Source: http://www.google.com/patents/US7042621?dq=patent:4807115
Timestamp: 2014-12-18 10:04:58
Document Index: 18209232

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Patent US7042621 - Micromirror device - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsThere is provided a micromirror device, which is provided with a mirror layer including a mirror surface which is supported to be rotatable around a first axis passing through a center of the mirror surface, and an upper substrate having transparency including a first upper electrode part and a second...http://www.google.com/patents/US7042621?utm_source=gb-gplus-sharePatent US7042621 - Micromirror deviceAdvanced Patent SearchPublication numberUS7042621 B2Publication typeGrantApplication numberUS 11/036,983Publication dateMay 9, 2006Filing dateJan 19, 2005Priority dateJan 20, 2004Fee statusLapsedAlso published asDE102005002794A1, US7116465, US20050179981, US20060152793Publication number036983, 11036983, US 7042621 B2, US 7042621B2, US-B2-7042621, US7042621 B2, US7042621B2InventorsMasanori Maeda, Satoshi Karasawa, Rogerio Jun Mizuno, Naoki KikuchiOriginal AssigneePentax CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (10), Non-Patent Citations (2), Referenced by (4), Classifications (15), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMicromirror deviceUS 7042621 B2Abstract There is provided a micromirror device, which is provided with a mirror layer including a mirror surface which is supported to be rotatable around a first axis passing through a center of the mirror surface, and an upper substrate having transparency including a first upper electrode part and a second upper electrode part arranged on its surface facing the mirror layer to face each other via a first upper boundary passing through a center of the surface and parallel to the first axis, and a lower substrate including a first lower electrode part and a second lower electrode part arranged on its surface facing the mirror layer to face each other via a first lower boundary passing through a center of the surface and parallel to the first axis. The upper substrate is stacked on one side of the mirror layer while securing a first space between the center of the mirror surface and the first and second upper electrode parts, while the lower substrate is stacked on the other side of the mirror layer while securing a second space between the center of the mirror surface and the first and second lower electrode parts. The mirror surface is rotated around the first axis by applying voltage to a pair of the electrodes placed diagonally with respect to the first axis.
BACKGROUND OF THE INVENTION The present invention relates to a micromirror device of a capacitance type which is used for scanning an optical beam.
Micromirror devices of the capacitance type (hereinafter also referred to simply as �micromirror devices�) have widely been used in various technical fields like optical switches for communication, measuring instruments, scanners, etc. In a micromirror device of the capacitance type, a plurality of electrodes are arranged on a substrate which is placed under a mirror scanning an incident beam. By applying voltage to a proper electrode, electrostatic attraction is caused between the electrode and the mirror and thereby the surface of the mirror is tilted in a desired direction. A typical micromirror device has been disclosed in Japanese Patent Provisional Publication No.2003-29172 (hereinafter referred to as a �document No.1�), for example.
Meanwhile, a micromirror device disclosed in Japanese Patent Provisional Publication No.2003-57575 (hereinafter referred to as a �document No.2�) aims to miniaturize the whole device and achieves a wide scan range by increasing the electrostatic attraction applied to the mirror by reducing a space between a mirror and electrodes.
SUMMARY OF THE INVENTION However, if the space between the mirror and the electrodes is designed small as above, a so-called �pull-in� (the tilted mirror sticking to an electrode and getting uncontrollable) might occur. Consequently, the controllable tilt angle becomes small as a matter of course and thereby the scan range is necessitated to be small.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 is a perspective view showing the overall composition of a micromirror device in accordance with an embodiment of the present invention;
FIG. 4A is a cross-sectional view of an upper substrate of the micromirror device taken along the line A�A shown in FIG. 2;
FIG. 5A is a cross-sectional view of the micromirror device taken along a plane containing the X axis and the line A�A of FIG. 2, showing the status of the device before the application of voltage to drive electrodes;
FIG. 5B is a cross-sectional view of the micromirror device taken along a plane containing the X axis and the line A�A of FIG. 2, showing the status of the device with a prescribed voltage applied to drive electrodes; and
DETAILED DESCRIPTION OF THE EMBODIMENTS Referring now to the drawings, a description will be given in detail of a preferred embodiment in accordance with the present invention. FIG. 1 is a perspective view showing the overall configuration of a micromirror device 10 according to an embodiment of the present invention. As shown in FIG. 1, the micromirror device 10 is formed in a shape like a cuboid. FIG. 2 is a perspective view showing components of the micromirror device 10 in a disassembled state.
As shown in FIGS. 1 and 2, the micromirror device 10 includes an upper substrate 2 and a lower substrate 3 stacked up to sandwich a mirror layer 1. The upper substrate 2 is stacked on the mirror layer 1 via a spacer 4, and thus the micromirror device 10 includes the upper substrate 2, the spacer 4, the mirror layer 1 and the lower substrate 3 from its light incident side. In this description, part of the micromirror device 10 in the light incident side is defined as an �upper part� and the other part is defined as a �lower part� for the sake of convenience.
As shown in FIG. 2, the mirror layer 1 includes a circular mirror surface 11 placed in the central part of the mirror layer 1, a ring-shaped frame 12 placed to surround the periphery of the mirror surface 11, and an outer frame 13 formed to surround the frame 12. The frame 12 has a pair of hinge parts 12X arranged in a first direction (x direction) to sandwich the mirror surface 11 (hereinafter referred to as �first hinge parts 12X�). Each first hinge part 12X is joined to the mirror surface 11 at one end, while being joined to the frame 12 at the other end. Therefore, the first hinge parts 12X support the mirror surface 11 to be rotatable around an X axis in the x direction. The frame 12 is further provided with another pair of hinge parts 12Y arranged in a second direction (y direction) orthogonal to the x direction to sandwich the frame 12 (hereinafter referred to as �second hinge parts 12Y�). Each second hinge part 12Y is joined to the frame 12 at one end, while being connected to the outer frame 13 at the other end. Therefore, the second hinge parts 12Y support the frame 12 and the mirror surface 11 to be rotatable around a Y axis in the y direction. In FIG. 2, the X and Y axes are indicated with broken lines and the intersection of the two axes (the center of the mirror surface 11) is indicated with a reference character �C1�.
FIG. 3 is a schematic diagram showing the cross-sectional configuration of the mirror layer 1 shown in FIG. 2 along the X axis. As shown in FIG. 3, a protruded part 14 is provided to a peripheral part of the outer frame 13 facing the lower substrate 3 so as to protrude downward by a prescribed level difference compared with the central part where the mirror surface 11 is placed. The protruded part 14 is formed in order to secure a prescribed space (hereinafter referred to as a �lower space�) between the mirror layer 1 and the lower substrate 3.
Next, the upper substrate 2 will be explained referring to FIGS. 4A through 4C. FIG. 4A is a cross-sectional view of the upper substrate 2 shown in FIG. 2 taken along the line A�A (diagonal line). FIG. 4B is a bottom view of the upper substrate 2 seen from the mirror layer's side. FIG. 4C is a top view of the upper substrate 2 seen from the light incident side.
The upper substrate 2 is prepared by processing a glass substrate 2 a having sufficient transparency allowing a beam led from outside to be incident upon the mirror surface 11. As shown in FIGS. 4A and 4B, first through fourth drive electrodes T1�T4 are formed on a plane surface 2 b of the upper substrate 2 facing the mirror layer 1. Each drive electrode T1�T4 is formed as a transparent electrode like an ITO (Indium-Tin-Oxide) film so as not to block the incidence of the beam upon the mirror surface 11. The drive electrodes T1�T4 are shaped into sector forms of the same size. Specifically, first and second drive electrodes T1 and T2 are placed to be symmetrical with each other with respect to a boundary passing through the center C2 of the upper substrate 2 and stretching in the y direction (first boundary, corresponding to the Y axis of the mirror layer 1). Third and fourth drive electrodes T3 and T4 are placed to be symmetrical with each other with respect to a boundary passing through the center C2 and stretching in the x direction (second boundary, corresponding to the X axis of the mirror layer 1).
As shown in FIGS. 4A and 4C, on a surface 2 c of the upper substrate 2 opposite to the surface 2 b facing the mirror layer 1, first through fourth wiring electrodes t1�t4 are formed so that voltage supplied from the outside of the micromirror device 10 can be applied to the drive electrodes T1�T4.
The glass substrate 2 a is also provided with conducting parts 2 d for electrically connecting the wiring electrodes t1�t4 to the drive electrodes T1�T4, respectively. Each conducting part 2 d is formed by opening a through hole through the glass substrate 2 a by sand blasting, etc. and filling the through hole with conductive material. The formation of the conducting part 2 d (through hole) by sand blasting is only an example, and thus other techniques can also be used as long as the conducting part 2 d (through hole) can be formed. By the above configuraton, voltage supplied from the outside of the micromirror device 10 can be applied to the drive electrodes T1�T4 via the conducting parts 2 d. The lower substrate 3 in this embodiment is configured to be the same as the upper substrate 2 which has been described above. By the common use of the same substrate configuration for the upper and lower substrates 2 and 3, costs can be reduced and efficiency of assembly work can be increased. Further, among the electrodes facing one another via the mirror layer 1 (mirror surface 11), those placed diagonally with respect to the X axis or the Y axis are in symmetrical relationship with each other with respect to the center C1 of the mirror surface 11. Therefore, the electrostatic forces produced when a predetermined voltage is applied to the electrodes become substantially the same.
The spacer 4 is provided in order to secure a prescribed space (hereinafter referred to as an �upper space�) between the upper substrate 2 and the mirror layer 1. Specifically, the spacer 4 is made of silicon to have substantially the same height as the protruded part 14 of the mirror layer 1. In other words, in the micromirror device 10 of this embodiment, the upper space secured by the spacer 4 has substantially the same height as the lower space secured by the protruded part 14. Therefore, electrostatic forces applied to the mirror surface 11 when a certain voltage is applied to the electrodes T1 to T4 become substantially the same, and thus application of bias voltage causes no displacement of the mirror surface 11.
In the stacking of the components 1 to 4, various joining techniques can be used. In this embodiment, the components 1 to 4 are joined together by anode junction. Since the spacer 4 and the mirror layer 1 (both made of silicon) can not be joined directly by anode junction, a thin glass layer is placed between the spacer 4 and the mirror layer 1 and the two layers are joined together by anode junction via the glass layer. Incidentally, an error in the height of the upper space caused by the glass layer has no effect in practical use since the glass layer is far thinner than each component 1�4.
In cases where the components 1�4 are vacuum-packaged in the last step of the manufacturing process of the micromirror device 10, the use of a spacer 4 made of Pyrex glass is desirable. Parts that can not be joined together by anode junction may also be joined by use of polyimide adhesives like Photoneece.
The principle of operation of the micromirror device 10 configured as above will be explained below referring to FIGS. 5A and 5B. The mirror layer 1 shown in FIGS. 5A and 5B has the same configuration as that shown in FIG. 3. Thus, FIGS. 5A and 5B are cross-sectional views of the micromirror device 10 taken along a plane containing the X axis and the line A�A shown in FIG. 2, in which FIG. 5A shows the status of the micromirror device 10 before the application of voltage to drive the electrodes and FIG. 5B shows the status of the micromirror device 10 with a prescribed voltage applied to drive electrodes. In FIGS. 5A and 5B, for discriminating between the drive electrodes T1�T4 provided to the upper substrate 2 and the lower substrate 3, drive electrodes of the upper substrate 2 are referred to as �upper drive electrodes T1 u�T4 u� while those of the lower substrate 3 are referred to as �lower drive electrodes T1 d�T4 d� for the sake of convenience.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5799643 *Oct 1, 1996Sep 1, 1998Nippei Toyama CorpSlurry managing system and slurry managing method for wire sawsUS6431714Oct 5, 2001Aug 13, 2002Nippon Telegraph And Telephone CorporationMicro-mirror apparatus and production method thereforUS6473221 *Mar 12, 2001Oct 29, 2002Fujitsu LimitedGalvano-mirror and method of making the sameUS6545260 *Nov 16, 2000Apr 8, 2003Olympus Optical Co., Ltd.Light scanning optical device which acquires a high resolution two-dimensional image without employing a charge-coupled deviceUS6633426 *May 10, 2001Oct 14, 2003Analog Devices, Inc.Overlaying or covered with an optically transmissive substrate held spaced in inverted preferably flip-chip bonded fashion to the device, with transparent electrodes provided in the substrate for generating an upper mirror-actuating field toUS6891650 *Jan 13, 2004May 10, 2005Fujitsu Limited,Micromirror unit fabrication method and micromirror unit made by the sameUS20020018276 *Apr 24, 2001Feb 14, 2002Takeshi SugaConfocal optical systemUS20030016906Jul 16, 2002Jan 23, 2003Nec CorporationOptical switchJP2003029172A Title not availableJP2003057575A Title not available* Cited by examinerNon-Patent CitationsReference1T.J. Brosnihan et al., The 12<SUP>th </SUP>International Conference on Solid State Sensors, Actuators and Microsystems, Boston, Jun. 8-12, 2003, IEEE, 2003, pp. 1638-1642.2U.S. Appl. No. 11/042,157, to Mizuno, which was filed Jan. 26, 2005.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7271946Dec 27, 2006Sep 18, 2007Tohoku UniversityMicromirror and micromirror deviceUS7277217 *Mar 1, 2007Oct 2, 2007Ricoh Company, Ltd.Optical deflecting device, optical deflecting device manufacturing method, and optical projecting deviceUS7372620Dec 27, 2006May 13, 2008Tohoku UniversityMicromirror and micromirror deviceUS8094357 *Jul 27, 2007Jan 10, 2012Nippon Telegraph And Telephone CorporationMirror control device* Cited by examinerClassifications U.S. Classification359/290, 359/226.1, 600/476, 600/473, 359/904, 359/291International ClassificationA61B6/00, G02B26/08, B81B3/00, G02B26/00Cooperative ClassificationY10S359/904, G02B26/0841, G02B21/0048European ClassificationG02B26/08M4E, G02B21/00M4A5MLegal EventsDateCodeEventDescriptionMay 9, 2014LAPSLapse for failure to pay maintenance feesDec 20, 2013REMIMaintenance fee reminder mailedOct 7, 2009FPAYFee paymentYear of fee payment: 4Apr 29, 2005ASAssignmentOwner name: PENTAX CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MAEDA, MASANORI;KARASAWA, SATOSHI;MIZUNO, ROGERIO JUN;AND OTHERS;REEL/FRAME:016508/0521;SIGNING DATES FROM 20050217 TO 20050318RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google