OPTICAL SCANNING APPARATUS AND OPTICAL SCANNING OBSERVATION APPARATUS

Included are an optical fiber (11), a driver (21) that drives an emission end (11b) of the optical fiber (11), a current detector (55) that detects a current flowing in the driver (21), and a controller (31) that scans light emitted from the optical fiber (11) by controlling the driver (21) based on output of the current detector (55). The driver (21) comprises vibration elements (28a to 28d), ground terminals of the vibration elements (28a to 28d) are connected in common to the driver (21), and the current detector (55) detects the current at the power supply terminal of the vibration elements (28a to 28d).

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuing Application based on International Application PCT/JP2015/003001 filed on Jun. 16, 2015, which in turn claims priority to Japanese Patent Application No. 2014-125470 filed on Jun. 18, 2014, the entire disclosure of these earlier applications being incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to an optical scanning apparatus and an optical scanning observation apparatus that optically scan an object by vibrating an optical fiber.

BACKGROUND

One known example of an optical scanning observation apparatus vibrates the emission end of an optical fiber to scan a beam of light from the optical fiber over an object and detects light that is reflected, scattered, or the like by the object or detects fluorescent light or the like generated by the object (for example, see JP 4672023 B2 (PTL 1)).

CITATION LIST

Patent Literature

SUMMARY

An optical scanning apparatus according to this disclosure includes:

an optical fiber;

a driver configured to drive an emission end of the optical fiber;

a current detector configured to detect a current flowing in the driver; and

a controller configured to scan light emitted from the optical fiber by controlling the driver based on output of the current detector; wherein

the driver comprises a plurality of vibration elements;

ground terminals of the vibration elements are connected in common to the driver; and

the current detector detects the current at a power supply terminal of the vibration elements.

The current detector may include a current transformer.

The vibration elements may include a plurality of first vibration elements that vibrate the emission end in a first direction and a plurality of second vibration elements that vibrate the emission end in a second direction different from the first direction;

power supply terminals of the first vibration elements may be connected in common to the driver; and

power supply terminals of the second vibration elements may be connected in common to the driver.

The controller may control the driver based on output of the current detector at a time when an amplitude of the current is maximized.

The controller may control the driver so that a maximum value of the current detected by the current detector becomes constant.

Furthermore, an optical scanning observation apparatus includes:

the aforementioned optical scanning apparatus;

a photodetector configured to detect light obtained from an object by optical scanning with the optical scanning apparatus and to convert the light to an electrical signal; and

an image processor configured to generate an image based on the electrical signal output from the photodetector.

DETAILED DESCRIPTION

Embodiments are described below with reference to the drawings.

FIG. 1is a block diagram schematically illustrating the structure of an optical scanning observation apparatus according to Embodiment 1. The optical scanning observation apparatus inFIG. 1constitutes an optical scanning endoscope apparatus10. The optical scanning endoscope apparatus10includes a scope (endoscope)20, a control device body30, and a display40.

The control device body30includes a controller31that controls the optical scanning endoscope apparatus10overall, a light emission timing controller32, lasers33R,33G, and33B, and a combiner34. The laser33R emits red laser light, the laser33G emits green laser light, and the laser33B emits blue laser light. Under the control of the controller31, the light emission timing controller32controls the light emission timing of the three lasers33R,33G, and33B. For example, Diode-Pumped Solid-State (DPSS) lasers or laser diodes may be used as the lasers33R,33G, and33B. The laser light emitted from the lasers33R,33G, and33B is combined by the combiner34and is incident as white illumination light on an optical fiber11for illumination, which is formed by a single-mode fiber. The combiner34may, for example, be configured to include a dichroic prism or the like. The configuration of the light source in the optical scanning endoscope apparatus10is not limited to this example. A light source with one laser may be used, or a plurality of other light sources may be used. The lasers33R,33G, and33B and the combiner34may be stored in a housing that is separate from the control device body30and is joined to the control device body30by a signal wire.

The optical fiber11for illumination extends to the tip of the scope20. Illumination light incident on the optical fiber11for illumination via the combiner34is guided to the tip of the scope20and irradiated towards an object100. At this time, the emission end of the optical fiber11for illumination is subjected to vibration driving by the driver21. As a result, the observation surface of the object100is scanned in2D by illumination light emitted from the optical fiber11for illumination. The driver21is controlled by the drive controller/resonance frequency detector38of the below-described control device body30. Signal light, such as reflected light, scattered light, fluorescent light, and the like obtained from the object100by irradiation with illumination light is incident on the end face of an optical fiber bundle12for detection, which is formed by multi-mode fibers extending inside the scope20, and the signal light is then guided to the control device body30.

The control device body30further includes a photodetector35for processing signal light, an analog/digital converter (ADC)36, an image processor37, and a drive controller/resonance frequency detector38. The photodetector35divides the signal light optically guided by the optical fiber bundle12for detection into spectral components and converts the spectral components into electric signals with a photodiode or the like. The ADC36converts the analog electric signals output from the photodetector35into digital signals and outputs the digital signals to the image processor37. Based on information such as the amplitude, phase, and the like of vibration voltage applied by the drive controller/resonance frequency detector38, the controller31calculates information on the scanning position along the scanning trajectory of laser illumination light and provides the information to the image processor37. The image processor37sequentially stores pixel data (pixel values) of the object100in a non-illustrated memory based on the digital signals output by the ADC36and the scanning position information from the controller31. After completion of scanning or during scanning, the image processor37generates an image of the object100by performing image processing, such as interpolation, as necessary and displays the image on the display40.

In the above-described processing, the controller31synchronously controls the light emission timing controller32, the photodetector35, the drive controller/resonance frequency detector38, and the image processor37.

FIG. 2is a schematic overview of the scope20. The scope20includes an operation part22and an insertion part23. The optical fiber11for illumination, the optical fiber bundle12for detection, and wiring cables13extending from the control device body30are each connected to the operation part22. The optical fiber11for illumination, optical fiber bundle12for detection, and wiring cables13pass through the insertion part23and extend to a tip24(the portion within the dotted line inFIG. 2) of the insertion part23.

FIG. 3is a cross-sectional diagram illustrating an enlargement of the tip24of the insertion part23of the scope20inFIG. 2. The tip24includes the driver21, projection lenses25aand25b, the optical fiber11for illumination that passes through the central portion of the scope20, and the optical fiber bundle12for detection that passes through the peripheral portion.

The driver21includes an actuator tube27fixed to the inside of the insertion part23of the scope20by an attachment ring26, a fiber holding member29disposed inside the actuator tube27, and piezoelectric elements28ato28d(seeFIGS. 4A and 4B). The optical fiber11for illumination is supported by the fiber holding member29, and the emission end11bfrom the fixed end11aby the fiber holding member29to the emission end face11cis capable of oscillation. The optical fiber bundle12for detection is disposed to pass through the peripheral portion of the insertion part23and extends to the end of the tip24. A non-illustrated detection lens is also provided at the tip of each fiber in the optical fiber bundle12for detection.

Furthermore, the projection lenses25aand25band the detection lenses are disposed at the extreme end of the tip24. The projection lenses25aand25bare configured so that laser light emitted from the emission end face11cof the optical fiber11for illumination is roughly concentrated on the object100. The detection lenses are disposed so that light that is reflected, scattered, refracted, or the like by the object100(light that interacts with the object100), fluorescent light, or the like due to laser light concentrated on the object100is captured as signal light, concentrated on the optical fiber bundle12for detection disposed behind the detection lenses, and combined. The projection lenses are not limited to a double lens structure and may be structured as a single lens or as three or more lenses.

FIG. 4Aillustrates the vibration driving mechanism of the driver21and the emission end11bof the optical fiber11for illumination in the optical scanning endoscope apparatus10.FIG. 4Bis a cross-sectional diagram along the A-A line inFIG. 4A. The optical fiber11for illumination passes through the center of the fiber holding member29, which has a prismatic shape, and is fixed and held by the fiber holding member29. The four sides of the fiber holding member29respectively face the ±Y direction and the ±X direction when the optical axis of the optical fiber11for illumination in the fiber holding member29is in the Z direction, and directions that traverse the optical axis in a plane orthogonal to the optical axis and are orthogonal to each other are the Y direction (first direction) and the X direction (second direction). A pair of piezoelectric elements28aand28cfor driving in the Y direction are fixed onto the sides of the fiber holding member29in the ±Y direction, and a pair of piezoelectric elements28band28dfor driving in the X direction are fixed onto the sides in the ±X direction.

The piezoelectric elements28ato28deach constitute a vibration element, and the ground terminals (one of the surface electrodes) of the piezoelectric elements are connected in common in the driver21. For example, the ground terminals of the piezoelectric elements28ato28dare connected in common on the fiber holding member29by the piezoelectric elements28ato28dbeing mounted on a common connection wiring pattern29aformed on the fiber holding member29. The corresponding wiring cable13from the drive controller/resonance frequency detector38of the control device body30is connected to the power supply terminal (the other surface electrode) of the piezoelectric elements28ato28d. Similarly, a corresponding wiring cable13from the drive controller/resonance frequency detector38is connected to the connection wiring pattern29aof the fiber holding member29.

In this way, by connecting the ground terminals of the piezoelectric elements28ato28dto the driver21in common, five wiring cables13are sufficient for electrically connecting the piezoelectric elements28ato28dwith the drive controller/resonance frequency detector38. By contrast, when the ground terminals of the piezoelectric elements28ato28dare not connected in common, two wiring cables are required for each of the piezoelectric elements28ato28d, making it necessary to dispose a total of eight wiring cables inside the insertion part23of the scope20. Accordingly, this embodiment allows a reduction in the number of wiring cables13, with a corresponding reduction in size and diameter of the insertion part23. Furthermore, the ground terminals of the piezoelectric elements28ato28dcan be connected in common on the fiber holding member29by, for example, the piezoelectric elements28ato28dbeing mounted on the common connection wiring pattern29aformed on the fiber holding member29, thereby also simplifying the structure of the driver21.

FIG. 5is a block diagram schematically illustrating the structure of the drive controller/resonance frequency detector38. The drive controller/resonance frequency detector38includes a Digital Direct Synthesis (DDS) transmitter51ya, Digital/Analog Converter (DAC)52ya, and amplifier53yacorresponding to the piezoelectric element28a, a DDS51xb, DAC52xb, and amplifier53xbcorresponding to the piezoelectric element28b, a DDS51yc, DAC52yc, and amplifier53yccorresponding to the piezoelectric element28c, and a DDS51xd, DAC52xd, and amplifier53xdcorresponding to the piezoelectric element28d. Unless otherwise specified, these components are collectively abbreviated as DDSes51, DACs52, and amplifiers53. The DDSes51receive input of a corresponding control signal from the controller31and generate a digital driving signal. After each of these digital driving signals is converted to an analog signal by the corresponding DAC52, the analog signal is amplified by the corresponding amplifier53. Via the corresponding wiring cable13, the output of the amplifiers53is applied to the corresponding one of the piezoelectric elements28ato28dpositioned at the tip24of the scope20. As a result, the piezoelectric elements28ato28dare driven by vibration.

Voltage of equivalent magnitude and opposite sign is applied across the piezoelectric elements28band28din the X direction. As a result, when one of the piezoelectric elements28band28dextends and the other contracts, the fiber holding member29is flexed. Repeating this process causes the fiber holding member29to vibrate in the X direction. Similarly, voltage of equivalent magnitude and opposite sign is applied across the piezoelectric elements28aand28cin the Y direction, causing the fiber holding member29to vibrate in the Y direction.

The drive controller/resonance frequency detector38applies vibration voltage of the same frequency or vibration voltage of different frequencies to the piezoelectric elements28band28dfor driving in the X direction and the piezoelectric elements28aand28cfor driving in the Y direction. Upon vibration driving of each of the piezoelectric elements28aand28cfor driving in the Y direction and the piezoelectric elements28band28dfor driving in the X direction, the emission end11bof the optical fiber11for illumination illustrated inFIG. 3,FIG. 4A, andFIG. 4Bvibrate. As a result, the emission end face11cis then selected, and the laser light emitted from the emission end face11csequentially scans the surface of the object100.

The emission end11bof the optical fiber11for illumination is subjected to vibration driving at the resonance frequency in one or both of the X direction and the Y direction. The resonance frequency of the emission end11b, however, changes based on environmental conditions and also changes over time. Therefore, in this embodiment, the resonance frequency of the emission end11bof the optical fiber11for illumination is detected in the drive controller/resonance frequency detector38.

InFIG. 5, in order to detect the resonance frequency of the emission end11b, the drive controller/resonance frequency detector38includes, at the power supply terminal side of the piezoelectric elements28ato28d, current detectors55ya,55xb,55yc, and55xdthat detect the current flowing in the corresponding piezoelectric elements28ato28d, and voltage detectors56ya,56xb,56yc, and56xdthat detect the applied voltage. Unless otherwise specified, these components are collectively abbreviated as current detectors55and voltage detectors56. The current detectors55may be configured using Current Transformers (CTs). The current detectors55are not limited to CTs and may be configured with a known integrated circuit or the like. In particular, by using CTs, a low-voltage circuit configuration is possible even when the voltage applied to the corresponding piezoelectric element is a relatively high voltage, thus allowing a reduction in size and cost of the current detectors55. Using CTs also allows the detection system to be arranged on the 2D circuit side, which offers the advantage of simplifying insulation from the patient circuit.

The drive controller/resonance frequency detector38further includes Analog/Digital Converters (ADCs), which convert, to a digital signal, the current and voltage detected by the current detectors55and voltage detectors56respectively corresponding to the piezoelectric elements28ato28d, and a resonance frequency detector59that detects the resonance frequency in the corresponding vibration direction from the phase difference in the current and voltage that were converted to digital signals. To simplify the drawing,FIG. 5only shows the ADC57xbcorresponding to the current detector55xband the ADC58xbcorresponding to the voltage detector56xb. The other ADCs are omitted from the drawing. Unless otherwise specified, these components are collectively abbreviated as ADCs57and ADCs58. The output of the ADCs57and the ADCs58is also provided to the controller31.

Through control by the controller31, the ADCs57convert the output of the current detectors55to a digital signal at the time at which the amplitude of the current detected by the current detectors55reaches a maximum. Similarly, through control by the controller31, the ADCs58convert the output of the voltage detectors56to a digital signal at the time at which the amplitude of the voltage reaches a maximum. As a result, the current and voltage can be detected with a high S/N ratio, thus allowing accurate driving control.

Operations of the optical scanning endoscope apparatus10are now described with reference toFIG. 6andFIGS. 7A to 7E.FIG. 6is a flowchart describing operations.FIGS. 7A to 7Eillustrate the operation timing and the content of the operation of each component, along with the scanning trajectory of illumination light.FIG. 7Ashows the amplitude A of driving voltage,FIG. 7Bshows the frequency f of driving voltage,FIG. 7Cshows laser output P of the lasers33R,33G, and33B,FIG. 7Dshows the waveform of output voltage Vf, andFIG. 7Eshows the scanning trajectory of illumination light emitted from the optical fiber11for illumination. InFIGS. 7A to 7D, the horizontal axis t represents time.

First, the initial state is a state in which operation of the emission end11bof the optical fiber11for illumination is suspended (step S01). This state is represented as period I inFIG. 7A.

Next, the controller31starts a resonance frequency detection step to detect the resonance frequency (step S02). The resonance frequency detection step corresponds to period II inFIG. 7A. In period II, vibration voltage with an amplitude A equivalent to a predetermined amplitude Vsweep, a phase that is shifted by 90° between the X and Y directions, and a frequency f that increases over time is applied to the piezoelectric elements28band28din the X direction and the piezoelectric elements28aand28cin the Y direction (seeFIGS. 7A, 7B, and 7D). As a result, the vibration frequency of the emission end11bof the optical fiber11for illumination is swept within a predetermined frequency range. The predetermined frequency range is predicted in advance as a range that is around the resonance frequency at the time of design and over which the resonance frequency can vary. At this time, the lasers33R,33G, and33B are not yet turned on (FIG. 7C). As a result, the emission end face11cof the optical fiber11for illumination vibrates so as to trace a circle (FIG. 7E).

While the frequency of the driving voltage is increasing, the current signals and voltage signals detected by the corresponding current detectors55and voltage detectors56are monitored by the resonance frequency detector59. The resonance frequency detector59detects the resonance frequency by detecting the shift in phase of the current signal and the voltage signal (the temporal shift of the maximum value of each signal). In general, the frequency characteristics of the vibration circuit's impedance and of the phase shift in current and voltage are known to be as inFIG. 8AandFIG. 8B. At the time of vibration at the resonance frequency, the impedance is minimized, and the phase shift is zero. The resonance frequency detector59identifies the frequency fr at the time that the phase shift of the current signal from the corresponding current detector55and the voltage signal from the corresponding voltage detector56is zero as being the resonance frequency and outputs the resonance frequency to the controller31.

The controller31determines the subsequent driving frequency to be near the detected resonance frequency fr (step S03). The driving frequency allows driving at a frequency near the resonance frequency fr, but the driving frequency need not match fr exactly and may be a slightly different value. The driving frequency determination step to determine the driving frequency is performed during period II.

If the resonance frequency is not detected in the resonance frequency detection step (step S02), either there is no output from the resonance frequency detector59to the controller31, or a signal detecting an error is transmitted. In this case, the controller31determines that an error has occurred, suspends the apparatus, and displays a warning indicating an error on the display40. Possible examples of when the resonance frequency is not detected include the optical fiber11for illumination being broken and an error in the piezoelectric elements28ato28d.

Immediately before the end of period II, the controller31turns on the lasers33R,33G, and33B. Next, as the scanning step, the object is optically scanned (step S04). In other words, in period III, the controller31fixes the driving frequency f of the voltage applied to the piezoelectric elements28band28din the X direction and the piezoelectric elements28aand28cin the Y direction at the resonance frequency fr (FIG. 7B) and increases the amplitude A of the driving voltage from zero to the maximum value Vmax over time (FIG. 7A). As a result, the light emitted from the optical fiber11for illumination follows a spiral trajectory in which the radius increases over time (FIG. 7E). At this time, based on output of the ADCs57, the controller31performs feedback control so that the maximum value of the current detected by the current detectors55becomes constant. The controller31also monitors output of the ADCs58.

Next, upon detecting that the amplitude A of the driving voltage output by the ADCs58has reached the maximum value Vmax, the controller31suspends oscillation of the lasers33R,33G, and33B and also gradually suspends vibration of the optical fiber11for illumination (step S05). Vibration is suspended by rapidly decreasing the amplitude A of the driving voltage in period IV, which is shorter than period III. By the above-described spiral scanning, a circular region of the object100is scanned in 2D, and one frame of an image is acquired. In the case of acquiring the next frame, the controller31returns to step S02again and repeats step S02through step S05. Accordingly, in this embodiment, the controller31and the drive controller/resonance frequency detector38constitute a controller that controls the driver21.

According to the optical scanning endoscope apparatus10of this embodiment, as described above, the insertion part23of the scope20can be reduced in size and diameter, the structure of the driver21can be simplified, the current detectors55can be reduced in size and cost, accuracy of current detection can be improved, and insulation from the patient circuit can be simplified, among other effects. The optical scanning endoscope apparatus10detects the resonance frequency fr before scanning the object100and acquires an image by optically scanning the object under observation at this resonance frequency fr. Therefore, it is possible to prevent a decrease in performance due to misalignment with the resonance frequency of the fiber resulting from variability between apparatuses and change over time, and the driving frequency can be adjusted appropriately. Always subjecting the emission end11bof the optical fiber11for illumination to vibration driving at a frequency near the resonance frequency also allows scanning with good energy efficiency.

Furthermore, since the resonance frequency is detected before each image frame is acquired, the driving frequency can be adjusted to an appropriate value immediately if the resonance frequency changes for a reason such as a temperature increase during operation of the optical scanning endoscope apparatus10. As a result, the emission end face11cof the optical fiber11for illumination can be vibrated over a stable trajectory. It is thus expected that a more stable image can be acquired and displayed.

Furthermore, in the resonance frequency detection step (step S02), when the resonance frequency cannot be detected, the apparatus is suspended and a warning is issued, thereby allowing early detection of an error in the apparatus and preventing malfunction or increased damage.

Instead of detecting the resonance frequency and determining the driving frequency for the second time onward after scanning is suspended in period IV, these operations may be performed by sweeping the vibration frequency f around the resonance frequency and detecting the resonance frequency while vibration is being reduced during period IV (step S05). In this case, optical scanning can start immediately after suspension of vibration (step S03), which increases the frame rate and allows acquisition of a better image.

FIGS. 9A, 9B, and 9Care expanded diagrams illustrating the tip of the scope in the optical scanning endoscope apparatus according to Embodiment 2. This embodiment has the structure of the optical scanning endoscope apparatus10of Embodiment 1, except that instead of piezoelectric elements, the driver21is configured using a permanent magnet63fixed to the optical fiber11for illumination and coils62ato62dfor generation of a deflecting magnetic field (electromagnetic coils) that drive the permanent magnet63. Portions identical to the structure described in Embodiment 1 are labeled with the same reference signs, and a description thereof is omitted. The differences from Embodiment 1 are described below.FIG. 9Ais a cross-sectional diagram of the tip24of the scope20,FIG. 9Bis an enlarged perspective view of the driver21inFIG. 9A, andFIG. 9Cis a cross-sectional view perpendicular to the axis of the optical fiber11for illumination, illustrating a portion including the coils62ato62dfor generation of a deflecting magnetic field and the permanent magnet63inFIG. 9B.

At a portion of the emission end11bof the optical fiber11for illumination, the permanent magnet63, which is magnetized in the axial direction of the optical fiber11for illumination and includes a through-hole, is joined to the optical fiber11for illumination by the optical fiber11being passed through the through-hole. A square tube61, one end of which is fixed to the attachment ring26, is provided so as to surround the emission end11b, and flat coils62ato62dfor generation of a deflecting magnetic field are provided on the sides of the square tube61at a portion thereof opposing one pole of the permanent magnet63.

The pair of coils62aand62cfor generation of a deflecting magnetic field in the Y direction and the pair of coils62band62dfor generation of a deflecting magnetic field in the X direction are each disposed on opposing sides of the square tube61, and a line connecting the center of the coil62afor generation of a deflecting magnetic field with the center of the coil62cfor generation of a deflecting magnetic field is orthogonal to a line connecting the center of the coil62bfor generation of a deflecting magnetic field with the center of the coil62dfor generation of a deflecting magnetic field near the central axis of the square tube61when the optical fiber11for illumination is disposed therein at rest.

The coils62ato62dfor generation of a deflecting magnetic field each constitute a vibration element, and the ground terminals (one of the surface electrodes) of the coils are connected in common in the driver21. For example, the ground terminals of the coils62ato62dfor generation of a deflecting magnetic field are connected in common on the square tube61by the ground terminals being adhered to a common connection wiring pattern61aformed on the square tube61. The corresponding wiring cable13from the drive controller/resonance frequency detector38of the control device body30is connected to the power supply terminal (the other end) of each of the coils62ato62dfor generation of a deflecting magnetic field. Similarly, a corresponding wiring cable13from the drive controller/resonance frequency detector38is connected to the connection wiring pattern61aof the square tube61. In this way, the driving current from the drive controller/resonance frequency detector38is supplied to the coils62ato62dfor generation of a deflecting magnetic field, and due to electromagnetic action with the permanent magnet63, the emission end11bof the optical fiber11for illumination is vibrated.

FIG. 10is a flowchart illustrating operations of the optical scanning endoscope apparatus10according to this embodiment. Since the content of the steps inFIG. 10is nearly the same as that of the steps in Embodiment 1, the steps inFIG. 10are numbered by adding10to the reference numeral of the corresponding steps inFIG. 6. In this embodiment, however, after operation of the apparatus begins, the resonance frequency is detected only once (step S12), and the driving frequency is determined (step S13). Subsequently, acquisition of image data by optically scanning the object (step S14) is repeated until the controller31suspends acquisition of the next frame (step S16). Since the remaining structure and operations are similar to those of Embodiment 1, identical or corresponding constituent elements are labeled with the same reference signs, and a description thereof is omitted.

According to this embodiment, the number of wiring cables13for electrically connecting the coils62ato62dfor generation of a deflecting magnetic field with the drive controller/resonance frequency detector38can be reduced, thereby obtaining the same effects as in Embodiment 1, such as a reduction in size and diameter of the insertion part23of the scope20and simplification of the structure of the driver21. Furthermore, after detecting the resonance frequency once, image frames are acquired by repeated optical scanning. Therefore, endoscope images can be acquired at a higher frame rate than in Embodiment 1. In this embodiment, since the vibration elements are formed by coils, the current detectors55are not limited to current transformers, and a variety of known current sensors may be used.

FIG. 11is a block diagram schematically illustrating the main structure of an optical scanning endoscope apparatus according to Embodiment 3. This embodiment has the structure of the optical scanning endoscope apparatus10of Embodiment 1, except that the power supply terminals of the piezoelectric elements (first vibration element)28aand28cthat vibrate the emission end11bof the optical fiber11for illumination in the Y direction and the power supply terminals of the piezoelectric elements (second vibration element)28band28dthat vibrate the emission end11bin the X direction are respectively connected in parallel at the driver21side. Portions identical to the structure described in Embodiment 1 are labeled with the same reference signs, and a description thereof is omitted. The differences from Embodiment 1 are described below.

The same driving signal is applied to the piezoelectric elements28aand28cvia the corresponding DDS51y, DAC52y, amplifier53y, and wiring cable13. Similarly, the same driving signal is applied to the piezoelectric elements28band28dvia the corresponding DDS51x, DAC52x, amplifier53x, and wiring cable13. The piezoelectric elements28aand28cthat form a pair are configured so that when the applied driving signal has a certain polarity, a first one of the piezoelectric elements28aand28cexpands and a second one of the piezoelectric elements28aand28ccontracts, whereas when the driving signal has the opposite polarity, the second one of the piezoelectric elements28aand28cexpands and the first one of the piezoelectric elements28aand28ccontracts. Similarly, the piezoelectric elements28band28dthat form a pair are configured so that when the applied driving signal has a certain polarity, a first one of the piezoelectric elements28band28dexpands and a second one of the piezoelectric elements28band28dcontracts, whereas when the driving signal has the opposite polarity, the second one of the piezoelectric elements28band28dexpands and the first one of the piezoelectric elements28band28dcontracts. As a result, the piezoelectric elements28ato28dare driven by vibration.

The combined current flowing in the piezoelectric elements28aand28cis detected by the current detector55y, which is provided with a Current Transformer (CT), is converted to a digital signal by the ADC57y, and is input into the resonance frequency detector59. Similarly, the combined current flowing in the piezoelectric elements28band28dis detected by the current detector55x, which is provided with a Current Transformer (CT), is converted to a digital signal by the ADC57x, and is input into the resonance frequency detector59. The vibration voltage applied to the piezoelectric elements28aand28cis detected by the voltage detector56y, is converted to a digital signal by the ADC58y, and is input into the resonance frequency detector59. Similarly, the vibration voltage applied to the piezoelectric elements28band28dis detected by the voltage detector56x, is converted to a digital signal by the ADC58x, and is input into the resonance frequency detector59. The output of the ADCs57xand57yand of the ADCs58xand58yis also provided to the controller31. To simplify the drawing,FIG. 11only shows the ADC57xcorresponding to the current detector55xand the ADC58xcorresponding to the voltage detector56x. The other ADCs are omitted from the drawing. The remaining structure and operations are similar to those of Embodiment 1.

According to this embodiment, in the driver21, the ground terminals of the piezoelectric elements28ato28dare connected in common, and the power supply terminals of the piezoelectric elements28band28dforming a pair in the X direction and the power supply terminals of the piezoelectric elements28aand28cforming a pair in the Y direction are respectively connected in parallel. Accordingly, the total number of wiring cables13for electrically connecting the piezoelectric elements28ato28dwith the drive controller/resonance frequency detector38is reduced to three. Hence, the number of wiring cables13can be reduced beyond the number in Embodiment 1, which is advantageous in allowing a further reduction in size and diameter of the insertion part23of the scope20.

This disclosure is not limited only to the above embodiments, and a variety of changes or modifications may be made. For example, the optical scanning is not limited to being spiral scanning and may instead be raster scanning. In this case, the optical fiber for illumination is only vibrated at the resonance frequency in one of the XY scanning directions. Furthermore, the vibration driving means is not limited to a method using coils and a magnet or a method using piezoelectric elements. Any other vibration driving means may be used. In the case of using coils, two coils in series may constitute one vibration element. Furthermore, the resonance frequency is not limited to being detected upon each scanning or at the start of driving the apparatus and may instead be detected at various timings. For example, possible settings include one detection per a plurality of scans, one detection per day, or detection upon user instruction. This disclosure is not limited to an endoscope apparatus and may also be adapted for use in another apparatus such as a microscope or a projector.

REFERENCE SIGNS LIST

11Optical fiber for illumination

62ato62dCoil for generation of a deflecting magnetic field