Patent Publication Number: US-2019196178-A1

Title: Actuator and light scanning device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority to Japanese Patent Applications No. 2017-251834 filed on Dec. 27, 2017, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an actuator and a light scanning device. 
     2. Description of the Related Art 
     Conventionally, there is known a light scanning device that scans light by causing a mirror to oscillate around a rotating axis, using an actuator having a piezoelectric element, an upper electrode formed on the piezoelectric element, and a lower electrode formed under the piezoelectric element. In the light scanning device, an upper wire connecting to the upper electrode and a lower wire connecting to the lower electrode are formed, in order to apply voltage to the piezoelectric element (see Patent Document 1, for example). 
     An actuator for a light scanning device disclosed in Patent Document 2 includes multiple beams forming a meander shape. Because a sensor for detecting displacement is provided on one of the beams located at an outermost position (hereinafter, this beam is referred to as an “outermost beam”), a displacement of the outermost beam can be detected by the sensor, and whether or not the actuator is generating a desired vibration can be detected. 
     In the actuator disclosed in Patent Document 2, when a malfunction occurs in the outermost beam, the malfunctions can be detected by the sensor. However, in a case in which breakage occurs in a beam located inwards from the outermost beam and in which the outermost beam is operating normally, the malfunction cannot be detected by the sensor. If a sensor is provided on each of the beams located inwards from the outermost beam, malfunction may be detected. However, in this case, as the same number of wires as the number of the sensors is required, the beams need to be thicker for placing the wires. 
     CITATION LIST 
     Patent Document 
     [Patent Document 1] Japanese Laid-open Patent Application Publication No. 2016-001325 
     [Patent Document 2] Japanese Laid-open Patent Application Publication No. 2017-068205 
     SUMMARY OF THE INVENTION 
     An actuator according to an aspect of the present invention includes an actuation object, a first actuating beam supporting the actuation object, a fixing frame supporting the first actuating beam, a first actuation source configured to cause the actuation object to oscillate around a first axis, by actuating the first actuating beam, a first wiring pattern for failure detection drawn on the first actuating beam, and a terminal of the first wiring pattern for failure detection disposed on the fixing frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a first embodiment; 
         FIG. 2  is a schematic diagram of a failure detecting circuit for the light scanning unit according to the first embodiment; 
         FIG. 3  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a second embodiment; 
         FIG. 4  is a plan view illustrating another example of a light scanning unit in a light scanning device according to the second embodiment; 
         FIG. 5  is a plan view illustrating yet another example of a light scanning unit in a light scanning device according to the second embodiment; 
         FIG. 6  is a schematic diagram of a failure detecting circuit for the light scanning unit according to the second embodiment; 
         FIG. 7  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a third embodiment; 
         FIG. 8  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a fourth embodiment; 
         FIG. 9  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a fifth embodiment; 
         FIG. 10  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a sixth embodiment; and 
         FIG. 11  is a plan view illustrating another example of an upper surface of a light scanning unit in a light scanning device according to the sixth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present disclosure will be described with reference to the drawings. Note that, in the drawings, elements having substantially identical features are given the same reference symbols and overlapping descriptions may be omitted. 
     First Embodiment 
       FIG. 1  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a first embodiment. The light scanning unit  100  according to the present embodiment can be operated in a state in which the light scanning unit  100  is housed in a package member such as a ceramic package. 
     The light scanning unit  100  scans laser light emitted from a light source, by oscillating a mirror  110 . The light scanning unit  100  is, for example, a MEMS (Micro Electro Mechanical Systems) mirror that drives a mirror  110  by a piezoelectric element. By reflecting incident light (laser light) using the mirror  110 , the light scanning unit  100  performs two-dimensional scanning of light. 
     As illustrated in  FIG. 1 , the light scanning unit  100  includes the mirror  110 , a mirror support (may also be referred to as a “mirror supporting member”)  120 , connecting beams  121 A and  121 B, horizontal actuating beams  130 A and  130 B, a movable frame  160 , vertical actuating beams  170 A and  170 B, and a fixing frame  180 . The mirror  110  is supported on the mirror support  120 . 
     At both sides of the mirror support  120  supporting the mirror  110 , the horizontal actuating beams  130 A and  130 B are provided respectively. The horizontal actuating beams  130 A and  130 B are connected to the mirror support  120  via the connecting beams  121 A and  121 B, respectively. The horizontal actuating beams  130 A and  130 B, the connecting beams  121 A and  121 B, the mirror support  120 , and the mirror  110  are supported by the movable frame  160  from outside. The horizontal actuating beam  130 A includes multiple horizontal beams of rectangular shape arranged side by side, each of which extends in a direction of a vertical oscillating axis AXV orthogonal to a horizontal oscillating axis AXH. Further, since one end of each horizontal beam is connected (linked) to an end of one of two adjacent horizontal beams, with the other end of the horizontal beam being connected (linked) to an end of the other of the two adjacent horizontal beams, the horizontal actuating beam  130 A has a meander shape as a whole. One end of the horizontal actuating beam  130 A is connected to an inner edge of the movable frame  160 , and the other end of the horizontal actuating beam  130 A is connected to the mirror support  120 . The horizontal actuating beam  130 B also includes multiple horizontal beams of rectangular shape arranged side by side, each of which extends in the direction of the vertical oscillating axis AXV. Further, since one end of each horizontal beam is connected (linked) to an end of one of two adjacent horizontal beams, with the other end of the horizontal beam being connected (linked) to an end of the other of the two adjacent horizontal beams, the horizontal actuating beam  130 B has a meander shape as a whole. One end of the horizontal actuating beam  130 B is connected to an inner edge of the movable frame  160 , and the other end of the horizontal actuating beam  130 B is connected to the mirror support  120 . 
     In addition, at both sides of the movable frame  160 , the vertical actuating beams  170 A and  170 B are provided respectively. The vertical actuating beam  170 A includes multiple vertical beams of rectangular shape arranged side by side, each of which extends in a direction of the horizontal oscillating axis AXH. Since one end of each vertical beam is connected (linked) to an end an adjacent vertical beam, the vertical actuating beam  170 A has a meander shape as a whole. One end of the vertical actuating beam  170 A is connected to an inner edge of the fixing frame  180 , and the other end of the vertical actuating beam  170 A is connected to an outer edge of the movable frame  160 . The vertical actuating beam  170 B also includes multiple vertical beams of rectangular shape arranged side by side, each of which extends in a direction of the horizontal oscillating axis AXH. Since one end of each vertical beam is connected (linked) to an end of an adjacent vertical beam, the vertical actuating beam  170 B has a meander shape as a whole. One end of the vertical actuating beam  170 B is connected to an inner edge of the fixing frame  180 , and the other end of the vertical actuating beam  170 B is connected to an outer edge of the movable frame  160 . 
     The horizontal actuating beams  130 A and  130 B include horizontal actuation sources  131 A and  131 B respectively. Also, the vertical actuating beams  170 A and  170 B include vertical actuation sources  171 A and  171 B respectively. The horizontal actuation beams  130 A and  130 B and the vertical actuation beams  170 A and  170 B serve as actuators for scanning laser light by causing the mirror  110  to oscillate horizontally and vertically. 
     On each of the horizontal beams (not including curved portions) on an upper surface of the horizontal actuating beam  130 A, the horizontal actuation source  131 A is formed. Similarly, on each of the horizontal beams (not including curved portions) on an upper surface of the horizontal actuating beam  130 B, the horizontal actuation source  131 B is formed. The horizontal actuation source  131 A includes a piezoelectric thin film formed on the upper surface of the horizontal actuating beam  130 A, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. The horizontal actuation source  131 B includes a piezoelectric thin film formed on the upper surface of the horizontal actuating beam  130 B, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. 
     To each of the horizontal beams in the horizontal actuating beams  130 A and  130 B, drive voltage having different polarity from that applied to an adjacent horizontal beam is applied. As a result, each of the horizontal beams in the horizontal actuating beams  130 A and  130 B bends in a different direction from the adjacent horizontal beam, and accumulated displacement from each of the horizontal beams is propagated to the mirror support  120 . By the above mentioned operation of the horizontal actuating beams  130 A and  130 B, the mirror  110  and the mirror support  120  oscillate in a manner in which the mirror  110  and the mirror support  120  rotate around the horizontal oscillating axis AXH (which passes through a center of a reflecting surface of the mirror  110 ). In the present embodiment, this direction of the rotation (oscillation) of the mirror  110  (and the mirror support  120 ) is referred to as a “horizontal direction”. For example, a non-resonant vibration mode may be used for the horizontal actuation of the horizontal actuating beams  130 A and  130 B. 
     For example, the horizontal actuation source  131 A includes four horizontal actuation sources  131 A 1 ,  131 A 2 ,  131 A 3 , and  131 A 4 , which are respectively formed on first, second, third, and fourth horizontal beams constituting the horizontal actuating beam  130 A. The horizontal actuation source  131 B also includes four horizontal actuation sources  131 B 1 ,  131 B 2 ,  131 B 3 , and  131 B 4 , which are respectively formed on first, second, third, and fourth horizontal beams constituting the horizontal actuating beam  130 B. In this case, if the actuation sources  131 A 1 ,  131 B 1 ,  131 A 3 , and  131 B 3  are actuated by voltage having the same waveform being applied, and if the actuation sources  131 A 2 ,  131 E 32 ,  131 A 4 , and  131 B 4  are actuated by voltage having opposite polarity from that applied to the actuation sources  131 A 1  and the like, the mirror  110  and the mirror support  120  are caused to oscillate in a horizontal direction. 
     On each of the vertical beams (not including curved portions) on an upper surface of the vertical actuating beam  170 A, the vertical actuation source  171 A is formed. Similarly, on each of the vertical beams (not including curved portions) on an upper surface of the vertical actuating beam  170 B, the vertical actuation source  171 B is formed. The vertical actuation source  171 A includes a piezoelectric thin film formed on the upper surface of the vertical actuating beam  170 A, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. The vertical actuation source  171 B includes a piezoelectric thin film formed on the upper surface of the vertical actuating beam  170 B, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. 
     To each of the vertical beams in the vertical actuating beams  170 A and  170 B, drive voltage having different polarity from that applied to an adjacent vertical beam is applied. As a result, each of the vertical beams in the vertical actuating beams  170 A and  170 B bends in a different direction from the adjacent vertical beam, and accumulated displacement from each of the vertical beams is propagated to the movable frame  160 . By the above mentioned operation of the vertical actuating beams  170 A and  170 B, the mirror  110  and the mirror support  120  oscillate in a manner in which the mirror  110  and the mirror support  120  rotate around an axis which is orthogonal to the horizontal oscillating axis AXH and which passes through a center of a reflecting surface of the mirror  110 . In the present embodiment, this direction of the rotation (oscillation) of the mirror  110  is referred to as a “vertical direction”, and the axis which is orthogonal to the horizontal oscillating axis AXH and which passes through the center of the reflecting surface of the mirror  110  is referred to as the vertical oscillating axis AXV. For example, a non-resonant vibration mode may be used for the vertical actuation of the vertical actuating beams  170 A and  170 B. 
     For example, the vertical actuation source  171 A includes two vertical actuation sources  171 A 1  and  171 A 2 , which are respectively formed on first and second vertical beams constituting the vertical actuating beam  170 A. The vertical actuation source  171 B also includes two vertical actuation sources  17181  and  171 B 2 , which are respectively formed on first and second vertical beams constituting the vertical actuating beam  170 B. In this case, if the actuation sources  171 A 1  and  171 B 1  are actuated by voltage having the same waveform, and if the actuation sources  171 A 2  and  171 B 2  are actuated by voltage having opposite polarity from that applied to the actuation sources  171 A 1  and  171 B 1 , the movable frame  160  connected to the mirror  110  is caused to oscillate in a vertical direction. 
     In the light scanning device according to the present embodiment, a MEMS structure functioning as an actuator is formed of an SOI substrate including a support layer, a buried oxide (BOX) layer, and an active layer, for example. The fixing frame  180  and the movable frame  160  described above are formed of a support layer, a BOX layer, and an active layer. On the other hand, parts of the light scanning device other than the fixing frame  180  and the movable frame  160 , such as the horizontal actuating beams  130 A and  130 B and the vertical actuating beams  170 A and  170 B, are formed of a single layer of an active layer, or may be formed of a BOX layer and an active layer. 
     On the outermost vertical beam of the vertical actuating beam  170 A, a displacement sensor  195  for acquiring displacement is formed. On the outermost vertical beam of the vertical actuating beam  170 B, a displacement sensor  196  for acquiring displacement is formed. Based on signals acquired from the displacement sensors  195  and  196 , displacement of the outermost vertical beam of the vertical actuating beam  170 A and the outermost vertical beam of the vertical actuating beam  170 B can be detected, and whether or not a desired vibration is generated by the vertical actuating beams  170 A and  170 B can be detected. 
     In the light scanning device according to the present embodiment, a wiring pattern for failure detection  10  is formed on the vertical actuating beams  170 A and  170 B and the horizontal actuating beams  130 A and  130 B. Terminals  11  and  12  are formed at one end of the wiring pattern for failure detection  10  and the other end of the wiring pattern for failure detection  10  respectively. Each of the terminals  11  and  12  is formed on the fixing frame  180 . From the terminal  11  on the fixing frame  180 , the wiring pattern for failure detection  10  is drawn on the vertical actuating beam  170 A via a connecting member A 12 , drawn on the movable frame  160  via a connecting member A 11 , and further drawn on the horizontal actuating beam  130 B and the connecting beams  121 B and  121 A. The wiring pattern for failure detection  10  is further drawn, from the connecting beams  121 B and  121 A, on the horizontal actuating beam  130 A, drawn on the vertical actuating beam  170 B via a connecting member A 13 , and drawn to the terminal  12  on the fixing frame  180  via a connecting member. 
     The light scanning device according to the present embodiment is configured to be capable of detecting whether an actuating beam on which a wiring pattern for failure detection is drawn has breakage or not, by checking a conduction state between the terminals  11  and  12 . That is, in a case in which a path between the terminals  11  and  12  is in a conductive state, it is determined that no breakage occurs in actuating beams on which a wiring pattern for failure detection is drawn. Conversely, in a case in which a path between the terminals  11  and  12  is not in a conductive state, it is determined that breakage occurs at a certain point in actuating beams on which a wiring pattern for failure detection is drawn. As described above, in a MEMS structure functioning as an actuator, in a case in which breakage occurs in a beam located inwards from an outermost beam, the breakage can be detected regardless of whether a displacement sensor is present or not. 
     The wiring pattern for failure detection in the light scanning device according to the present embodiment does not detect a variation of an amount of vibration of an actuating beam, but can be used for determination as to whether or not breakage occurs in an actuating beam. By providing the wiring pattern for failure detection, detection of breakage in an actuating beam can be realized. Also, as voltage applied to the wiring pattern for failure detection may be low, a thin wiring pattern can be used as the wiring pattern for failure detection. As the required number of the wiring patterns is one, at minimum, providing the wiring pattern for failure detection on a beam (such as the horizontal actuating beam and the vertical actuating beam) has little effect on beam width as compared to a case in which additional displacement sensors are provided. 
       FIG. 2  is a schematic diagram of a failure detecting circuit for the light scanning unit  100  according to the present embodiment. A wiring pattern for failure detection  10 A is drawn on a MEMS structure such as the vertical actuating beams  170 A and  170 B and the horizontal actuating beams  130 A and  130 B. Voltage V such as power supply voltage is applied to one of terminals of the wiring pattern for failure detection  10 A. The other terminal of the wiring pattern for failure detection  10 A is connected to an input terminal of a signal processing unit such as a CPU (Central Processing Unit), and the CPU can observe an output of the other terminal in real time. An intermediate section of the wiring pattern for failure detection  10 A is grounded via a resistance element R. In a case in which the failure detecting circuit is configured as illustrated in  FIG. 2 , if the MEMS structure such as the vertical actuating beams  170 A and  170 B and the horizontal actuating beams  130 A and  130 B is not in failure, the voltage V is input to the input terminal of the CPU. Conversely, if disconnection occurs at any point of the MEMS structure such as the vertical actuating beams  170 A and  170 B and the horizontal actuating beams  130 A and  130 B, the input terminal of the CPU is grounded. In a case in which a value between the ground voltage and the voltage V is defined as a threshold, when voltage below the threshold is input to the CPU, it is determined that disconnection occurs at any point within the MEMS structure. Note that a circuit used for checking a conduction state of a wiring pattern for failure detection is not limited to the circuit illustrated in  FIG. 2 . Other circuits may be used for checking a conduction state. 
     Second Embodiment 
       FIG. 3  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a second embodiment. The light scanning unit includes a mirror, a mirror support  122 , horizontal actuating beams  132 A and  132 B, vertical actuating beams  172 A and  172 B, and a fixing frame  181 . The mirror is supported on the mirror support  122 . At both sides of the mirror support  122  supporting the mirror, in a direction of a horizontal oscillating axis AXH, the horizontal actuating beams  132 A and  132 B are provided respectively. Each of the horizontal actuating beams  132 A and  132 B is connected to the mirror support  122  at one end, and is connected to the fixing frame  181  at the other end. Each of the horizontal actuating beams  132 A and  132 B includes multiple horizontal beams of rectangular shape arranged side by side, each of which extends in a direction of a vertical oscillating axis AXV orthogonal to the horizontal oscillating axis AXH. Since one end of each horizontal beam is connected (linked) to an end of one of two adjacent horizontal beams, with the other end of the horizontal beam being connected (linked) to an end of the other of the two adjacent horizontal beams, the horizontal actuating beams  132 A and  132 B have a meander shape as a whole. 
     At both sides of the mirror support  122  supporting the mirror, in a direction of the vertical oscillating axis AXV, the vertical actuating beams  172 A and  172 B are provided respectively. Each of the vertical actuating beams  172 A and  172 B is connected to the mirror support  122  at one end, and is connected to the fixing frame  181  at the other end. Each of the vertical actuating beams  172 A and  172 B includes multiple vertical beams of rectangular shape arranged side by side, each of which extends in a direction of the horizontal oscillating axis AXH orthogonal to the vertical oscillating axis AXV. Since one end of each vertical beam is connected (linked) to an end of one of two adjacent vertical beams, with the other end of the vertical beam being connected (linked) to an end of the other of the two adjacent vertical beams, the vertical actuating beams  172 A and  172 B have a meander shape as a whole. 
     On each of the horizontal actuating beams  132 A and  132 B, a horizontal actuation source is formed. Also, on each of the vertical actuating beams  172 A and  172 B, a vertical actuation source is formed. The horizontal actuation beams  132 A and  132 B and the vertical actuation beams  172 A and  172 B serve as actuators for scanning laser light by causing the mirror support  122  to oscillate horizontally and vertically. 
     On upper surfaces of the horizontal actuating beams  132 A and  132 B, the horizontal actuation source is formed on each of the horizontal beams (not including curved portions). The horizontal actuation source includes a piezoelectric thin film, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. To each of the horizontal beams in the horizontal actuating beams  132 A and  132 B, drive voltage having different polarity from that applied to an adjacent horizontal beam is applied. As a result, each of the horizontal beams in the horizontal actuating beams  132 A and  132 B bends in a different direction from the adjacent horizontal beam, and accumulated displacement from each of the horizontal beams is propagated to the mirror support  122 . By the above mentioned operation of the horizontal actuating beams  132 A and  132 B, the mirror and the mirror support  122  oscillate in a manner in which the mirror and the mirror support  122  rotate around the horizontal oscillating axis AXH (which passes through a center of a reflecting surface of the mirror  110 ). In the present embodiment, this direction of the rotation (oscillation) of the mirror (and the mirror support  122 ) is referred to as a “horizontal direction”. For example, a non-resonant vibration mode may be used for the horizontal actuation of the horizontal actuating beams  132 A and  132 B. 
     On upper surfaces of the vertical actuating beams  172 A and  172 B, the vertical actuation source is formed on each of the vertical beams (not including curved portions). The vertical actuation source includes a piezoelectric thin film, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. To each of the vertical beams in the vertical actuating beams  172 A and  172 B, drive voltage having different polarity from that applied to an adjacent vertical beam is applied. As a result, each of the vertical beams in the vertical actuating beams  172 A and  172 B bends in a different direction from the adjacent vertical beam, and accumulated displacement from each of the vertical beams is propagated to the movable frame  160 . By the above mentioned operation of the vertical actuating beams  172 A and  172 B, the mirror and the mirror support  122  oscillate in a manner in which the mirror and the mirror support  122  rotate around the vertical oscillating axis AXV. In the present embodiment, this direction of the rotation (oscillation) of the mirror is referred to as a “vertical direction”, and the vertical oscillating axis AXV passes through the center of the reflecting surface of the mirror. For example, a non-resonant vibration mode may be used for the vertical actuation of the vertical actuating beams  172 A and  172 B. 
     In the light scanning device according to the present embodiment, a MEMS structure functioning as an actuator is formed of an SOI substrate including a support layer, a buried oxide (BOX) layer, and an active layer, for example. The above described fixing frame  180  and the like are formed of a support layer, a BOX layer, and an active layer. On the other hand, parts of the light scanning device such as the horizontal actuating beams  132 A and  132 B and the vertical actuating beams  172 A and  172 B, is formed of a single layer of an active layer, or may be formed of a BOX layer and an active layer. 
     In the light scanning device according to the present embodiment, a wiring pattern for failure detection  13  is formed on the vertical actuating beams  172 A and  172 B and the horizontal actuating beams  132 A and  132 B. Terminals  14  and  15  are formed at one end of the wiring pattern for failure detection  13  and the other end of the wiring pattern for failure detection  13  respectively. The terminals  14  and  15  are formed on the fixing frame  181 . The wiring pattern for failure detection  13  is drawn from the terminal  14  (on the fixing frame  181 ) on the vertical actuating beam  172 B, and drawn on the horizontal actuating beam  132 A and the fixing frame  181  via the mirror support  122 . From the fixing frame  181 , the wiring pattern for failure detection  13  is further drawn on the vertical actuating beam  172 A, and on the horizontal actuating beam  132 B via the mirror support  122 . Lastly, the wiring pattern for failure detection  13  is connected to the terminal  15  on the fixing frame  181 . 
     The light scanning device according to the present embodiment illustrated in  FIG. 3  is configured to be capable of detecting whether an actuating beam on which a wiring pattern for failure detection is drawn has breakage or not, by checking a conduction state between the terminals  14  and  15 . That is, in a case in which a path between the terminals  14  and  15  is in a conductive state, it is determined that no breakage occurs in actuating beams on which a wiring pattern for, failure detection is drawn (the vertical actuating beams  172 A and  172 B and the horizontal actuating beams  132 A and  132 B). Conversely, in a case in which a path between the terminals  14  and  15  is not in a conductive state, it is determined that breakage occurs at a certain point in the actuating beams on which a wiring pattern for failure detection is drawn. By checking the conduction state between the terminals ( 14  and  15 ), presence or absence of breakage in an actuating beam can be determined. As described above, in a MEMS structure functioning as an actuator, in a case in which breakage occurs in a beam located inwards from an outermost beam, the breakage can be detected regardless of whether a displacement sensor is present or not. 
       FIG. 4  is a plan view illustrating another example of a light scanning unit in a light scanning device according to the second embodiment. Except for a route of a wiring pattern for failure detection, a configuration of the light scanning unit in  FIG. 4  is the same as that in  FIG. 3 . On a mirror support (actuation target), a set of wiring patterns for failure detection  16  in  FIG. 4  has an intersection of wiring patterns drawn on vertical actuating beams and wiring patterns drawn on horizontal actuating beams. For example, a first one of the wiring patterns for failure detection  16  is drawn from a terminal  17  on a fixing frame  181  to a mirror support  122  via a horizontal actuating beam  132 A. A second one of the wiring patterns for failure detection  16  is drawn from a terminal  18  on the fixing frame  181  to the mirror support  122  via a vertical actuating beam  172 A. A third one of the wiring patterns for failure detection  16  is drawn from a terminal  19  on a fixing frame  181  to the mirror support  122  via a horizontal actuating beam  132 B. A fourth one of the wiring patterns for failure detection  16  is drawn from a terminal  20  on the fixing frame  181  to the mirror support  122  via a vertical actuating beam  172 B. An intersection of the above mentioned four wiring patterns for failure detection  16  is located at the center  121  of the mirror support  122 . 
     The light scanning unit illustrated in  FIG. 4  is configured to be capable of detecting whether an actuating beam on which a wiring pattern for failure detection is drawn has breakage or not, by checking a conduction state between any two terminals among the four terminals  17 ,  18 ,  19 , and  20 . That is, in a case in which a path between the terminals  17  and  18  is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beam  132 A and the vertical actuating beam  172 A on which a wire for failure detection between the terminals  17  and  18  is drawn. Conversely, in a case in which the path between the terminals  17  and  18  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beam  132 A and the vertical actuating beam  172 A on which the wire for failure detection between the terminals  17  and  18  is drawn. In a case in which a path between the terminals  17  and  19  is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beams  132 A and  132 B on which a wire for failure detection between the terminals  17  and  19  is drawn. Conversely, in a case in which the path between the terminals  17  and  19  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beams  132 A and  132 B on which the wire for failure detection between the terminals  17  and  19  is drawn. In a case in which a path between the terminals  17  and  20  is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beam  132 A and the vertical actuating beam  172 B on which a wire for failure detection between the terminals  17  and  20  is drawn. Conversely, in a case in which the path between the terminals  17  and  20  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beam  132 A and the vertical actuating beam  172 B on which the wire for failure detection between the terminals  17  and  20  is drawn. In a case in which a path between the terminals  18  and  19  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beam  172 A and the horizontal actuating beam  132 B on which a wire for failure detection between the terminals  18  and  19  is drawn. Conversely, in a case in which the path between the terminals  18  and  19  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beam  172 A and the horizontal actuating beam  132 B on which the wire for failure detection between the terminals  18  and  19  is drawn. In a case in which a path between the terminals  18  and  20  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  172 A and  172 B on which a wire for failure detection between the terminals  18  and  20  is drawn. Conversely, in a case in which the path between the terminals  18  and  20  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  172 A and  172 B on which the wire for failure detection between the terminals  18  and  20  is drawn. In a case in which a path between the terminals  19  and  20  is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beam  132 B and the vertical actuating beam  172 B on which a wire for failure detection between the terminals  19  and  20  is drawn. Conversely, in a case in which the path between the terminals  19  and  20  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beam  132 B and the vertical actuating beam  172 B on which the wire for failure detection between the terminals  19  and  20  is drawn. 
     In the light scanning unit illustrated in  FIG. 4 , for example, by checking conduction states of paths each connecting the terminal  17  with any one of the terminals  18 ,  19 , and  20 , it can be determined which of the actuating beams has breakage. For example, in a case in which electrical conduction cannot be detected from any of the paths each connecting the terminal  17  with one of the terminals  18 ,  19 , and  20 , it is determined that breakage occurs in the horizontal actuating beam  132 A. Further, in a case in which electrical conduction cannot be detected from one of the above mentioned paths, it is determined that breakage occurs in an actuating beam corresponding to the path from which electrical conduction cannot be detected. That is, in such a case, if electrical conduction cannot be detected from a path between the terminal  17  and the terminal  18 , it is determined that breakage occurs in the vertical actuating beam  172 A. In such a case, if electrical conduction cannot be detected from a path between the terminal  17  and the terminal  19 , it is determined that breakage occurs in the horizontal actuating beam  132 B. In such a case, if electrical conduction cannot be detected from a path between the terminal  17  and the terminal  20 , it is determined that breakage occurs in the vertical actuating beam  172 B. As described above, in a MEMS structure functioning as an actuator, in a case in which breakage occurs in a beam located inwards from an outermost beam, the breakage can be detected regardless of whether a displacement sensor is present or not. 
       FIG. 5  is a plan view illustrating yet another example of a light scanning unit in a light scanning device according to the second embodiment. Except for a route of a wiring pattern for failure detection, a configuration of the light scanning unit in  FIG. 5  is the same as that in  FIG. 3  or  FIG. 4 . A wiring pattern for failure detection of the light scanning unit illustrated in  FIG. 5  includes a first wiring pattern  22  drawn on a horizontal actuating beam  132 A and a vertical actuating beam  172 B, and a second wiring pattern  25  drawn on a horizontal actuating beam  132 B and a vertical actuating beam  172 A. The second wiring pattern  25  does not cross the first wiring pattern  22 . For example, the first wiring pattern  22  is drawn from a terminal  23  on a fixing frame  181  to a terminal  24  via the horizontal actuating beam  132 A, a mirror support  122 , and the vertical actuating beams  172 B. The second wiring pattern  25  is drawn from a terminal  26  on the fixing frame  181  to a terminal  27  via the vertical actuating beam  172 A, the mirror support  122 , and the horizontal actuating beam  132 B, without crossing the first wiring pattern  22 . 
     In the light scanning unit illustrated in  FIG. 5 , by checking a conduction state between the terminals  23  and  24 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection (the first wiring pattern  22 ) is drawn can be detected. That is, in a case in which the first wiring pattern  22  (a path between the terminals  23  and  24 ) is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beam  132 A and the vertical actuating beams  172 B on which the first wiring pattern  22  is drawn. Conversely, in a case in which the first wiring pattern  22  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beam  132 A or the vertical actuating beams  172 B on which the first wiring pattern  22  is drawn. Further, by checking a conduction state between the terminals  26  and  27 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection (the second wiring pattern  25 ) is drawn can be detected. That is, in a case in which the second wiring pattern  25  (a path between the terminals  26  and  27 ) is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  172 A and the horizontal actuating beam  132 B on which the second wiring pattern  25  is drawn. Conversely, in a case in which the second wiring pattern  25  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  172 A or the horizontal actuating beam  132 B on which the second wiring pattern  25  is drawn. As described above, in a MEMS structure functioning as an actuator, in a case in which breakage occurs in a beam located inwards from an outermost beam, the breakage can be detected regardless of whether a displacement sensor is present or not. 
       FIG. 6  is a schematic diagram of a failure detecting circuit for the light scanning unit according to the present embodiment. A wiring pattern for failure detection  10 B is drawn on a MEMS structure such as the vertical actuating beams  172 A and  172 B and the horizontal actuating beams  132 A and  132 B. One of terminals of the wiring pattern for failure detection  10 B is grounded, and the other terminal of the wiring pattern for failure detection  10 B is connected to an input terminal of a signal processing unit such as a CPU, and the CPU can observe an output of the other terminal in real time. To an intermediate section of the wiring pattern for failure detection  10 B, voltage V such as power supply voltage is applied via a resistance element R. In a case in which the failure detecting circuit is configured as illustrated in  FIG. 6 , if the MEMS structure such as the vertical actuating beams  172 A and  172 B and the horizontal actuating beams  132 A and  132 B is not in failure, the input terminal of the CPU is grounded. Conversely, if disconnection occurs at any point of the MEMS structure such as the vertical actuating beams  172 A and  172 B and the horizontal actuating beams  132 A and  132 B, the voltage at the input terminal of the CPU is raised towards the voltage V. In a case in which a value between the ground voltage and the voltage V is defined as a threshold, when voltage above the threshold is input to the CPU, it is determined that disconnection occurs at any point of the MEMS structure. Note that a circuit used for checking a conduction state of the wiring pattern for failure detection is not limited to the circuit illustrated in  FIG. 6 . Another type of circuit may be used for checking a conduction state. 
     The failure detecting circuit illustrated in  FIG. 6  is applicable to the first embodiment. Similarly, the failure detecting circuit illustrated in  FIG. 2  is applicable to the second embodiment. Further, in the following embodiments to be described below, both the failure detecting circuit illustrated in  FIG. 2  and the failure detecting circuit illustrated in  FIG. 6  can be employed. 
     Third Embodiment 
       FIG. 7  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a third embodiment. The light scanning unit illustrated in  FIG. 7  is similar to that in  FIG. 1 , except that a resistive-type resistance thermometer  28  is provided on a path of a wiring pattern for failure detection  10 , in the light scanning unit illustrated in  FIG. 7 . In  FIG. 7 , the resistance thermometer  28  is provided on the movable frame  160 , on the path of the wiring pattern for failure detection  10 . Normally, the resistance thermometer  28  is used for measuring temperature of the light scanning unit, by measuring resistance of the wiring pattern for failure detection  10  including the resistance thermometer  28 . In a case in which electrical conduction cannot be detected from the wiring pattern for failure detection (because of disconnection), it is determined that breakage occurs in an actuating beam. As the resistance thermometer  28 , a thermistor can be used. In addition, other function-specific devices may be provided on the path of the wiring pattern for failure detection  10 . For example, by providing a strain gauge, a strain can be observed. Because of the wiring pattern, functions such as temperature measurement or strain measurement can be added without additional wiring. 
     Fourth Embodiment 
       FIG. 8  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a fourth embodiment. The light scanning unit illustrated in  FIG. 8  is similar to that in  FIG. 1 , except that a first wiring pattern  29  and a second wiring pattern  32  are provided to the light scanning unit of  FIG. 8 , as a wiring pattern for failure detection. 
     In the light scanning device according to the present embodiment, the first wiring pattern  29  is drawn on vertical actuating beams  170 A and  170 B and horizontal actuating beams  130 A and  130 B. The first wiring pattern  29  also includes terminals  30  and  31 , and the terminals  30  and  31  are formed on the fixing frame  180 . For example, the first wiring pattern  29  is drawn from the terminal  30  on the fixing frame  180  to the vertical actuating beam  170 A via a connecting member A 12 . Further, the first wiring pattern  29  is drawn from the vertical actuating beam  170 A, via a connecting member A 11 , to upper surfaces of a movable frame  160 , the horizontal actuating beam  130 B, a connecting beam  121 B, and a connecting beam  121 A. Further, the first wiring pattern  29  is drawn on the horizontal actuating beam  130 A from the connecting beams  121 B and  121 A, drawn on the vertical actuating beam  170 B via a connecting member A 13 , and is connected to the terminal  31  on the fixing frame  180  via a connecting member A 14 . 
     Further, in the light scanning device according to the present embodiment, the second wiring pattern  32  is drawn on the vertical actuating beams  170 A and  170 B. The second wiring pattern  32  is not drawn on the horizontal actuating beams  130 A and  130 B. The second wiring pattern  32  includes terminals  33  and  34 , and the terminals  33  and  34  are formed on the fixing frame  180 . For example, the second wiring pattern  32  is drawn from the terminal  33  on the fixing frame  180  to the upper surface of the vertical actuating beam  170 A via the connecting member A 12 , and is drawn on the movable frame  160  via the connecting member A 11 . Further, the second wiring pattern  32  is drawn on the vertical actuating beam  170 B, from the movable frame  160  via the connecting member A 13 , and is connected to the terminal  34  on the fixing frame  180  via a connecting member A 14 . 
     In the light scanning unit illustrated in  FIG. 8 , by checking a conduction state between the terminals  30  and  31 , and a conduction state between the terminals  33  and  34 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection (the first and second wiring patterns  29  and  32 ) is drawn can be detected. That is, in a case in which a path between the terminals  30  and  31  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  170 A and  170 B and the horizontal actuating beams  130 A and  130 B on which the first wiring pattern  29  is drawn. In a case in which a path between the terminals  30  and  31  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  170 A and  170 B or the horizontal actuating beams  130 A and  130 B on which the first wiring pattern  29  is drawn. In a case in which a path between the terminals  33  and  34  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  170 A and  170 B on which the second wiring pattern  32  is drawn. In a case in which a path between the terminals  33  and  34  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  170 A and  170 B on which the second wiring pattern  32  is drawn. 
     In the light scanning unit illustrated in  FIG. 8 , in a case in which no electrical conduction between the terminals  30  and  31  or between the terminals  33  and  34  can be detected, that is, in a case in which both the first and second wiring patterns  29  and  32  are disconnected, it is assumed that breakage occurs in the vertical actuating beams  170 A and  170 B on which both the first wiring pattern  29  and the second wiring pattern  32  are drawn. Also, in a case in which electrical conduction between the terminals  33  and  34  can be detected but electrical conduction between the terminals  30  and  31  cannot be detected, that is, in a case in which the second wiring pattern  32  is not disconnected but the first wiring pattern  29  is disconnected, it is assumed that breakage occurs in the horizontal actuating beams  130 A and  130 B on which only the first wiring pattern  29  is drawn. As described above, in a MEMS structure functioning as an actuator, in a case in which breakage occurs in a beam located inwards from an outermost beam, the breakage can be detected regardless of whether a displacement sensor is present or not. 
     Fifth Embodiment 
       FIG. 9  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a fifth embodiment. The light scanning unit scans laser light emitted from a light source, by oscillating a mirror. The light scanning unit is, for example, a MEMS mirror that drives the mirror by a piezoelectric element. By reflecting incident light (laser light) using the mirror, the light scanning unit performs two-dimensional scanning of light. 
     As illustrated in  FIG. 9 , the light scanning unit includes the mirror, a mirror support  220 , horizontal actuating beams  231 A and  231 B, and a fixing frame  280 . The mirror is supported on the mirror support  220 . At both sides of the mirror support  220  supporting the mirror, the horizontal actuating beams  231 A and  231 B are provided respectively. The horizontal actuating beams  231 A and  231 B extend in a direction of a horizontal oscillating axis AXH, and each of the horizontal actuating beams  231 A and  231 B is connected to the mirror support  220  at one end, and is connected to the fixing frame  280  at the other end. The horizontal actuating beams  231 A and  231 B act as torsion beams for causing the mirror support  220  to oscillate around the horizontal oscillating axis AXH. Horizontal actuation sources are formed on the fixing frame  280 , at a location close to the horizontal actuating beam  231 A and at a location close to the horizontal actuating beam  231 B. Each of the horizontal actuation sources is formed of a piezoelectric thin film, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. By applying a predetermined voltage to the horizontal actuation sources, the horizontal actuating beams  231 A and  231 B are twisted, and the mirror support  220  oscillates around the horizontal oscillating axis AXH. Alternatively, the mirror support  220  may be actuated electromagnetically by providing coils on the mirror support  220 . 
     In the light scanning device according to the present embodiment, a wiring pattern for failure detection  40  is formed on the horizontal actuating beams  231 A and  231 B. Terminals  41  and  42  are formed at one end of the wiring pattern for failure detection  40  and the other end of the wiring pattern for failure detection  40 , and the terminals  41  and  42  are formed on the fixing frame  280 . From the terminal  41  on the fixing frame  280 , the wiring pattern for failure detection  40  is drawn on the horizontal actuating beam  231 A, the mirror support  220 , and the horizontal actuating beam  231 B, and the wiring pattern for failure detection  40  is connected to the terminal  42  on the fixing frame  280 . 
     In the light scanning device according to the present embodiment, by checking a conduction state between the terminals  41  and  42 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection  40  is drawn can be detected. That is, in a case in which a path between the terminals  41  and  42  is in a conductive state, it is determined that no breakage occurs in the horizontal actuating beams  231 A and  231 B on which the wiring pattern for failure detection  40  is drawn. In a case in which a path between the terminals  41  and  42  is not in a conductive state, it is determined that breakage occurs at a certain point in the horizontal actuating beams  231 A and  231 B on which the wiring pattern for failure detection  40  is drawn. As described above, in a MEMS structure functioning as an actuator, breakage of a beam can be detected regardless of whether a displacement sensor is present or not. 
     Sixth Embodiment 
       FIG. 10  is a plan view illustrating an example of an upper surface of a light scanning unit in a light scanning device according to a sixth embodiment. The light scanning unit scans laser light emitted from a light source, by oscillating a mirror. The light scanning unit is, for example, a MEMS mirror that drives the mirror by a piezoelectric element. By reflecting incident light (laser light) using the mirror, the light scanning unit performs two-dimensional scanning of light. 
     As illustrated in  FIG. 10 , the light scanning unit includes the mirror, a mirror support  220 , horizontal actuating beams  231 A and  231 B, a movable frame  260 , vertical actuating beams  271 A and  271 B, and a fixing frame  280 . The mirror is supported on the mirror support  220 . At both sides of the mirror support  220  supporting the mirror, a pair of the horizontal actuating beams  231 A and  231 B are provided respectively. The horizontal actuating beams  231 A and  231 B extend in a direction of a horizontal oscillating axis AXH, and each of the horizontal actuating beams  231 A and  231 B is connected to the mirror support  220  at one end, and is connected to the movable frame  260  at the other end. The horizontal actuating beams  231 A and  231 B act as torsion beams for causing the mirror support  220  to oscillate around the horizontal oscillating axis AXH. Horizontal actuation sources are formed on the movable frame  260 . Each of the horizontal actuation sources is formed of a piezoelectric thin film, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. By applying predetermined voltage to the horizontal actuation sources, the horizontal actuating beams  231 A and  231 B are twisted, and the mirror support  220  oscillates around the horizontal oscillating axis AXH. At both sides of the movable frame  260 , the vertical actuating beams  271 A and  271 B are provided respectively, and the vertical actuating beams  271 A and  271 B are connected to the movable frame  260 . The vertical actuating beams  271 A and  271 B extend in a direction of a vertical oscillating axis AXV, and each of the vertical actuating beams  271 A and  271 B is connected to the movable frame  260  at one end, and is connected to the fixing frame  280  at the other end. The vertical actuating beams  271 A and  271 B act as torsion beams for causing the movable frame  260  to oscillate around the vertical oscillating axis AXV. Vertical actuation sources are formed on the fixing frame  280 , at a location close to the vertical actuating beam  271 A and at a location close to the vertical actuating beam  271 B. Each of the vertical actuation sources is formed of a piezoelectric thin film, an upper electrode formed on the piezoelectric thin film, and a lower electrode formed under the piezoelectric thin film. By applying predetermined voltage to the vertical actuation sources, the vertical actuating beams  271 A and  271 B are twisted, and the movable frame  260  oscillates around the vertical oscillating axis AXV. 
     In the light scanning device according to the present embodiment, a wiring pattern for failure detection  43  is formed on the horizontal actuating beams  231 A and  231 B and the vertical actuating beams  271 A and  271 B. The wiring pattern for failure detection  43  has a terminal  44  at one end, and has a terminal  45  at the other end, and the terminals  44  and  45  are formed on the fixing frame  280 . From the terminal  44  on the fixing frame  280 , the wiring pattern for failure detection  43  is drawn on the vertical actuating beam  271 A, the movable frame  260 , the horizontal actuating beam  231 B, the mirror support  220 , the horizontal actuating beam  231 A, the movable frame  260 , and the vertical actuating beam  271 B, and the wiring pattern for failure detection  43  is connected to the terminal  45  on the fixing frame  280 . 
     In the light scanning unit illustrated in  FIG. 10 , by checking a conduction state between the terminals  44  and  45 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection  43  is drawn can be detected. That is, in a case in which a path between the terminals  44  and  45  is in a conductive state, it is determined that no breakage occurs in actuating beams (the horizontal actuating beams  231 A and  231 B, and the vertical actuating beams  271 A and  271 B) on which the wiring pattern for failure detection  43  is drawn. In a case in which a path between the terminals  44  and  45  is not in a conductive state, it is determined that breakage occurs at a certain point in the actuating beams on which the wiring pattern for failure detection  43  is drawn. As described above, in a MEMS structure functioning as an actuator, breakage of a beam can be detected regardless of whether a displacement sensor is present or not. 
       FIG. 11  is a plan view illustrating another example of an upper surface of a light scanning unit in a light scanning device according to the sixth embodiment. The light scanning unit in  FIG. 11  is similar to that in  FIG. 10 , except that a first wiring pattern  46  and a second wiring pattern  49  are provided, as a wiring pattern for failure detection, on the light scanning unit in  FIG. 11 . 
     In the light scanning device according to the present embodiment, the first wiring pattern  46  is drawn, from a terminal  47  on the fixing frame  280 , on the vertical actuating beam  271 A, the movable frame  260 , the horizontal actuating beam  231 B, the mirror support  220 , the horizontal actuating beam  231 A, the movable frame  260 , and the vertical actuating beam  271 B, and the first wiring pattern  46  is connected to a terminal  48  on the fixing frame  280 . The second wiring pattern  49  is drawn, from a terminal  50  on the fixing frame  280 , on the vertical actuating beam  271 A, the movable frame  260 , and the vertical actuating beam  271 B, and the second wiring pattern  49  is connected to a terminal  51  on the fixing frame  280 . The second wiring pattern  49  is not drawn on the horizontal actuating beams  231 A and  231 B. 
     In the light scanning unit illustrated in  FIG. 11 , by checking a conduction state between the terminals  47  and  48 , and a conduction state between the terminals  50  and  51 , occurrence of breakage in an actuating beam on which the wiring pattern for failure detection (the first or second wiring pattern  46  or  49 ) is drawn can be detected. That is, in a case in which a path between the terminals  47  and  48  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  271 A and  271 B and the horizontal actuating beams  231 A and  231 B on which the first wiring pattern  46  is drawn. In a case in which a path between the terminals  47  and  48  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  271 A and  271 B and the horizontal actuating beams  231 A and  231 B on which the first wiring pattern  46  is drawn. In a case in which a path between the terminals  50  and  51  is in a conductive state, it is determined that no breakage occurs in the vertical actuating beams  271 A and  271 B on which the second wiring pattern  49  is drawn. In a case in which a path between the terminals  50  and  51  is not in a conductive state, it is determined that breakage occurs at a certain point in the vertical actuating beams  271 A and  271 B on which the second wiring pattern  49  is drawn. 
     In the light scanning unit illustrated in  FIG. 11 , in a case in which no electrical conduction between the terminals  47  and  48  or between the terminals  50  and  51  can be detected, that is, in a case in which both the first and second wiring patterns  46  and  49  are disconnected, it is assumed that breakage occurs in the vertical actuating beams  271 A and  271 B on which both the first wiring pattern  46  and the second wiring pattern  49  are drawn. Also, in a case in which electrical conduction between the terminals  50  and  51  can be detected but electrical conduction between the terminals  47  and  48  cannot be detected, that is, in a case in which the second wiring pattern  49  is not disconnected but the first wiring pattern  46  is disconnected, it is assumed that breakage occurs in the horizontal actuating beams  231 A and  231 B on which only the first wiring pattern  46  is drawn. As described above, in a MEMS structure functioning as an actuator, breakage can be detected regardless of whether a displacement sensor is present or not. 
     Although preferable embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Various changes or enhancements can be made hereto within the scope of the present invention. For example, the above described embodiments describe a case in which an actuator is applied to a light scanning device having a mirror. However, what is driven by an actuator is not limited to a mirror, and the present invention is applicable to an actuator driving an article other than a mirror. Further, a light scanning device according to the above described embodiments is preferably applicable to optical coherence tomography for a funduscopic apparatus. In the optical coherence tomography for a funduscopic apparatus, different from a projection apparatus, a resonant actuation for high speed drive of a mirror is not required. Rather, as it is required that an oscillating angle of a mirror for scanning light can be freely configured, a light scanning device configured to drive a mirror by using a non-resonant actuation in both horizontal and vertical directions, as described in the above embodiments, is preferable. In a case in which the present invention is applied to an optical coherence tomography for a funduscopic apparatus, the optical coherence tomography can be configured to detect breakage of an actuating beam immediately and to stop emitting laser light in response to the detection of breakage of an actuating beam. Thus, in the optical coherence tomography to which the present invention is applied, even when breakage of an actuating beam has occurred, the optical coherence tomography can avoid damaging a fundus by emitting laser light to a specific point. The present invention can also be applied to a projecting apparatus, or a sensor such as an acceleration sensor. In a case in which the present invention is applied to a sensor, if breakage of an actuating beam occurs, a sensitivity of the sensor degrades and an erroneous value is output. By detecting breakage of an actuating beam quickly, a state in which breakage of an actuating beam has occurred can be detected quickly.