Abstract:
A scanning endoscope system includes: a fiber that guides illuminating light emitted from a light source; a first actuator provided on a side of the fiber, the first actuator expanding/contracting according to an applied voltage, thereby swinging the fiber; a second actuator disposed at a position facing the first actuator across the fiber, the second actuator expanding/contracting according to an applied voltage, thereby swinging the fiber; and a drive signal output section that applies a first drive signal that varies with reference to a first voltage that brings the first actuator into a contracted state to the first actuator and applies a second drive signal that varies with reference to a second voltage that brings the second actuator into a contracted state to the second actuator.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation application of PCT/JP2013/074102 filed on Sep. 6, 2013 and claims benefit of Japanese Application No. 2012-233024 filed in Japan on Oct. 22, 2012, the entire contents of which are incorporated herein by this reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a scanning endoscope system, and specifically relates to a scanning endoscope system for scanning an object to obtain an image. 
         [0004]    2. Description of the Related Art 
         [0005]    In endoscopes in a medical field, in order to reduce a burden on subjects, various techniques for thinning insertion portions to be inserted into body cavities of the subjects have been proposed. As an example of such techniques, a scanning endoscope including no solid image pickup device in a part corresponding to the aforementioned insertion portion and a system including the scanning endoscope are known. 
         [0006]    More specifically, the system including the scanning endoscope is configured to, for example, swing a distal end portion of an illumination fiber that guides illuminating light emitted from a light source section to two-dimensionally scan an object according to a pre-set scanning pattern, receive return light from the object via light-reception fibers disposed in the periphery of the illumination fiber and generate an image of the object based on the return light received via the light-reception fibers. As an example of those having a configuration similar to such system, the scanning beam system disclosed in U.S. Patent Application Publication No. 2008/0218824 is known. 
       SUMMARY OF THE INVENTION 
       [0007]    A scanning endoscope system according to an aspect of the present invention includes: a fiber that guides illuminating light emitted from a light source; a first actuator provided on a side of the fiber, the first actuator expanding/contracting according to an applied voltage, thereby swinging the fiber; a second actuator disposed at a position facing the first actuator across the fiber, the second actuator expanding/contracting according to an applied voltage, thereby swinging the fiber; and a drive signal output section that applies a first drive signal that varies with reference to a first voltage that brings the first actuator into a contracted state to the first actuator and applies a second drive signal that varies with reference to a second voltage that brings the second actuator into a contracted state to the second actuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagram illustrating a configuration of a main part of a scanning endoscope system according to an embodiment; 
           [0009]      FIG. 2  is a cross-sectional diagram for describing a configuration of an actuator section provided in the scanning endoscope; 
           [0010]      FIG. 3  is a diagram illustrating an example of a waveform of a first drive signal, which is used for driving the actuator section provided in the scanning endoscope; and 
           [0011]      FIG. 4  is a diagram illustrating an example of a waveform of a second drive signal, which is used for driving the actuator section provided in the scanning endoscope. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]    An embodiment of the present invention will be described below with reference to the drawings. 
         [0013]      FIGS. 1 to 4  relate to an embodiment of the present invention.  FIG. 1  is a diagram illustrating a configuration of a main part of a scanning endoscope system according to the embodiment. 
         [0014]    A scanning endoscope system  1  includes, for example, as illustrated in  FIG. 1 , a scanning endoscope  2  to be inserted into a body cavity of a subject, a body apparatus  3  to be connected to the scanning endoscope  2  and a monitor  4  to be connected to the body apparatus  3 . 
         [0015]    The scanning endoscope  2  includes an insertion portion  11  formed so as to have an elongated shape and flexibility that enable the insertion portion  11  to be inserted into a body cavity of a subject. Note that in a proximal end portion of the insertion portion  11 , e.g., a non-illustrated connector for detachably connecting the scanning endoscope  2  to the body apparatus  3  is provided. 
         [0016]    In a part from the proximal end portion to a distal end portion of the inside of the insertion portion  11 , an illumination fiber  12  having a function as a light-guiding section that guides illuminating light supplied from a light source unit  21  of the body apparatus  3  to a light collection optical system  14 , and light-reception fibers  13  that receive return light from an object and guide the return light to a detection unit  23  of the body apparatus  3  are inserted, respectively. 
         [0017]    An end portion of the illumination fiber  12  that includes a light entrance surface is disposed in a multiplexer  32  provided inside the body apparatus  3 . Also, an end portion of the illumination fiber  12  that includes a light exit surface is disposed in the vicinity of a light entrance surface of a lens  14   a  provided in the distal end portion of the insertion portion  11  in such a manner that the end portion is not fixed via, e.g., a fixing member. 
         [0018]    An end portion of each light-reception fiber  13  that includes a light entrance surface is fixedly disposed in the periphery of a light exit surface of a lens  14   b  in a distal end face of the distal end portion of the insertion portion  11 . Also, an end portion of each light-reception fiber  13  that includes a light exit surface is disposed in a demultiplexer  36  provided inside the body apparatus  3 . 
         [0019]    The light collection optical system  14  includes the lens  14   a  and the lens  14   b,  and is configured to collect illuminating light entered from the illumination fiber  12  and make the resulting illuminating light exit to the object. 
         [0020]    In a portion partway of the illumination fiber  12  on the distal end portion side of the insertion portion  11 , an actuator section  15  that is driven based on drive signals outputted from a driver unit  22  of the body apparatus  3  is provided. 
         [0021]    The illumination fiber  12  and the actuator section  15  are each disposed so as to have, for example, the positional relationship illustrated in  FIG. 2  in a cross-section perpendicular to a longitudinal axis direction of the insertion portion  11 .  FIG. 2  is a cross-sectional diagram for describing a configuration of the actuator section provided in the scanning endoscope. 
         [0022]    As illustrated in  FIG. 2 , a ferrule  41 , which serves as a joining member, is disposed between the illumination fiber  12  and the actuator section  15 . More specifically, the ferrule  41  is formed of, for example, zirconia (ceramic) or nickel. 
         [0023]    As illustrated in  FIG. 2 , the ferrule  41  is formed in the shape of a quadrangular prism, and includes side faces  42   a  and  42   c  perpendicular to an X-axis direction (transverse direction in the sheet) and side faces  42   b  and  42   d  perpendicular to a Y-axis direction (vertical direction in the sheet). Also, at a center of the ferrule  41 , the illumination fiber  12  is fixedly disposed. Note that the ferrule  41  may be formed in another shape other than a quadrangular prism as long as such shape is a prism. 
         [0024]    As illustrated in  FIG. 2 , the actuator section  15  includes an actuator  15   a  disposed along the side face  42   a,  an actuator  15   b  disposed along the side face  42   b,  an actuator  15   c  disposed along the side face  42   c  and an actuator  15   d  disposed along the side face  42   d.    
         [0025]    In other words, the actuator section  15 , which has a function as an optical scanning section, includes a pair of actuators  15   a  and  15   c  disposed at respective positions that face the Y-axis (or are symmetrical with respect to the Y-axis) across the illumination fiber  12 , along the X-axis direction, and a pair of actuators  15   b  and  15   d  disposed at respective positions that face the X-axis (or are symmetrical with respect to the X-axis) across the illumination fiber  12 , along the Y-axis direction. 
         [0026]    Each of the actuators  15   a,    15   b,    15   c  and  15   d  is configured to be driven according to a drive signal outputted from the driver unit  22 . 
         [0027]    The actuator  15   a  includes, for example, a piezoelectric element subjected to polarization processing in advance so that a polarization direction thereof agrees with a negative direction of the X-axis (direction from the right to the left in the sheet of  FIG. 2 ), and is configured to, upon application of a voltage of a positive value according to a drive signal outputted from the driver unit  22  (if a direction of an electric field generated as a result of supply of the drive signal is a forward direction relative to the polarization direction), contract along a Z-axis direction (normal direction in the sheet), and upon application of a voltage of a negative value according to a drive signal outputted from the driver unit  22  (if a direction of an electric field generated as a result of supply of the drive signal is a backward direction relative to the polarization direction), expand along the Z-axis direction. 
         [0028]    The actuator  15   b  includes, for example, a piezoelectric element subjected to polarization processing in advance so that a polarization direction thereof agrees with a negative direction of the Y-axis (direction from the top to the bottom in the sheet of  FIG. 2 ), and is configured to, upon application of a voltage of a positive value according to a drive signal outputted from the driver unit  22 , contract along the Z-axis direction, and upon application of a voltage of a negative value according to a drive signal outputted from the driver unit  22 , expand along the Z-axis direction. 
         [0029]    The actuator  15   c  includes, for example, a piezoelectric element subjected to polarization processing in advance so that a polarization direction thereof agrees with the negative direction of the X-axis, and is configured to, upon application of a voltage of a negative value according to a drive signal outputted from the driver unit  22 , contract along the Z-axis direction, and upon application of a voltage of a positive value according to a drive signal outputted from the driver unit  22 , expand along the Z-axis direction. 
         [0030]    The actuator  15   d  includes, for example, a piezoelectric element subjected to polarization processing in advance so that a polarization direction thereof agrees with the negative direction of the Y-axis, and is configured to, upon application of a voltage of a negative value according to a drive signal outputted from the driver unit  22 , contract in the Z-axis direction, and upon application of a voltage of a positive value according to a drive signal outputted from the driver unit  22 , expand along the Z-axis direction. 
         [0031]    Note that according to the present embodiment, the actuator section  15  is not limited to one configured using the actuators  15   a  to  15   d  having such polarization directions and expansion/contraction directions as described above, and may be configured using actuators  15   a  to  15   d  having other polarization directions and expansion/contraction directions. 
         [0032]    Inside the insertion portion  11 , a memory  16  with endoscope information stored in advance, the endoscope information including various pieces of information such as individual identification information for the scanning endoscope  2 , is provided. Upon the scanning endoscope  2  and the body apparatus  3  being connected, the endoscope information stored in the memory  16  is read from a controller  25  in the body apparatus  3 . 
         [0033]    The body apparatus  3  includes the light source unit  21 , the driver unit  22 , the detection unit  23 , a memory  24  and the controller  25 . 
         [0034]    The light source unit  21  includes a light source  31   a,  a light source  31   b,  a light source  31   c  and the multiplexer  32 . 
         [0035]    The light source  31   a  includes, for example, a laser light source, and is configured to, when the light source  31   a  is controlled to be turned on by the controller  25 , emit light of a red wavelength band (hereinafter also referred to as “R light”) to the multiplexer  32 . 
         [0036]    The light source  31   b  includes, for example, a laser light source, and is configured to, when the light source  31   b  is controlled to be turned on by the controller  25 , emit light of a green wavelength band (hereinafter also referred to as “G light”) to the multiplexer  32 . 
         [0037]    The light source  31   c  includes, for example, a laser light source, and is configured to, when the light source  31   c  is controlled to be turned on by the controller  25 , emit light of a blue wavelength band (hereinafter referred to as “B light”) to the multiplexer  32 . 
         [0038]    The multiplexer  32  is configured to combine the R light emitted from the light source  31   a,  the G light emitted from the light source  31   b,  and the B light emitted from the light source  31   c  and supply the resulting light to the light entrance surface of the illumination fiber  12 . 
         [0039]    The driver unit  22  has a function as a drive signal output section, and includes a signal generator  33 , D/A converters  34   a  and  34   b  and an amplifier  35 . 
         [0040]    The signal generator  33  is configured to generate respective drive signals for swinging the end portion of the illumination fiber  12  that includes the light exit surface, based on control performed by the controller  25 , and output the respective drive signals to the D/A converters  34   a  and  34   b.    
         [0041]    The D/A converters  34   a  and  34   b  are configured to convert the respective digital drive signals outputted from the signal generator  33  into analog drive signals and output the analog drive signals to the amplifier  35 . 
         [0042]    The amplifier  35  is configured to amplify the respective drive signals outputted from the D/A converters  34   a  and  34   b  and output the resulting drive signals to the actuator section  15 . 
         [0043]    The detection unit  23  includes the demultiplexer  36 , detectors  37   a,    37   b  and  37   c,  and A/D converters  38   a,    38   b  and  38   c.    
         [0044]    The demultiplexer  36  includes, e.g., a dichroic mirror, and is configured to split return light that has exited from the light exit surfaces of the light-reception fibers  13  into light of R (red) components, light of G (green) components and light of B (blue) components and make the light of R (red) components, the light of G (green) components and the light of B (blue) components exit to the respective detectors  37   a,    37   b  and  37   c.    
         [0045]    The detector  37   a  is configured to detect an intensity of the R light outputted from the demultiplexer  36 , generate an analog R signal according to the detected intensity of the R light and output the analog R signal to the A/D converter  38   a.    
         [0046]    The detector  37   b  is configured to detect an intensity of the G light outputted from the demultiplexer  36 , generate an analog G signal according the detected intensity of the G light and output the analog G signal to the A/D converter  38   b.    
         [0047]    The detector  37   c  is configured to detect an intensity of the B light outputted from the demultiplexer  36 , generate an analog B signal according to the detected intensity of the B light and output the analog B signal to the A/D converter  38   c.    
         [0048]    The A/D converter  38   a  is configured to convert the analog R signal outputted from the detector  37   a  into a digital R signal and output the digital R signal to the controller  25 . 
         [0049]    The A/D converter  38   b  is configured to convert the analog G signal outputted from the detector  37   b  into a digital G signal and output the digital G signal to the controller  25 . 
         [0050]    The A/D converter  38   c  is configured to convert the analog B signal outputted from the detector  37   c  into a digital B signal and output the digital B signal to the controller  25 . 
         [0051]    In the memory  24 , e.g., a control program for performing control of the body apparatus  3  is stored in advance. Also, in the memory  24 , endoscope information read by the controller  25  in the body apparatus  3  is stored. 
         [0052]    The controller  25  includes, e.g., a CPU, and is configured to read the control program stored in the memory  24 , and perform control of the light source unit  21  and the driver unit  22  based on the read control program. In other words, the actuator section  15 , which has a function as an optical scanning section, can swing the illumination fiber  12  so that positions in an object illuminated by illuminating light form a trajectory according to a predetermined scanning pattern, based on drive signals outputted from the driver unit  22  according to control performed by the controller  25  such as described above. 
         [0053]    The controller  25  operates so as to store the endoscope information outputted from the memory  16  when the insertion portion  11  is connected to the body apparatus  3 , in the memory  24 . 
         [0054]    The controller  25  is configured to generate an image based on the R signal, the G signal and the B signal outputted from the detection unit  23 , and display the generated image on the monitor  4 . 
         [0055]    Next, an operation, etc., of the scanning endoscope system  1  having the above described configuration will be described. 
         [0056]    When power sources of the respective components of the scanning endoscope system  1  are turned on, the endoscope information stored in the memory  16  in the insertion portion  11  is read by the controller  25 , and the read endoscope information is stored in the memory  24 . 
         [0057]    The controller  25  stores the endoscope information read from the memory  16  in the memory  24 , and then controls the light source unit  21  to switch the light sources  31   a,    31   b  and  31   c  from “off” to “on”, and controls the driver unit  22  to output first and second drive signals, which will be described later, from the signal generator  33 . 
         [0058]    Based on the control performed by the controller  25 , the signal generator  33  generates a first drive signal having, for example, the waveform illustrated in  FIG. 3  as a drive signal for driving the actuators  15   a  and  15   b  and outputs the first drive signal to the D/A converter  34   a.    FIG. 3  is a diagram illustrating an example of a waveform of the first drive signal used for driving the actuator section provided in the scanning endoscope. 
         [0059]    More specifically, based on the control performed by the controller  25 , the signal generator  33  generates, for example, a sine wave having a voltage value periodically varying with a positive voltage value VP 1  that is larger than zero as a center and having an amplitude value (peak value) that does not exceed (does not fall below) a negative voltage value VN 1  corresponding to a coercive electric field in each of the actuators  15   a  and  15   b,  as a first drive signal (see  FIG. 3 ). 
         [0060]    Also, based on the control performed by the controller  25 , the signal generator  33  generates a second drive signal having, for example, the waveform illustrated in  FIG. 4  as a drive signal for driving the actuators  15   c  and  15   d  and outputs the second drive signal to the D/A converter  34   b.    FIG. 4  is a diagram illustrating an example of a waveform of the second drive signal used for driving the actuator section provided in the scanning endoscope. 
         [0061]    More specifically, based on the control performed by the controller  25 , the signal generator  33  generates, for example, a sine wave having a voltage value periodically varying with a negative voltage value VN 2  that is smaller than zero as a center and having an amplitude value (peak value) that does not exceed (is not larger than) a positive voltage value VP 2  corresponding to a coercive electric field in each of the actuators  15   c  and  15   d,  as a second drive signal (see  FIG. 4 ). 
         [0062]    Note that the aforementioned negative voltage value VN 1  is a value determined according to a thickness in the polarization direction of the piezoelectric element in each of the actuators  15   a  and  15   b.  Also, the aforementioned positive voltage value VP 2  is a value determined according to a thickness in the polarization direction of the piezoelectric element in each of the actuators  15   c  and  15   d.  Thus, for example, if the actuators  15   a  to  15   d  are formed by respective piezoelectric elements having a same thickness in the respective polarization directions, a relationship of VN1=VP2 holds between the negative voltage value VN 1  and the positive voltage value VP 2 . 
         [0063]    The above-described first and second drive signals are generated so as to have a same phase and provide the relationship of VP1=VN2 in order to balance among forces applied to the ferrule  41  as a result of driving of the actuators  15   a  to  15   d.    
         [0064]    Then, the first drive signal generated by the signal generator  33  is outputted to the actuators  15   a  and  15   b  through the D/A converter  34   a  and the amplifier  35 . Also, the second drive signal generated by the signal generator  33  is outputted to the actuators  15   c  and  15   d  through the D/A converter  34   b  and the amplifier  35 . 
         [0065]    Here, where an alternating-current voltage according to the above-described first drive signal is applied to the actuator  15   a,  and an alternating-current voltage according to the above-described second drive signal is applied to the actuator  15   c,  a force applied to the ferrule  41  as a result of expansion/contraction of the actuator  15   a  and a force applied to the ferrule  41  as a result of expansion/contraction of the actuator  15   c  are cancelled out. Thus, as a result of the alternating-current voltage according to the first drive signal being applied to the actuator  15   a  and the alternating-current voltage according to the second drive signal being applied to the actuator  15   c,  the illumination fiber  12  can be swung while a position in the X-axis direction of the ferrule  41  in a case where no voltage is applied to either of the actuators  15   a  and  15   c  (where neither of the actuators  15   a  and  15   c  expands/contracts) is maintained. 
         [0066]    Also, where the alternating-current voltage according to the first drive signal is applied to the actuator  15   b  and the alternating-current voltage according to the second drive signal is applied to the actuator  15   d,  a force applied to the ferrule  41  as a result of expansion/contraction of the actuator  15   b  and a force applied to the ferrule  41  as a result of expansion/contraction of the actuator  15   d  are cancelled out. Thus, as a result of the alternating-current voltage according to the first drive signal being applied to the actuator  15   b  and the alternating-current voltage according to the second drive signal being applied to the actuator  15   d,  the illumination fiber  12  can be swung while a position in the Y-axis direction of the ferrule  41  in a case where no voltage is applied to either of the actuators  15   b  and  15   d  (where neither of the actuators  15   b  and  15   d  expands/contracts) is maintained. 
         [0067]    In a case where the illumination fiber  12  is swung by means of a conventional method in which, for example, an alternating-current voltage according to a drive signal whose voltage value periodically varies with a voltage value of zero as a center is applied to each of the actuators  15   a  to  15   d,  there is substantially no need to take balancing of forces applied to the ferrule  41  into account; however, in order to maintain polarization of the actuators  15   a  to  15   d,  there is a need to set an amplitude value within a range between the negative voltage value VN 1  corresponding to a coercive electric field in each of the actuators  15   a  and  15   b  and the positive voltage value VP 2  corresponding to a coercive electric field in each of the actuators  15   c  and  15   d  (within a range of no less than VN 1  and no more than VP 2 ). 
         [0068]    On the other hand, according to the present embodiment, the alternating-current voltage according to the first drive signal whose voltage value periodically varies with the positive voltage value VP 1  as a center is applied to the actuators  15   a  and  15   b  and the alternating-current voltage according to the second drive signal whose voltage value periodically varies with the negative voltage value VN 2  as a center is applied to the actuators  15   c  and  15   d,  thereby relaxing the limitations on the amplitude value (peak value) by the negative voltage value VN 1  and the positive voltage value VP 2 . As a result, the present embodiment enables the illumination fiber  12  to be swung in a wide area compared to the conventional method, that is, enables a scanning area of an object to be widened compared to the conventional method. 
         [0069]    It should be understood that the present invention is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit of the invention.