Source: http://www.google.com/patents/US6900925?dq=6272333
Timestamp: 2016-07-31 10:17:57
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Patent US6900925 - Optical deflector and method of producing same - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThere are provided a small optical deflector that can be driven at a high speed with a low voltage, provides a large angle of deflection, has a low distortion even in high speed operation and has a high static flatness of a reflective surface, and a method of producing the optical deflector. The optical...http://www.google.com/patents/US6900925?utm_source=gb-gplus-sharePatent US6900925 - Optical deflector and method of producing sameAdvanced Patent SearchPublication numberUS6900925 B2Publication typeGrantApplication numberUS 10/608,109Publication dateMay 31, 2005Filing dateJun 30, 2003Priority dateJul 5, 2002Fee statusPaidAlso published asUS7038834, US20040070816, US20050179985Publication number10608109, 608109, US 6900925 B2, US 6900925B2, US-B2-6900925, US6900925 B2, US6900925B2InventorsTakahisa Kato, Takayuki Yagi, Yasuhiro ShimadaOriginal AssigneeCanon Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (15), Referenced by (46), Classifications (17), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetOptical deflector and method of producing same
US 6900925 B2Abstract
There are provided a small optical deflector that can be driven at a high speed with a low voltage, provides a large angle of deflection, has a low distortion even in high speed operation and has a high static flatness of a reflective surface, and a method of producing the optical deflector. The optical deflector drives a movable plate relative to a supporting substrate to deflect a light incident on a reflective surface and has a configuration in which at least two recesses are formed in a surface of the movable plate on which the reflective surface is not formed, and a magnetic material is provided in the recesses.
a supporting substrate having an elastic supporting part; a movable plate having a reflective surface on one side thereof and a magnetic material on another side thereof and supported at both ends thereof by the elastic supporting part so as to be torsionally vibratable around a torsion axis; and magnetism generating means provided in the vicinity of and spaced apart from the magnetic material, for driving the movable plate relative to the supporting substrate to deflect light incident on the reflective surface, wherein the another side of the movable plate has at least two recesses, and the magnetic material is provided in the recesses. 2. The optical deflector according to claim 1, wherein the recesses are spaced apart from the torsion axis of the movable plate and are not close to the torsion axis.
3. The optical deflector according to claim 1, wherein the supporting substrate, the elastic supporting part, the movable plate, and the recesses are integrally formed of single-crystal silicon.
4. The optical deflector according to claim 1, wherein the first side of the movable plate comprises a (100)-equivalent plane of a silicon crystal, and an inner surface of at least one of the recesses comprises a (111)-equivalent plane of a silicon crystal.
5. The optical deflector according to claim 1, wherein the elastic supporting part has an X-shaped cross section.
6. The optical deflector according to claim 1, wherein a side wall of the movable plate has a recess.
7. The optical deflector according to claim 1, wherein the recesses each have a substantially vertical side wall in a cross section taken along a line perpendicular to the direction of a width of the movable plate.
8. The optical deflector according to claim 1, wherein the recesses are each substantially V-shaped in a cross section taken along a line perpendicular to the direction of a width of the movable plate.
9. The optical deflector according to claim 1, wherein a cross section of each of the recesses which is parallel to the second side of the movable plate has a larger area within the movable plate than at a surface of the movable plate.
10. The optical deflector according to claim 1, wherein the magnetic material has a substantially circular cross section taken along a line perpendicular to the direction of a width of the movable plate.
11. The optical deflector according to claim 1, wherein, when viewed from above the surface of the movable plate having the recesses formed therein, the magnetic material overlies the recesses.
12. An optical device, comprising the optical deflector as set forth in claim 1.
13. A display device comprising the optical deflector as set forth in claim 1 and a light source, wherein the optical deflector performs deflection/scanning of light from the light source to form an image on a projection plane.
The present invention has been devised in view of the problems of prior art described above.
a supporting substrate having an elastic supporting part; a movable plate having a reflective surface on one side thereof and a magnetic material on another side thereof and supported at both ends thereof by the elastic supporting part so as to be torsionally vibratable around a torsion axis; and magnetism generating means provided in the vicinity of and spaced apart from the magnetic material, for driving the movable plate relative to the supporting substrate to deflect a light incident on the reflective surface, wherein the another side of the movable plate has at least two recesses, and the magnetic material is provided in the recesses. According to a second aspect of the present invention, there is provided a method of producing an optical deflector having a supporting substrate, an elastic supporting part and a movable plate, comprising the steps of:
preparing a silicon substrate having a first side for formation of a reflective surface and a second side; forming mask layers on the first and the second sides of the silicon substrate; removing the mask layer on the first side except an area thereof for formation of the supporting substrate, elastic supporting part and movable plate; removing the mask layer on the second side except an area thereof for formation of the supporting substrate, elastic supporting part and movable plate and also removing the mask layer on an area for formation of a recess within the area for formation of the movable plate; dipping the silicon substrate in an aqueous alkaline solution to perform anisotropic etching to divide the silicon substrate into the supporting substrate, the elastic supporting part and the movable plate and to form the recess on one side of the movable plate; removing the mask layers on the silicon substrate; forming a reflective film on the first side of the movable plate; and providing a magnetic material in the recess. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an optical deflector according to a first embodiment of the invention;
FIGS. 5A, 5B and 5C are cross-sectional views taken along the lines 5A—5A, 5B—5B and 5C13 5C in FIG. 4, respectively;
FIG. 9 is a cross-sectional view taken along the line 9—9 in FIG. 8;
FIG. 11 is a cross-sectional view taken along the line 11—11 in FIG. 10;
In the following, preferred embodiments of the invention will be described in detail with reference to the drawings.
(Entire Configuration and Mirror (Movable Plate))
FIG. 1 is a perspective view showing a configuration of an optical deflector according to a first embodiment of the invention. In FIG. 1, an optical deflector 1 comprises a supporting substrate 2, a movable plate 6, and elastic supporting parts 3, the movable plate 6 being supported at both ends thereof on the supporting substrate 2 via the elastic supporting parts 3. The elastic supporting parts 3 support the movable plate 6 in such a manner that the movable plate 6 can be elastically and torsionally vibrated about a C axis (that is, a torsion axis) in a direction indicated by the arrow E. One surface of the movable plate 6 is a reflective surface 4 that constitutes a mirror surface, and torsional movement of the movable plate 6 in the E direction provides deflection of a light incident on the reflective surface 4 at a predetermined angle. The direction indicated by the arrow B in FIG. 1 is perpendicular to the torsion axis C and parallel to a plane in which the reflective surface 4 of the movable plate 6 is formed. The direction indicated by the arrow B is referred to as “movable plate width direction”.
In a surface of the movable plate 6 opposite to the reflective surface 4 (hereinafter, referred to as “back surface”), a plurality of recesses 5 is formed parallel to the B direction. This back surface refers to a surface of the movable plate 6 opposite to the reflective surface 4, that is, a surface having no reflective surface formed thereon. In particular, in two of the plurality of recesses 5, permanent magnets 7, for example rare-earth permanent magnets containing samarium-iron-nitrogen, are embedded. The permanent magnets 7 are each magnetized to opposite polarities with the torsion axis C therebetween.
Referring to FIG. 2, an action of the optical deflector 1 according to this embodiment will be described. FIG. 2 is a cross-sectional view of the optical deflector 1 shown in FIG. 1, taken along the line 2—2 in FIG. 1. As shown in FIG. 2, the permanent magnet 7 is magnetized to opposite polarities on both sides of the torsion axis C, and the direction of magnetization is as shown in the figure, for example. When the coil 9 is energized, a magnetic flux Φ is produced in a direction, for example as shown in FIG. 2, depending on the direction of the applied current. At the magnetic poles of the permanent magnet 7, attractive force and repulsive force are generated, respectively, in relation to the direction of the magnetic flux, and a torque T is applied to the movable plate 6, which is elastically supported around the torsion axis C. Similarly, if the current is applied to the coil 9 in the opposite direction, the torque T is applied thereto in the opposite direction. Therefore, as shown in FIG. 2, the movable plate 6 can be driven to any angle depending on the current applied to the coil 9.
FIG. 4 is a perspective view of an optical deflector according to a second embodiment of the invention. An optical deflector 21 of this embodiment is essentially the same in driving principle as the optical deflector 1 of the first embodiment. Furthermore, as in the first embodiment, the optical deflector 21 is integrally formed from single-crystal silicon by a micromachining technique, which is an application of the semiconductor producing technology.
FIG. 5A is a cross-sectional view taken along the line 5A—5A in FIG. 4, FIG. 5B is a cross-sectional view taken along the line 5B—5B in FIG. 4, and FIG. 5C is a cross-sectional view taken along the line 5C—5C in FIG. 4. The respective surfaces of the elastics supporting parts 3 and the recess are constituted by (111)-equivalent planes of single-crystal silicon, as shown in FIGS. 5A and 5B. The recess is provided so as not to extend over the torsion axis. Here, for example, a (−1-11) plane, a (11-1) plane and the like are collectively referred to as (111)-equivalent plane, and a (−100) plane and the like are collectively referred to as (100)-equivalent plane. The (100)-equivalent plane and the (111)-equivalent plane of silicon form an angle of about 54.7� with each other, as shown in FIG. 5A. Therefore, as can be seen from FIG. 5A, the side and back surfaces of the movable plate 6 can be constituted by the (111)-equivalent planes in a concave shape. As can be seen from FIG. 5C, the cross section of the elastic supporting part 3 taken along the line 5C—5C is in the shape of the letter X formed by the (111)- and (100)-equivalent planes.
As can be seen from FIG. 5B, the recess 5 formed in the back surface of the movable plate 6 has a cross section, taken along the line 5B—5B, in the shape of the letter V formed by the (111)-equivalent planes. As shown in FIGS. 4 and 5B, permanent magnets 7, which are formed from an iron-cobalt-chromium alloy wire, for example, have a cylindrical shape and are fitted into two of the recesses 5 and bonded thereto.
Now, a method of producing the supporting substrate 2, the elastic supporting part 3, the movable plate 6 and the recess 5 will be described with reference to FIGS. 12A to 12E. FIGS. 12A to 12E show steps of the method of producing the supporting substrate 2, the elastic supporting part 3, the movable plate 6 and the recess 5 by anisotropic etching using an aqueous alkaline solution according to this embodiment. These drawings show schematic cross sections thereof taken along the line 5A—5A in FIG. 4 in the respective steps. First, as shown in FIG. 12A, silicon-nitride mask layers 101 are formed on both surfaces of a planar silicon substrate 104 by low pressure chemical vapor deposition or the like.
Then, as shown in FIG. 12D, anisotropic etching is performed by dipping the substrate for a desired time in an aqueous alkaline solution having significantly different erosion rates for crystal faces of single-crystal silicon (for example, an aqueous potassium hydroxide solution, an aqueous tetramethylammonium hydroxide solution, etc.), thereby forming the supporting substrate 2, the movable plate 6, the elastic supporting part 3 and the recess 5 which are shaped as shown in FIG. 12D. In the anisotropic etching, the etch rate is greater for the (100)-equivalent plane and smaller for the (111)-equivalent plane. Therefore, the silicon substrate 104 is etched from the front and back surfaces thereof, and due to the relation of the patterns of the mask layers 101 with the silicon crystal faces, the silicon substrate 104 can be precisely etched into a shape formed by the (100)-equivalent planes covered with the mask layers 101 and the (111)-equivalent planes. That is, by this alkaline anisotropic etching, the recess 5 constituted by the (111)-equivalent planes is formed in the back surface of the movable plate 6, and the concave shape constituted by the (111)-equivalent planes is formed in the side faces thereof. At the same time, in this etching step, the elastic supporting parts 3 are also worked in the form of an X-shaped polygon formed by the (100)- and (111)-equivalent planes (see FIG. 5C).
FIG. 6 is a perspective view of an optical deflector according to a third embodiment of the invention.
FIG. 7 is a cross-sectional view taken along the line 7—7 in FIG. 6. The inner surfaces of the recess 5 are constituted by (111)-equivalent planes of single-crystal silicon wafer as with the optical deflector 21 of the second embodiment, and as shown in FIG. 7, the cross section of the recess 5 taken along the line 7—7 is in the shape of the letter V. In particular, in the optical deflector 31 of this embodiment, all the recesses 5 formed in the movable plate 6 are arranged symmetrically with respect to the torsion axis C, and no recess 5 is formed in the vicinity of the torsion axis C.
FIG. 8 is a perspective view of an optical deflector according to a fourth embodiment of the invention.
FIG. 9 is a cross-sectional view taken along the line 9—9 in FIG. 8. The inner surfaces of the recess 5 are constituted by (111)-equivalent planes of single-crystal silicon wafer as with the optical deflector 21 of the second embodiment, and as shown in FIG. 9, the cross section of the recess 5 taken along the line 9—9 is in the shape of the letter V. In particular, in the optical deflector 41 of this embodiment, the permanent magnet 7 is in the form of a planar rectangular parallelepiped and provided above the recess 5 as shown in FIG. 9.
FIG. 10 is a perspective view of an optical deflector according to a fifth embodiment of the invention.
FIG. 11 is a cross-sectional view taken along the line 11—11 in FIG. 10. The inner surfaces of the recess 5 are constituted by (111)-equivalent planes of single-crystal silicon wafer as with the optical deflector 21 of the second embodiment, and as shown in FIG. 11, the cross section, taken along the line 11—11, of a recess 5 in which the permanent magnet 7 is to be provided is in the shape of a rhombus, and the cross section of the other recesses 5 is in the shape of the letter V. In particular, in the optical deflector 51 of this embodiment, the permanent magnet 7 is embedded in the recess 5 having a rhombic cross section.
Now, a method of producing the supporting substrate 2, the elastic supporting part 3, the movable plate 6 and the recess 5 will be described with reference to FIGS. 13A to 13F. FIGS. 13A to 13F shows steps in the method of producing the supporting substrate 2, the elastic supporting part 3, the movable plate 6 and the recess 5 by etching according to this embodiment. These drawings show schematic cross sections thereof taken along the line 11—11 in FIG. 10 in the respective steps. First, as shown in FIG. 13A, silicon-nitride mask layers 101 are formed on both surface of a planar silicon substrate 104 by low pressure chemical vapor deposition or the like.
FIG. 14 shows an embodiment of an optical device using any one of the optical deflectors described above. In this embodiment, an image display device is adopted as the optical device. In FIG. 14, reference numeral 201 denotes an optical deflector group having two optical deflectors according to any one of the first to the fifth embodiments disposed with the deflection directions being perpendicular to each other. In this embodiment, the optical deflector group is used as an optical scanner device for raster-scanning an incident light in the horizontal and vertical directions. Reference numeral 202 denotes a laser source, reference numeral 203 denotes a lens or lens group, reference numeral 204 denotes a writing lens or writing lens group, and reference numeral 205 denotes a projection plane. An incident laser beam from the laser source 202 is subject to a predetermined intensity modulation associated with a scan timing and scans two-dimensionally under the action of the optical deflector group 201. The scanning laser beam forms an image on the projection plane 205 by means of writing lens 204. In short, the image display device according to this embodiment can be applied to display products.
FIG. 15 shows another embodiment of an optical device using any one of the optical deflectors described above. In this embodiment, an electrophotographic image forming device is adopted as the optical device. In FIG. 15, reference numeral 201 denotes an optical deflector according to any one of the first to the fifth embodiments, which is, in this embodiment, used as an optical scanner device for scanning an incident light one-dimensionally. Reference numeral 202 denotes a laser source. Reference numeral 203 denotes a lens or lens group, reference numeral 204 denotes a writing lens or writing lens group, and reference numeral 206 denotes a photosensitive body. A laser beam emitted from the laser source is subject to a predetermined intensity modulation associated with a scan timing and scans one-dimensionally under the action of the optical deflector 201. The scanning laser beam forms an image on the photosensitive body 206 by means of the writing lens 204.
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20030904 TO 20030911Dec 13, 2005CCCertificate of correctionOct 30, 2008FPAYFee paymentYear of fee payment: 4Sep 28, 2012FPAYFee paymentYear of fee payment: 8RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services