxide film 24c is formed and patterned.
FIG. 12 shows a stage where a polysilicon film 22 is formed and ions are implanted and then patterned. At this time, the polysilicon film 22 is patterned so as to cover a part of the formed sacrificial layer 17 and the tip of the polysilicon film 22 is shorter than the tip of the sacrificial layer 17 manufactured in FIG. To do.
In this step, the internal stress of the cantilever 30 is controlled. As a result, the cantilever 30 can have a curved structure with the external force released as shown in FIG. An example of the film forming conditions in FIG.
(1) Using LPCVD (low pressure chemical vapor deposition) method, under conditions where the film forming temperature is 520 ° C., the flow rate of Si 2 H 6 is 300 sccm, 6 Pa, the film forming rate is 100 Km / min, and the film pressure is 2000 Km. Then, an amorphous silicon film is formed.
(2) Crystallization annealing is performed on the amorphous silicon film formed in (1) above under the conditions of a temperature of 1000 ° C., an N 2 flow rate of 10 L / min, and a time of 60 min.
(3) Ion implantation is carried out under the conditions that the ions are P, the acceleration energy is 80 keV, and the dose is 1 × 10 16 / cm 2 .
(4) Activation annealing is performed under conditions where the temperature is 1000 ° C., the gas is N 2 , the N 2 flow rate is 10 L / min, and the time is 60 min.
FIG. 13 shows a stage where a silicon oxide film 24d is formed and patterned.
FIG. 14 shows a stage where an aluminum film 26 is formed and patterned. This aluminum film becomes the reflective surface of the cantilever 30.
FIG. 15 shows a stage in which a hole is formed in 24e which is a part of the silicon oxide film to form an etching hole.
FIG. 16 shows the stage where the silicon sacrificial layer 17 has been etched and the right end of the cantilever 30 has been released. If the film forming process of the polysilicon film 22 shown in FIG. 12 is performed under the above conditions (1) to (4), the polysilicon film 22 is subjected to compressive stress on the lower surface of the polysilicon film 22. 22 is formed. Therefore, when the silicon sacrificial layer 17 is removed, the cause of compressing the lower surface of the polysilicon film 22 disappears, and the lower surface of the polysilicon film 22 expands. As a result, when the silicon sacrificial layer 17 is removed, the polysilicon film 22 is curved upward. The optical element shown in FIG. 16 is completed.

  In order to form the cantilever 30 of the optical element 4, it is not necessary to form the thick silicon sacrificial layer 17 under the cantilever 30. In order to increase the rotation angle of the mirror with the technique of Patent Document 1, it is necessary to form a thick sacrificial layer and etch the thick sacrificial layer, which increases the manufacturing cost. With the optical element of this embodiment, it is not necessary to form a thick sacrificial layer and etch the thick sacrificial layer, and the manufacturing cost can be reduced.

  In addition, said film-forming conditions are an example and a manufacturing process is not limited above. For example, in FIG. 12 described above, the polysilicon film 22 of the cantilever 30 is a single layer film, but may be a multilayer film in which a film having a stronger tensile stress is laminated on the upper side. In FIG. 15, the aluminum film 26 is formed as the reflective film, but a film other than the aluminum film having a high reflective film may be used. Further, a film having a high reflectance such as an aluminum film may be attached to the upper portion of the cantilever 30. Alternatively, the upper surface of the silicon oxide film 24d may be used as a reflection surface as it is.

  According to the optical device 2 of the present embodiment, by using the optical element 4 having the cantilever 30, the traveling direction of the light beam can be controlled and the image appearing on the screen 104 can be controlled. By narrowing the width of the base portion of the cantilever 30, a large angle change can be applied with a small driving force, and durability and cost reduction can be realized. Furthermore, by reducing the width of the base portion of the cantilever beam 30 that is likely to generate noise, an image with high contrast can be acquired. In addition, with the structure divided into two pieces at the base of the cantilever, optical elements can be arranged at high density, the area of the reflecting surface can be increased, and a bright image can be acquired.

  The optical element of this embodiment can control the image appearing on the screen by arranging a plurality of optical elements in one or two dimensions. For example, if each optical element is one pixel, 800 × 600 optical elements can be arranged to form an image having a resolution of SVGA (Super Video Graphics Array).

(Second embodiment)
FIG. 17 shows an optical element of the second embodiment. The cantilever 30 according to the second embodiment includes a projection group 500 including projections 50, 52, 54, 56 and 58 on the contact surface 28. Thereby, even if the external force is released, the contact surface 28 can be prevented from sticking to the contact reference surface 20. The protrusion group 500 may be formed on the adhesion film 18 side.

(Third embodiment)
18 and 19 show an optical element of the third embodiment. In the optical elements of FIGS. 18 and 19, a flat mirror 74 is fixed to the upper surface of the cantilever 30 via a support portion 72. The support part 72 is provided at the tip of the cantilever 30. The flat mirror 74 is fixed so as to protrude beyond the tip of the cantilever 30. Further, the flat mirror 74 extends until it covers a part of the base of the cantilever 30 of the adjacent optical element. 18 shows an ON state and FIG. 19 shows an OFF state, and the angle of the flat mirror 74 changes with the cantilever 30.
In the ON state shown in FIG. 18, the flat mirror 74 takes a horizontal posture. That is, the light beams 100 and 120 reflected on the flat mirror 74 are reflected at the same reflection angle as that of the optical element 4 (ON state) in FIG. 4 and enter the imaging lens 102 to form an image.
In the OFF state shown in FIG. 19, a change angle that greatly changes the reflection direction of the light beam is obtained over the entire flat mirror 74. That is, the light beams 100, 120, and 130 are reflected at the same reflection angle and do not enter the imaging lens 102. The portion of the flat mirror 74 that protrudes beyond the tip of the cantilever can block the light beam 120a that should have reached the root of the adjacent cantilever. It should be noted that the protruding length of the portion of the flat mirror 74 that protrudes beyond the tip of the cantilever 30 depends on the base of the adjacent cantilever 30 according to the incident angle of the light beams 100, 120, and 130. It is set so that the light beam 120a does not reach. It is preferable that the portion of the flat mirror 74 that protrudes ahead of the tip of the cantilever extends to cover a part of the base of the cantilever 30 of the adjacent optical element. The above effect can be obtained in a wide range of incident angles of the light beams 100, 120, and 130.
By fixing the flat mirror 74, an image is formed in the same manner as when the flat mirror is not fixed in the ON state (that is, when reflected by the upper surface of the planar cantilever), but the posture changes in the OFF state. It is possible to inhibit the reflection of the light beam at the base portion having a small height and reduce noise. Moreover, since the space | interval with the flat mirror 74 of an adjacent optical element can be made small by the flat mirror 74, an effective reflective area can be enlarged.

(Fourth embodiment)
It is also useful to adjust the positional relationship between the light source and the optical element in order to reduce the amount of light that is reflected at the base portion where the change angle of the directivity direction of the reflecting surface is small and becomes noise. FIG. 20 shows an optical path when the light beam 100 is incident on the optical element in the OFF state. The light beam is reflected at the base portion having a curved shape and reflected again at the tip portion. Since the light beam 100 is finally reflected at the tip portion having a large change angle and the traveling direction is largely switched, it does not enter the imaging lens 102. As a result, the amount of light that is reflected at the base and becomes noise can be reduced.

(5th Example)
In an optical device, it is preferable that noise is small and the effective reflection area per unit area is large. For this purpose, it is also useful to adjust the shape and arrangement method of the cantilever beams. In the fifth embodiment, the shape of the cantilever beam is devised, and the tip portion of the cantilever beam is arranged so as to be inserted into the interval between the base portions divided into two pieces of the adjacent cantilever beam, thereby reducing noise. An optical element capable of reducing and increasing an effective reflection area is provided.

  FIGS. 21 to 24 show the optical elements as seen from above. All adjacent optical elements have the same structure. FIG. 21 shows a state in which the optical elements 140, 160 and 180 are adjacent to each other. In the optical element 160, the gap M160 between the base portions divided into two pieces is widened to a width that allows the tip portion of the cantilever to be inserted (that is, M160> W3). As a result, it is possible to arrange the tip portions of the adjacent optical elements 140 to be inserted in the gap M160. That is, it is possible to use the interval between the base portions as an effective reflection area while reducing the noise by reducing the reflection surface of the base portion that causes noise.

  FIG. 22 shows a state in which the optical elements 240, 260, and 280 are adjacent to each other. In the optical element 260, the width of the tip portion of the cantilever has two stages, and the width W3-260 of the tip portion on the tip side from the positions 262 and 268 of the tip portion can be inserted into the interval M between the root portions. It is narrowed to the width (ie, M> W3-260). As a result, the distal end portion of the optical element 260 having the width W3-260 can be arranged so as to be inserted into the interval M between the base portions of the adjacent optical elements 280. That is, it is possible to use the interval between the base portions as an effective reflection area while reducing the noise by reducing the reflection surface of the base portion that causes noise.

  FIG. 23 shows a state in which the optical elements 340, 360, and 380 are adjacent to each other. In the optical element 360, the interval between the base portions divided into two pieces is expanded in two stages, and the interval M360-1 on the base side from the positions 364 and 366 of the base portions is wider than the interval M360-2. The interval M360-2 is widened so that the tip end portion (width W3) of the cantilever can be inserted (that is, M360-2> W3). The interval M360-1 is widened so that the base of the width (W1 + W2 + M360-2) can be inserted (that is, M360-1> (W1 + W2 + M360-2)). Accordingly, a part of the base portion and the tip end portion of the optical element 340 can be arranged so as to be inserted into the interval of the optical element 360. That is, it is possible to use the interval between the base portions as an effective reflection area while reducing the noise by reducing the reflection surface of the base portion that causes noise. Further, by inserting the base portion of the adjacent optical element into the interval between the base portions, the length of the base portion in the direction orthogonal to the interval M360-1 can be increased. As a result, the number of bending points at the narrow and flexible base portion can be increased, and the tip portion can be greatly deformed with a small driving force.

  FIG. 24 shows a state where the optical elements 440, 460, and 480 are adjacent to each other. In the optical element 460, the width of the tip portion of the cantilever is in two stages, and the width W3-460 of the tip portion closer to the tip side than the positions 462 and 468 of the tip portion can be inserted into the interval M between the root portions. It is narrowed to the width (ie, M> W3-460). Furthermore, the width of the interval M between the bases is increased from the middle of the base (positions 464 and 466) toward the base of the base. The base portion interval M460 is wide enough to insert the tip portion of the width W and the base portion (W = W1 + W2 + M) (that is, M460> (W1 + W2 + M)). Accordingly, a part of the base portion and the tip end portion of the optical element 440 can be arranged so as to be inserted into the interval of the optical element 460. Further, by inserting the base portion of the adjacent optical element into the interval between the base portions, the length of the base portion in the direction orthogonal to the interval M can be increased. As a result, the number of bending points at the narrow and flexible base portion can be increased, and the tip portion can be greatly deformed with a small driving force.

  In the fifth embodiment, by reducing the width of the base portion and reducing the area, the amount of reflected light of the light beam at the base portion can be reduced and noise can be reduced. In addition, the tip of another cantilever is inserted into the space between the base parts divided into two pieces, and the reflection surface of the other cantilever whose directing direction changes greatly is used as an effective reflection area. be able to. Further, by inserting a part of the base portion in addition to the tip portion of the adjacent optical element into the interval between the base portions, the length of the base portion in the direction orthogonal to the interval M can be increased. As a result, the number of bending points at the narrow and flexible base portion can be increased, and the tip portion can be greatly deformed with a small driving force.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, the reference surface for contact is not necessarily a flat surface, and may be a curved surface that matches the characteristics of an optical system that uses light from the optical device.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

Sectional drawing of the optical element of 1st Example is shown. The top view of the optical element of 1st Example is shown. An operation principle of the optical element of the first embodiment is schematically shown. An operation principle of the optical element of the first embodiment is schematically shown. An operation principle of the optical element of the first embodiment is schematically shown. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. The manufacturing process of the optical element of 1st Example is shown in steps. Sectional drawing of the optical element of 2nd Example is shown. An operation principle of the optical element of the third embodiment is schematically shown. The operation principle of the optical element of the third embodiment is schematically shown. An operation principle of the optical element of the fourth embodiment is schematically shown. The top view of the optical element of 5th Example is shown. The top view of the optical element of 5th Example is shown. The top view of the optical element of 5th Example is shown. The top view of the optical element of 5th Example is shown.

Explanation of symbols

2: optical device 4, 6: optical element 10: substrate 18: adhesion film 20: adhesion reference plane 28: adhesion surface 30: cantilever 26: aluminum films 100, 120, 130: light beam 102: imaging lens 104: Screen

Claims (8)

  1. An optical element that switches the traveling direction of the light beam,
    A substrate having a reference surface for adhesion;
    It has a plate shape, one end of the plate shape is fixed to the substrate, the surface opposite to the substrate is a reflective surface that reflects a light beam, and is fixed to the substrate in a state where no external force is applied. A cantilever beam that has a bent shape that is bent at two or more locations in a direction that is far away from the reference surface for contact as it moves away from one end, and that has a flexibility to closely contact the reference surface when an external force is applied When,
    An actuator that is provided between the substrate and the cantilever, and that generates a suction force between the substrate and the cantilever to bring the cantilever into close contact with the contact reference surface;
    An optical element comprising:
  2.   The width of the cantilever beam measured in a direction perpendicular to the direction in which the cantilever beam extends is narrower than the remaining portion in the vicinity of one end where the cantilever beam is fixed to the substrate. Item 2. The optical element according to Item 1.
  3.   3. The high reflectivity film is formed in a range excluding the vicinity of one end where the cantilever is fixed to the substrate in the reflective surface of the cantilever. An optical element according to 1.
  4.   The protrusion group is formed on at least one surface of the reference surface for contact and the surface of the cantilever that is in close contact with the reference surface for contact. An optical element according to 1.
  5.   The light beam reflected in the vicinity of one end fixed to the substrate of the cantilever having the bent shape with respect to the light source is disposed in a positional relationship where it is reflected again on the tip side of the cantilever. The optical element according to any one of claims 1 to 4, wherein the optical element is formed.
  6.   The optical element according to any one of claims 1 to 4, wherein a flat mirror is fixed to a tip side of the cantilever.
  7. A plurality of the optical elements according to any one of claims 1 to 6 are arranged,
    An optical device characterized in that the actuator of each optical element can be controlled independently from the actuator of an adjacent optical element.
  8. A plurality of optical elements are arranged along the extending direction of the cantilever,
    The vicinity of one end fixed to the substrate of the cantilever is divided into two pieces extending in parallel at an interval,
    8. The optical apparatus according to claim 7, wherein a cantilever beam of an optical element adjacent to the interval between the two pieces enters.
JP2008109400A 2008-04-18 2008-04-18 Optical element and optical device Pending JP2009258511A (en)

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