JP5665552B2 - Calibration apparatus and calibration method - Google Patents

Description

  The present invention relates to a calibration device and a calibration method suitable for easily calculating a scanning error amount resulting from a product-specific characteristic of a scanning endoscope system.

  2. Description of the Related Art A scanning endoscope system that generates an image by optically scanning a subject by periodically moving an optical fiber is known. A specific configuration example of this type of scanning endoscope system is described in Patent Document 1.

  The scanning endoscope system described in Patent Document 1 includes an optical fiber that transmits and emits scanning light emitted from a light source. The optical fiber periodically scans the subject in a spiral manner in accordance with the frame rate by means of resonance motion and amplitude control by a piezoelectric biaxial actuator. The scanning endoscope system assigns pixel positions to detection signals in accordance with the detection timing of reflected light from a subject and performs a raster arrangement.

  Each detection signal arranged in a raster pattern represents a point image of a scanning position corresponding to the assigned pixel position. In order to generate a highly reproducible image without distortion, it is necessary to accurately arrange each point image according to the scanning position. Therefore, in this type of scanning endoscope system calibration, the operator relies on experience and feeling while viewing the generated image, the optical fiber resonance frequency, amplitude, inclination, applied voltage value to the biaxial actuator, An operation of grasping various characteristics such as a phase difference of applied voltages and storing a correction value of point image arrangement data in a memory is being performed.

US Pat. No. 6,294,775

  However, in the above method, an inexperienced worker cannot perform accurate calibration. In addition, there is a problem that variation is large among workers. In order to perform accurate calibration, it is necessary to determine a correction value after accurately measuring various characteristics with various measuring instruments such as an oscilloscope, a power meter, and a beam profiler. However, performing calibration using a plurality of types of measuring devices is a complicated operation. Such a complicated operation cannot be easily incorporated into the manufacturing process.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to easily calculate a scanning error amount caused by a product-specific characteristic of a scanning endoscope system. Providing a calibration apparatus and a calibration method.

  A calibration device according to an embodiment of the present invention that solves the above-described problem is a scanning device that periodically scans light emitted from a light source within a predetermined scanning range, and detects a scanning position and a light amount of the scanning light. Based on the comparison result, a light detection means, a histogram forming means for making a histogram of the light quantity distribution of the scanning light within the scanning range based on the detected scanning position and light quantity, a comparing means for comparing the histogram with a predetermined master histogram And a scanning error amount calculation means for calculating a scanning error amount due to the product-specific characteristics of the scanning device.

  According to the calibration device of the present invention, the histogram generated by using the light detection means capable of detecting the position in addition to the light amount is generated due to a complex characteristic unique to the product. The amount of scanning error to be calculated can be easily calculated.

  The histogram forming means divides and defines the effective light receiving area of the light detecting means into a plurality of predetermined areas, calculates the total light quantity for each area with reference to the scanning position and the light quantity detected by the light detecting means, A configuration may be adopted in which the irradiation density is calculated by dividing the total light amount of the region by the area of the region, and a histogram is created using the irradiation density of each region.

  The calibration apparatus according to the present invention may be configured to include a display unit that displays at least one of a histogram and a scanning error amount from the viewpoint of usability.

  The calibration device according to the present invention corrects the correction value of the remap data for assigning the pixel position to each detection signal according to the detection timing of the reflected light of the light that scanned the subject based on the scanning error amount. It is good also as a structure with a value preparation means. In this case, the scanning endoscope system can perform remapping using the remapping data corrected by the correction value, and can generate an image in which distortion due to the scanning error is reduced.

  The calibration device according to the present invention may include an adjustment unit that adjusts the relative position between the scanning device and the light detection unit, and a correction value correction unit that corrects a correction value according to an adjustment amount by the adjustment unit. Good.

  The calibration apparatus according to the present invention may be configured to be housed in a shielding housing that shields the light detection means from outside light in order to improve the SN ratio of the detection signal by the light detection means.

  The scanning error amount calculation means may be configured to calculate the positional deviation amount of the scanning start point of the scanning light with respect to a predetermined reference position based on the difference between the appearance positions of the peaks of the histogram and the master histogram. Or it is good also as a structure which calculates the distortion of the scanning locus | trajectory of scanning light based on the approximation degree of the distribution shape of a histogram and a master histogram.

  The calibration device according to the present invention may be configured such that, in the histogram, a scanning range corresponding to an area with a predetermined light amount or more is defined as within the angle of view, and a range corresponding to an area with less than the predetermined light amount is defined as outside the field angle. .

  A calibration method according to an aspect of the present invention that solves the above problem is a light that detects a scanning position and a light amount of scanning light by a scanning device that periodically scans light within a predetermined scanning range with a predetermined light receiving element. Based on the detection step, a histogram forming step that forms a histogram of the light amount distribution of the scanning light within the scanning range based on the detected scanning position and light amount, a comparison step that compares the histogram with a predetermined master histogram, and a comparison result And a scanning error amount calculating step for calculating a scanning error amount due to a product-specific characteristic of the scanning device.

  ADVANTAGE OF THE INVENTION According to this invention, the calibration apparatus and the calibration method which can calculate easily the scanning error amount which arises due to the product intrinsic | native characteristic of a scanning endoscope system are provided.

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 schematic diagram of the calibration jig | tool of embodiment of this invention. It is a figure which shows the spot formation position, histogram data, etc. at the time of using the ideal scanning confocal endoscope system which does not have a product specific characteristic. It is the flowchart figure which arranged each process performed during the calibration of the scanning confocal endoscope system of embodiment of this invention in time series. It is a figure which shows the example of histogram data in case a product specific characteristic is included. It is a figure which shows the example of histogram data in case a product specific characteristic is included. It is a figure which shows the example of histogram data extract | collected when an optical fiber is drawn out to Z direction. It is a schematic diagram of a calibration jig suitable for a scanning endoscope system compatible with color imaging. It is the flowchart figure which arranged each process performed during the calibration of the scanning confocal endoscope system of embodiment of this invention in time series. It is a figure which shows flat histogram data. It is a supplementary figure for demonstrating the flowchart of FIG. It is the flowchart figure which arranged each process performed during the calibration of the scanning confocal endoscope system of embodiment of this invention in time series.

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

  The scanning endoscope system of the present embodiment is a scanning confocal endoscope system designed by applying the principle of a confocal microscope, and is preferably configured to observe a subject with high magnification and high resolution. Has been. 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 probe 200, and a monitor 300. 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 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 video signal output. A circuit 120 is included. 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 that excites the drug 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 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 and is incident on the proximal end of the optical fiber 202, then transmitted through the optical fiber 202 and 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.

  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.

  The excitation light is pulsed light (or continuous light), and is emitted from the tip 202a of the optical fiber 202 during the period from the start of application of the alternating voltage to the biaxial actuator 204C to the stop of application. 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. 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 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 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 forming position in the observation region (scanning region) corresponding to the position and the return light from the spot forming position are detected. Thus, the signal acquisition timing for obtaining the digital detection signal is almost uniquely determined. The CPU memory 110 stores a remapping table that associates the determined signal acquisition timing with the pixel position (pixel address). Note that the timing for detecting the return light and the signal acquisition timing are substantially the same.

  By the way, the scanning confocal endoscope system 1 includes unique characteristics (hereinafter referred to as “product unique characteristics”) that depend on individual product differences. Such product-specific characteristics include, for example, the resonance frequency and amplitude of the optical fiber 202, the inclination with respect to the central axis AX, the applied voltage value to the biaxial actuator 204C, the phase difference of the applied voltage, and the like. The scanning trajectory deviates from the ideal trajectory because the spot formation position varies mainly due to the product-specific characteristics. With uniformly determined remapping data, pixel placement errors due to variations in spot formation positions remain, and the generated image is distorted depending on the product-specific characteristics. In the present embodiment, product-specific characteristics can be estimated based on histogram data (described later). In order to suppress the distortion of the generated image, the correction value of the remap data is calculated using the histogram data and stored in the CPU memory 110 or the sub memory 208.

  The video signal processing circuit 116 refers to the remap data corrected by the correction value, and assigns the point image represented by each digital detection signal to the pixel address according to the signal acquisition timing. 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 three-dimensional confocal image of a subject with high magnification and high resolution is displayed.

  FIG. 3 is a schematic diagram of a calibration jig 400 used during calibration according to the present embodiment. In calibration, a correction value for correcting uniformly determined remapping data is created (if there is no uniformly determined remapping data, the remapping data itself is created). .

  The calibration jig 400 is configured independently of the system main body 100, but may be part of the configuration incorporated in the system main body 100. As shown in FIG. 3, the calibration jig 400 has a case 402. The case 402 accommodates a PSD (Position Sensitive Detector) 404, a power adjustment lens unit 406, and a support plate 410. The PSD 404 is arranged such that the light receiving surface is positioned on the XY plane (in other words, orthogonal to the Z direction). The power adjustment lens unit 406 is disposed so that the optical axis is in the Z direction. The position of the power adjustment lens unit 406 can be finely adjusted in the X direction or the Y direction by operating an XY adjustment tool 408 (for example, a general XY stage). An insertion port 412 is formed at the center of one end surface of the case 402.

  In performing the calibration, the confocal optical unit 204 is inserted into the insertion port 412. The confocal optical unit 204 is supported by the support plate 410 and the direction of the central axis AX is determined in the Z direction. The central axis AX, the optical axis of the power adjusting lens unit 406, and the center of the effective light receiving area of the PSD 404 are arranged substantially coaxially. The case 402 is in a light-shielded state with no external light entering. Therefore, the PSD 404 detects the spot light from the confocal optical unit 204 with a high S / N ratio. The output of the PSD 404 is input to the calibration circuit 414.

  The size of the spot light formed by the confocal optical unit 204 is extremely small. For this reason, accurate detection may not be possible with the resolution of the PSD 404. The power adjustment lens unit 406 expands the spot light so that spot detection by the PSD 404 is accurately performed.

  FIG. 4A illustrates the relationship between the effective light receiving area of the PSD 404, the spot formation position and the pixel position when the ideal scanning confocal endoscope system 1 having no product-specific characteristics is used. FIG. In FIG. 4A, for the sake of convenience of explanation, the effective light receiving area of the PSD 404 is divided into a lattice shape corresponding to the pixel arrangement. Further, the central portion of the effective light receiving region is defined as a region A, and the regions toward the peripheral portion on the right side of the region A are defined as regions B, C, D, E,. Each region toward the peripheral portion on the left side is defined as regions B ′, C ′, D ′, E ′,. The region may be divided in units of one pixel or may be divided in units of a plurality of pixels.

  The calibration circuit 414 calculates the total amount of spot light for each of the areas A to E, B ′ to E ′,... Using each spot formation position and each spot light quantity in the effective light receiving area detected by the PSD 404. calculate. When the excitation light is pulsed light, the total light amount in each region is obtained by [number of times of irradiation to the region × light amount of spot light]. When the excitation light is continuous light, it is obtained by [irradiation time to the area × spot light quantity per unit time]. The calibration circuit 414 calculates the irradiation density (irradiation energy per unit area) for each region by dividing the total light amount of each region by the region area. FIG. 4B shows a histogram in which the irradiation density (in other words, the light amount distribution per unit area of each region) of each region A to E..., B ′ to E ′. It is data.

  In the spiral scan method, a certain number of pulsed light beams are irradiated during each spiral (one rotation scan). The irradiation interval of the pulsed light is constant during the entire scanning period. Since the optical fiber 202 has a resonance motion, the period of each spiral is the same, but one spiral length is shorter as the scanning center (in other words, the pixel closer to the center of the image). Therefore, the irradiation density is higher at the scanning center. Therefore, when the ideal scan shown in FIG. 4A is performed, the histogram has a peak in the region A defined as the central region of the scan and the region as shown in FIG. 4B. It has a left-right symmetry across A. The calibration circuit 414 stores the histogram data shown in FIG. 4B as a master histogram. In FIG. 4 and the subsequent histogram diagrams, a one-dot chain line O is drawn at a distribution point corresponding to the center of the effective light receiving area of the PSD 404.

  FIG. 5 is a flowchart in which the processes performed during calibration are arranged in time series. For convenience of explanation, the processing step is abbreviated as “S” in the description and drawings in this specification.

  The initial spot formation position (hereinafter referred to as “reference spot formation position”) when no voltage is applied to the biaxial actuator 204C is a deviation (position deviation or angle) of the central axis of the optical fiber 202 with respect to the central axis AX. Or the like) may be off the center of the effective light receiving area of the PSD 404. However, in order to make maximum use of the effective light receiving area of the PSD 404, it is desirable to position the reference spot formation position at the center of the effective light receiving area. Further, when the deviation of the reference spot forming position is large, there is a possibility that the calibration may be hindered. In this case, position correction is essential.

  Therefore, as shown in FIG. 5, calibration setup is performed in the process of S <b> 1. Specifically, the operator finely adjusts the XY position of the power adjustment lens unit 406 by operating the XY adjustment tool 408 in accordance with a GUI (Graphical User Interface) displayed on the display screen of the monitor 300. The fine adjustment is performed until the detection position of the spot light when no voltage is applied to the biaxial actuator 204C roughly matches the reference spot formation position. The calibration circuit 414 calculates a predetermined correction value from the adjustment amount of the power adjustment lens unit 406 and temporarily holds it.

  After the calibration is set up, the operator operates the scanning confocal endoscope system 1 to perform scanning on the PSD 404. In the process of S2, the detected spot light is output from the PSD 404 to the calibration circuit 414. In the process of S3, each spot formation position and each spot light amount in the effective light receiving area of the PSD 404 are calculated based on the output of the PSD 404. In the process of S4, the total amount of spot light for each of the areas A to E, B ′ to E ′,... Is calculated using each calculated spot formation position and each spot light quantity, and the total light quantity of each area is calculated. Is divided by the area of the area to obtain the irradiation density for each area. Next, histogram data in which the irradiation density of each region is histogrammed is created and displayed on the display screen of the monitor 300.

  In the process of S5, the histogram data created in the process of S4 is compared with the master histogram. In the process of S6, a histogram error amount E is calculated based on the comparison result. In the present embodiment, the histogram error amount E is defined from the reference spot forming position shift amount E1 and the roundness E2 of the scanning locus. The deviation amount E1 of the reference spot formation position is defined as the deviation amount of the reference spot formation position with respect to the center of the effective light receiving area of the PSD 404 as described above. The roundness E2 is defined as a value representing the correlation between the scanning locus and the ideal locus (see FIG. 4A) on the shape surface. That is, the roundness E2 is higher as the distribution shapes of the histogram data and the master histogram are approximated (or the scanning locus is closer to the ideal locus (round circle)). In another embodiment, the histogram error amount E may be defined by other elements.

  For example, as shown in FIG. 6A, consider a case where the reference spot formation position is off the center of the effective light receiving area of the PSD 404 and the scanning locus itself is not distorted (substantially a perfect circle). In this case, as shown in FIG. 6B, the histogram data has a distribution shifted from the master histogram by an amount corresponding to the shift amount of the reference spot formation position. That is, the shift amount has a certain relationship with the shift amount E1. The histogram error amount E is equivalent to the shift amount E1 because the scanning locus itself is not distorted.

  In the process of S7, a predetermined function is applied to the deviation amount E1, and the correction value of the remapping data is calculated. Next, the correction value is corrected using the correction value corresponding to the adjustment amount of the power adjustment lens unit 406. In the process of S8, the corrected correction value after correction is stored in the CPU memory 110 or the sub memory 208 in association with the identification information of the confocal probe 200. The histogram error amount E may be displayed on the display screen of the monitor 300 together with the histogram data from the viewpoint of usability.

  For example, as shown in FIG. 7A, consider a case where the reference spot formation position deviates from the center of the effective light receiving area of the PSD 404 and the scanning locus is distorted into an ellipse. In this case, as shown in FIG. 7B, the histogram data has a distribution shifted from the master histogram by an amount corresponding to the amount of deviation of the reference spot formation position. Further, the symmetry with respect to the peak is broken according to the distortion of the scanning locus. That is, the left-right symmetry of the histogram data has a certain relationship with the roundness E2. In the example of FIG. 7, the histogram error amount E is defined by the shift amount E1 and the roundness E2. In the process of S7, a predetermined function is applied to the deviation amount E1 and the roundness E2, and the correction value of the remap data is calculated and corrected. In the process of S8, the corrected correction value after correction is stored in the CPU memory 110 or the sub memory 208 in association with the identification information of the confocal probe 200.

  According to the present embodiment, complex product unique characteristics can be easily measured by using the calibration jig 400 alone using the histogram data, and the correction value of the remapping data can be easily obtained.

  Here, the scanning locus changes in accordance with the position of the optical fiber 202 in the Z direction. Such a change in the scanning trajectory also varies from product to product depending on the product-specific characteristics. For example, consider a case where a predetermined amount of the optical fiber 202 is extended in the Z direction with respect to the example of FIG. In this case, the spot formation positions are more concentrated at the center of the scanning region as shown in FIG. Therefore, as shown in FIG. 8B, the histogram data has a distribution that is higher at the center of the scanning region and lower at the periphery of the scanning region. Thus, using the calibration jig 400, it is possible to collect histogram data for each position in the Z direction. For example, a correction value of remapping data for each position in the Z direction is obtained using each collected histogram data. Since an appropriate correction value can be applied for each position in the Z direction, the remap data is corrected with high accuracy and the image quality is improved.

  Since the return light is weaker toward the periphery of the scanning region, it may not contribute to image formation. Therefore, FOV (Field of View) is calculated using the histogram data. Specifically, in the histogram data, a spot formation position corresponding to a distribution having a value equal to or greater than a predetermined threshold S (see FIG. 8B) is defined as within the angle of view. A spot formation position corresponding to a distribution less than the threshold value S is defined as out of the field angle because it does not contribute to image formation due to insufficient light quantity. As an example, the spot formation position corresponding to the distribution included in the half width of the histogram is defined as the angle of view. Thus, by using the histogram data, it is possible to easily calculate the angle of view that varies depending on the product-specific characteristics. Note that, from the viewpoint of usability, only the distribution having a predetermined threshold value S or higher in the histogram data may be displayed on the display screen of the monitor 300.

  As the output of the light source 102 is increased, a distribution greater than or equal to the threshold S spreads around the scanning region. By repeating the recalculation of the histogram data while increasing the output of the light source 102, the output of the light source 102 necessary for obtaining a desired angle of view can be easily obtained.

  By the way, in the spiral scan method, since the irradiation density is higher toward the center of the scanning region, the decomposition of the phosphor progresses more rapidly and fading occurs. 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. In order to suppress the fading of fluorescence, for example, measures such as reducing the intensity of excitation light can be considered. However, when the intensity of the excitation light is suppressed, noise is particularly noticeable due to a lack of detected light quantity particularly in the periphery of the observation region. For this reason, there is a possibility that it may hinder the discovery of a lesioned part by a doctor or accurate determination of the lesioned part. Therefore, in the present embodiment, light amount control data effective for suppressing fluorescence fading is also created using histogram data created for calibration. The light quantity control data can be created by calibration of the scanning trajectory and a series of operations.

  FIG. 10 is a flowchart in which the processes performed during calibration are arranged in time series. As shown in FIG. 10, first, the processes of S1 to S4 similar to those in the flowchart of FIG. 5 are performed. In the process of S4, for example, histogram data shown in FIG. 4B is created. In the process of S15, it is determined whether or not flat histogram data has been created in the process of S4. FIG. 11 shows flat histogram data. As shown in FIG. 11, flat histogram data refers to data with uniform irradiation density in each region.

  When the histogram data is not flat (S15: NO), since the irradiation density is high at a specific location, the fading of fluorescence tends to proceed. In the process of S16, the output of the light source 102 during the sampling period is adjusted in order to flatten the histogram data. The processes of S2 to S4, S15, and S16 are repeatedly performed until flat histogram data is obtained.

  Specifically, the calibration circuit 414 holds the correlation between the output of the light source 102 and the amount of spot light detected by the PSD 404 as a function. During the scanning period corresponding to the area with high irradiation density (in the example of FIG. 4B, the period near the center of the scanning area), the light source 102 is modulated so that the irradiation density decreases to a predetermined reference value ( Reduce the duty ratio). During the scanning period corresponding to the area where the irradiation density is low (in the example of FIG. 4B, the period near the periphery of the scanning area), the output of the light source 102 is modulated so that the irradiation density increases to a predetermined reference value. Yes (increase the duty ratio). In the example of FIG. 4B, when the excitation light is continuous light, the output of the light source 102 is controlled to increase linearly in proportion to the time immediately after the sampling period starts and ends. However, the output may be controlled to change nonlinearly according to the product-specific characteristics. The predetermined reference value is set to, for example, the half-value width of the peak value of the histogram data created first after starting calibration. Alternatively, it is set to a value sufficient to secure the amount of reflected light necessary for image formation while suppressing the fading of fluorescence.

  When the histogram data becomes flat (S15: YES), the control data of the light source 102 created through the process of S16 is stored in the CPU memory 110 or the sub memory 208 (S17). In practical use, the light source 102 is controlled using the control data. There are no places where the irradiation density is excessively high in the scanning region.

  According to this embodiment, the energy absorbed by the phosphor is reduced at the center of the scanning region. Since the progress of decomposition of the phosphor is delayed, the fading of fluorescence can be suppressed. Since weak return light increases in the periphery of the scanning region, the S / N ratio is improved.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the technical idea of the present invention. For example, various forms (area size, shape, etc.) are assumed for the areas defined in FIG. The accuracy of calibration improves as the area is defined more finely, for example.

  The scanning endoscope system according to the present invention can be applied not only to a scanning confocal endoscope system but also to a scanning endoscope system corresponding to color image shooting exemplified in Patent Document 1. . FIG. 9 is a diagram showing a schematic configuration of a calibration jig 400 used at the time of calibration of a scanning endoscope system compatible with color photographing. An example of the configuration of the calibration jig 400 is shown in FIGS. 9A and 9B one by one.

  In a scanning endoscope system that supports color imaging, the spot diameter is not as small as that of a scanning confocal endoscope system. Therefore, the power adjustment lens unit 406 is unnecessary. In the configuration example of FIG. 9A, the XY adjustment tool 408 is attached to the PSD 404 instead of the power adjustment lens unit 406. In the configuration example of FIG. 9B, the support plate 410 is attached. Calibration setup is performed by finely adjusting the XY position of the PSD 404 or the support plate 410.

  By the way, the scanning endoscope system has a wide angle of view. In a scanning endoscope system compatible with color imaging, it is difficult to secure a sufficient amount of light for image formation around the scanning region due to cosine fourth law, vignetting, or the like. In particular, vignetting due to the outer cylinder 204A may occur depending on the product-specific characteristics, and the light quantity loss due to vignetting tends to be dominant. Vignetting is likely to occur because the diameter of the outer cylinder 204A is designed to be thin while maintaining a wide angle of view in order to reduce the burden on the patient.

  FIG. 12A shows the movement of the tip 202a of the optical fiber 202. FIG. FIG. 12B is a diagram for explaining light amount loss due to vignetting. FIG. 12C is a diagram illustrating a voltage applied to the light source 102. FIG. 12D is a diagram illustrating the spot light amount per unit time detected by the PDS 404. The horizontal axes in FIGS. 12A to 12D are time axes. The vertical axis in FIG. 12A indicates the amount of displacement in the X (or Y) direction of the tip 202a with reference to the central axis AX. The vertical axes of FIGS. 12B and 12D indicate the spot light amount per unit time. The vertical axis in FIG. 12C indicates the voltage applied to the light source 102.

  FIG. 12B shows a spot light amount per unit time when the output of the light source 102 is constant. In the vicinity of the scanning region, vignetting is caused by the outer cylinder 204A, so that the light amount loss is large as shown in FIG. Therefore, the output control of the light source 102 is performed, and the light amount loss due to vignetting is compensated by the increase in the spot light amount.

  FIG. 13 is a flowchart in which the processes performed during calibration are arranged in time series. As shown in FIG. 13, first, the processes of S1 to S3 similar to the flowchart of FIG. 5 are performed. In the process of S24, the light quantity for each spiral is calculated using each spot formation position and each spot light quantity calculated in the process of S3. That is, in the process of S24, the total amount of spot light detected during each spiral period is monitored during the sampling period. In the processing of S25, it is determined whether or not there remains a spiral period in which the total light amount is less than a predetermined value.

  When the spiral period in which the total light amount is less than the predetermined value remains (S25: YES), the light amount necessary for image formation is insufficient in the corresponding scanning region. In the process of S26, the output of the light source 102 during the corresponding spiral period is increased. The processes of S2, S3, and S24 to S26 are repeatedly performed until the total light amount of all corresponding spiral periods reaches a predetermined value. For example, as shown in FIG. 12C, the output of the light source 102 during the spiral period in which vignetting has occurred is increased. Thereby, the light quantity loss due to vignetting is compensated by the increase of the spot light quantity as shown in FIG.

  When the total light amount reaches a predetermined value in all spiral periods in which the total light amount has been insufficient (S25: NO), the control data of the light source 102 created through the processing of S26 is stored in the CPU memory 110 or the sub memory 208. (S27). In practical use, the light source 102 is controlled using the control data. Therefore, a sufficient amount of light for image formation around the scanning region is secured.

  When it is desired to illuminate the subject uniformly, the processes of S2, S3, and S24 to S26 may be performed so that the total light amount during the entire spiral period is constant. In this case, the light source 102 is controlled so that the output decreases during a spiral period in which the total light amount exceeds a predetermined value. During a spiral period in which the total light amount is less than a predetermined value, the output is controlled to increase.

  The scanning method to which the present invention can be applied is not limited to the spiral scanning method described in this embodiment. 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.

  The position detection element mounted on the calibration jig 400 is not limited to PSD. The PSD 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 Jig 402 Case 404 PSD
406 Power adjustment lens unit 408 XY adjustment tool 410 Support plate 412 Insertion port 414 Calibration circuit

Claims (18)

A scanning device that periodically scans the light emitted from the light source within a predetermined scanning range;
A light detecting means for detecting a scanning position and a light amount of the scanning light;
Histogram generating means for generating a histogram of the light quantity distribution of the scanning light within the scanning range based on the detected scanning position and the light quantity;
Comparing means for comparing the histogram with a predetermined master histogram;
A scanning error amount calculating means for calculating a scanning error amount caused by a product-specific characteristic of the scanning device based on the comparison result;
A calibration apparatus comprising: The histogram forming means includes:
The effective light receiving area of the light detection means is defined by dividing into a plurality of predetermined areas,
Calculate the total light amount for each region with reference to the scanning position and the light amount detected by the light detection means,
Calculate the irradiation density by dividing the total amount of light in each region by the area of the region,
The calibration apparatus according to claim 1, wherein a histogram is created using an irradiation density of each of the regions.   The calibration apparatus according to claim 1, further comprising display means for displaying at least one of the histogram or the scanning error amount.   Correction value generating means for generating a correction value of remapping data for assigning a pixel position to each detection signal according to the detection timing of the reflected light of the light scanned by the subject based on the scanning error amount The calibration device according to any one of claims 1 to 3. Adjusting means for adjusting the relative position between the scanning device and the light detecting means;
Correction value correcting means for correcting the correction value according to the adjustment amount by the adjusting means;
The calibration apparatus according to claim 4 , further comprising:   The calibration device according to claim 1, wherein the light detection unit is housed in a shielding housing that shields from external light.   The scanning error amount calculating means calculates a positional deviation amount of a scanning start point of the scanning light with respect to a predetermined reference position based on a difference between appearance positions of peaks of the histogram and the master histogram. The calibration device according to any one of claims 1 to 6.   The scanning error amount calculation means calculates distortion of the scanning trajectory of the scanning light based on the degree of approximation of the distribution shape of the histogram and the master histogram. The calibration device according to one item.   The scanning range corresponding to an area with a predetermined light amount or more in the histogram is defined as within the angle of view, and the range corresponding to an area with less than the predetermined light amount is defined as outside the angle of view. 9. The calibration apparatus according to any one of items 8. A light detecting step of detecting a scanning position and a light amount of scanning light by a scanning device that periodically scans light within a predetermined scanning range with a predetermined light receiving element;
A histogram forming step for histogramizing the light amount distribution of the scanning light within the scanning range based on the detected scanning position and the light amount;
A comparison step of comparing the histogram with a predetermined master histogram;
A scanning error amount calculating step for calculating a scanning error amount caused by a product-specific characteristic of the scanning device based on the comparison result;
A calibration method characterized by comprising: In the histogram step,
The effective light receiving area of the light receiving element is defined by being divided into a plurality of predetermined areas,
Calculate the total light amount for each region with reference to the scanning position and light amount detected in the light detection step,
Calculate the irradiation density by dividing the total amount of light in each region by the area of the region,
The calibration method according to claim 10, wherein a histogram is created using an irradiation density of each of the regions.   The calibration method according to claim 10, further comprising a display step of displaying at least one of the histogram or the scanning error amount.   And a correction value creating step of creating a correction value of remapping data for assigning a pixel position to each detection signal according to the detection timing of reflected light of the light scanned by the subject based on the scanning error amount. The calibration method according to any one of claims 10 to 12. An adjusting step for adjusting a relative position between the scanning device and the light receiving element;
A correction value correction step of correcting the correction value according to the adjusted amount of adjustment;
The calibration method according to claim 13 , further comprising:   The calibration method according to any one of claims 10 to 14, wherein the light receiving element is housed in a shielding housing shielded from external light.   The scanning error amount calculating step calculates a positional deviation amount of the scanning start point of the scanning light with respect to a predetermined reference position based on a difference between appearance positions of peaks of the histogram and the master histogram. The calibration method according to any one of claims 10 to 15.   17. The distortion of the scanning trajectory of the scanning light is calculated in the scanning error amount calculating step based on the degree of approximation between the distribution shapes of the histogram and the master histogram. The calibration method according to one item.   The scanning range corresponding to an area with a predetermined light amount or more in the histogram is defined as within the angle of view, and the range corresponding to an area with less than the predetermined light amount is defined as outside the angle of view. The calibration method according to any one of 17.

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