JP2014147462A - Calibration method and scanning type endoscope system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic calibration method of a scanning type endoscope system capable of giving a uniform calibration result free from variations by operators.SOLUTION: An automatic calibration method comprises: a light scanning step of performing light scanning by driving an actuator based on scanning parameters; a scanning locus acquisition step of acquiring a scanning locus of scanning light emitted from a leading end of an optical fiber; and an adjustment step of adjusting the scanning parameters so that the acquired scanning locus becomes a predetermined reference scanning locus. The adjustment step comprises: a frequency adjustment step of adjusting a frequency of a driving voltage of the actuator so that the amplitude of the scanning locus becomes the maximum; a phase adjustment step of adjusting phase differences of the actuator between an X-axis direction and a Y-axis direction so that the scanning locus becomes almost completely round; and an amplitude adjustment step of adjusting the amplitude of the driving voltage of the actuator in an X-axis direction and a Y-axis direction so that the magnitude and shape of the scanning locus fall within a predetermined range.

Description

  The present invention relates to an automatic calibration method for correcting a scanning trajectory of scanning light emitted from an optical scanning endoscope and a scanning endoscope system for performing the automatic calibration method.

  2. Description of the Related Art Conventionally, a scanning endoscope system is known in which light guided by an optical fiber is scanned in a spiral shape with respect to an observation site, and reflected light from the observation site is received and imaged. In such a scanning endoscope system, a single mode type optical fiber is provided inside the endoscope, and a base end portion thereof is held in a cantilever shape by a biaxial actuator. The biaxial actuator two-dimensionally vibrates (resonates) the tip of the fiber in accordance with the natural frequency while modulating and amplifying the amplitude of vibration, and drives the tip of the optical fiber in a spiral shape. As a result, the illumination light guided from the light source by the optical fiber scans the observation region in a spiral shape, and an image of the irradiation region (scanning region) is acquired based on the return light from the observation region.

  In such a scanning endoscope system, reflected light or fluorescence from a scanning region (observation site) is received at a predetermined cycle timing (hereinafter referred to as “sampling points”), and luminance information at each sampling point is received. Is assigned to the display coordinate system of the monitor (the pixel position of the endoscopic image) to display a two-dimensional endoscopic image. Therefore, in order to generate a highly reproducible endoscope image without distortion, it is necessary to accurately match the scanning position of each sampling point with the display coordinate system of the monitor. Therefore, this type of scanning endoscope system is calibrated so as to obtain an ideal scanning pattern while monitoring an actual scanning pattern (scanning trajectory).

JP 2010-515947 A

  The scanning endoscope system described in Patent Document 1 is a biaxial actuator that only receives illumination light emitted from an optical fiber by a PSD (Position Sensitive Detector) and displays a scanning pattern (scanning trajectory) on a monitor. The adjustment of the amplitude, phase, frequency, and the like of the applied voltage is manually performed while the operator looks at the scanning pattern displayed on the monitor. Calibration of a scanning endoscope system is complicated in procedure, and it is difficult to unify the procedure among workers. As a result, calibration results differ depending on the operator.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an automatic calibration method that gives a uniform calibration result without variation by an operator, and a scanning endoscope that executes the method. Is to provide a system.

  According to one embodiment of the present invention, an optical fiber that guides light emitted from a light source, and an X-axis direction that is two radial directions orthogonal to each other while cantilevering and supporting the tip of the optical fiber Actuators that vibrate in the Y-axis direction, and driving voltages in the X-axis direction and the Y-axis direction of the actuator based on predetermined scanning parameters so that the light emitted from the tip of the optical fiber is scanned in a spiral trajectory A scanning type having an optical scanning device having periodic control of spiral light scanning, and control means for controlling the scanning and scanning locus detection means for detecting the scanning locus of the scanning light emitted from the tip of the optical fiber An automatic calibration method for an endoscope system, wherein a control unit drives an actuator based on a scanning parameter to perform optical scanning, and a control unit scans A scanning trajectory acquisition step for acquiring a scanning trajectory of the scanning light emitted from the tip of the optical fiber from the trace detection means, and an adjustment step for adjusting the scanning parameter so that the acquired scanning trajectory becomes a predetermined reference scanning trajectory. And the adjustment step includes a frequency adjustment step for adjusting the frequency of the drive voltage of the actuator so that the amplitude of the scanning locus is maximized, and an X-axis direction of the actuator so that the scanning locus is a substantially perfect circle. A phase adjustment step for adjusting the phase difference between the driving voltage in the Y-axis direction and the amplitude of the driving voltage in the X-axis and Y-axis directions of the actuator so that the size and shape of the scanning locus are within a predetermined range. And an amplitude adjustment step. An automatic calibration method for a scanning endoscope system is provided.

  According to this configuration, the frequency adjustment process, the phase adjustment process, and the amplitude adjustment process of the driving voltage of the actuator, which are essential for the calibration of the scanning trajectory of the optical scanning device, are automatically executed in a predetermined procedure. Uniform calibration results with no variation due to.

  In the automatic calibration method described above, it is desirable that the phase adjustment step and the amplitude adjustment step be executed after the frequency adjustment step.

  According to this configuration, since the frequency adjustment step that has the greatest influence on the scanning trajectory is performed first, the frequency adjustment causes other adjusted parameters (phase, amplitude) to be out of order, and readjustment is necessary. It is prevented.

  In the automatic calibration method described above, the adjustment step may further include a polar coordinate conversion step for converting the coordinates of the scanning locus into polar coordinates.

  In the above-described automatic calibration method, the frequency adjustment step includes a step of obtaining a frequency at which the amplitude of the scanning locus is maximum in a frequency region including the resonance frequency of the tip of the cantilevered optical fiber, And a step of changing the frequency of the drive voltage to a frequency that maximizes the amplitude of the scanning locus.

  According to this configuration, the frequency of the drive voltage of the actuator can be adjusted to a value close to the resonance frequency of the tip portion of the optical fiber.

  In the above-described automatic calibration method, the step of obtaining the frequency at which the amplitude of the scanning trajectory is maximized is a step of repeatedly obtaining the amplitude of the scanning trajectory while changing the frequency of the drive voltage in the frequency region including the resonance frequency. It is good also as a structure containing.

  In the automatic calibration method described above, the step of acquiring the frequency at which the amplitude of the scanning trajectory is maximized is a stepwise process in which the frequency of the drive voltage is set at a first frequency interval in the first frequency region including the resonance frequency. A first frequency acquisition step that repeatedly acquires the amplitude of the scanning locus while changing, and a frequency of the drive voltage at which the maximum amplitude of the scanning locus is acquired in the first frequency acquisition step is narrower than the first frequency region. A second frequency acquisition step of repeatedly acquiring the amplitude of the scanning trajectory while stepwise changing the frequency of the drive voltage at a second frequency interval narrower than the first frequency interval in the second frequency region. It is good also as a structure.

  According to this configuration, the frequency of the driving voltage can be optimized with high accuracy over a wide frequency range without acquiring a scanning locus by changing the frequency at narrow frequency intervals over the entire wide frequency range. Therefore, the frequency adjustment process is made efficient.

  In the above-described automatic calibration method, the phase adjustment step includes the step of repeatedly acquiring the amplitude of the scanning locus while changing the phase difference between the drive voltage in the X-axis direction and the Y-axis direction of the actuator, and the acquired spiral Extracting a predetermined one-turn amplitude from the scanning trajectory, calculating a dispersion value of the one-turn amplitude, and the phase difference between the drive voltage in the X-axis direction and the Y-axis direction of the actuator. And a step of changing to a value at which the dispersion value of the amplitude for the turn is minimized.

  Further, in the above automatic calibration method, the phase adjustment step and the amplitude adjustment step may be alternately executed until the scanning locus becomes a substantially perfect circle.

  According to this configuration, after the adjustment, the deviation caused by the adjustment of other parameters is readjusted, so that more accurate calibration is possible.

  In the automatic calibration method, the phase adjustment step or the amplitude adjustment step may be executed at least twice.

  In the automatic calibration method, the amplitude adjustment step includes a step of acquiring a scanning locus, an amplitude determining step of determining whether or not the amplitude in at least two directions of the scanning locus satisfies a predetermined amplitude determination condition, A drive amplitude adjustment step of adjusting the amplitude of the drive voltage of the actuator in at least a direction that does not satisfy the amplitude determination condition may be adopted.

  In the above automatic calibration method, the amplitude determination condition includes a first condition that the amplitude in at least two directions is equal to or greater than a predetermined target value, and a first condition that an amplitude difference in at least two directions is equal to or less than a predetermined value. It is good also as a structure containing 2 conditions.

  According to this configuration, not only the size of the scanning trajectory but also the shape is adjusted uniformly.

  In the above automatic calibration method, at least two directions include the X-axis direction and the Y-axis direction, and only when the amplitude of the scanning locus in the X-axis direction or the Y-axis direction does not satisfy the first condition. It is good also as a structure which increases the amplitude of the drive voltage of the actuator in the direction which does not satisfy | fill conditions.

  In the above-described automatic calibration method, the amplitude adjustment step further includes an amplitude comparison step that compares the amplitudes of the scanning trajectories in the X-axis direction and the Y-axis direction to determine the magnitude, and depends on the determination result of the amplitude comparison step. Thus, the amplitude of the drive voltage may be adjusted.

  In the above-described automatic calibration method, only when the amplitude of the scanning locus in the X-axis direction and the Y-axis direction does not satisfy the first condition, the direction of the direction in which the amplitude of the scanning locus is determined to be small in the amplitude comparison step. A configuration may be adopted in which the amplitude of the drive voltage is increased more than the amplitude of the drive voltage in the direction determined to be large.

  In the automatic calibration method described above, the amplitude of the scanning trajectory in the amplitude comparison step only when the amplitudes of the scanning trajectories in the X-axis direction and the Y-axis direction both satisfy the first condition and the second condition is not satisfied. The amplitude of the drive voltage in the direction determined to be large may be reduced.

  In the automatic calibration method, the amplitude determination step may determine the amplitudes in the eight directions at intervals of π / 4.

  The automatic calibration method may further include a pass / fail determination step for determining pass / fail of the scanning locus, and the pass / fail determination step may be executed after the frequency adjustment step, the phase adjustment step, and the amplitude adjustment step.

  In the above-described automatic calibration method, the pass / fail determination step further includes a scan diameter pass / fail determination step for determining pass / fail of the size of the spiral scan trajectory, and the scan diameter pass / fail determination step includes the spiral scan trajectory. Including the step of obtaining the amplitude of one turn on the outermost periphery and the step of determining whether or not all the amplitudes of one turn on the outermost periphery are equal to or greater than a target value. Only when all of the above are equal to or larger than the target value, the size of the spiral scanning trajectory may be determined to be acceptable.

  In the automatic calibration method described above, the frequency adjustment step may be executed again only when it is determined that the scanning diameter acceptance / rejection determination step fails.

  In the above-described automatic calibration method, the pass / fail determination step may further include a roundness pass / fail determination step for determining pass / fail of the roundness of the spiral scanning trajectory.

  In the automatic calibration method described above, the phase adjustment step may be executed again only when it is determined that the roundness determination step fails.

  In the automatic calibration method described above, the scanning endoscope system detects a return light from the subject irradiated with the scanning light and generates a video signal for displaying the subject image on the monitor based on the detection result. Further comprising imaging means for generating and outputting, the adjusting step adjusts the drive stop time for adjusting the time for stopping the actuator so that the period of the spiral scan coincides with the reciprocal of the frame rate of the video signal. It is good also as a structure further including a step.

  In the automatic calibration method described above, the drive stop time adjustment step may be executed after the frequency adjustment step, the phase adjustment step, and the amplitude adjustment step.

  In the automatic calibration method, the drive stop time adjustment step may be executed after the pass / fail determination step.

  According to one embodiment of the present invention, an optical fiber that guides light emitted from a light source, and an X-axis direction that is two radial directions orthogonal to each other while cantilevering and supporting the tip of the optical fiber And driving in the X-axis direction and the Y-axis direction of the actuator based on predetermined scanning parameters so that the light emitted from the tip of the optical fiber is scanned in a spiral locus A scanning device having a control means for controlling the voltage and a scanning locus detection means for detecting a scanning locus of the scanning light emitted from the tip of the optical fiber, and provided with an optical scanning device that periodically performs spiral optical scanning. The endoscope system further includes scanning parameter automatic adjustment means for automatically adjusting scanning parameters in a predetermined procedure so that the acquired scanning locus becomes a predetermined reference scanning locus. The parameter automatic adjustment means includes a frequency adjustment means for adjusting the frequency of the driving voltage of the actuator so that the amplitude of the scanning locus is maximized, and an X-axis direction and a Y-axis of the actuator so that the scanning locus is substantially perfect circle. Phase adjusting means for adjusting the phase difference of the driving voltage in the direction, and amplitude adjusting means for adjusting the amplitude of the driving voltage in the X-axis and Y-axis directions of the actuator so that the size and shape of the scanning locus are within a predetermined range A scanning endoscope system is provided.

  According to the calibration method and the scanning endoscope system according to the embodiment of the present invention, since the complicated adjustment processing of the scanning parameters of the optical scanning device is automatically performed in a uniform procedure, the calibration result by the operator This solves the problem of variation.

It is a block diagram which shows the structure of the scanning confocal endoscope system of embodiment of this invention. It is a figure which shows schematically the structure of the confocal optical unit which the scanning confocal endoscope system of embodiment of this invention has. It is a figure which shows the rotation locus | trajectory of the front-end | tip of an optical fiber on an XY approximate surface. It is a figure which shows the relationship between the displacement amount (amplitude) of the front-end | tip of an optical fiber on an XY approximate surface in the X (or Y) direction, and a sampling period and a braking period. It is a figure explaining the correspondence of a sampling point and a raster coordinate. It is a schematic diagram of the calibration apparatus of embodiment of this invention. It is a flowchart of the calibration program performed with the scanning confocal endoscope system of embodiment of this invention. It is a figure which shows the initial spot formation position on the light-receiving surface of PSD. It is a figure which shows a mode when XY adjustment is performed by the calibration program. It is a figure which shows the relationship between the movement amount when moving the light-receiving surface of PSD to a Z direction, and the output current of PSD. It is a figure which shows the scanning locus | trajectory of excitation light when predetermined alternating voltage X and Y are applied to a biaxial actuator. It is a figure which shows the scanning locus | trajectory of the excitation light adjusted so that it might become an ideal scanning locus | trajectory by calibration. It is a flowchart which shows the procedure of the process which adjusts a scanning parameter. It is a flowchart which shows the procedure of the process which adjusts the frequency of the alternating voltage applied to a biaxial actuator. It is a flowchart which shows the procedure of the process which adjusts the phase of the alternating voltage applied to a biaxial actuator. It is a flowchart which shows the procedure of the process which adjusts the amplitude of the alternating voltage applied to a biaxial actuator. It is a figure explaining eight directions in which an amplitude is evaluated in the pass / fail judgment of the roundness of a scanning locus.

  Hereinafter, a scanning confocal endoscope system according to an embodiment of the present invention will be described with reference to the drawings.

  The scanning confocal endoscope system of the present embodiment is a system designed by applying the principle of a confocal microscope, and is preferably configured to observe a subject with high magnification and high resolution. FIG. 1 is a block diagram showing a configuration of a scanning confocal endoscope system 1 according to an embodiment of the present invention. As shown in FIG. 1, the scanning confocal endoscope system 1 includes a system main body 100, a confocal endoscope 200, a monitor 300, and a calibration device 400. The confocal observation using the scanning confocal endoscope system 1 is performed in a state where the distal end surface of the flexible tubular confocal endoscope 200 is applied to the subject.

  The system body 100 includes a light source 102, an optical demultiplexer / multiplexer (optical coupler) 104, a damper 106, a CPU 108, a CPU memory 110, an optical fiber 112, a light receiver 114, a video signal processing circuit 116, an image memory 118, and a video signal output. A circuit 120 is included. The confocal endoscope 200 includes an optical fiber 202, a confocal optical unit 204, a sub CPU 206, a sub memory 208, and a scanning driver 210. In the following description, one end where the objective optical system 204D is disposed in the longitudinal direction of the confocal endoscope 200 is referred to as a distal end, and the other end connected to the system main body 100 is referred to as a proximal end.

  The light source 102 emits excitation light that excites the medicine administered into the body cavity of the patient in accordance with the drive control of the CPU 108. The excitation light enters the optical demultiplexer / multiplexer 104. An optical connector 152 is coupled to one of the ports of the optical demultiplexer / multiplexer 104. The unnecessary port of the optical demultiplexer-multiplexer 104 is coupled to a damper 106 that terminates the excitation light emitted from the light source 102 without reflection. The excitation light incident on the former port passes through the optical connector 152 and enters the optical system arranged in the confocal endoscope 200.

  One end (hereinafter referred to as “base end”) of the optical fiber 202 is optically coupled to the optical demultiplexing / multiplexing device 104 through the optical connector 152. The other end (hereinafter referred to as “tip”) of the optical fiber 202 is housed in a confocal optical unit 204 incorporated in the tip of the confocal endoscope 200. The excitation light emitted from the optical demultiplexer-multiplexer 104 passes through the optical connector 152, enters the proximal end of the optical fiber 202, transmits through the optical fiber 202, and is emitted from the distal end of the optical fiber 202.

  FIG. 2A is a diagram schematically showing the configuration of the confocal optical unit 204. Hereinafter, for convenience of describing the confocal optical unit 204, the longitudinal direction of the confocal optical unit 204 is defined as the Z direction, and two directions orthogonal to the Z direction and orthogonal to each other are defined as the X direction and the Y direction. As shown in FIG. 2A, the confocal optical unit 204 has a metal outer cylinder 204A that houses various components. The outer cylinder 204A holds an inner cylinder 204B having an outer wall surface shape corresponding to the inner wall surface shape of the outer cylinder 204A so as to be slidable coaxially (Z direction). The distal end of the optical fiber 202 (hereinafter referred to as “202a”) is housed and supported in the inner cylinder 204B through openings formed in the base end surfaces of the outer cylinder 204A and the inner cylinder 204B, and is located within the scanning confocal. It functions as a secondary point light source of the endoscope system 1. The position of the tip 202a, which is a point light source, periodically changes according to control by the CPU. In FIG. 2A, a central axis AX is an optical axis of an objective optical system 204D described later. When the tip 202a of the optical fiber 202 arranged in the Z direction is not vibrating, the central axis AX Coincides with the optical axis (center axis) of the optical fiber 202.

  The sub memory 208 stores probe information such as identification information and various properties of the confocal endoscope 200. The sub CPU 206 reads probe information from the sub memory 208 when the system is activated, and transmits the probe information to the CPU 108 via the electrical connector 154 that electrically connects the system main body 100 and the confocal endoscope 200. The CPU 108 stores the transmitted probe information in the CPU memory 110. The CPU 108 reads the stored probe information when necessary, generates a signal necessary for controlling the confocal endoscope 200, and transmits the signal to the sub CPU 206. The sub CPU 206 designates a setting value necessary for the scan driver 210 in accordance with the control signal transmitted from the CPU 108.

  The scanning driver 210 generates a drive signal corresponding to the designated set value, and drives and controls the biaxial actuator 204C that is bonded and fixed to the outer peripheral surface of the optical fiber 202 near the tip 202a. FIG. 2B is a diagram schematically showing the configuration of the biaxial actuator 204C. As shown in FIG. 2B, the biaxial actuator 204C includes a pair of X-axis electrodes (“X” and “X ′” in the figure) and Y-axis electrodes (in the figure) connected to the scanning driver 210. “Y”, “Y ′”) are piezoelectric actuators formed on a piezoelectric body.

  The scanning driver 210 applies an AC voltage X between the X-axis electrodes of the biaxial actuator 204C to vibrate the piezoelectric body in the X direction, and generates an AC voltage Y having the same frequency as that of the AC voltage X and orthogonal in phase. Applied between the Y-axis electrodes, the piezoelectric body is vibrated in the Y direction. The AC voltages X and Y are respectively defined as voltages that increase linearly in proportion to time and reach effective values (X) and (Y) over time (X) and (Y). The tip 202a of the optical fiber 202 is on a surface that approximates the XY plane (hereinafter referred to as "XY approximate surface") by combining the kinetic energy in the X and Y directions by the biaxial actuator 204C. Rotate to draw a spiral pattern around the central axis AX. The rotation trajectory of the tip 202a increases in proportion to the applied voltage, and draws a circular trajectory having the largest diameter when the AC voltage having the effective values (X) and (Y) is applied. In the present embodiment, the amplitude, phase, and frequency of the AC voltages X and Y are adjusted by calibration described later so that the rotation locus of the tip 202a becomes an ideal scanning locus. . FIG. 3 is a diagram illustrating a rotation locus of the tip 202a on the XY approximate plane adjusted by calibration.

  FIG. 4 is a diagram for explaining the relationship between the amount of displacement (amplitude) in the X (or Y) direction of the tip 202a of the optical fiber 202 on the XY approximate plane and each operation timing of the confocal endoscope 200. The excitation light is continuous light (or pulsed light) and is in the period from immediately after the start of application of AC voltage to the biaxial actuator 204C until the application is stopped (hereinafter, this period is referred to as “sampling period” for convenience of explanation). The light is emitted from the tip 202a of the optical fiber 202. As described above, when an AC voltage is applied to the biaxial actuator 204C, the tip 202a of the optical fiber 202 rotates so as to draw a spiral pattern around the central axis AX. For this reason, during the sampling period, the excitation light emitted from the tip 202a of the optical fiber 202 scans a predetermined circular scanning region around the central axis AX in a spiral shape. When the application of the AC voltage to the biaxial actuator 204C is stopped after the sampling period has elapsed, the vibration of the optical fiber 202 is attenuated. The circular motion of the tip 202a on the approximate XY plane converges as the vibration of the optical fiber 202 is attenuated, and the vibration of the optical fiber 202 becomes substantially zero after a predetermined time (that is, the tip 202a is on the central axis AX). Almost stop). Hereinafter, for convenience of explanation, a period from the end of the sampling period until the tip 202a substantially stops on the central axis AX is referred to as a “braking period”. After the braking period, the next sampling period is started after a predetermined time has elapsed. Hereinafter, for convenience of description, a period from the end of the braking period to the start of the next sampling period is referred to as a “settling period”. The settling period is a standby time for completely stopping the tip 202a of the optical fiber 202 on the central axis AX. By providing the settling time, the tip 202a can be scanned accurately. The period corresponding to one frame (scanning period) is composed of one sampling period, one braking period, and one settling period. By adjusting the settling period, the period of the scanning period is set to the frame rate. It can be adjusted to match F (fps: frames per second). That is, the settling period can be appropriately set from the relationship between the time until the tip 202a of the optical fiber 202 completely stops and the frame rate F. In order to shorten the braking period, a braking torque may be positively applied by applying a reverse phase voltage to the biaxial actuator 204C in the initial stage of the braking period.

  An objective optical system 204D is installed in front of the tip 202a of the optical fiber 202. The objective optical system 204D is composed of a plurality of optical lenses, and is held by the outer cylinder 204A via a lens frame (not shown). The lens frame is fixed and supported relative to the inner cylinder 204B inside the outer cylinder 204A. Therefore, the optical lens group held by the lens frame slides in the Z direction integrally with the inner cylinder 204B inside the outer cylinder 204A. A cover glass (not shown) is held at the forefront of the outer cylinder 204A (that is, in front of the objective optical system 204D).

  A compression coil spring 204E and a shape memory alloy 204F are attached between the base end surface of the inner cylinder 204B and the inner wall surface of the outer cylinder 204A. The compression coil spring 204E is initially compressed and sandwiched in the Z direction from the natural length. The shape memory alloy 204F has a long bar shape in the Z direction, deforms when an external force is applied at room temperature, and has a property of restoring to a predetermined shape by a shape memory effect when heated to a certain temperature or higher. ing. The shape memory alloy 204F is designed such that the restoring force due to the shape memory effect is larger than the restoring force of the compression coil spring 204E. The scan driver 210 generates a drive signal corresponding to the set value designated by the sub CPU 206, and energizes and heats the shape memory alloy 204F to control the expansion / contraction amount. The shape memory alloy 204F advances and retracts the inner tube 204B in the Z direction together with the optical fiber 202 according to the amount of expansion and contraction.

  The excitation light emitted from the tip 202a of the optical fiber 202 passes through the objective optical system 204D and forms a spot on the surface or surface layer of the subject. The spot forming position is displaced in the Z direction in accordance with the advance / retreat of the tip 202a which is a point light source. That is, the confocal optical unit 204 scans the subject three-dimensionally by combining the periodic circular motion of the tip 202a on the XY approximate plane by the biaxial actuator 204C and the advance and retreat in the Z direction.

  Since the tip 202a of the optical fiber 202 is disposed at the front focal position of the objective optical system 204D, it functions as a confocal pinhole. Of the scattering component (fluorescence) of the subject excited by the excitation light, only the fluorescence from the condensing point optically conjugate with the tip 202a is incident on the tip 202a. The fluorescence is transmitted through the optical fiber 202, passes through the optical connector 152, and enters the optical demultiplexer / multiplexer 104. The optical demultiplexer / multiplexer 104 separates the incident fluorescence from the excitation light emitted from the light source 102 and guides it to the optical fiber 112. The fluorescence is transmitted through the optical fiber 112 and detected by the light receiver 114. The light receiver 114 may be a high-sensitivity photodetector such as a photomultiplier tube in order to detect weak light with low noise.

  The detection signal detected by the light receiver 114 is input to the video signal processing circuit 116. The video signal processing circuit 116 operates under the control of the CPU 108 to obtain a digital detection signal by sample-holding and AD converting the detection signal at a constant rate. Here, when the position (trajectory) of the tip 202a of the optical fiber 202 during the sampling period is determined, the spot formation position in the observation region (scanning region) corresponding to the position, the return light (fluorescence) from the spot formation position. The signal acquisition timing (that is, the sampling point) for obtaining the digital detection signal by detecting the signal is almost uniquely determined. As will be described later, in the present embodiment, the scanning locus of the tip 202a is measured in advance using the calibration device 400. Then, the amplitude, phase, frequency, etc. of the voltage applied to the biaxial actuator 204C are adjusted so that the measured scanning locus becomes an ideal scanning pattern (that is, an ideal spiral scanning pattern) The position on the image corresponding to the sampling point (the pixel position of the endoscopic image displayed on the monitor 300) is determined. The correspondence between the sampling point and the pixel position (pixel address) of the endoscopic image is stored in the CPU memory 110 as a remap table. For example, when the endoscopic image is composed of 15 pixels in the horizontal direction (X direction) and 15 pixels in the vertical direction (Y direction), the position of the excitation light (sampling point) and the pixels of the endoscopic image that are sequentially sampled The relationship with the position (raster coordinates) is as shown in FIG. 5, and the CPU 108 obtains the pixel position (raster coordinates) of the endoscopic image corresponding to each sampling point based on this relationship and creates a remap table. . FIG. 5 shows sampling points in the central portion and peripheral portion of the scanning region in consideration of the visibility of the drawing, but in actuality, a large number of sampling points are taken along the spiral scanning locus. There is a point.

  The video signal processing circuit 116 refers to the remapping table and assigns each digital detection signal obtained at each sampling point as corresponding pixel address data. Hereinafter, for convenience of explanation, the above assignment work is referred to as remapping. The video signal processing circuit 116 buffers an image signal constituted by a spatial arrangement of each point image in the image memory 118 according to the remapping result in a frame unit. The buffered signal is swept from the image memory 118 to the video signal output circuit 120 at a predetermined timing, and the video signal conforms to a predetermined standard such as NTSC (National Television System Committee) or PAL (Phase Alternating Line). To be output to the monitor 300. On the display screen of the monitor 300, a high-magnification and high-resolution three-dimensional confocal image of the subject (in this specification, simply referred to as “endoscopic image”) is displayed.

  As described above, since the image of the subject is constructed by the remapping operation, in order to obtain an endoscope image without distortion, it is necessary to rotate the tip 202a so as to have an ideal spiral scanning pattern. is there. However, since the characteristics of each component constituting the scanning confocal endoscope system 1 usually vary within a predetermined range, each product has a characteristic specific to each product (hereinafter referred to as “product specific characteristic”). The simple scanning trajectory as shown in FIG. 3 cannot be obtained simply by assembling. Therefore, in the scanning confocal endoscope system 1 of the present embodiment, calibration described later is performed in order to cancel such product-specific characteristics.

  FIG. 6 is a schematic diagram of a calibration apparatus 400 used during calibration according to the present embodiment. In the calibration, the rotation locus of the tip 202a of the optical fiber 202 is detected, and this rotation locus becomes an ideal rotation locus (that is, the scanning locus of the excitation light emitted from the confocal optical unit 204 is the reference). The amplitude, phase, and frequency of the AC voltages X and Y applied to the biaxial actuator 204C are adjusted to create a new remapping table (so that a scanning trajectory is obtained). Hereinafter, in this specification, parameters adjusted by calibration, mainly the amplitude, phase, and frequency of the AC voltages X and Y, are collectively referred to as “adjustment parameters”. The calibration apparatus 400 will be described as a configuration independent of the system main body 100, but may be a part of the configuration incorporated in the system main body 100.

  As shown in FIG. 6, the calibration apparatus 400 includes a unit support 420, a case 402, an XYZ stage 408, a stage drive motor 410, a calibration circuit 412, and the like.

  The unit support 420 is a substantially cylindrical member fixed to the main body (not shown) of the calibration device 400, and the inner diameter thereof is configured to be slightly larger than the outer diameter of the confocal optical unit 204. . At the time of calibration, the focus optical unit 204 is inserted into the unit support 420 and positioned and fixed in each of the X, Y, and Z directions.

  A PSD 404, a PSD substrate 405, and a relay lens unit 406 are attached to the case 402. The PSD 404 is mounted on the PSD substrate 405 and is disposed on the base end surface side of the case 402 so that the light receiving surface is positioned on the XY plane (in other words, orthogonal to the Z direction). The PSD 404 receives the excitation light emitted from the confocal optical unit 204 and detects its position (that is, the position of the excitation light on the light receiving surface) (details will be described later). The relay lens unit 406 is disposed on the distal end side (confocal optical unit 204 side) of the case 402 so that the optical axis is in the Z direction. The relay lens unit 406 is a so-called magnifying optical system having a plurality of lenses inside, and is arranged so that the optical axis and the rear focal point F2 are positioned at the center of the light receiving surface of the PSD 404. Further, the front focal point F1 of the relay lens unit 406 is adjusted so as to substantially coincide with the focal point of the objective optical system 204D of the confocal optical unit 204 (that is, the condensing position of the excitation light) by calibration described later. That is, the relay lens unit 406 functions to enlarge the projection image (that is, the excitation light scanning region (maximum shake width)) at the condensing position of the excitation light emitted from the confocal optical unit 204. Note that the inside of the case 402 is shielded so that external light does not enter, and the PSD 404 detects the excitation light from the confocal optical unit 204 with a high SN ratio. The detection current of the PSD 404 is output to the calibration circuit 412 via the PSD substrate 405.

  The case 402 is fixed on an XYZ stage 408 that can move in the X, Y, and Z directions by a stage drive motor 410. The stage drive motor 410 is, for example, a stepping motor, and receives a signal from the calibration circuit 412 during calibration described later, and moves the XYZ stage 408 in a predetermined direction. In the present embodiment, the moving resolution of the XYZ stage 408 (that is, the moving amount of the XYZ stage 408 with respect to one step of the stage drive motor 410) is set to about 10 μm.

  The calibration circuit 412 is a circuit capable of bidirectional communication with the CPU 108. The calibration circuit 412 moves the XYZ stage 408 via the stage drive motor 410 under the control of the CPU 108 during calibration. Further, the calibration circuit 412 converts the detected current of the PSD 404 output from the PSD substrate 405 into a voltage and outputs it to the CPU 108 as a detected voltage.

  FIG. 7 is a flowchart of a calibration program executed during calibration. The calibration program is executed by the CPU 108 when the user (surgeon) inserts the focus optical unit 204 into the unit support 420 and inputs a predetermined instruction from a user interface (not shown) of the system main body 100. It is a subroutine. For convenience of explanation, each processing step of calibration is abbreviated as “S” in the explanation and drawings in this specification.

  As shown in FIG. 7, when the calibration program is started, the CPU 108 executes S1. In S <b> 1, the position of the case 402 is adjusted with respect to the focus optical unit 204. In this process, the CPU 108 controls the light source 102 so that the excitation light is continuously emitted, and controls the operation driver 210 so as to stop the voltage application to the biaxial actuator 204C. As a result, the excitation light emitted from the optical fiber 202 travels along the central axis AX, passes through the relay lens unit 406, and forms an image on the light receiving surface of the PSD 404 (FIG. 6). In the present specification, the initial spot formation position of the excitation light when no voltage is applied to the biaxial actuator 204C is hereinafter referred to as “initial spot formation position”.

  FIG. 8 is a diagram showing the initial spot formation position P on the light receiving surface of the PSD 404. As described above, since the scanning confocal endoscope system 1 has product-specific characteristics, the initial spot formation position does not necessarily coincide with the center of the PSD 404 and is detected by being shifted in the X and Y directions. Further, since the focal point of the objective optical system 204D of the confocal optical unit 204 also varies somewhat depending on the parts, the front focal point F1 of the relay lens unit 406 and the focal point of the objective optical system 204D of the confocal optical unit 204 (that is, excitation light). Does not necessarily match. Therefore, in S1, the case 402 is moved in the X and Y directions (XY adjustment) so that the initial spot formation position substantially coincides with the center of the light receiving surface of the PSD 404, and the front focal point F1 of the relay lens unit 406 is set. The case 402 is moved in each direction of Z so that the focal point of the objective optical system 204D of the confocal optical unit 204 is substantially coincident (Z adjustment).

ここで、Ｉ_Ｘ１は、電極Ｘ１から出力される電流であり、Ｉ_Ｘ２は、電極Ｘ２から出力される電流であり、Ｉ_Ｙ１は、電極Ｙ１から出力される電流であり、Ｉ_Ｙ２は、電極Ｙ２から出力される電流である。また、Ｌは、ＰＳＤ４０４の受光面の中心から各電極までの距離である。 (XY adjustment)
The PSD 404 includes a pair of X-direction electrodes X1 and X2 and a pair of Y-direction electrodes Y1 and Y2. The spot formation position on the light receiving surface of the PSD 404 detects a current output from each electrode. Sought by. Specifically, the positions Xp and Yp on the light receiving surface of the PSD 404 at the initial spot formation position P are obtained by the following formulas (Formula 1 and Formula 2).

Here, I _X1 is a current output from the electrode X1, I _X2 is a current output from the electrode X2, I _Y1 is a current output from the electrode Y1, and I _Y2 is an electrode This is the current output from Y2. L is a distance from the center of the light receiving surface of the PSD 404 to each electrode.

In S1, the CPU 108 determines the current I _X1 output from the electrode _X1 , the current I _X2 output from the electrode _X2 , the current I _Y1 output from the electrode Y1, and the electrode from the detection voltage of the PSD 404 input from the calibration circuit 412. The currents I _Y2 output from _Y2 are respectively obtained, and the positions Xp and Yp on the light receiving surface of the PSD 404 at the initial spot formation position P are obtained based on the above formulas 1 and 2. Then, the CPU 108 drives the stage drive motor 410 so that Xp and Yp are minimized (that is, the initial spot formation position substantially coincides with the center of the light receiving surface of the PSD 404), and moves the XYZ stage 408 in the X direction. And move in the Y direction. However, as described above, the XYZ stage 408 of this embodiment has a moving resolution, and actually there is a backlash of the stage drive motor 410, and these error factors are magnified by the relay lens unit 406. For this reason, it is difficult to accurately match the spot of the excitation light with the center of the light receiving surface of the PSD 404. Therefore, in the present embodiment, a PSD 404 having a light receiving surface (10 mm × 10 mm) sufficiently larger than the scanning region (diameter 5 mm) of excitation light on the PSD 404 is used.

  FIG. 9 is a diagram illustrating a state when the XY adjustment is performed in S1. For convenience of explanation, FIG. 9 shows a state where the initial spot formation position P has moved to the center O of the light receiving surface of the PSD 404. When the initial spot formation position P moves to the center O of the light receiving surface of the PSD 404, the excitation light scanning region T becomes a region having a diameter of 5 mm centered on the center O of the light receiving surface. The light receiving surface of the PSD 404 is sufficiently larger than the scanning area T of the excitation light, and the shaded area surrounding the scanning area T (area corresponding to a width of about 2.5 mm) is adjusted during adjustment in the XY direction. It is designed to function as a proxy α. In other words, even if backlash or the like of the stage drive motor 410 occurs, the scanning region T is configured to be always within the light receiving surface of the PSD 404.

(Z adjustment)
FIG. 10 shows the relationship between the movement amount z when the light-receiving surface of the PSD 404 is moved in the Z direction, the total current in the X direction (I _X1 + I _X2 ), and the total current in the Y direction (I _Y1 + I _Y2 ). It is a graph which shows. Here, Z = 0 is a position when the front focal point F1 of the relay lens unit 406 coincides with the focal point of the objective optical system 204D of the confocal optical unit 204. As shown in FIG. 9, when the front focal point F1 of the relay lens unit 406 coincides with the focal point of the objective optical system 204D of the confocal optical unit 204, the excitation light is most focused on the light receiving surface of the PSD 404, and the current in the X direction is reduced. The sum (I _X1 + I _X2 ) and the sum of currents in the Y direction (I _Y1 + I _Y2 ) take extreme values. Therefore, in S1, Z adjustment is performed by using the sum of currents in the X direction (I _X1 + I _X2 ) and the sum of currents in the Y direction (I _Y1 + I _Y2 ) as an index representing the beam diameter of the excitation light. Specifically, the CPU 108 determines the current I _X1 output from the electrode _X1 , the current I _X2 output from the electrode _X2 , and the current I _Y1 output from the electrode Y1 from the detection voltage of the PSD 404 output from the calibration circuit 412. The current I _Y2 output from the electrode Y2 is obtained, respectively, and the sum of currents in the X direction (I _X1 + I _X2 ) and the sum of currents in the Y direction (I _Y1 + I _Y2 ) are obtained. Then, the CPU 108 takes the extreme values of the sum of currents in the X direction (I _X1 + I _X2 ) and the sum of currents in the Y direction (I _Y1 + I _Y2 ) (that is, with the front focal point F1 of the relay lens unit 406). The stage drive motor 410 is driven to move the XYZ stage 408 along the Z direction (so that the focal point of the objective optical system 204D of the confocal optical unit 204 substantially matches).

  As described above, in S1, XY adjustment for moving the case 402 in the X and Y directions and Z adjustment for moving the case 402 in the Z directions are performed, and the initial spot formation position is the center of the light receiving surface of the PSD 404. And the front focal point F1 of the relay lens unit 406 and the focal point of the objective optical system 204D of the confocal optical unit 204 are adjusted to substantially coincide. In the above, for convenience of explanation, the description has been made in the order of XY adjustment and Z adjustment, but it is also possible to perform the adjustment in the order of Z adjustment and XY adjustment. If the Z adjustment is performed before the XY adjustment, the XY adjustment can be performed in a state where the excitation light spot is narrowed. Therefore, the aberration of the objective optical system 204D and the relay lens unit 406, the inclination of the objective optical system 204D, The XY adjustment can be performed with high accuracy without being affected by the mounting error of the focus optical unit 204. Next, the process proceeds to S2 (FIG. 7).

  In S <b> 2, the CPU 108 applies uniform (ie, default) AC voltages X and Y to the biaxial actuator 204 </ b> C to rotate the tip 202 a of the optical fiber 202, and spirals the light receiving surface of the PSD 404. A scanning locus of the excitation light to be scanned is detected. FIG. 11 is a diagram showing a scanning trajectory of excitation light when the default AC voltages X and Y are applied to the biaxial actuator 204C. As described above, since the scanning confocal endoscope system 1 has product-specific characteristics, an ideal scanning locus as shown in FIG. 3 is not obtained in a state where the default AC voltages X and Y are applied. For example, the scanning locus is distorted in an elliptical shape. Next, the process proceeds to S3.

  In S3, the CPU 108 evaluates the scanning trajectory of the excitation light detected in S2, and determines whether or not the scanning trajectory is within a specified tolerance (that is, whether or not it is an allowable scanning trajectory). The specified tolerance is determined in advance from the allowable distortion amount of the image, and the CPU 108 determines the size, shape (roundness), scanning speed, etc. of the scanning area from the scanning trajectory of the excitation light detected in S2. To evaluate. In S3, when it is determined that it is within the tolerance (S3: YES), the process proceeds to S5, and when it is determined that it is not within the tolerance (S3: NO), the process proceeds to S4.

  In S4, the CPU 108 changes adjustment parameters (scanning parameters) of the AC voltages X and Y applied to the biaxial actuator 204C. Specifically, the CPU 108 determines the frequencies of the AC voltages X and Y based on the evaluation result of the scanning trajectory of the excitation light in S3 (specifically, the cantilever-supported light). The driving efficiency of the confocal optical unit 204 is increased by adjusting the frequency so as to match the resonance frequency of the tip of the fiber. If there is a problem with the size of the scanning locus, the frequency of the AC voltages X and Y is adjusted to enlarge or reduce the scanning locus. If there is a problem with the shape of the scanning locus, the shape of the scanning locus is changed by adjusting the phases of the AC voltages X and Y. The CPU 108 repeatedly executes the processing from S2 to S4 until it is determined in S3 that it is within the tolerance. As a result, the scanning trajectory of the excitation light detected in S2 is adjusted to be an ideal scanning trajectory as shown in FIG. Details of the process S4 for adjusting the scanning parameter will be described later.

  In S5, the CPU 108 obtains the correspondence between each sampling point and the pixel position (pixel address) of the endoscope image for the scanning trajectory adjusted in S4, and creates a new remapping table. Then, the created remapping table is stored in the CPU memory 110 together with the adjustment parameters adjusted in S4 (that is, the amplitude, phase, and frequency of the AC voltages X and Y), and the calibration program is terminated. In S5, the remap table and the adjustment parameter stored in the CPU memory 110 are repeatedly used until new calibration is performed.

  Next, details of the process S4 for adjusting the scanning parameter will be described. FIG. 13 is a flowchart showing an outline of the procedure of the process S4. The process S4 for adjusting the scanning parameter is a process S10 for adjusting the frequency f of the AC voltages X and Y (that is, the drive frequency f of the biaxial actuator 204C), and a process S30 for adjusting the phase difference between the AC voltage X and the AC voltage Y. In addition, a process S50 for adjusting the amplitudes of the AC voltage X and the AC voltage Y, a pass / fail determination process S80, and a process S90 for adjusting the settling period are included. After the shape and size of the scanning trajectory of the excitation light is adjusted by S10, S30, and S50, it is determined whether or not the scanning trajectory is properly adjusted by S80, and after passing the determination of S80, S90 is performed. Is called. Details of each process of S4 will be described below.

  First, the process S10 for adjusting the frequencies of the AC voltages X and Y will be described. As described above, in the confocal optical unit 204 of the present embodiment, the frequencies of the AC voltages X and Y are set to the resonance frequency band at the tip of the optical fiber. Thereby, the vibration of the biaxial actuator 204C can be efficiently transmitted to the tip of the optical fiber. When the frequency of the AC voltages X and Y deviates from the resonance frequency band of the optical fiber tip, the tip of the optical fiber is hardly driven. As a result, the excitation light is not scanned with sufficient amplitude, and calibration is performed. I can't. Therefore, in the process S4 for adjusting the scanning parameter, S10 is performed first, and the necessary size of the scanning locus is ensured.

  In S10, a process for detecting the resonance frequency of the tip of the optical fiber and changing the set value of the drive frequency f of the biaxial actuator 204C to the detected resonance frequency is performed. In the detection of the resonance frequency, the size of the scanning locus is evaluated while changing the driving frequency f of the biaxial actuator 204C, the frequency at which the size of the scanning locus is maximized is regarded as the resonance frequency, and this value is regarded as the driving frequency f. Set to. Since the bandwidth of the resonance frequency is as narrow as several Hz, it is necessary to evaluate the size of the scanning locus while changing the frequency at 1 Hz intervals. Further, since the resonance frequency of the confocal optical unit 204 has a large individual difference and has a variation of about 1 kHz, it is necessary to evaluate the size of the scanning locus by changing the frequency over the range of 1 kHz. However, it takes an enormous amount of time to evaluate the size of the scanning trajectory at 1 Hz intervals over a frequency range of several kHz. Therefore, in the present embodiment, the resonance frequency can be efficiently detected by performing the detection of the resonance frequency in three stages by changing the frequency range and interval.

  FIG. 14 is a flowchart showing the procedure of the process S10. In S10, the buffer (memory) is first initialized, and the counter k is set to 1 (S11). The counter k is a parameter indicating the stage of processing for detecting the resonance frequency. In the first embodiment, in the first stage, the size of the scanning locus is evaluated at 50 Hz intervals in the frequency range of 1 kHz. In the second stage, the size of the scanning trajectory is evaluated at 10 Hz intervals in a frequency range of 200 Hz including the frequency at which the size of the scanning trajectory is maximized in the first stage. In the final third stage, the size of the scanning trajectory is evaluated at 1 Hz intervals in a frequency range of 20 Hz including the frequency at which the scanning trajectory has the maximum magnitude in the second stage.

Next, the driving frequency f is set to the initial value f ₀ (k) of the frequency range in the k-th stage (S12), the biaxial actuator 204C is driven, and the scanning trajectory for one cycle of the excitation light using the PSD 404. Is acquired (S13). As described above, the position information of the excitation light obtained from the detection current of the PSD 404 is an orthogonal coordinate system (XY coordinate system) with the initial spot formation position (spot position of the excitation light when the confocal optical unit 204 is stopped) as the origin. Coordinate values Xp and Yp. In the present embodiment, since the excitation light is scanned so as to draw a spiral trajectory, the orthogonal coordinate values Xp and Yp are converted into polar coordinate values r and θ suitable for processing the spiral trajectory (S14). Then, the maximum value r _max of the polar coordinate value r is extracted (S15) and compared with the value r _rec recorded in the buffer (the maximum value of the polar coordinate value r so far) (S16). If r _max is larger than r _rec (S16: YES), r _max and drive frequency f are overwritten and stored in the buffer (S17), and the process proceeds to S18. If r _max is equal to or less than r _rec , the process proceeds to S18 without rewriting the buffer.

  In S18, a predetermined value Δf (k) is added to the drive frequency f of the biaxial actuator 204C. Δf (k) is a frequency interval for evaluating the size of the scanning trajectory. As described above, in the present embodiment, the first stage (k = 1) is Δf (1) = 50 Hz, the second stage (k = 2) is Δf (2) = 10 Hz, and the third stage (k = 3). Is set to Δf (3) = 1 Hz.

Next, it is determined whether or not the drive frequency f has reached a predetermined adjustment range (S19). If the drive frequency f is within the adjustment range (S19: NO), the process returns to S13, and the scanning locus for one cycle of the excitation light is acquired again. If the drive frequency f has reached the outside of the adjustment range (S19: YES), the counter k is incremented (S20), and whether or not the value of the counter k after the increment exceeds n (the upper limit value of the counter k). It is determined (S21). If the value of the counter k is less than or equal to n (S21: NO), the process returns to S12, and the drive frequency f is set to the initial value f ₀ (k) in the frequency range corresponding to the counter k after increment. The initial value f ₀ (k) (where k ≠ 1) is a value (for example, f _rec −2 × Δf (k)) slightly smaller than the frequency f _rec at which the amplitude is maximized in the previous stage search. ). In S21, if the value of the counter k exceeds n (S21: YES), the frequency f _rec stored in the buffer is read and the value of the drive frequency f is changed to f _rec (S22). . And S10 is complete | finished and a process transfers to S30.

In S30, the phase difference φ between the AC voltage X and the AC voltage Y is adjusted so that the scanning trajectory of the excitation light becomes a substantially perfect circle. Specifically, the biaxial actuator 204C is driven while changing the phase difference φ of the AC voltage Y with respect to the AC voltage X, and the phase difference φ _opt where the scanning locus of the excitation light comes closest to a perfect circle is detected. Then, φ _opt is set as the value of the phase difference φ.

FIG. 15 is a flowchart showing the procedure of S30. In S30, first, a phase difference phi is set to a predetermined initial value φ ₀ (S31). In this embodiment, the roundness of the scanning trajectory is evaluated while changing the phase difference φ by a predetermined value Δφ (for example, π / 32) within a predetermined adjustment range (for example, a range from π / 4 to 3 / 4π). To search for the phase difference φ at which the scanning locus of the excitation light becomes a substantially perfect circle. That is, π / 4 is set as the initial value φ ₀ of the phase difference.

Next, the biaxial actuator 204C is driven, and the scanning trajectory for one cycle of the excitation light is acquired using the PSD 404 (S32). Next, the scanning trajectory given by the orthogonal coordinate values Xp and Yp is converted into polar coordinate values r and θ (S33). Then, the maximum value r _max of the amplitude r is searched (S34), and a scanning trajectory for one turn centering on θ _max giving r _max is extracted (S35). Next, the variance value of the amplitude r of the scanning trajectory for one turn extracted in S35 is calculated (S36). Since the variance value of the amplitude r becomes smaller as the shape of the scanning locus is closer to a perfect circle, the variance value of the amplitude r is used here as an index of the roundness of the scanning locus. Next, the value V _rec stored in the buffer is read, and it is determined whether or not the variance value V of the amplitude r calculated in S36 is smaller than V _rec (S37). If V is smaller than V _rec (S37: YES), the dispersion value V and the phase difference φ are overwritten and stored in the buffer (S38), and the process proceeds to S39. If V is equal to or higher than V _rec , the process proceeds to S39 without rewriting the buffer.

Next, a predetermined value Δφ is added to the phase difference φ of the AC voltage Y with respect to the AC voltage X (S39), and it is determined whether or not the phase difference φ after addition has reached the outside of the adjustment range (S40). If the phase difference φ is within the adjustment range (S40: NO), the process returns to S32, and the scanning locus for one cycle of the excitation light is acquired again. If the phase difference φ has reached the outside of the adjustment range (S40: YES), the phase difference φ _rec stored in the buffer is read and the value of the phase difference φ is changed to φ _rec (S41). And S10 is complete | finished and a process transfers to S50.

  In S50, the amplitudes of the AC voltage X and the AC voltage Y are adjusted so that the size and shape of the scanning locus of the excitation light are within a predetermined range. FIG. 16 is a flowchart showing the procedure of S50. In S50, it is first determined whether or not the values of the AC voltages X and Y are within the adjustment range (S51). If either of the AC voltages X and Y is out of the adjustment range (S51: NG), the AC voltages X and Y are changed to values stored in the buffer (S52), and S50 ends. In addition, when the data of AC voltage X and Y are not preserve | saved at the buffer, the present setting value is hold | maintained as it is.

If the values of the AC voltages X and Y are within the adjustment range (S51: OK), the biaxial actuator 204C is driven, and the scanning trajectory for one cycle of the excitation light is acquired using the PSD 404 (S53). Next, the scanning trajectory given by the orthogonal coordinate values Xp and Yp is converted into polar coordinate values r and θ (S54). Next, the amplitude r of the scanning trajectory in eight directions (θ = 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, 7π / 4) shown in FIG. 17 is extracted. (S55). Next, a pass / fail determination is performed on the extracted amplitudes in the eight directions (S56). In S56, it is determined whether or not the following two conditions are satisfied.
_-First condition: the amplitude in the eight directions is greater than or equal to the target value r _target- Second condition: the amplitude difference in the eight directions is less than or equal to a predetermined value Judged as passing if both the first and second conditions are satisfied (S56: OK), and the process S50 for adjusting the amplitudes of the AC voltages X and Y ends. Moreover, when either one of 1st and 2nd conditions is not satisfy | filled, it determines with disqualifying (S56: NG) and a process progresses to S57.

In S57, the sign of the difference Δr between the amplitude _{r Y} in the amplitude _{r X} and Y-axis direction (θ = π / 2) in the X-axis direction of the scanning locus _{(θ = 0) (= r} X -r Y) is positive It is determined whether there is, that is, whether the amplitude in the X-axis direction is larger than the Y-axis direction. If Δr is positive (that is, r _X > r _Y ), the process proceeds to S58, and if Δr is 0 or negative (that is, r _X ≦ r _Y ), the process proceeds to S65.

In S58, it is determined whether or not the absolute value of the difference Δr in amplitude between the X-axis direction and the Y-axis direction of the scanning locus is smaller than the absolute value of the value Δr _rec recorded in the buffer. If | Δr | is smaller than | Δr _rec | (S58: YES), the AC voltage X and Δr are overwritten and stored in the buffer (S59), and the process proceeds to S60. If | Δr | is greater than | Δr _rec | (S58: NO), the process proceeds to S60 without rewriting the buffer.

In S60, whether the amplitude _{r X} is above the target value _{r target} is determined in the X-axis direction of the scanning locus. If the amplitude _{r X} is long exceeds the target value _{r target} (S60: YES), the process proceeds to S61. If the amplitude _{r X} is less than the target value _{r target} (S60: NO), the AC voltage X, adjustment processing S64 in Y is performed. In this case, the amplitude r _X and Y-axis direction amplitude r _Y in the X-axis direction scanning locus are both equal to or less than the target value r _target, both of the AC voltage X and Y is increased. Specifically, the AC voltage X is increased by one unit of a predetermined unit voltage adjustment amount ΔX, and the AC voltage Y is increased by two units of the predetermined unit voltage adjustment amount ΔY. Since the amplitude of the scanning locus is smaller in the Y-axis direction than in the X-axis direction, the adjustment amount of the AC voltage Y is set larger than the adjustment amount of the AC voltage X.

In S61, it is determined whether or not the amplitude _rY in the Y-axis direction of the scanning locus exceeds the target value _rtarget . If the amplitude r _Y exceeds the target value r _target (S61: YES), the AC voltage X, Y adjustment processing S62 is performed. If the amplitude r _X is equal to or _smaller than the target value r _target (S61: NO), The adjustment processing S63 of the AC voltages X and Y is performed.

In S62, it is highly likely that the second condition is not satisfied in S56 to the amplitude r _X is too large, the only AC voltage X, is adjusted to reduce by one unit the unit voltage adjustment amount ΔX is performed.

In S63, since only the amplitude _rY is lower than the target value _rtarget , only the AC voltage Y is adjusted to increase by one unit of the unit voltage adjustment amount ΔY.

Next, a process when it is determined that the amplitude in the Y-axis direction is larger than the amplitude in the X-axis direction of the scanning locus (S57: NO) will be described. In S65, as in S58, it is determined whether or not the absolute value of the difference Δr in amplitude between the X-axis direction and the Y-axis direction of the scanning locus is smaller than the absolute value of the value Δr _rec recorded in the buffer. If | Δr | is smaller than | Δr _rec | (S65: YES), the AC voltages Y and Δr are overwritten and stored in the buffer (S66), and the process proceeds to S67. If | Δr | is greater than | Δr _rec | (S65: NO), the process proceeds to S67 without rewriting the buffer.

In S67, it is determined whether or not the amplitude _rY in the Y-axis direction of the scanning locus exceeds the target value _rtarget . If the amplitude r _Y exceeds the target value r _target (S67: YES), the process proceeds to S68, and if the amplitude r _X is equal to or less than the target value r _target (S67: NO), the AC voltages X and Y are adjusted. Process S71 is performed.

In S71, the amplitude _{r X} and Y-axis direction amplitude _{r Y} in the X-axis direction scanning locus are both equal to or less than the target value _{r target,} both of the AC voltage X and Y is increased. Specifically, the AC voltage X is increased by 2 units of the unit voltage adjustment amount ΔX, and the AC voltage Y is increased by 1 unit of the unit voltage adjustment amount ΔY. Since the amplitude of the scanning locus is smaller in the X axis direction than in the Y axis direction, the adjustment amount of the AC voltage X is set larger than the adjustment amount of the AC voltage Y.

In S68, whether the amplitude _{r X} is above the target value _{r target} is determined in the X-axis direction of the scanning locus. If the amplitude _{r X} is greater than the target value _{r target} (S68: YES), the AC voltage X, adjustment processing of Y S69 is performed, and if the amplitude _{r X} is less than the target value _{r target} (S68: NO), The adjustment processing S70 for the AC voltages X and Y is performed.

In S69, since the amplitude _rY is too large, there is a high possibility that the second condition was not satisfied in S56. Therefore, only the AC voltage Y is adjusted to decrease by one unit of the unit voltage adjustment amount ΔY.

S70, since only the amplitude _{r X} is below the target value _{r target,} only for the AC voltage X, an adjustment to increase by one unit of unit voltage adjustment amount ΔX is performed.

  When the adjustment processes S62 to S64 and S69 to S71 for the AC voltages X and Y are completed, the process returns to S51.

  As shown in FIG. 13, a pass / fail determination process S80 is performed after S50. In the pass / fail determination process S80, the biaxial actuator 204C is first driven, and a scanning trajectory for one cycle of the excitation light is acquired using the PSD 404 (S81), and the scanning trajectory given by the orthogonal coordinate values Xp and Yp is a polar coordinate value. Conversion into r and θ is performed (S82).

Next, a scan diameter pass / fail determination S83 is performed. In S83, data for one turn on the outermost periphery of the spiral scanning locus is extracted, and it is determined whether or not the amplitude exceeds the target value r _target at all points on the outermost periphery. If the amplitude is greater than the target value r _target at all points on the outermost periphery, it is determined to be acceptable (S83: OK), and the process proceeds to roundness determination S84. If the amplitude is equal to or less than the target value r _target even at any one point on the outermost periphery, it is determined as rejected (S83: NG). In this case, since the frequency adjustment failure may have caused the failure, the process returns to the frequency adjustment process S10.

  In roundness determination S84, a variance value is calculated for the amplitude of one turn on the outermost circumference of the scanning locus, and it is determined whether or not it is equal to or less than a predetermined upper limit value. On the other hand, if the variance value of the amplitude of the scanning trajectory is equal to or less than the upper limit value, it is determined as acceptable (S84: OK), and the process proceeds to the settling period adjustment process S90. If the variance value of the amplitude of the scanning trajectory exceeds the upper limit value, it is determined as rejected (S84: NG), and the process returns to the phase adjustment process S30.

  As described above, the settling period adjustment process S90 is a process for adjusting the length of the settling period so that the period of the scanning period including the sampling period, the braking period, and the settling period is matched with the frame rate F of the video signal. is there.

If the lengths of the sampling period, the braking period, and the settling period are T ₁ , T ₂ , and T ₃ , respectively, the period of the scanning period is T ₁ + T ₂ + T ₃ . On the other hand, the frame period of the video signal is expressed as 1 / F using the frame rate F. Accordingly, when the period of the scanning period coincides with the period of the frame of the video signal, the following Expression 3 is established, and the length T3 of the settling period is expressed by Expression 4 derived from Expression 3.

In the present embodiment, the lengths of the sampling period, the braking period, and the settling period are set as relative values with the drive cycle T _f (= 1 / f) of the biaxial actuator 204C as a basic unit. For example, the length of the sampling period is set to 500 _Tf . Frame rate F, the period T ₂ of the cycle T1 and the braking period of the sampling period is set in advance, also, the driving cycle T _f of the biaxial actuator 204C, the biaxial actuator 204C set in the frequency adjustment process S10 Since it is obtained from the driving frequency f, the period T ₃ of the settling period is calculated by the above equation 4.

  The above is the description of the embodiment of the present invention. However, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical idea. For example, in the above-described embodiment, after the processing (phase adjustment processing) S30 for adjusting the phase difference between the AC voltage X and the AC voltage Y is completed in the scanning parameter adjustment processing S4, the AC voltage X and the AC voltage Y are adjusted. Although the configuration in which the process of adjusting the amplitude (amplitude adjustment process) S50 is performed is adopted, the order of performing the phase adjustment process S30 and the amplitude adjustment process S50 may be reversed from that of the above embodiment. Further, before the pass / fail judgment S83 of the scanning diameter, the phase adjustment process S30 and the amplitude adjustment process S50 are alternately and repeatedly executed (for example, the phase adjustment process S30 or the amplitude adjustment process S50 is executed at least twice). It may be. Since there is a certain correlation between the phases and amplitudes of the AC voltages X and Y, when one parameter is adjusted, the other parameter is affected and changes somewhat. For this reason, the phase adjustment process S30 and the amplitude adjustment process S50 are alternately and repeatedly performed, thereby enabling more reliable and accurate adjustment. Further, the phase adjustment processing S30 and the amplitude adjustment processing S50 are integrated (that is, the scanning trajectory acquisition processing S32 and S53 are combined), and the adjustment is advanced in parallel while changing the phase and the amplitude little by little alternately. It is good also as a structure. This configuration improves the efficiency of parameter adjustment when the correlation between phase and amplitude is large.

  In the present embodiment, the CPU 108 has been described as executing the calibration program. However, the present invention is not limited to this configuration, and the calibration circuit 412 may execute the calibration program. In this case, the calibration circuit 412 is configured to control the biaxial actuator 204C, change adjustment parameters, and the like by communication with the CPU 108.

  In the calibration program S1 of the present embodiment, the XY adjustment and the Z adjustment are performed in a state where the rotation driving of the optical fiber 202 is stopped. For example, the spot position of the excitation light during the braking period is initially set. If it is detected as a spot formation position, XY adjustment and Z adjustment can be performed even when the optical fiber 202 is rotationally driven.

  A system to which the present invention is applicable is not limited to the scanning confocal endoscope system described in the present embodiment. The scanning area enlarged by the relay lens unit 406 only needs to be received by the PSD 404, and can be applied to a general scanning endoscope system. For example, the present invention may also be applied to a scanning endoscope system that employs a raster scan method that reciprocally scans the horizontal direction of the scan region, a Lissajous scan method that scans the scan region sinusoidally, and the like.

  In addition, the confocal optical unit 204 of the present embodiment is configured to be incorporated in the distal end portion of the confocal endoscope 200. However, the confocal optical unit 204 is inserted into a treatment instrument insertion channel of the endoscope, for example. And may be incorporated into a confocal probe to be used.

  Further, the position detection element mounted on the calibration apparatus 400 is not limited to PSD. The PSD 404 may be replaced with another element capable of detecting the position and light quantity, such as a CCD (Charge Coupled Device) or an array type PMT (Photomultiplier Tube).

1 Scanning Confocal Endoscope System 100 System Main Body 102 Light Source 104 Optical Demultiplexer / Multiplexer 106 Damper 108 CPU
110 CPU memory 112 Optical fiber 114 Light receiver 116 Video signal processing circuit 118 Image memory 120 Video signal output circuit 200 Confocal probe 202 Optical fiber 204 Confocal optical unit 206 Sub CPU
208 Sub Memory 210 Scan Driver 400 Calibration Device 402 Case 404 PSD
405 PSD board 406 Relay lens unit 408 XYZ stage 410 Stage drive motor 412 Calibration circuit

Claims (25)

An optical fiber that guides light emitted from a light source, and an actuator that cantilever-supports the tip of the optical fiber and vibrates the optical fiber in two radial directions that are orthogonal to each other, the X-axis direction and the Y-axis direction And a control for controlling the drive voltage in the X-axis direction and the Y-axis direction of the actuator based on predetermined scanning parameters so that the light emitted from the tip of the optical fiber is scanned in a spiral trajectory And a scanning trajectory detecting means for detecting a scanning trajectory of scanning light emitted from the tip of the optical fiber, and a scanning endoscope having an optical scanning device that periodically performs spiral optical scanning A system automatic calibration method,
An optical scanning step in which the control means performs the optical scanning by driving the actuator based on the scanning parameter;
A scanning trajectory acquisition step in which the control means acquires a scanning trajectory of scanning light emitted from the tip of the optical fiber from the scanning trajectory detection means;
An adjustment step in which the control means adjusts the scanning parameter so that the acquired scanning trajectory becomes a predetermined reference scanning trajectory;
Including
The adjustment step includes
A frequency adjustment step of adjusting the frequency of the drive voltage of the actuator so that the amplitude of the scanning locus is maximized;
A phase adjustment step of adjusting a phase difference between the drive voltages in the X-axis direction and the Y-axis direction of the actuator so that the scanning locus becomes a substantially perfect circle;
An amplitude adjustment step of adjusting the amplitude of the drive voltage in the X-axis direction and the Y-axis direction of the actuator so that the size and shape of the scanning locus are within a predetermined range;
A method for automatically calibrating a scanning endoscope system, comprising:   2. The automatic calibration method for a scanning endoscope system according to claim 1, wherein the phase adjustment step and the amplitude adjustment step are executed after the frequency adjustment step.   3. The automatic calibration method for a scanning endoscope system according to claim 1, wherein the adjustment step further includes a polar coordinate conversion step of converting the coordinates of the scanning trajectory into polar coordinates. The frequency adjusting step includes
Obtaining a frequency at which the amplitude of the scanning trajectory is maximum in a frequency region including a resonance frequency of the tip of the optical fiber that is cantilevered;
Changing the frequency of the drive voltage of the actuator to a frequency at which the amplitude of the scanning trajectory is maximized.
The automatic calibration method for a scanning endoscope system according to any one of claims 1 to 3, wherein: The step of obtaining the frequency at which the amplitude of the scanning locus is maximum includes the step of repeatedly obtaining the amplitude of the scanning locus while changing the frequency of the drive voltage in a frequency region including the resonance frequency.
The method for automatically calibrating a scanning endoscope system according to claim 4. The step of obtaining the frequency at which the amplitude of the scanning trajectory is maximized,
A first frequency acquisition step of repeatedly acquiring the amplitude of the scanning locus while gradually changing the frequency of the drive voltage at a first frequency interval in a first frequency region including the resonance frequency;
In the second frequency region that is narrower than the first frequency region, including the frequency of the driving voltage at which the maximum amplitude of the scanning locus is acquired in the first frequency acquisition step, the frequency of the driving voltage is set to the first frequency A second frequency acquisition step of repeatedly acquiring the amplitude of the scanning trajectory while changing stepwise at a second frequency interval narrower than the frequency interval,
The automatic calibration method for a scanning endoscope system according to claim 5. The phase adjustment step includes
Repetitively acquiring the amplitude of the scanning locus while changing the phase difference between the driving voltage of the actuator in the X-axis direction and the Y-axis direction;
Extracting the amplitude for a predetermined one turn from the acquired spiral scan trajectory;
Calculating a variance value of the amplitude for one turn;
Changing the phase difference between the driving voltage of the actuator in the X-axis direction and the Y-axis direction to a value at which the variance value of the amplitude for one turn is minimized.
The method for automatically calibrating a scanning endoscope system according to any one of claims 1 to 6, wherein: The scanning endoscope according to any one of claims 1 to 7, wherein the phase adjustment step and the amplitude adjustment step are alternately performed until the scanning locus becomes a substantially perfect circle. Automatic system calibration method. Performing the phase adjustment step or the amplitude adjustment step at least twice;
The method for automatically calibrating a scanning endoscope system according to claim 8. The amplitude adjustment step includes:
Obtaining the scanning trajectory;
An amplitude determination step for determining whether amplitudes in at least two directions of the scanning locus satisfy a predetermined amplitude determination condition;
A drive amplitude adjustment step of adjusting the amplitude of the drive voltage of the actuator for at least a direction that does not satisfy the amplitude determination condition,
The method for automatically calibrating a scanning endoscope system according to any one of claims 1 to 9, wherein: The amplitude determination condition is:
A first condition that the amplitude in the at least two directions is greater than or equal to a predetermined target value;
A second condition that the amplitude difference in at least two directions is a predetermined value or less,
The method for automatically calibrating a scanning endoscope system according to claim 10. The at least two directions include the X-axis direction and the Y-axis direction,
The drive voltage amplitude of the actuator in the direction not satisfying the first condition is increased only when the amplitude of the scanning locus in the X-axis direction or the Y-axis direction does not satisfy the first condition. The automatic calibration method according to claim 11. The amplitude adjustment step further includes an amplitude comparison step of comparing the amplitudes of the scanning trajectories in the X-axis direction and the Y-axis direction to determine the magnitude.
The amplitude of the drive voltage is adjusted according to the determination result of the amplitude comparison step.
The method for automatically calibrating a scanning endoscope system according to any one of claims 10 to 12, wherein: The amplitude of the drive voltage in the direction in which the amplitude of the scanning locus is determined to be small in the amplitude comparison step only when the amplitude of the scanning locus in the X-axis direction and the Y-axis direction does not satisfy the first condition. Is increased more than the amplitude of the driving voltage in the direction determined to be large,
The automatic calibration method for a scanning endoscope system according to claim 13. When the amplitude of the scanning locus in the X axis direction and the Y axis direction satisfies both the first condition and the second condition is not satisfied, the amplitude of the scanning locus is large in the amplitude comparison step. The amplitude of the drive voltage in the determined direction is reduced,
15. The automatic calibration method for a scanning endoscope system according to claim 13 or 14, wherein the method is automatically calibrated. In the amplitude determination step, amplitudes in 8 directions at intervals of π / 4 are determined.
The method for automatically calibrating a scanning endoscope system according to any one of claims 10 to 15, wherein: The control means further includes a pass / fail determination step of determining pass / fail of the scanning trajectory,
The pass / fail determination step is executed after the frequency adjustment step, the phase adjustment step, and the amplitude adjustment step.
The method for automatically calibrating a scanning endoscope system according to any one of claims 1 to 16, wherein: The acceptance / rejection determination step further includes a scanning diameter acceptance / rejection determination step for determining acceptance / rejection of the size of the spiral scanning trajectory,
The scanning diameter pass / fail determination step includes:
Obtaining an amplitude of one turn of the outermost circumference of the spiral scanning trajectory;
Determining whether or not all of the amplitude of one turn of the outermost circumference is equal to or greater than a target value,
Only when the amplitude of one turn of the outermost circumference is not less than a target value, the size of the spiral scanning trajectory is determined to be acceptable.
The automatic calibration method for a scanning endoscope system according to claim 17. Only when it is determined to be unacceptable in the scanning diameter acceptance / rejection determination step, the frequency adjustment step is executed again.
The automatic calibration method for a scanning endoscope system according to claim 17 or 18, wherein the method is automatically calibrated. The pass / fail determination step further includes a roundness pass / fail determination step for determining pass / fail of the roundness of the spiral scanning trajectory.
The method for automatically calibrating a scanning endoscope system according to any one of claims 17 to 19, wherein the method is automatically calibrated. Only when the roundness determination step is determined to be unacceptable, the phase adjustment step is executed again.
21. The automatic calibration method for a scanning endoscope system according to claim 20, wherein: The scanning endoscope system detects return light from a subject irradiated with the scanning light, and generates and outputs a video signal for displaying a video of the subject on a monitor based on the detection result Further comprising:
The adjusting step further includes a driving stop time adjusting step of adjusting a time for stopping the driving of the actuator so that a period of the spiral scan coincides with a reciprocal of a frame rate of the video signal.
The method for automatically calibrating a scanning endoscope system according to any one of claims 1 to 21, wherein: After the frequency adjustment step, the phase adjustment step, and the amplitude adjustment step, the drive stop time adjustment step is executed.
The method for automatically calibrating a scanning endoscope system according to claim 22. Performing the drive stop time adjustment step after the pass / fail determination step;
The automatic calibration method for a scanning endoscope system according to claim 22 or 23, which directly or indirectly references claim 17. An optical fiber that guides the light emitted from the light source, and cantilevered at the tip of the optical fiber, and vibrates in the X-axis direction and the Y-axis direction, which are two radial directions orthogonal to each other. And the drive voltage in the X-axis direction and the Y-axis direction of the actuator based on predetermined scanning parameters so that the light emitted from the tip of the optical fiber is scanned in a spiral trajectory And a scanning trajectory detecting means for detecting a scanning trajectory of scanning light emitted from the tip of the optical fiber, and comprising a light scanning device that periodically performs spiral optical scanning. An endoscope system,
The control means includes
Frequency adjusting means for adjusting the frequency of the drive voltage of the actuator so that the amplitude of the scanning locus is maximized;
Phase adjusting means for adjusting a phase difference between driving voltages of the actuator in the X-axis direction and the Y-axis direction so that the scanning locus becomes a substantially perfect circle;
Amplitude adjusting means for adjusting the amplitude of the drive voltage in the X-axis and Y-axis directions of the actuator so that the size and shape of the scanning locus are within a predetermined range;
A scanning endoscope system.

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