JP2013121455A - Scanning type endoscope system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning type endoscope system capable of eliminating useless irradiation with light and obtaining endoscopic images of uniform brightness.SOLUTION: The scanning type endoscope system includes: an optical fiber for guiding illumination light to an emission end and emitting it to a subject; an optical fiber scanning means for cyclically moving the emission end of the optical fiber so that the illumination light emitted from the emission end of the optical fiber cyclically scans a two-dimensional scanning area on the subject; a light source control means for generating drive signals for driving the illumination light and ON/OFF controlling the illumination light on the basis of the drive signals; an image signal detection means for receiving scattered light from the subject and detecting image signals at prescribed detection timing; and an image generation means for allocating two-dimensional pixel positions corresponding to the detection timing of the image signals, arraying the image signals at the pixel positions and generating the endoscopic images. The light source control means generates the drive signals on the basis of the detection timing of the image signals so that the irradiation density of the illumination light is roughly fixed in the entire scanning area.

Description

  The present invention relates to a scanning endoscope system that scans light guided by an optical fiber with respect to an observation site and receives reflected light or fluorescence to form an image.

  Conventionally, as one of the scanning endoscope systems, a scanning confocal endoscope system is known (for example, Patent Document 1). A scanning confocal endoscope system irradiates a living tissue to which a drug is administered with a laser beam, and among the fluorescence emitted from the living tissue, a pin arranged at a position conjugate to the focal position of the confocal optical system By extracting only the components through the holes, the living tissue can be observed at a higher magnification than an observation image obtained by a normal endoscope optical system. In a scanning confocal endoscope system, it is impossible to observe at a magnification of an observation image obtained by a normal endoscope optical system by scanning a laser beam irradiated to a living tissue in two dimensions or three dimensions. It is configured so that a minute object can be observed or a tomographic part of a living tissue can be observed.

  In recent years, scanning endoscope systems have been proposed in which light guided by an optical fiber is scanned in a spiral manner with respect to an observation site, and the reflected light is received and imaged (for example, Patent Documents). 2-4). In such a scanning endoscope system, a single mode type optical fiber is provided in the endoscope, and a base end portion thereof is held in a cantilever shape by a piezoelectric actuator. Then, the piezoelectric actuator modulates and amplifies the vibration amplitude, two-dimensionally vibrates (resonates) the fiber tip according to the natural frequency, 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 is irradiated spirally toward the observation site, and an image of the irradiation region (scanning region) is acquired.

  In recent years, a scanning endoscope system configured to scan light in a spiral shape as described in Patent Documents 2 to 4 is used as a scanning confocal endoscope as described in Patent Document 1. Application to a mirror system has also been proposed (for example, Patent Document 5).

JP 2004-321792 A US Pat. No. 6,856,712 US Pat. No. 6,959,130 US Pat. No. 6,975,898 JP 2010-162090 A

  The scanning endoscope systems described in Patent Documents 2 to 5 include a plurality of piezoelectric actuators in the vicinity of the tip of the optical fiber, and an optical fiber is applied by applying a voltage having a predetermined period and amplitude to each piezoelectric actuator. Is bent in a predetermined direction, and the continuous light guided by the optical fiber is swirled with respect to the observation site. Then, reflected light from the 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 displayed on the monitor display coordinate system (endoscopic image). A two-dimensional endoscope image is displayed by assigning to a pixel position.

  FIG. 12 is a schematic diagram showing a relationship between a light scanning locus and a sampling point in a conventional scanning endoscope system. As shown in FIG. 12, the conventional scanning endoscope system adopts a configuration in which continuous light is scanned in a spiral shape from the central portion of the scanning region to the peripheral portion. Since the configuration is used, the light scanning speed is different between the central portion and the peripheral portion of the scanning region, and the sampling points are concentrated in the central portion of the scanning region. When such sampling points are assigned to the display coordinate system of the monitor, a plurality of sampling points are assigned to the same display coordinates in the central portion of the scanning region. In addition, the process of assigning sampling points to the display coordinate system of the monitor is a process of assigning a spiral scanning trajectory to a pixel position of a square-arranged endoscopic image, so that a plurality of adjacent scanning trajectories have the same endoscope. In some cases, the pixels pass through the mirror image, and in this case, a plurality of sampling points are assigned to the same display coordinates. When a plurality of sampling points are assigned to the same display coordinates, the luminance information obtained at the extra sampling points has been discarded. That is, the conventional scanning endoscope system has a problem in terms of power consumption, light source life, and the like because light is irradiated even at unnecessary sampling points.

In the conventional scanning endoscope system, since the scanning speed of light is not constant, the light amount (irradiation) per unit area of the scanning region (that is, the observation region) is obtained between the central portion and the peripheral portion of the scanning region. Energy) will be very different. Therefore, when the scanning endoscope system having such a configuration is applied to a scanning confocal endoscope system using fluorescence from a living tissue as described in Patent Document 1, irradiation per unit area is performed. As a result of phosphor decomposition progressing faster in the center of the high energy scanning area, the center of the scanning area becomes darker (fading) than the surrounding area, and the endoscope has a uniform brightness. There arises a problem that an image cannot be obtained.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a scanning type endoscope that eliminates unnecessary light irradiation and can obtain an endoscopic image with uniform brightness. It is to provide a mirror system.

  In order to achieve the above object, a scanning confocal endoscope system according to the present invention includes an optical fiber that guides illumination light incident on an incident end to an output end, and emits the light from the output end to a subject. An optical fiber scanning means for periodically moving the exit end of the optical fiber so that the illumination light emitted from the exit end periodically scans within the two-dimensional scanning region on the object; and for driving the illumination light A light source control unit that generates a drive signal and controls on / off of illumination light based on the drive signal; an image signal detection unit that receives scattered light from a subject and detects an image signal at a predetermined detection timing; Image generation means for assigning a two-dimensional pixel position corresponding to the detection timing of the image and arranging the image signal at the assigned pixel position to generate an endoscopic image, and the light source control means comprises an illumination density of illumination light Scan area And generating a drive signal based on the detection timing of the image signal so as to be substantially constant in the entire area of.

  With such a configuration, since the irradiation energy of the illumination light becomes substantially uniform over the entire scanning region, it is possible to obtain an endoscopic image with uniform brightness. Moreover, since unnecessary illumination light is not emitted, power consumption is also reduced.

  Further, the light source control means, when a plurality of image signal detection timings are assigned to the same two-dimensional pixel position, sets a predetermined pulse width using any one of the plurality of image signal detection timings as a reference timing. It is possible to generate the driving pulse having the driving pulse and generate the driving signal based on the driving pulse. According to such a configuration, since one pulse of illumination light is assigned to each pixel of the endoscopic image, an endoscopic image having uniform brightness can be obtained.

  The reference timing is preferably the detection timing that is located on the outermost side in the scanning region among the detection timings of a plurality of image signals assigned to the same two-dimensional pixel position.

  Further, the light source control means can be configured to generate a drive pulse prior to the reference timing.

  Further, it is preferable that the light source control means generates the drive pulse so as to include the reference timing. According to such a configuration, it becomes possible to reliably detect the scattered light generated by the pulsed illumination light at the reference timing.

  The light source control means includes first input means for receiving an input from the user, and adjusts a time between the generation timing of the drive pulse and the reference timing in accordance with the user input received by the first input means. Can be configured to. According to such a configuration, since it is possible to arbitrarily adjust the timing at which illumination light starts to be emitted, even if a change occurs in the signal delay time due to a change in the system configuration, Scattered light generated by the illumination light can be reliably detected at the reference timing.

  The pulse width of the drive pulse is preferably longer than the period of the detection timing of the image signal. According to such a configuration, it is possible to reliably detect scattered light even when the delay time or the like caused by the system varies.

  The light source control unit may include a second input unit that receives an input from the user and adjusts the pulse width of the drive pulse according to the user input received by the second input unit. According to such a configuration, it is possible to reliably detect scattered light even when the delay time or the like caused by the system varies.

  Further, it is preferable that the optical fiber scanning unit moves the emission end of the optical fiber so that the scanning speed of the illumination light is not constant. In this case, the optical fiber scanning unit may be configured so that the emission end of the optical fiber is simply oscillated in two directions orthogonal to each other so that the illumination light performs Lissajous scanning in the scanning region at a constant period. . Further, the optical fiber scanning means rotationally drives the emission end of the optical fiber in a spiral shape so that the illumination light rotates and scans in a spiral shape at a constant rotation period from the center to the periphery in the scanning region. You may comprise.

  Further, it is preferable that the light source control means generates a driving pulse when the illumination light scans the central portion in the scanning region. In this case, it is preferable that the diameter of the central portion in the scanning region is approximately 1/3 or less of the diameter of the scanning region. According to such a configuration, it is not necessary to generate a drive pulse when the excitation light scans the peripheral portion in the scanning region, and thus a load necessary for generating the drive pulse is reduced.

  In addition, the optical fiber scanning unit rotates the emission end of the optical fiber in a spiral shape, and then stops rotational driving of the emission end of the optical fiber for a predetermined period. The light source control unit performs illumination light for a predetermined period. It is preferable that the light emission is stopped. According to such a configuration, power consumption is further reduced.

  Further, a confocal pinhole disposed at a position conjugate with the condensing point of the illumination light is provided, and the image signal detecting means can be configured to receive the scattered light through the confocal pinhole. According to such a configuration, although it functions as a confocal endoscope, the irradiation energy of the illumination light (excitation light) becomes substantially uniform over the entire scanning region, so that the phosphor is decomposed in the scanning region. Therefore, it is possible to obtain an endoscopic image (confocal image) with uniform brightness.

  According to the scanning endoscope system of the present invention, it is possible to obtain an endoscopic image with uniform brightness because unnecessary light irradiation is eliminated.

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 intensity | strength of the excitation light which the light source of embodiment of this invention radiate | emits. It is a figure which shows the relationship between the position (sampling point) of the excitation light and the pixel position (raster coordinate) of an endoscopic image of embodiment of this invention. It is a figure which shows an example of the remapping table and light emission pattern data of embodiment of this invention. It is a figure explaining the correspondence of a sampling point and a raster coordinate in embodiment of this invention. It is a flowchart of the light emission pattern data generation process performed with the scanning confocal endoscope system of embodiment of this invention. It is a figure which shows typically the relationship between the excitation light irradiated in a pulse form based on the light emission pattern data of embodiment of this invention, and a raster coordinate. It is a timing chart which shows the relationship between each sampling point and a laser drive signal. It is a figure which shows the intensity | strength of excitation light in the modification of embodiment of this invention. It is a schematic diagram which shows the relationship between the scanning locus | trajectory of light and a sampling point in the conventional scanning endoscope system.

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

  FIG. 1 is a block diagram showing a configuration of a scanning confocal endoscope system 1 according to an embodiment of the present invention. The scanning confocal endoscope system 1 according to 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. As shown in FIG. 1, the scanning confocal endoscope system 1 includes a system main body 100, a confocal probe 200, a monitor 300, and a calibration unit 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 probe 200 is applied to the subject.

  The system main body 100 includes a light source 102, an optical demultiplexer / multiplexer (photocoupler) 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 remap table. A memory 119, a video signal output circuit 120, a laser control circuit 122, and an A / D converter 130. The confocal probe 200 includes an optical fiber 202, a confocal optical unit 204, a sub CPU 206, a sub memory 208, and a scanning driver 210.

  The light source 102 emits excitation light (for example, laser light having a wavelength of 488 nm) that excites the medicine administered into the body cavity of the patient in accordance with the drive control of the laser control circuit 122 according to the instruction 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 probe 200.

  The proximal end of the optical fiber 202 is coupled to the optical demultiplexer / multiplexer 104 through the optical connector 152. The tip of the optical fiber 202 is housed in a confocal optical unit 204 that is built into the tip of the confocal probe 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 based on control by the CPU.

  The sub memory 208 stores probe information such as identification information and various properties of the confocal probe 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 probe 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 probe 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 resonate the piezoelectric body in the X direction, and also applies 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 resonates 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. FIG. 3 shows the rotation locus of the tip 202a on the XY approximate plane.

  The excitation light emitted from the light source 102 is transmitted through the optical fiber 202 in accordance with the laser drive signal supplied from the laser control circuit 122 to the light source 102 during the period from the start of application of AC voltage to the biaxial actuator 204C to the stop of application. The light is emitted from the tip 202a in a predetermined light emission pattern. Hereinafter, for convenience of explanation, this period is referred to as a “sampling period”. 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 XY approximate plane converges as the vibration of the optical fiber 202 is attenuated, and stops on the central axis AX after a predetermined time. Hereinafter, for convenience of explanation, a period from the end of the sampling period until the tip 202a stops on the central axis AX (more precisely, in order to guarantee the stop on the central axis AX, calculation required to stop) The period of time slightly longer than the above time) is referred to as a “braking period”. The period corresponding to one frame is composed of one sampling period and one braking period. In order to shorten the braking period, the reverse torque may be applied to the biaxial actuator 204C in the initial stage of the braking period to positively apply the braking torque.

  An objective optical system 204D is installed in front of the tip 202a of the optical fiber 202 (FIG. 2). 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 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 formation position is displaced in the Z-axis direction in accordance with the advance / retreat of the tip 202a that 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 (hereinafter referred to as “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 locus of the tip 202a is measured in advance using the calibration unit 400, and the spot formation position and the sampling point are estimated based on the actual measurement result. Then, the position on the corresponding image (the pixel position of the endoscopic image displayed on the monitor 300) and the emission pattern of the excitation light are determined from the sampling point. The correspondence between the sampling point and the pixel position (pixel address) of the endoscopic image is stored as a remap table in the remap table memory 119 connected to the video signal processing circuit 116, and the sampling points of the remap table and The correspondence between the pixel address and the light emission pattern of the excitation light is stored as light emission pattern data in a light emission pattern memory 122a built in the laser control circuit 122 (details will be described later).

  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, the subject is scanned in a spiral shape (spiral scan) from the center of the scanning region to the periphery in the XY direction (FIG. 3), but the optical fiber 202 has a spiral period ( The time required for scanning for one rotation is the same. For this reason, the irradiation density (irradiation energy per unit area) of the excitation light increases toward the center of the scanning region, and the decomposition of the phosphor progresses more rapidly, causing discoloration. As a result, there is a problem that the image becomes dark at the center of the observation area where the observation subject is located. Therefore, the scanning confocal endoscope system 1 according to the present embodiment is configured to appropriately suppress the fluorescence fading by appropriately controlling the emission pattern of the excitation light.

  FIG. 4A is a diagram illustrating the movement of the tip 202 a of the optical fiber 202. FIG. 4B is a diagram illustrating the intensity of the excitation light emitted from the light source 102. Both the horizontal axes of FIGS. 4A and 4B are time axes. The vertical axis in FIG. 4A indicates the amount of displacement in the X (or Y) direction of the tip 202a with respect to the central axis AX. The vertical axis | shaft of FIG.4 (b) shows the intensity | strength of excitation light. As shown in FIG. 4B, in the present embodiment, pulsed excitation light is emitted during the sampling period (hereinafter, the period in which the pulsed excitation light is emitted is referred to as “pulse drive period”). .) As will be described later, the light emission pattern (light emission timing) of the excitation light during the pulse drive period is determined by the light emission pattern data generated based on the remapping table, and in this embodiment, one pulse having a predetermined pulse width. The light emission pattern data is generated so that the excitation light corresponds to one pixel of the endoscopic image. As described above, since the scanning speed of the central portion of the scanning region is slower than the scanning speed of the peripheral portion, many sampling points are concentrated on one pixel of the endoscopic image corresponding to the central portion of the scanning region. With such a configuration, unnecessary (overlapping) sampling points are thinned out so that the irradiation density of the excitation light is substantially constant over the entire scanning region. Therefore, according to the present embodiment, the irradiation energy of the excitation light is reduced particularly in the central portion of the scanning region where a large number of sampling points are concentrated. It will be suppressed. In the present embodiment, the emission of excitation light is controlled to stop during the braking period. Therefore, the phosphor is not decomposed by unnecessary excitation light during the braking period. In addition, according to the present embodiment, unnecessary excitation light emission is eliminated, so that power consumption is reduced as compared with the conventional configuration described above. Therefore, the scanning confocal endoscope system 1 of the present embodiment is particularly effective when used in a system using a battery. Further, according to the present embodiment, the irradiation time of the excitation light can be reduced as compared with the conventional configuration described above, so that the life of the light source 102 is extended, and the endoscope distal end is heated by the excitation light. This is also prevented. That is, compared with the conventional configuration, the product life and safety are significantly improved.

  As described above, in the present embodiment, the emission pattern of the excitation light during the pulse drive period is determined by the emission pattern data generated based on the remapping table. Hereinafter, a method of creating the remapping table and the light emission pattern data of this embodiment will be described in detail.

  The remap table is created by measuring the rotation locus of the tip 202a of the optical fiber 202 using the calibration unit 400 (FIG. 1). The measurement of the rotation trajectory of the tip 202a by the calibration unit 400 is a so-called calibration operation performed before using the scanning confocal endoscope system 1 of the present embodiment, and the calibration unit 400 is used as the confocal optical unit 204. This is done by placing it at the tip.

  The calibration unit 400 includes a PSD (Position Sensitive Detector) 402 and an amplifier 404 (FIG. 1). The PSD 402 is a semiconductor position detection element, and is an optical sensor that detects the position of excitation light emitted from the confocal optical unit 204. When the calibration unit 400 is disposed at the tip of the confocal optical unit 204, the PSD 402 is disposed to face the tip 202a of the optical fiber 202 of the confocal optical unit 204. In this state, the CPU 108 controls the light source 102 and the scanning driver 210 to continuously emit excitation light while scanning (rotating) the tip 202a of the optical fiber 202 in a spiral shape. The excitation light emitted from the tip 202a of the optical fiber 202 is received by the PSD 402, and the position information of the excitation light scanned in a spiral shape is sequentially converted into a current and output. The current output from the PSD 402 is converted into a voltage by the amplifier 404 and sent to the A / D 130 of the system main body 100. Then, after being sampled by the A / D 130 at a predetermined sampling frequency (for example, 54 MHz), converted into a digital value, the position information of the excitation light converted into the digital value is sequentially stored in the CPU memory 110. . Here, the sampling frequency is a frequency corresponding to the time taken to scan approximately one pixel of the endoscopic image in the peripheral portion of the scanning region.

  Next, the CPU 108 creates a remap table by associating the position information of the excitation light stored in the CPU memory 110 with the image memory 118 and stores the remap table in the remap table memory 119. In other words, the remapping table is a table that describes the correspondence between the position information of the excitation light and the endoscopic image displayed on the monitor 300. For example, the remap table represents 15 pixels in the horizontal direction (X direction), When configured with 15 pixels in the vertical direction (Y direction), the relationship between the sequentially sampled excitation light position (sampling point) and the endoscopic image pixel position (raster coordinates) is as shown in FIG. Based on this relationship, the CPU 108 obtains the pixel position (raster coordinates) of the endoscopic image corresponding to each sampling point and creates a remap table. Further, in the present embodiment, excitation light is emitted in a pulse shape in order to prevent the occurrence of fading due to the concentration of a plurality of sampling points on the same pixel of the endoscopic image in the central portion of the scanning region. The light emission pattern data for making it generate is created. 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.

  FIG. 6 is a diagram illustrating an example of the remap table and the light emission pattern data created by the CPU 108. FIG. 7 is a diagram for explaining the correspondence between sampling points and raster coordinates. As shown in FIGS. 5 to 7, in this embodiment, it is assumed that the endoscopic image is composed of 15 pixels in the horizontal direction (X direction) and 15 pixels in the vertical direction (Y direction), and excitation light. Is assumed to be scanned spirally from raster coordinates (8,8) to (8,15). In addition, it is assumed that there are 1000 sampling points during the sampling period (that is, while being scanned spirally from raster coordinates (8, 8) to (8, 15)). (Sampling point number). 7 indicate each sampling point, and the number assigned to each sampling point corresponds to the sampling point number in FIG. In FIG. 7, in consideration of easy viewing of the drawing, a part of sampling points in the central portion of the scanning region are shown. However, in actuality, a large number of sampling points are shown along a spiral scanning locus shown by a solid line. Sampling points exist.

  As shown in FIG. 6, since the scanning speed is extremely low at the approximate center of the scanning region, many sampling points are concentrated on the same pixel (raster coordinate) of the endoscopic image (FIG. 6). 6 sampling points 1-10). As the scanning progresses outward, the interval between the sampling points gradually increases. However, in the central portion of the scanning region (for example, the first 1/3 period of the sampling period), a plurality of consecutive sampling points have the same raster. In some cases, the coordinates are assigned (sampling points 201 to 310 in FIG. 6). Further, as shown in FIGS. 6 and 7, since the remapping is a process of assigning the spiral scanning trajectory of the excitation light to the pixel positions of the squarely arranged endoscopic image, for example, sampling points 204 and 205 are used. , 303, and 304, the same endoscopic image pixels may pass through the inside and outside of the scanning trajectory (that is, the same raster coordinates may be assigned). As described above, when a plurality of sampling points are assigned to the same raster coordinate and the excitation light is irradiated at all the sampling points, the irradiation energy per unit area becomes high particularly in the central portion of the scanning region, and Decomposition proceeds faster and fluorescent discoloration occurs. Therefore, in the present embodiment, the CPU 108 executes a light emission pattern data generation process, which will be described later, so that the excitation light is emitted only once at a position corresponding to each pixel of the endoscopic image. Data is being generated. Specifically, when a plurality of sampling points are assigned to each raster coordinate, light emission pattern data is generated so that the excitation light is pulsed at the outermost sampling point (that is, the largest sampling point number). Processing is in progress. For example, in FIGS. 6 and 7, sampling points 204, 205, 303, and 304 are assigned to raster coordinates (6, 7), but light is emitted so that excitation light is emitted only at the positions of sampling points 304. The pattern data is set to “1”, and the emission pattern data is set to “0” so that excitation light is not emitted at the positions of the sampling points 204, 205, and 303. The black circles in FIG. 7 indicate sampling points at which the excitation light emits pulses, and the white circles indicate sampling points at which the excitation light does not emit pulses (that is, extinguishes).

  FIG. 8 is a flowchart of the light emission pattern data generation process executed in the scanning confocal endoscope system 1 of the present embodiment. The light emission pattern data generation process of the present embodiment is a subroutine executed by the CPU 108 when the remap table is created by the CPU 108. As shown in FIG. 8, when the light emission pattern data generation process is started, the CPU 108 executes Step S1.

  In step S1, the CPU 108 refers to the remap table, stores the X coordinate value of the raster coordinate of each sampling point in a one-dimensional array x [N] of size N, and sets the Y coordinate value to a one-dimensional size of N. Store in array y [N]. Here, N means the maximum value of the sampling point number. In the case of FIGS. By the processing in step S1, the X coordinate value and the Y coordinate value of each sampling point are stored in each element of the array x and the array y in order, and each index of the array x and the array y corresponds to each sampling point number. It will be. Next, the process proceeds to step S2.

  In step S <b> 2, the CPU 108 prepares a two-dimensional array n [M] [M] having a size M × M, and initializes all elements to “0”. Here, M means the number of pixels in the X direction and the Y direction of the endoscopic image (that is, each index of the array n corresponds to each raster coordinate). In the case of FIGS. Is. In this way, each element of the two-dimensional array n corresponds to each pixel (raster coordinate) of the endoscopic image. As will be described later, the sampling point number of the sampling point where the excitation light is to be pulsed is set. Remembered. Next, the process proceeds to step S3.

  In step S3, the CPU 108 prepares a one-dimensional array v [N] of size N and initializes all elements to “0”. As will be described later, the array v is an array for storing light emission pattern data. Next, the process proceeds to step S4.

  In step S4, the CPU 108 sets the loop variable k to N (that is, the maximum sampling point number). The loop variable k is a loop variable that is decremented in step S8 described later, and corresponds to the sampling point number. Next, the process proceeds to step S5.

  In step S5, the CPU 108 reads the element x [k] of the index k of the array x and the element y [k] of the index k of the array y, and whether or not each value is in the range of 1 to M. (That is, whether or not it is within the effective pixel range of the endoscopic image). As described above, the indices of the array x and the array y correspond to the sampling point numbers. Therefore, it is possible to confirm whether or not the raster coordinates assigned to the sampling point of sampling point number k are included in the effective pixel range of the endoscopic image by the processing in step S5. As will be described later, since the loop variable k is sequentially decremented in step S8, in step S5, the raster coordinates assigned to the sampling points are read out in descending order of the sampling point numbers, and the endoscopic image is read. It is confirmed whether or not it is included in the effective pixel range. If it is determined in step S5 that the raster coordinates assigned to the sampling point with the sampling point number k are included in the effective pixel range of the endoscopic image (step S5: YES), the process proceeds to step S6. If it is determined that it is not included in the effective pixel range of the endoscopic image (step S5: NO), the process proceeds to step S8.

  In step S6, the CPU 108 reads the element of the index [x [k]] [y [k]] of the array n (that is, the element corresponding to the raster coordinate assigned to the sampling point of the sampling point number k), and It is determined whether or not the value is smaller than the loop variable k. As described above, since all elements of the array n are initialized to “0”, when the step S6 is first executed (that is, the raster coordinates assigned to the sampling point of the sampling point number k are the array n). Since the loop variable k becomes larger than the initial value “0” (step S6: YES), the process proceeds to step S7, and the index [x [k]] [y [k]] is first matched. When step S6 is executed twice or more, the loop variable k is smaller than the element of the index [x [k]] [y [k]] of the array n (as described later) (step S6: NO). The process proceeds to step S8.

  In step S7, the value of the loop variable k is put into the element of the index [x [k]] [y [k]] of the array n, and “1” is put into the index [k] of the array v. As described above, step S6 reads the element of index [x [k]] [y [k]] of array n (that is, the element corresponding to the raster coordinate assigned to the sampling point of sampling point number k). , A process for determining whether or not the value is smaller than the loop variable k. Therefore, when the loop variable k is decremented in step S8, which will be described later, and step S6 is executed twice or more, the loop variable k is larger than the element of the index [x [k]] [y [k]] of the array n. It always becomes smaller and step S7 is not executed. That is, in step S6 and step S7, among the sampling points assigned to each raster coordinate, the outermost sampling point (that is, the largest sampling point number) is specified, and the index [x [k]] of the array n is specified. An array v (that is, light emission pattern data) that is stored in the element [y [k]] and becomes “1” at the specified sampling point is generated.

  In step S8, the CPU 108 decrements the loop variable k, and proceeds to step S9.

  In step S9, the CPU 108 determines whether or not the value of the loop variable k is 1 or more. As described above, since the loop variable k indicates the sampling point number, if the sampling point is smaller than 1 (step S9: NO), it is determined that the light emission pattern data has been generated for all sampling points. If the sampling point is 1 or more (step S9: YES), it is determined that the light emission pattern data has not yet been generated for all sampling points, and the process returns to step S5, and steps S5 to S5 are performed. S9 is repeatedly executed.

  As described above, the light emission pattern data is generated in the array v by the CPU 108 executing the light emission pattern data generation process. The light emission pattern data generated in this way is sent to and stored in a light emission pattern memory 122a built in the laser control circuit 122.

  When the remap table and the light emission pattern data are completed, the normal confocal observation (endoscopic observation) can be performed by removing the calibration unit 400 from the tip of the confocal optical unit 204. That is, the CPU 108 controls the laser control circuit 122 so that excitation light corresponding to the light emission pattern data is emitted from the light source 102 while scanning (rotating) the tip 202a of the optical fiber 202 in a spiral shape. Specifically, the laser control circuit 122 controlled by the CPU 108 generates the laser drive signal while sequentially calling the light emission pattern data of each sampling point from the light emission pattern memory 122a, and supplies the laser drive signal to the light source 102 to thereby generate the excitation light. Perform on / off control.

  FIG. 9 is a diagram schematically illustrating a relationship between excitation light irradiated in a pulse shape based on light emission pattern data and raster coordinates (pixel address of an endoscopic image). As shown in FIG. 9, as a result of irradiating the excitation light based on the emission pattern data, each pulse of the endoscopic image can be sampled at one sampling point only at the outermost sampling point. Excitation light will be irradiated. That is, the irradiation density of the excitation light is substantially constant throughout the scanning region.

  FIG. 10 is a timing chart showing the relationship between each sampling point and the laser drive signal. In FIG. 10, black circles indicate sampling points whose emission pattern data is “1”, and white circles indicate sampling points whose emission pattern data is “0”. As shown in FIG. 10, the laser drive signal of the present embodiment is a pulse signal having a certain width (for example, 5 samplings) centered on the sampling point where the light emission pattern data is “1”. This is because when the excitation light is irradiated for a time corresponding to one sampling point, the irradiation time of the excitation light is about 18.5 ns (1/54 MHz), and a sufficient amount of fluorescence is obtained from the relationship with the reaction time of the fluorescent reagent. This is because it is difficult to obtain the sampling point and it is difficult to accurately irradiate the sampling point with the excitation light due to the delay time caused by the system. Note that the delay time caused by the system varies depending on the components used, and the reaction time of the fluorescent reagent also varies depending on the type and observation target. Therefore, a user interface (not shown) provided in the system main body 100 is used. ), The pulse width of the laser drive signal may be variable.

  In addition, since it is considered that the signal delay time and the reaction time of the fluorescent reagent change due to changes in the system configuration and the fluorescent reagent, in this embodiment, a user interface (not shown) provided in the system main body 100 is used. By operating, the laser drive signal can be arbitrarily advanced with respect to the sampling point (that is, the timing at which the excitation light starts to be irradiated can be arbitrarily adjusted).

  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 present embodiment, the scanning confocal endoscope system has been described as an example. However, the present invention is not limited to the confocal configuration, and the normal scanning type endoscope described in Patent Documents 2 to 5 is used. It is also possible to apply to an endoscope system. Also in this case, the above-described light emission pattern data generation process is executed, and laser light (illumination light) is pulse-driven based on the light emission pattern data, whereby one pulse of illumination light is emitted to each raster coordinate. It becomes possible. Therefore, it is possible to obtain an endoscopic image with uniform brightness while suppressing the irradiation of unnecessary illumination light, reducing power consumption and extending the life of the laser light source as compared with the conventional configuration. In addition, the endoscope tip is prevented from being heated by the illumination light.

  In this embodiment, the scanning of the excitation light has been described as a spiral scan, but is not limited to this configuration. For example, the present invention can be applied to a so-called Lissajous scanning type scanning endoscope system in which excitation light is scanned sinusoidally by causing the tip 202a of the optical fiber 202 to vibrate in two directions orthogonal to each other. is there. Even in such a scanning method, since the scanning speed is slow at a specific portion of the scanning area (that is, the scanning speed of the excitation light gradually changes and does not become constant), a plurality of sampling points are set on the same raster coordinate. Is assigned. Therefore, there is a problem that the irradiation density is increased for some raster coordinates and the fading of fluorescence proceeds. However, even in such a scanning method, the above-described light emission pattern data generation process is executed, and the excitation light is pulse-driven based on the light emission pattern data, thereby irradiating each raster coordinate with one pulse of excitation light. Therefore, like the present embodiment, such a problem is effectively solved.

  In the present embodiment, the entire sampling period is set as the pulse drive period, and the excitation light is irradiated in a pulse shape with the laser drive signal based on the light emission pattern data. However, the irradiation density of the excitation light is in the entire scanning region. It is only necessary to be substantially constant, and the configuration is not limited to this. For example, since the fading of the fluorescence becomes conspicuous particularly in the central portion of the scanning region, as shown in FIG. 11, the light emission pattern data generation process is performed only on the central portion of the scanning region as the target of the pulse driving period, and the scanning region The light emission pattern data at each sampling point may be unconditionally set to “1” (that is, continuous light emission) in the peripheral portion of. In this case, based on the results of actual machine verification performed by the inventors, the first one-third period of the sampling period is set as a pulse driving period (that is, the first one-third period of the sampling period is set as the fluorescence period). It is preferable to control so that the excitation light is emitted in a pulsed manner, assuming that it is a period in which a fading occurs. With such a configuration, it is only necessary to generate light emission pattern data for sampling points corresponding to the pulse drive period, and the processing can be made efficient. Further, the pulse driving period may be arbitrarily set by the user operating a user interface (not shown).

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 119 Remap table memory 120 Video signal output circuit 122 Laser control circuit 122a Light emission pattern memory 130 A / D
200 confocal probe 202 optical fiber 204 confocal optical unit 206 sub CPU
208 Sub Memory 210 Scan Driver 300 Monitor 400 Calibration Unit 402 PSD
404 amplifier

Claims (15)

An optical fiber that guides illumination light incident on the incident end to the exit end, and exits the exit end to the subject;
Optical fiber scanning means for periodically moving the emission end of the optical fiber so that the illumination light emitted from the emission end of the optical fiber periodically scans in a two-dimensional scanning region on the subject. ,
Light source control means for generating a drive signal for driving the illumination light, and for controlling on / off of the illumination light based on the drive signal;
Image signal detecting means for receiving scattered light from the subject and detecting an image signal at a predetermined detection timing;
Image generation means for assigning a two-dimensional pixel position corresponding to the detection timing of the image signal, and arranging the image signal at the assigned pixel position to generate an endoscopic image;
With
The light source control means generates the driving signal based on the detection timing of the image signal so that the illumination density of the illumination light is substantially constant over the entire scanning region. Mirror system.   The light source control means, when a plurality of the image signal detection timings are assigned to the same two-dimensional pixel position, has a predetermined pulse width with any one of the plurality of image signal detection timings as a reference timing. 2. The scanning endoscope system according to claim 1, wherein a drive pulse having the following is generated, and the drive signal is generated based on the drive pulse.   The reference timing is a detection timing located on the outermost side in the scanning region among detection timings of the plurality of image signals assigned to the same two-dimensional pixel position. The scanning endoscope system described.   4. The scanning endoscope system according to claim 2, wherein the light source control unit generates the drive pulse prior to the reference timing. 5.   The scanning endoscope system according to any one of claims 2 to 4, wherein the light source control unit generates the drive pulse so as to include the reference timing.   The light source control means includes first input means for receiving an input from a user, and a time between the generation timing of the drive pulse and the reference timing according to the user input received by the first input means. The scanning endoscope system according to any one of claims 2 to 5, characterized in that adjustment is made.   The scanning endoscope system according to any one of claims 2 to 6, wherein a pulse width of the drive pulse is longer than a period of detection timing of the image signal.   The light source control means includes second input means for receiving an input from a user, and adjusts a pulse width of the drive pulse in accordance with a user input received by the second input means. The scanning endoscope system according to any one of claims 2 to 7.   The scanning according to any one of claims 1 to 8, wherein the optical fiber scanning unit moves an output end of the optical fiber so that a scanning speed of the illumination light is not constant. Type endoscope system.   The optical fiber scanning unit causes the emission end of the optical fiber to vibrate in two directions orthogonal to each other so that the illumination light performs Lissajous scanning in the scanning region at a constant period. The scanning endoscope system according to 9, wherein   The optical fiber scanning means rotates the emission end of the optical fiber in a spiral shape so that the illumination light rotates and scans in a spiral shape with a constant rotation period from the center to the periphery in the scanning region. The scanning endoscope system according to claim 9, wherein:   The scanning endoscope system according to claim 11, wherein the light source control unit generates the drive pulse when the illumination light scans a central portion in the scanning region.   The scanning endoscope system according to claim 12, wherein a diameter of a central portion in the scanning region is approximately 1/3 or less of a diameter of the scanning region. The optical fiber scanning means, after rotating the emission end of the optical fiber in a spiral shape, stops the rotation drive of the emission end of the optical fiber for a predetermined period,
The scanning endoscope system according to any one of claims 11 to 13, wherein the light source control unit stops emission of the illumination light for the predetermined period. A confocal pinhole arranged at a position conjugate with the condensing point of the illumination light,
The scanning endoscope system according to any one of claims 1 to 14, wherein the image signal detection unit receives the scattered light through the confocal pinhole.

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