Patent Publication Number: US-2023161153-A1

Title: Optical scanning device and distance measuring device

Description:
TECHNICAL FIELD 
     The present disclosure relates to an optical scanning device and a distance measuring device. 
     BACKGROUND ART 
     Japanese Patent No. 2722314 (PTL 1) discloses a planar galvanometer mirror. The planar galvanometer mirror includes a semiconductor substrate, a movable plate, a mirror provided on the movable plate, and a torsion bar that swingably supports the movable plate on the semiconductor substrate. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent No. 2722314 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the galvanometer mirror described above, the mirror unit including the movable plate and the mirror film is driven by the resonance frequency of the mirror unit to scan a light beam at a large deflection angle as fast as possible. However, in order to prevent torsional rupture of the torsion bar, the deflection angle of the galvanometer mirror is limited to an angle less than 20° at the maximum. The light beam incident on the galvanometer mirror is received by a single mirror. As a result, the size and the mass of the mirror unit become large, and thereby there is a limit to speeding up the optical scanning using the galvanometer mirror. 
     The present disclosure has been made to solve the aforementioned problems, and an object of an aspect of the present disclosure is to provide an optical scanning device capable of performing an optical scanning with a light beam at a higher speed and a larger deflection angle. Another object of the present disclosure is to provide a distance measuring device capable of measuring an ambient distance more quickly and more easily. 
     Solution to Problem 
     The optical scanning device of the present disclosure includes a substrate and a plurality of movable mirror elements. The substrate includes a main surface that extends in a first direction and a second direction perpendicular to the first direction. The plurality of movable mirror elements are two-dimensionally arranged on the main surface of the substrate in a plan view of the main surface of the substrate. The plurality of movable mirror elements are capable of operating independently of each other and capable of forming a diffraction grating. Each of the plurality of movable mirror elements includes a beam, a first anchor, a second anchor, a movable mirror, and a pillar. The beam is bendable in a third direction perpendicular to the main surface. The first anchor is provided on the main surface of the substrate to support a first end of the beam. The second anchor is provided on the main surface of the substrate to support the second end of the beam opposite to the first end. The movable mirror includes a movable plate separated from the beam in the third direction, and a mirror film disposed on the movable plate. The pillar connects the movable plate and a portion of the beam other than the first end and the second end to each other. 
     The distance measuring device of the present disclosure includes the optical scanning device of the present disclosure. 
     Advantageous Effects of Invention 
     In the optical scanning device of the present disclosure, the light beam incident on the optical scanning device is received by the movable mirror of each of the plurality of movable mirror elements. Thus, it is possible to reduce the size and mass of each movable mirror, which makes it possible to move each movable mirror at a higher speed. Therefore, it is possible for the optical scanning device to perform an optical scanning with a light beam at a higher speed. Further, in the optical scanning device, the light beam incident on the optical scanning device is deflected by using a diffraction grating formed from a plurality of movable mirror elements capable of operating independently of each other. Therefore, it is possible for the optical scanning device to perform an optical scanning with a light beam at a larger deflection angle. 
     The distance measuring device of the present disclosure includes the optical scanning device of the present disclosure capable of performing an optical scanning with a light beam at a higher speed. Therefore, it is possible for the distance measuring device to measure the ambient distance more quickly. The distance measuring device of the present disclosure includes the optical scanning device of the present disclosure capable of perform an optical scanning with a light beam at a larger deflection angle. Therefore, it is possible for the distance measuring device to measure the ambient distance more easily. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic view illustrating an optical scanning device according to a first embodiment, a third embodiment and a fourth embodiment; 
         FIG.  2    is a partially enlarged schematic perspective view illustrating the optical scanning device according to the first embodiment; 
         FIG.  3    is a partially enlarged schematic cross-sectional view illustrating the optical scanning device of the first embodiment taken along a cross-sectional line illustrated in  FIGS.  5  and  6   ; 
         FIG.  4    is a partially enlarged schematic cross-sectional view illustrating the optical scanning device according to the first embodiment; 
         FIG.  5    is a partially enlarged schematic plan view illustrating the optical scanning device according to the first embodiment; 
         FIG.  6    is a partially enlarged schematic plan view illustrating the optical scanning device according to the first embodiment; 
         FIG.  7    is a schematic enlarged side view illustrating the optical scanning device according to the first embodiment; 
         FIG.  8    is a partially enlarged schematic perspective view illustrating the optical scanning device according to the first embodiment; 
         FIG.  9    is a partially enlarged schematic perspective view illustrating the optical scanning device according to the first embodiment; 
         FIG.  10    is a partially enlarged schematic cross-sectional view illustrating a step in a manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  11    is a partially enlarged schematic cross-sectional view illustrating a step subsequent to the step illustrated in  FIG.  10    in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  12    is a partially enlarged schematic cross-sectional view illustrating a step subsequent to the step illustrated in  FIG.  11    in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  13    is a partially enlarged schematic cross-sectional view illustrating a step in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  14    is a partially enlarged schematic cross-sectional view illustrating a step subsequent to the step illustrated in  FIG.  13    in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  15    is a partially enlarged schematic cross-sectional view illustrating a step subsequent to the step illustrated in  FIGS.  12  and  14    in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  16    is a partially enlarged schematic cross-sectional view illustrating a step subsequent to the step illustrated in  FIG.  15    in the manufacturing method of the optical scanning device according to the first embodiment; 
         FIG.  17    is a partially enlarged schematic perspective view illustrating an optical scanning device according to a modification of the first embodiment; 
         FIG.  18    is a partially enlarged schematic perspective view illustrating an optical scanning device according to a modification of the first embodiment; 
         FIG.  19    is a partially enlarged schematic perspective view illustrating an optical scanning device according to a modification of the first embodiment; 
         FIG.  20    is a schematic view illustrating an optical scanning device according to a second embodiment; 
         FIG.  21    is a partially enlarged schematic plan view illustrating the optical scanning device according to the second embodiment; 
         FIG.  22    is a partially enlarged schematic plan view illustrating an optical scanning device according to a third embodiment; 
         FIG.  23    is a partially enlarged schematic plan view illustrating an optical scanning device according to a fourth embodiment; 
         FIG.  24    is a schematic view illustrating an optical scanning device according to a fifth embodiment; 
         FIG.  25    is a partially enlarged schematic cross-sectional view illustrating an optical scanning device according to a fifth embodiment; 
         FIG.  26    is a schematic view illustrating a distance measuring device according to a sixth embodiment; and 
         FIG.  27    is a schematic block view illustrating a controller included in the distance measuring device according to the sixth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described. The same components are denoted by the same reference numerals, and the description thereof will not be repeated. 
     First Embodiment 
     An optical scanning device  1  according to a first embodiment will be described with reference to  FIGS.  1  to  6   . The optical scanning device  1  includes a substrate  2 , a plurality of movable mirror elements  3 , and a controller  7 . 
     The substrate  2  includes a main surface  2   a  that extends in a first direction (x direction) and a second direction (y direction) perpendicular to the first direction (x direction). The substrate  2  has a thickness of, for example, 100 μm or more and 1000 μm or less. 
     As illustrated in  FIGS.  3  and  4   , in the present embodiment, the substrate  2  includes a conductive substrate  10  and a first insulating film  11  provided on the conductive substrate  10 . The conductive substrate  10  is, for example, a silicon substrate containing a dopant, and the first insulating film  11  is, for example, a silicon nitride film, a silicon dioxide film, or a laminated film of a silicon nitride film and a silicon dioxide film. The substrate  2  may be an insulating substrate. The first insulating film  11  has a thickness of, for example, 0.01 μm or more and 1.0 μm or less. When the substrate  2  is an insulating substrate, the first insulating film  11  may be dispensed with. 
     In a plan view of the main surface  2   a  of the substrate  2 , the plurality of movable mirror elements  3  are two-dimensionally arranged on the main surface  2   a  of the substrate  2 . The plurality of movable mirror elements  3  are capable of operating independently of each other and capable of forming a diffraction grating. Each of the plurality of movable mirror elements  3  includes an electrode  12   a , an electrode  12   b , a wiring  13   a , a wiring  13   b , an electrode  14 , a wiring  15 , an anchor  17   a , an anchor  17   b , a beam  18   a , a movable mirror  20 , and a pillar  23 . Each of the plurality of movable mirror elements  3  may further include an electrode  12   c , an electrode  12   d , a wiring  13   c , a wiring  13   d , an anchor  17   c , an anchor  17   d , and a beam  18   b.    
     The electrode  12   a  and the electrode  12   b  are provided on the main surface  2   a  of the substrate  2 . Specifically, the electrode  12   a  and the electrode  12   b  are provided on the first insulating film  11 , and are separated from each other. The wiring  13   a  and the wiring  13   b  are provided on the main surface  2   a  of the substrate  2 . Specifically, the wiring  13   a  and the wiring  13   b  are provided on the first insulating film  11 . The wiring  13   a  is connected to the electrode  12   a , and is configured to supply a voltage to the electrode  12   a . The wiring  13   b  is connected to the electrode  12   b , and is configured to supply a voltage to the electrode  12   b . Each of the electrode  12   a , the electrode  12   b , the wiring  13   a , and the wiring  13   b  is made of, for example, conductive polysilicon or a metal such as aluminum, gold or platinum. Each of the electrode  12   a , the electrode  12   b , the wiring  13   a , and the wiring  13   b  has a thickness of, for example, 0.10 μm or more and 10 μm or less. 
     The electrode  12   c  and the electrode  12   d  are provided on the main surface  2   a  of the substrate  2 . Specifically, the electrode  12   c  and the electrode  12   d  are provided on the first insulating film  11 , and are separated from each other. The wiring  13   c  and the wiring  13   d  are provided on the main surface  2   a  of the substrate  2 . Specifically, the wiring  13   c  and the wiring  13   d  are provided on the first insulating film  11 . The wiring  13   c  is connected to the electrode  12   c , and is configured to supply a voltage to the electrode  12   c . The wiring  13   d  is connected to the electrode  12   d , and is configured to supply a voltage to the electrode  12   d . Each of the electrode  12   c , the electrode  12   d , the wiring  13   c , and the wiring  13   d  is made of, for example, conductive polysilicon or a metal such as aluminum, gold or platinum. Each of the electrode  12   c , the electrode  12   d , the wiring  13   c , and the wiring  13   d  has a thickness of, for example, 0.10 μm or more and 10 μm or less. 
     The electrode  14  is provided on the main surface  2   a  of the substrate  2 . Specifically, the electrode  14  is provided on the first insulating film  11  and is electrically insulated from the electrodes  12   a  and  12   b  and the electrodes  12   c  and  12   d.    
     The electrode  14  is opposed to the pillar  23  in a third direction (z direction). The wiring  15  is provided on the main surface  2   a  of the substrate  2 . Specifically, the wiring  15  is provided on the first insulating film  11 . The wiring  15  is connected to the electrode  14 , and is configured to supply a voltage to the electrode  14 . The electrode  14  and the wiring  15  are made of, for example, conductive polysilicon or a metal such as aluminum, gold or platinum. Each of the electrode  14  and the wiring  15  has a thickness of, for example, 0.10 μm or more and 10 μm or less. 
     The anchor  17   a  and the anchor  17   b  are provided on the main surface  2   a  of the substrate  2 . Specifically, the anchor  17   a  is provided on the electrode  12   a , and is provided on the main surface  2   a  of the substrate  2  via the electrode  12   a . The anchor  17   b  is provided on the electrode  12   b , and is provided on the main surface  2   a  of the substrate  2  via the electrode  12   b . The anchor  17   a  and the anchor  17   b  support the beam  18   a . Specifically, the anchor  17   a  supports a first end of the beam  18   a . The anchor  17   b  supports a second end of the beam  18   a  opposite to the first end of the beam  18   a . The anchor  17   a  and the anchor  17   b  may be electrically conductive. Each of the anchor  17   a  and the anchor  17   b  is made of, for example, conductive polysilicon. The anchor  17   a  is electrically connected to the electrode  12   a . The anchor  17   b  is electrically connected to the electrode  12   b.    
     The anchor  17   c  and the anchor  17   d  are provided on the main surface  2   a  of the substrate  2 . Specifically, the anchor  17   c  is provided on the electrode  12   c , and is provided on the main surface  2   a  of the substrate  2  via the electrode  12   c . The anchor  17   d  is provided on the electrode  12   d , and is provided on the main surface  2   a  of the substrate  2  via the electrode  12   d . The anchor  17   c  and the anchor  17   d  support the beam  18   b . Specifically, the anchor  17   c  supports a third end of the beam  18   b . The anchor  17   d  supports a fourth end of the beam  18   b  opposite to the third end of the beam  18   b . The anchor  17   c  and the anchor  17   d  may be electrically conductive. Each of the anchor  17   c  and the anchor  17   d  is made of, for example, conductive polysilicon. The anchor  17   c  is electrically connected to the electrode  12   c . The anchor  17   d  is electrically connected to the electrode  12   d.    
     As illustrated in  FIGS.  3  and  4   , the beam  18   a  is bendable in the third direction (z direction) perpendicular to the main surface  2   a  of the substrate  2 . The beam  18   a  is fixed to the substrate  2  by the anchor  17   c  and the anchor  17   d . Specifically, the first end of the beam  18   a  is supported by the anchor  17   a . The second end of the beam  18   a  is supported by the anchor  17   b . The beam  18   a  may be electrically conductive. The beam  18   a  is made of, for example, conductive polysilicon. The beam  18   a  is electrically connected to the electrode  12   a  via the anchor  17   a . The beam  18   a  is electrically connected to the electrode  12   b  via the anchor  17   b.    
     The beam  18   b  is bendable in the third direction (z direction) perpendicular to the main surface  2   a  of the substrate  2 . The beam  18   b  is fixed to the substrate  2  by the anchor  17   c  and the anchor  17   d . Specifically, the third end of the beam  18   b  is supported by the anchor  17   c . The fourth end of the beam  18   b  is supported by the anchor  17   d . The beam  18   b  may be electrically conductive. The beam  18   b  is made of, for example, conductive polysilicon. The beam  18   b  is electrically connected to the electrode  12   c  via the anchor  17   c . The beam  18   b  is electrically connected to the electrode  12   d  via the anchor  17   d.    
     As illustrated in  FIG.  6   , in a plan view of the main surface  2   a  of the substrate  2 , the longitudinal direction of the beam  18   b  at a portion of the beam  18   b  connected to the pillar  23  intersects the longitudinal direction of the beam  18   a  at a portion of the beam  18   a  connected to the pillar  23 . Specifically, in the plan view of the main surface  2   a  of the substrate  2 , the longitudinal direction of the beam  18   b  at the portion of the beam  18   b  connected to the pillar  23  is perpendicular to the longitudinal direction of the beam  18   a  at the portion of the beam  18   a  connected to the pillar  23 . Specifically, in the plan view of the main surface  2   a  of the substrate  2 , the longitudinal direction of the beam  18   a  at the portion of the beam  18   a  connected to the pillar  23  is the second direction (y direction). In the plan view of the main surface  2   a  of the substrate  2 , the longitudinal direction of the beam  18   b  at the portion of the beam  18   b  connected to the pillar  23  is the first direction (x direction). 
     In the plan view of the main surface  2   a  of the substrate  2 , the movable mirror  20  has, for example, a square shape. The movable mirror  20  includes a movable plate  21  and a mirror film  22 . The movable plate  21  is separated from the beam  18   a  in the third direction (z direction). The movable plate  21  is separated from the beam  18   b  in the third direction (z direction). The movable plate  21  is made of, for example, conductive silicon. The mirror film  22  is provided on the movable plate  21 . The mirror film  22  is, for example, a Cr/Ni/Au film or a Ti/Pt/Au film. The Cr film and the Ti film improve adhesion of the mirror film  22  to the movable plate  21  made of silicon. Since the uppermost layer of the mirror film  22  is an Au film, the mirror film  22  has a high reflectivity for a light beam incident on the optical scanning device  1 . 
     The longitudinal direction of the pillar  23  is the third direction (z direction). The pillar  23  connects the movable plate  21  to a portion of the beam  18   a  other than the first end of the beam  18   a  and the second end of the beam  18   a  to each other. Specifically, the portion of the beam  18   a  is a central portion of the beam  18   a , and the pillar  23  is connected to the central portion of the beam  18   a . The pillar  23  connects the movable plate  21  and a portion of the beam  18   b  other than the third end of the beam  18   b  and the fourth end of the beam  18   b  to each other. Specifically, the portion of the beam  18   b  is a central portion of the beam  18   b , and the pillar  23  is connected to the central portion of the beam  18   b . The pillar  23  is connected to a back surface of the movable plate  21  opposite to a front surface of the movable plate  21  on which the mirror film  22  is provided. The pillar  23  may be connected to the back surface of the movable plate  21  via a second insulating film  24 . The pillar  23  is made of, for example, conductive silicon. The second insulating film  24  is, for example, a silicon dioxide film. 
     The pillar  23  and the portion of the beam  18   a  connected to the pillar  23  are opposed to the electrode  14  in the third direction (z direction). The pillar  23  and the portion of the beam  18   b  connected to the pillar  23  are opposed to the electrode  14  in the third direction (z direction). The movable mirror  20  and the pillar  23  are supported by the beam  18   a . The movable mirror  20  and the pillar  23  may be supported by the beam  18   a  and the beam  18   b . Since the movable mirror  20  and the pillar  23  are supported by the beam  18   a  and the beam  18   b , it is possible to more reliably set the displacement direction of the movable mirror  20  to the third direction (z direction) perpendicular to the substrate  2 . 
     The controller  7  includes, for example, a semiconductor processor such as a central processing unit (CPU). The controller  7  controls a vertical displacement amount of the movable mirror  20  in the third direction (z direction) so as to form a diffraction grating from the plurality of movable mirror elements  3 . 
     Specifically, as illustrated in  FIG.  1   , the controller  7  includes a voltage control unit  8 . The voltage control unit  8  is connected to the electrodes  12   a  and  12   b  via the wirings  13   a  and  13   b . The voltage control unit  8  is connected to the electrodes  12   c  and  12   d  via the wirings  13   c  and  13   d . The beam  18   a  is electrically connected to the electrode  12   a  via the anchor  17   a . The beam  18   a  is electrically connected to the electrode  12   b  via the anchor  17   b . Specifically, the electrode  12   a  is electrically connected to the first end of the beam  18   a  via the anchor  17   a . The electrode  12   b  is electrically connected to the second end of the beam  18   a  opposite to the first end of the beam  18   a  via the anchor  17   b.    
     The beam  18   b  is electrically connected to the electrode  12   c  via the anchor  17   c . The beam  18   b  is electrically connected to the electrode  12   d  via the anchor  17   d . Specifically, the electrode  12   c  is electrically connected to the third end of the beam  18   b  via the anchor  17   c . The electrode  12   d  is electrically connected to the fourth end of the beam  18   b  opposite to the third end of the beam  18   b  via the anchor  17   d . The voltage controller  8  controls the voltage of the beam  18   a  electrically connected to the electrodes  12   a  and  12   b . The voltage controller  8  controls the voltage of the beam  18   b  electrically connected to the electrodes  12   c  and  12   d.    
     The voltage control unit  8  is connected to the electrode  14  via the wiring  15 . The voltage control unit  8  controls the voltage of the electrode  14 . Thus, the voltage control unit  8  controls the voltage between the beam  18   a  and the electrode  14 . The voltage controller  8  controls the voltage between the beam  18   b  and the electrode  14 . Thus, the controller  7  can control a vertical displacement amount of the movable mirror  20  in the third direction (z direction). 
     For example, the voltage between the beam  18   a  and the electrode  14  of a non-hatched movable mirror element  3  in  FIG.  2    is relatively lower than that of a hatched movable mirror element  3  in  FIG.  2   . As illustrated in  FIG.  3   , the vertical displacement amount of the movable mirror  20  of a non-hatched movable mirror element  3  in  FIG.  2    is a first vertical displacement amount. Specifically, the voltage between the beam  18   a  and the electrode  14  of a non-hatched movable mirror element  3  in  FIG.  2    is zero, and no electrostatic attractive force acts between the beam  18   a  and the electrode  14 . The beam  18   a  of a non-hatched movable mirror element  3  in  FIG.  2    is not bent, and thereby the first vertical displacement amount of the movable mirror  20  is zero. 
     On the other hand, as illustrated in  FIG.  4   , a second vertical displacement amount of the movable mirror  20  of a hatched movable mirror element  3  in  FIG.  2    is larger than the first vertical displacement amount. In the third direction (z direction), the movable mirror  20  of a hatched movable mirror element  3  in  FIG.  2    is closer to the main surface  2   a  of the substrate  2  than the movable mirror  20  of a non-hatched movable mirror element  3  in  FIG.  2   . Specifically, in a hatched movable mirror element  3  in  FIG.  2   , the voltage between the beam  18   a  and the electrode  14  is non-zero, and thereby an electrostatic attractive force acts between the beam  18   a  and the electrode  14 . In a hatched movable mirror element  3  of  FIG.  2   , the beam  18   a  is bent toward the main surface  2   a  of the substrate  2 , and the second vertical displacement amount of the movable mirror  20  is larger than the first vertical displacement amount. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     As illustrated in  FIG.  2   , the controller  7  constructs a plurality of first movable mirror arrays  4  and a plurality of second movable mirror arrays  5  from the plurality of movable mirror elements  3 . The plurality of first movable mirror arrays  4  are constructed from a part of the plurality of movable mirror elements  3  in which the vertical displacement amount of the movable mirror  20  is the first vertical displacement amount. The plurality of second movable mirror arrays  5  are constructed from the remaining part of the plurality of movable mirror elements  3  in which the vertical displacement amount of the movable mirror  20  is the second vertical displacement amount which is larger than the first vertical displacement amount. In the plan view of the main surface  2   a  of the substrate  2 , a first longitudinal direction of each of the plurality of first movable mirror arrays  4  is parallel to a second longitudinal direction of each of the plurality of second movable mirror arrays  5 . The plurality of first movable mirror arrays  4  and the plurality of second movable mirror arrays  5  are arranged alternately and periodically in a direction perpendicular to the first longitudinal direction. Thus, the plurality of movable mirror elements  3  can form a diffraction grating. 
     As illustrated in  FIG.  7   , a light beam  40  is incident on the movable mirrors  20  of the plurality of movable mirror elements  3  in the third direction (z direction). The light beam  40  is diffracted by the diffraction grating formed by the movable mirrors  20  of the plurality of movable mirror elements  3 . A diffraction angle θ of the light beam diffracted by the plurality of movable mirror elements  3 , that is, a deflection angle of the optical scanning device  1  is given by the following equation (1). The diffraction angle θ is defined as an angle between the light beam  40  incident on the plurality of movable mirror elements  3  and a diffraction light beam (for example, a +1 order diffraction light beam  41 ) diffracted by the plurality of movable mirror elements  3 . “d” represents a period of the plurality of first movable mirror arrays  4  (i.e., a period of the plurality of second movable mirror arrays  5 ). “λ” represents the wavelength of the light beam  40  incident on the plurality of movable mirror elements  3 . “m” represents an integer. 
         d ×sin θ= mλ   (1)
 
     The diffraction grating formed by the movable mirrors  20  of the plurality of movable mirror elements  3  generates, for example, a +1 order diffraction light beam  41  and a −1 order diffraction light beam  42 . The +1 order diffraction light beam  41  is a diffraction light beam having a diffraction order of +1. The −1 order diffraction light beam  42  is a diffraction light beam having a diffraction order of −1. The diffraction order of the diffraction light beam is equal to m. 
     The plurality of movable mirror elements  3  are capable of operating independently of each other. The controller  7  is capable of controlling the plurality of movable mirror elements  3  independently of each other. Therefore, the controller  7  can change the number of rows of the movable mirrors  20  included in each of the plurality of first movable mirror arrays  4  so as to change the period d of the plurality of first movable mirror arrays  4 . The controller  7  can change the number of rows of the movable mirrors  20  included in each of the plurality of second movable mirror arrays  5  so as to change the period d of the plurality of second movable mirror arrays  5 . Specifically, although in the example illustrated in  FIG.  2   , the number of rows of the movable mirrors  20  included in each of the plurality of first movable mirror arrays  4  is two, the number of rows of the movable mirrors  20  included in each of the plurality of first movable mirror arrays  4  may be changed to one or three or more. Although in the example illustrated in  FIG.  2   , the number of rows of the movable mirrors  20  included in each of the plurality of second movable mirror arrays  5  is two, the number of rows of the movable mirrors  20  included in each of the plurality of second movable mirror arrays  5  may be changed to one or three or more. 
     Changing the period d of the plurality of first movable mirror arrays  4  and the period d of the plurality of second movable mirror arrays  5  makes it possible to change the diffraction angle θ of the light beam diffracted by the plurality of movable mirror elements  3 , that is, the deflection angle of the optical scanning device  1 , which makes it possible to change an area to be optically scanned by the optical scanning device  1 . 
     With reference to  FIG.  7   , an absolute value u of the difference between the first vertical displacement amount and the second vertical displacement amount may be given by the following equation (2). “λ” represents the wavelength of the light beam  40  incident on the plurality of movable mirror elements  3 , and “n” represents zero or a natural number. Therefore, the light beam  40  can be prevented from being (perpendicularly) reflected toward the incident direction (the third direction (z direction)) of the light beam  40  in the diffraction grating formed by the plurality of movable mirror elements  3 . 
         u =(¼+ n/ 2)λ  (2)
 
     The plurality of movable mirror elements  3  are capable of operating independently of each other. The controller  7  can control the plurality of movable mirror elements  3  independently of each other. Therefore, as illustrated in  FIGS.  2 ,  8  and  9   , in the plan view of the main surface  2   a  of the substrate  2 , the controller  7  can change the first longitudinal direction of each of the plurality of first movable mirror arrays  4  and the second longitudinal direction of each of the plurality of second movable mirror arrays  5  in a plane (a plane along the main surface  2   a  of the substrate  2 , i.e., an xy plane) defined by the first direction (x direction) and the second direction (y direction). The light beam diffracted by the plurality of movable mirror elements  3  can be scanned around an axis (z axis) parallel to the third direction (z direction). 
     As illustrated in  FIG.  7   , the absolute value u may satisfy the following equation (3). “W” represents an interval between a pair of first movable mirror arrays  4  adjacent to each other among the plurality of first movable mirror arrays  4 , and “0” represents a diffraction angle of a light beam diffracted by the plurality of movable mirror elements  3  (i.e., a deflection angle of the optical scanning device  1 ). Therefore, it is possible to block the diffraction light beam unnecessary for the optical scanning by using the first movable mirror array  4 . 
         u≥W /tan θ  (3)
 
     As illustrated in  FIG.  7   , the optical scanning device  1  further includes a light shielding member  43  that blocks one of the +1 order diffraction light beam  41  and the −1 order diffraction light beam  42  generated by the diffraction grating. For example, if the −1 order diffraction light beam  42  is not used for the optical scanning, the light shielding member  43  blocks the −1 order diffraction light beam  42 . The light shielding member  43  may be, for example, a light absorbing member. 
     The light shielding member  43  may be an optical shutter. Depending on the application of the optical scanning device  1 , the −1 order diffraction light beam  42  may not be required as the light beam for the optical scanning, or both the −1 order diffraction light beam  42  and the +1 order diffraction light beam  41  may be required as the light beam for the optical scanning. When the −1 order diffraction light beam  42  is not required as the light beam for the optical scanning, the optical shutter blocks the −1 order diffraction light beam  42 . When both the −1 order diffraction light beam  42  and the +1 order diffraction light beam  41  are required as the light beam for the optical scanning, the optical shutter allows the −1 order diffraction light beam  42  to pass therethrough. 
     The optical shutter may be, for example, a mechanical optical shutter or an electro-optical shutter. The electro-optical shutter is formed from, for example, a pair of polarizing plates and an electro-optical medium (for example, liquid crystal or lead lanthanum zirconate titanate (PLZT)) disposed between the pair of polarizing plates. 
     A method of manufacturing the optical scanning device  1  according to the first embodiment will be described with reference to  FIGS.  3 ,  5 ,  6 , and  10  to  16   . The method of manufacturing the optical scanning device  1  according to the first embodiment includes a first step of forming a first structure including the substrate  2  and the beams  18   a  and  18   b  (see  FIGS.  6  and  10  to  12   ), a second step of forming a second structure including the mirror film  22  and the pillar  23  (see  FIGS.  13  and  14   ), and a third step of bonding the second structure to the first structure (see  FIGS.  3 ,  5 ,  6 ,  15  and  16   ). The first step may be performed before the second step or after the second step. 
     The first step of forming a first structure including the substrate  2  and the beams  18   a  and  18   b  will be described with reference to  FIGS.  6  and  10  to  12   . 
     With reference to  FIG.  10   , the substrate  2  is prepared. In the present embodiment, the substrate  2  includes a conductive substrate  10  and a first insulating film  11  provided on the conductive substrate  10 . The conductive substrate  10  is, for example, a silicon substrate containing a dopant. The first insulating film  11  is, for example, a silicon nitride film, a silicon dioxide film, or a laminated film of a silicon nitride film and a silicon dioxide film. The first insulating film  11  is formed on the conductive substrate  10  by plasma-enhanced chemical vapor deposition (PECVD), for example. The substrate  2  may be an insulating substrate. 
     As illustrated in  FIGS.  6  and  10   , the electrodes  12   a ,  12   b ,  12   c ,  12   d  and  14  and the wirings  13   a ,  13   b ,  13   c ,  13   d  and  15  are formed on the main surface  2   a  (or the first insulating film  11 ) of the substrate  2 . 
     Specifically, a conductive film is formed on the main surface  2   a  (or the first insulating film  11 ) of the substrate  2 . The conductive film is made of conductive polysilicon or a metal such as aluminum, gold or platinum. When the conductive film is made of conductive polysilicon, the conductive film is formed on the main surface  2   a  of the substrate  2  by, for example, a low pressure chemical vapor deposition (LPCVD) method. When the conductive film is made of a metal such as aluminum, gold or platinum, the conductive film is formed on the main surface  2   a  of the substrate  2  by, for example, a sputtering method. When the substrate  2  is an insulating substrate, the conductive film may be formed directly on the insulating substrate. The conductive substrate  10 , the first insulating film  11  and the conductive film may constitute a silicon-on-insulator substrate (SOI substrate). When the conductive substrate  10 , the first insulating film  11  and the conductive film constitute an SOI substrate, the conductive film is made of a conductive silicon film having a high dopant concentration. 
     Then, the conductive film is patterned to form the electrodes  12   a ,  12   b ,  12   c ,  12   d  and  14  and the wirings  13   a ,  13   b ,  13   c ,  13   d  and  15 . Specifically, a resist (not shown) is formed on a part of the conductive film where the electrodes  12   a ,  12   b ,  12   c ,  12   d  and  14  and the wirings  13   a ,  13   b ,  13   c ,  13   d  and  15  are to be formed. The remaining part of the conductive film which is exposed from the resist is etched by a reactive ion etching (RIB) method such as an inductively coupled plasma reactive ion etching (ICP-RIE) method. The resist is removed by, for example, an oxygen ashing method. 
     As illustrated in  FIG.  11   , a sacrificial layer  30  is formed on the electrode  12   a ,  12   b ,  12   c ,  12   d  and  14 , the wiring  13   a ,  13   b ,  13   c ,  13   d  and  15 , and the main surface  2   a  of the substrate  2 . The sacrificial layer  30  is made of, for example, phosphosilicate glass (PSG). The sacrificial layer  30  is formed by, for example, the LPCVD. The sacrificial layer  30  has a thickness of, for example, 0.01 μm or more and 20 μm or less. 
     As illustrated in  FIG.  11   , a hole  31  is formed in the sacrificial layer  30  by removing a portion of the sacrificial layer  30 . The hole  31  is formed in a portion of the sacrificial layer  30  corresponding to each of the electrodes  12   a ,  12   b ,  12   c  and  12   d . Each of the electrodes  12   a ,  12   b ,  12   c  and  12   d  in the corresponding hole  31  is exposed from the sacrificial layer  30 . Specifically, a resist (not shown) is formed on the sacrificial layer  30 . The resist is formed with holes (not shown). A part of the sacrificial layer  30  which is located in each hole of the resist and is exposed from the resist is removed by, for example, a dry etching method such as the RIE method or a wet etching method. The resist is removed by, for example, an oxygen ashing method. 
     As illustrated in  FIGS.  6  and  12   , the anchors  17   a ,  17   b ,  17   c  and  17   d  and the beams  18   a  and  18   b  are formed. 
     Specifically, a film is formed on the surface of the sacrificial layer  30  and in each hole  31  of the sacrificial layer  30 . The film filled in each hole  31  of the sacrificial layer  30  corresponds to the anchor  17   a ,  17   b ,  17   c  and  17   d , respectively. The film is made of, for example, a conductive material such as conductive polysilicon. When the film is made of conductive polysilicon, the film is formed by, for example, the LPCVD. In order to planarize the film, the film may be subjected to chemical mechanical polishing (CMP), for example. Then, the film formed on the surface of the sacrificial layer  30  is patterned to form the beams  18   a  and  18   b . A part of the film is etched by an RIE method such as an ICP-RIE method. Thus, the first structure including the substrate  2  and the beams  18   a  and  18   b  is obtained. 
     The second step of forming the second structure including the mirror film  22  and the pillar  23  will be described with reference to  FIGS.  13  and  14   . 
     With reference to  FIG.  13   , a silicon-on-insulator substrate (an SOI substrate  36 ) is prepared. The SOI substrate  36  includes a silicon substrate  33 , an insulating film  34  provided on the silicon substrate  33 , and a silicon layer  35  provided on the insulating film  34 . The silicon substrate  33  has a thickness of, for example, 10 μm or more and 1000 μm or less. The insulating film  34  has a thickness of, for example, 0.01 μm or more and 2.0 μm or less. The silicon layer  35  has a thickness of, for example, 1.0 μm or more and 100 μm or less. The silicon substrate  33  may be electrically conductive. The silicon layer  35  may be electrically conductive. The insulating film  34  is disposed between the silicon substrate  33  and the silicon layer  35  so as to electrically insulate the silicon substrate  33  from the silicon layer  35 . 
     As illustrated in  FIG.  13   , the mirror film  22  is formed on the SOI substrate  36 . 
     Specifically, a reflective film is formed on the SOI substrate  36 . The reflective film is formed on the silicon layer  35  by a sputtering method, for example. The reflective film has a thickness of, for example, 0.01 μm or more and 1.0 μm or less. The reflective film is, for example, a Cr/Ni/Au film or a Ti/Pt/Au film. The Cr film and the Ti film improve adhesion of the mirror film  22  to the silicon layer  35 . Since the uppermost layer of the reflective film is an Au film, the reflective film has a high reflectivity for the light beam incident on the optical scanning device  1 . Then, the reflective film is patterned to form the mirror film  22 . A portion of the reflective film is removed by, for example, a wet etching method, a lift-off method, or an ion beam etching method. 
     As illustrated in  FIG.  14   , a part of the silicon substrate  33  is removed to form the pillar  23 . The part of the silicon substrate  33  may be removed by the ICP-RIE method, for example. A part of the insulating film  34  is removed to form the second insulating film  24 . The part of the insulating film  34  may be removed by the ICP-RIE method, for example. Thus, the second structure including the mirror film  22  and the pillar  23  is obtained. 
     The third step of bonding the second structure to the first structure will be described with reference to  FIGS.  3 ,  5 ,  6 ,  15  and  16   . 
     As illustrated in  FIG.  15   , the pillar  23  is bonded to the beams  18   a  and  18   b . The pillar  23  is bonded to the beams  18   a  and  18   b  by, for example, a room temperature bonding method or a plasma surface activation bonding method. The pillar  23  is opposed to the electrode  14  in the third direction (z direction). 
     As illustrated in  FIG.  16   , a part of the silicon layer  35  is removed to form the movable plate  21 . The part of the silicon layer  35  may be removed by the ICP-RIE method, for example. 
     Then, the sacrificial layer  30  is removed by a wet etching method or a dry etching method using hydrofluoric acid or the like. Thus, the optical scanning device  1  illustrated in  FIGS.  3 ,  5  and  6    is obtained. 
     A modification of the present embodiment will be described with reference to  FIGS.  17  to  19   . In the modification of the present embodiment, the movable mirror  20  has a regular triangular shape in a plan view of the main surface  2   a  of the substrate  2 . Therefore, it is easy to perform an optical scanning with a light beam in a plurality of directions different from each other by 60° in a plane (a plane along the main surface  2   a  of the substrate  2 , i.e., an xy plane) defined by the first direction (x direction) and the second direction (y direction). In the plan view of the main surface  2   a  of the substrate  2 , the movable mirror  20  may have a regular hexagon shape or a regular octagon shape. 
     Effects of the optical scanning device  1  of the present embodiment will be described. 
     The optical scanning device  1  of the present embodiment includes a substrate  2  and a plurality of movable mirror elements  3 . The substrate  2  includes a main surface  2   a  that extends in a first direction (x direction) and a second direction (y direction) perpendicular to the first direction (x direction). The plurality of movable mirror elements  3  are two-dimensionally arranged on the main surface  2   a  of the substrate  2  in a plan view of the main surface  2   a  of the substrate  2 . The plurality of movable mirror elements  3  are capable of operating independently of each other and capable of forming a diffraction grating. Each of the plurality of movable mirror elements  3  includes a beam (for example, a beam  18   a ), a first anchor (for example, an anchor  17   a ), a second anchor (for example, an anchor  17   a ), a movable mirror  20 , and a pillar  23 . The beam is bendable in a third direction (z direction) perpendicular to the main surface  2   a  of the substrate  2 . The first anchor is provided on the main surface  2   a  of the substrate  2  to support the first end of the beam. The second anchor is provided on the main surface  2   a  of the substrate  2  to support the second end of the beam opposite to the first end. The movable mirror  20  includes a movable plate  21  separated from the beam in the third direction (z direction), and a mirror film  22  provided on the movable plate  21 . The pillar  23  connects the movable plate  21  to a portion of the beam other than the first end and the second end to each other. 
     In the optical scanning device  1 , the light beam  40  incident on the optical scanning device  1  is received by the movable mirrors  20  of the plurality of movable mirror elements  3 . Thus, it is possible to reduce the size and mass of each movable mirror  20 , which makes it possible to move each movable mirror  20  at a higher speed. Therefore, it is possible for the optical scanning device  1  to perform an optical scanning with a light beam at a higher speed. Further, in the optical scanning device  1 , the light beam  40  incident on the optical scanning device  1  is deflected by a diffraction grating formed from a plurality of movable mirror elements  3  capable of operating independently of each other. Therefore, it is possible for the optical scanning device  1  to perform an optical scanning with a light beam at a larger deflection angle. 
     Since the beam (for example, the beam  18   a ) is bendable in the third direction (z direction) perpendicular to the main surface  2   a  of the substrate  2 , it is possible for the movable mirror  20  connected to the beam to move in the third direction (z direction). Therefore, it is possible to move the movable mirror  20  without twisting the beam, which makes it possible to prevent torsional rupture of the beam when the movable mirror  20  is driven to move. Therefore, the optical scanning device  1  has a longer lifetime. Further, according to the optical scanning device  1 , it is possible to perform an optical scanning with a light beam at a larger deflection angle without setting the driving frequency of the movable mirror  20  to the resonance frequency of the movable mirror  20 . Therefore, the optical scanning device  1  can perform an optical scanning with a light beam at a larger deflection angle more stably regardless of the driving frequency of the movable mirror  20 . 
     The optical scanning device  1  according to the present embodiment further includes a controller  7  that controls a vertical displacement amount of the movable mirror  20  in the third direction (z direction). The controller  7  constructs a plurality of first movable mirror arrays  4  and a plurality of second movable mirror arrays  5  from the plurality of movable mirror elements  3 . The plurality of first movable mirror arrays  4  are constructed from a part of the plurality of movable mirror elements  3  in which the vertical displacement amount of the movable mirror  20  is a first vertical displacement amount. The plurality of second movable mirror arrays  5  are constructed from the remaining part of the plurality of movable mirror elements  3  in which the vertical displacement amount of the movable mirror  20  is a second vertical displacement amount which is larger than the first vertical displacement amount. In the plan view of the main surface  2   a  of the substrate  2 , the first longitudinal direction of each of the plurality of first movable mirror arrays  4  is parallel to the second longitudinal direction of each of the plurality of second movable mirror arrays  5 . The plurality of first movable mirror arrays  4  and the plurality of second movable mirror arrays  5  are arranged alternately and periodically in a direction perpendicular to the first longitudinal direction. In the plan view of the main surface  2   a  of the substrate  2 , the controller  7  is capable of changing the first longitudinal direction and the second longitudinal direction. 
     Therefore, it is possible for the optical scanning device  1  to perform an optical scanning with a light beam around an axis parallel to the third direction (z direction) at a higher speed. 
     In the optical scanning device  1  of the present embodiment, the absolute value u of the difference between the first vertical displacement amount and the second vertical displacement amount is given by the following equation (4). “λ” represents the wavelength of the light beam incident on the plurality of movable mirror elements  3 , and “n” represents zero or a natural number. 
         u =(¼+ n/ 2)λ  (4)
 
     Therefore, the light beam  40  be prevented from being (perpendicularly) reflected toward the incident direction (the third direction (z direction)) of the light beam  40  by the diffraction grating formed from the plurality of movable mirror elements  3 . 
     In the optical scanning device  1  of the present embodiment, the absolute value u satisfies the following equation (5). “W” represents an interval between a pair of first movable mirror arrays  4  adjacent to each other among the plurality of first movable mirror arrays  4 , and “θ” represents a diffraction angle of a light beam diffracted by the plurality of movable mirror elements  3 . 
         u≥W /tan θ  (5)
 
     Therefore, it is possible to block the diffraction light beam that is not required for the optical scanning by using the first movable mirror array  4 . 
     The optical scanning device  1  of the present embodiment further includes a light shielding member  43  that blocks one of a pair of diffraction light beams generated by the diffraction grating. Therefore, it is possible to block the diffraction light beam that is not required for the optical scanning. 
     In the optical scanning device  1  of the present embodiment, the light shielding member  43  is an optical shutter. Therefore, one of the pair of diffraction beam beams is blocked or transmitted depending on the application of the optical scanning device  1 . It is possible to expand the application of the optical scanning device  1 . 
     In the optical scanning device  1  of the present embodiment, the beam (for example, the beam  18   a ) is electrically conductive. Each of the plurality of movable mirror elements  3  includes a first electrode (for example, the electrode  12   a ) and a second electrode (for example, the electrode  12   b ). The first electrode and the second electrode are provided on the main surface  2   a  of the substrate  2 , and are electrically insulated from each other. The first electrode is electrically connected to the beam. The second electrode is opposed to the pillar  23  and a portion of the beam in the third direction (z direction). 
     Therefore, the beam (for example, the beam  18   a ) is driven in accordance with a voltage applied between the first electrode (for example, the electrode  12   a ) and the second electrode (for example, the electrode  12   b ), which makes it possible for the optical scanning device  1  to perform an optical scanning with a light beam at a higher speed and a larger deflection angle. 
     Second Embodiment 
     An optical scanning device  1   b  according to a second embodiment will be described with reference to  FIGS.  20  and  21   . The optical scanning device  1   b  of the present embodiment has substantially the same configuration as the optical scanning device  1  of the first embodiment, but is different from the optical scanning device  1  of the first embodiment mainly on the following points. 
     The optical scanning device  1   b  further includes magnets  51  and  52 . The magnets  51  and  52  are, for example, permanent magnets or electromagnets. The magnets  51  and  52  are provided on both sides of the substrate  2  in the first direction (x direction). The substrate  2  is sandwiched between the magnet  51  and the magnet  52  in the first direction (x direction). The magnets  51  and  52  generate a magnetic field along the main surface  2   a  of the substrate  2  on the beam  18   a . Specifically, the magnets  51  and  52  generate a magnetic field in the direction (the first direction (x direction)) along the main surface  2   a  of the substrate  2  which is perpendicular to the longitudinal direction (the second direction (y direction)) of the beam  18   a  on a portion of the beam  18   a  connected to the pillar  23 . 
     The optical scanning device  1   b  may further include magnets  53  and  54 . The magnets  53  and  54  are, for example, permanent magnets or electromagnets. The magnets  53  and  54  are provided on both sides of the substrate  2  in the second direction (y direction). The substrate  2  is sandwiched between the magnet  53  and the magnet  54  in the second direction (y direction). The magnets  53  and  54  generate a magnetic field along the main surface  2   a  of the substrate  2  on the beam  18   b . Specifically, the magnets  53  and  54  generate a magnetic field in the direction (the second direction (y direction)) along the main surface  2   a  of the substrate  2  which is perpendicular to the longitudinal direction (the first direction (x direction)) of the beam  18   b  on a portion of the beam  18   b  connected to the pillar  23 . 
     With reference to  FIG.  21   , the wiring  13   a  is connected to the electrode  12   a , and is configured to supply a current to the electrode  12   a . The wiring  13   b  is connected to the electrode  12   b , and is configured to supply a current to the electrode  12   b . The wiring  13   c  is connected to the electrode  12   c , and is configured to supply a current to the electrode  12   c . The wiring  13   d  is connected to the electrode  12   d , and is configured to supply a current to the electrode  12   d . Different from the plurality of movable mirror elements  3  of the first embodiment, the plurality of movable mirror elements  3   b  of the present embodiment do not include the electrode  14  and the wiring  15 . 
     As illustrated in  FIG.  20   , the controller  7   b  includes at least one of a current control unit  8   b  or a magnetic field control unit  9   b.    
     The current control unit  8   b  is connected to the electrode  12   a  and the electrode  12   b  via the wiring  13   a  and the wiring  13   b . The current control unit  8   b  is connected to the electrode  12   c  and the electrode  12   d  via the wirings  13   c  and  13   d . The electrode  12   a  is electrically connected to the first end of the beam  18   a  via the anchor  17   a . The electrode  12   b  is electrically connected to the second end of the beam  18   a  opposite to the first end of the beam  18   a  via the anchor  17   b . The electrode  12   c  is electrically connected to the third end of the beam  18   b  via the anchor  17   c . The electrode  12   d  is electrically connected to the fourth end of the beam  18   b  opposite to the third end of the beam  18   b  via the anchor  17   d . The beams  18   a  and  18   b  are electrically conductive. The current control unit  8   b  controls a current flowing through the beam  18   a  electrically connected to the electrode  12   a  and the electrode  12   b . The current control unit  8   b  controls a current flowing through the beam  18   b  electrically connected to the electrode  12   c  and the electrode  12   d.    
     When the magnets  51  and  52  are electromagnets, the magnetic field control unit  9   b  controls the magnets  51  and  52  so as to control the magnetic field to be formed by the magnets  51  and  52  on the beam  18   a . When the magnets  53  and  54  are electromagnets, the magnetic field control unit  9   b  controls the magnets  53  and  54  so as to control the magnetic field generated by the magnets  53  and  54  on the beam  18   b . Thus, the controller  7   b  can control the vertical displacement amount of the movable mirror  20  in the third direction (z direction). 
     As a first example, when the magnets  51  and  52  are permanent electromagnets, the current control unit  8   b  supplies a zero current to the beam  18   a . No Lorentz force acts on the beam  18   a . The beam  18   a  is not bent, and thereby the first vertical displacement amount of the movable mirror  20  is zero. Thus, it is possible to realize the movable mirror elements  3   b  in which the vertical displacement amount of the movable mirror  20  is the first vertical displacement amount. On the other hand, when the current control unit  8   b  supplies a non-zero current to the beam  18   a , a Lorentz force acts on the beam  18   a . The beam  18   a  is bent toward the main surface  2   a  of the substrate  2 , and the second vertical displacement amount of the movable mirror  20  is larger than the first vertical displacement amount. Thus, it is possible to realize the movable mirror elements  3   b  in which the vertical displacement amount of the movable mirror  20  is the second vertical displacement amount. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     As a second example, when the magnets  51  and  52  are electromagnets, the current control unit  8   b  supplies a current to the beam  18   a , and the magnetic field control unit  9   b  turns off the magnets  51  and  52 . Since no magnetic field is generated by the magnets  51  and  52  on the beam  18   a , no Lorentz force acts on the beam  18   a . The beam  18   a  is not bent, and thereby the first vertical displacement amount of the movable mirror  20  is zero. Thus, it is possible to realize the movable mirror elements  3   b  in which the vertical displacement amount of the movable mirror  20  is the first vertical displacement amount. On the other hand, the current control unit  8   b  supplies a current to the beam  18   a , and the magnetic field control unit  9   b  turns on the magnets  51  and  52 . Since a magnetic field is generated by the magnets  51  and  52  on the beam  18   a , a Lorentz force acts on the beam  18   a . The beam  18   a  is bent toward the main surface  2   a  of the substrate  2 , and thereby the second vertical displacement amount of the movable mirror  20  is larger than the first vertical displacement amount. Thus, it is possible to realize the movable mirror elements  3   b  in which the vertical displacement amount of the movable mirror  20  is the second vertical displacement amount. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     The optical scanning device  1   b  according to the present embodiment has the following effects in addition to the effects of the optical scanning device  1  according to the first embodiment. 
     The optical scanning device  1   b  of the present embodiment further includes a first magnet (for example, at least one of the magnets  51  and  52 ) that generates a first magnetic field along the main surface  2   a  of the substrate  2  on a beam (for example, the beam  18   a ). The beam is electrically conductive. Each of the plurality of movable mirror elements  3   b  includes a first electrode (for example, the electrode  12   a ) and a second electrode (for example, the electrode  12   b ). The first electrode and the second electrode are provided on the main surface  2   a  of the substrate  2 , and are separated from each other. The first electrode is electrically connected to the first end of the beam. The second electrode is electrically connected to the second end of the beam. 
     Therefore, the beam is driven in accordance with the current flowing through the beam (for example, the beam  18   a ) and the first magnetic field formed on the beam by the first magnet (for example, at least one of the magnets  51  and  52 ), which makes it possible for the optical scanning device  1   b  to perform an optical scanning with a light beam at a higher speed and a larger deflection angle. 
     Third Embodiment 
     An optical scanning device  1   c  according to a third embodiment will be described with reference to  FIGS.  1  and  22   . The optical scanning device  1   c  of the present embodiment has substantially the same configuration as the optical scanning device  1  of the first embodiment, but is different from the optical scanning device  1  of the first embodiment mainly on the following points. 
     The plurality of movable mirror elements  3   c  include piezoelectric films  61  and  62 . The plurality of movable mirror elements  3   c  may further include piezoelectric films  63  and  64 . The piezoelectric films  61 ,  62 ,  63 ,  64  are made of, for example, lead zirconate titanate (PZT), barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), or zinc oxide (ZnO). 
     The piezoelectric films  61  and  62  are provided on the beam  18   a . Specifically, the piezoelectric films  61  and  62  are provided on a front surface of the beam  18   a  opposite to a back surface of the beam  18   a  opposed to the main surface  2   a  of the substrate  2 . The piezoelectric film  61  is provided on a portion of the beam  18   a  that is located closer to the electrode  12   a  or the anchor  17   a  than a portion of the beam  18   a  (for example, a central portion of the beam  18   a ) connected to the pillar  23 . The piezoelectric film  62  is provided on a portion of the beam  18   a  that is located closer to the electrode  12   b  or the anchor  17   b  than a portion of the beam  18   a  (for example, a central portion of the beam  18   a ) connected to the pillar  23 . The piezoelectric film  63  is provided on a portion of the beam  18   b  that is located closer to the electrode  12   c  or the anchor  17   c  than a portion of the beam  18   b  (for example, a central portion of the beam  18   b ) connected to the pillar  23 . The piezoelectric film  64  is provided on a portion of the beam  18   b  that is located closer to the electrode  12   d  or the anchor  17   d  than a portion of the beam  18   b  (for example, a central portion of the beam  18   b ) connected to the pillar  23 . 
     Different from the plurality of movable mirror elements  3   c  of the first embodiment, the plurality of movable mirror elements  3   c  of the present embodiment do not include the electrode  14  and the wiring  15 . 
     The controller  7   c  includes a voltage control unit  8   c . The voltage control unit  8   c  is connected to the electrode  12   a  and the electrode  12   b  via the wiring  13   a  and the wiring  13   b . The voltage control unit  8   c  is connected to the electrode  12   c  and the electrode  12   d  via the wirings  13   c  and  13   d . The piezoelectric film  61  is electrically connected to the electrode  12   a  via the anchor  17   a  and the beam  18   a . The piezoelectric film  62  is electrically connected to the electrode  12   b  via the anchor  17   b  and the beam  18   a . The piezoelectric film  63  is electrically connected to the electrode  12   c  via the anchor  17   c  and the beam  18   b . The piezoelectric film  64  is electrically connected to the electrode  12   d  via the anchor  17   d  and the beam  18   b.    
     The voltage control unit  8   c  controls the voltage of the piezoelectric film  61  electrically connected to the electrode  12   a . The voltage control unit  8   c  controls the voltage of the piezoelectric film  62  electrically connected to the electrode  12   b . The voltage control unit  8   c  controls the voltage of the piezoelectric film  63  electrically connected to the electrode  12   c . The voltage control unit  8   c  controls the voltage of the piezoelectric film  64  electrically connected to the electrode  12   d . Thus, the controller  7   c  can control the vertical displacement amount of the movable mirror  20  in the third direction (z direction). 
     For example, the voltage control unit  8   c  applies a zero voltage to the piezoelectric films  61  and  62 . The beam  18   a  is not bent, and thereby the first vertical displacement amount of the movable mirror  20  is zero. Thus, it is possible to realize the movable mirror elements  3   c  in which the vertical displacement amount of the movable mirror  20  is the first vertical displacement amount. On the other hand, the voltage control unit  8   c  applies a non-zero voltage to the piezoelectric films  61  and  62 . The beam  18   a  is bent toward the main surface  2   a  of the substrate  2 , and thereby the second vertical displacement amount of the movable mirror  20  is larger than the first vertical displacement amount. Those described above with respect to the beam  18   a  also applies to the beam  18   b . Thus, it is possible to realize the movable mirror elements  3   c  in which the vertical displacement amount of the movable mirror  20  is the second vertical displacement amount. 
     The optical scanning device  1   c  according to the present embodiment has the following effects in addition to the effects of the optical scanning device  1  according to the first embodiment. 
     In the optical scanning device  1   c  of the present embodiment, the plurality of movable mirror elements  3   c  include a piezoelectric film (for example, at least one of the piezoelectric films  61  and  62 ) provided on a beam (for example, the beam  18   a ). Therefore, the beam is driven in accordance with the voltage applied to the piezoelectric film, which makes it possible for the optical scanning device  1   c  to perform an optical scanning with a light beam at a higher speed and a larger deflection angle. 
     Fourth Embodiment 
     An optical scanning device  1   d  according to a fourth embodiment will be described with reference to  FIGS.  1  and  23   . The optical scanning device  1   d  of the present embodiment has substantially the same configuration as the optical scanning device  1  of the first embodiment, but is different from the optical scanning device  1  of the first embodiment mainly on the following points. 
     The optical scanning device  1   d  further includes an in-plane driving unit  70  that drives the beams  18   a  and  18   b  to move in at least one direction of the first direction (x direction) or the second direction (y direction). The in-plane driving unit  70  includes comb-shaped electrodes  71   a  and  71   b  and comb-shaped electrodes  74   a  and  74   b.    
     Each of the plurality of movable mirror elements  3   d  includes comb-shaped electrodes  71   a  and  71   b , wirings  72   a  and  72   b , driving electrodes  73   a  and  73   b , and comb-shaped electrodes  74   a  and  74   b . The wirings  72   a  and  72   b  are provided on the main surface  2   a  of the substrate  2 . The wirings  72   a  and  72   b  are made of, for example, the same material as the wiring  13   a ,  13   b ,  13   c ,  13   d  or  15 . The wirings  72   a  and  72   b  are formed by the same step as the step of forming the wiring  13   a ,  13   b ,  13   c ,  13   d  or  15 , for example. 
     The driving electrode  73   a  is provided on the main surface  2   a  of the substrate  2  via the wiring  72   a . The driving electrode  73   a  may be made of the same material as the anchor  17   a , for example. The driving electrode  73   b  is provided on the main surface  2   a  of the substrate  2  via the wiring  72   b . The driving electrodes  73   a  and  73   b  may be made of the same material as the anchor  17   b , for example. The driving electrodes  73   a  and  73   b  are formed by the same step as the step of forming the anchors  17   a  and  17   b , for example. 
     The comb-shaped electrode  74   a  is provided on the driving electrode  73   a . The comb-shaped electrode  74   a  protrudes in the first direction (x direction) from a side surface of the driving electrode  73   a . The comb-shaped electrode  74   b  is provided on the driving electrode  73   b . The comb-shaped electrode  74   b  protrudes in the first direction (x direction) from a side surface of the driving electrode  73   b . The comb-shaped electrodes  74   a  and  74   b  are made of the same material as the beam  18   a , for example. The comb-shaped electrodes  74   a  and  74   b  are formed by the same step as the step of forming the beam  18   a , for example. The comb-shaped electrodes  74   a  and  74   b  function as fixed comb-shaped electrodes. 
     The comb-shaped electrode  71   a  is provided on the beam  18   a . Specifically, the comb-shaped electrode  71   a  is provided on a portion of the beam  18   a  that is located closer to the electrode  12   a  or the anchor  17   a  than a portion of the beam  18   a  (for example, a central portion of the beam  18   a ) connected to the pillar  23 . The comb-shaped electrode  71   a  protrudes in the first direction (x direction) from a first side surface of the beam  18   a . The comb-shaped electrode  71   b  is provided on the beam  18   a . Specifically, the comb-shaped electrode  71   b  is provided on a portion of the beam  18   a  that is located closer to the electrode  12   b  or the anchor  17   b  than the portion of the beam  18   a  (for example, the central portion of the beam  18   a ) connected to the pillar  23 . The comb-shaped electrode  71   b  protrudes in the first direction (x direction) from a second side surface of the beam  18   a  opposite to the first side surface of the beam  18   a . The comb-shaped electrodes  71   a  and  71   b  are made of the same material as the beam  18   a , for example. The comb-shaped electrodes  71   a  and  71   b  are formed by the same step as the step of forming the beam  18   a , for example. The comb-shaped electrodes  71   a  and  71   b  function as movable comb-shaped electrodes. 
     The comb-shaped electrode  71   a  and the comb-shaped electrode  74   a  are opposed to each other. The comb-shaped electrode  71   b  and the comb-shaped electrode  74   b  are opposed to each other. 
     The in-plane driving unit  70  may further include comb-shaped electrodes  71   c  and  71   d  and comb-shaped electrodes  74   c  and  74   d.    
     Each of the plurality of movable mirror elements  3   d  further includes comb-shaped electrodes  71   c  and  71   d , wirings  72   c  and  72   d , driving electrodes  73   c  and  73   d , and comb-shaped electrodes  74   c  and  74   d . The wirings  72   c  and  72   d  are provided on the main surface  2   a  of the substrate  2 . The wirings  72   c  and  72   d  are made of, for example, the same material as the wiring  13   a ,  13   b ,  13   c ,  13   d  and  15 . The wirings  72   c  and  72   d  are formed by the same step as the step of forming the wiring  13   a ,  13   b ,  13   c ,  13   d  and  15 , for example. 
     The driving electrode  73   c  is provided on the main surface  2   a  of the substrate  2  via the wiring  72   c . The driving electrode  73   c  may be made of the same material as the anchor  17   c , for example. The driving electrode  73   d  is provided on the main surface  2   a  of the substrate  2  via the wiring  72   d . The driving electrodes  73   c  and  73   d  may be made of the same material as the anchor  17   d , for example. The driving electrodes  73   c  and  73   d  are formed by the same step as the step of forming the anchors  17   c  and  17   d , for example. 
     The comb-shaped electrode  74   c  is provided on the driving electrode  73   c . The comb-shaped electrode  74   c  protrudes in the second direction (y direction) from a side surface of the driving electrode  73   c . The comb-shaped electrode  74   d  is provided on the driving electrode  73   d . The comb-shaped electrode  74   d  protrudes in the second direction (y direction) from a side surface of the driving electrode  73   d . The comb-shaped electrodes  74   c  and  74   d  are made of the same material as the beam  18   b , for example. The comb-shaped electrodes  74   c  and  74   d  are formed by the same step as the step of forming the beam  18   b , for example. The comb-shaped electrodes  74   c  and  74   d  function as fixed comb-shaped electrodes. 
     The comb-shaped electrode  71   c  is provided on the beam  18   b . Specifically, the comb-shaped electrode  71   c  is provided on a portion of the beam  18   b  that is located closer to the electrode  12   c  or the anchor  17   c  than a portion of the beam  18   b  (for example, a central portion of the beam  18   b ) connected to the pillar  23 . The comb-shaped electrode  71   c  protrudes in the second direction (y direction) from a third side surface of the beam  18   b . The comb-shaped electrode  71   d  is provided on the beam  18   b . Specifically, the comb-shaped electrode  71   d  is provided on a portion of the beam  18   b  that is located closer to the electrode  12   d  or the anchor  17   d  than the portion of the beam  18   b  (for example, the central portion of the beam  18   b ) connected to the pillar  23 . The comb-shaped electrode  71   d  protrudes in the second direction (y direction) from a fourth side surface of the beam  18   b  opposite to the third side surface of the beam  18   b . The comb-shaped electrodes  71   c  and  71   d  are made of the same material as the beam  18   b , for example. The comb-shaped electrodes  71   c  and  71   d  are formed by the same step as the step of forming the beam  18   b , for example. The comb-shaped electrodes  71   c  and  71   d  function as movable comb-shaped electrodes. 
     The comb-shaped electrode  71   c  and the comb-shaped electrode  74   c  are opposed to each other. The comb-shaped electrode  71   d  and the comb-shaped electrode  74   d  are opposed to each other. 
     The controller  7   d  includes a voltage control unit  8   d . The voltage control unit  8   d  of the present embodiment is similar to the voltage control unit  8  of the first embodiment, but is different from the voltage control unit  8  of the first embodiment on the following points. 
     The voltage controller  8   d  further controls the voltage of the beam  18   a . The beam  18   a  is electrically conductive. Therefore, the voltage control unit  8   d  further controls the voltages of the comb-shaped electrodes  71   a  and  71   b  provided on the beam  18   a . The voltage controller  8   d  further controls the voltage of the beam  18   b . The beam  18   b  is electrically conductive. Therefore, the voltage control unit  8   d  further controls the voltages of the comb-shaped electrodes  71   c  and  71   d  provided on the beam  18   b.    
     The voltage control unit  8   d  is connected to the driving electrode  73   a  via the wiring  72   a . Therefore, the voltage control unit  8   d  further controls the voltage of the comb-shaped electrode  74   a . The voltage control unit  8   d  is connected to the driving electrode  73   b  via the wiring  72   b . Therefore, the voltage control unit  8   d  further controls the voltage of the comb-shaped electrode  74   b . The voltage control unit  8   d  is connected to the driving electrode  73   c  via the wiring  72   c . Therefore, the voltage control unit  8   d  further controls the voltage of the comb-shaped electrode  74   c . The voltage control unit  8   d  is connected to the driving electrode  73   d  via the wiring  72   d . Therefore, the voltage control unit  8   d  further controls the voltage of the comb-shaped electrode  74   d.    
     The voltage control unit  8   d  controls the voltage between the comb-shaped electrodes  71   a  and  74   a . The voltage control unit  8   d  controls the voltage between the comb-shaped electrodes  71   b  and  74   b . The voltage control unit  8   d  controls the voltage between the comb-shaped electrodes  71   c  and  74   c . The voltage control unit  8   d  controls the voltage between the comb-shaped electrodes  71   d  and  74   d . Thus, the controller  7   d  can control the horizontal displacement amount of the movable mirror  20  in the first direction (x direction) or the second direction (y direction). 
     For example, when the movable mirrors  20  of the plurality of movable mirror elements  3   d  are arranged as illustrated in  FIGS.  2  and  7   , the diffraction angle θ can be changed by changing the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction). 
     Specifically, the voltage control unit  8   d  controls the voltage between the comb-shaped electrode  71   a  and the comb-shaped electrode  74   a  to generate an electrostatic attractive force between the comb-shaped electrode  71   a  and the comb-shaped electrode  74   a , which causes the movable mirror  20  to move in the positive first direction (+x direction) together with the beam  18   a . On the other hand, the voltage control unit  8   d  controls the voltage between the comb-shaped electrode  71   b  and the comb-shaped electrode  74   b  to generate an electrostatic attractive force between the comb-shaped electrode  71   b  and the comb-shaped electrode  74   b , which causes the movable mirror  20  to move in the negative first direction (−x direction) together with the beam  18   a.    
     The movement amount of each movable mirror  20  in the first direction (x direction) is changed for each movable mirror  20 . Thus, the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) can be changed. For example, when the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) are made smaller, the diffraction angle θ becomes larger. When the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) are made larger, the diffraction angle θ becomes smaller. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     When the movable mirrors  20  of the plurality of movable mirror elements  3   d  are arranged as illustrated in  FIG.  9   , the diffraction angle θ can be changed by changing the period of the plurality of second movable mirror arrays  5  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction). 
     Specifically, the voltage control unit  8   d  controls the voltage between the comb-shaped electrode  71   c  and the comb-shaped electrode  74   c  to generate an electrostatic attractive force between the comb-shaped electrode  71   c  and the comb-shaped electrode  74   c , which causes the movable mirror  20  to move in the positive second direction (+y direction) together with the beam  18   b . On the other hand, the voltage control unit  8   d  controls the voltage between the comb-shaped electrode  71   d  and the comb-shaped electrode  74   d  to generate an electrostatic attractive force between the comb-shaped electrode  71   d  and the comb-shaped electrode  74   d , which causes the movable mirror  20  to move in the negative second direction (−y direction) together with the beam  18   b.    
     The movement amount of each movable mirror  20  in the second direction (y direction) is changed for each movable mirror  20 . Thus, the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) can be changed. For example, when the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) are made smaller, the diffraction angle θ becomes larger. When the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) are made larger, the diffraction angle θ becomes smaller. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     The optical scanning device  1   d  according to the present embodiment has the following effects in addition to the effects of the optical scanning device  1  according to the first embodiment. 
     The optical scanning device  1   d  of the present embodiment further includes an in-plane driving unit  70  that drives the beam (for example, the beam  18   a ) to move in at least one direction of the first direction (x direction) or the second direction (y direction). Therefore, it is possible to change the deflection angle of the optical scanning device  1   d , which makes it possible for the optical scanning device  1   d  to change the area to be optically scanned. 
     In the optical scanning device  1   d  of the present embodiment, the beam (for example, the beam  18   a ) is electrically conductive. The in-plane driving unit  70  includes a first comb-shaped electrode (for example, the comb-shaped electrode  71   a ) provided on the beam, a driving electrode (for example, the driving electrode  73   a ) provided on the main surface  2   a  of the substrate  2 , and a second comb-shaped electrode (for example, the comb-shaped electrode  74   a ) provided on the driving electrode. The first comb-shaped electrode and the second comb-shaped electrode are opposed to each other. 
     Therefore, it is possible to change the deflection angle of the optical scanning device  1   d  in accordance with the voltage applied between the first comb-shaped electrode and the second comb-shaped electrode, which makes it possible for the optical scanning device  1   d  to change the area to be optically scanned. 
     Fifth Embodiment 
     With reference to  FIGS.  24  and  25   , an optical scanning device  1   e  according to a fifth embodiment will be described. The optical scanning device  1   e  of the present embodiment has substantially the same configuration as the optical scanning device  1  of the first embodiment, but is different from the optical scanning device  1  of the first embodiment mainly on the following points. 
     The optical scanning device  1   e  further includes an in-plane driving unit  70   e  that drives the beams  18   a  and  18   b  to move in at least one direction of the first direction (x direction) or the second direction (y direction). The in-plane driving unit  70   e  includes a magnet  77 . The magnet  77  is, for example, a permanent magnet or an electromagnet. The magnet  77  is provided on a side distal to the movable mirror  20  with respect to the substrate  2 . The magnet  77  generates a magnetic field perpendicular to the main surface  2   a  of the substrate  2  on the beams  18   a  and  18   b . The magnet  77  generates a magnetic field along the third direction (z direction) on the beams  18   a  and  18   b.    
     The wiring  13   a  is connected to the electrode  12   a , and is configured to supply a voltage and a current to the electrode  12   a . The wiring  13   b  is connected to the electrode  12   b , and is configured to supply a voltage and a current to the electrode  12   b . The wiring  13   c  is connected to the electrode  12   c , and is configured to supply a voltage and a current to the electrode  12   c . The wiring  13   d  is connected to the electrode  12   d , and is configured to supply a voltage and a current to the electrode  12   d.    
     The electrode  12   a  is electrically connected to the first end of the beam  18   a  via the anchor  17   a . The electrode  12   b  is electrically connected to the second end of the beam  18   a  opposite to the first end of the beam  18   a  via the anchor  17   b . The electrode  12   c  is electrically connected to the third end of the beam  18   b  via the anchor  17   c . The electrode  12   d  is electrically connected to the fourth end of the beam  18   b  opposite to the third end of the beam  18   b  via the anchor  17   d.    
     As illustrated in  FIG.  24   , the controller  7   e  includes a voltage controller  8 , and at least one of a current control unit  8   b  or a magnetic field control unit  9   e.    
     The current control unit  8   b  of the present embodiment is the same as the current control unit  8   b  of the second embodiment. The current control unit  8   b  is connected to the electrode  12   a  and the electrode  12   b  via the wiring  13   a  and the wiring  13   b . The current control unit  8   b  is connected to the electrode  12   c  and the electrode  12   d  via the wirings  13   c  and  13   d . The current control unit  8   b  controls a current flowing through the beam  18   a  connected to the electrode  12   a  and the electrode  12   b . The current control unit  8   b  controls a current flowing through the beam  18   b  connected to the electrode  12   c  and the electrode  12   d . The beams  18   a  and  18   b  are electrically conductive. 
     When the magnet  77  is an electromagnet, the magnetic field control unit  9   e  controls the magnet  77  to control the magnetic field generated by the magnet  77  on the beams  18   a  and  18   b . Thus, the controller  7   e  can control the horizontal displacement amount of the movable mirror  20  in the first direction (x direction) or the second direction (y direction). 
     For example, when the movable mirrors  20  of the plurality of movable mirror elements  3   d  are arranged as illustrated in  FIGS.  2  and  7   , the diffraction angle θ can be changed by changing the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction). 
     As a first example, when the magnet  77  is a permanent electromagnet, the current control unit  8   b  supplies a zero current to the beam  18   a . No Lorentz force acts on the beam  18   a . The beam  18   a  is not bent, and thereby the movable mirror  20  does not move in the horizontal direction. The horizontal displacement amount of the movable mirror  20  is zero. On the other hand, when the current control unit  8   b  supplies a non-zero current to the beam  18   a , a Lorentz force acts on the beam  18   a . The direction of the Lorentz force acting on the beam  18   a  is the first direction (x direction) perpendicular to the longitudinal direction (the second direction (y direction)) of the beam  18   a  in the portion of the beam  18   a  to which the pillar  23  is connected and the direction (the third direction (z direction)) of the magnetic field generated by the magnet  77  on the beam  18   a . The beam  18   a  is bent in the first direction (x direction), and thereby the movable mirror  20  moves in the first direction (x direction). The horizontal displacement amount of the movable mirror  20  becomes non-zero. 
     As a second example, when the magnet  77  is an electromagnet, the current control unit  8   b  supplies a current to the beam  18   a , and the magnetic field control unit  9   e  turns off the magnet  77 . Since no magnetic field is generated by the magnet  77  on the beam  18   a , no Lorentz force acts on the beam  18   a . The beam  18   a  is not bent, and thereby the horizontal displacement amount of the movable mirror  20  is zero. On the other hand, the current control unit  8   b  supplies a current to the beam  18   a , and the magnetic field control unit  9   e  turns on the magnet  77 . Since a magnetic field is generated by the magnet  77  on the beam  18   a , a Lorentz force acts on the beam  18   a . The direction of the Lorentz force acting on the beam  18   a  is the first direction (x direction) perpendicular to the longitudinal direction (the second direction (y direction)) of the beam  18   a  in the portion of the beam  18   a  to which the pillar  23  is connected and the direction (the third direction (z direction)) of the magnetic field generated by the magnet  77  on the beam  18   a . The beam  18   a  is bent in the first direction (x direction), and thereby the movable mirror  20  moves in the first direction (x direction). The horizontal displacement amount of the movable mirror  20  becomes non-zero. 
     The movement amount of each movable mirror  20  in the first direction (x direction) is changed for each movable mirror  20 . Thus, the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) can be changed. For example, when the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) are made smaller, the diffraction angle θ becomes larger. When the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the first direction (x direction) are made larger, the diffraction angle θ becomes smaller. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     When the movable mirrors  20  of the plurality of movable mirror elements  3   d  are arranged as illustrated in  FIG.  9   , the diffraction angle θ can be changed by changing the period of the plurality of second movable mirror arrays  5  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction). 
     As a first example, when the magnet  77  is a permanent electromagnet, the current control unit  8   b  supplies a zero current to the beam  18   b . No Lorentz force acts on the beam  18   b . The beam  18   b  is not bent, and thereby the movable mirror  20  does not move in the horizontal direction. The horizontal displacement amount of the movable mirror  20  is zero. On the other hand, when the current control unit  8   b  supplies a non-zero current to the beam  18   b , a Lorentz force acts on the beam  18   b . The direction of the Lorentz force acting on the beam  18   b  is the second direction (y direction) perpendicular to the longitudinal direction (the first direction (x direction)) of the beam  18   b  in the portion of the beam  18   b  to which the pillar  23  is connected and the direction (the third direction (z direction)) of the magnetic field generated by the magnet  77  on the beam  18   a . The beam  18   b  is bent in the second direction (y direction), and thereby the movable mirror  20  moves in the second direction (y direction). The horizontal displacement amount of the movable mirror  20  becomes non-zero. 
     As a second example, when the magnet  77  is an electromagnet, the current control unit  8   b  supplies a current to the beam  18   b , and the magnetic field control unit  9   e  turns off the magnet  77 . Since no magnetic field is generated by the magnet  77  on the beam  18   b , no Lorentz force acts on the beam  18   b . The beam  18   b  is not bent, and thereby the horizontal displacement amount of the movable mirror  20  is zero. On the other hand, the current control unit  8   b  supplies a current to the beam  18   b , and the magnetic field control unit  9   e  turns on the magnet  77 . Since a magnetic field is generated by the magnet  77  on the beam  18   b , a Lorentz force acts on the beam  18   b . The direction of the Lorentz force acting on the beam  18   b  is the second direction (y direction) perpendicular to the longitudinal direction (the first direction (x direction)) of the beam  18   b  in the portion of the beam  18   b  to which the pillar  23  is connected and the direction (the third direction (z direction)) of the magnetic field generated by the magnet  77  on the beam  18   b . The beam  18   b  is bent in the second direction (y direction), and thereby the movable mirror  20  moves in the second direction (y direction). The horizontal displacement amount of the movable mirror  20  becomes non-zero. 
     The movement amount of each movable mirror  20  in the second direction (y direction) is changed for each movable mirror  20 . Thus, the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) can be changed. For example, when the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) are made smaller, the diffraction angle θ becomes larger. When the period of the plurality of first movable mirror arrays  4  and the period of the plurality of second movable mirror arrays  5  in the second direction (y direction) are made larger, the diffraction angle θ becomes smaller. Those described above with respect to the beam  18   a  also applies to the beam  18   b.    
     The optical scanning device  1   e  according to the present embodiment has the following effects in addition to the effects of the optical scanning device  1  according to the first embodiment. 
     In the optical scanning device  1   e  of the present embodiment, the in-plane driving unit  70   e  includes a second magnet (for example, the magnet  77 ) that generates a second magnetic field perpendicular to the main surface  2   a  of the substrate  2  on the beam (for example, the beam  18   a ). The beam is electrically conductive. Each of the plurality of movable mirror elements  3   d  includes a first electrode (for example, the electrode  12   a ) and a second electrode (for example, the electrode  12   b ). The first electrode and the second electrode are provided on the main surface  2   a  of the substrate  2 , and are separated from each other. The first electrode is electrically connected to the first end of the beam. The second electrode is electrically connected to the second end of the beam. 
     Therefore, it is possible to change the deflection angle of the optical scanning device  1   e  in accordance with a current flowing through the beam (for example, the beam  18   a ) and the second magnetic field formed on the beam by the second magnet (for example, the magnet  77 ), which makes it possible for the optical scanning device  1   e  to change the area to be optically scanned. 
     Sixth Embodiment 
     With reference to  FIGS.  26  and  27   , a distance measuring device  80  according to a sixth embodiment will be described. The distance measuring device  80  is, for example, a light detection and ranging measurement (LiDAR) system. 
     As illustrated in  FIG.  26   , the distance measuring device  80  includes a light source  82 , an optical scanning device  83 , and a light receiver  86 . The distance measuring device  80  may further include a beam splitter  84 , a case  81 , a transparent window  85 , and a light shielding member  43 . 
     The light source  82  emits a light beam  40  toward the optical scanning device  83 . The light source  82  is, for example, a laser light source such as a semiconductor laser. The light beam  40  emitted from the light source  82  is, for example, a laser light. The light beam  40  emitted from the light source  82  may have a wavelength within a near infrared wavelength range of 800 nm to 1600 nm. A light beam within the near infrared wavelength range is less susceptible to sunlight and is harmless to human eyes. Therefore, a light beam in the near infrared wavelength region is preferable as the light beam  40  to be used for the distance measuring device  80 . The light beam  40  emitted from the light source  82  may be a terahertz wave having a wavelength of 30 μm or more and 1000 μm or less. Since the terahertz wave is harmless to human body and has high transparency to an object, it is preferable as the light beam to be used for the distance measuring device  80 . 
     Specifically, the light source  82  may be a wavelength variable light source. The light source  82  may be, for example, a wavelength variable semiconductor laser. The light source  82  emits the light beam  40  in, for example, the third direction (z direction). The light beam  40  emitted from the light source  82  passes through the beam splitter  84  and is incident on the optical scanning device  83 . 
     The optical scanning device  83  is, for example, any one of the optical scanning devices  1 ,  1   b ,  1   c ,  1   d  and  1   e  according to the first to fifth embodiment, respectively. The light scanning device  83  diffracts the light beam  40  emitted from the light source  82  toward the periphery of the distance measuring device  80  and scans the periphery with the light beam. 
     The light beam emitted to the periphery of the optical scanning device  83  (for example, the +1 order diffraction light beam  41 ) is reflected or diffusely reflected by an object located in the periphery of the optical scanning device  83 . The light receiver  86  receives a light beam  41   b  reflected or diffusely reflected from the periphery of the distance measuring device  80 . Specifically, the light beam  41   b  reflected or diffusely reflected from the periphery of the distance measuring device  80  returns to the optical scanning device  83 . The light beam  41   b  reflected or diffusely reflected from the periphery of the distance measuring device  80  is diffracted by the light scanning device  83 , reflected by the beam splitter  84 , and incident on the light receiver  86 . The light receiver  86  is, for example, a photodiode. 
     The case  81  houses the light source  82 , the optical scanning device  83 , the light receiver  86 , and the beam splitter  84 . The case  81  may be provided with a transparent window  85 . The transparent window  85  transmits the +1 order diffraction light beam  41  diffracted by the optical scanning device  83  and the light beam  41   b  reflected or diffusely reflected from the periphery of the distance measuring device  80 . The transparent window  85  is made of transparent glass or transparent resin. The case  81  may be provided with a light shielding member  43 . The light shielding member  43  is the same as that described in the first embodiment. 
     The controller  7   f  is communicably connected to the light source  82 . As illustrated in  FIG.  27   , the controller  7   f  includes a light source control unit  91 . The light source control unit  91  controls the light source  82 , i.e., controls a light emission timing or a light emission rate of the light source  82 . The controller  7   f  is communicably connected to the light receiver  86 . The controller  7   f  includes a distance calculation unit  92 . The controller  7   f  receives a signal from the light receiver  86 . The distance calculation unit  92  is configured to process the signal so as to calculate a distance from an object located in the periphery of the distance measuring device  80  to the distance measuring device  80 . When the light shielding member  43  is an optical shutter, the controller  7   f  includes an optical shutter control unit  93 . The optical shutter control unit  93  controls an optical transmittance of the optical shutter. 
     The controller  7   f  may further include a voltage control unit  8  or the like depending on the configuration of the optical scanning device  83 . For example, when the optical scanning device  83  is the optical scanning device  1  of the first embodiment, the controller  7   f  further includes the voltage control unit  8  of the first embodiment. 
     The distance measuring device  80  according to the present embodiment has the following effects in addition to the effects of the optical scanning device  1  according to the first embodiment. 
     The distance measuring device  80  of the present embodiment includes a light source  82 , an optical scanning device  83 , and a light receiver  86 . The light scanning device  83  diffracts the light beam  40  emitted from the light source  82  toward the periphery of the distance measuring device  80  and scans the periphery with the light beam. The light receiver  86  receives the light beam  41   b  reflected or diffusely reflected from the periphery of the distance measuring device  80 . 
     The distance measuring device  80  includes an optical scanning device  83  capable of performing an optical scanning with a light beam at a higher speed. Therefore, the distance measuring device  80  can measure the distance of an object in the periphery of the distance measuring device  80  more quickly. The distance measuring device  80  includes an optical scanning device  83  capable of performing an optical scanning with a light beam at a larger deflection angle. Therefore, the distance measuring device  80  can more easily measure the distance of an object in the periphery of the distance measuring device  80 . 
     In the distance measuring device  80  of the present embodiment, the light source  82  is a wavelength variable light source. The diffraction angle of the light beam diffracted by the light scanning device  83  (the deflection angle of the light scanning device  83 ) can be changed by changing the wavelength of the light beam emitted from the light source  82 . The distance measuring device  80  can measure the distance of an object in the periphery thereof over a wider area. 
     It should be understood that the first embodiment to the sixth embodiment disclosed herein are illustrative and not restrictive in all respects. At least two of the first embodiment to the sixth embodiment disclosed herein may be combined unless they are inconsistent to each other. For example, the in-plane driving unit  70  of the fourth embodiment or the in-plane driving unit  70   e  of the fifth embodiment may be added to the optical scanning device  1   b  of the second embodiment or the optical scanning device  1   c  of the third embodiment. It is intended that the scope of the present invention is not limited to the description above but defined by the scope of the claims and encompasses all modifications equivalent in meaning and scope to the claims. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1   b ,  1   c ,  1   d ,  1   e ,  83 : optical scanning device;  2 : substrate;  2   a : main surface;  3 ,  3   b ,  3   c ,  3   d : movable mirror element;  4 : first movable mirror array;  5 : second movable mirror array;  7 ,  7   b ,  7   c ,  7   d ,  7   e ,  7   f : controller;  8 ,  8   c ,  8   d : voltage control unit;  8   b : current control unit;  9   b ,  9   e : magnetic field control unit;  10 : conductive substrate;  11 : first insulating film;  12   a ,  12   b ,  12   c ,  12   d ,  14 : electrode;  13   a ,  13   b ,  13   c ,  13   d ,  15 ,  72   a ,  72   b ,  72   c ,  72   d : wiring;  17   a ,  17   b ,  17   c ,  17   d : anchor;  18   a ,  18   b : beam;  20 : movable mirror;  21 : movable plate;  22 : mirror film;  23 : pillar;  24 : second insulating film;  30 : sacrificial layer;  31 : hole;  33 : silicon substrate;  34 : insulating film;  35 : silicon layer;  36 : SOI substrate;  40 ,  41   b : light beam;  41 : +1 order diffraction light beam;  42 : −1 order diffraction light beam;  43 : light shielding member;  51 ,  52 ,  53 ,  54 ,  77 : magnet;  61 ,  62 ,  63 ,  64 : piezoelectric film;  70 ,  70   e : in-plane driving unit;  71   a ,  71   b ,  71   c ,  71   d : comb-shaped electrode;  73   a ,  73   b ,  73   c ,  73   d : driving electrode;  74   a ,  74   b ,  74   c ,  74   d : comb-shaped electrode;  80 : distance measuring device;  81 : case;  82 : light source;  84 : beam splitter;  85 : transparent window;  86 : light receiver;  91 : light source control unit;  92 : distance calculation unit;  93 : optical shutter control unit